WorldWideScience

Sample records for modelling planetary albedo

  1. Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

    Science.gov (United States)

    Haines, E. L.; Metzger, A. E.

    1984-01-01

    In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

  2. Modeling Earth Albedo for Satellites in Earth Orbit

    DEFF Research Database (Denmark)

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate...... with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We present a modeling scheme base4d on Eartht reflectance, measured by NASA's Total Ozone Mapping Spectrometer......, in which the Earth Probe Satellite has recorded reflectivity data daily since mid 1996. The mean of these data can be used to calculate the Earth albedo given the positions of the satellite and the Sun. Our results show that the albedo varies highly with the solar angle to the satellite's field of view...

  3. Energy-balance climate models: stability experiments with a refined albedo and updated coefficients for infrared emission

    NARCIS (Netherlands)

    Oerlemans, J.

    1978-01-01

    A zonally averaged' climate model of the energy-balance type is examined. Recently published satellite measurements were used to improve existing parameterizations of planetary albedo and outgoing radiation in terms of surface and sea level temperature. A realistic constant for the diffusion of

  4. Effective single scattering albedo estimation using regional climate model

    CSIR Research Space (South Africa)

    Tesfaye, M

    2011-09-01

    Full Text Available In this study, by modifying the optical parameterization of Regional Climate model (RegCM), the authors have computed and compared the Effective Single-Scattering Albedo (ESSA) which is a representative of VIS spectral region. The arid, semi...

  5. Numerical models of planetary dynamos

    International Nuclear Information System (INIS)

    Glatzmaier, G.A.; Roberts, P.H.

    1992-01-01

    We describe a nonlinear, axisymmetric, spherical-shell model of planetary dynamos. This intermediate-type dynamo model requires a prescribed helicity field (the alpha effect) and a prescribed buoyancy force or thermal wind (the omega effect) and solves for the axisymmetric time-dependent magnetic and velocity fields. Three very different time dependent solutions are obtained from different prescribed sets of alpha and omega fields

  6. Land surface albedo bias in climate models and its association with tropical rainfall

    Science.gov (United States)

    Levine, Xavier J.; Boos, William R.

    2017-06-01

    The influence of surface albedo on tropical precipitation is widely appreciated, but albedo bias over snow-free areas in climate models has been studied little. Here historical Coupled Model Intercomparison Project Phase 5 simulations are shown to exhibit large multimodel mean bias and intermodel variability in boreal summer mean surface broadband shortwave albedo. Intermodel variability in this albedo is globally coherent over vegetated regions and correlates with intermodel tropical precipitation variability. Evidence supports the hypothesis that these spatially coherent albedo variations cause precipitation variations. Specifically, spatial structures of albedo and precipitation variations are distinct, suggesting the latter do not cause the former by darkening soil. Furthermore, simulated interannual albedo variance is small compared to intermodel albedo variance, while the ratio of interannual to intermodel precipitation variance is much larger. Finally, imposing the dominant pattern of intermodel albedo variability in one climate model causes a precipitation change with structure similar to that of the intermodel variability.

  7. Model test of CCN-cloud albedo climate forcing

    Science.gov (United States)

    Ghan, S. J.; Taylor, K. E.; Penner, J. E.; Erickson, D. J., III

    1990-01-01

    Cloud condensation nuclei (CCN) influence cloud albedo through their effect on the cloud droplet size distribution. A number of studies have evaluated the climatic impact of the CCN-cloud albedo feedback, but all have assumed that cloud distributions, cloud thicknesses, and cloud liquid water contents would remain constant as the climate adjusted. This assumption has been tested using the Livermore version of the National Center for Atmospheric Research Community Climate Model. The results indicate that there are no significant compensating changes in cloud properties that would counteract the 1.7 percent global albedo increase resulting from a fourfold increase in marine CCN concentration. Furthermore, when ocean surface temperatures are decreased 4 C in a manner broadly consistent with the enhanced cloud albedos, an increase in cloud fraction of 3.5 percent and a reduction in cloud altitude are predicted, leading to a positive feedback from clouds that would imply a climate impact roughly double that calculated from cloud droplet size distribution change alone.

  8. Validation of snow characteristics and snow albedo feedback in the Canadian Regional Climate Model simulations over North America

    Science.gov (United States)

    Fang, B.; Sushama, L.; Diro, G. T.

    2015-12-01

    Snow characteristics and snow albedo feedback (SAF) over North America, as simulated by the fifth-generation Canadian Regional Climate Model (CRCM5), when driven by ERA-40/ERA-Interim, CanESM2 and MPI-ESM-LR at the lateral boundaries, are analyzed in this study. Validation of snow characteristics is performed by comparing simulations against available observations from MODIS, ISCCP and CMC. Results show that the model is able to represent the main spatial distribution of snow characteristics with some overestimation in snow mass and snow depth over the Canadian high Arctic. Some overestimation in surface albedo is also noted for the boreal region which is believed to be related to the snow unloading parameterization, as well as the overestimation of snow albedo. SAF is assessed both in seasonal and climate change contexts when possible. The strength of SAF is quantified as the amount of additional net shortwave radiation at the top of the atmosphere as surface albedo decreases in association with a 1°C increase in surface temperature. Following Qu and Hall (2007), this is expressed as the product of the variation in planetary albedo with surface albedo and the change in surface albedo for 1°C change in surface air temperature during the season, which in turn is determined by the strength of the snow cover and snowpack metamorphosis feedback loops. Analysis of the latter term in the seasonal cycle suggests that for CRCM5 simulations, the snow cover feedback loop is more dominant compared to the snowpack metamorphosis feedback loop, whereas for MODIS, the two feedback loops have more or less similar strength. Moreover, the SAF strength in the climate change context appears to be weaker than in the seasonal cycle and is sensitive to the driving GCM and the RCP scenario.

  9. Using albedo to reform wind erosion modelling, mapping and monitoring

    Science.gov (United States)

    Chappell, Adrian; Webb, Nicholas P.

    2016-12-01

    Wind erosion and dust emission models are used to assess the impacts of dust on radiative forcing in the atmosphere, cloud formation, nutrient fertilisation and human health. The models are underpinned by a two-dimensional geometric property (lateral cover; L) used to characterise the three-dimensional aerodynamic roughness (sheltered area or wakes) of the Earth's surface and calibrate the momentum it extracts from the wind. We reveal a fundamental weakness in L and demonstrate that values are an order of magnitude too small and significant aerodynamic interactions between roughness elements and their sheltered areas have been omitted, particularly under sparse surface roughness. We describe a solution which develops published work to establish a relation between sheltered area and the proportion of shadow over a given area; the inverse of direct beam directional hemispherical reflectance (black sky albedo; BSA). We show direct relations between shadow and wind tunnel measurements and thereby provide direct calibrations of key aerodynamic properties. Estimation of the aerodynamic parameters from albedo enables wind erosion assessments over areas, across platforms from the field to airborne and readily available satellite data. Our new approach demonstrated redundancy in existing wind erosion models and thereby reduced model complexity and improved fidelity. We found that the use of albedo enabled an adequate description of aerodynamic sheltering to characterise fluid dynamics and predict sediment transport without the use of a drag partition scheme (Rt) or threshold friction velocity (u∗t). We applied the calibrations to produce global maps of aerodynamic properties which showed very similar spatial patterns to each other and confirmed the redundancy in the traditional parameters of wind erosion modelling. We evaluated temporal patterns of predicted horizontal mass flux at locations across Australia which revealed variation between land cover types that would not

  10. Vegetation controls on northern high latitude snow-albedo feedback: observations and CMIP5 model simulations.

    Science.gov (United States)

    Loranty, Michael M; Berner, Logan T; Goetz, Scott J; Jin, Yufang; Randerson, James T

    2014-02-01

    The snow-masking effect of vegetation exerts strong control on albedo in northern high latitude ecosystems. Large-scale changes in the distribution and stature of vegetation in this region will thus have important feedbacks to climate. The snow-albedo feedback is controlled largely by the contrast between snow-covered and snow-free albedo (Δα), which influences predictions of future warming in coupled climate models, despite being poorly constrained at seasonal and century time scales. Here, we compare satellite observations and coupled climate model representations of albedo and tree cover for the boreal and Arctic region. Our analyses reveal consistent declines in albedo with increasing tree cover, occurring south of latitudinal tree line, that are poorly represented in coupled climate models. Observed relationships between albedo and tree cover differ substantially between snow-covered and snow-free periods, and among plant functional type. Tree cover in models varies widely but surprisingly does not correlate well with model albedo. Furthermore, our results demonstrate a relationship between tree cover and snow-albedo feedback that may be used to accurately constrain high latitude albedo feedbacks in coupled climate models under current and future vegetation distributions. © 2013 John Wiley & Sons Ltd.

  11. Vegetation controls on northern high latitude snow-albedo feedback: Observations and CMIP5 model simulations

    OpenAIRE

    Loranty, MM; Berner, LT; Goetz, SJ; Jin, Y; Randerson, JT

    2014-01-01

    The snow-masking effect of vegetation exerts strong control on albedo in northern high latitude ecosystems. Large-scale changes in the distribution and stature of vegetation in this region will thus have important feedbacks to climate. The snow-albedo feedback is controlled largely by the contrast between snow-covered and snow-free albedo (Δα), which influences predictions of future warming in coupled climate models, despite being poorly constrained at seasonal and century time scales. Here, ...

  12. International Planetary Data Alliance (IPDA) Information Model

    Science.gov (United States)

    Hughes, John Steven; Beebe, R.; Guinness, E.; Heather, D.; Huang, M.; Kasaba, Y.; Osuna, P.; Rye, E.; Savorskiy, V.

    2007-01-01

    This document is the third deliverable of the International Planetary Data Alliance (IPDA) Archive Data Standards Requirements Identification project. The goal of the project is to identify a subset of the standards currently in use by NASAs Planetary Data System (PDS) that are appropriate for internationalization. As shown in the highlighted sections of Figure 1, the focus of this project is the Information Model component of the Data Architecture Standards, namely the object models, a data dictionary, and a set of data formats.

  13. Spatio-temporal Variability of Albedo and its Impact on Glacier Melt Modelling

    Science.gov (United States)

    Kinnard, C.; Mendoza, C.; Abermann, J.; Petlicki, M.; MacDonell, S.; Urrutia, R.

    2017-12-01

    Albedo is an important variable for the surface energy balance of glaciers, yet its representation within distributed glacier mass-balance models is often greatly simplified. Here we study the spatio-temporal evolution of albedo on Glacier Universidad, central Chile (34°S, 70°W), using time-lapse terrestrial photography, and investigate its effect on the shortwave radiation balance and modelled melt rates. A 12 megapixel digital single-lens reflex camera was setup overlooking the glacier and programmed to take three daily images of the glacier during a two-year period (2012-2014). One image was chosen for each day with no cloud shading on the glacier. The RAW images were projected onto a 10m resolution digital elevation model (DEM), using the IMGRAFT software (Messerli and Grinsted, 2015). A six-parameter camera model was calibrated using a single image and a set of 17 ground control points (GCPs), yielding a georeferencing accuracy of accounting for possible camera movement over time. The reflectance values from the projected image were corrected for topographic and atmospheric influences using a parametric solar irradiation model, following a modified algorithm based on Corripio (2004), and then converted to albedo using reference albedo measurements from an on-glacier automatic weather station (AWS). The image-based albedo was found to compare well with independent albedo observations from a second AWS in the glacier accumulation area. Analysis of the albedo maps showed that the albedo is more spatially-variable than the incoming solar radiation, making albedo a more important factor of energy balance spatial variability. The incorporation of albedo maps within an enhanced temperature index melt model revealed that the spatio-temporal variability of albedo is an important factor for the calculation of glacier-wide meltwater fluxes.

  14. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Science.gov (United States)

    Wang, Tao; Peng, Shushi; Krinner, Gerhard; Ryder, James; Li, Yue; Dantec-Nédélec, Sarah; Ottlé, Catherine

    2015-01-01

    Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation) into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms) and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique) improve the simulation accuracy of mean seasonal (October throughout May) snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the magnitude of

  15. Impacts of Satellite-Based Snow Albedo Assimilation on Offline and Coupled Land Surface Model Simulations.

    Directory of Open Access Journals (Sweden)

    Tao Wang

    Full Text Available Seasonal snow cover in the Northern Hemisphere is the largest component of the terrestrial cryosphere and plays a major role in the climate system through strong positive feedbacks related to albedo. The snow-albedo feedback is invoked as an important cause for the polar amplification of ongoing and projected climate change, and its parameterization across models is an important source of uncertainty in climate simulations. Here, instead of developing a physical snow albedo scheme, we use a direct insertion approach to assimilate satellite-based surface albedo during the snow season (hereafter as snow albedo assimilation into the land surface model ORCHIDEE (ORganizing Carbon and Hydrology In Dynamic EcosystEms and assess the influences of such assimilation on offline and coupled simulations. Our results have shown that snow albedo assimilation in both ORCHIDEE and ORCHIDEE-LMDZ (a general circulation model of Laboratoire de Météorologie Dynamique improve the simulation accuracy of mean seasonal (October throughout May snow water equivalent over the region north of 40 degrees. The sensitivity of snow water equivalent to snow albedo assimilation is more pronounced in the coupled simulation than the offline simulation since the feedback of albedo on air temperature is allowed in ORCHIDEE-LMDZ. We have also shown that simulations of air temperature at 2 meters in ORCHIDEE-LMDZ due to snow albedo assimilation are significantly improved during the spring in particular over the eastern Siberia region. This is a result of the fact that high amounts of shortwave radiation during the spring can maximize its snow albedo feedback, which is also supported by the finding that the spatial sensitivity of temperature change to albedo change is much larger during the spring than during the autumn and winter. In addition, the radiative forcing at the top of the atmosphere induced by snow albedo assimilation during the spring is estimated to be -2.50 W m-2, the

  16. High-resolution mapping and modelling of surface albedo in Norwegian boreal forests: from remotely sensed data to predictions

    Science.gov (United States)

    Cherubini, Francesco; Hu, Xiangping; Vezhapparambu, Sajith; Stromman, Anders

    2017-04-01

    Surface albedo, a key parameter of the Earth's climate system, has high variability in space, time, and land cover and its parameterization is among the most important variables in climate models. The lack of extensive estimates for model improvement is one of the main limitations for accurately quantifying the influence of surface albedo changes on the planetary radiation balance. We use multi-year satellite retrievals of MODIS surface albedo (MCD43A3), high resolution land cover maps, and meteorological records to characterize albedo variations in Norway across latitude, seasons, land cover type, and topography. We then use this dataset to elaborate semi-empirical models to predict albedo values as a function of tree species, age, volume and climate variables like temperature and snow water equivalents (SWE). Given the complexity of the dataset and model formulation, we apply an innovative non-linear programming approach simultaneously coupled with linear un-mixing. The MODIS albedo products are at a resolution of about 500 m and 8 days. The land cover maps provide vegetation structure information on relative abundance of tree species, age, and biomass volumes at 16 m resolution (for both deciduous and coniferous species). Daily observations of meteorological information on air temperature and SWE are produced at 1 km resolution from interpolation of meteorological weather stations in Norway. These datasets have different resolution and projection, and are harmonized by identifying, for each MODIS pixel, the intersecting land cover polygons and the percentage area of the MODIS pixel represented by each land cover type. We then filter the subplots according to the following criteria: i) at least 96% of the total pixel area is covered by a single land cover class (either forest or cropland); ii) if forest area, at least 98% of the forest area is covered by spruce, deciduous or pine. Forested pixels are then categorized as spruce, deciduous, or pine dominant if the

  17. ALBEDO MODELS FOR SNOW AND ICE ON A FRESHWATER LAKE. (R824801)

    Science.gov (United States)

    AbstractSnow and ice albedo measurements were taken over a freshwater lake in Minnesota for three months during the winter of 1996¯1997 for use in a winter lake water quality model. The mean albedo of new snow was measured as 0.83±0.028, while the...

  18. Assimilation of satellite observed snow albedo in a land surface model

    NARCIS (Netherlands)

    Malik, M.J.; van der Velde, R.; Vekerdy, Z.; Su, Zhongbo

    2012-01-01

    This study assesses the impact of assimilating satellite-observed snow albedo on the Noah land surface model (LSM)-simulated fluxes and snow properties. A direct insertion technique is developed to assimilate snow albedo into Noah and is applied to three intensive study areas in North Park

  19. A new albedo parameterization for use in climate models over the Antarctic ice sheet

    NARCIS (Netherlands)

    Kuipers Munneke, P.|info:eu-repo/dai/nl/304831891; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Flanner, M.G.; Gardner, A.S.; van de Berg, W.J.|info:eu-repo/dai/nl/304831611

    2011-01-01

    A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995–2004. Over the Antarctic

  20. The Alpine snow-albedo feedback in regional climate models

    Science.gov (United States)

    Winter, Kevin J.-P. M.; Kotlarski, Sven; Scherrer, Simon C.; Schär, Christoph

    2017-02-01

    The effect of the snow-albedo feedback (SAF) on 2m temperatures and their future changes in the European Alps is investigated in the ENSEMBLES regional climate models (RCMs) with a focus on the spring season. A total of 14 re-analysis-driven RCM experiments covering the period 1961-2000 and 10 GCM-driven transient climate change projections for 1950-2099 are analysed. A positive springtime SAF is found in all RCMs, but the range of the diagnosed SAF is large. Results are compared against an observation-based SAF estimate. For some RCMs, values very close to this estimate are found; other models show a considerable overestimation of the SAF. Net shortwave radiation has the largest influence of all components of the energy balance on the diagnosed SAF and can partly explain its spatial variability. Model deficiencies in reproducing 2m temperatures above snow and ice and associated cold temperature biases at high elevations seem to contribute to a SAF overestimation in several RCMs. The diagnosed SAF in the observational period strongly influences the estimated SAF contribution to twenty first century temperature changes in the European Alps. This contribution is subject to a clear elevation dependency that is governed by the elevation-dependent change in the number of snow days. Elevations of maximum SAF contribution range from 1500 to 2000 m in spring and are found above 2000 m in summer. Here, a SAF contribution to the total simulated temperature change between 0 and 0.5 °C until 2099 (multi-model mean in spring: 0.26 °C) or 0 and 14 % (multi-model mean in spring: 8 %) is obtained for models showing a realistic SAF. These numbers represent a well-funded but only approximate estimate of the SAF contribution to future warming, and a remaining contribution of model-specific SAF misrepresentations cannot be ruled out.

  1. MODIS/Terra+Aqua BRDF/Albedo Model Parameters Daily L3 Global 0.05Deg CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS MCD43C1 Version 6 Bidirectional reflectance distribution function and Albedo (BRDF/Albedo) Model Parameters data set is a 5600 meter daily 16-day product....

  2. MODIS/Terra+Aqua BRDF/Albedo Model Parameters Daily L3 Global - 500m V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS MCD43A1 Version 6 Bidirectional reflectance distribution function and Albedo (BRDF/Albedo) Model Parameters data set is a 500 meter daily 16-day product....

  3. MODIS/Terra+Aqua BRDF/Albedo Model Parameters Daily L3 Global 500m SIN Grid

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS Near Real Time (NRT) MCD43A1N, MODIS Combined Aqua and Terra Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameters is a...

  4. MODIS/Terra+Aqua BRDF/Albedo Model Parameters Daily L3 Global 0.05Deg CMG

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS Near Real Time (NRT) MCD43C1N, MODIS Combined Aqua and Terra Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameters is a...

  5. Energy Balance Models and Planetary Dynamics

    Science.gov (United States)

    Domagal-Goldman, Shawn

    2012-01-01

    We know that planetary dynamics can have a significant affect on the climate of planets. Planetary dynamics dominate the glacial-interglacial periods on Earth, leaving a significant imprint on the geological record. They have also been demonstrated to have a driving influence on the climates of other planets in our solar system. We should therefore expect th.ere to be similar relationships on extrasolar planets. Here we describe a simple energy balance model that can predict the growth and thickness of glaciers, and their feedbacks on climate. We will also describe model changes that we have made to include planetary dynamics effects. This is the model we will use at the start of our collaboration to handle the influence of dynamics on climate.

  6. Analysis of earth albedo effect on sun sensor measurements based on theoretical model and mission experience

    Science.gov (United States)

    Brasoveanu, Dan; Sedlak, Joseph

    1998-01-01

    Analysis of flight data from previous missions indicates that anomalous Sun sensor readings could be caused by Earth albedo interference. A previous Sun sensor study presented a detailed mathematical model of this effect. The model can be used to study the effect of both diffusive and specular reflections and to improve Sun angle determination based on perturbed Sun sensor measurements, satellite position, and an approximate knowledge of attitude. The model predicts that diffuse reflected light can cause errors of up to 10 degrees in Coarse Sun Sensor (CSS) measurements and 5 to 10 arc sec in Fine Sun Sensor (FSS) measurements, depending on spacecraft orbit and attitude. The accuracy of these sensors is affected as long as part of the illuminated Earth surface is present in the sensor field of view. Digital Sun Sensors (DSS) respond in a different manner to the Earth albedo interference. Most of the time DSS measurements are not affected, but for brief periods of time the Earth albedo can cause errors which are a multiple of the sensor least significant bit and may exceed one degree. This paper compares model predictions with Tropical Rainfall Measuring Mission (TRMM) CSS measurements in order to validate and refine the model. Methods of reducing and mitigating the impact of Earth albedo are discussed. ne CSS sensor errors are roughly proportional to the Earth albedo coefficient. Photocells that are sensitive only to ultraviolet emissions would reduce the effective Earth albedo by up to a thousand times, virtually eliminating all errors caused by Earth albedo interference.

  7. Empirical models of monthly and annual surface albedo in managed boreal forests of Norway

    Science.gov (United States)

    Bright, Ryan M.; Astrup, Rasmus; Strømman, Anders H.

    2013-04-01

    As forest management activities play an increasingly important role in climate change mitigation strategies of Nordic regions such as Norway, Sweden, and Finland -- the need for a more comprehensive understanding of the types and magnitude of biogeophysical climate effects and their various tradeoffs with the global carbon cycle becomes essential to avoid implementation of sub-optimal policy. Forest harvest in these regions reduces the albedo "masking effect" and impacts Earth's radiation budget in opposing ways to that of concomitant carbon cycle perturbations; thus, policies based solely on biogeochemical considerations in these regions risk being counterproductive. There is therefore a need to better understand how human disturbances (i.e., forest management activities) affect important biophysical factors like surface albedo. An 11-year remotely sensed surface albedo dataset coupled with stand-level forest management data for a variety of stands in Norway's most productive logging region are used to develop regression models describing temporal changes in monthly and annual forest albedo following clear-cut harvest disturbance events. Datasets are grouped by dominant tree species and site indices (productivity), and two alternate multiple regression models are developed and tested following a potential plus modifier approach. This resulted in an annual albedo model with statistically significant parameters that explains a large proportion of the observed variation, requiring as few as two predictor variables: i) average stand age - a canopy modifier predictor of albedo, and ii) stand elevation - a local climate predictor of a forest's potential albedo. The same model structure is used to derive monthly albedo models, with models for winter months generally found superior to summer models, and conifer models generally outperforming deciduous. We demonstrate how these statistical models can be applied to routine forest inventory data to predict the albedo

  8. Computer Modeling of Planetary Surface Temperatures in Introductory Astronomy Courses

    Science.gov (United States)

    Barker, Timothy; Goodman, J.

    2013-01-01

    Barker, T., and Goodman, J. C., Wheaton College, Norton, MA Computer modeling is an essential part of astronomical research, and so it is important that students be exposed to its powers and limitations in the first (and, perhaps, only) astronomy course they take in college. Building on the ideas of Walter Robinson (“Modeling Dynamic Systems,” Springer, 2002) we have found that STELLA software (ISEE Systems) allows introductory astronomy students to do sophisticated modeling by the end of two classes of instruction, with no previous experience in computer programming or calculus. STELLA’s graphical interface allows students to visualize systems in terms of “flows” in and out of “stocks,” avoiding the need to invoke differential equations. Linking flows and stocks allows feedback systems to be constructed. Students begin by building an easily understood system: a leaky bucket. This is a simple negative feedback system in which the volume in the bucket (a “stock”) depends on a fixed inflow rate and an outflow that increases in proportion to the volume in the bucket. Students explore how changing inflow rate and feedback parameters affect the steady-state volume and equilibration time of the system. This model is completed within a 50-minute class meeting. In the next class, students are given an analogous but more sophisticated problem: modeling a planetary surface temperature (“stock”) that depends on the “flow” of energy from the Sun, the planetary albedo, the outgoing flow of infrared radiation from the planet’s surface, and the infrared return from the atmosphere. Students then compare their STELLA model equilibrium temperatures to observed planetary temperatures, which agree with model ones for worlds without atmospheres, but give underestimates for planets with atmospheres, thus introducing students to the concept of greenhouse warming. We find that if we give the students part of this model at the start of a 50-minute class they are

  9. Improvement of Mars surface snow albedo modeling in LMD Mars GCM with SNICAR

    Science.gov (United States)

    Singh, D.; Flanner, M.; Millour, E.

    2017-12-01

    The current version of Laboratoire de Météorologie Dynamique (LMD) Mars GCM (original-MGCM) uses annually repeating (prescribed) albedo values from the Thermal Emission Spectrometer observations. We integrate the Snow, Ice, and Aerosol Radiation (SNICAR) model with MGCM (SNICAR-MGCM) to prognostically determine H2O and CO2 ice cap albedos interactively in the model. Over snow-covered regions mean SNICAR-MGCM albedo is higher by about 0.034 than original-MGCM. Changes in albedo and surface dust content also impact the shortwave energy flux at the surface. SNICAR-MGCM model simulates a change of -1.26 W/m2 shortwave flux on a global scale. Globally, net CO2 ice deposition increases by about 4% over one Martian annual cycle as compared to original-MGCM simulations. SNICAR integration reduces the net mean global surface temperature, and the global surface pressure of Mars by about 0.87% and 2.5% respectively. Changes in albedo also show a similar distribution as dust deposition over the globe. The SNICAR-MGCM model generates albedos with higher sensitivity to surface dust content as compared to original-MGCM. For snow-covered regions, we improve the correlation between albedo and optical depth of dust from -0.91 to -0.97 with SNICAR-MGCM as compared to original-MGCM. Using new diagnostic capabilities with this model, we find that cryospheric surfaces (with dust) increase the global surface albedo of Mars by 0.022. The cryospheric effect is severely muted by dust in snow, however, which acts to decrease the planet-mean surface albedo by 0.06.

  10. Deriving albedo maps for HAPEX-Sahel from ASAS data using kernel-driven BRDF models

    Directory of Open Access Journals (Sweden)

    P. Lewis

    1999-01-01

    Full Text Available This paper describes the application and testing of a method for deriving spatial estimates of albedo from multi-angle remote sensing data. Linear kernel-driven models of surface bi-directional reflectance have been inverted against high spatial resolution multi-angular, multi- spectral airborne data of the principal cover types within the HAPEX-Sahel study site in Niger, West Africa. The airborne data are obtained from the NASA Airborne Solid-state Imaging Spectrometer (ASAS instrument, flown in Niger in September and October 1992. The maps of model parameters produced are used to estimate integrated reflectance properties related to spectral albedo. Broadband albedo has been estimated from this by weighting the spectral albedo for each pixel within the map as a function of the appropriate spectral solar irradiance and proportion of direct and diffuse illumination. Partial validation of the results was performed by comparing ASAS reflectance and derived directional-hemispherical reflectance with simulations of a millet canopy made with a complex geometric canopy reflectance model, the Botanical Plant Modelling System (BPMS. Both were found to agree well in magnitude. Broadband albedo values derived from the ASAS data were compared with ground-based (point sample albedo measurements and found to agree extremely well. These results indicate that the linear kernel-driven modelling approach, which is to be used operationally to produce global 16 day, 1 km albedo maps from forthcoming NASA Earth Observing System spaceborne data, is both sound and practical for the estimation of angle-integrated spectral reflectance quantities related to albedo. Results for broadband albedo are dependent on spectral sampling and on obtaining the correct spectral weigthings.

  11. Method to determine snow albedo values in the ultraviolet for radiative transfer modeling.

    Science.gov (United States)

    Schwander, H; Mayer, B; Ruggaber, A; Albold, A; Seckmeyer, G; Koepke, P

    1999-06-20

    For many cases modeled and measured UV global irradiances agree to within +/-5% for cloudless conditions, provided that all relevant parameters for describing the atmosphere and the surface are well known. However, for conditions with snow-covered surfaces this agreement is usually not achievable, because on the one hand the regional albedo, which has to be used in a model, is only rarely available and on the other hand UV irradiance alters with different snow cover of the surface by as much as 50%. Therefore a method is given to determine the regional albedo values for conditions with snow cover by use of a parameterization on the basis of snow depth and snow age, routinely monitored by the weather services. An algorithm is evolved by multiple linear regression between the snow data and snow-albedo values in the UV, which are determined from a best fit of modeled and measured UV irradiances for an alpine site in Europe. The resulting regional albedo values in the case of snow are in the 0.18-0.5 range. Since the constants of the regression depend on the area conditions, they have to be adapted if the method is applied for other sites. Using the algorithm for actual cases with different snow conditions improves the accuracy of modeled UV irradiances considerably. Compared with the use of an average, constant snow albedo, the use of actual albedo values, provided by the algorithm, halves the average deviations between measured and modeled UV global irradiances.

  12. Quality assurance of in-situ measurements of land surface albedo: A model-based approach

    Science.gov (United States)

    Adams, Jennifer; Gobron, Nadine; Widlowski, Jean-Luc; Mio, Corrado

    2016-04-01

    This paper presents the development of a model-based framework for assessing the quality of in-situ measurements of albedo used to validate land surface albedo products. Using a 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model, a quality assurance framework is built based on simulated field measurements of albedo within complex 3D canopies and under various illumination scenarios. This method provides an unbiased approach in assessing the quality of field measurements, and is also able to trace the contributions of two main sources of uncertainty in field-measurements of albedo; those resulting from 1) the field measurement protocol, such as height or placement of field measurement within the canopy, and 2) intrinsic factors of the 3D canopy under specific illumination characteristics considered, such as the canopy structure and landscape heterogeneity, tree heights, ecosystem type and season.

  13. Comparative Climates of the Trappist-1 Planetary System: Results from a Simple Climate-vegetation Model

    Science.gov (United States)

    Alberti, Tommaso; Carbone, Vincenzo; Lepreti, Fabio; Vecchio, Antonio

    2017-07-01

    The recent discovery of the planetary system hosted by the ultracool dwarf star TRAPPIST-1 could open new paths for investigations of the planetary climates of Earth-sized exoplanets, their atmospheres, and their possible habitability. In this paper, we use a simple climate-vegetation energy-balance model to study the climate of the seven TRAPPIST-1 planets and the climate dependence on various factors: the global albedo, the fraction of vegetation that could cover their surfaces, and the different greenhouse conditions. The model allows us to investigate whether liquid water could be maintained on the planetary surfaces (I.e., by defining a “surface water zone (SWZ)”) in different planetary conditions, with or without the presence of a greenhouse effect. It is shown that planet TRAPPIST-1d seems to be the most stable from an Earth-like perspective, since it resides in the SWZ for a wide range of reasonable values of the model parameters. Moreover, according to the model, outer planets (f, g, and h) cannot host liquid water on their surfaces, even with Earth-like conditions, entering a snowball state. Although very simple, the model allows us to extract the main features of the TRAPPIST-1 planetary climates.

  14. Comparative Climates of the Trappist-1 Planetary System: Results from a Simple Climate-vegetation Model

    Energy Technology Data Exchange (ETDEWEB)

    Alberti, Tommaso; Carbone, Vincenzo; Lepreti, Fabio [Dipartimento di Fisica, Università della Calabria, Ponte P. Bucci, Cubo 31C, I-87036, Rende (CS) (Italy); Vecchio, Antonio, E-mail: tommaso.alberti@unical.it, E-mail: tommasoalberti89@gmail.com [LESIA—Observatoire de Paris, PSL Research University, 5 place Jules Janssen, F-92190, Meudon (France)

    2017-07-20

    The recent discovery of the planetary system hosted by the ultracool dwarf star TRAPPIST-1 could open new paths for investigations of the planetary climates of Earth-sized exoplanets, their atmospheres, and their possible habitability. In this paper, we use a simple climate-vegetation energy-balance model to study the climate of the seven TRAPPIST-1 planets and the climate dependence on various factors: the global albedo, the fraction of vegetation that could cover their surfaces, and the different greenhouse conditions. The model allows us to investigate whether liquid water could be maintained on the planetary surfaces (i.e., by defining a “surface water zone (SWZ)”) in different planetary conditions, with or without the presence of a greenhouse effect. It is shown that planet TRAPPIST-1d seems to be the most stable from an Earth-like perspective, since it resides in the SWZ for a wide range of reasonable values of the model parameters. Moreover, according to the model, outer planets (f, g, and h) cannot host liquid water on their surfaces, even with Earth-like conditions, entering a snowball state. Although very simple, the model allows us to extract the main features of the TRAPPIST-1 planetary climates.

  15. Modeling Approaches in Planetary Seismology

    Science.gov (United States)

    Weber, Renee; Knapmeyer, Martin; Panning, Mark; Schmerr, Nick

    2014-01-01

    Of the many geophysical means that can be used to probe a planet's interior, seismology remains the most direct. Given that the seismic data gathered on the Moon over 40 years ago revolutionized our understanding of the Moon and are still being used today to produce new insight into the state of the lunar interior, it is no wonder that many future missions, both real and conceptual, plan to take seismometers to other planets. To best facilitate the return of high-quality data from these instruments, as well as to further our understanding of the dynamic processes that modify a planet's interior, various modeling approaches are used to quantify parameters such as the amount and distribution of seismicity, tidal deformation, and seismic structure on and of the terrestrial planets. In addition, recent advances in wavefield modeling have permitted a renewed look at seismic energy transmission and the effects of attenuation and scattering, as well as the presence and effect of a core, on recorded seismograms. In this chapter, we will review these approaches.

  16. A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard

    Directory of Open Access Journals (Sweden)

    M. Möller

    2012-09-01

    Full Text Available The ice cap Vestfonna is located in northeastern Svalbard and forms one of the largest ice bodies of the Eurasian Arctic. Its surface albedo plays a key role in the understanding and modelling of its energy and mass balance. The principle governing factors for albedo evolution, i.e. precipitation and air temperature and therewith snow depth and melt duration, were found to vary almost exclusively with terrain elevation throughout the ice cap. Hence, surface albedo can be expected to develop a comparable pattern. A new statistical model is presented that estimates this mean altitudinal albedo profile of the ice cap on the basis of a minimal set of meteorological variables on a monthly resolution. Model calculations are based on a sigmoid function of the artificial quantity rain-snow ratio and a linear function of cumulative snowfall and cumulative positive degree days. Surface albedo fields of the MODIS snow product MOD10A1 from the period March to October in the years 2001–2008 serve as a basis for both calibration and cross-validation of the model. The meteorological model input covers the period September 2000 until October 2008 and is based on ERA-Interim data of a grid point located close to the ice cap. The albedo model shows a good performance. The root mean square error between observed and modelled albedo values along the altitudinal profile is 0.057±0.028 (mean ± one standard deviation. The area weighted mean even reduces to a value of 0.054. Distinctly higher deviations (0.07–0.09 are only present throughout the very lowest and uppermost parts of the ice cap that are either small in area or hardly affected by surface melt. Thus, the new, minimal, statistical albedo model presented in this study is found to reproduce the albedo evolution on Vestfonna ice cap on a high level of accuracy and is thus suggested to be fully suitable for further application in broader energy or mass-balance studies of the ice cap.

  17. Modeling Earth Albedo Currents on Sun Sensors for Improved Vector Observations

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    2006-01-01

    Earth albedo influences vector measurements of the solar line of sight vector, due to the induced current on in the photo voltaics of Sun sensors. Although advanced digital Sun sensors exist, these are typically expensive and may not be suited for satellites in the nano or pico-class. Previously...... for modeling Sun sensor output by incorporating the Earth albedo model is presented. This model utilizes the directional information of in the Earth albedo model, which is achieved by Earth surface partitioning. This allows accurate simulation of the Sun sensor output and the results are consistent with Ørsted...... and useful for space environment simulations, and may be utilized to improve attitude estimation algorithms applying Sun sensor vector observations....

  18. Chemical kinetics and modeling of planetary atmospheres

    Science.gov (United States)

    Yung, Yuk L.

    1990-01-01

    A unified overview is presented for chemical kinetics and chemical modeling in planetary atmospheres. The recent major advances in the understanding of the chemistry of the terrestrial atmosphere make the study of planets more interesting and relevant. A deeper understanding suggests that the important chemical cycles have a universal character that connects the different planets and ultimately link together the origin and evolution of the solar system. The completeness (or incompleteness) of the data base for chemical kinetics in planetary atmospheres will always be judged by comparison with that for the terrestrial atmosphere. In the latter case, the chemistry of H, O, N, and Cl species is well understood. S chemistry is poorly understood. In the atmospheres of Jovian planets and Titan, the C-H chemistry of simple species (containing 2 or less C atoms) is fairly well understood. The chemistry of higher hydrocarbons and the C-N, P-N chemistry is much less understood. In the atmosphere of Venus, the dominant chemistry is that of chlorine and sulfur, and very little is known about C1-S coupled chemistry. A new frontier for chemical kinetics both in the Earth and planetary atmospheres is the study of heterogeneous reactions. The formation of the ozone hole on Earth, the ubiquitous photochemical haze on Venus and in the Jovian planets and Titan all testify to the importance of heterogeneous reactions. It remains a challenge to connect the gas phase chemistry to the production of aerosols.

  19. Spatiokinematical models of five planetary nebulae

    International Nuclear Information System (INIS)

    Sabbadin, F.

    1984-01-01

    The [OOOI] and Hα expansion velocity fields in the planetary nebulae NGC6058 and 6804 and the [OIII], Hα and [NII] expansion velocity fields in NGC6309, 6751 and 6818, were obtained from high dispersion spectra. Spatiokinematical models of the nebulae were derived assuming an expansion velocity of the gas proportional to the distance from the central star and using the expansion velocity-radius correlation previously given. The observational parameters of the nebulae (radius, mass and expansion velocity) and of the exciting stars (temperature, radius and luminosity) closely fit the suggested evolutionary model for this class of objects. (author)

  20. A COMPARISON OF OBSERVATION WITH MODELING FOR ALBEDO AND TRANSMITTANCE OF SNOW

    OpenAIRE

    アオキ, テルオ; セコ, カツモト; アオキ, タダオ; フカボリ, マサシ; Teruo, AOKI; Katsumoto, SEKO; Tadao, AOKI; Masashi, FUKABORI

    1994-01-01

    Snow surface albedo and transmittance inside the snow have been investigated by observation and modeling. Observations were taken by a grating type spectrometer at Tokamachi in March 1993. The observed snow was old and very wet. Microscope photo-graphs of snow grains taken at this time indicate that snow grain is spherical particles with size of about 1.0μm. Surface albedo and transmittance of snow by a multiple scattering model for the atmosphere-snow system with pure snow grain size of 1.0μ...

  1. Modelled climate sensitivity of the mass balance of Morteratschgletscher and its dependence on albedo parameterization

    NARCIS (Netherlands)

    Klok, E.J.; Oerlemans, J.

    2004-01-01

    This paper presents a study of the climate sensitivity of the mass balance of Morteratschgletscher in Switzerland, estimated from a two-dimensional mass balance model. Since the albedo scheme chosen is often the largest error source in mass balance models, we investigated the impact of using

  2. Gaian bottlenecks and planetary habitability maintained by evolving model biospheres: The ExoGaia model

    Science.gov (United States)

    Nicholson, Arwen E.; Wilkinson, David M.; Williams, Hywel T. P.; Lenton, Timothy M.

    2018-03-01

    The search for habitable exoplanets inspires the question - how do habitable planets form? Planet habitability models traditionally focus on abiotic processes and neglect a biotic response to changing conditions on an inhabited planet. The Gaia hypothesis postulates that life influences the Earth's feedback mechanisms to form a self-regulating system, and hence that life can maintain habitable conditions on its host planet. If life has a strong influence, it will have a role in determining a planet's habitability over time. We present the ExoGaia model - a model of simple `planets' host to evolving microbial biospheres. Microbes interact with their host planet via consumption and excretion of atmospheric chemicals. Model planets orbit a `star' which provides incoming radiation, and atmospheric chemicals have either an albedo, or a heat-trapping property. Planetary temperatures can therefore be altered by microbes via their metabolisms. We seed multiple model planets with life while their atmospheres are still forming and find that the microbial biospheres are, under suitable conditions, generally able to prevent the host planets from reaching inhospitable temperatures, as would happen on a lifeless planet. We find that the underlying geochemistry plays a strong role in determining long-term habitability prospects of a planet. We find five distinct classes of model planets, including clear examples of `Gaian bottlenecks' - a phenomenon whereby life either rapidly goes extinct leaving an inhospitable planet, or survives indefinitely maintaining planetary habitability. These results suggest that life might play a crucial role in determining the long-term habitability of planets.

  3. NASA Lunar and Planetary Mapping and Modeling

    Science.gov (United States)

    Day, B. H.; Law, E.

    2016-12-01

    NASA's Lunar and Planetary Mapping and Modeling Portals provide web-based suites of interactive visualization and analysis tools to enable mission planners, planetary scientists, students, and the general public to access mapped lunar data products from past and current missions for the Moon, Mars, and Vesta. New portals for additional planetary bodies are being planned. This presentation will recap significant enhancements to these toolsets during the past year and look forward to the results of the exciting work currently being undertaken. Additional data products and tools continue to be added to the Lunar Mapping and Modeling Portal (LMMP). These include both generalized products as well as polar data products specifically targeting potential sites for the Resource Prospector mission. Current development work on LMMP also includes facilitating mission planning and data management for lunar CubeSat missions, and working with the NASA Astromaterials Acquisition and Curation Office's Lunar Apollo Sample database in order to help better visualize the geographic contexts from which samples were retrieved. A new user interface provides, among other improvements, significantly enhanced 3D visualizations and navigation. Mars Trek, the project's Mars portal, has now been assigned by NASA's Planetary Science Division to support site selection and analysis for the Mars 2020 Rover mission as well as for the Mars Human Landing Exploration Zone Sites. This effort is concentrating on enhancing Mars Trek with data products and analysis tools specifically requested by the proposing teams for the various sites. Also being given very high priority by NASA Headquarters is Mars Trek's use as a means to directly involve the public in these upcoming missions, letting them explore the areas the agency is focusing upon, understand what makes these sites so fascinating, follow the selection process, and get caught up in the excitement of exploring Mars. The portals also serve as

  4. Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

    NARCIS (Netherlands)

    van Angelen, J.H.|info:eu-repo/dai/nl/325922470; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Lhermitte, S.; Fettweis, X.; Kuipers Munneke, P.|info:eu-repo/dai/nl/304831891; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; van Meijgaard, E.; Smeets, C.J.P.P.|info:eu-repo/dai/nl/191522236

    2012-01-01

    We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover,

  5. Spatial distribution of mineral dust single scattering albedo based on DREAM model

    Science.gov (United States)

    Kuzmanoski, Maja; Ničković, Slobodan; Ilić, Luka

    2016-04-01

    Mineral dust comprises a significant part of global aerosol burden. There is a large uncertainty in estimating role of dust in Earth's climate system, partly due to poor characterization of its optical properties. Single scattering albedo is one of key optical properties determining radiative effects of dust particles. While it depends on dust particle sizes, it is also strongly influenced by dust mineral composition, particularly the content of light-absorbing iron oxides and the mixing state (external or internal). However, an assumption of uniform dust composition is typically used in models. To better represent single scattering albedo in dust atmospheric models, required to increase accuracy of dust radiative effect estimates, it is necessary to include information on particle mineral content. In this study, we present the spatial distribution of dust single scattering albedo based on the Dust Regional Atmospheric Model (DREAM) with incorporated particle mineral composition. The domain of the model covers Northern Africa, Middle East and the European continent, with horizontal resolution set to 1/5°. It uses eight particle size bins within the 0.1-10 μm radius range. Focusing on dust episode of June 2010, we analyze dust single scattering albedo spatial distribution over the model domain, based on particle sizes and mineral composition from model output; we discuss changes in this optical property after long-range transport. Furthermore, we examine how the AERONET-derived aerosol properties respond to dust mineralogy. Finally we use AERONET data to evaluate model-based single scattering albedo. Acknowledgement We would like to thank the AERONET network and the principal investigators, as well as their staff, for establishing and maintaining the AERONET sites used in this work.

  6. Urban Morphology Influence on Urban Albedo: A Revisit with the S olene Model

    Science.gov (United States)

    Groleau, Dominique; Mestayer, Patrice G.

    2013-05-01

    This heuristic study of the urban morphology influence on urban albedo is based on some 3,500 simulations with the S olene model. The studied configurations include square blocks in regular and staggered rows, rectangular blocks with different street widths, cross-shaped blocks, infinite street canyons and several actual districts in Marseilles, Toulouse and Nantes, France. The scanned variables are plan density, facade density, building height, layout orientation, latitude, date and time of the day. The sky-view factors of the ground and canopy surfaces are also considered. This study demonstrates the significance of the facade density, in addition to the built plan density, as the explanatory geometrical factor to characterize the urban morphology, rather than building height. On the basis of these albedo calculations the puzzling results of Kondo et al. (Boundary-Layer Meteorol 100:225-242, 2001) for the influence of building height are explained, and the plan density influence is quantitatively assessed. It is shown that the albedo relationship with plan and facade densities obtained with the regular square plot configuration may be considered as a reference for all other configurations, with the exception of the infinite street canyon that shows systematic differences for the lower plan densities. The curves representing this empirical relationship may be used as a sort of abacus for all other geometries while an approximate simple mathematical model is proposed, as well as relationships between the albedo and sky-view factors.

  7. Atmospheric statistical dynamic models. Climate experiments: albedo experiments with a zonal atmospheric model

    International Nuclear Information System (INIS)

    Potter, G.L.; Ellsaesser, H.W.; MacCracken, M.C.; Luther, F.M.

    1978-06-01

    The zonal model experiments with modified surface boundary conditions suggest an initial chain of feedback processes that is largest at the site of the perturbation: deforestation and/or desertification → increased surface albedo → reduced surface absorption of solar radiation → surface cooling and reduced evaporation → reduced convective activity → reduced precipitation and latent heat release → cooling of upper troposphere and increased tropospheric lapse rates → general global cooling and reduced precipitation. As indicated above, although the two experiments give similar overall global results, the location of the perturbation plays an important role in determining the response of the global circulation. These two-dimensional model results are also consistent with three-dimensional model experiments. These results have tempted us to consider the possibility that self-induced growth of the subtropical deserts could serve as a possible mechanism to cause the initial global cooling that then initiates a glacial advance thus activating the positive feedback loop involving ice-albedo feedback (also self-perpetuating). Reversal of the cycle sets in when the advancing ice cover forces the wave-cyclone tracks far enough equatorward to quench (revegetate) the subtropical deserts

  8. Finite Elements Contact Modelling of Planetary Gear Trains

    Science.gov (United States)

    Stoyanov, Svetlin; Dobrev, Vasko; Dobreva, Antoaneta

    2017-10-01

    The paper presents the application aspects of computer technologies concerning the process of creating theoretical contact models of planetary gear trains using Abaqus/Explicit. The necessary assumptions, constrains and specific features of these gear drives are discussed in details. The models created are appropriate and useful tools for computer simulation research of the dynamic behaviour of planetary gear trains.

  9. Morpho-kinematic modeling of planetary nebulae

    Science.gov (United States)

    Chan, Tsz-Pan (Henry)

    2009-11-01

    The Planetary Nebulae (PNe) are the transition phase between asymptotic giant branch (AGB) star and white dwarfs for stars with masses between 1 and 8 M⊙. They were originally thought to be well-studied and can be explained with simple models. With the advance of imaging technology especially on Space Telescope (HST), the shapes of PNe have been found to be much more complex than we assumed to be. We aimed to investigate on the basic but mysterious intrinsic three-dimensional structures using the newly developed modeling software. Astronomers usually use the morphological classification on group and classify different properties of PNe. Over the past century many attempts have been made for this classification to seek for explaining and understanding the threedimensional structure that is responsible for the observed images. There have been two beliefs in explaining the variety of shapes of PNe and among them the most amazing one is that the morphologies can be accounted by different orientations of a single structure (Khromov & Kohoutek, 1968). Motivated by the study of Ring Nebula on its intrinsic structure, we investigated the possibility that different types of morphology in PNe can be explained by a single model. We used the newly developed modeling code SHAPE (Steffen et al., 2006), which cooperates the use of spatial information as well as its kinematics, and aimed to quantitatively investigate the basic structure inside PNe. We investigated two classical nebulae: NGC 2346 and NGC 2440. We proposed a simple but adequate model for these nebulae. Stimulated optical images and the p-v arrays were derived by the modeling code SHAPE to make comparison with the observed data to seek for the correctness of the model. Hubble velocity field and inverse square law density distribution were assumed throughout the modeling process. This model provides insights in seeking further adequate intrinsic structure of PNe.

  10. MODIS/Terra+Aqua BRDF/Albedo Snow-free Model Parameters Daily L3 Global 0.05Deg CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — Version 6 Bidirectional reflectance distribution function and Albedo (BRDF/Albedo) Model Snow Free Quality Parameters data set is a 5600 meter daily 16-day product....

  11. Surface albedo in relation to disturbance and early stand dynamics in the boreal forest: Implications for climate models

    Science.gov (United States)

    Halim, M. A.; Thomas, S. C.

    2017-12-01

    Surface albedo is the most important biophysical radiative forcing in the boreal forest. General Circulation Model studies have suggested that harvesting of boreal forest has a net cooling effect, in contrast to other terrestrial biomes, by increasing surface albedo. However, albedo estimation in these models has been achieved by simplifying processes governing albedo at a coarse scale (both spatial and temporal). Biophysical processes that determine albedo likely operate on small spatial and temporal scales, requiring more direct estimates of effects of landcover change on net radiation. We established a chronosequence study in post-fire and post-clearcut sites (2013, 2006, 1998), logging data from July 2013 to July 2017 in boreal forest sites in northwestern Ontario, Canada. Each age-class X disturbance had 3 three replicates, matched to 18 permanent circular plots (10-m radius) each with an instrumented tower measuring surface albedo, air and soil temperature, and soil moisture. We also measured leaf area index, species composition and soil organic matter content at each site. BRDF-corrected surface albedo was calculated from daily 30m x 30m reflectance data fused from the MODIS MOD09GA product and Landsat 7 reflectance data. Calculated albedo was verified using ground-based measurements. Results show that fire sites generally had lower (15-25%) albedo than clearcut sites in all seasons. Because of rapid forest regrowth, large perturbations of clearcut harvests on forest albedo started to fade out within a year. Albedo differences between fire and clearcut sites also declined sharply with stand age. Younger stands generally had higher albedo than older stands mainly due to the presence of broadleaf species (for example, Populus tremuloides). In spring, snow melted 10-12 days earlier in recent (2013) clearcut sites compared to closed-canopy sites, causing a sharp reduction in surface albedo in comparison to old clearcut/fire sites (2006 and 1998). Snow melted

  12. Spring Snow-Albedo Feedback Analysis Over the Third Pole: Results From Satellite Observation and CMIP5 Model Simulations

    Science.gov (United States)

    Guo, Hui; Wang, Xiaoyi; Wang, Tao; Ma, Yaoming; Ryder, James; Zhang, Taotao; Liu, Dan; Ding, Jinzhi; Li, Yue; Piao, Shilong

    2018-01-01

    The snow-albedo feedback is a crucial component in high-altitude cryospheric change but is poorly quantified over the Third Pole, encompassing the Karakoram and Tibetan Plateau. Here we present an analysis of present-day and future spring snow-albedo feedback over the Third Pole, using a 28 year satellite-based albedo and the latest climate model simulations. We show that present-day spring snow-albedo feedback strength is primarily determined by the decrease in albedo due to snow metamorphosis, rather than that due to reduced snow cover in the Karakoram, but not found in Southeastern Tibet. We further demonstrate an emergent relationship between snow-albedo feedback from the seasonal cycle and that from climate change across models. Combined with contemporary satellite-based snow-albedo feedback from seasonal cycle, this relationship enables us to estimate that the feedback strength for the Karakoram with a relatively high glaciated area is -2.42 ± 0.48% K-1 under an unmitigated scenario, which is much stronger than that for Southeastern Tibet (-1.64 ± 0.48% K-1) and for the Third Pole (-0.89 ± 0.44% K-1), respectively. Moreover, it is noteworthy that the magnitude of the constrained strength is only half of the unconstrained model estimate for the Third Pole, suggesting that current climate models generally overestimate the feedback of spring snow change to temperature change based on the unmitigated scenario.

  13. Using albedo to reform wind erosion modelling, mapping and monitoring

    Science.gov (United States)

    Dust emission models are used to assess the impacts of dust on radiative forcing in the atmosphere, cloud formation, nutrient fertilisation and human health. We describe a need in aeolian research to adequately represent the spatial variability and particularly the area average of the key aerodynami...

  14. Factors affecting projected Arctic surface shortwave heating and albedo change in coupled climate models.

    Science.gov (United States)

    Holland, Marika M; Landrum, Laura

    2015-07-13

    We use a large ensemble of simulations from the Community Earth System Model to quantify simulated changes in the twentieth and twenty-first century Arctic surface shortwave heating associated with changing incoming solar radiation and changing ice conditions. For increases in shortwave absorption associated with albedo reductions, the relative influence of changing sea ice surface properties and changing sea ice areal coverage is assessed. Changes in the surface sea ice properties are associated with an earlier melt season onset, a longer snow-free season and enhanced surface ponding. Because many of these changes occur during peak solar insolation, they have a considerable influence on Arctic surface shortwave heating that is comparable to the influence of ice area loss in the early twenty-first century. As ice area loss continues through the twenty-first century, it overwhelms the influence of changes in the sea ice surface state, and is responsible for a majority of the net shortwave increases by the mid-twenty-first century. A comparison with the Arctic surface albedo and shortwave heating in CMIP5 models indicates a large spread in projected twenty-first century change. This is in part related to different ice loss rates among the models and different representations of the late twentieth century ice albedo and associated sea ice surface state. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  15. Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

    Directory of Open Access Journals (Sweden)

    J. H. van Angelen

    2012-10-01

    Full Text Available We present a sensitivity study of the surface mass balance (SMB of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6% at the K-transect (west Greenland for the period 2004–2009 is considerably reduced compared to the previous density-dependent albedo scheme (+22%. To simulate realistic snow albedo values, a small concentration of black carbon is needed, which has strongest impact on melt in the accumulation area. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced meltwater retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer that covers the Greenland Ice Sheet.

  16. Estimating Crop Albedo in the Application of a Physical Model Based on the Law of Energy Conservation and Spectral Invariants

    Directory of Open Access Journals (Sweden)

    Jingjing Peng

    2015-11-01

    Full Text Available Albedo characterizes the radiometric interface of land surfaces, especially vegetation, and the atmosphere. Albedo is a critical input to many models, such as crop growth models, hydrological models and climate models. For the extensive attention to crop monitoring, a physical albedo model for crops is developed based on the law of energy conservation and spectral invariants, which is derived from a prior forest albedo model. The model inputs have been efficiently and physically parameterized, including the dependency of albedo on the solar zenith/azimuth angle, the fraction of diffuse skylight in the incident radiance, the canopy structure, the leaf reflectance/transmittance and the soil reflectance characteristics. Both the anisotropy of soil reflectance and the clumping effect of crop leaves at the canopy scale are considered, which contribute to the improvement of the model accuracy. The comparison between the model results and Monte Carlo simulation results indicates that the canopy albedo has high accuracy with an RMSE < 0.005. The validation using ground measurements has also demonstrated the reliability of the model and that it can reflect the interaction mechanism between radiation and the canopy-soil system.

  17. A model-based framework for the quality assessment of surface albedo in situ measurement protocols

    Science.gov (United States)

    Adams, Jennifer; Gobron, Nadine; Widlowski, Jean-Luc; Mio, Corrado

    2016-09-01

    Satellite-based retrievals of land surface albedo are essential for climate and environmental modelling communities. To be of use, satellite-retrievals are required to comply to given accuracy requirements, mainly achieved through comparison with in situ measurements. Differences between in situ and satellite-based retrievals depend on their actual difference and their associated uncertainties. It is essential that these uncertainties can be computed to properly understand the differences between satellite-based and in situ measurements of albedo, however quantifying the individual contributions of uncertainty is difficult. This study introduces a model-based framework for assessing the quality of in situ albedo measurements. A 3D Monte Carlo Ray Tracing (MCRT) radiative transfer model is used to simulate field measurements of surface albedo, and is able to identify and quantify potential sources of error in the field measurement. Compliance with the World Meteorological Organisation (WMO) requirement for 3% accuracy is tested. 8 scenarios were investigated, covering a range of ecosystem types and canopy structures, seasons, illumination angles and tree heights. Results indicate that height of measurement above the canopy is the controlling factor in accuracy, with each canopy scenario reaching the WMO requirement at different heights. Increasing canopy heterogeneity and tree height noticeably reduces the accuracy, whereas changing seasonality from summer to winter in a deciduous forest increases accuracy. For canopies with a row structure, illumination angle can significantly impact accuracy as a result of shadowing effects. Tests were made on the potential use of multiple in situ measurements, indicating considerably increased accuracy if two or more in situ measurements can be made.

  18. Evolutionary sequence of models of planetary nebulae

    International Nuclear Information System (INIS)

    Vil'koviskij, Eh.Ya.; Kondrat'eva, L.N.; Tambovtseva, L.V.

    1983-01-01

    The evolutionary sequences of model planetary nebulae of different masses have been calculated. The computed emission line intensities are compared with the observed ones by means of the parameter ''reduced size of the nebula'', Rsub(n). It is shown that the evolution tracks of Schonberner for the central stars are consistent with the observed data. Part of ionized mass Mi in any nebulae does not not exceed 0.3 b and in the average Msu(i) 3 years at actual values of radius Rsub(i) <0.025 ps. Then the luminosity growth slows down to the maximum temperature which central star reaches and decreases with sharp decrease of the star luminosity. At that, the radius of ionized zone of greater mass nebulae can even decrease, inspite of the constant expansion of the nebula. As a result nebulae of great masses having undergone the evolution can be included in the number of observed compact objects (Rsub(n) < 0.1 ps)

  19. MODIS/Terra+Aqua BRDF/Albedo Model Parameters 16-Day L3 Global 1km SIN Grid V005

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43B1) contains three-dimensional (3D) data sets providing users...

  20. MODIS/Terra+Aqua BRDF/Albedo Model Parameters 16-Day L3 Global 500m SIN Grid V005

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43A1) contains three-dimensional (3D) data sets providing users...

  1. Process-model simulations of cloud albedo enhancement by aerosols in the Arctic

    Science.gov (United States)

    Kravitz, Ben; Wang, Hailong; Rasch, Philip J.; Morrison, Hugh; Solomon, Amy B.

    2014-01-01

    A cloud-resolving model is used to simulate the effectiveness of Arctic marine cloud brightening via injection of cloud condensation nuclei (CCN), either through geoengineering or other increased sources of Arctic aerosols. An updated cloud microphysical scheme is employed, with prognostic CCN and cloud particle numbers in both liquid and mixed-phase marine low clouds. Injection of CCN into the marine boundary layer can delay the collapse of the boundary layer and increase low-cloud albedo. Albedo increases are stronger for pure liquid clouds than mixed-phase clouds. Liquid precipitation can be suppressed by CCN injection, whereas ice precipitation (snow) is affected less; thus, the effectiveness of brightening mixed-phase clouds is lower than for liquid-only clouds. CCN injection into a clean regime results in a greater albedo increase than injection into a polluted regime, consistent with current knowledge about aerosol–cloud interactions. Unlike previous studies investigating warm clouds, dynamical changes in circulation owing to precipitation changes are small. According to these results, which are dependent upon the representation of ice nucleation processes in the employed microphysical scheme, Arctic geoengineering is unlikely to be effective as the sole means of altering the global radiation budget but could have substantial local radiative effects. PMID:25404677

  2. Modeling the Diagnostic Effects of Vegetation, Soil Albedo, and Dust on Mid-Holocene Saharan Climate

    Science.gov (United States)

    Thompson, A.; Poulsen, C. J.; Skinner, C. B.

    2017-12-01

    Unlike today, the Mid-Holocene (MH, 6,000 BP) African Sahara comprised of mixed vegetation and permanent lakes that supported human settlements. Climate proxies including leaf wax isotope, pollen, and dust flux records suggest that African monsoonal precipitation reached 31°N, compared to 15°N today. Changes in orbital forcing are partly responsible for the intensification of the African monsoon, but alone cannot explain the more humid MH Sahara. Modeling studies have shown that vegetation and soil albedo feedbacks greatly increase Saharan rainfall but still fall short of levels indicated by proxies. A recent study proposed that reduced Saharan dust concentrations due to greater vegetation coverage further increased MH rainfall. However, this study used idealized dust concentrations to improve proxy agreement and did not include the dust aerosol indirect effects in its model physics. Here we use CESM CAM5-chem to quantify the impact of diagnostic changes in Saharan dust, including indirect effects, on MH Saharan climate and compare it to changes in orbital forcing, soil albedo, and vegetation. Consistent with previous studies, a change in MH orbital forcing alone leads to a 20% increase in summer (June-Sept.) precipitation over Northern Africa (0°-30°N, 20°W-30°E) relative to a pre-industrial control, but still fails to reach the northward extent suggested by proxies. Adding MH soil albedo or vegetation increases summer precipitation by 45% and 52%, and shifts the maximum latitudinal rainfall extent 10° and 12° northward, respectively. These increases are 2.28 and 2.64 times greater than the precipitation increase from MH orbital forcing alone. MH soil albedo results in a dust burden increase of 22%, yet MH vegetation results in a 96% reduction. Both MH soil albedo and vegetation combined increase summer precipitation by 56% and 13° northward, an increase 2.84 times greater than the orbital forcing alone, and reduces dust burden by 97%. An additional

  3. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    Science.gov (United States)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  4. Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

    Directory of Open Access Journals (Sweden)

    L. Frey

    2017-07-01

    Full Text Available The effects of different aerosol types on cloud albedo are analysed using the linear relation between total albedo and cloud fraction found on a monthly mean scale in regions of subtropical marine stratocumulus clouds and the influence of simulated aerosol variations on this relation. Model experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5 are used to separately study the responses to increases in sulfate, non-sulfate and all anthropogenic aerosols. A cloud brightening on the month-to-month scale due to variability in the background aerosol is found to dominate even in the cases where anthropogenic aerosols are added. The aerosol composition is of importance for this cloud brightening, that is thereby region dependent. There is indication that absorbing aerosols to some extent counteract the cloud brightening but scene darkening with increasing aerosol burden is generally not supported, even in regions where absorbing aerosols dominate. Month-to-month cloud albedo variability also confirms the importance of liquid water content for cloud albedo. Regional, monthly mean cloud albedo is found to increase with the addition of anthropogenic aerosols and more so with sulfate than non-sulfate. Changes in cloud albedo between experiments are related to changes in cloud water content as well as droplet size distribution changes, so that models with large increases in liquid water path and/or cloud droplet number show large cloud albedo increases with increasing aerosol. However, no clear relation between model sensitivities to aerosol variations on the month-to-month scale and changes in cloud albedo due to changed aerosol burden is found.

  5. Inferring past land use-induced changes in surface albedo from satellite observations: a useful tool to evaluate model simulations

    Directory of Open Access Journals (Sweden)

    J. P. Boisier

    2013-03-01

    Full Text Available Regional cooling resulting from increases in surface albedo has been identified in several studies as the main biogeophysical effect of past land use-induced land cover changes (LCC on climate. However, the amplitude of this effect remains quite uncertain due to, among other factors, (a uncertainties in the extent of historical LCC and, (b differences in the way various models simulate surface albedo and more specifically its dependency on vegetation type and snow cover. We derived monthly albedo climatologies for croplands and four other land cover types from the Moderate Resolution Imaging Spectroradiometer (MODIS satellite observations. We then reconstructed the changes in surface albedo between preindustrial times and present-day by combining these climatologies with the land cover maps of 1870 and 1992 used by seven land surface models (LSMs in the context of the LUCID ("Land Use and Climate: identification of robust Impacts" intercomparison project. These reconstructions show surface albedo increases larger than 10% (absolute in winter, and larger than 2% in summer between 1870 and 1992 over areas that experienced intense deforestation in the northern temperate regions. The historical surface albedo changes estimated with MODIS data were then compared to those simulated by the various climate models participating in LUCID. The inter-model mean albedo response to LCC shows a similar spatial and seasonal pattern to the one resulting from the MODIS-based reconstructions, that is, larger albedo increases in winter than in summer, driven by the presence of snow. However, individual models show significant differences between the simulated albedo changes and the corresponding reconstructions, despite the fact that land cover change maps are the same. Our analyses suggest that the primary reason for those discrepancies is how LSMs parameterize albedo. Another reason, of secondary importance, results from differences in their simulated snow extent

  6. On the nature of the sea ice albedo feedback in simple models.

    Science.gov (United States)

    Moon, W; Wettlaufer, J S

    2014-08-01

    We examine the nature of the ice-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea ice. The central issue examined is how the evolution of the ice area is treated when modeling a partial ice cover using a two-category-thickness scheme; thin sea ice and open water in one category and "thick" sea ice in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional ice cover and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions. Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.

  7. Effect of ice-albedo feedback on global sensitivity in a one-dimensional radiative-convective climate model

    Science.gov (United States)

    Wang, W.-C.; Stone, P. H.

    1980-01-01

    The feedback between the ice albedo and temperature is included in a one-dimensional radiative-convective climate model. The effect of this feedback on global sensitivity to changes in solar constant is studied for the current climate conditions. This ice-albedo feedback amplifies global sensitivity by 26 and 39%, respectively, for assumptions of fixed cloud altitude and fixed cloud temperature. The global sensitivity is not affected significantly if the latitudinal variations of mean solar zenith angle and cloud cover are included in the global model. The differences in global sensitivity between one-dimensional radiative-convective models and energy balance models are examined. It is shown that the models are in close agreement when the same feedback mechanisms are included. The one-dimensional radiative-convective model with ice-albedo feedback included is used to compute the equilibrium ice line as a function of solar constant.

  8. VIS and NIR land surface albedo sensitivity of the Ent Terrestrial Biosphere Model to forcing leaf area index

    Science.gov (United States)

    Montes, C.; Kiang, N. Y.; Ni-Meister, W.; Yang, W.; Schaaf, C.; Aleinov, I. D.; Jonas, J.; Zhao, F. A.; Yao, T.; Wang, Z.; Sun, Q.; Carrer, D.

    2016-12-01

    Land surface albedo is a major controlling factor in vegetation-atmosphere transfers, modifying the components of the energy budget, the ecosystem productivity and patterns of regional and global climate. General Circulation Models (GCMs) are coupled to Dynamic Global Vegetation Models (DGVMs) to solve vegetation albedo by using simple schemes prescribing albedo based on vegetation classification, and approximations of canopy radiation transport for multiple plant functional types (PFTs). In this work, we aim at evaluating the sensitivity of the NASA Ent Terrestrial Biosphere Model (TBM), a demographic DGVM coupled to the NASA Goddard Institute for Space Studies (GISS) GCM, in estimating VIS and NIR surface albedo by using variable forcing leaf area index (LAI). The Ent TBM utilizes a new Global Vegetation Structure Dataset (GVSD) to account for geographically varying vegetation tree heights and densities, as boundary conditions to the gap-probability based Analytical Clumped Two-Stream (ACTS) canopy radiative transfer scheme (Ni-Meister et al., 2010). Land surface and vegetation characteristics for the Ent GVSD are obtained from a number of earth observation platforms and algorithms, including the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and plant functional types (PFTs) (Friedl et al., 2010), soil albedo derived from MODIS (Carrer et al., 2014), and vegetation height from the Geoscience Laser Altimeter System (GLAS) on board ICESat (Ice, Cloud, and land Elevation Satellite) (Simard et al., 2011; Tang et al., 2014). Three LAI products are used as input to ACTS/Ent TBM: MODIS MOD15A2H product (Yang et al., 2006), Beijing Normal University LAI (Yuan et al., 2011), and Global Data Sets of Vegetation (LAI3g) (Zhu et al. 2013). The sensitivity of the Ent TBM VIS and NIR albedo to the three LAI products is assessed, compared against the previous GISS GCM vegetation classification and prescribed Lambertian albedoes (Matthews, 1984), and against

  9. Empirical Modeling of Planetary Boundary Layer Dynamics Under Multiple Precipitation Scenarios Using a Two-Layer Soil Moisture Approach: An Example From a Semiarid Shrubland

    Science.gov (United States)

    Sanchez-Mejia, Zulia Mayari; Papuga, Shirley A.

    2017-11-01

    In semiarid regions, where water resources are limited and precipitation dynamics are changing, understanding land surface-atmosphere interactions that regulate the coupled soil moisture-precipitation system is key for resource management and planning. We present a modeling approach to study soil moisture and albedo controls on planetary boundary layer height (PBLh). We used Santa Rita Creosote Ameriflux and Tucson Airport atmospheric sounding data to generate empirical relationships between soil moisture, albedo, and PBLh. Empirical relationships showed that ˜50% of the variation in PBLh can be explained by soil moisture and albedo with additional knowledge gained by dividing the soil profile into two layers. Therefore, we coupled these empirical relationships with soil moisture estimated using a two-layer bucket approach to model PBLh under six precipitation scenarios. Overall we observed that decreases in precipitation tend to limit the recovery of the PBL at the end of the wet season. However, increases in winter precipitation despite decreases in summer precipitation may provide opportunities for positive feedbacks that may further generate more winter precipitation. Our results highlight that the response of soil moisture, albedo, and the PBLh will depend not only on changes in annual precipitation, but also on the frequency and intensity of this change. We argue that because albedo and soil moisture data are readily available at multiple temporal and spatial scales, developing empirical relationships that can be used in land surface-atmosphere applications have great potential for exploring the consequences of climate change.

  10. Albedo and heat transport in 3-D model simulations of the early Archean climate

    Directory of Open Access Journals (Sweden)

    H. Kienert

    2013-08-01

    Full Text Available At the beginning of the Archean eon (ca. 3.8 billion years ago, the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth". We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

  11. The Impact of Albedo Increase to Mitigate the Urban Heat Island in Terni (Italy Using the WRF Model

    Directory of Open Access Journals (Sweden)

    Elena Morini

    2016-10-01

    Full Text Available The impacts of the urban heat island (UHI phenomenon on energy consumption, air quality, and human health have been widely studied and described. Mitigation strategies have been developed to fight the UHI and its detrimental consequences. A potential countermeasure is the increase of urban albedo by using cool materials. Cool materials are highly reflective materials that can maintain lower surface temperatures and thus can present an effective solution to mitigate the UHI. Terni’s proven record of high temperatures along with related environmental and comfort issues in its urban areas have reflected the local consequences of global warming. On the other hand, it promoted integrated actions by the government and research institutes to investigate solutions to mitigate the UHI effects. In this study, the main goal is to investigate the effectiveness of albedo increase as a strategy to tackle the UHI, by using the Weather Research and Forecasting (WRF mesoscale model to simulate the urban climate of Terni (Italy. Three different scenarios through a summer heat wave in the summer of 2015 are analyzed. The Base Scenario, which simulates the actual conditions of the urban area, is the control case. In the Albedo Scenario (ALB Scenario, the albedo of the roof, walls and road of the whole urban area is increased. In the Albedo-Industrial Scenario (ALB-IND Scenario, the albedo of the roof, walls and road of the area occupied by the main industrial site of Terni, located in close proximity to the city center, is increased. The simulation results show that the UHI is decreased up to 2 °C both at daytime and at nighttime in the ALB and in ALB-IND Scenarios. Peak temperatures in the urban area can be decreased by 1 °C at daytime, and by about 2 °C at nighttime. Albedo increase in the area of interest might thus represent an opportunity to decrease the UHI effect and its consequences.

  12. Development of a MODIS-Derived Surface Albedo Data Set: An Improved Model Input for Processing the NSRDB

    Energy Technology Data Exchange (ETDEWEB)

    Maclaurin, Galen [National Renewable Energy Lab. (NREL), Golden, CO (United States); Sengupta, Manajit [National Renewable Energy Lab. (NREL), Golden, CO (United States); Xie, Yu [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gilroy, Nicholas [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-12-01

    A significant source of bias in the transposition of global horizontal irradiance to plane-of-array (POA) irradiance arises from inaccurate estimations of surface albedo. The current physics-based model used to produce the National Solar Radiation Database (NSRDB) relies on model estimations of surface albedo from a reanalysis climatalogy produced at relatively coarse spatial resolution compared to that of the NSRDB. As an input to spectral decomposition and transposition models, more accurate surface albedo data from remotely sensed imagery at finer spatial resolutions would improve accuracy in the final product. The National Renewable Energy Laboratory (NREL) developed an improved white-sky (bi-hemispherical reflectance) broadband (0.3-5.0 ..mu..m) surface albedo data set for processing the NSRDB from two existing data sets: a gap-filled albedo product and a daily snow cover product. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Terra and Aqua satellites have provided high-quality measurements of surface albedo at 30 arc-second spatial resolution and 8-day temporal resolution since 2001. The high spatial and temporal resolutions and the temporal coverage of the MODIS sensor will allow for improved modeling of POA irradiance in the NSRDB. However, cloud and snow cover interfere with MODIS observations of ground surface albedo, and thus they require post-processing. The MODIS production team applied a gap-filling methodology to interpolate observations obscured by clouds or ephemeral snow. This approach filled pixels with ephemeral snow cover because the 8-day temporal resolution is too coarse to accurately capture the variability of snow cover and its impact on albedo estimates. However, for this project, accurate representation of daily snow cover change is important in producing the NSRDB. Therefore, NREL also used the Integrated Multisensor Snow and Ice Mapping System data set, which provides daily snow cover observations of the

  13. Modeling glacier-surface albedo across Svalbard for the 1979-2015 period: The HiRSvaC500-α data set

    Science.gov (United States)

    Möller, Marco; Möller, Rebecca

    2017-03-01

    Albedo is an important quantity for determining the energy balance of snow and ice surfaces and thus also for the mass balance of glaciers. It is especially important in polar regions where shortwave radiation fluxes typically provide most of the energy input to a glacier. In order to use albedo data in any spatially distributed glaciological modeling, it is vital that the albedo fields are not only of high accuracy but also available on sufficiently high spatial resolution and in a manner that is consistent over time. This article presents the newly developed data set HiRSvaC500-α, which provides daily updated, gapless albedo fields for all glacierized areas of the Arctic archipelago Svalbard on a 500 m resolution over the period 1979-2015. Albedo modeling for creation of the data set is done using a multistep geostatistical approach on the basis of remotely sensed Moderate Resolution Imaging Spectroradiometer (MODIS) albedo data and gridded ERA-Interim climate data. Validation of the modeled HiRSvaC500-α albedo fields against in situ albedo measurements at automatic weather stations operated on two different glaciers suggests that the accuracy of the newly developed data set lies close to that of remotely sensed MODIS albedo data. An analysis of the HiRSvaC500-α albedo data set yields a mean annual-average albedo of 0.754 across all glaciers of Svalbard over 1979-2015. A decrease of albedo with time is found, following a highly significant (95% level) trend of -0.010 per decade. For certain subregions, this trend even reaches up to -0.014 per decade.

  14. The dependence of the ice-albedo feedback on atmospheric properties.

    Science.gov (United States)

    von Paris, P; Selsis, F; Kitzmann, D; Rauer, H

    2013-10-01

    Ice-albedo feedback is a potentially important destabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover, and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was used for the calculation of planetary albedos. We varied CO₂ partial pressures as well as the H₂O, CH₄, and O₃ content in the atmosphere for planets orbiting Sun-like and M type stars. Results suggest that, for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO₂ atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO₂ pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H₂O and CH₄ in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O₃ could also lead to a very strong decrease of the ice-albedo feedback at high CO₂ pressures.

  15. The influence of inter-annually varying albedo on regional climate and drought

    KAUST Repository

    Meng, Xianhong

    2013-05-05

    Albedo plays an important role in land-atmosphere interactions and local climate. This study presents the impact on simulating regional climate, and the evolution of a drought, when using the default climatological albedo as is usually done in regional climate modelling, or using the actual observed albedo which is rarely done. Here, time-varying satellite derived albedo data is used to update the lower boundary condition of the Weather Research and Forecasting regional climate model in order to investigate the influence of observed albedo on regional climate simulations and also potential changes to land-atmosphere feedback over south-east Australia. During the study period from 2000 to 2008, observations show that albedo increased with an increasingly negative precipitation anomaly, though it lagged precipitation by several months. Compared to in-situ observations, using satellite observed albedo instead of the default climatological albedo provided an improvement in the simulated seasonal mean air temperature. In terms of precipitation, both simulations reproduced the drought that occurred from 2002 through 2006. Using the observed albedo produced a drier simulation overall. During the onset of the 2002 drought, albedo changes enhanced the precipitation reduction by 20 % on average, over locations where it was active. The area experiencing drought increased 6.3 % due to the albedo changes. Two mechanisms for albedo changes to impact land-atmosphere drought feedback are investigated. One accounts for the increased albedo, leading to reduced turbulent heat flux and an associated decrease of moist static energy density in the planetary boundary layer; the other considers that enhanced local radiative heating, due to the drought, favours a deeper planetary boundary layer, subsequently decreasing the moist static energy density through entrainment of the free atmosphere. Analysis shows that drought related large-scale changes in the regional climate favour a

  16. Modeling Snow Regime in Cores of Small Planetary Bodies

    Science.gov (United States)

    Boukaré, C. E.; Ricard, Y. R.; Parmentier, E.; Parman, S. W.

    2017-12-01

    Observations of present day magnetic field on small planetary bodies such as Ganymede or Mercury challenge our understanding of planetary dynamo. Several mechanisms have been proposed to explain the origin of magnetic fields. Among the proposed scenarios, one family of models relies on snow regime. Snow regime is supported by experimental studies showing that melting curves can first intersect adiabats in regions where the solidifying phase is not gravitationaly stable. First solids should thus remelt during their ascent or descent. The effect of the snow zone on magnetic field generation remains an open question. Could magnetic field be generated in the snow zone? If not, what is the depth extent of the snow zone? How remelting in the snow zone drive compositional convection in the liquid layer? Several authors have tackled this question with 1D-spherical models. Zhang and Schubert, 2012 model sinking of the dense phase as internally heated convection. However, to our knowledge, there is no study on the convection structure associated with sedimentation and phase change at planetary scale. We extend the numerical model developped in [Boukare et al., 2017] to model snow dynamics in 2D Cartesian geometry. We build a general approach for modeling double diffusive convection coupled with solid-liquid phase change and phase separation. We identify several aspects that may govern the convection structure of the solidifying system: viscosity contrast between the snow zone and the liquid layer, crystal size, rate of melting/solidification and partitioning of light components during phase change.

  17. Europlanet/IDIS: Combining Diverse Planetary Observations and Models

    Science.gov (United States)

    Schmidt, Walter; Capria, Maria Teresa; Chanteur, Gerard

    2013-04-01

    Planetary research involves a diversity of research fields from astrophysics and plasma physics to atmospheric physics, climatology, spectroscopy and surface imaging. Data from all these disciplines are collected from various space-borne platforms or telescopes, supported by modelling teams and laboratory work. In order to interpret one set of data often supporting data from different disciplines and other missions are needed while the scientist does not always have the detailed expertise to access and utilize these observations. The Integrated and Distributed Information System (IDIS) [1], developed in the framework of the Europlanet-RI project, implements a Virtual Observatory approach ([2] and [3]), where different data sets, stored in archives around the world and in different formats, are accessed, re-formatted and combined to meet the user's requirements without the need of familiarizing oneself with the different technical details. While observational astrophysical data from different observatories could already earlier be accessed via Virtual Observatories, this concept is now extended to diverse planetary data and related model data sets, spectral data bases etc. A dedicated XML-based Europlanet Data Model (EPN-DM) [4] was developed based on data models from the planetary science community and the Virtual Observatory approach. A dedicated editor simplifies the registration of new resources. As the EPN-DM is a super-set of existing data models existing archives as well as new spectroscopic or chemical data bases for the interpretation of atmospheric or surface observations, or even modeling facilities at research institutes in Europe or Russia can be easily integrated and accessed via a Table Access Protocol (EPN-TAP) [5] adapted from the corresponding protocol of the International Virtual Observatory Alliance [6] (IVOA-TAP). EPN-TAP allows to search catalogues, retrieve data and make them available through standard IVOA tools if the access to the archive

  18. Modeling Tides, Planetary Waves, and Equatorial Oscillations in the MLT

    Science.gov (United States)

    Mengel, J. G.; Mayr, H. G.; Drob, D. P.; Porter, H. S.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    Applying Hines Doppler Spread Parameterization for gravity waves (GW), our 3D model reproduces some essential features that characterize the observed seasonal variations of tides and planetary waves in the upper mesosphere. In 2D, our model also reproduces the large Semi-Annual Oscillation (SAO) and Quasi Biennial Oscillation (QBO) observed in this region at low latitudes. It is more challenging to describe these features combined in a more comprehensive self consistent model, and we give a progress report that outlines the difficulties and reports some success. In 3D, the GW's are partially absorbed by tides and planetary waves to amplify them. Thus the waves are less efficient in generating the QBO and SAO at equatorial latitudes. Some of this deficiency is compensated by the fact that the GW activity is observed to be enhanced at low latitudes. Increasing the GW source has the desired effect to boost the QBO, but the effect is confined primarily to the stratosphere. With increasing altitude, the meridional circulation becomes more important in redistributing the momentum deposited in the background flow by the GW's. Another factor involved is the altitude at which the GW's originate, which we had originally chosen to be the surface. Numerical experiments show that moving this source altitude to the top of the troposphere significantly increases the efficiency for generating the QBO without affecting much the tides and planetary waves in the model. Attention to the details in which the GW source comes into play thus appears to be of critical importance in modeling the phenomenology of the MLT. Among the suite of numerical experiments reported, we present a simulation that produced significant variations of tides and planetary waves in the upper mesosphere. The effect is related to the QBO generated in the model, and GW filtering is the likely cause.

  19. Planetary Interior Modeling and Tectonic Implications

    Science.gov (United States)

    Phillips, R. J.

    1985-01-01

    A technique is described for estimating spectral admittance functions using Pioneer Venus gravity and topography data. These admittance functions provide a convenient means to carry out systematic geophysical studies over much of the surface of Venus with a variety of interior density models. The admittance functions are calculated in the observation space of line-of-sight (LOS) gravity. Both closed and open system petrological models are considered for the Tharsis region of Mars. An analytic theory for isostatic compensation on one-plate planet is applied, including membrane stresses in the lithosphere, self gravitation, and rotational ellipticity. Crucial to this stress modeling and also to the petrological modeling is the observation that the earliest fracturing seen in the Tharsis region is associated with isostatic stresses. The radial fractures that extend far from Tharsis are associated with an additional and/or a completely different mechanism.

  20. Sand Dune Albedo Feedback

    Directory of Open Access Journals (Sweden)

    Yosef Ashkenazy

    2018-02-01

    Full Text Available Sand dunes cover substantial parts of desert areas. Fully active dunes are bare, while fixed dunes are stabilized by vegetation and biogenic crust, and the dune activity is affected by the wind. Here we suggest the following atmosphere-sand dune feedback: spatial differences in the dunes’ vegetation and biogenic crust cover lead to differences in albedo as the albedo of bare sand is larger than that of vegetation and biogenic crust. This leads to a higher temperature over the vegetated area, resulting in air flow from the bare dune area to the vegetated dune area, thus increasing the wind activity over the vegetated dune area. In turn, this leads to enhanced stress on the vegetation and enhanced dune activity and thus to a decrease in vegetation. These changes in vegetation cover affect the surface albedo, leading to a change in wind activity. We examined this feedback using an atmospheric general circulation model, Weather Research and Forecasting (WRF, in selected regions of the northwestern Negev Desert and the Sahara/Sahel region, and we show that changes in surface albedo do indeed lead to significantly enhanced wind activity over the lower albedo region. We then incorporated this feedback into a simple vegetated dune model, showing that the multiple states associated with active and fixed dunes can be obtained for a larger range of parameters and that the stables states become more extreme (i.e., the fixed dune state becomes more vegetated and the active dune state becomes less vegetated.

  1. Albedo boundary conditions for global calculations of thermal nuclear reactors with the model of discrete ordinates to two energy groups

    International Nuclear Information System (INIS)

    Nunes, Carlos Eduardo de Araujo

    2011-01-01

    As neutron fission events do not take place in the non-multiplying regions of nuclear reactors, e.g., moderator, reflector, and structural core, these regions do not generate power and the computational efficiency of nuclear reactor global calculations can hence be improved by eliminating the explicit numerical calculations within the non-multiplying regions around the active domain. Discussed here is the computational efficiency of approximate discrete ordinates (SN) albedo boundary conditions for two-energy group eigenvalue problems in X, Y geometry. Albedo, the Latin word for w hiteness , was originally defined as the fraction of incident light reflected diffusely by a surface. This Latin word has remained the usual scientific term in astronomy and in this dissertation this concept is extended for the reflection of neutrons. The non-standard SN albedo substitutes approximately the reflector region around the active domain, as we neglect the transverse leakage terms within the non-multiplying reflector. Should the problem have no transverse leakage terms, i.e., one dimensional slab geometry, then the offered albedo boundary conditions are exact. By computational efficiency we mean analyzing the accuracy of the numerical results versus the CPU execution time of each run for a given model problem. Numerical results to two 1/4 symmetric test problems are shown to illustrate this efficiency analysis. (author)

  2. Observational determination of albedo decrease caused by vanishing Arctic sea ice.

    Science.gov (United States)

    Pistone, Kristina; Eisenman, Ian; Ramanathan, V

    2014-03-04

    The decline of Arctic sea ice has been documented in over 30 y of satellite passive microwave observations. The resulting darkening of the Arctic and its amplification of global warming was hypothesized almost 50 y ago but has yet to be verified with direct observations. This study uses satellite radiation budget measurements along with satellite microwave sea ice data to document the Arctic-wide decrease in planetary albedo and its amplifying effect on the warming. The analysis reveals a striking relationship between planetary albedo and sea ice cover, quantities inferred from two independent satellite instruments. We find that the Arctic planetary albedo has decreased from 0.52 to 0.48 between 1979 and 2011, corresponding to an additional 6.4 ± 0.9 W/m(2) of solar energy input into the Arctic Ocean region since 1979. Averaged over the globe, this albedo decrease corresponds to a forcing that is 25% as large as that due to the change in CO2 during this period, considerably larger than expectations from models and other less direct recent estimates. Changes in cloudiness appear to play a negligible role in observed Arctic darkening, thus reducing the possibility of Arctic cloud albedo feedbacks mitigating future Arctic warming.

  3. Solar Irradiance from GOES Albedo performance in a Hydrologic Model Simulation of Snowmelt Runoff

    Science.gov (United States)

    Sumargo, E.; Cayan, D. R.; McGurk, B. J.

    2015-12-01

    In many hydrologic modeling applications, solar radiation has been parameterized using commonly available measures, such as the daily temperature range, due to scarce in situ solar radiation measurement network. However, these parameterized estimates often produce significant biases. Here we test hourly solar irradiance derived from the Geostationary Operational Environmental Satellite (GOES) visible albedo product, using several established algorithms. Focusing on the Sierra Nevada and White Mountain in California, we compared the GOES irradiance and that from a traditional temperature-based algorithm with incoming irradiance from pyranometers at 19 stations. The GOES based estimates yielded 21-27% reduction in root-mean-squared error (average over 19 sites). The derived irradiance is then prescribed as an input to Precipitation-Runoff Modeling System (PRMS). We constrain our experiment to the Tuolumne River watershed and focus our attention on the winter and spring of 1996-2014. A root-mean-squared error reduction of 2-6% in daily inflow to Hetch Hetchy at the lower end of the Tuolumne catchment was achieved by incorporating the insolation estimates at only 8 out of 280 Hydrologic Response Units (HRUs) within the basin. Our ongoing work endeavors to apply satellite-derived irradiance at each individual HRU.

  4. The impact of black carbon deposition on snowpack and streamflow in the Wasatch mountains in Utah: A study using MODIS albedo data, statistical modeling and machine learning

    Science.gov (United States)

    Panthail, Jai Kanth

    Salt Lake City, located at the base of the Wasatch mountain range in Utah, receives a majority of its potable water from a system of mountain creeks. Snowmelt runoff from mountain watersheds provides the city a clean and relatively inexpensive water supply, and has been a key driver in the city's growth and prosperity. There has been keen interest recently on the possible impact of the deposition of darkening matter, such as dust and black carbon (BC) on the snow, which might lead to a decrease in its 'albedo' or reflective capacity. Such a decrease is expected to result in faster melting of the snow, shifting springtime streamflows to winter. This study aimed to develop a modeling framework to estimate the impact on snowmelt-driven runoff due to various BC deposition scenarios. An albedo simulation model, Snow, Ice, and Aerosol Radiation (SNICAR) model, was used to understand the evolution of albedo under different BC loadings. An Albedo-Snow Water Equivalent (A-SWE) model was developed using a machine learning technique, 'Random Forests', to quantify the effect on the state of snowpack under various albedo-change scenarios. An Albedo-Snow Water Equivalent-Streamflow (A-SWE-S) model was designed using an advanced statistical modeling technique, 'Generalized Additive Models (GAMs)', to extend the analysis to streamflow variations. All models were tested and validated using robust k-fold cross-validation. Albedo data were obtained from NASA's MODIS satellite platform. The key results found the snowpack to be depleted 2-3 weeks later with an albedo increase between 5-10% above current conditions, and 1-2 weeks earlier under albedo decrease of 5-10% below current conditions. Future work will involve improving the A-SWE-S model by better accounting for lagged effects, and the use of results from both models in a city-wide systems model to understand water supply reliability under combined deposition and climate change scenarios.

  5. Distinguishing the albedo of exoplanets from stellar activity

    Science.gov (United States)

    Serrano, L. M.; Barros, S. C. C.; Oshagh, M.; Santos, N. C.; Faria, J. P.; Demangeon, O.; Sousa, S. G.; Lendl, M.

    2018-03-01

    Context. Light curves show the flux variation from the target star and its orbiting planets as a function of time. In addition to the transit features created by the planets, the flux also includes the reflected light component of each planet, which depends on the planetary albedo. This signal is typically referred to as phase curve and could be easily identified if there were no additional noise. As well as instrumental noise, stellar activity, such as spots, can create a modulation in the data, which may be very difficult to distinguish from the planetary signal. Aims: We analyze the limitations imposed by the stellar activity on the detection of the planetary albedo, considering the limitations imposed by the predicted level of instrumental noise and the short duration of the obervations planned in the context of the CHEOPS mission. Methods: As initial condition, we have assumed that each star is characterized by just one orbiting planet. We built mock light curves that included a realistic stellar activity pattern, the reflected light component of the planet and an instrumental noise level, which we have chosen to be at the same level as predicted for CHEOPS. We then fit these light curves to try to recover the reflected light component, assuming the activity patterns can be modeled with a Gaussian process. Results: We estimate that at least one full stellar rotation is necessary to obtain a reliable detection of the planetary albedo. This result is independent of the level of noise, but it depends on the limitation of the Gaussian process to describe the stellar activity when the light curve time-span is shorter than the stellar rotation. As an additional result, we found that with a 6.5 magnitude star and the noise level of CHEOPS, it is possible to detect the planetary albedo up to a lower limit of Rp = 0.03 R*. Finally, in presence of typical CHEOPS gaps in the simulations, we confirm that it is still possible to obtain a reliable albedo.

  6. Planetary wave prediction: Benefits of tropical data and global models

    Science.gov (United States)

    Somerville, R. C. J.

    1985-01-01

    Skillful numerical predictions of midlatitude atmospheric planetary waves generally require both tropical data for the initial conditions and a global domain for the forecast model. The lack of either adequate tropical observations or a global domain typically leads to a significant degradation of forecast skill in middle latitudes within the first one to three days of the forecast period. These effects were first discovered by numerical experimentation. They were subsequently explained theoretically, and their importance for practical forecasting was confirmed in a series of prediction experiments using FGGE data.

  7. Flyover Modeling of Planetary Pits - Undergraduate Student Instrument Project

    Science.gov (United States)

    Bhasin, N.; Whittaker, W.

    2015-12-01

    On the surface of the moon and Mars there are hundreds of skylights, which are collapsed holes that are believed to lead to underground caves. This research uses Vision, Inertial, and LIDAR sensors to build a high resolution model of a skylight as a landing vehicle flies overhead. We design and fabricate a pit modeling instrument to accomplish this task, implement software, and demonstrate sensing and modeling capability on a suborbital reusable launch vehicle flying over a simulated pit. Future missions on other planets and moons will explore pits and caves, led by the technology developed by this research. Sensor software utilizes modern graph-based optimization techniques to build 3D models using camera, LIDAR, and inertial data. The modeling performance was validated with a test flyover of a planetary skylight analog structure on the Masten Xombie sRLV. The trajectory profile closely follows that of autonomous planetary powered descent, including translational and rotational dynamics as well as shock and vibration. A hexagonal structure made of shipping containers provides a terrain feature that serves as an appropriate analog for the rim and upper walls of a cylindrical planetary skylight. The skylight analog floor, walls, and rim are modeled in elevation with a 96% coverage rate at 0.25m2 resolution. The inner skylight walls have 5.9cm2 color image resolution and the rims are 6.7cm2 with measurement precision superior to 1m. The multidisciplinary student team included students of all experience levels, with backgrounds in robotics, physics, computer science, systems, mechanical and electrical engineering. The team was commited to authentic scientific experimentation, and defined specific instrument requirements and measurable experiment objectives to verify successful completion.This work was made possible by the NASA Undergraduate Student Instrument Project Educational Flight Opportunity 2013 program. Additional support was provided by the sponsorship of an

  8. Fractal planetary rings: Energy inequalities and random field model

    Science.gov (United States)

    Malyarenko, Anatoliy; Ostoja-Starzewski, Martin

    2017-12-01

    This study is motivated by a recent observation, based on photographs from the Cassini mission, that Saturn’s rings have a fractal structure in radial direction. Accordingly, two questions are considered: (1) What Newtonian mechanics argument in support of such a fractal structure of planetary rings is possible? (2) What kinematics model of such fractal rings can be formulated? Both challenges are based on taking planetary rings’ spatial structure as being statistically stationary in time and statistically isotropic in space, but statistically nonstationary in space. An answer to the first challenge is given through an energy analysis of circular rings having a self-generated, noninteger-dimensional mass distribution [V. E. Tarasov, Int. J. Mod Phys. B 19, 4103 (2005)]. The second issue is approached by taking the random field of angular velocity vector of a rotating particle of the ring as a random section of a special vector bundle. Using the theory of group representations, we prove that such a field is completely determined by a sequence of continuous positive-definite matrix-valued functions defined on the Cartesian square F2 of the radial cross-section F of the rings, where F is a fat fractal.

  9. Representation of vegetation effects on the snow-covered albedo in the Noah land surface model with multiple physics options

    OpenAIRE

    S. Park; S. K. Park

    2015-01-01

    Snow albedo plays a critical role in calculating the energy budget, but parameterization of the snow surface albedo is still under great uncertainty. It varies with snow grain size, snow cover thickness, snow age, forest shading factor and other variables. Snow albedo of forest is typically lower than that of short vegetation; thus snow albedo is dependent on the spatial distributions of characteristic land cover and on the canopy density and structure. In the No...

  10. Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000-2013)

    NARCIS (Netherlands)

    Alexander, P. M.; Tedesco, M.; Fettweis, X.; Van De Wal, R. S W|info:eu-repo/dai/nl/101899556; Smeets, C. J P P|info:eu-repo/dai/nl/191522236; Van Den Broeke, M. R.|info:eu-repo/dai/nl/073765643

    2014-01-01

    Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July,

  11. Joint DEnKF-albedo assimilation scheme that considers the common land model subgrid heterogeneity and a snow density-based observation operator for improving snow depth simulations

    Science.gov (United States)

    Xu, Jianhui; Zhang, Feifei; Zhao, Yi; Shu, Hong; Zhong, Kaiwen

    2016-07-01

    For the large-area snow depth (SD) data sets with high spatial resolution in the Altay region of Northern Xinjiang, China, we present a deterministic ensemble Kalman filter (DEnKF)-albedo assimilation scheme that considers the common land model (CoLM) subgrid heterogeneity. In the albedo assimilation of DEnKF-albedo, the assimilated albedos over each subgrid tile are estimated with the MCD43C1 bidirectional reflectance distribution function (BRDF) parameters product and CoLM calculated solar zenith angle. The BRDF parameters are hypothesized to be consistent over all subgrid tiles within a specified grid. In the SCF assimilation of DEnKF-albedo, a DEnKF combining a snow density-based observation operator considers the effects of the CoLM subgrid heterogeneity and is employed to assimilate MODIS SCF to update SD states over all subgrid tiles. The MODIS SCF over a grid is compared with the area-weighted sum of model predicted SCF over all the subgrid tiles within the grid. The results are validated with in situ SD measurements and AMSR-E product. Compared with the simulations, the DEnKF-albedo scheme can reduce errors of SD simulations and accurately simulate the seasonal variability of SD. Furthermore, it can improve simulations of SD spatiotemporal distribution in the Altay region, which is more accurate and shows more detail than the AMSR-E product.

  12. An energy balance model exploration of the impacts of interactions between surface albedo, cloud cover and water vapor on polar amplification

    Science.gov (United States)

    Södergren, A. Helena; McDonald, Adrian J.; Bodeker, Gregory E.

    2017-11-01

    We examine the effects of non-linear interactions between surface albedo, water vapor and cloud cover (referred to as climate variables) on amplified warming of the polar regions, using a new energy balance model. Our simulations show that the sum of the contributions to surface temperature changes due to any variable considered in isolation is smaller than the temperature changes from coupled feedback simulations. This non-linearity is strongest when all three climate variables are allowed to interact. Surface albedo appears to be the strongest driver of this non-linear behavior, followed by water vapor and clouds. This is because increases in longwave radiation absorbed by the surface, related to increases in water vapor and clouds, and increases in surface absorbed shortwave radiation caused by a decrease in surface albedo, amplify each other. Furthermore, our results corroborate previous findings that while increases in cloud cover and water vapor, along with the greenhouse effect itself, warm the polar regions, water vapor also significantly warms equatorial regions, which reduces polar amplification. Changes in surface albedo drive large changes in absorption of incoming shortwave radiation, thereby enhancing surface warming. Unlike high latitudes, surface albedo change at low latitudes are more constrained. Interactions between surface albedo, water vapor and clouds drive larger increases in temperatures in the polar regions compared to low latitudes. This is in spite of the fact that, due to a forcing, cloud cover increases at high latitudes and decreases in low latitudes, and that water vapor significantly enhances warming at low latitudes.

  13. Photoionization modelling of planetary nebulae - II. Galactic bulge nebulae, a comparison with literature results

    NARCIS (Netherlands)

    van Hoof, PAM; Van de Steene, GC

    1999-01-01

    We have constructed photoionization models of five galactic bulge planetary nebulae using our automatic method, which enables a fully self-consistent determination of the physical parameters of a planetary nebula. The models are constrained using the spectrum, the IRAS and radio fluxes and the

  14. Influence of Dust and Black Carbon on the Snow Albedo in the NASA Goddard Earth Observing System Version 5 Land Surface Model

    Science.gov (United States)

    Yasunari, Teppei J.; Koster, Randal D.; Lau, K. M.; Aoki, Teruo; Sud, Yogesh C.; Yamazaki, Takeshi; Motoyoshi, Hiroki; Kodama, Yuji

    2011-01-01

    Present-day land surface models rarely account for the influence of both black carbon and dust in the snow on the snow albedo. Snow impurities increase the absorption of incoming shortwave radiation (particularly in the visible bands), whereby they have major consequences for the evolution of snowmelt and life cycles of snowpack. A new parameterization of these snow impurities was included in the catchment-based land surface model used in the National Aeronautics and Space Administration Goddard Earth Observing System version 5. Validation tests against in situ observed data were performed for the winter of 2003.2004 in Sapporo, Japan, for both the new snow albedo parameterization (which explicitly accounts for snow impurities) and the preexisting baseline albedo parameterization (which does not). Validation tests reveal that daily variations of snow depth and snow surface albedo are more realistically simulated with the new parameterization. Reasonable perturbations in the assigned snow impurity concentrations, as inferred from the observational data, produce significant changes in snowpack depth and radiative flux interactions. These findings illustrate the importance of parameterizing the influence of snow impurities on the snow surface albedo for proper simulation of the life cycle of snow cover.

  15. Ground tests of the Dynamic Albedo of Neutron instrument operation in the passive mode with a Martian soil model

    Science.gov (United States)

    Shvetsov, V. N.; Dubasov, P. V.; Golovin, D. V.; Kozyrev, A. S.; Krylov, A. R.; Krylov, V. A.; Litvak, M. L.; Malakhov, A. V.; Mitrofanov, I. G.; Mokrousov, M. I.; Sanin, A. B.; Timoshenko, G. N.; Vostrukhin, A. A.; Zontikov, A. O.

    2017-07-01

    The results of the Dynamic Albedo of Neutrons (DAN) instrument ground tests in the passive mode of operation are presented in comparison with the numerical calculations. These test series were conducted to support the current surface measurements of DAN onboard the MSL Curiosity rover. The instrument sensitivity to detect thin subsurface layers of water ice buried at different depths in the analog of Martian soil has been evaluated during these tests. The experiments have been done with a radioisotope Pu-Be neutron source (analog of the MMRTG neutron source onboard the Curiosity rover) and the Martian soil model assembled from silicon-rich window glass pane. Water ice layers were simulated with polyethylene sheets. All experiments have been performed at the test facility built at the Joint Institute for Nuclear Research (Dubna, Russia).

  16. The diversity of planetary system from formation/composition population synthesis models

    Science.gov (United States)

    Alibert, Yann; thiabaud, amaury; marboeuf, ulysses; swoboda, david; benz, willy; mezger, klaus; leya, ingo

    2015-12-01

    Extrasolar planetary systems show an extreme diversity in mass and orbital architecture. Explaining this diversity is one of the key challenges for theoretical models and requires understanding the formation, composition and evolution of planetary systems from the stage of the protoplanetary disk up to the full mature planetary system. Such an effort needs the development of end-to-end, necessarily simplified, formation models used in a population synthesis approach. We present in this contribution such planetary system formation and composition models. Our planetary system formation models include the following effects: planetary growth by capture of solids and gas, protoplanetary disk structure and evolution, planet-planet and planet-disk interactions. In addition, we compute the composition of the solids and gas in the protoplanetary disk and their evolution with time. The formation and composition models allow therefore the determination of the composition of planets in terms of refractory elements (Mg, Si, Fe, etc…) as well as volatile compounds (water, CO2, CO, NH3, etc…), in a way that is self-consistent with the formation process of the different members of the planetary system. We will show the results of these formation/composition models, and will compare the diversity of observed and synthetic planetary systems. Considering the solar system, we will show how different formation scenarios translate into different planetary compositions. Finally, we will demonstrate how the simultaneous determination of mass and radius of a statistical number of warm to cold earth to neptune mass bodies at different ages can be used to constrain the composition (in particular the volatile content) of planets, and how the same observations (mass, radius, period) can be used in order to select planets that are best suited for follow-up habitability studies.

  17. Shaping of planetary nebulae

    International Nuclear Information System (INIS)

    Balick, B.

    1987-01-01

    The phases of stellar evolution and the development of planetary nebulae are examined. The relation between planetary nebulae and red giants is studied. Spherical and nonspherical cases of shaping planetaries with stellar winds are described. CCD images of nebulae are analyzed, and it is determined that the shape of planetary nebulae depends on ionization levels. Consideration is given to calculating the distances of planetaries using radio images, and molecular hydrogen envelopes which support the wind-shaping model of planetary nebulae

  18. Public Outreach with NASA Lunar and Planetary Mapping and Modeling

    Science.gov (United States)

    Law, E.; Day, B.

    2017-09-01

    NASA's Trek family of online portals is an exceptional collection of resources making it easy for students and the public to explore surfaces of planetary bodies using real data from real missions. Exotic landforms on other worlds and our plans to explore them provide inspiring context for science and technology lessons in classrooms, museums, and at home. These portals can be of great value to formal and informal educators, as well as to scientists working to share the excitement of the latest developments in planetary science, and can significantly enhance visibility and public engagement in missions of exploration.

  19. Modelling Mean Albedo of Individual Roofs in Complex Urban Areas Using Satellite Images and Airborne Laser Scanning Point Clouds

    Science.gov (United States)

    Kalantar, B.; Mansor, S.; Khuzaimah, Z.; Sameen, M. Ibrahim; Pradhan, B.

    2017-09-01

    Knowledge of surface albedo at individual roof scale is important for mitigating urban heat islands and understanding urban climate change. This study presents a method for quantifying surface albedo of individual roofs in a complex urban area using the integration of Landsat 8 and airborne LiDAR data. First, individual roofs were extracted from airborne LiDAR data and orthophotos using optimized segmentation and supervised object based image analysis (OBIA). Support vector machine (SVM) was used as a classifier in OBIA process for extracting individual roofs. The user-defined parameters required in SVM classifier were selected using v-fold cross validation method. After that, surface albedo was calculated for each individual roof from Landsat images. Finally, thematic maps of mean surface albedo of individual roofs were generated in GIS and the results were discussed. Results showed that the study area is covered by 35% of buildings varying in roofing material types and conditions. The calculated surface albedo of buildings ranged from 0.16 to 0.65 in the study area. More importantly, the results indicated that the types and conditions of roofing materials significantly effect on the mean value of surface albedo. Mean albedo of new concrete, old concrete, new steel, and old steel were found to be equal to 0.38, 0.26, 0.51, and 0.44 respectively. Replacing old roofing materials with new ones should highly prioritized.

  20. MODELLING MEAN ALBEDO OF INDIVIDUAL ROOFS IN COMPLEX URBAN AREAS USING SATELLITE IMAGES AND AIRBORNE LASER SCANNING POINT CLOUDS

    Directory of Open Access Journals (Sweden)

    B. Kalantar

    2017-09-01

    Full Text Available Knowledge of surface albedo at individual roof scale is important for mitigating urban heat islands and understanding urban climate change. This study presents a method for quantifying surface albedo of individual roofs in a complex urban area using the integration of Landsat 8 and airborne LiDAR data. First, individual roofs were extracted from airborne LiDAR data and orthophotos using optimized segmentation and supervised object based image analysis (OBIA. Support vector machine (SVM was used as a classifier in OBIA process for extracting individual roofs. The user-defined parameters required in SVM classifier were selected using v-fold cross validation method. After that, surface albedo was calculated for each individual roof from Landsat images. Finally, thematic maps of mean surface albedo of individual roofs were generated in GIS and the results were discussed. Results showed that the study area is covered by 35% of buildings varying in roofing material types and conditions. The calculated surface albedo of buildings ranged from 0.16 to 0.65 in the study area. More importantly, the results indicated that the types and conditions of roofing materials significantly effect on the mean value of surface albedo. Mean albedo of new concrete, old concrete, new steel, and old steel were found to be equal to 0.38, 0.26, 0.51, and 0.44 respectively. Replacing old roofing materials with new ones should highly prioritized.

  1. Parameterizations for narrowband and broadband albedo of pure snow and snow containing mineral dust and black carbon

    Science.gov (United States)

    Dang, Cheng; Brandt, Richard E.; Warren, Stephen G.

    2015-06-01

    The reduction of snow spectral albedo by black carbon (BC) and mineral dust, both alone and in combination, is computed using radiative transfer modeling. Broadband albedo is shown for mass fractions covering the full range from pure snow to pure BC and pure dust, and for snow grain radii from 5 µm to 2500 µm, to cover the range of possible grain sizes on planetary surfaces. Parameterizations are developed for opaque homogeneous snowpacks for three broad bands used in general circulation models and several narrower bands. They are functions of snow grain radius and the mass fraction of BC and/or dust and are valid up to BC content of 10 ppm, needed for highly polluted snow. A change of solar zenith angle can be mimicked by changing grain radius. A given mass fraction of BC causes greater albedo reduction in coarse-grained snow; BC and grain radius can be combined into a single variable to compute the reduction of albedo relative to pure snow. The albedo reduction by BC is less if the snow contains dust, a common situation on mountain glaciers and in agricultural and grazing lands. Measured absorption spectra of mineral dust are critically reviewed as a basis for specifying dust properties for modeling. The effect of dust on snow albedo at visible wavelengths can be represented by an "equivalent BC" amount, scaled down by a factor of about 200. Dust has little effect on the near-IR albedo because the near-IR albedo of pure dust is similar to that of pure snow.

  2. Little Earth Experiment: An instrument to model planetary cores.

    Science.gov (United States)

    Aujogue, Kélig; Pothérat, Alban; Bates, Ian; Debray, François; Sreenivasan, Binod

    2016-08-01

    In this paper, we present a new experimental facility, Little Earth Experiment, designed to study the hydrodynamics of liquid planetary cores. The main novelty of this apparatus is that a transparent electrically conducting electrolyte is subject to extremely high magnetic fields (up to 10 T) to produce electromagnetic effects comparable to those produced by moderate magnetic fields in planetary cores. This technique makes it possible to visualise for the first time the coupling between the principal forces in a convection-driven dynamo by means of Particle Image Velocimetry (PIV) in a geometry relevant to planets. We first present the technology that enables us to generate these forces and implement PIV in a high magnetic field environment. We then show that the magnetic field drastically changes the structure of convective plumes in a configuration relevant to the tangent cylinder region of the Earth's core.

  3. Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo

    Science.gov (United States)

    Cook, Joseph M.; Hodson, Andrew J.; Gardner, Alex S.; Flanner, Mark; Tedstone, Andrew J.; Williamson, Christopher; Irvine-Fynn, Tristram D. L.; Nilsson, Johan; Bryant, Robert; Tranter, Martyn

    2017-11-01

    The darkening effects of biological impurities on ice and snow have been recognised as a control on the surface energy balance of terrestrial snow, sea ice, glaciers and ice sheets. With a heightened interest in understanding the impacts of a changing climate on snow and ice processes, quantifying the impact of biological impurities on ice and snow albedo (bioalbedo) and its evolution through time is a rapidly growing field of research. However, rigorous quantification of bioalbedo has remained elusive because of difficulties in isolating the biological contribution to ice albedo from that of inorganic impurities and the variable optical properties of the ice itself. For this reason, isolation of the biological signature in reflectance data obtained from aerial/orbital platforms has not been achieved, even when ground-based biological measurements have been available. This paper provides the cell-specific optical properties that are required to model the spectral signatures and broadband darkening of ice. Applying radiative transfer theory, these properties provide the physical basis needed to link biological and glaciological ground measurements with remotely sensed reflectance data. Using these new capabilities we confirm that biological impurities can influence ice albedo, then we identify 10 challenges to the measurement of bioalbedo in the field with the aim of improving future experimental designs to better quantify bioalbedo feedbacks. These challenges are (1) ambiguity in terminology, (2) characterising snow or ice optical properties, (3) characterising solar irradiance, (4) determining optical properties of cells, (5) measuring biomass, (6) characterising vertical distribution of cells, (7) characterising abiotic impurities, (8) surface anisotropy, (9) measuring indirect albedo feedbacks, and (10) measurement and instrument configurations. This paper aims to provide a broad audience of glaciologists and biologists with an overview of radiative transfer and

  4. Quantifying bioalbedo: a new physically based model and discussion of empirical methods for characterising biological influence on ice and snow albedo

    Directory of Open Access Journals (Sweden)

    J. M. Cook

    2017-11-01

    Full Text Available The darkening effects of biological impurities on ice and snow have been recognised as a control on the surface energy balance of terrestrial snow, sea ice, glaciers and ice sheets. With a heightened interest in understanding the impacts of a changing climate on snow and ice processes, quantifying the impact of biological impurities on ice and snow albedo (bioalbedo and its evolution through time is a rapidly growing field of research. However, rigorous quantification of bioalbedo has remained elusive because of difficulties in isolating the biological contribution to ice albedo from that of inorganic impurities and the variable optical properties of the ice itself. For this reason, isolation of the biological signature in reflectance data obtained from aerial/orbital platforms has not been achieved, even when ground-based biological measurements have been available. This paper provides the cell-specific optical properties that are required to model the spectral signatures and broadband darkening of ice. Applying radiative transfer theory, these properties provide the physical basis needed to link biological and glaciological ground measurements with remotely sensed reflectance data. Using these new capabilities we confirm that biological impurities can influence ice albedo, then we identify 10 challenges to the measurement of bioalbedo in the field with the aim of improving future experimental designs to better quantify bioalbedo feedbacks. These challenges are (1 ambiguity in terminology, (2 characterising snow or ice optical properties, (3 characterising solar irradiance, (4 determining optical properties of cells, (5 measuring biomass, (6 characterising vertical distribution of cells, (7 characterising abiotic impurities, (8 surface anisotropy, (9 measuring indirect albedo feedbacks, and (10 measurement and instrument configurations. This paper aims to provide a broad audience of glaciologists and biologists with an overview of

  5. Assimilation of MODIS Ice Surface Temperature and Albedo into the Snow and Ice Model CROCUS Over the Greenland Ice Sheet Along the K-transect Stations

    Science.gov (United States)

    Navari, M.; Margulis, S. A.; Bateni, S. M.; Alexander, P. M.; Tedesco, M.

    2016-12-01

    Estimating the Greenland Ice Sheet (GrIS) surface mass balance (SMB) is an important component of current and future projections of sea level rise. In situ measurement provides direct estimates of the SMB, but are inherently limited by their spatial extent and representativeness. Given this limitation, physically based regional climate models (RCMs) are critical for understanding GrIS physical processes and estimating of the GrIS SMB. However, the uncertainty in estimates of SMB from RCMs is still high. Surface remote sensing (RS) has been used as a complimentary tool to characterize various aspects related to the SMB. The difficulty of using these data streams is that the links between them and the SMB terms are most often indirect and implicit. Given the lack of in situ information, imperfect models, and under-utilized RS data it is critical to merge the available data in a systematic way to better characterize the spatial and temporal variation of the GrIS SMB. This work proposes a data assimilation (DA) framework that yields temporally-continuous and physically consistent SMB estimates that benefit from state-of-the-art models and relevant remote sensing data streams. Ice surface temperature (IST) is the most important factor that regulates partitioning of the net radiation into the subsurface snow/ice, sensible and latent heat fluxes and plays a key role in runoff generation. Therefore it can be expected that a better estimate of surface temperature from a data assimilation system would contribute to a better estimate of surface mass fluxes. Albedo plays an important role in the surface energy balance of the GrIS. However, even advanced albedo modules are not adequate to simulate albedo over the GrIS. Therefore, merging remotely sensed albedo product into a physically based model has a potential to improve the estimates of the GrIS SMB. In this work a MODIS-derived IST and a 16-day albedo product are independently assimilated into the snow and ice model CROCUS

  6. An Antarctic research outpost as a model for planetary exploration.

    Science.gov (United States)

    Andersen, D T; McKay, C P; Wharton, R A; Rummel, J D

    1990-01-01

    During the next 50 years, human civilization may well begin expanding into the solar system. This colonization of extraterrestrial bodies will most likely begin with the establishment of small research outposts on the Moon and/or Mars. In all probability these facilities, designed primarily for conducting exploration and basic science, will have international participation in their crews, logistical support and funding. High fidelity Earth-based simulations of planetary exploration could help prepare for these expensive and complex operations. Antarctica provides one possible venue for such a simulation. The hostile and remote dry valleys of southern Victoria Land offer a valid analog to the Martian environment but are sufficiently accessible to allow routine logistical support and to assure the relative safety of their inhabitants. An Antarctic research outpost designed as a planetary exploration simulation facility would have great potential as a testbed and training site for the operation of future Mars bases and represents a near-term, relatively low-cost alternative to other precursor activities. Antarctica already enjoys an international dimension, an aspect that is more than symbolically appropriate to an international endeavor of unprecedented scientific and social significance--planetary exploration by humans. Potential uses of such a facility include: 1) studying human factors in an isolated environment (including long-term interactions among an international crew); 2) testing emerging technologies (e.g., advanced life support facilities such as a partial bioregenerative life support system, advanced analytical and sample acquisition instrumentation and equipment, etc.); and 3) conducting basic scientific research similar to the research that will be conducted on Mars, while contributing to the planning for human exploration. (Research of this type is already ongoing in Antarctica).

  7. Modeling of the process of gear shifting in planetary gear trains of motor vehicles

    Directory of Open Access Journals (Sweden)

    Aleksandar R. Grkić

    2011-04-01

    Full Text Available Gear boxes, i. e. the realization of their functions, especially gear shift, have a big impact on vehicle operation quality through their effects on the performance of vehicles and their comfort. This paper shows a method of modeling the transition process during gear shifting in planetary gear trains. The simulation model is developed with in order to provide virtual research of planetary gear trains, which would positively decrease the number of real prototypes, thus considerably saving time and contributing to the quality improvement of the final product (planetary gear train and vehicles in general. Introduction Modeling of gear shift processes has been carried out on the planetary gear type Ravigneaux used in planetary gear trains of motor vehicles. The model was developed modularly, so that more simulation models can be added to the whole. At the same time each subsystem is a model for itself and can be used independently from the main model. Simplified engine model Bearing in mind that, for the simulation of the planetary gear which is the subject of this paper, the necessary input parameters are in the form of engine torque Mm, angular velocity and motor ωm moment of inertia of rotating engine components reduced to the input shaft gear, a simplified model of an internal combustion engine has been formed. Model of external load External load resistance is in the form of the torque Mt occurring on the drive wheel of the vehicle. On the other hand, this load is defined by the moment of inertia of rotating elements from the planetary gear to the drive wheel, reduced to the output shaft. Model of friction transmission simulation Transmission power control in planetary gears is achieved through friction components. The output size of this subsystem is the moment of carrying the friction assembly. Simulation model of the planetary gear train The model simulation of the planetary gear type Ravigneaux was formed in accordance with the kinematic

  8. An Evaluation of High-Resolution Regional Climate Model Simulated Snow Cover Using Satellite Data (With Implications for the Simulated Snow-Albedo Feedback)

    Science.gov (United States)

    Minder, J. R.; Letcher, T.

    2015-12-01

    Snow cover often exhibits large spatial variability over mountainous regions where variations in elevation, aspect, vegetation, winds, and orographic precipitation all modulate snow cover. Under climate change, reductions in mountain snow cover are likely to substantially amplify regional warming via the snow-albedo feedback. To capture this important feedback it is crucial that regional climate models (RCMs) adequately simulate spatial and temporal variations in snow cover. Snow cover simulated by high-resolution RCMs over the central Rocky Mountains of the United States is evaluated. RCM simulations were conducted using the Weather Research and Forecasting (WRF) model on a 4 km horizontal grid forced by reanalysis boundary conditions over a seven-year time period. A pair of simulations is considered that differ in the domain size (regional vs. continental) and the land surface model (Noah vs. Noah-MP) employed. RCM output is compared with high-resolution gridded satellite analyses of surface albedo and fractional snow cover derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). Results reveal that both RCMs are generally successful at reproducing the observed seasonal cycle and interannual variability of snow extent over the high terrain of the Rockies. However, in simulations using the Noah land surface model (LSM), sub-grid scale fractional snow covered area of grid cells containing snow is systematically too high compared to observations, often exceeding observations by more than 0.2. This bias in fractional snow cover leads to a substantial positive bias in regional surface albedo. Simulations using the Noah-MP LSM produce more realistic variations in fractional snow cover and surface albedo, likely due to its more-realistic treatment of canopy effects. We quantify how differences in simulated snow cover affect the strength of the snow-albedo feedback under climate change. Both RCMs were used to conduct representative 7-year simulations of a

  9. Linear and nonlinear aspects of snow albedo feedbacks in atmospheric models

    Science.gov (United States)

    Roads, J. O.

    1981-01-01

    Namias' hypothesis, that anomalous snowcover on the eastern side of the North American continent can generate an anomalous east coast low pressure system and an anomalous inland high pressure system, is consistent with the time-averaged anomalous response from a nonlinear, primitive equation channel model with an idealized, flat land-sea arrangement. An attempt to understand and describe this anomalous response in the nonlinear model as a linear response to anomalous diabatic heating was largely unsuccessful, primarily because the anomalous eddy fluxes were also important. This unsuccessful attempt to describe the nonlinear model's time averages by linear theory then motivated several comparisons between linear and nonlinear severely truncated quasi-geostrophic models. It was also found in these models that the eddy fluxes were extremely important for forcing or dissipating the stationary eddies.

  10. Improving snow albedo processes in WRF/SSiB regional climate model to assess impact of dust and black carbon in snow on surface energy balance and hydrology over western U.S.

    OpenAIRE

    Oaida, CM; Xue, Y; Flanner, MG; Skiles, SMK; De Sales, F; Painter, TH

    2015-01-01

    © 2015. American Geophysical Union. All Rights Reserved. Two important factors that control snow albedo are snow grain growth and presence of light-absorbing impurities (aerosols) in snow. However, current regional climate models do not include such processes in a physically based manner in their land surface models. We improve snow albedo calculations in the Simplified Simple Biosphere (SSiB) land surface model coupled with the Weather Research and Forecasting (WRF) regional climate model (R...

  11. Planetary Magnetism

    Science.gov (United States)

    Connerney, J. E. P.

    2007-01-01

    The chapter on Planetary Magnetism by Connerney describes the magnetic fields of the planets, from Mercury to Neptune, including the large satellites (Moon, Ganymede) that have or once had active dynamos. The chapter describes the spacecraft missions and observations that, along with select remote observations, form the basis of our knowledge of planetary magnetic fields. Connerney describes the methods of analysis used to characterize planetary magnetic fields, and the models used to represent the main field (due to dynamo action in the planet's interior) and/or remnant magnetic fields locked in the planet's crust, where appropriate. These observations provide valuable insights into dynamo generation of magnetic fields, the structure and composition of planetary interiors, and the evolution of planets.

  12. Regular network model for the sea ice-albedo feedback in the Arctic.

    Science.gov (United States)

    Müller-Stoffels, Marc; Wackerbauer, Renate

    2011-03-01

    The Arctic Ocean and sea ice form a feedback system that plays an important role in the global climate. The complexity of highly parameterized global circulation (climate) models makes it very difficult to assess feedback processes in climate without the concurrent use of simple models where the physics is understood. We introduce a two-dimensional energy-based regular network model to investigate feedback processes in an Arctic ice-ocean layer. The model includes the nonlinear aspect of the ice-water phase transition, a nonlinear diffusive energy transport within a heterogeneous ice-ocean lattice, and spatiotemporal atmospheric and oceanic forcing at the surfaces. First results for a horizontally homogeneous ice-ocean layer show bistability and related hysteresis between perennial ice and perennial open water for varying atmospheric heat influx. Seasonal ice cover exists as a transient phenomenon. We also find that ocean heat fluxes are more efficient than atmospheric heat fluxes to melt Arctic sea ice.

  13. Can uncertainties in sea ice albedo reconcile patterns of data-model discord for the Pliocene and 20th/21st centuries?

    Science.gov (United States)

    Howell, Fergus W.; Haywood, Alan M.; Dolan, Aisling M.; Dowsett, Harry J.; Francis, Jane E; Hill, Daniel J.; Pickering, Steven J.; Pope, James O.; Salzmann, Ulrich; Wade, Bidget S

    2014-01-01

    General Circulation Model simulations of the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Myr ago) currently underestimate the level of warming that proxy data suggest existed at high latitudes, with discrepancies of up to 11°C for sea surface temperature estimates and 17°C for surface air temperature estimates. Sea ice has a strong influence on high-latitude climates, partly due to the albedo feedback. We present results demonstrating the effects of reductions in minimum sea ice albedo limits in general circulation model simulations of the mPWP. While mean annual surface air temperature increases of up to 6°C are observed in the Arctic, the maximum decrease in model-data discrepancies is just 0.81°C. Mean annual sea surface temperatures increase by up to 2°C, with a maximum model-data discrepancy improvement of 1.31°C. It is also suggested that the simulation of observed 21st century sea ice decline could be influenced by the adjustment of the sea ice albedo parameterization.

  14. Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback

    Energy Technology Data Exchange (ETDEWEB)

    Rose, Brian E. J. [Department of Atmospheric and Environmental Sciences, University at Albany (State University of New York), 1400 Washington Avenue, Albany, NY 12222 (United States); Cronin, Timothy W. [Program in Atmospheres, Oceans, and Climate, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bitz, Cecilia M., E-mail: brose@albany.edu [Department of Atmospheric Sciences, MS 351640, University of Washington, Seattle, WA 98195-1640 (United States)

    2017-09-01

    Planetary obliquity determines the meridional distribution of the annual mean insolation. For obliquity exceeding 55°, the weakest insolation occurs at the equator. Stable partial snow and ice cover on such a planet would be in the form of a belt about the equator rather than polar caps. An analytical model of planetary climate is used to investigate the stability of ice caps and ice belts over the widest possible range of parameters. The model is a non-dimensional diffusive Energy Balance Model, representing insolation, heat transport, and ice−albedo feedback on a spherical planet. A complete analytical solution for any obliquity is given and validated against numerical solutions of a seasonal model in the “deep-water” regime of weak seasonal ice line migration. Multiple equilibria and unstable transitions between climate states (ice-free, Snowball, or ice cap/belt) are found over wide swaths of parameter space, including a “Large Ice-Belt Instability” and “Small Ice-Belt Instability” at high obliquity. The Snowball catastrophe is avoided at weak radiative forcing in two different scenarios: weak albedo feedback and inefficient heat transport (favoring stable partial ice cover), or efficient transport at high obliquity (favoring ice-free conditions). From speculative assumptions about distributions of planetary parameters, three-fourths to four-fifths of all planets with stable partial ice cover should be in the form of Earth-like polar caps.

  15. Ice Caps and Ice Belts: The Effects of Obliquity on Ice-Albedo Feedback

    Science.gov (United States)

    Rose, Brian E. J.; Cronin, Timothy W.; Bitz, Cecilia M.

    2017-09-01

    Planetary obliquity determines the meridional distribution of the annual mean insolation. For obliquity exceeding 55°, the weakest insolation occurs at the equator. Stable partial snow and ice cover on such a planet would be in the form of a belt about the equator rather than polar caps. An analytical model of planetary climate is used to investigate the stability of ice caps and ice belts over the widest possible range of parameters. The model is a non-dimensional diffusive Energy Balance Model, representing insolation, heat transport, and ice-albedo feedback on a spherical planet. A complete analytical solution for any obliquity is given and validated against numerical solutions of a seasonal model in the “deep-water” regime of weak seasonal ice line migration. Multiple equilibria and unstable transitions between climate states (ice-free, Snowball, or ice cap/belt) are found over wide swaths of parameter space, including a “Large Ice-Belt Instability” and “Small Ice-Belt Instability” at high obliquity. The Snowball catastrophe is avoided at weak radiative forcing in two different scenarios: weak albedo feedback and inefficient heat transport (favoring stable partial ice cover), or efficient transport at high obliquity (favoring ice-free conditions). From speculative assumptions about distributions of planetary parameters, three-fourths to four-fifths of all planets with stable partial ice cover should be in the form of Earth-like polar caps.

  16. The Effect of Bond Albedo on Venus' Atmospheric and Surface Temperatures

    Science.gov (United States)

    Bullock, M. A.; Limaye, S. S.; Grinspoon, D. H.; Way, M.

    2017-12-01

    In spite of Venus' high planetary albedo, sufficient solar energy reaches the surface to drive a powerful greenhouse effect. The surface temperature is three times higher than it would be without an atmosphere. However, the details of the energy balance within Venus' atmosphere are poorly understood. Half of the solar energy absorbed within the clouds, where most of the solar energy is absorbed, is due to an unknown agent. One of the challenges of modeling Venus' atmosphere has been to account for all the sources of opacity sufficient to generate a globally averaged surface temperature of 735 K, when only 2% of the incoming solar energy is deposited at the surface. The wavelength and spherically integrated albedo, or Bond albedo, has typically been cited as between 0.7 and 0.82 (Colin 1983). Yet, recent photometry of Venus at extended phase angles between 2 and 179° indicate a Bond albedo of 0.90 (Mallama et al., 2006). The authors note an increase in cloud top brightness at phase angles right). Venus surface temperature as Bond Albedo changes. Radiative-convective equilibrium models predict the correct globally averaged surface temperature at a=0.81. Calculations here show that a Bond albedo of a=0.9 would yield a surface temperature of 666.4 K, about 70 K too low, unless there is additional thermal absorption within the atmosphere that is not understood. Colin, L.,, Venus, University of Arizona Press, Tucson, 1983, pp 10-26. Mallama, A., et al., 2006. Icarus. 182, 10-22.

  17. Comparison and Implementation of a Rigid and a Flexible Multibody Planetary Gearbox Model

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    2014-01-01

    We propose algorithms for developing (1) a rigid (constrained) and (2) a flexible planetary gearbox model. The two methods are compared against each other and advantages/disadvantages of each method are discussed. The rigid model (1) has gear tooth reaction forces expressed by Lagrange multipliers...

  18. Cold aqueous planetary geochemistry with FREZCHEM from modeling to the search for life at the limits

    CERN Document Server

    Marion, Giles M

    2007-01-01

    This book explicitly investigates issues of astrobiological relevance in the context of cold aqueous planetary geochemistry. At the core of the technical chapters is the FREZCHEM model, initially developed over many years by one of the authors to quantify aqueous electrolyte properties and chemical thermodynamics at subzero temperatures. FREZCHEM, of general relevance to biogeochemists and geochemical modelers, cold planetary scientists, physicochemists and chemical engineers, is subsequently applied to the exploration of biogeochemical applications to solar systems bodies in general, and to speculations about the limits for life in cold environments in particular.

  19. Enabling interoperability in planetary sciences and heliophysics: The case for an information model

    Science.gov (United States)

    Hughes, J. Steven; Crichton, Daniel J.; Raugh, Anne C.; Cecconi, Baptiste; Guinness, Edward A.; Isbell, Christopher E.; Mafi, Joseph N.; Gordon, Mitchell K.; Hardman, Sean H.; Joyner, Ronald S.

    2018-01-01

    The Planetary Data System has developed the PDS4 Information Model to enable interoperability across diverse science disciplines. The Information Model is based on an integration of International Organization for Standardization (ISO) level standards for trusted digital archives, information model development, and metadata registries. Where controlled vocabularies provides a basic level of interoperability by providing a common set of terms for communication between both machines and humans the Information Model improves interoperability by means of an ontology that provides semantic information or additional related context for the terms. The information model was defined by team of computer scientists and science experts from each of the diverse disciplines in the Planetary Science community, including Atmospheres, Geosciences, Cartography and Imaging Sciences, Navigational and Ancillary Information, Planetary Plasma Interactions, Ring-Moon Systems, and Small Bodies. The model was designed to be extensible beyond the Planetary Science community, for example there are overlaps between certain PDS disciplines and the Heliophysics and Astrophysics disciplines. "Interoperability" can apply to many aspects of both the developer and the end-user experience, for example agency-to-agency, semantic level, and application level interoperability. We define these types of interoperability and focus on semantic level interoperability, the type of interoperability most directly enabled by an information model.

  20. Reflectance model for densely packed media: Estimates of the surface properties of the high-albedo satellites of Saturn

    Science.gov (United States)

    Tishkovets, V. P.; Petrova, E. V.

    2017-07-01

    Interpretation of photometric and polarimetric observations of atmosphereless celestial bodies faces the problems connected with both the insufficient accuracy and level of details in groundbased observations and the current state of the theory of the multiple scattering of light. In application to sparse media, where the electromagnetic waves, propagating between the scatterers, can be considered as spherical (the socalled far-field approximation), this theory is rather well developed for both the diffuse and coherent components of the scattered radiation. In this paper, we show that this theory can be also successfully applied to the measurements of polarization of light scattered by densely packed, though nonabsorbing or weakly absorbing, media. For this purpose, we calculated the models for a semi-infinite layer of the medium composed of randomly oriented clusters of spherical particles and compared them with the data of laboratory and astronomical measurements. The potential of the present approach is illustrated by an example of the interpretation of the polarization measurements of the ice satellites of Saturn—Rhea and Enceladus—which allowed some properties of the surface of these celestial bodies to be estimated. In particular, the ratio of the surface area that makes no contribution to the negative polarization of light reflected at small phase angles to the area producing the negative polarization branch was found. Under the assumption of the same albedo of these areas, this ratio turned out to be 3.31-3.66 and 1.7-3.8 for Rhea and Enceladus, respectively. For Enceladus, it is difficult to obtain a sufficiently narrow range of the estimated parameters, since the number of measurement points in the phase dependence of polarization of this satellite is small. For the surface of Rhea, the estimated packing density of particles, participating in the opposition effects, is approximately 15%, while their smallest size is of the order of the wavelength of

  1. Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone.

    Science.gov (United States)

    Joshi, Manoj M; Haberle, Robert M

    2012-01-01

    M stars comprise 80% of main sequence stars, so their planetary systems provide the best chance for finding habitable planets, that is, those with surface liquid water. We have modeled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M stars), using spectrally resolved data of Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 μm, combined with M stars emitting a significant fraction of their radiation at these same longer wavelengths, means that the albedos of ice and snow on planets orbiting M stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M stars may be 10-30% farther away from the parent star than previously thought.

  2. Towards Camera-LIDAR Fusion-Based Terrain Modelling for Planetary Surfaces: Review and Analysis.

    Science.gov (United States)

    Shaukat, Affan; Blacker, Peter C; Spiteri, Conrad; Gao, Yang

    2016-11-20

    In recent decades, terrain modelling and reconstruction techniques have increased research interest in precise short and long distance autonomous navigation, localisation and mapping within field robotics. One of the most challenging applications is in relation to autonomous planetary exploration using mobile robots. Rovers deployed to explore extraterrestrial surfaces are required to perceive and model the environment with little or no intervention from the ground station. Up to date, stereopsis represents the state-of-the art method and can achieve short-distance planetary surface modelling. However, future space missions will require scene reconstruction at greater distance, fidelity and feature complexity, potentially using other sensors like Light Detection And Ranging (LIDAR). LIDAR has been extensively exploited for target detection, identification, and depth estimation in terrestrial robotics, but is still under development to become a viable technology for space robotics. This paper will first review current methods for scene reconstruction and terrain modelling using cameras in planetary robotics and LIDARs in terrestrial robotics; then we will propose camera-LIDAR fusion as a feasible technique to overcome the limitations of either of these individual sensors for planetary exploration. A comprehensive analysis will be presented to demonstrate the advantages of camera-LIDAR fusion in terms of range, fidelity, accuracy and computation.

  3. Towards Camera-LIDAR Fusion-Based Terrain Modelling for Planetary Surfaces: Review and Analysis

    Directory of Open Access Journals (Sweden)

    Affan Shaukat

    2016-11-01

    Full Text Available In recent decades, terrain modelling and reconstruction techniques have increased research interest in precise short and long distance autonomous navigation, localisation and mapping within field robotics. One of the most challenging applications is in relation to autonomous planetary exploration using mobile robots. Rovers deployed to explore extraterrestrial surfaces are required to perceive and model the environment with little or no intervention from the ground station. Up to date, stereopsis represents the state-of-the art method and can achieve short-distance planetary surface modelling. However, future space missions will require scene reconstruction at greater distance, fidelity and feature complexity, potentially using other sensors like Light Detection And Ranging (LIDAR. LIDAR has been extensively exploited for target detection, identification, and depth estimation in terrestrial robotics, but is still under development to become a viable technology for space robotics. This paper will first review current methods for scene reconstruction and terrain modelling using cameras in planetary robotics and LIDARs in terrestrial robotics; then we will propose camera-LIDAR fusion as a feasible technique to overcome the limitations of either of these individual sensors for planetary exploration. A comprehensive analysis will be presented to demonstrate the advantages of camera-LIDAR fusion in terms of range, fidelity, accuracy and computation.

  4. Numerical model of a non-steady atmospheric planetary boundary layer, based on similarity theory

    DEFF Research Database (Denmark)

    Zilitinkevich, S.S.; Fedorovich, E.E.; Shabalova, M.V.

    1992-01-01

    A numerical model of a non-stationary atmospheric planetary boundary layer (PBL) over a horizontally homogeneous flat surface is derived on the basis of similarity theory. The two most typical turbulence regimes are reproduced: one corresponding to a convectively growing PBL and another correspon...

  5. On the Nature, Theory, and Modeling of Atmospheric Planetary Boundary Layers

    DEFF Research Database (Denmark)

    Baklanov, Alexander A.; Grisogono, Branko; Bornstein, Robert

    2011-01-01

    The gap between our modern understanding of planetary boundary layer physics and its decades-old representations in current operational atmospheric models is widening, which has stimulated this review of the current state of the art and an analysis of the immediate needs in boundary layer theory,...

  6. Characterization and Modeling of Materials Responsible for Planetary Crustal Magnetism

    Science.gov (United States)

    Strauss, Becky E.

    Earth and Mercury are the only terrestrial planets in our solar system with present-day magnetic dipole fields generated by internal dynamo systems. In contrast, Mars and the Moon show evidence of past dipole fields in the form of crustal magnetic anomalies; to hold measurable magnetizations, crustal materials must have been exposed to an applied field. While the physical principles of magnetic recording are consistent between terrestrial planets, the particular conditions at each planet control the mechanisms by which crustal materials may be magnetized and limit the types of minerals that can retain magnetic remanence. As the suite of magnetic materials used for studies of remanence expands, the need for new methods follows. The integration of rock magnetic techniques with microscopy and chemical analyses enables the reconstruction of increasingly comprehensive narratives of remanence acquisition and alteration, even in materials that are challenging to study using traditional methods. This thesis demonstrates the utility of a materials approach to rock magnetism by applying techniques designed for terrestrial use in a planetary context. The first of two case studies focuses on calcite cave deposits as a means to demonstrate how novel techniques can be used to unlock previously inaccessible archives of magnetic information. Tandem magnetic and microscopic analyses improve our understanding of the rock magnetic properties of weakly magnetic stalagmites and their potential for paleomagnetic research, as well as illuminating the pathways of remanence acquisition in cave systems. The second case study addresses the magnetic anomalies recently detected by the MESSENGER orbiter at Mercury. These anomalies are consistent with remanence acquired in a dipole field. However, in the absence of physical samples, the types of magnetic minerals that could be holding remanence in Mercury's hot, highly reducing surface environment have not yet been determined. Orbital data is

  7. Albedo matters: Understanding runaway albedo variations on Pluto

    Science.gov (United States)

    Earle, Alissa M.; Binzel, Richard P.; Young, Leslie A.; Stern, S. A.; Ennico, K.; Grundy, W.; Olkin, C. B.; Weaver, H. A.; New Horizons Surface Composition Theme

    2018-03-01

    The data returned from NASA's New Horizons reconnaissance of the Pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries. Pluto has a high obliquity (currently 119°) that varies by 23° over a period of less than 3 million years. This variation, combined with its regressing longitude of perihelion (360° over 3.7 million years), creates epochs of "Super Seasons" where one pole is pointed at the Sun at perihelion, thereby experiencing a short, relatively warm summer followed by its longest possible period of winter darkness. In contrast, the other pole experiences a much longer, less intense summer and a short winter season. We use a simple volatile sublimation and deposition model to explore the relationship between albedo variations, latitude, and volatile sublimation and deposition for the current epoch as well as historical epochs during which Pluto experienced these "Super Seasons." Our investigation quantitatively shows that Pluto's geometry creates the potential for runaway albedo and volatile variations, particularly in the equatorial region, which can sustain stark longitudinal contrasts like the ones we see between Tombaugh Regio and the informally named Cthulhu Regio.

  8. Approximating Matsubara dynamics using the planetary model: Tests on liquid water and ice

    Science.gov (United States)

    Willatt, Michael J.; Ceriotti, Michele; Althorpe, Stuart C.

    2018-03-01

    Matsubara dynamics is the quantum-Boltzmann-conserving classical dynamics which remains when real-time coherences are taken out of the exact quantum Liouvillian [T. J. H. Hele et al., J. Chem. Phys. 142, 134103 (2015)]; because of a phase-term, it cannot be used as a practical method without further approximation. Recently, Smith et al. [J. Chem. Phys. 142, 244112 (2015)] developed a "planetary" model dynamics which conserves the Feynman-Kleinert (FK) approximation to the quantum-Boltzmann distribution. Here, we show that for moderately anharmonic potentials, the planetary dynamics gives a good approximation to Matsubara trajectories on the FK potential surface by decoupling the centroid trajectory from the locally harmonic Matsubara fluctuations, which reduce to a single phase-less fluctuation particle (the "planet"). We also show that the FK effective frequency can be approximated by a direct integral over these fluctuations, obviating the need to solve iterative equations. This modification, together with use of thermostatted ring-polymer molecular dynamics, allows us to test the planetary model on water (gas-phase, liquid, and ice) using the q-TIP4P/F potential surface. The "planetary" fluctuations give a poor approximation to the rotational/librational bands in the infrared spectrum, but a good approximation to the bend and stretch bands, where the fluctuation lineshape is found to be motionally narrowed by the vibrations of the centroid.

  9. Tackling regional climate change by leaf albedo bio-geoengineering.

    Science.gov (United States)

    Ridgwell, Andy; Singarayer, Joy S; Hetherington, Alistair M; Valdes, Paul J

    2009-01-27

    The likelihood that continuing greenhouse-gas emissions will lead to an unmanageable degree of climate change has stimulated the search for planetary-scale technological solutions for reducing global warming ("geoengineering"), typically characterized by the necessity for costly new infrastructures and industries. We suggest that the existing global infrastructure associated with arable agriculture can help, given that crop plants exert an important influence over the climatic energy budget because of differences in their albedo (solar reflectivity) compared to soils and to natural vegetation. Specifically, we propose a "bio-geoengineering" approach to mitigate surface warming, in which crop varieties having specific leaf glossiness and/or canopy morphological traits are specifically chosen to maximize solar reflectivity. We quantify this by modifying the canopy albedo of vegetation in prescribed cropland areas in a global-climate model, and thereby estimate the near-term potential for bio-geoengineering to be a summertime cooling of more than 1 degrees C throughout much of central North America and midlatitude Eurasia, equivalent to seasonally offsetting approximately one-fifth of regional warming due to doubling of atmospheric CO(2). Ultimately, genetic modification of plant leaf waxes or canopy structure could achieve greater temperature reductions, although better characterization of existing intraspecies variability is needed first.

  10. Improvement of a snow albedo parameterization in the Snow-Atmosphere-Soil Transfer model: evaluation of impacts of aerosol on seasonal snow cover

    Science.gov (United States)

    Zhong, Efang; Li, Qian; Sun, Shufen; Chen, Wen; Chen, Shangfeng; Nath, Debashis

    2017-11-01

    The presence of light-absorbing aerosols (LAA) in snow profoundly influence the surface energy balance and water budget. However, most snow-process schemes in land-surface and climate models currently do not take this into consideration. To better represent the snow process and to evaluate the impacts of LAA on snow, this study presents an improved snow albedo parameterization in the Snow-Atmosphere-Soil Transfer (SAST) model, which includes the impacts of LAA on snow. Specifically, the Snow, Ice and Aerosol Radiation (SNICAR) model is incorporated into the SAST model with an LAA mass stratigraphy scheme. The new coupled model is validated against in-situ measurements at the Swamp Angel Study Plot (SASP), Colorado, USA. Results show that the snow albedo and snow depth are better reproduced than those in the original SAST, particularly during the period of snow ablation. Furthermore, the impacts of LAA on snow are estimated in the coupled model through case comparisons of the snowpack, with or without LAA. The LAA particles directly absorb extra solar radiation, which accelerates the growth rate of the snow grain size. Meanwhile, these larger snow particles favor more radiative absorption. The average total radiative forcing of the LAA at the SASP is 47.5 W m-2. This extra radiative absorption enhances the snowmelt rate. As a result, the peak runoff time and "snow all gone" day have shifted 18 and 19.5 days earlier, respectively, which could further impose substantial impacts on the hydrologic cycle and atmospheric processes.

  11. Spacecraft Attitude Determination with Earth Albedo Corrected Sun Sensor Measurements

    DEFF Research Database (Denmark)

    Bhanderi, Dan

    This thesis focuses on advanced modeling of the Earth albedo experienced by satellites in Earth orbit. The model of the Earth albedo maintains directional information of the Earth albedo irradiance from each partition on the Earth surface. This allows enhanced modeling of Sun sensor current outputs......-Method, Extended Kalman Filter, and Unscented Kalman Filter algorithms are presented and the results are compared. Combining the Unscented Kalman Filter with Earth albedo and enhanced Sun sensor modeling allows for three-axis attitude determination from Sun sensor only, which previously has been perceived...

  12. EUROPLANET-RI modelling service for the planetary science community: European Modelling and Data Analysis Facility (EMDAF)

    Science.gov (United States)

    Khodachenko, Maxim; Miller, Steven; Stoeckler, Robert; Topf, Florian

    2010-05-01

    Computational modeling and observational data analysis are two major aspects of the modern scientific research. Both appear nowadays under extensive development and application. Many of the scientific goals of planetary space missions require robust models of planetary objects and environments as well as efficient data analysis algorithms, to predict conditions for mission planning and to interpret the experimental data. Europe has great strength in these areas, but it is insufficiently coordinated; individual groups, models, techniques and algorithms need to be coupled and integrated. Existing level of scientific cooperation and the technical capabilities for operative communication, allow considerable progress in the development of a distributed international Research Infrastructure (RI) which is based on the existing in Europe computational modelling and data analysis centers, providing the scientific community with dedicated services in the fields of their computational and data analysis expertise. These services will appear as a product of the collaborative communication and joint research efforts of the numerical and data analysis experts together with planetary scientists. The major goal of the EUROPLANET-RI / EMDAF is to make computational models and data analysis algorithms associated with particular national RIs and teams, as well as their outputs, more readily available to their potential user community and more tailored to scientific user requirements, without compromising front-line specialized research on model and data analysis algorithms development and software implementation. This objective will be met through four keys subdivisions/tasks of EMAF: 1) an Interactive Catalogue of Planetary Models; 2) a Distributed Planetary Modelling Laboratory; 3) a Distributed Data Analysis Laboratory, and 4) enabling Models and Routines for High Performance Computing Grids. Using the advantages of the coordinated operation and efficient communication between the

  13. Design of Mobility System for Ground Model of Planetary Exploration Rover

    Directory of Open Access Journals (Sweden)

    Younkyu Kim

    2012-12-01

    Full Text Available In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL, followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.

  14. A dynamic model to predict modulation sidebands of a planetary gear set having manufacturing errors

    Science.gov (United States)

    Inalpolat, Murat; Kahraman, Ahmet

    2010-02-01

    In this study, a nonlinear time-varying dynamic model is proposed to predict modulation sidebands of planetary gear sets. This discrete dynamic model includes periodically time-varying gear mesh stiffnesses and the nonlinearities associated with tooth separations. The model uses forms of gear mesh interface excitations that are amplitude and frequency modulated due to a class of gear manufacturing errors to predict dynamic forces at all sun-planet and ring-planet gear meshes. The predicted gear mesh force spectra are shown to exhibit well-defined modulation sidebands at frequencies associated with the rotational speeds of gears relative to the planet carrier. This model is further combined with a previously developed model that accounts for amplitude modulations due to rotation of the carrier to predict acceleration spectra at a fixed position in the planetary transmission housing. Individual contributions of each gear error in the form of amplitude and frequency modulations are illustrated through an example analysis. Comparisons are made to measured spectra to demonstrate the capability of the model in predicting the sidebands of a planetary gear set with gear manufacturing errors and a rotating carrier.

  15. Large-scale simulations of snow albedo masking by forests

    OpenAIRE

    Essery, Richard

    2013-01-01

    Comparisons between climate models have found large differences in predictions for the albedo of forested regions with snow cover, leading to uncertainty in the strength of snow albedo feedbacks on climate change predicted by these models. To explore this uncertainty, three commonly used methods for calculating the albedo of vegetated surfaces are compared, taking observed snow and vegetation distributions as inputs. Surprisingly, all three methods produce similar results and compare reasonab...

  16. Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

    Science.gov (United States)

    Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

    2010-01-01

    As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

  17. Towards a realistic simulation of boreal summer tropical rainfall climatology in state-of-the-art coupled models: role of the background snow-free land albedo

    Science.gov (United States)

    Terray, P.; Sooraj, K. P.; Masson, S.; Krishna, R. P. M.; Samson, G.; Prajeesh, A. G.

    2017-07-01

    State-of-the-art global coupled models used in seasonal prediction systems and climate projections still have important deficiencies in representing the boreal summer tropical rainfall climatology. These errors include prominently a severe dry bias over all the Northern Hemisphere monsoon regions, excessive rainfall over the ocean and an unrealistic double inter-tropical convergence zone (ITCZ) structure in the tropical Pacific. While these systematic errors can be partly reduced by increasing the horizontal atmospheric resolution of the models, they also illustrate our incomplete understanding of the key mechanisms controlling the position of the ITCZ during boreal summer. Using a large collection of coupled models and dedicated coupled experiments, we show that these tropical rainfall errors are partly associated with insufficient surface thermal forcing and incorrect representation of the surface albedo over the Northern Hemisphere continents. Improving the parameterization of the land albedo in two global coupled models leads to a large reduction of these systematic errors and further demonstrates that the Northern Hemisphere subtropical deserts play a seminal role in these improvements through a heat low mechanism.

  18. Incorporation of the Mass Concentration and the New Snow Albedo Schemes into the Global Forecasting Model, GEOS-5 and the Impact of the New Schemes over Himalayan Glaciers

    Science.gov (United States)

    Yasunari, Teppei

    2012-01-01

    Recently the issue on glacier retreats comes up and many factors should be relevant to the issue. The absorbing aerosols such as dust and black carbon (BC) are considered to be one of the factors. After they deposited onto the snow surface, it will reduce snow albedo (called snow darkening effect) and probably contribute to further melting of glacier. The Goddard Earth Observing System version 5 (GEOS-5) has developed at NASA/GSFC. However, the original snowpack model used in the land surface model in the GEOS-5 did not consider the snow darkening effect. Here we developed the new snow albedo scheme which can consider the snow darkening effect. In addition, another scheme on calculating mass concentrations on the absorbing aerosols in snowpack was also developed, in which the direct aerosol depositions from the chemical transport model in the GEOS-5 were used. The scheme has been validated with the observed data obtained at backyard of the Institute of Low Temperature Science, Hokkaido University, by Dr. Teruo Aoki (Meteorological Research Institute) et aL including me. The observed data was obtained when I was Ph.D. candidate. The original GEOS-5during 2007-2009 over the Himalayas and Tibetan Plateau region showed more reductions of snow than that of the new GEOS-5 because the original one used lower albedo settings. On snow cover fraction, the new GEOS-5 simulated more realistic snow-covered area comparing to the MODIS snow cover fraction. The reductions on snow albedo, snow cover fraction, and snow water equivalent were seen with statistically significance if we consider the snow darkening effect comparing to the results without the snow darkening effect. In the real world, debris cover, inside refreezing process, surface flow of glacier, etc. affect glacier mass balance and the simulated results immediately do not affect whole glacier retreating. However, our results indicate that some surface melting over non debris covered parts of the glacier would be

  19. A secular model for efficient exploration of mutually-inclined planetary systems

    Science.gov (United States)

    Deitrick, Russell; Barnes, Rory

    2015-01-01

    Dynamical studies of exoplanets largely assume coplanarity because of the lack of inclination information in many cases. However, the multiplanet system Upsilon Andromedae has orbital planes inclined by 30 degrees, models of planet-planet scattering predict large mutual inclinations, and astrometry missions such as Gaia have the power to reveal the 3 dimensional architecture of planetary systems. As the dynamics of systems with non-planar orbits will be key to understanding origins, and ultimately habitability where applicable, we present a computationally efficient model for the orbital evolution of planetary systems with modest inclinations and eccentricities which are not in a mean motion resonance. Specifically, our model is based on the disturbing function and extends to 4th order in eccentricity and inclination. We present comparisons to N-body models for known systems, such as the Solar System and Upsilon Andromedae, and hypothetical systems with a range of orbital configurations. We describe the eccentricity and inclination conditions under which the model is valid. We further calculate the rotational evolution of planets based on the orbital evolution and the stellar torque and find a wide range of obliquity evolution is possible. As obliquity is a key driver of planetary climate, Earth-like planets in non-planar systems may have climates dominated by their orbital evolution.

  20. Considering Planetary Constraints and Dynamic Screening in Solar Evolution Modeling

    Science.gov (United States)

    Wood, Suzannah R.; Mussack, Katie; Guzik, Joyce A.

    2018-01-01

    The ‘faint early sun problem’ remains unsolved. This problem consists of the apparent contradiction between the standard solar model prediction of lower luminosity (70% of current luminosity) and the observations of liquid water on early Earth and Mars. The presence of liquid water on early Earth and Mars should not be neglected and should be used as a constraint for solar evolution modeling. In addition, modifications to standard solar models are needed to address the discrepancy with solar structure inferred from helioseismology given the latest solar abundance determinations. Here, we will utilize the three different solar abundances: GN93 (Grevesse & Noels, 1993), AGS05 (Asplund et al., 2005), AGSS09 (Asplund et al., 2009). Here, we propose an early mass loss model with an initial solar mass between 1.07 and 1.15 solar masses and an exponentially decreasing mass-loss rate to meet conditions in the early solar system (Wood et al, submitted). Additionally, we investigate the effects of dynamic screening and the new OPLIB opacities from Los Alamos (Colgan et al., 2016). We show the effects of these modifications to the standard solar evolution models on the interior structure, neutrino fluxes, sound speed, p-mode frequencies, convection zone depth, and envelope helium and element abundance of the model sun at the present day.

  1. ESA' s novel gravitational modeling of irregular planetary bodies

    Science.gov (United States)

    Ortega, Guillermo

    A detailed understanding and modeling of the gravitational modeling is required for realistic investigation of the dynamics of orbits close to irregularly shaped bodies. Gravity field modelling up to a certain maximum spherical harmonic degree N involves N2 unkown spherical harmonic coefficients or complex harmonics. The corresponding number of matrix entries reaches till N4 . For missions like CHAMP, GRACE or GOCE, the maximum degree of resolution is 75, 150 and 300 respectively. Therefore, the number of unknowns for a satellite like GOCE will be around 100.000. Since these missions usually fly for a period of time of several years, the number of observations is huge. Hence, gravity field recovery from these missions is a high demanding task. The classical approaches like spherical expansion of the potential lead generally to a high number of coefficients, which reduce the software computational efficiency of the orbit propagation and which have mostly a limited physical meaning. One of the main targets of the activity is the modelling of asteroids, small moons, and cometary bodies. All celestial bodies are irregular by definition. However, the scope of the activity is broad enough as to be able to use the models and the software in quasy-regular bodies as well. Therefore the models and tools could be used for bodies such as the Moon, Mars, Venus, Deimos, Europa, Eros, Mathilda, and Churyumov-Gerasimenko, etc., being these applications relevant for scientific (Rosetta, Bepi Colombo), exploration (Exo-Mars), NEO mitigation (Don Quijote) and Earth observation (GOCE) missions of ESA.

  2. Edge effect modeling of small tool polishing in planetary movement

    Science.gov (United States)

    Li, Qi-xin; Ma, Zhen; Jiang, Bo; Yao, Yong-sheng

    2018-03-01

    As one of the most challenging problems in Computer Controlled Optical Surfacing (CCOS), the edge effect greatly affects the polishing accuracy and efficiency. CCOS rely on stable tool influence function (TIF), however, at the edge of the mirror surface,with the grinding head out of the mirror ,the contact area and pressure distribution changes, which resulting in a non-linear change of TIF, and leads to tilting or sagging at the edge of the mirror. In order reduce the adverse effects and improve the polishing accuracy and efficiency. In this paper, we used the finite element simulation to analyze the pressure distribution at the mirror edge and combined with the improved traditional method to establish a new model. The new method fully considered the non-uniformity of pressure distribution. After modeling the TIFs in different locations, the description and prediction of the edge effects are realized, which has a positive significance on the control and suppression of edge effects

  3. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters

    Directory of Open Access Journals (Sweden)

    Sílvia N. M. Yanagi

    2011-12-01

    Full Text Available This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS and near-infrared (NIR spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (x up and to the reflectivity in the near-infrared spectral band (rNIR,up, a smaller sensitivity to the reflectivity in the visible spectral band (rVIS,up and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are Xup = 0.86, rVIS,up = 0.062 and rNIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.Este estudo avalia a sensibilidade do albedo da superfície pelo Simulador Integrado da Biosfera (IBIS a um conjunto de parâmetros que representam algumas propriedades arquitetônicas e óticas do dossel da floresta tropical Amazônica. Os parâmetros testados neste estudo são a orientação e refletância das folhas do dossel superior e inferior nas bandas espectrais do visível (VIS e infravermelho próximo (NIR. Os resultados são avaliados contra observações feitas no sítio K34 pertencente ao Instituto Nacional de Pesquisas da Amazônia (INPA na Reserva Biológica de Cuieiras. A análise de sensibilidade indica uma forte resposta aos parâmetros de orienta

  4. A Continental United States High Resolution NLCD Land Cover – MODIS Albedo Database to Examine Albedo and Land Cover Change Relationships

    Science.gov (United States)

    Surface albedo influences climate by affecting the amount of solar radiation that is reflected at the Earth’s surface, and surface albedo is, in turn, affected by land cover. General Circulation Models typically use modeled or prescribed albedo to assess the influence of land co...

  5. Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP

    Directory of Open Access Journals (Sweden)

    Y. H. Lee

    2013-03-01

    Full Text Available As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP, we evaluate the historical black carbon (BC aerosols simulated by 8 ACCMIP models against observations including 12 ice core records, long-term surface mass concentrations, and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using offline models with prescribed meteorology from 1996–2000. We evaluate the vertical profile of BC snow concentrations from these offline simulations using the recent BC snowpack measurements. Despite using the same BC emissions, the global BC burden differs by approximately a factor of 3 among models due to differences in aerosol removal parameterizations and simulated meteorology: 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However, the global BC burden from preindustrial to present-day increases by 2.5–3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions during the same period. We find a large divergence among models at both Northern Hemisphere (NH and Southern Hemisphere (SH high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC surface mass concentrations well in Europe and North America except at Ispra. However, the models fail to predict the Arctic BC seasonality due to severe underestimations during winter and spring. The simulated vertically resolved BC snow concentrations are, on average, within a factor of 2–3 of the BC snowpack measurements except for Greenland and the Arctic Ocean. For the ice core evaluation, models tend to adequately capture both the observed temporal trends and the magnitudes at Greenland sites. However, models fail to predict the decreasing trend of BC depositions/ice core concentrations from the 1950s to the 1970s in most Tibetan Plateau ice cores. The distinct temporal trend at the Tibetan

  6. Evaluation of preindustrial to present-day black carbon and its albedo forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

    Science.gov (United States)

    Lee, Y. H.; Lamarque, J.-F.; Flanner, M. G.; Jiao, C.; Shindell, D. T.; Bernsten, T.; Bisiaux, M. M.; Cao, J.; Collins, W. J.; Curran, M.; hide

    2013-01-01

    As part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), we evaluate the historical black carbon (BC) aerosols simulated by 8 ACCMIP models against observations including 12 ice core records, long-term surface mass concentrations, and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using offline models with prescribed meteorology from 1996-2000. We evaluate the vertical profile of BC snow concentrations from these offline simulations using the recent BC snowpack measurements. Despite using the same BC emissions, the global BC burden differs by approximately a factor of 3 among models due to differences in aerosol removal parameterizations and simulated meteorology: 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However, the global BC burden from preindustrial to present-day increases by 2.5-3 times with little variation among models, roughly matching the 2.5-fold increase in total BC emissions during the same period.We find a large divergence among models at both Northern Hemisphere (NH) and Southern Hemisphere (SH) high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC surface mass concentrations well in Europe and North America except at Ispra. However, the models fail to predict the Arctic BC seasonality due to severe underestimations during winter and spring. The simulated vertically resolved BC snow concentrations are, on average, within a factor of 2-3 of the BC snowpack measurements except for Greenland and the Arctic Ocean. For the ice core evaluation, models tend to adequately capture both the observed temporal trends and the magnitudes at Greenland sites. However, models fail to predict the decreasing trend of BC depositions/ice core concentrations from the 1950s to the 1970s in most Tibetan Plateau ice cores. The distinct temporal trend at the Tibetan Plateau ice cores

  7. Equilibrium Temperatures and Albedos of Habitable Earth-Like Planets in a Coupled Atmosphere-Ocean GCM

    Science.gov (United States)

    Del Genio, Anthony; Way, Michael; Amundsen, David; Sohl, Linda; Fujii, Yuka; Ebihara, Yuka; Kiang, Nancy; Chandler, Mark; Aleinov, Igor; Kelley, Maxwell

    2017-01-01

    The potential habitability of detected exoplanets is typically assessed using the concept of equilibrium temperature (T[subscript] e) based on cloud-free 1-D models with assumed albedo equal to Earth's (0.3) to determine whether a planet lies in the habitable zone. Incident stellar flux appears to be a better metric for stars unlike the Sun. These estimates, however, ignore the effect of clouds on planetary albedo and the fact that the climates of synchronously rotating planets are not well predicted by 1-D models. Given that most planet candidates that will be detected in the next few years will be tidally locked and orbiting M stars, how might the habitable zone e tailored to better in-form characterization with scarce observing resources?

  8. Quantitative Outline-based Shape Analysis and Classification of Planetary Craterforms using Supervised Learning Models

    Science.gov (United States)

    Slezak, Thomas Joseph; Radebaugh, Jani; Christiansen, Eric

    2017-10-01

    The shapes of craterform morphology on planetary surfaces provides rich information about their origins and evolution. While morphologic information provides rich visual clues to geologic processes and properties, the ability to quantitatively communicate this information is less easily accomplished. This study examines the morphology of craterforms using the quantitative outline-based shape methods of geometric morphometrics, commonly used in biology and paleontology. We examine and compare landforms on planetary surfaces using shape, a property of morphology that is invariant to translation, rotation, and size. We quantify the shapes of paterae on Io, martian calderas, terrestrial basaltic shield calderas, terrestrial ash-flow calderas, and lunar impact craters using elliptic Fourier analysis (EFA) and the Zahn and Roskies (Z-R) shape function, or tangent angle approach to produce multivariate shape descriptors. These shape descriptors are subjected to multivariate statistical analysis including canonical variate analysis (CVA), a multiple-comparison variant of discriminant analysis, to investigate the link between craterform shape and classification. Paterae on Io are most similar in shape to terrestrial ash-flow calderas and the shapes of terrestrial basaltic shield volcanoes are most similar to martian calderas. The shapes of lunar impact craters, including simple, transitional, and complex morphology, are classified with a 100% rate of success in all models. Multiple CVA models effectively predict and classify different craterforms using shape-based identification and demonstrate significant potential for use in the analysis of planetary surfaces.

  9. NASA's Solar System Treks: Online Portals for Planetary Mapping and Modeling

    Science.gov (United States)

    Day, Brian

    2017-01-01

    NASA's Solar System Treks are a suite of web-based of lunar and planetary mapping and modeling portals providing interactive visualization and analysis tools enabling mission planners, planetary scientists, students, and the general public to access mapped lunar data products from past and current missions for the Moon, Mars, Vesta, and more. New portals for additional planetary bodies are being planned. This presentation will recap significant enhancements to these toolsets during the past year and look ahead to future features and releases. Moon Trek is a new portal replacing its predecessor, the Lunar Mapping and Modeling Portal (LMMP), that significantly upgrades and builds upon the capabilities of LMMP. It features greatly improved navigation, 3D visualization, fly-overs, performance, and reliability. Additional data products and tools continue to be added. These include both generalized products as well as polar data products specifically targeting potential sites for NASA's Resource Prospector mission as well as for missions being planned by NASA's international partners. The latest release of Mars Trek includes new tools and data products requested by NASA's Planetary Science Division to support site selection and analysis for Mars Human Landing Exploration Zone Sites. Also being given very high priority by NASA Headquarters is Mars Trek's use as a means to directly involve the public in upcoming missions, letting them explore the areas the agency is focusing upon, understand what makes these sites so fascinating, follow the selection process, and get caught up in the excitement of exploring Mars. Phobos Trek, the latest effort in the Solar System Treks suite, is being developed in coordination with the International Phobos/Deimos Landing Site Working Group, with landing site selection and analysis for JAXA's MMX (Martian Moons eXploration) mission as a primary driver.

  10. Testing the chondrule-rich accretion model for planetary embryos using calcium isotopes

    Science.gov (United States)

    Amsellem, Elsa; Moynier, Frédéric; Pringle, Emily A.; Bouvier, Audrey; Chen, Heng; Day, James M. D.

    2017-07-01

    Understanding the composition of raw materials that formed the Earth is a crucial step towards understanding the formation of terrestrial planets and their bulk composition. Calcium is the fifth most abundant element in terrestrial planets and, therefore, is a key element with which to trace planetary composition. However, in order to use Ca isotopes as a tracer of Earth's accretion history, it is first necessary to understand the isotopic behavior of Ca during the earliest stages of planetary formation. Chondrites are some of the oldest materials of the Solar System, and the study of their isotopic composition enables understanding of how and in what conditions the Solar System formed. Here we present Ca isotope data for a suite of bulk chondrites as well as Allende (CV) chondrules. We show that most groups of carbonaceous chondrites (CV, CI, CR and CM) are significantly enriched in the lighter Ca isotopes (δ 44 / 40 Ca = + 0.1 to + 0.93 ‰) compared with bulk silicate Earth (δ 44 / 40 Ca = + 1.05 ± 0.04 ‰, Huang et al., 2010) or Mars, while enstatite chondrites are indistinguishable from Earth in Ca isotope composition (δ 44 / 40 Ca = + 0.91 to + 1.06 ‰). Chondrules from Allende are enriched in the heavier isotopes of Ca compared to the bulk and the matrix of the meteorite (δ 44 / 40 Ca = + 1.00 to + 1.21 ‰). This implies that Earth and Mars have Ca isotope compositions that are distinct from most carbonaceous chondrites but that may be like chondrules. This Ca isotopic similarity between Earth, Mars, and chondrules is permissive of recent dynamical models of planetary formation that propose a chondrule-rich accretion model for planetary embryos.

  11. NASA's Solar System Treks: Online Portals for Planetary Mapping and Modeling

    Science.gov (United States)

    Day, B. H.; Law, E.

    2017-12-01

    NASA's Solar System Treks are a suite of web-based of lunar and planetary mapping and modeling portals providing interactive visualization and analysis tools enabling mission planners, planetary scientists, students, and the general public to access mapped lunar data products from past and current missions for the Moon, Mars, Vesta, and more. New portals for additional planetary bodies are being planned. This presentation will recap significant enhancements to these toolsets during the past year and look ahead to future features and releases. Moon Trek is a new portal replacing its predecessor, the Lunar Mapping and Modeling Portal (LMMP), that significantly upgrades and builds upon the capabilities of LMMP. It features greatly improved navigation, 3D visualization, fly-overs, performance, and reliability. Additional data products and tools continue to be added. These include both generalized products as well as polar data products specifically targeting potential sites for NASA's Resource Prospector mission as well as for missions being planned by NASA's international partners. The latest release of Mars Trek includes new tools and data products requested by NASA's Planetary Science Division to support site selection and analysis for Mars Human Landing Exploration Zone Sites. Also being given very high priority by NASA Headquarters is Mars Trek's use as a means to directly involve the public in upcoming missions, letting them explore the areas the agency is focusing upon, understand what makes these sites so fascinating, follow the selection process, and get caught up in the excitement of exploring Mars. Phobos Trek, the latest effort in the Solar System Treks suite, is being developed in coordination with the International Phobos/Deimos Landing Site Working Group, with landing site selection and analysis for JAXA's MMX mission as a primary driver.

  12. The Albedo of Kepler's Small Worlds

    Science.gov (United States)

    Jansen, Tiffany; Kipping, David

    2018-01-01

    The study of exoplanet phase curves has been established as a powerful tool for measuring the atmospheric properties of other worlds. To first order, phase curves have the same amplitude as occultations, yet far greater temporal baselines enabling substantial improvements in sensitivity. Even so, only a relatively small fraction of Kepler planets have detectable phase curves, leading to a population dominated by hot-Jupiters. One way to boost sensitivity further is to stack different planets of similar types together, giving rise to an average phase curve for a specific ensemble. In this work, we measure the average albedo, thermal redistribution efficiency, and greenhouse boosting factor from the average phase curves of 115 Neptunian and 50 Terran (solid) worlds. We construct ensemble phase curve models for both samples accounting for the reflection and thermal components and regress our models assuming a global albedo, redistribution factor and greenhouse factor in a Bayesian framework. We find modest evidence for a detected phase curve in the Neptunian sample, although the albedo and thermal properties are somewhat degenerate meaning we can only place an upper limit on the albedo of Ag < 0.23 and greenhouse factor of f < 1.40 to 95% confidence. As predicted theoretically, this confirms hot-Neptunes are darker than Neptune and Uranus. Additionally, we place a constraint on the albedo of solid, Terran worlds of Ag < 0.42 and f < 1.60 to 95% confidence, compatible with a dark Lunar-like surface.

  13. IMPEx : enabling model/observational data comparison in planetary plasma sciences

    Science.gov (United States)

    Génot, V.; Khodachenko, M.; Kallio, E. J.; Al-Ubaidi, T.; Alexeev, I. I.; Topf, F.; Gangloff, M.; André, N.; Bourrel, N.; Modolo, R.; Hess, S.; Perez-Suarez, D.; Belenkaya, E. S.; Kalegaev, V.

    2013-09-01

    The FP7 IMPEx infrastructure, whose general goal is to encourage and facilitate inter-comparison between observational and model data in planetary plasma sciences, is now established for 2 years. This presentation will focus on a tour of the different achievements which occurred during this period. Within the project, data originate from multiple sources : large observational databases (CDAWeb, AMDA at CDPP, CLWeb at IRAP), simulation databases for hybrid and MHD codes (FMI, LATMOS), planetary magnetic field models database and online services (SINP). Each of these databases proposes dedicated access to their models and runs (HWA@FMI, LATHYS@LATMOS, SMDC@SINP). To gather this large data ensemble, IMPEx offers a distributed framework in which these data may be visualized, analyzed, and shared thanks to interoperable tools; they comprise of AMDA - an online space physics analysis tool -, 3DView - a tool for data visualization in 3D planetary context -, and CLWeb - an online space physics visualization tool. A simulation data model, based on SPASE, has been designed to ease data exchange within the infrastructure. On the communication point of view, the VO paradigm has been retained and the architecture is based on web services and the IVOA protocol SAMP. The presentation will focus on how the tools may be operated synchronously to manipulate these heterogeneous data sets. Use cases based on in-flight missions and associated model runs will be proposed for the demonstration. Finally the motivation and functionalities of the future IMPEx portal will be exposed. As requirements to and potentialities of joining the IMPEx infrastructure will be shown, the presentation could be seen as an invitation to other modeling teams in the community which may be interested to promote their results via IMPEx.

  14. Enhancement of the MODIS Daily Snow Albedo Product

    Science.gov (United States)

    Hall, Dorothy K.; Schaaf, Crystal B.; Wang, Zhuosen; Riggs, George A.

    2009-01-01

    The MODIS daily snow albedo product is a data layer in the MOD10A1 snow-cover product that includes snow-covered area and fractional snow cover as well as quality information and other metadata. It was developed to augment the MODIS BRDF/Albedo algorithm (MCD43) that provides 16-day maps of albedo globally at 500-m resolution. But many modelers require daily snow albedo, especially during the snowmelt season when the snow albedo is changing rapidly. Many models have an unrealistic snow albedo feedback in both estimated albedo and change in albedo over the seasonal cycle context, Rapid changes in snow cover extent or brightness challenge the MCD43 algorithm; over a 16-day period, MCD43 determines whether the majority of clear observations was snow-covered or snow-free then only calculates albedo for the majority condition. Thus changes in snow albedo and snow cover are not portrayed accurately during times of rapid change, therefore the current MCD43 product is not ideal for snow work. The MODIS daily snow albedo from the MOD10 product provides more frequent, though less robust maps for pixels defined as "snow" by the MODIS snow-cover algorithm. Though useful, the daily snow albedo product can be improved using a daily version of the MCD43 product as described in this paper. There are important limitations to the MOD10A1 daily snow albedo product, some of which can be mitigated. Utilizing the appropriate per-pixel Bidirectional Reflectance Distribution Functions (BRDFs) can be problematic, and correction for anisotropic scattering must be included. The BRDF describes how the reflectance varies with view and illumination geometry. Also, narrow-to-broadband conversion specific for snow on different surfaces must be calculated and this can be difficult. In consideration of these limitations of MOD10A1, we are planning to improve the daily snow albedo algorithm by coupling the periodic per-pixel snow albedo from MCD43, with daily surface ref|outanoom, In this paper, we

  15. Numerical Modeling of Normal-Mode Oscillations in Planetary Atmospheres: Application to Saturn and Titan

    Science.gov (United States)

    Friedson, Andrew James; Ding, Leon

    2015-11-01

    We have developed a numerical model to calculate the frequencies and eigenfunctions of adiabatic, non-radial normal-mode oscillations in the gas giants and Titan. The model solves the linearized momentum, energy, and continuity equations for the perturbation displacement, pressure, and density fields and solves Poisson’s equation for the perturbation gravitational potential. The response to effects associated with planetary rotation, including the Coriolis force, centrifugal force, and deformation of the equilibrium structure, is calculated numerically. This provides the capability to accurately compute the influence of rotation on the modes, even in the limit where mode frequency approaches the rotation rate, when analytical estimates based on functional perturbation analysis become inaccurate. This aspect of the model makes it ideal for studying the potential role of low-frequency modes for driving spiral density waves in the C ring that possess relatively low pattern speeds (Hedman, M.M and P.D. Nicholson, MNRAS 444, 1369-1388). In addition, the model can be used to explore the effect of internal differential rotation on the eigenfrequencies. We will (1) present examples of applying the model to calculate the properties of normal modes in Saturn and their relationship to observed spiral density waves in the C ring, and (2) discuss how the model is used to examine the response of the superrotating atmosphere of Titan to the gravitational tide exerted by Saturn. This research was supported by a grant from the NASA Planetary Atmosphere Program.

  16. Model/observational data cross analysis in planetary plasma sciences with IMPEx

    Science.gov (United States)

    Genot, V. N.; Khodachenko, M.; Kallio, E. J.; Al-Ubaidi, T.; Alexeev, I. I.; Gangloff, M.; Bourrel, N.; andre, N.; Modolo, R.; Hess, S.; Topf, F.; Perez-Suarez, D.; Belenkaya, E. S.; Kalegaev, V. V.; Hakkinen, L. V.

    2013-12-01

    This presentation details how the FP7 IMPEx (http://impex-fp7.oeaw.ac.at/) infrastructure helps scientists in inter-comparing observational and model data in planetary plasma sciences. Within the project, data originate from multiple sources : large observational databases (CDAWeb, AMDA at CDPP, CLWeb at IRAP), simulation databases for hybrid and MHD codes (FMI, LATMOS), planetary magnetic field models database and online services (SINP). To navigate in this large data ensemble, IMPEx offers a distributed framework in which these data may be visualized, analyzed, and shared thanks to a set of interoperable tools (AMDA, 3DView, CLWeb). A simulation data model, based on SPASE, has been designed to ease data exchange within the infrastructure. On the communication point of view, the Virtual Observatory paradigm is followed and the architecture is based on web services and the IVOA protocol SAMP. These choices enabled a high level versatility with the goal to allow other model or data providers to distribute their own resources via the IMPEx infrastructure. A detailed use case based on Mars data and hybrid models will be proposed showing how the tools may be operated synchronously to manipulate heterogeneous data sets. Facilitating the analysis of the future MAVEN observations is one possible application of the IMPEx infrastructure.

  17. The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

    Science.gov (United States)

    Shields, Aomawa L; Meadows, Victoria S; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

    2013-08-01

    Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice

  18. The albedo of snow for partially cloudy skies

    Science.gov (United States)

    Choudhury, B. J.; Chang, A. T. C.

    1980-01-01

    The input parameters of the model are atmospheric precipitable water, ozone content, turbidity, cloud optical thickness, size and shape of ice crystal of snow and surface pressure. The model outputs spectral and integrated solar flux snow reflectance as a function of solar elevation and fractional cloudcover. The model is illustrated using representative parameters for the Antarctic coastal regions. The albedo for a clear sky depends inversely on the solar elevation. At high elevation the albedo depends primarily upon the grain size; at low elevation this dependence is on grain size and shape. The gradient of the albedo-elevation curve increases as the grains get larger and faceted. The albedo for a dense overcast is a few percent higher than the clear sky albedo at high elevations. A simple relation between the grain size and the overcast albedo is obtained. For a set of grain size and shape, the albedo matrices (the albedo as a function of solar elevation and fractional cloudcover) are tabulated.

  19. Europlanet-RI: Access to Planetary Data, Tools, Models and Support Information

    Science.gov (United States)

    Schmidt, W.; Capria, M. T.; Chanteur, G.

    2012-04-01

    During the past three years the Europlanet Research Infrastructure consortium with financial support from the EU's 7th framework program has developed a wide range of tools to support all aspects of planetary research. During the final year of the project these are being integrated into the "Integrated and Distributed Information Service IDIS" [1]. The challenge is the diversity of research fields involved in planetary research, each with its own way of collecting and archiving data and publishing its results. Nevertheless the results of one field are needed by others to be able to correctly interpret their observations, and to design new kinds of measurements to advance our knowledge of the Solar system. The IDIS team in close cooperation with the efforts of the International Planetary Data Alliance (IPDA) has developed a data model which allows the registration of a wide range of data sources including the results from modelling efforts thereby providing Virtual Observatory (IDIS-VO) [2,3] services for the community to register and access data from planetary data centres, laboratory measurements, spectral- and molecular data bases and simulations. Once a data set from any of these sources is registered with IDIS, it can be accessed, its used archive format translated into a compatible internal format and combined with other data using the visualization tools developed in connection with IDIS. Tools to calculate ephemeris data for a wide range of solar system bodies, to visualize their locations or identify them from existing images can be found as well as interactive tools to evaluate chemical reaction paths, spectral information from gas or solids or the mapping of planetary surfaces. Additionally information about ground observation possibilities, test facilities, laboratories, research institutes and scientists with detailed contact information is made available to the user. For the developers of new space instruments and operators of active missions support

  20. Dispersion of radionuclides released into a stable planetary boundary layer using a Monte Carlo model

    International Nuclear Information System (INIS)

    Basit, Abdul; Raza, S Shoaib; Irfan, Naseem

    2006-01-01

    In this paper a Monte Carlo model for describing the atmospheric dispersion of radionuclides (represented by Lagrangian particles/neutral tracers) continuously released into a stable planetary boundary layer is presented. The effect of variation in release height and wind directional shear on plume dispersion is studied. The resultant plume concentration and dose rate at the ground is also calculated. The turbulent atmospheric parameters, like vertical profiles of fluctuating wind velocity components and eddy lifetime, were calculated using empirical relations for a stable atmosphere. The horizontal and vertical dispersion coefficients calculated by a numerical Lagrangian model are compared with the original and modified Pasquill-Gifford and Briggs empirical σs. The comparison shows that the Monte Carlo model can successfully predict dispersion in a stable atmosphere using the empirical turbulent parameters. The predicted ground concentration and dose rate contours indicate a significant increase in the affected area when wind shear is accounted for in the calculations

  1. Multibody Model for Planetary Gearbox of 500 kW Wind Turbine

    DEFF Research Database (Denmark)

    Jørgensen, Martin Felix; Pedersen, Niels Leergaard; Sørensen, Jens Nørkær

    The aim of the work is to simulate the loadings in a planetary gearbox of a wind turbine using a multibody program. A realistic wind turbine gearbox of a 500 kW wind turbine is examined using turbulent inflow data. An aeroelastic model of the wind turbine has been set up using the FLEX5-code...... (industrial standard software). The FLEX5 model as well as the developed multibody code has been verified from strain gauge measurements, giving e.g. the main shaft torque, and met mast wind data measurements. The realistic measurements on both input and output variables form an excellent base for studying...... the gearbox fatigue loads, the effect of wind turbulence on the power production/output torque on the highspeed shaft and for calibration and verification of the gearbox model....

  2. Planetary resources and astroecology. Planetary microcosm models of asteroid and meteorite interiors: electrolyte solutions and microbial growth--implications for space populations and panspermia.

    Science.gov (United States)

    Mautner, Michael N

    2002-01-01

    Planetary microcosms were constructed using extracts from meteorites that simulate solutions in the pores of carbonaceous chondrites. The microcosms were found to support the growth of complex algal and microbial populations. Such astroecology experiments demonstrate how a diverse ecosystem could exist in fluids within asteroids, and in meteorites that land on aqueous planets. The microcosm solutions were obtained by extracting nutrient electrolytes under natural conditions from powders of the Allende (CV3) and Murchison (CM2) meteorites at low (0.02 g/ml) and high (10.0 g/ml) solid/solution ratios. The latter solutions contain > 3 mol/L electrolytes and about 10 g/L organics, that simulate natural fluids in asteroids during aqueous alteration and in the pores of meteorites, which can help prebiotic synthesis and the survival of early microorganisms. These solutions and wet solids were in fact found to support complex self-sustaining microbial communities with populations of 4 x 10(5) algae and 6 x 10(6) bacteria and fungi for long periods (> 8 months). The results show that planetary microcosms based on meteorites can: assay the fertilities of planetary materials; identify space bioresources; target astrobiology exploration; and model past and future space-based ecosystems. The results show that bioresources in the carbonaceous asteroids can sustain a biomass of 10(18) kg, comprising 10(32) microorganisms and a human population of 10(14). The results also suggest that protoplanetary nebulae can support and disperse microorganisms and can be therefore effective environments for natural and directed panspermia.

  3. Snow cover and vegetation-induced decrease in global albedo from 2002 to 2016

    OpenAIRE

    Li, Qiuping; Ma, Mingguo; Wu, Xiaodan; Yang, Hong

    2018-01-01

    Land surface albedo is an essential parameter in regional and global climate models, and it is markedly influenced by land cover change. Variations in the albedo can affect the surface radiation budget and further impact the global climate. In this study, the interannual variation of albedo from 2002 to 2016 was estimated on the global scale using Moderate Resolution Imaging Spectroradiometer (MODIS) datasets. The presence and causes of the albedo changes for each specific region were also ex...

  4. Measurements of spectral snow albedo at Neumayer, Antarctica

    Directory of Open Access Journals (Sweden)

    S. Wuttke

    2006-03-01

    Full Text Available Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional component of the snow reflectivity for direct incidence, combined with a slightly mislevelled sensor and the snow surface not being perfectly horizontal. A possible explanation for an observed decline in albedo is an increase in snow grain size. The theoretically predicted increase in albedo with increasing solar zenith angle (SZA could not be observed. This is explained by the small range of SZA during albedo measurements, combined with the effect of changing snow conditions outweighing the effect of changing SZA. The measured spectral albedo serves as input for radiative transfer models, describing radiation conditions in Antarctica.

  5. The importance of accurate glacier albedo for estimates of surface mass balance on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations

    Science.gov (United States)

    Steffensen Schmidt, Louise; Aðalgeirsdóttir, Guðfinna; Guðmundsson, Sverrir; Langen, Peter L.; Pálsson, Finnur; Mottram, Ruth; Gascoin, Simon; Björnsson, Helgi

    2017-07-01

    A simulation of the surface climate of Vatnajökull ice cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980-2014, is used to estimate the evolution of the glacier surface mass balance (SMB). This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the ice albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs) from the period 2001-2014, as well as in situ SMB measurements from the period 1995-2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net mass balance for the whole of Vatnajökull (1995-2014) shows a good overall fit during the summer, with a small mass balance underestimation of 0.04 m w.e. on average, whereas the winter mass balance is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the ice cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981-2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes currently not accounted for in RCMs

  6. The importance of accurate glacier albedo for estimates of surface mass balance on Vatnajökull: evaluating the surface energy budget in a regional climate model with automatic weather station observations

    Directory of Open Access Journals (Sweden)

    L. S. Schmidt

    2017-07-01

    Full Text Available A simulation of the surface climate of Vatnajökull ice cap, Iceland, carried out with the regional climate model HIRHAM5 for the period 1980–2014, is used to estimate the evolution of the glacier surface mass balance (SMB. This simulation uses a new snow albedo parameterization that allows albedo to exponentially decay with time and is surface temperature dependent. The albedo scheme utilizes a new background map of the ice albedo created from observed MODIS data. The simulation is evaluated against observed daily values of weather parameters from five automatic weather stations (AWSs from the period 2001–2014, as well as in situ SMB measurements from the period 1995–2014. The model agrees well with observations at the AWS sites, albeit with a general underestimation of the net radiation. This is due to an underestimation of the incoming radiation and a general overestimation of the albedo. The average modelled albedo is overestimated in the ablation zone, which we attribute to an overestimation of the thickness of the snow layer and not taking the surface darkening from dirt and volcanic ash deposition during dust storms and volcanic eruptions into account. A comparison with the specific summer, winter, and net mass balance for the whole of Vatnajökull (1995–2014 shows a good overall fit during the summer, with a small mass balance underestimation of 0.04 m w.e. on average, whereas the winter mass balance is overestimated by on average 0.5 m w.e. due to too large precipitation at the highest areas of the ice cap. A simple correction of the accumulation at the highest points of the glacier reduces this to 0.15 m w.e. Here, we use HIRHAM5 to simulate the evolution of the SMB of Vatnajökull for the period 1981–2014 and show that the model provides a reasonable representation of the SMB for this period. However, a major source of uncertainty in the representation of the SMB is the representation of the albedo, and processes

  7. ISLSCP II MODIS (Collection 4) Albedo, 2002

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The MODIS BRDF/Albedo Product (MOD43B) provides measures of clear sky surface albedo every 16 days. Both white-sky albedo (bihemispherical reflectance) and...

  8. Simple Model-Free Controller for the Stabilization of Planetary Inverted Pendulum

    Directory of Open Access Journals (Sweden)

    Huanhuan Mai

    2012-01-01

    Full Text Available A simple model-free controller is presented for solving the nonlinear dynamic control problems. As an example of the problem, a planetary gear-type inverted pendulum (PIP is discussed. To control the inherently unstable system which requires real-time control responses, the design of a smart and simple controller is made necessary. The model-free controller proposed includes a swing-up controller part and a stabilization controller part; neither controller has any information about the PIP. Since the input/output scaling parameters of the fuzzy controller are highly sensitive, we use genetic algorithm (GA to obtain the optimal control parameters. The experimental results show the effectiveness and robustness of the present controller.

  9. A Model for the Dynamical and Ionization Structure of Planetary Nebula IC 418

    Directory of Open Access Journals (Sweden)

    J. Ghanbari

    1997-04-01

    Full Text Available   The interacting two winds model and a spherical density distribution function are introduced to study the dynamical and ionization structure of the planetary nebula IC 418. A fast wind with a mechanical luminousity  2/34×1034erg.s-1 of interacts with a super wind with a mass-loss rate of  2×10-5M(°yr-1 and  a velocity of 10 , and produces a dense and luminous medium.   In this model, the expansion velocities of OI and HI lines are predicted to be 11 and 10.5kms-1 , respectively. The calculated dynamical time-scale 1033yr for the nebula is in good agreement with the evolution time of the central star after the interaction of the two winds. Our calculations give a luminosity  0.05M(°of for the central star

  10. Arecibo Radar Observation of Near-Earth Asteroids: Expanded Sample Size, Determination of Radar Albedos, and Measurements of Polarization Ratios

    Science.gov (United States)

    Lejoly, Cassandra; Howell, Ellen S.; Taylor, Patrick A.; Springmann, Alessondra; Virkki, Anne; Nolan, Michael C.; Rivera-Valentin, Edgard G.; Benner, Lance A. M.; Brozovic, Marina; Giorgini, Jon D.

    2017-10-01

    The Near-Earth Asteroid (NEA) population ranges in size from a few meters to more than 10 kilometers. NEAs have a wide variety of taxonomic classes, surface features, and shapes, including spheroids, binary objects, contact binaries, elongated, as well as irregular bodies. Using the Arecibo Observatory planetary radar system, we have measured apparent rotation rate, radar reflectivity, apparent diameter, and radar albedos for over 350 NEAs. The radar albedo is defined as the radar cross-section divided by the geometric cross-section. If a shape model is available, the actual cross-section is known at the time of the observation. Otherwise we derive a geometric cross-section from a measured diameter. When radar imaging is available, the diameter was measured from the apparent range depth. However, when radar imaging was not available, we used the continuous wave (CW) bandwidth radar measurements in conjunction with the period of the object. The CW bandwidth provides apparent rotation rate, which, given an independent rotation measurement, such as from lightcurves, constrains the size of the object. We assumed an equatorial view unless we knew the pole orientation, which gives a lower limit on the diameter. The CW also provides the polarization ratio, which is the ratio of the SC and OC cross-sections.We confirm the trend found by Benner et al. (2008) that taxonomic types E and V have very high polarization ratios. We have obtained a larger sample and can analyze additional trends with spin, size, rotation rate, taxonomic class, polarization ratio, and radar albedo to interpret the origin of the NEAs and their dynamical processes. The distribution of radar albedo and polarization ratio at the smallest diameters (≤50 m) differs from the distribution of larger objects (>50 m), although the sample size is limited. Additionally, we find more moderate radar albedos for the smallest NEAs when compared to those with diameters 50-150 m. We will present additional trends we

  11. Evaluation of Preindustrial to Present-day Black Carbon and its Albedo Forcing from Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y. H.; Lamarque, J.-F.; Flanner, M. G.; Jiao, C.; Shindell, Drew; Berntsen, T.; Bisiauxs, M.; Cao, J.; Collins, W. J.; Curran, M.; Edwards, R.; Faluvegi, G.; Ghan, Steven J.; Horowitz, L.; McConnell, J.R.; Ming, J.; Myhre, G.; Nagashima, T.; Naik, Vaishali; Rumbold, S.; Skeie, R. B.; Sudo, K.; Takemura, T.; Thevenon, F.; Xu, B.; Yoon, Jin-Ho

    2013-03-05

    As a part of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), we evaluate the historical black carbon (BC) aerosols simulated by 8 ACCMIP models against the observations including 12 ice core records, a long-term surface mass concentrations and recent Arctic BC snowpack measurements. We also estimate BC albedo forcing by performing additional simulations using the NCAR Community Land and Sea-Ice model 4 with prescribed meteorology from 1996-2000, which includes the SNICAR BC-snow model. We evaluated the vertical profile of BC snow concentrations from these offline simulations to using recent BC snowpack measurements. Despite using the same BC emissions, global BC burden differs by approximately a factor of 3 among models due to the differences in aerosol removal parameterizations and simulated meteorology among models; 34 Gg to 103 Gg in 1850 and 82 Gg to 315 Gg in 2000. However,models agree well on 2.5~3 times increase in the global BC burden from preindustrial to present-day, which matches with the 2.5 times increase in BC emissions. We find a large model diversity at both NH and SH high latitude regions for BC burden and at SH high latitude regions for deposition fluxes. The ACCMIP simulations match the observed BC mass concentrations well in Europe and North America except at Jungfrauch and Ispra. However, the models fail to capture the Arctic BC seasonality due tosevere underestimations during winter and spring. Compared to recent snowpack measurements, the simulated vertically resolved BC snow concentrations are, on average, within a factor of 2-3 of observations except for Greenland and Arctic Ocean. However, model and observation differ widely due to missing interannual variations in emissions and possibly due to the choice of the prescribed meteorology period (i.e., 1996-2000).

  12. Planetary nebulae

    International Nuclear Information System (INIS)

    Amnuehl', P.R.

    1985-01-01

    The history of planetary nebulae discovery and their origin and evolution studies is discussed in a popular way. The problem of planetary nebulae central star is considered. The connection between the white-draft star and the planetary nebulae formulation is shown. The experimental data available acknowledge the hypothesis of red giant - planetary nebula nucleus - white-draft star transition process. Masses of planetary nebulae white-draft stars and central stars are distributed practically similarly: the medium mass is close to 0.6Msub(Sun) (Msub(Sun) - is the mass of the Sun)

  13. Simulations of tropical rainforest albedo: is canopy wetness important?

    Directory of Open Access Journals (Sweden)

    Silvia N.M. Yanagi

    Full Text Available Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  14. High Fidelity Modeling of Plume-Induced Soil Erosion During Lunar and Planetary Landing

    Data.gov (United States)

    National Aeronautics and Space Administration — During lunar and planetary landings, rocket plumes interact with the surface, ejecting soil and other particles into the surrounding environment. These particles,...

  15. Close packing effects on clean and dirty snow albedo and associated climatic implications

    Science.gov (United States)

    He, Cenlin; Takano, Yoshi; Liou, Kuo-Nan

    2017-04-01

    Previous modeling of snow albedo, a key climate feedback parameter, follows the independent scattering approximation (ISA) such that snow grains are considered as a number of separate units with distances longer than wavelengths. Here we develop a new snow albedo model for widely observed close-packed snow grains internally mixed with black carbon (BC) and demonstrate that albedo simulations match closer to observations. Close packing results in a stronger light absorption for clean and BC-contaminated snow. Compared with ISA, close packing reduces pure snow albedos by up to 0.05, whereas it enhances BC-induced snow albedo reduction and associated surface radiative forcing by up to 15% (20%) for fresh (old) snow, with larger enhancements for stronger structure packing. Finally, our results suggest that BC-snow albedo forcing and snow albedo feedback (climate sensitivity) are underestimated in previous modeling studies, making snow close packing consideration a necessity in climate modeling and analysis.

  16. Dust in planetary nebulae

    International Nuclear Information System (INIS)

    Kwok, S.

    1980-01-01

    A two-component dust model is suggested to explain the infrared emission from planetary nebulae. A cold dust component located in the extensive remnant of the red-giant envelope exterior to the visible nebula is responsible for the far-infrared emission. A ward dust component, which is condensed after the formation of the planetary nebula and confined within the ionized gas shell, emits most of the near- and mid-infrared radiation. The observations of NGC 7027 are shown to be consisten with such a model. The correlation of silicate emission in several planetary nebulae with an approximately +1 spectral index at low radio frequencies suggests that both the silicate and radio emissions originate from the remnant of the circumstellar envelope of th precursor star and are observable only while the planetary nebula is young. It is argued that oxygen-rich stars as well as carbon-rich stars can be progenitors of planetary nebulae

  17. Surface albedo measurements in Mexico City metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Castro, T; Mar, B; Longoria, R; Ruiz Suarez, L. G [Centro de Ciencias de la Atmosfera, UNAM, Mexico, D.F. (Mexico); Morales, L [Instituto de Geografia, UNAM, Mexico, D.F. (Mexico)

    2001-04-01

    Optical and thermal properties of soils are important input data for the meteorological and photochemical modules of air quality models. As development of these models increase on spatial resolution good albedo data become more important. In this paper measurements of surface albedo of UV (295-385 nm) and visible (450-550 nm) radiation are reported for different urban and rural surfaces in the vicinity of Mexico City. It was found for the downtown zone and average albedo value of 0.05 which is in very good agreement with reported values for urban surfaces. Our albedo values measured in UV region for grey cement and green grass are of 0.10 and 0.009, respectively, and quite similar to those found at the literature of 0.11 and 0.008 for those type of surfaces. [Spanish] Las propiedades opticas y termicas de suelos son datos importantes para los modulos meteorologicos y fotoquimicos de los modelos de calidad del aire. Conforme aumenta la resolucion espacial del modelo se vuelve mas importante contar con buenos datos de albedo. En este articulo se presentan mediciones de albedo superficial de radiacion Ultravioleta (295-385 nm) y visible (450-550 nm) para diferentes superficies urbanas. Los valores medidos de albedo en la region UV para cemento gris y pasto verde son de 0.10 y 0.009, respectivamente, y son muy similares a los reportados en la literatura, 0.11 y 0.008 para este tipo de superficies.

  18. AVHRR Surface Temperature and Narrow-Band Albedo Comparison with Ground Measurements for the Greenland Ice Sheet

    Science.gov (United States)

    Haefliger, M.; Steffen, K.; Fowler, C.

    1993-01-01

    An ice-surface temperature retrieval algorithm for the Greenland ice sheet was developed using NOAA 11 thermal radiances from channels 4 and 5. Temperature, pressure and humidity profiles, cloud observations and skin temperatures from the Swiss Federal Institute of Technology (ETH) camp, located at the equilibrium line altitude at 49 deg17 min W, 69 deg 34 min N, were used in the LOWTRAN 7 model. Through a statistical analysis of daily clear sky profiles, the coefficients that correct for the atmospheric effects were determined for the ETH-Camp field season (May to August). Surface temperatures retrieved by this method were then compared against the in situ observations with a maximum difference of 0.6 K. The NOAA 11 narrow-band planetary albedo values for channels 1 and 2 were calculated using pre-launch calibration coefficients. Scattering and absorption by the atmosphere were modelled with LOWTRAN 7. Then, narrow-band albedo values for the AVHRR visible and near infrared channels were compared with in situ high resolution spectral reflectance measurements. In the visible band (580-680 nm), AVHRR-derived narrow-band albedo and the in situ measurements corrected with radiative transfer model LOWTRAN 7 showed a difference of less than 2%. For the near infrared channel (725-1100 nm) the difference between the measured and modelled narrow-band albedo was 14%. These discrepancies could be either the result of inaccurate aerosol scattering modelling (lack of the in situ observation), or the result of sensor drift due to degradation.

  19. MODELING OF DYNAMIC PROCESSES IN PLANETARY IN-WHEEL MOTOR GEARBOXES OF MINE TRUCKS DURING ITS STARTING AND ACCELERATION

    Directory of Open Access Journals (Sweden)

    V. V. Mikhailov

    2012-01-01

    Full Text Available The paper describes a mathematical model for planetary double-row in-wheel motor gear box. Main parameters of its dynamic system have been determined in the paper. The paper reveals simulation of transition processes during starting and acceleration of a mine truck with electric motor wheels. Its own gear box frequency has been established theoretically and experimentally in the paper. The paper proposes an algorithm and program for calculations as an alternative to high-cost tests while investigating gear mechanism dynamics of large-size planetary gearboxes.

  20. A Multi-Scale Validation Strategy for Albedo Products over Rugged Terrain and Preliminary Application in Heihe River Basin, China

    Directory of Open Access Journals (Sweden)

    Xingwen Lin

    2018-01-01

    Full Text Available The issue for the validation of land surface remote sensing albedo products over rugged terrain is the scale effects between the reference albedo measurements and coarse scale albedo products, which is caused by the complex topography. This paper illustrates a multi-scale validation strategy specified for coarse scale albedo validation over rugged terrain. A Mountain-Radiation-Transfer-based (MRT-based albedo upscaling model was proposed in the process of multi-scale validation strategy for aggregating fine scale albedo to coarse scale. The simulated data of both the reference coarse scale albedo and fine scale albedo were used to assess the performance and uncertainties of the MRT-based albedo upscaling model. The results showed that the MRT-based model could reflect the albedo scale effects over rugged terrain and provided a robust solution for albedo upscaling from fine scale to coarse scale with different mean slopes and different solar zenith angles. The upscaled coarse scale albedos had the great agreements with the simulated coarse scale albedo with a Root-Mean-Square-Error (RMSE of 0.0029 and 0.0017 for black sky albedo (BSA and white sky albedo (WSA, respectively. Then the MRT-based model was preliminarily applied for the assessment of daily MODerate Resolution Imaging Spectroradiometer (MODIS Albedo Collection V006 products (MCD43A3 C6 over rugged terrain. Results showed that the MRT-based model was effective and suitable for conducting the validation of MODIS albedo products over rugged terrain. In this research area, it was shown that the MCD43A3 C6 products with full inversion algorithm, were generally in agreement with the aggregated coarse scale reference albedos over rugged terrain in the Heihe River Basin, with the BSA RMSE of 0.0305 and WSA RMSE of 0.0321, respectively, which were slightly higher than those over flat terrain.

  1. On the modeling of planetary plasma environments by a fully kinetic electromagnetic global model HYB-em

    Directory of Open Access Journals (Sweden)

    V. Pohjola

    2010-03-01

    Full Text Available We have developed a fully kinetic electromagnetic model to study instabilities and waves in planetary plasma environments. In the particle-in-a-cell (PIC model both ions and electrons are modeled as particles. An important feature of the developed global kinetic model, called HYB-em, compared to other electromagnetic codes is that it is built up on an earlier quasi-neutral hybrid simulation platform called HYB and that it can be used in conjunction with earlier hybrid models. The HYB models have been used during the past ten years to study globally the flowing plasma interaction with various Solar System objects: Mercury, Venus, the Moon, Mars, Saturnian moon Titan and asteroids. The new stand-alone fully kinetic model enables us to (1 study the stability of various planetary plasma regions in three-dimensional space, (2 analyze the propagation of waves in a plasma environment derived from the other global HYB models. All particle processes in a multi-ion plasma which are implemented on the HYB platform (e.g. ion-neutral-collisions, chemical processes, particle loss and production processes are also automatically included in HYB-em model.

    In this brief report we study the developed approach by analyzing the propagation of high frequency electromagnetic waves in non-magnetized plasma in two cases: We study (1 expansion of a spherical wave generated from a point source and (2 propagation of a plane wave in plasma. The analysis shows that the HYB-em model is capable of describing these space plasma situations successfully. The analysis also suggests the potential of the developed model to study both high density-high magnetic field plasma environments, such as Mercury, and low density-low magnetic field plasma environments, such as Venus and Mars.

  2. On the modeling of planetary plasma environments by a fully kinetic electromagnetic global model HYB-em

    Directory of Open Access Journals (Sweden)

    V. Pohjola

    2010-03-01

    Full Text Available We have developed a fully kinetic electromagnetic model to study instabilities and waves in planetary plasma environments. In the particle-in-a-cell (PIC model both ions and electrons are modeled as particles. An important feature of the developed global kinetic model, called HYB-em, compared to other electromagnetic codes is that it is built up on an earlier quasi-neutral hybrid simulation platform called HYB and that it can be used in conjunction with earlier hybrid models. The HYB models have been used during the past ten years to study globally the flowing plasma interaction with various Solar System objects: Mercury, Venus, the Moon, Mars, Saturnian moon Titan and asteroids. The new stand-alone fully kinetic model enables us to (1 study the stability of various planetary plasma regions in three-dimensional space, (2 analyze the propagation of waves in a plasma environment derived from the other global HYB models. All particle processes in a multi-ion plasma which are implemented on the HYB platform (e.g. ion-neutral-collisions, chemical processes, particle loss and production processes are also automatically included in HYB-em model. In this brief report we study the developed approach by analyzing the propagation of high frequency electromagnetic waves in non-magnetized plasma in two cases: We study (1 expansion of a spherical wave generated from a point source and (2 propagation of a plane wave in plasma. The analysis shows that the HYB-em model is capable of describing these space plasma situations successfully. The analysis also suggests the potential of the developed model to study both high density-high magnetic field plasma environments, such as Mercury, and low density-low magnetic field plasma environments, such as Venus and Mars.

  3. Planetary Atmospheric Electricity

    CERN Document Server

    Leblanc, F; Yair, Y; Harrison, R. G; Lebreton, J. P; Blanc, M

    2008-01-01

    This volume presents our contemporary understanding of atmospheric electricity at Earth and in other solar system atmospheres. It is written by experts in terrestrial atmospheric electricity and planetary scientists. Many of the key issues related to planetary atmospheric electricity are discussed. The physics presented in this book includes ionisation processes in planetary atmospheres, charge generation and separation, and a discussion of electromagnetic signatures of atmospheric discharges. The measurement of thunderstorms and lightning, including its effects and hazards, is highlighted by articles on ground and space based instrumentation, and new missions.Theory and modelling of planetary atmospheric electricity complete this review of the research that is undertaken in this exciting field of space science. This book is an essential research tool for space scientists and geoscientists interested in electrical effects in atmospheres and planetary systems. Graduate students and researchers who are new to t...

  4. Modeling Radar Scattering by Planetary Regoliths for Varying Angles of Incidence

    Science.gov (United States)

    Prem, P.; Patterson, G. W.; Zimmerman, M. I.

    2017-12-01

    Bistatic radar observations can play an important role in characterizing the texture and composition of planetary regoliths. Multiple scattering within a closely-packed particulate medium, such as a regolith, can lead to a response referred to as the Coherent Backscatter Opposition Effect (CBOE), associated with an increase in the intensity of backscattered radiation and an increase in Circular Polarization Ratio (CPR) at small bistatic angles. The nature of the CBOE is thought to depend not only on regolith properties, but also on the angle of incidence (Mishchenko, 1992). The latter factor is of particular interest in light of recent radar observations of the Moon over a range of bistatic and incidence angles by the Mini-RF instrument (on board the Lunar Reconnaissance Orbiter), operating in bistatic mode with a ground-based transmitter at the Arecibo Observatory. These observations have led to some intriguing results that are not yet well-understood ­- for instance, the lunar South Polar crater Cabeus shows an elevated CPR at only some combinations of incidence angle/bistatic angle, a potential clue to the depth distribution of water ice at the lunar poles (Patterson et al., 2017). Our objective in this work is to develop a model for radar scattering by planetary regoliths that can assist in the interpretation of Mini-RF observations. We approach the problem by coupling the Multiple Sphere T-Matrix (MSTM) code of Mackowski and Mishchenko (2011) to a Monte Carlo radiative transfer model. The MSTM code is based on the solution of Maxwell's equations for the propagation of electromagnetic waves in the presence of a cluster of scattering/absorbing spheres, and can be used to model the scattering of radar waves by an aggregation of nominal regolith particles. The scattering properties thus obtained serve as input to the Monte Carlo model, which is used to simulate radar scattering at larger spatial scales. The Monte Carlo approach has the advantage of being able to

  5. MODIS/Terra+Aqua BRDF/Albedo Albedo Daily L3 Global - 500m V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS MCD43A3 Version 6 Albedo Model data set is a daily 16-day product. The Julian date in the granule ID of each specific file represents the 9th day of the 16...

  6. Model planetary nebulae: the effect of shadowed filaments on low ionization potential ion radiation

    International Nuclear Information System (INIS)

    Katz, A.

    1977-01-01

    Previous homogeneous model planetary nebulae calculations No. 4 have yielded emission strengths for low ionization potential No. 4 ions which are considerably lower than those observed. Several attempts were to correct this problem by the inclusion of optically thin condensations, the use of energy flux distributions from stellar model calculations instead of blackbody spectrum stars, and the inclusion of dust in the nebulae. The effect that shadowed filaments have on the ionization and thermal structure of model nebulae and the resultant line strengths are considered. These radial filaments are shielded from the direct stellar ionizing radiation by optically thick condensations in the nebula. Theoretical observational evidence exists for the presence of condensations and filaments. Since the only source of ionizing photons in the shadowed filaments is due to diffuse photons produced by recombination, ions of lower ionization potential are expected to exist there in greater numbers than those found in the rest of the nebula. This leads to increased line strengths from these ions and increases their values to match the observational values. It is shown that these line strengths in the filaments increase by over one to two orders of magnitude relative to values found in homogeneous models. This results in an increase of approximately one order of magnitude for these lines when contributions from both components of the nebula are considered. The parameters that determine the exact value of the increase are the radial location of the filaments in the nebula and the fraction of the nebular volume occupied by the filaments

  7. A Model of Thermal Conductivity for Planetary Soils. 2; Theory for Cemented Soils

    Science.gov (United States)

    Piqueux, S.; Christensen, P. R.

    2009-01-01

    A numerical model of heat conduction through particulate media made of spherical grains cemented by various bonding agents is presented. The pore-filling gas conductivity, volume fraction, and thermal conductivity of the cementing phase are tunable parameters. Cement fractions <0.001-0.01% in volume have small effects on the soil bulk thermal conductivity. A significant conductivity increase (factor 3-8) is observed for bond fractions of 0.01 to 1% in volume. In the 1 to 15% bond fraction domain, the conductivity increases continuously but less intensely (25-100% conductivity increase compared to a 1% bond system). Beyond 15% of cements, the conductivity increases vigorously and the bulk conductivity rapidly approaches that of bedrock. The composition of the cements (i.e. conductivity) has little influence on the bulk thermal inertia of the soil, especially if the volume of bond <10%. These results indicate that temperature measurements are sufficient to detect cemented soils and quantify the amount of cementing phase, but the mineralogical nature of the bonds and the typical grain size are unlikely to be determined from orbit. On Mars, a widespread surface unit characterized by a medium albedo (0.19-0.26) and medium/high thermal inertia (200-600 J s(0.5)/sq m/K) has long been hypothesized to be associated with a duricrust. The fraction of cement required to fit the thermal data is less than approx.1-5% by volume. This small amount of material is consistent with orbital observations, confirming that soil cementation is an important factor controlling the thermal inertia of the Martian surface

  8. A Model of Thermal Conductivity for Planetary Soils. 2; Theory for Cemented Soils

    Science.gov (United States)

    Piqueux, S.; Christensen, P. R.

    2009-01-01

    A numerical model of heat conduction through particulate media made of spherical grains cemented by various bonding agents is presented. The pore-filling gas conductivity, volume fraction, and thermal conductivity of the cementing phase are tunable parameters. Cement fractions conductivity. A significant conductivity increase (factor 3-8) is observed for bond fractions of 0.01 to 1% in volume. In the 1 to 15% bond fraction domain, the conductivity increases continuously but less intensely (25-100% conductivity increase compared to a 1% bond system). Beyond 15% of cements, the conductivity increases vigorously and the bulk conductivity rapidly approaches that of bedrock. The composition of the cements (i.e. conductivity) has little influence on the bulk thermal inertia of the soil, especially if the volume of bond <10%. These results indicate that temperature measurements are sufficient to detect cemented soils and quantify the amount of cementing phase, but the mineralogical nature of the bonds and the typical grain size are unlikely to be determined from orbit. On Mars, a widespread surface unit characterized by a medium albedo (0.19-0.26) and medium/high thermal inertia (200-600 J s(0.5)/sq m/K) has long been hypothesized to be associated with a duricrust. The fraction of cement required to fit the thermal data is less than approx.1-5% by volume. This small amount of material is consistent with orbital observations, confirming that soil cementation is an important factor controlling the thermal inertia of the Martian surface

  9. Enhancement of marine cloud albedo via controlled sea spray injections: a global model study of the influence of emission rates, microphysics and transport

    Directory of Open Access Journals (Sweden)

    H. Korhonen

    2010-05-01

    Full Text Available Modification of cloud albedo by controlled emission of sea spray particles into the atmosphere has been suggested as a possible geoengineering option to slow global warming. Previous global studies have imposed changes in cloud drop concentration in low level clouds to explore the radiative and climatic effects. Here, we use a global aerosol transport model to quantify how an imposed flux of sea spray particles affects the natural aerosol processes, the particle size distribution, and concentrations of cloud drops. We assume that the proposed fleet of vessels emits sea spray particles with a wind speed-dependent flux into four regions of persistent stratocumulus cloud off the western coasts of continents. The model results show that fractional changes in cloud drop number concentration (CDNC vary substantially between the four regions because of differences in wind speed (which affects the spray efficiency of the vessels, transport and particle deposition rates, and because of variations in aerosols from natural and anthropogenic sources. Using spray emission rates comparable to those implied by previous studies we find that the predicted CDNC changes are very small (maximum 20% and in one of the four regions even negative. The weak or negative effect is because the added particles suppress the in-cloud supersaturation and prevent existing aerosol particles from forming cloud drops. A scenario with five times higher emissions (considerably higher than previously assumed increases CDNC on average by 45–163%, but median concentrations are still below the 375 cm−3 assumed in previous studies. An inadvertent effect of the spray emissions is that sulphur dioxide concentrations are suppressed by 1–2% in the seeded regions and sulphuric acid vapour by 64–68% due to chemical reactions on the additional salt particles. The impact of this suppression on existing aerosol is negligible in the model, but should be investigated further in

  10. An Improved Rigid Multibody Model for the Dynamic Analysis of the Planetary Gearbox in a Wind Turbine

    Directory of Open Access Journals (Sweden)

    Wenguang Yang

    2016-01-01

    Full Text Available This paper proposes an improved rigid multibody model for the dynamic analysis of the planetary gearbox in a wind turbine. The improvements mainly include choosing the inertia frame as the reference frame of the carrier, the ring, and the sun and adding a new degree of freedom for each planet. An element assembly method is introduced to build the model, and a time-varying mesh stiffness model is presented. A planetary gear study case is employed to verify the validity of the improved model. Comparisons between the improvement model and the traditional model show that the natural characteristics are very close; the improved model can obtain the right equivalent moment of inertia of the planetary gear in the transient simulation, and all the rotation speeds satisfy the transmission relationships well; harmonic resonance and resonance modulation phenomena can be found in their vibration signals. The improved model is applied in a multistage gearbox dynamics analysis to reveal the prospects of the model. Modal analysis and transient analysis with and without time-varying mesh stiffness considered are conducted. The rotation speeds from the transient analysis are consistent with the theory, and resonance modulation can be found in the vibration signals.

  11. Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers

    Directory of Open Access Journals (Sweden)

    J. E. Box

    2012-08-01

    Full Text Available Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite-derived surface albedo with calibrated regional climate modeled surface air temperature and surface downward solar irradiance, we determine the spatial dependence and quantitative impact of the ice sheet albedo feedback over 12 summer periods beginning in 2000. We find that, while albedo feedback defined by the change in net solar shortwave flux and temperature over time is positive over 97% of the ice sheet, when defined using paired annual anomalies, a second-order negative feedback is evident over 63% of the accumulation area. This negative feedback damps the accumulation area response to warming due to a positive correlation between snowfall and surface air temperature anomalies. Positive anomaly-gauged feedback concentrated in the ablation area accounts for more than half of the overall increase in melting when satellite-derived melt duration is used to define the timing when net shortwave flux is sunk into melting. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme since 2007, enabled three amplifying mechanisms to maximize the albedo feedback: (1 increased warm (south air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; (2 increased surface downward shortwave flux, leading to more surface heating and further albedo reduction; and (3 reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net infrared and solar radiation for the high elevation accumulation area approached

  12. Elements of a stochastic precipitation model: from drop to planetary scales

    Science.gov (United States)

    Lovejoy, S.; Schertzer, D.

    2009-04-01

    Technological advances have now permitted observations of precipitation over wide ranges of scales including the extreme small drop scales (using stereophotography to determine the liquid water density) and the extreme large planetary scales (using satellite borne radar to measure reflectivities). Statistical analyses show that at small scales (less than roughly 30 - 50 cm depending on the rate) rain is organized into "patches" at scales such that the Stokes number (St) >1; the implied decoupling of the rain with the turbulence leads to high wavenumber white noise spectrum so that the patches are statistically homogeneous. At larger scales, where St Poisson process yielding a model in which the drop positions and sizes are specified in a way that is compatible with turbulence theory and the observations: the key is the scaling of the rain drop number density. When the number density is low the discrete nature of the particles acts as a rain/no rain threshold. Complete theoretical analysis of this compound Poisson - multifractal model is difficult: it imples that the thresholding is both stochastic and coupled with the turbulence. However, we show by a simple approximation that the model does yield the observed change in exponents. We further argue that it can potentially explain both observations of precipitation scaling as well as those finding breaks in the scaling: the latter being fundamentally consequences of rain - no rain transitions.

  13. REFLECTED LIGHT CURVES, SPHERICAL AND BOND ALBEDOS OF JUPITER- AND SATURN-LIKE EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Dyudina, Ulyana; Kopparla, Pushkar; Ingersoll, Andrew P.; Yung, Yuk L. [Division of Geological and Planetary Sciences, 150-21 California Institute of Technology, Pasadena, CA 91125 (United States); Zhang, Xi [University of California Santa Cruz 1156 High Street, Santa Cruz, CA 95064 (United States); Li, Liming [Department of Physics, University of Houston, Houston, TX 77204 (United States); Dones, Luke [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder CO 80302 (United States); Verbiscer, Anne, E-mail: ulyana@gps.caltech.edu [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)

    2016-05-10

    Reflected light curves observed for exoplanets indicate that a few of them host bright clouds. We estimate how the light curve and total stellar heating of a planet depends on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet’s phase. These observations cover broadbands at 0.59–0.72 and 0.39–0.5 μ m, and narrowbands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24–0.28 μ m. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter and Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of ∼1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating.

  14. Characterization of a Planetary Boundary Layer model to evaluate radionuclides releases in nuclear installations

    International Nuclear Information System (INIS)

    Molnary, Leslie de

    1993-01-01

    A two layer bulk model is used to simulate numerically the time and spatial evolution of concentration of radionuclides in the Planetary Boundary Layer (PBL) for convective and stable conditions. In this model, the closure hypothesis are based on the integrated version of the Turbulent Kinetics Energy (TKE) equation (Smeda,1979). This type of model was adopted here because it is numerically simple to be applied operationally in routine and emergency support systems of atmospheric releases at nuclear power plants, and the hypothesis of the efficiency of the vertical mixing seems to be physically reasonable to simulated PBL evolution for high wind conditions and stable conditions in Subtropical latitudes regions. In order to validate the model to the nuclear power plants of the Centro Experimental Aramar (CEA), located in Ipero, State of Sao Paulo, Brazil, numerical simulations were carried out with initial and boundary conditions based on vertical profiles of temperature and horizontal wind speed and direction obtained from tethered balloon soundings, synoptic charts at 850 hPa and surface observations. Comparisons between a 24 hour long numerical simulation and observations indicate that the model is capable of reproduce the diurnal evolution of temperature and horizontal wind during the convective regime. During stable conditions, the slab model was able to simulate the intensity of the surface inversion as a difference between the mixed layer and surface temperatures. The simulated mixed layer height matches with observations during the convective and stable regime. A daytime release of radionuclides was simulated for CEA region and the results indicated that the maximum relative concentration reaches a distance about 15 Km in 1 hour, varing from 100 times background at the moment of the release to 15 times the background. For night releases, the maximum concentration reaches the same distance in 45 minutes, varing from 100 to 30 times the background values

  15. Interpretation of two compact planetary nebulae, IC 4997 and NGC 6572, with aid of theoretical models.

    Science.gov (United States)

    Hyung, S; Aller, L H

    1993-01-15

    Observations of two dense compact planetary nebulae secured with the Hamilton Echelle spectrograph at Lick Observatory combined with previously published UV spectra secured with the International Ultraviolet Explorer enable us to probe the electron densities and temperatures (plasma diagnostics) and ionic concentrations in these objects. The diagnostic diagrams show that no homogenous model will work for these nebulae. NGC 6572 may consist of an inner torordal ring of density 25,000 atoms/cm3 and an outer conical shell of density 10,000 atoms/cm3. The simplest model of IC 4997 suggests a thick inner shell with a density of about 107 atoms/cm3 and an outer envelope of density 10,000 atoms/cm3. The abundances of all elements heavier than He appear to be less than the solar values in NGC 6572, whereas He, C, N, and O may be more abundant in IC 4997 than in the sun. IC 4997 presents puzzling problems.

  16. An Investigation of Ice Surface Albedo and Its Influence on the High-Altitude Lakes of the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Jiahe Lang

    2018-02-01

    Full Text Available Most high-altitude lakes are more sensitive to global warming than the regional atmosphere. However, most existing climate models produce unrealistic surface temperatures on the Tibetan Plateau (TP lakes, and few studies have focused on the influence of ice surface albedo on high-altitude lakes. Based on field albedo measurements, moderate resolution imaging spectrometer (MODIS albedo products and numerical simulation, this study evaluates the ice albedo parameterization schemes in existing lake models and investigates the characteristics of the ice surface albedo in six typical TP lakes, as well as the influence of ice albedo error in the FLake model. Compared with observations, several ice albedo schemes all clearly overestimate the lake ice albedo by 0.26 to 0.66, while the average bias of MODIS albedo products is only 0.07. The MODIS-observed albedo of a snow-covered lake varies with the snow proportion, and the lake surface albedo in a snow-free state is approximately 0.15 during the frozen period. The MODIS-observed ice surface (snow-free albedos are concentrated within the ranges of 0.14–0.16, 0.08–0.10 and 0.10–0.12 in Aksai Chin Lake, Nam Co Lake and Ngoring Lake, respectively. The simulated lake surface temperature is sensitive to variations in lake ice albedo especially in the spring and winter.

  17. Modelling the light-scattering properties of a planetary-regolith analog sample

    Science.gov (United States)

    Vaisanen, T.; Markkanen, J.; Hadamcik, E.; Levasseur-Regourd, A. C.; Lasue, J.; Blum, J.; Penttila, A.; Muinonen, K.

    2017-12-01

    Solving the scattering properties of asteroid surfaces can be made cheaper, faster, and more accurate with reliable physics-based electromagnetic scattering programs for large and dense random media. Existing exact methods fail to produce solutions for such large systems and it is essential to develop approximate methods. Radiative transfer (RT) is an approximate method which works for sparse random media such as atmospheres fails when applied to dense media. In order to make the method applicable to dense media, we have developed a radiative-transfer coherent-backscattering method (RT-CB) with incoherent interactions. To show the current progress with the RT-CB, we have modeled a planetary-regolith analog sample. The analog sample is a low-density agglomerate produced by random ballistic deposition of almost equisized silicate spheres studied using the PROGRA2-surf experiment. The scattering properties were then computed with the RT-CB assuming that the silicate spheres were equisized and that there were a Gaussian particle size distribution. The results were then compared to the measured data and the intensity plot is shown below. The phase functions are normalized to unity at the 40-deg phase angle. The tentative intensity modeling shows good match with the measured data, whereas the polarization modeling shows discrepancies. In summary, the current RT-CB modeling is promising, but more work needs to be carried out, in particular, for modeling the polarization. Acknowledgments. Research supported by European Research Council with Advanced Grant No. 320773 SAEMPL, Scattering and Absorption of ElectroMagnetic waves in ParticuLate media. Computational resources provided by CSC - IT Centre for Science Ltd, Finland.

  18. Modeling pN2through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures.

    Science.gov (United States)

    Stüeken, E E; Kipp, M A; Koehler, M C; Schwieterman, E W; Johnson, B; Buick, R

    2016-12-01

    Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N 2 , but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean-presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N 2 pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN 2 and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN 2 to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO 2 , and (c) atmospheric oxygenation could have initiated a stepwise pN 2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN 2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N 2 and O 2 is a signature of an oxygen-producing biosphere. Key Words: Biosignatures-Early Earth-Planetary atmospheres. Astrobiology 16, 949-963.

  19. A Common Model to Handle PDS3 and PDS4 Data in the New Planetary Science Archive (PSA)

    Science.gov (United States)

    Macfarlane, A. J.; Barbarisi, I.; Rios, C.; Docasal, R.; Martinez, S.; Arviset, C.; Besse, S.; De Marchi, G.; Grotheer, E.; Gonzalez, J.; Lim, T.; Fraga, D.; Barthelemy, M.

    2015-12-01

    The first of the European Space Agency's (ESA) planetary missions to make use of the latest release of the Planetary Data Standards (PDS4) are currently in advanced stages of development (ExoMars, BepiColombo). This occurs at a time when the Planetary Science Archive (PSA) has been undergoing a complete reengineering in order to increase the accessibility of ESA's planetary data holdings utilising the latest technologies and to significantly improve the user experience for both the specialist scientific community and general public alike. The PSA must also keep on handling PDS3 data arriving to the archive from active missions (Rosetta, Mars Express, Venus Express) as well as continuing to provide access to missions that have reached the legacy phase (Huygens, SMART1, Giotto). Therefore, as part of the reengineering of the PSA, an effort has been made to map the key metadata from PDS3 and PDS4 into a common data model with the intention of providing transparency to the services that make up the new PSA, and consequently to the end user. We present how this common mapping allows the PSA to support the data deliveries from the pipelines of existing missions without the need to reprocess the PDS3 data and in addition how it should simplify the data deliveries from PDS4 missions. We review how the implementation of this data model, involving a PostgreSQL database with the PostGIS extension, enables the new PSA to be able to provide multiple methods of interoperability used by the international community, such as PDAP (Planetary Data Access Protocol), EPN-TAP (EuroPlanet-Table Access Protocol), and GIS-enabled technologies without the user having to know in detail the underlying structure of the data format.

  20. Narrowband-to-broadband albedo conversion for glacier ice and snow: equations based on modeling and ranges of validity of the equations

    NARCIS (Netherlands)

    Greuell, W.; Oerlemans, J.

    2004-01-01

    In this paper, we propose equations for narrowband-to-broadband (NTB) albedo conversion for glacier ice and snow for four types of satellite sensors: thematic mapper (TM), advanced very high resolution radiometer (AVHRR), moderate resolution imaging spectroradiometer (MODIS), and multi-angle imaging

  1. Greenland ice sheet albedo variability and feedback: 2000-2015

    Science.gov (United States)

    Box, J. E.; van As, D.; Fausto, R. S.; Mottram, R.; Langen, P. P.; Steffen, K.

    2015-12-01

    Absorbed solar irradiance represents the dominant source of surface melt energy for Greenland ice. Surface melting has increased as part of a positive feedback amplifier due to surface darkening. The 16 most recent summers of observations from the NASA MODIS sensor indicate a darkening exceeding 6% in July when most melting occurs. Without the darkening, the increase in surface melting would be roughly half as large. A minority of the albedo decline signal may be from sensor degradation. So, in this study, MOD10A1 and MCD43 albedo products from MODIS are evaluated for sensor degradation and anisotropic reflectance errors. Errors are minimized through calibration to GC-Net and PROMICE Greenland snow and ice ground control data. The seasonal and spatial variability in Greenland snow and ice albedo over a 16 year period is presented, including quantifying changing absorbed solar irradiance and melt enhancement due to albedo feedback using the DMI HIRHAM5 5 km model.

  2. Satellite-based albedo, sea surface temperature and effective land roughness maps used in the HIRLAM model for weather and climate scenarios

    Science.gov (United States)

    Hasager, C. B.; Nielsen, N. W.; Christensen, J. H.; Soegaard, H.; Boegh, E.; Rasmussen, M. S.; Jensen, N. O.

    2001-12-01

    A study is conducted on the effect of introducing maps of geophysical parameters retrieved from satellite Earth Observation data into the atmospheric model HIRLAM (HIgh Resolution Limited Area Model). . The HIRLAM system was developed by the HIRLAM project group, a cooperative project of the national weather services in Denmark, Finland, Iceland, Ireland, the Netherlands, Norway and Sweden. It is currently used by weather services in several European countries. The exchanges of sensible heat, water vapour and momentum between the land- and ocean surface and the atmosphere are very important dynamical processes in this type of model. The results from the HIRLAM model when using the improved surface boundary conditions is validated from wind and temperature data at synoptic weather stations and surface flux data from land- and ocean meteorological masts in Denmark. The results from a set of scenarios covering the hurricane in Denmark in December 1999 and several springtime cases in 2000 show improved weather forecasts. The methodology on retrieving improved boundary conditions is based on satellite image data. Maps on the geophysical parameters albedo and sea surface temperature are retrieved at a 1 km spatial resolution from NOAA AVHRR. Furthermore, land cover maps based on Landsat TM satellite data are used to assess the regional roughness. The high-resolution land roughness map (Areal Systems Information in a 25 m pixel resolution) is area-averaged into effective roughness values (15 km grid) by using a non-linear aggregation technique (QJRMS 1999, vol 125, 2075-2102). The area-averaging is highly non-linear due to the turbulent physical processes involved. Thus the effective surface conditions cannot be obtained by simple averaging but only by a flow model taking horizontal advection into consideration. The effect of hedges in the landscape is included as a correction index based on a vector-based map. The land surface fluxes of heat and water vapour is also

  3. Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface.

    Science.gov (United States)

    Zheng, Zhiyuan; Wei, Zhigang; Wen, Zhiping; Dong, Wenjie; Li, Zhenchao; Wen, Xiaohang; Zhu, Xian; Ji, Dong; Chen, Chen; Yan, Dongdong

    2017-12-01

    Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

  4. Dynamical models to explain observations with SPHERE in planetary systems with double debris belts

    Science.gov (United States)

    Lazzoni, C.; Desidera, S.; Marzari, F.; Boccaletti, A.; Langlois, M.; Mesa, D.; Gratton, R.; Kral, Q.; Pawellek, N.; Olofsson, J.; Bonnefoy, M.; Chauvin, G.; Lagrange, A. M.; Vigan, A.; Sissa, E.; Antichi, J.; Avenhaus, H.; Baruffolo, A.; Baudino, J. L.; Bazzon, A.; Beuzit, J. L.; Biller, B.; Bonavita, M.; Brandner, W.; Bruno, P.; Buenzli, E.; Cantalloube, F.; Cascone, E.; Cheetham, A.; Claudi, R. U.; Cudel, M.; Daemgen, S.; De Caprio, V.; Delorme, P.; Fantinel, D.; Farisato, G.; Feldt, M.; Galicher, R.; Ginski, C.; Girard, J.; Giro, E.; Janson, M.; Hagelberg, J.; Henning, T.; Incorvaia, S.; Kasper, M.; Kopytova, T.; LeCoroller, H.; Lessio, L.; Ligi, R.; Maire, A. L.; Ménard, F.; Meyer, M.; Milli, J.; Mouillet, D.; Peretti, S.; Perrot, C.; Rouan, D.; Samland, M.; Salasnich, B.; Salter, G.; Schmidt, T.; Scuderi, S.; Sezestre, E.; Turatto, M.; Udry, S.; Wildi, F.; Zurlo, A.

    2018-03-01

    circular or eccentric orbit. We then consider multi-planetary systems: two and three equal-mass planets on circular orbits and two equal-mass planets on eccentric orbits in a packed configuration. As a final step, we compare each couple of values (Mp, ap), derived from the dynamical analysis of single and multiple planetary models, with the detection limits obtained with SPHERE. Results: For one single planet on a circular orbit we obtain conclusive results that allow us to exclude such a hypothesis since in most cases this configuration requires massive planets which should have been detected by our observations. Unsatisfactory is also the case of one single planet on an eccentric orbit for which we obtained high masses and/or eccentricities which are still at odds with observations. Introducing multi planetary architectures is encouraging because for the case of three packed equal-mass planets on circular orbits we obtain quite low masses for the perturbing planets which would remain undetected by our SPHERE observations. The case of two equal-mass planets on eccentric orbits is also of interest since it suggests the possible presence of planets with masses lower than the detection limits and with moderate eccentricity. Our results show that the apparent lack of planets in gaps between double belts could be explained by the presence of a system of two or more planets possibly of low mass and on eccentric orbits whose sizes are below the present detection limits. Based on observations collected at Paranal Observatory, ESO (Chile) Program ID: 095.C-0298, 096.C-0241, 097.C-0865, and 198.C-0209.

  5. Estimation of a planetary magnetic field using a reduced magnetohydrodynamic model

    Directory of Open Access Journals (Sweden)

    C. Nabert

    2017-03-01

    Full Text Available Knowledge of planetary magnetic fields provides deep insights into the structure and dynamics of planets. Due to the interaction of a planet with the solar wind plasma, a rather complex magnetic environment is generated. The situation at planet Mercury is an example of the complexities occurring as this planet's field is rather weak and the magnetosphere rather small. New methods are presented to separate interior and exterior magnetic field contributions which are based on a dynamic inversion approach using a reduced magnetohydrodynamic (MHD model and time-varying spacecraft observations. The methods select different data such as bow shock location information or magnetosheath magnetic field data. Our investigations are carried out in preparation for the upcoming dual-spacecraft BepiColombo mission set out to precisely estimate Mercury's intrinsic magnetic field. To validate our new approaches, we use THEMIS magnetosheath observations to estimate the known terrestrial dipole moment. The terrestrial magnetosheath provides observations from a strongly disturbed magnetic environment, comparable to the situation at Mercury. Statistical and systematic errors are considered and their dependence on the selected data sets are examined. Including time-dependent upstream solar wind variations rather than averaged conditions significantly reduces the statistical error of the estimation. Taking the entire magnetosheath data along the spacecraft's trajectory instead of only the bow shock location into account further improves accuracy of the estimated dipole moment.

  6. Quantifying the ice-albedo feedback through decoupling

    Science.gov (United States)

    Kravitz, B.; Rasch, P. J.

    2017-12-01

    The ice-albedo feedback involves numerous individual components, whereby warming induces sea ice melt, inducing reduced surface albedo, inducing increased surface shortwave absorption, causing further warming. Here we attempt to quantify the sea ice albedo feedback using an analogue of the "partial radiative perturbation" method, but where the governing mechanisms are directly decoupled in a climate model. As an example, we can isolate the insulating effects of sea ice on surface energy and moisture fluxes by allowing sea ice thickness to change but fixing Arctic surface albedo, or vice versa. Here we present results from such idealized simulations using the Community Earth System Model in which individual components are successively fixed, effectively decoupling the ice-albedo feedback loop. We isolate the different components of this feedback, including temperature change, sea ice extent/thickness, and air-sea exchange of heat and moisture. We explore the interactions between these different components, as well as the strengths of the total feedback in the decoupled feedback loop, to quantify contributions from individual pieces. We also quantify the non-additivity of the effects of the components as a means of investigating the dominant sources of nonlinearity in the ice-albedo feedback.

  7. Albedo as a modulator of climate response to tropical deforestation

    Science.gov (United States)

    Dirmeyer, Paul A.; Shukla, J.

    1994-01-01

    An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local climate due to tropical deforestation for the Amazon basin. One control and three anomaly integrations of 4 years' duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in climate, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.

  8. Pile driving models for the evaluation of soil penetration resistance measurements from planetary subsurface probes

    Science.gov (United States)

    Kömle, Norbert I.; Poganski, Joshua; Kargl, Günter; Grygorczuk, Jerzy

    2015-05-01

    Several planetary lander missions conducted in the past and planned for the near future have instruments on board, which are dedicated to the determination of various material properties, among them mechanical properties of the surface like material strength and penetration resistance. In this paper two instruments are considered in more detail: (i) the MUPUS penetrator, a device aboard the Lander Philae of ESA's Rosetta mission, and (ii) the Mole HP3, which is part of the payload of NASA's next Discovery mission InSight, due for landing on Mars in 2016. Both devices are driven by hammering mechanisms designed to work under low or micro-gravity conditions and blaze themselves a trail into the subsurface of their respective target bodies. Naturally the speed with which this process takes place and if penetration is possible at all depends on the mechanical properties of the soil. However, a quantitative evaluation of soil mechanical parameters from measured depth-versus-time data is not a straightforward task. In this paper we apply an old technique, originally developed for modelling the driving of a pile into the ground, to describe the performance of penetrators and Moles developed for planetary applications. The numerical pile driving model of Smith (1962) is scaled and adapted for this purpose and used to predict the penetration behaviour of these instruments in dependence of their internal construction and the properties of the soil they are driven in. The model computes the permanent set of the surrounding soil in response to one hammer blow cycle as well as the oscillations and waves excited inside the devices and in the surrounding soil. Both the penetration resistance of the tip and the resistance caused by friction of the penetrator along the cylindrical side wall are calculated. By comparing the modelling results with previous laboratory measurements it is demonstrated that the models produce realistic results and can be used both as tools for proper

  9. Albedo and transmittance of inhomogeneous stratus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Zuev, V.E.; Kasyanov, E.I.; Titov, G.A. [Institute of Atmospheric Optics, Tomsk (Russian Federation)] [and others

    1996-04-01

    A highly important topic is the study of the relationship between the statistical parameters of optical and radiative charactertistics of inhomogeneous stratus clouds. This is important because the radiation codes of general circulation models need improvement, and it is important for geophysical information. A cascade model has been developed at the Goddard Space Flight Center to treat stratocumulus clouds with the simplest geometry and horizontal fluctuations of the liquid water path (optical thickness). The model evaluates the strength with which the stochastic geometry of clouds influences the statistical characteristics of albedo and the trnasmittance of solar radiation.

  10. An investigation of ozone and planetary boundary layer dynamics over the complex topography of Grenoble combining measurements and modeling

    OpenAIRE

    Couach, O.; Balin, I.; Jiménez, R.; Ristori, P.; Perego, S.; Kirchner, F.; Simeonov, V.; Calpini, B.; Van Den Bergh, H.

    2003-01-01

    This paper concerns an evaluation of ozone (O3) and planetary boundary layer (PBL) dynamics over the complex topography of the Grenoble region through a combination of measurements and mesoscale model (METPHOMOD) predictions for three days, during July 1999. The measurements of O3 and PBL structure were obtained with a Differential Absorption Lidar (DIAL) system, situated 20 km south of Grenoble at Vif (310 m ASL). The combined lidar observations ...

  11. Design of a Novel Spectral Albedometer for Validating the MODerate Resolution Imaging Spectroradiometer Spectral Albedo Product

    Directory of Open Access Journals (Sweden)

    Hongmin Zhou

    2018-01-01

    Full Text Available Land surface shortwave broadband albedo is a key parameter in general circulation models and surface energy budget models. Multispectral satellite data are typically used to generate broadband albedo products in a three-step process: atmospheric correction, for converting the top-of-atmosphere observations to surface directional reflectance; angular modeling, for converting the surface directional reflectance to spectral albedo of each individual band; and finally, narrowband-to-broadband conversion, for transforming the spectral albedos to broadband albedos. Spectroradiometers can be used for validating surface directional reflectance products and pyranometers or broadband albedometers, for validating broadband albedo products, but spectral albedo products are rarely validated using ground measurements. In this study, we designed a new type of albedometer that can measure spectral albedos. It consists of multiple interference filters and a silicon detector, for measuring irradiance from 400–1100 nm. The linearity of the sensors is 99%, and the designed albedometer exhibits consistency up to 0.993, with a widely-used commercial instrument. A field experiment for measuring spectral albedo of grassland using this new albedometer was conducted in Yudaokou, China and the measurements are used for validating the MODerate Resolution Imaging Spectroradiometer (MODIS spectral albedos. The results show that the biases of the MODIS spectral albedos of the first four bands are −0.0094, 0.0065, 0.0159, and −0.0001, respectively. This new instrument provides an effective technique for validating spectral albedos of any satellite sensor in this spectral range, which is critical for improving satellite broadband albedo products.

  12. An Investigation of Ice Surface Albedo and Its Influence on the High-Altitude Lakes of the Tibetan Plateau

    OpenAIRE

    Jiahe Lang; Shihua Lyu; Zhaoguo Li; Yaoming Ma; Dongsheng Su

    2018-01-01

    Most high-altitude lakes are more sensitive to global warming than the regional atmosphere. However, most existing climate models produce unrealistic surface temperatures on the Tibetan Plateau (TP) lakes, and few studies have focused on the influence of ice surface albedo on high-altitude lakes. Based on field albedo measurements, moderate resolution imaging spectrometer (MODIS) albedo products and numerical simulation, this study evaluates the ice albedo parameterization schemes in existing...

  13. Co-registration of Laser Altimeter Tracks with Digital Terrain Models and Applications in Planetary Science

    Science.gov (United States)

    Glaeser, P.; Haase, I.; Oberst, J.; Neumann, G. A.

    2013-01-01

    We have derived algorithms and techniques to precisely co-register laser altimeter profiles with gridded Digital Terrain Models (DTMs), typically derived from stereo images. The algorithm consists of an initial grid search followed by a least-squares matching and yields the translation parameters at sub-pixel level needed to align the DTM and the laser profiles in 3D space. This software tool was primarily developed and tested for co-registration of laser profiles from the Lunar Orbiter Laser Altimeter (LOLA) with DTMs derived from the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) stereo images. Data sets can be co-registered with positional accuracy between 0.13 m and several meters depending on the pixel resolution and amount of laser shots, where rough surfaces typically result in more accurate co-registrations. Residual heights of the data sets are as small as 0.18 m. The software can be used to identify instrument misalignment, orbit errors, pointing jitter, or problems associated with reference frames being used. Also, assessments of DTM effective resolutions can be obtained. From the correct position between the two data sets, comparisons of surface morphology and roughness can be made at laser footprint- or DTM pixel-level. The precise co-registration allows us to carry out joint analysis of the data sets and ultimately to derive merged high-quality data products. Examples of matching other planetary data sets, like LOLA with LRO Wide Angle Camera (WAC) DTMs or Mars Orbiter Laser Altimeter (MOLA) with stereo models from the High Resolution Stereo Camera (HRSC) as well as Mercury Laser Altimeter (MLA) with Mercury Dual Imaging System (MDIS) are shown to demonstrate the broad science applications of the software tool.

  14. How Does the Shape of the Stellar Spectrum Affect the Raman Scattering Features in the Albedo of Exoplanets?

    Energy Technology Data Exchange (ETDEWEB)

    Oklopčić, Antonija [California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Hirata, Christopher M. [Center for Cosmology and Astroparticle Physics, Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 (United States); Heng, Kevin, E-mail: oklopcic@astro.caltech.edu [Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012, Bern (Switzerland)

    2017-09-10

    The diagnostic potential of the spectral signatures of Raman scattering, imprinted in planetary albedo spectra at short optical wavelengths, has been demonstrated in research on planets in the solar system, and has recently been proposed as a probe of exoplanet atmospheres, complementary to albedo studies at longer wavelengths. Spectral features caused by Raman scattering offer insight into the properties of planetary atmospheres, such as the atmospheric depth, composition, and temperature, as well as the possibility of detecting and spectroscopically identifying spectrally inactive species, such as H{sub 2} and N{sub 2}, in the visible wavelength range. Raman albedo features, however, depend on both the properties of the atmosphere and the shape of the incident stellar spectrum. Identical planetary atmospheres can produce very different albedo spectra depending on the spectral properties of the host star. Here we present a set of geometric albedo spectra calculated for atmospheres with H{sub 2}/He, N{sub 2}, and CO{sub 2} composition, irradiated by different stellar types ranging from late A to late K stars. Prominent albedo features caused by Raman scattering appear at different wavelengths for different types of host stars. We investigate how absorption due to the alkali elements sodium and potassium may affect the intensity of Raman features, and we discuss the preferred strategies for detecting Raman features in future observations.

  15. How Does the Shape of the Stellar Spectrum Affect the Raman Scattering Features in the Albedo of Exoplanets?

    International Nuclear Information System (INIS)

    Oklopčić, Antonija; Hirata, Christopher M.; Heng, Kevin

    2017-01-01

    The diagnostic potential of the spectral signatures of Raman scattering, imprinted in planetary albedo spectra at short optical wavelengths, has been demonstrated in research on planets in the solar system, and has recently been proposed as a probe of exoplanet atmospheres, complementary to albedo studies at longer wavelengths. Spectral features caused by Raman scattering offer insight into the properties of planetary atmospheres, such as the atmospheric depth, composition, and temperature, as well as the possibility of detecting and spectroscopically identifying spectrally inactive species, such as H_2 and N_2, in the visible wavelength range. Raman albedo features, however, depend on both the properties of the atmosphere and the shape of the incident stellar spectrum. Identical planetary atmospheres can produce very different albedo spectra depending on the spectral properties of the host star. Here we present a set of geometric albedo spectra calculated for atmospheres with H_2/He, N_2, and CO_2 composition, irradiated by different stellar types ranging from late A to late K stars. Prominent albedo features caused by Raman scattering appear at different wavelengths for different types of host stars. We investigate how absorption due to the alkali elements sodium and potassium may affect the intensity of Raman features, and we discuss the preferred strategies for detecting Raman features in future observations.

  16. Advanced Physical Models and Numerical Algorithms to Enable High-Fidelity Aerothermodynamic Simulations of Planetary Entry Vehicles on Emerging Distributed Heterogeneous Computing Architectures

    Data.gov (United States)

    National Aeronautics and Space Administration — The design and qualification of entry systems for planetary exploration largely rely on computational simulations. However, state-of-the-art modeling capabilities...

  17. ISLSCP II AVHRR Albedo and BRDF, 1995

    Data.gov (United States)

    National Aeronautics and Space Administration — This Albedo and BRDF (Bidirectional Reflectance Distribution Function) data set contains three files containing BRDF parameters, white- sky albedo and black-sky...

  18. Snow Cover and Vegetation-Induced Decrease in Global Albedo From 2002 to 2016

    Science.gov (United States)

    Li, Qiuping; Ma, Mingguo; Wu, Xiaodan; Yang, Hong

    2018-01-01

    Land surface albedo is an essential parameter in regional and global climate models, and it is markedly influenced by land cover change. Variations in the albedo can affect the surface radiation budget and further impact the global climate. In this study, the interannual variation of albedo from 2002 to 2016 was estimated on the global scale using Moderate Resolution Imaging Spectroradiometer (MODIS) datasets. The presence and causes of the albedo changes for each specific region were also explored. From 2002 to 2016, the MODIS-based albedo decreased globally, snow cover declined by 0.970 (percent per pixel), while the seasonally integrated normalized difference vegetation index increased by 0.175. Some obvious increases in the albedo were detected in Central Asia, northeastern China, parts of the boreal forest in Canada, and the temperate steppe in North America. In contrast, noticeable decreases in the albedo were found in the Siberian tundra, Europe, southeastern Australia, and northeastern regions of North America. In the Northern Hemisphere, the greening trend at high latitudes made more contribution to the decline in the albedo. However, the dramatic fluctuation of snow-cover at midlatitudes predominated in the change of albedo. Our analysis can help to understand the roles that vegetation and snow cover play in the variation of albedo on global and regional scales.

  19. Modelling of asteroid formation in planetary vortex and calculation its orbital parameters

    Directory of Open Access Journals (Sweden)

    L. V. Klychinska

    2015-01-01

    Full Text Available The theory of planetary vortex as the initial state of creation of the star systems is used to the study of conditions of formation of asteroids and calculation its orbital parameters. In application to Main asteroid belt of the Solar system the kind coincidence of theoretical and experimental data is got.

  20. Global albedos of Pluto and Charon from LORRI New Horizons observations

    Science.gov (United States)

    Buratti, B. J.; Hofgartner, J. D.; Hicks, M. D.; Weaver, H. A.; Stern, S. A.; Momary, T.; Mosher, J. A.; Beyer, R. A.; Verbiscer, A. J.; Zangari, A. M.; Young, L. A.; Lisse, C. M.; Singer, K.; Cheng, A.; Grundy, W.; Ennico, K.; Olkin, C. B.

    2017-05-01

    The exploration of the Pluto-Charon system by the New Horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's ;Third Zone; of distant ice-rich bodies. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that reveals surface albedo variegations larger than any other Solar System world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0, and the low-albedo areas of Pluto are darker than any region of Charon. Charon exhibits a much blander surface with normal reflectances ranging from 0.20-0.73. Pluto's albedo features are well-correlated with geologic features, although some exogenous low-albedo dust may be responsible for features seen to the west of the area informally named Tombaugh Regio. The albedo patterns of both Pluto and Charon are latitudinally organized, with the exception of Tombaugh Regio, with darker regions concentrated at the Pluto's equator and Charon's northern pole. The phase curve of Pluto is similar to that of Triton, the large moon of Neptune believed to be a captured Kuiper Belt Object (KBO), while Charon's is similar to that of the Moon. Preliminary Bond albedos are 0.25 ± 0.03 for Charon and 0.72 ± 0.07 for Pluto. Maps of an approximation to the Bond albedo for both Pluto and Charon are presented for the first time. Our work shows a connection between very high albedo (near unity) and planetary activity, a result that suggests the KBO Eris may be currently active.

  1. The Importance of Snow Albedo for Ice Sheet Evolution over the Last Glacial Cycle

    Science.gov (United States)

    Ganopolski, A.; Willeit, M.

    2017-12-01

    The surface energy and mass balance of ice sheets strongly depends on the amount of solar radiation absorbed at the surface, which is mainly controlled by the albedo of snow and ice. Here, using an Earth system model of intermediate complexity, we explore the role played by surface albedo for the simulation of glacial cycles. We show that the evolution of the Northern Hemisphere ice sheets over the last glacial cycle is very sensitive to the representation of snow albedo in the model. It is well known that the albedo of snow depends strongly on the snow grain size and the content of light absorbing impurities. Excluding either the snow aging effect or the dust darkening effect on snow albedo leads to an excessive ice build-up during glacial times and consequently to a failure in simulating deglaciation. While the effect of snow grain growth on snow albedo is well constrained, the albedo reduction due to the presence of dust in snow is much more uncertain, because the light absorbing properties of dust vary widely as a function of dust composition. We also show that assuming slightly different optical properties of dust leads to very different ice sheet and climate evolutions in the model. Conversely, ice sheet evolution is less sensitive to the choice of ice albedo in the model. We conclude that a proper representation of snow albedo is a fundamental prerequisite for a successful simulation of glacial cycles.

  2. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Artic Sea Ice Cover

    Science.gov (United States)

    2015-11-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. SUNLIGHT, SEA ICE , AND THE ICE ALBEDO FEEDBACK IN A...iv) onset dates of melt and freeze up. 4. Assess the magnitude of the contribution from ice - albedo feedback to the observed decrease of sea ice in... sea ice prediction and modeling community to improve the treatment of solar radiation and the ice - albedo feedback. This transfer will take the form of

  3. Global Cooling: Effect of Urban Albedo on Global Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Hashem; Menon, Surabi; Rosenfeld, Arthur

    2007-05-22

    In many urban areas, pavements and roofs constitute over 60% of urban surfaces (roof 20-25%, pavements about 40%). The roof and the pavement albedo can be increased by about 0.25 and 0.10, respectively, resulting in a net albedo increase for urban areas of about 0.1. Many studies have demonstrated building cooling-energy savings in excess of 20% upon raising roof reflectivity from an existing 10-20% to about 60%. We estimate U.S. potential savings in excess of $1 billion (B) per year in net annual energy bills. Increasing albedo of urban surfaces can reduce the summertime urban temperature and improve the urban air quality. Increasing the urban albedo has the added benefit of reflecting more of the incoming global solar radiation and countering the effect of global warming. We estimate that increasing albedo of urban areas by 0.1 results in an increase of 3 x 10{sup -4} in Earth albedo. Using a simple global model, the change in air temperature in lowest 1.8 km of the atmosphere is estimated at 0.01K. Modelers predict a warming of about 3K in the next 60 years (0.05K/year). Change of 0.1 in urban albedo will result in 0.01K global cooling, a delay of {approx}0.2 years in global warming. This 0.2 years delay in global warming is equivalent to 10 Gt reduction in CO2 emissions.

  4. Career and Workforce Impacts of the NASA Planetary Science Summer School: TEAM X model 1999-2015

    Science.gov (United States)

    Lowes, Leslie L.; Budney, Charles; Mitchell, Karl; Wessen, Alice; JPL Education Office, JPL Team X

    2016-10-01

    Sponsored by NASA's Planetary Science Division, and managed by the Jet Propulsion Laboratory (JPL), the Planetary Science Summer School prepares the next generation of engineers and scientists to participate in future solar system exploration missions. PSSS utilizes JPL's emerging concurrent mission design "Team X" as mentors. With this model, participants learn the mission life cycle, roles of scientists and engineers in a mission environment, mission design interconnectedness and trade-offs, and the importance of teamwork. Applicants are sought who have a strong interest and experience in careers in planetary exploration, and who are science and engineering post-docs, recent PhDs, doctoral or graduate students, and faculty teaching such students. An overview of the program will be presented, along with results of a diversity study conducted in fall 2015 to assess the gender and ethnic diversity of participants since 1999. PSSS seeks to have a positive influence on participants' career choice and career progress, and to help feed the employment pipeline for NASA, aerospace, and related academia. Results will also be presented of an online search that located alumni in fall 2015 related to their current occupations (primarily through LinkedIn and university and corporate websites), as well as a 2015 survey of alumni.

  5. Sulfur dioxide estimations in the planetary boundary layer using dispersion models and satellite retrievals

    Science.gov (United States)

    Zarauz, Jorge V.

    The health and environmental conditions in the Central Andes city La Oroya, Peru, have been seriously damaged by the heavy metal mining activities in the region. The situation has been exacerbated by the complex topography, which prevents proper mixing and dissolution of particles and gases released into the atmosphere. Understanding how pollutants are dispersed in populated regions, especially in complex terrain, would help to create mitigation strategies. The present study uses CALPUFF and HYSPLIT dispersion/deposition models to estimate sulfur dioxide (SO2) dispersion from the main stack of the La Oroya metallurgical plant. Due to the lack of meteorological data in the area, the Weather Research and Forecasting model (WRF) is used with observational nudging for temperature, relative humidity, and wind fields of three surface meteorological stations specifically installed for the study. The pollutant dispersion models are sensitive to a precise estimation of the turbulent vertical transport of mass, energy and moisture in the low atmosphere; therefore, two planetary boundary layer (PBL) schemes are tested, the Mellor-Yamada-Janjic and Yonsei University models. The dispersion models are run and results compared with field measurements at La Oroya, and Huancayo. The observation-nudging and YSU scheme considerably improved the prognostic variables. CALPUFF and HYSPLIT models showed similar patterns; however, HYSPLIT overestimated SO2 concentrations for low PBLs. Moreover, recent enhancements on spectral, spatial and temporal resolution of atmospheric scanning sensors of chemical constituents from the space, have led to detecting trace gases of anthropogenic origin in the lower troposphere. This contribution also explores the SO2 level 2 dataset from Ozone Mapping Instrument (OMI), in conjunction with atmospheric optical depth and Angstrom coefficient data products, extracted from MODerate Resolution Imaging Spectroradiometer (MODIS) to estimate SO2 loads in the PBL

  6. Summertime canopy albedo is sensitive to forest thinning

    NARCIS (Netherlands)

    Otto, J.; Berveiller, D.; Bréon, F.M.; Delpierre, N.; Geppert, G.; Granier, A.; Jans, W.W.P.; Knohl, A.; Moors, E.J.

    2013-01-01

    Despite an emerging body of literature linking canopy albedo to forest management, understanding of the process is still fragmented. We combined a stand-level forest gap model with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning,

  7. Competing effects of surface albedo and orographic elevated heating on regional climate

    Science.gov (United States)

    Hu, Shineng; Boos, William R.

    2017-07-01

    All else being equal, a given atmospheric pressure level is thought to be warmer over a plateau than over surrounding nonelevated terrain because of orographic "elevated heating." However, elevated surfaces are also typically brighter due to reduced vegetation and increased ice cover. Here we assess the degree to which surface albedo compensates for orographic elevated heating. We confirm that land surface albedo generally increases with surface elevation in observations. Using a cloud system-resolving model, we show that increased surface albedo strongly compensates for orographic elevated heating in radiative-convective equilibrium. A nonelevated surface with the albedo of modern India would enter a runaway greenhouse regime without ventilation by monsoonal winds, while a surface with the albedo and elevation of Tibet would achieve a cooler radiative-convective equilibrium. Surface albedo changes may thus be just as important as surface elevation changes for the evolution of low-latitude regional climate throughout Earth's history.

  8. Evaluating winds and vertical wind shear from Weather Research and Forecasting model forecasts using seven planetary boundary layer schemes

    DEFF Research Database (Denmark)

    Draxl, Caroline; Hahmann, Andrea N.; Pena Diaz, Alfredo

    2014-01-01

    with different PBL parameterizations at one coastal site over western Denmark. The evaluation focuses on determining which PBL parameterization performs best for wind energy forecasting, and presenting a validation methodology that takes into account wind speed at different heights. Winds speeds at heights...... regarding wind energy at these levels partly depends on the formulation and implementation of planetary boundary layer (PBL) parameterizations in these models. This study evaluates wind speeds and vertical wind shears simulated by theWeather Research and Forecasting model using seven sets of simulations...

  9. Planetary Magnetism

    International Nuclear Information System (INIS)

    Russell, C.T.

    1980-01-01

    Planetary spacecraft have now probed the magnetic fields of all the terrestrial planets, the moon, Jupiter, and Saturn. These measurements reveal that dynamos are active in at least four of the planets, Mercury, the earth, Jupiter, and Saturn but that Venus and Mars appear to have at most only very weak planetary magnetic fields. The moon may have once possessed an internal dynamo, for the surface rocks are magnetized. The large satellites of the outer solar system are candidates for dynamo action in addition to the large planets themselves. Of these satellites the one most likely to generate its own internal magnetic field is Io

  10. Conjecture on superrotation in planetary atmospheres - A diffusion model with mixing length theory

    Science.gov (United States)

    Mayr, H. G.; Harris, I.; Hartle, R. E.; Schatten, K. H.; Chan, K. L.

    1985-01-01

    The component of rigid shell superrotation on Venus is discussed in the context of comparative planetary atmospheres. A simplified, heuristic analysis, utilizing mixed length theory to describe the small scale nonlinear advections of energy and angular momentum, thereby providing a closure of the dynamic system, is presented, on the basis of which a crude estimate of zonal velocity is made. The rigid shell (global average) component on Venus was calculated to be 105 m/sec.

  11. Coherent Backscattering by Particulate Planetary Media of Nonspherical Particles

    Science.gov (United States)

    Muinonen, Karri; Penttila, Antti; Wilkman, Olli; Videen, Gorden

    2014-11-01

    The so-called radiative-transfer coherent-backscattering method (RT-CB) has been put forward as a practical Monte Carlo method to compute multiple scattering in discrete random media mimicking planetary regoliths (K. Muinonen, Waves in Random Media 14, p. 365, 2004). In RT-CB, the interaction between the discrete scatterers takes place in the far-field approximation and the wave propagation faces exponential extinction. There is a significant constraint in the RT-CB method: it has to be assumed that the form of the scattering matrix is that of the spherical particle. We aim to extend the RT-CB method to nonspherical single particles showing significant depolarization characteristics. First, ensemble-averaged single-scattering albedos and phase matrices of nonspherical particles are matched using a phenomenological radiative-transfer model within a microscopic volume element. Second, the phenomenologial single-particle model is incorporated into the Monte Carlo RT-CB method. In the ray tracing, the electromagnetic phases within the microscopic volume elements are omitted as having negligible lengths, whereas the phases are duly accounted for in the paths between two or more microscopic volume elements. We assess the computational feasibility of the extended RT-CB method and show preliminary results for particulate media mimicking planetary regoliths. The present work can be utilized in the interpretation of astronomical observations of asteroids and other planetary objects. In particular, the work sheds light on the depolarization characteristics of planetary regoliths at small phase angles near opposition. The research has been partially funded by the ERC Advanced Grant No 320773 entitled “Scattering and Absorption of Electromagnetic Waves in Particulate Media” (SAEMPL), by the Academy of Finland (contract 257966), NASA Outer Planets Research Program (contract NNX10AP93G), and NASA Lunar Advanced Science and Exploration Research Program (contract NNX11AB25G).

  12. Relating black carbon content to reduction of snow albedo

    Science.gov (United States)

    Brandt, R. E.; Warren, S. G.; Clarke, A. D.

    2011-12-01

    In remote snow of the Northern Hemisphere, the levels of soot pollution are in the parts-per-billion (ppb) range, where the effect on albedo is at the level of a few percent. A reduction of albedo by 1-2% is significant for climate but is difficult to detect experimentally, because snow albedo depends on several other variables. In our work to quantify the climatic effect of black carbon (BC) in snow, we therefore do not directly measure the albedo reduction. Instead, we use a two-step procedure: (1) We collect snow samples, melt and filter them, and analyze the filters spectrophotometrically for BC concentration. (2) We use the BC amount from the filter measurement, together with snow grain size, in a radiative transfer model to compute the albedo reduction. Our radiative transfer model uses the discrete ordinates algorithm DISORT 2.0. We have chosen a representative BC size distribution and optical constants, and have incorporated those of mineral dust as well. While a given mass of BC causes over an order of magnitude more snow albedo reduction compared to dust, a snowpack containing dust mutes the albedo-reducing effect of BC. Because the computed reduction of snow albedo is model-based, it requires experimental verification. We doubt that direct measurement of albedo-reduction will be feasible in nature, because of the vertical variation of both snow grain size and soot content, and because the natural soot content is small. We conclude that what is needed is an artificial snowpack, with uniform grain size and large uniform soot content (ppm not ppb), to produce a large signal on albedo. We have chosen to pursue this experiment outdoors rather than in the laboratory, for the following reasons: (1) The snowpack in the field of view is uniformly illuminated if the source of radiation is the Sun. (2) Visible radiation penetrates into the snow, so photons emerge horizontally distant from where they entered. In the limited width of a laboratory snowpack, radiation

  13. The retrieval of land surface albedo in rugged terrain

    NARCIS (Netherlands)

    Gao, B.; Jia, L.; Menenti, M.

    2012-01-01

    Land surface albedo may be derived from the satellite data through the estimation of a bidirectional reflectance distribution function (BRDF) model and angular integration. However many BRDF models do not consider explicitly the topography. In rugged terrain, the topography influences the observed

  14. The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets

    Science.gov (United States)

    Meadows, Victoria S.; Bitz, Cecilia M.; Pierrehumbert, Raymond T.; Joshi, Manoj M.; Robinson, Tyler D.

    2013-01-01

    Abstract Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO2 (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO2 in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global

  15. Matrix albedo for discrete ordinates infinite-medium boundary condition

    International Nuclear Information System (INIS)

    Mathews, K.; Dishaw, J.

    2007-01-01

    Discrete ordinates problems with an infinite exterior medium (reflector) can be more efficiently computed by eliminating grid cells in the exterior medium and applying a matrix albedo boundary condition. The albedo matrix is a discretized bidirectional reflection distribution function (BRDF) that accounts for the angular quadrature set, spatial quadrature method, and spatial grid that would have been used to model a portion of the exterior medium. The method is exact in slab geometry, and could be used as an approximation in multiple dimensions or curvilinear coordinates. We present an adequate method for computing albedo matrices and demonstrate their use in verifying a discrete ordinates code in slab geometry by comparison with Ganapol's infinite medium semi-analytic TIEL benchmark. With sufficient resolution in the spatial and angular grids and iteration tolerance to yield solutions converged to 6 digits, the conventional (scalar) albedo boundary condition yielded 2-digit accuracy at the boundary, but the matrix albedo solution reproduced the benchmark scalar flux at the boundary to all 6 digits. (authors)

  16. Theory of extended stellar atmospheres. II. A grid of static spherical models for O stars and planetary nebula nuclei

    International Nuclear Information System (INIS)

    Kunasz, P.B.; Hummer, D.G.; Mihalas, D.

    1975-01-01

    Spherical static non-LTE model atmospheres are presented for stars with M/M/sub sun/=30 and 60 at various points on their evolutionary tracks, and for some nuclei of planetary nebulae at two points of a modified Harman-Seaton sequence. The method of Mihalas and Hummer was employed, which uses a parametrized radiation force multiplier to simulate the force of radiation arising from the entire line spectrum. However, in the present work the density structure computed in the LTE models was held fixed in the calculation of the corresponding non-LTE models; in addition, the opacity of an ''average light ion'' was taken into account. The temperatures for the non-LTE models are generally lower, at a given depth, than for the corresponding LTE models when T/sub eff/<45,000 K, while the situation is reversed at higher temperatures. The continuous energy distributions are generally flattened by extension. The Lyman jump is in emission for extended models of massive stars, but never for the models of nuclei of planetary nebulae (this is primarily a temperature effect). The Balmer jumps are always in absorption. The Lyman lines are in emission, and the Balmer lines in absorption; He ii lambda4686 comes into emission in the most extended models without hydrogen line pumping, showing that it is an indicator of atmospheric extension. Very severe limb darkening is found for extended models, which have apparent angular sized significantly smaller than expected from the geometrical size of the star. Extensive tables are given of monochromatic magnitudes, continuum jumps and gradients, Stomgren-system colors, monochromatic extensions, and the profiles and equivalent widths of the hydrogen lines for all models, and of the He ii lines for some of the 60 M/sub X/ models

  17. Albedo enhancement of marine clouds to counteract global warming: impacts on the hydrological cycle

    Energy Technology Data Exchange (ETDEWEB)

    Bala, G. [Indian Institute of Science, Divecha Center for Climate Change, Bangalore (India); Indian Institute of Science, Center for Atmospheric and Oceanic Sciences, Bangalore (India); Caldeira, Ken; Cao, Long; Ban-Weiss, George; Shin, Ho-Jeong [Carnegie Institution, Department of Global Ecology, Stanford, CA (United States); Nemani, Rama [NASA Ames Research Center, Moffett Field, CA (United States)

    2011-09-15

    Recent studies have shown that changes in solar radiation affect the hydrological cycle more strongly than equivalent CO{sub 2} changes for the same change in global mean surface temperature. Thus, solar radiation management ''geoengineering'' proposals to completely offset global mean temperature increases by reducing the amount of absorbed sunlight might be expected to slow the global water cycle and reduce runoff over land. However, proposed countering of global warming by increasing the albedo of marine clouds would reduce surface solar radiation only over the oceans. Here, for an idealized scenario, we analyze the response of temperature and the hydrological cycle to increased reflection by clouds over the ocean using an atmospheric general circulation model coupled to a mixed layer ocean model. When cloud droplets are reduced in size over all oceans uniformly to offset the temperature increase from a doubling of atmospheric CO{sub 2}, the global-mean precipitation and evaporation decreases by about 1.3% but runoff over land increases by 7.5% primarily due to increases over tropical land. In the model, more reflective marine clouds cool the atmospheric column over ocean. The result is a sinking motion over oceans and upward motion over land. We attribute the increased runoff over land to this increased upward motion over land when marine clouds are made more reflective. Our results suggest that, in contrast to other proposals to increase planetary albedo, offsetting mean global warming by reducing marine cloud droplet size does not necessarily lead to a drying, on average, of the continents. However, we note that the changes in precipitation, evaporation and P-E are dominated by small but significant areas, and given the highly idealized nature of this study, a more thorough and broader assessment would be required for proposals of altering marine cloud properties on a large scale. (orig.)

  18. Higher albedos and size distribution of large transneptunian objects

    Science.gov (United States)

    Lykawka, Patryk Sofia; Mukai, Tadashi

    2005-11-01

    Transneptunian objects (TNOs) orbit beyond Neptune and do offer important clues about the formation of our solar system. Although observations have been increasing the number of discovered TNOs and improving their orbital elements, very little is known about elementary physical properties such as sizes, albedos and compositions. Due to TNOs large distances (>40 AU) and observational limitations, reliable physical information can be obtained only from brighter objects (supposedly larger bodies). According to size and albedo measurements available, it is evident the traditionally assumed albedo p=0.04 cannot hold for all TNOs, especially those with approximately absolute magnitudes H⩽5.5. That is, the largest TNOs possess higher albedos (generally >0.04) that strongly appear to increase as a function of size. Using a compilation of published data, we derived empirical relations which can provide estimations of diameters and albedos as a function of absolute magnitude. Calculations result in more accurate size/albedo estimations for TNOs with H⩽5.5 than just assuming p=0.04. Nevertheless, considering low statistics, the value p=0.04 sounds still convenient for H>5.5 non-binary TNOs as a group. We also discuss about physical processes (e.g., collisions, intrinsic activity and the presence of tenuous atmospheres) responsible for the increase of albedo among large bodies. Currently, all big TNOs (>700 km) would be capable to sustain thin atmospheres or icy frosts composed of CH 4, CO or N 2 even for body bulk densities as low as 0.5 g cm -3. A size-dependent albedo has important consequences for the TNOs size distribution, cumulative luminosity function and total mass estimations. According to our analysis, the latter can be reduced up to 50% if higher albedos are common among large bodies. Lastly, by analyzing orbital properties of classical TNOs ( 42AUbodies. For both populations, distinct absolute magnitude distributions are maximized for an inclination threshold

  19. Planetary Rings

    Science.gov (United States)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of

  20. MODIS/Terra+Aqua BRDF/Albedo Parameter1 Band6 Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D16 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameter data set is a daily 16-day product. This product...

  1. MODIS/Terra+Aqua BRDF/Albedo Parameter2 Band7 Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D20 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameter data set is a daily 16-day product. This product...

  2. MODIS/Terra+Aqua BRDF/Albedo Parameter1 VIS Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D22 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameter data set is a daily 16-day product. This product...

  3. MODIS/Terra+Aqua BRDF/Albedo Parameter1 Band2 Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D04 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameter data set is a daily 16-day product. This product...

  4. Validation of response simulation methodology of Albedo dosemeter

    International Nuclear Information System (INIS)

    Freitas, B.M.; Silva, A.X. da

    2016-01-01

    The Instituto de Radioprotecao e Dosimetria developed and runs a neutron TLD albedo individual monitoring service. To optimize the dose calculation algorithm and to infer new calibration factors, the response of this dosemeter was simulated. In order to validate this employed methodology, it was applied in the simulation of the problem of the QUADOS (Quality Assurance of Computational Tools for Dosimetry) intercomparison, aimed to evaluate dosimetric problems, one being to calculate the response of a generic albedo dosemeter. The obtained results were compared with those of other modeling and the reference one, with good agreements. (author)

  5. Ceres Photometry and Albedo from Dawn Framing Camera Images

    Science.gov (United States)

    Schröder, S. E.; Mottola, S.; Keller, H. U.; Li, J.-Y.; Matz, K.-D.; Otto, K.; Roatsch, T.; Stephan, K.; Raymond, C. A.; Russell, C. T.

    2015-10-01

    The Dawn spacecraft is in orbit around dwarf planet Ceres. The onboard Framing Camera (FC) [1] is mapping the surface through a clear filter and 7 narrow-band filters at various observational geometries. Generally, Ceres' appearance in these images is affected by shadows and shading, effects which become stronger for larger solar phase angles, obscuring the intrinsic reflective properties of the surface. By means of photometric modeling we attempt to remove these effects and reconstruct the surface albedo over the full visible wavelength range. Knowledge of the albedo distribution will contribute to our understanding of the physical nature and composition of the surface.

  6. Planetary Society

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    Carl Sagan, Bruce Murray and Louis Friedman founded the non-profit Planetary Society in 1979 to advance the exploration of the solar system and to continue the search for extraterrestrial life. The Society has its headquarters in Pasadena, California, but is international in scope, with 100 000 members worldwide, making it the largest space interest group in the world. The Society funds a var...

  7. Planetary atomspheres

    International Nuclear Information System (INIS)

    Lal, D.; Rao, M.N.

    1986-01-01

    Salient features of the atmosheres of Venus and Mars are described and compared with those of the earth. Their temperature profiles are given. Degassing of planetary interiors by volcanic and plate tectonic processes is described. Noble gas abundances in the atmospheres of these planets are compared. Information provided by Pioneer, Venera space probes and the Viking-landers on Mars is studied. (B.G.W.)

  8. Albedos

    Science.gov (United States)

    1993-07-01

    Maize 18 Spring wheat 10 - 25 Wheat 18 Swamp rice 11 Tobacco 19 Paddy rice 12 Cassava 19 Kola nuts 13 Potatos 19 Stubble fields 15 - 17 Yams 19 Sugar...441. Perevertun, M. P., 1957, "Spectral Reflectance of Certain Plants in the Range 650-1200 jm," Trans Asrobotan Sect Acad Sci Kazahk SSR, 5. Posey...Barnes) ATTN: AMSMI-RD-DE-SE Fort McClellan, AL 36205-5020 Gordon Lill, Jr. Redstone Arsenal, AL 35898-5245 NASA/Marshall Space Flight Center Deputy

  9. Planetary engineering

    Science.gov (United States)

    Pollack, James B.; Sagan, Carl

    1991-01-01

    Assuming commercial fusion power, heavy lift vehicles and major advances in genetic engineering, the authors survey possible late-21st century methods of working major transformations in planetary environments. Much more Earthlike climates may be produced on Mars by generating low freezing point greenhouse gases from indigenous materials; on Venus by biological conversion of CO2 to graphite, by canceling the greenhouse effect with high-altitude absorbing fine particles, or by a sunshield at the first Lagrangian point; and on Titan by greenhouses and/or fusion warming. However, in our present state of ignorance we cannot guarantee a stable endstate or exclude unanticipated climatic feedbacks or other unintended consequences. Moreover, as the authors illustrate by several examples, many conceivable modes of planetary engineering are so wasteful of scarce solar system resources and so destructive of important scientific information as to raise profound ethical issues, even if they were economically feasible, which they are not. Global warming on Earth may lead to calls for mitigation by planetary engineering, e.g., emplacement and replenishment of anti-greenhouse layers at high altitudes, or sunshields in space. But here especially we must be concerned about precision, stability, and inadvertent side-effects. The safest and most cost-effective means of countering global warming - beyond, e.g., improved energy efficiency, CFC bans and alternative energy sources - is the continuing reforestation of approximately 2 times 107 sq km of the Earth's surface. This can be accomplished with present technology and probably at the least cost.

  10. Planetary engineering

    Science.gov (United States)

    Pollack, James B.; Sagan, Carl

    Assuming commercial fusion power, heavy lift vehicles and major advances in genetic engineering, the authors survey possible late-21st century methods of working major transformations in planetary environments. Much more Earthlike climates may be produced on Mars by generating low freezing point greenhouse gases from indigenous materials; on Venus by biological conversion of CO2 to graphite, by canceling the greenhouse effect with high-altitude absorbing fine particles, or by a sunshield at the first Lagrangian point; and on Titan by greenhouses and/or fusion warming. However, in our present state of ignorance we cannot guarantee a stable endstate or exclude unanticipated climatic feedbacks or other unintended consequences. Moreover, as the authors illustrate by several examples, many conceivable modes of planetary engineering are so wasteful of scarce solar system resources and so destructive of important scientific information as to raise profound ethical issues, even if they were economically feasible, which they are not. Global warming on Earth may lead to calls for mitigation by planetary engineering, e.g., emplacement and replenishment of anti-greenhouse layers at high altitudes, or sunshields in space. But here especially we must be concerned about precision, stability, and inadvertent side-effects. The safest and most cost-effective means of countering global warming - beyond, e.g., improved energy efficiency, CFC bans and alternative energy sources - is the continuing reforestation of approximately 2 times 107 sq km of the Earth's surface. This can be accomplished with present technology and probably at the least cost.

  11. Neutron albedo effects of underground nuclear explosion

    International Nuclear Information System (INIS)

    Yang Bo; Ying Yangjun; Li Jinhong; Bai Yun

    2013-01-01

    The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device.The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device. (authors)

  12. Simulation and Analysis of Topographic Effect on Land Surface Albedo over Mountainous Areas

    Science.gov (United States)

    Hao, D.; Wen, J.; Xiao, Q.

    2017-12-01

    Land surface albedo is one of the significant geophysical variables affecting the Earth's climate and controlling the surface radiation budget. Topography leads to the formation of shadows and the redistribution of incident radiation, which complicates the modeling and estimation of the land surface albedo. Some studies show that neglecting the topography effect may lead to significant bias in estimating the land surface albedo for the sloping terrain. However, for the composite sloping terrain, the topographic effects on the albedo remain unclear. Accurately estimating the sub-topographic effect on the land surface albedo over the composite sloping terrain presents a challenge for remote sensing modeling and applications. In our study, we focus on the development of a simplified estimation method for land surface albedo including black-sky albedo (BSA) and white-sky albedo (WSA) of the composite sloping terrain at a kilometer scale based on the fine scale DEM (30m) and quantitatively investigate and understand the topographic effects on the albedo. The albedo is affected by various factors such as solar zenith angle (SZA), solar azimuth angle (SAA), shadows, terrain occlusion, and slope and aspect distribution of the micro-slopes. When SZA is 30°, the absolute and relative deviations between the BSA of flat terrain and that of rugged terrain reaches 0.12 and 50%, respectively. When the mean slope of the terrain is 30.63° and SZA=30°, the absolute deviation of BSA caused by SAA can reach 0.04. The maximal relative and relative deviation between the WSA of flat terrain and that of rugged terrain reaches 0.08 and 50%. These results demonstrate that the topographic effect has to be taken into account in the albedo estimation.

  13. Gazetteer of planetary nomenclature 1994

    Science.gov (United States)

    Batson, Raymond M.; Russell, Joel F.

    1995-01-01

    Planetary nomenclature, like terrestrial nomenclature, is used to uniquely identify a feature on the surface of a planet or satellite so that the feature can be easily located, described, and discussed. This volume contains detailed information about all names of topographic and albedo features on planets and satellites (and some planetary ring and ring-gap systems) that the International Astronomical Union has named and approved from its founding in 1919 through its triennial meeting in 1994.This edition of the Gazetteer of Planetary Nomenclature supersedes an earlier informal volume distributed by the U.S. Geological Survey in 1986 as Open-File Report 84-692 (Masursky and others, 1986). Named features are depicted on maps of the Moon published first by the U.S. Defense Mapping Agency or the Aeronautical Chart and Information Center and more recently by the U.S. Geological Survey; on maps of Mercury, Venus, Mars, and the satellites of Jupiter, Saturn, and Uranus published by the U.S. Geological Survey; and on maps of the Moon, Venus, and Mars produced by the U.S.S.R.Although we have attempted to check the accuracy of all data in this volume, we realize that some errors will remain in a work of this size. Readers noting errors or omissions are urged to communicate them to the U.S. Geological Survey, Branch of Astrogeology, Rm. 409, 2255 N. Gemini Drive, Flagstaff, AZ 86001.

  14. The Ultraviolet Albedo of Ganymede

    Science.gov (United States)

    McGrath, Melissa; Hendrix, A.

    2013-10-01

    A large set of ultraviolet images of Ganymede have been acquired with the Hubble Space Telescope over the last 15 years. These images have been used almost exclusively to study Ganymede’s stunning auroral emissions (Feldman et al. 2000; Eviatar et al. 2001; McGrath et al. 2004; Saur et al. 2011; McGrath et al. 2013), and even the most basic information about Ganymede’s UV albedo has yet to be gleaned from these data. We will present a first-cut analysis of both disk-averaged and spatially-resolved UV albedos of Ganymede, with focus on the spatially-resolved Lyman-alpha albedo, which has never been considered previously for this satellite. Ganymede's visibly bright regions are known to be rich in water ice, while the visibly dark regions seem to be more carbonaceous (Carlson et al., 1996). At Lyman-alpha, these two species should also have very different albedo values. References Carlson, R. and 39 co-authors, Near-infrared spectroscopy and spectral mapping of Jupiter and the Galilean satellites: Results from Galileo’s initial orbit, Science, 274, 385-388, 1996. Eviatar, A., D. F. Strobel, B. C. Wolven, P. D. Feldman, M. A. McGrath, and D. J. Williams, Excitation of the Ganymede ultraviolet aurora, Astrophys. J, 555, 1013-1019, 2001. Feldman, P. D., M. A. McGrath, D. F. Strobel, H. W. Moos, K. D. Retherford, and B. C. Wolven, HST/STIS imaging of ultraviolet aurora on Ganymede, Astrophys. J, 535, 1085-1090, 2000. McGrath M. A., Lellouch E., Strobel D. F., Feldman P. D., Johnson R. E., Satellite Atmospheres, Chapter 19 in Jupiter: The Planet, Satellites and Magnetosphere, ed. F. Bagenal, T. Dowling, W. McKinnon, Cambridge University Press, 2004. McGrath M. A., Jia, Xianzhe; Retherford, Kurt; Feldman, Paul D.; Strobel, Darrell F.; Saur, Joachim, Aurora on Ganymede, J. Geophys. Res., doi: 10.1002/jgra.50122, 2013. Saur, J., S. Duling, S., L. Roth, P. D. Feldman, D. F. Strobel, K. D. Retherford, M. A. McGrath, A. Wennmacher, American Geophysical Union, Fall Meeting

  15. Validation of response simulation methodology of Albedo dosemeter; Validacao da metodologia de simulacao de resposta de dosimetro de Albedo

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, B.M.; Silva, A.X. da, E-mail: bfreitas@nuclear.ufrj.br [Coordenacao do Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Mauricio, C.L.P. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2016-07-01

    The Instituto de Radioprotecao e Dosimetria developed and runs a neutron TLD albedo individual monitoring service. To optimize the dose calculation algorithm and to infer new calibration factors, the response of this dosemeter was simulated. In order to validate this employed methodology, it was applied in the simulation of the problem of the QUADOS (Quality Assurance of Computational Tools for Dosimetry) intercomparison, aimed to evaluate dosimetric problems, one being to calculate the response of a generic albedo dosemeter. The obtained results were compared with those of other modeling and the reference one, with good agreements. (author)

  16. CARP: a computer code and albedo data library for use by BREESE, the MORSE albedo package

    International Nuclear Information System (INIS)

    Emmett, M.B.; Rhoades, W.A.

    1978-10-01

    The CARP computer code was written to allow processing of DOT angular flux tapes to produce albedo data for use in the MORSE computer code. An albedo data library was produced containing several materials. 3 tables

  17. Diurnal variations in the UV albedo of arctic snow

    Directory of Open Access Journals (Sweden)

    O. Meinander

    2008-11-01

    Full Text Available The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67°22'N, 26°39'E, 179 m a.s.l. during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0°C on the following mornings. Hence, the reversible diurnal change, evident for ~1–2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

  18. Geodynamic Modeling of Planetary Ice-Oceans: Evolution of Ice-Shell Thickness in Convecting Two-Phase Systems

    Science.gov (United States)

    Allu Peddinti, D.; McNamara, A. K.

    2016-12-01

    Along with the newly unveiled icy surface of Pluto, several icy planetary bodies show indications of an active surface perhaps underlain by liquid oceans of some size. This augments the interest to explore the evolution of an ice-ocean system and its surface implications. The geologically young surface of the Jovian moon Europa lends much speculation to variations in ice-shell thickness over time. Along with the observed surface features, it suggests the possibility of episodic convection and conduction within the ice-shell as it evolved. What factors would control the growth of the ice-shell as it forms? If and how would those factors determine the thickness of the ice-shell and consequently the heat transfer? Would parameters such as tidal heating or initial temperature affect how the ice-shell grows and to what significance? We perform numerical experiments using geodynamical models of the two-phase ice-water system to study the evolution of planetary ice-oceans such as that of Europa. The models evolve self-consistently from an initial liquid ocean as it cools with time. The effects of presence, absence and magnitude of tidal heating on ice-shell thickness are studied in different models. The vigor of convection changes as the ice-shell continues to thicken. Initial modeling results track changes in the growth rate of the ice-shell as the vigor of the convection changes. The magnitude and temporal location of the rate change varies with different properties of tidal heating and values of initial temperature. A comparative study of models is presented to demonstrate how as the ice-shell is forming, its growth rate and convection are affected by processes such as tidal heating.

  19. MODIS/Terra+Aqua BRDF/Albedo Albedo Daily L3 Global 0.05Deg CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODIS MCD43C3 Version 6 Albedo Model data set is a 5600 meter daily 16-day product. The Julian date in the granule ID of each specific file represents the 9th...

  20. Mathematical Modeling of Electrodynamics Near the Surface of Earth and Planetary Water Worlds

    Science.gov (United States)

    Tyler, Robert H.

    2017-01-01

    An interesting feature of planetary bodies with hydrospheres is the presence of an electrically conducting shell near the global surface. This conducting shell may typically lie between relatively insulating rock, ice, or atmosphere, creating a strong constraint on the flow of large-scale electric currents. All or parts of the shell may be in fluid motion relative to main components of the rotating planetary magnetic field (as well as the magnetic fields due to external bodies), creating motionally-induced electric currents that would not otherwise be present. As such, one may expect distinguishing features in the types of electrodynamic processes that occur, as well as an opportunity for imposing specialized mathematical methods that efficiently address this class of application. The purpose of this paper is to present and discuss such specialized methods. Specifically, thin-shell approximations for both the electrodynamics and fluid dynamics are combined to derive simplified mathematical formulations describing the behavior of these electric currents as well as their associated electric and magnetic fields. These simplified formulae allow analytical solutions featuring distinct aspects of the thin-shell electrodynamics in idealized cases. A highly efficient numerical method is also presented that is useful for calculations under inhomogeneous parameter distributions. Finally, the advantages as well as limitations in using this mathematical approach are evaluated. This evaluation is presented primarily for the generic case of bodies with water worlds or other thin spherical conducting shells. More specific discussion is given for the case of Earth, but also Europa and other satellites with suspected oceans.

  1. Albedo Spatial Variability and Causes on the Western Greenland Ice Sheet Percolation Zone

    Science.gov (United States)

    Lewis, G.; Osterberg, E. C.; Hawley, R. L.; Koffman, B. G.; Marshall, H. P.; Birkel, S. D.; Dibb, J. E.

    2016-12-01

    Many recent studies have concluded that Greenland Ice Sheet (GIS) mass loss has been accelerating over recent decades, but spatial and temporal variations in GIS mass balance remain poorly understood due to a complex relationship among precipitation and temperature changes, increasing melt and runoff, ice discharge, and surface albedo. Satellite measurements from MODerate resolution Imaging Spectroradiometer (MODIS) indicate that albedo has been declining over the past decade, but the cause and extent of GIS albedo change remains poorly constrained by field data. As fresh snow (albedo > 0.85) warms and melts, its albedo decreases due to snow grain growth, promoting solar absorption, higher snowpack temperatures and further melt. However, dark impurities like soot and dust can also significantly reduce snow albedo, even in the dry snow zone. While many regional climate models (e.g. the Regional Atmospheric Climate MOdel - RACMO2) calculate albedo spatial resolutions on the order of 10-30 km, and MODIS averages albedo over 500 m, surface features like sastrugi can affect albedo on much smaller scales. Here we assess the relative importance of grain size and shape vs. impurity concentrations on albedo in the western GIS percolation zone. We collected broadband albedo measurements (300-2500 nm at 3-8 nm resolution) at 35 locations using an ASD FieldSpec4 spectroradiometer to simultaneously quantify radiative fluxes and spectral reflectance. Measurements were collected on 10 x 10 m, 1 x 1 km, 5 x 5 km, and 10 x 10 km grids to determine the spatial variability of albedo as part of the 850-km Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) traverse from Raven/Dye 2 to Summit. Additionally, we collected shallow (0-50 cm) snow pit samples every 5 cm at ASD measurement sites to quantify black carbon and mineral dust concentrations and size distributions using a Single Particle Soot Photometer and Coulter Counter, respectively. Preliminary results

  2. Dominance of grain size impacts on seasonal snow albedo at open sites in New Hampshire

    Science.gov (United States)

    Adolph, Alden C.; Albert, Mary R.; Lazarcik, James; Dibb, Jack E.; Amante, Jacqueline M.; Price, Andrea

    2017-01-01

    Snow cover serves as a major control on the surface energy budget in temperate regions due to its high reflectivity compared to underlying surfaces. Winter in the northeastern United States has changed over the last several decades, resulting in shallower snowpacks, fewer days of snow cover, and increasing precipitation falling as rain in the winter. As these climatic changes occur, it is imperative that we understand current controls on the evolution of seasonal snow albedo in the region. Over three winter seasons between 2013 and 2015, snow characterization measurements were made at three open sites across New Hampshire. These near-daily measurements include spectral albedo, snow optical grain size determined through contact spectroscopy, snow depth, snow density, black carbon content, local meteorological parameters, and analysis of storm trajectories using the Hybrid Single-Particle Lagrangian Integrated Trajectory model. Using analysis of variance, we determine that land-based winter storms result in marginally higher albedo than coastal storms or storms from the Atlantic Ocean. Through multiple regression analysis, we determine that snow grain size is significantly more important in albedo reduction than black carbon content or snow density. And finally, we present a parameterization of albedo based on days since snowfall and temperature that accounts for 52% of variance in albedo over all three sites and years. Our improved understanding of current controls on snow albedo in the region will allow for better assessment of potential response of seasonal snow albedo and snow cover to changing climate.

  3. Planetary geology

    CERN Document Server

    Gasselt, Stephan

    2018-01-01

    This book provides an up-to-date interdisciplinary geoscience-focused overview of solid solar system bodies and their evolution, based on the comparative description of processes acting on them. Planetary research today is a strongly multidisciplinary endeavor with efforts coming from engineering and natural sciences. Key focal areas of study are the solid surfaces found in our Solar System. Some have a direct interaction with the interplanetary medium and others have dynamic atmospheres. In any of those cases, the geological records of those surfaces (and sub-surfaces) are key to understanding the Solar System as a whole: its evolution and the planetary perspective of our own planet. This book has a modular structure and is divided into 4 sections comprising 15 chapters in total. Each section builds upon the previous one but is also self-standing. The sections are:  Methods and tools Processes and Sources  Integration and Geological Syntheses Frontiers The latter covers the far-reaching broad topics of exo...

  4. Geodatabase model for global geologic mapping: concept and implementation in planetary sciences

    Science.gov (United States)

    Nass, Andrea

    2017-04-01

    One aim of the NASA Dawn mission is to generate global geologic maps of the asteroid Vesta and the dwarf planet Ceres. To accomplish this, the Dawn Science Team followed the technical recommendations for cartographic basemap production. The geological mapping campaign of Vesta was completed and published, but mapping of the dwarf planet Ceres is still ongoing. The tiling schema for the geological mapping is the same for both planetary bodies and for Ceres it is divided into two parts: four overview quadrangles (Survey Orbit, 415 m/pixel) and 15 more detailed quadrangles (High Altitude Mapping HAMO, 140 m/pixel). The first global geologic map was based on survey images (415 m/pixel). The combine 4 Survey quadrangles completed by HAMO data served as basis for generating a more detailed view of the geologic history and also for defining the chronostratigraphy and time scale of the dwarf planet. The most detailed view can be expected within the 15 mapping quadrangles based on HAMO resolution and completed by the Low Altitude Mapping (LAMO) data with 35 m/pixel. For the interpretative mapping process of each quadrangle one responsible mapper was assigned. Unifying the geological mapping of each quadrangle and bringing this together to regional and global valid statements is already a very time intensive task. However, another challenge that has to be accomplished is to consider how the 15 individual mappers can generate one homogenous GIS-based project (w.r.t. geometrical and visual character) thus produce a geologically-consistent final map. Our approach this challenge was already discussed for mapping of Vesta. To accommodate the map requirements regarding rules for data storage and database management, the computer-based GIS environment used for the interpretative mapping process must be designed in a way that it can be adjusted to the unique features of the individual investigation areas. Within this contribution the template will be presented that uses standards

  5. Albedo recovery for hyperspectral image classification

    Science.gov (United States)

    Zhan, Kun; Wang, Haibo; Xie, Yuange; Zhang, Chutong; Min, Yufang

    2017-07-01

    Image intensity value is determined by both the albedo component and the shading component. The albedo component describes the physical nature of different objects at the surface of the earth, and land-cover classes are different from each other because of their intrinsic physical materials. We, therefore, recover the intrinsic albedo feature of the hyperspectral image to exploit the spatial semantic information. Then, we use the support vector machine (SVM) to classify the recovered intrinsic albedo hyperspectral image. The SVM tries to maximize the minimum margin to achieve good generalization performance. Experimental results show that the SVM with the intrinsic albedo feature method achieves a better classification performance than the state-of-the-art methods in terms of visual quality and three quantitative metrics.

  6. Seasonal simulations of the planetary boundary layer and boundary-layer stratocumulus clouds with a general circulation model

    Science.gov (United States)

    Randall, D. A.; Abeles, J. A.; Corsetti, T. G.

    1985-01-01

    The formulation of the planetary boundary layer (PBL) and stratocumulus parametrizations in the UCLA general circulation model (GCM) are briefly summarized, and extensive new results are presented illustrating some aspects of the simulated seasonal changes of the global distributions of PBL depth, stratocumulus cloudiness, cloud-top entrainment instability, the cumulus mass flux, and related fields. Results from three experiments designed to reveal the sensitivity of the GCM results to aspects of the PBL and stratocumulus parametrizations are presented. The GCM results show that the layer cloud instability appears to limit the extent of the marine subtropical stratocumulus regimes, and that instability frequently occurs in association with cumulus convection over land. Cumulus convection acts as a very significant sink of PBL mass throughout the tropics and over the midlatitude continents in winter.

  7. The potential impacts of climate change induced changes to tropical leaf albedo and its feedback on global climate

    Science.gov (United States)

    Doughty, C.; Shenkin, A.; Bentley, L. P.; Malhi, Y.

    2017-12-01

    Tropical forest leaf albedo plays a critical role in global climate by determining how much radiation the planet absorbs near the equator. However, little is known about how tropical leaf albedo could be affected by climate change and how any such changes in albedo could, in turn, impact global climate. Here we measure sunlit leaf albedo along two elevation temperature gradients (a 3000-meter gradient in Peru (10 plots) and a 1500 m gradient in Australia (10 plots) and along two wet to dry transects (a 2000 mm yr-1 gradient in Ghana (10 plots) and a 2000 mm yr-1 gradient in Brazil (10 plots). We found a highly significant increase in visible leaf albedo with wetness at both wet to dry gradients. We also found a marginally significant trend of increased albedo with warmer temperatures along one of the elevation gradients. Leaf albedo can also be impacted by changes in species composition, variations in interspecific variation, and changes in leaf chlorophyll concentrations. We removed the dominant two species from the basal area weighting for each plots but found no significant change, a directional change of interspecific variation could change albedo by 0.01 in the NIR, and changes in chlorophyll could decrease visible albedo by 0.005. We then simulated changes in tropical leaf albedo with a climate model and show that such changes could act as a small negative feedback on climate, but most likely will not have a large impact on future climate.

  8. Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

    Science.gov (United States)

    Hayashi, Joan N.; Jakosky, Bruce M.; Haberle, Robert M.

    1995-01-01

    We examine the effects of a dusty C02 atmosphere on the thermal inertia and thermally derived albedo of Mars and we present a new map of thermal inertias. This new map was produced using a coupled surface atmosphere (CSA) model, dust opacities from Viking infrared thermal mapper (IRTM) data, and C02 columns based on topography. The CSA model thermal inertias are smaller than the 2% model thermal inertias, with the difference largest at large thermal inertia. Although the difference between the thermal inertias obtained with the two models is moderate for much of the region studied, it is largest in regions of either high dust opacity or of topographic lows, including the Viking Lander 1 site and some geologically interesting regions. The CSA model thermally derived albedos do not accurately predict the IRTM measured albedos and are very similar to the thermally derived albedos obtained with models making the 2% assumption.

  9. Surface albedo following biochar application in durum wheat

    International Nuclear Information System (INIS)

    Genesio, L; Miglietta, F; Lugato, E; Baronti, S; Pieri, M; Vaccari, F P

    2012-01-01

    The agronomic use of charcoal from biomass pyrolysis (biochar) represents an interesting option for increasing soil fertility and sequestering atmospheric CO 2 . However, before moving toward large-scale biochar applications, additional research must evaluate all possible land–atmosphere feedbacks. Despite the increasing number of studies investigating the effect of biochar on soil physical, chemical and biological properties, only a few have been done on surface albedo variations on agricultural lands. The present work had the aim of characterizing the annual albedo cycle for a durum wheat crop in Central Italy, by means of a spectroradiometer measurement campaign. Plots treated with biochar, at a rate of 30–60 t ha −1 , showed a surface albedo decrease of up to 80% (after the application) with respect to the control in bare soil conditions, while this difference tended to decrease during the crop growing season, because of the prevailing effect of canopy development on the radiometer response. After the post-harvesting tillage, the soil treated with biochar again showed a lower surface albedo value (<20–26% than the control), while the measurements taken in the second year after application suggested a clear decrease of biochar influence on soil color. The modeling of the surface energy balance highlighted changes in the partitioning of heat fluxes and in particular a substantial increase of ground heat fluxes on an annual basis. (letter)

  10. New high (> or =6M/sub sun/) upper mass limit for planetary nebula formation, and a new high lower mass bound for carbon detonation supernova models

    International Nuclear Information System (INIS)

    Tuchman, Y.; Sack, N.; Barkat, Z.

    1978-01-01

    Envelope ejection leading to a planetary nebula has been recently shown to occur as the terminal point of the Mira stage. The ejection is due to a diverging pulsational instability, not to a dynamical one. It is found that in this case (and for Population I, mixing length=1 pressure scale height) the upper mass limit for formation of planetary nebulae is at least 6 M/sub sun/. It thus follows that the lower mass limit for realization of carbon detonation model configurations is also at last 6 M/sub sun/

  11. Planetary compositions

    International Nuclear Information System (INIS)

    Taylor, S.R.

    1988-01-01

    The present study of the density, major-element and trace-element compositions, oxygen isotopes, and noble gases of the metal, sulfide, and silicate components of meteorites shows that these properties do not match those of the terrestrial planets, and thereby suggests that there was not much lateral mixing in the solar nebula during planetary accretion. The planets would then have accumulated from narrow concentric zones, and the current zonal structure of the asteroid belt may be analogous to the structure of the inner portions of the solar nebula during the terrestrial planets' accretion. Localized heating during the material's infall to the median plane of the nebula is suggested to have occurred. 64 references

  12. A note on solar elevation dependence of clear sky snow albedo

    Science.gov (United States)

    Choudhury, B. J.

    1981-01-01

    Recent attempts to match shortwave albedo of snow for clear skies using approximate spectral solar fluxes and solutions of the radiative transfer equation for snow were unsuccessful until a separate surface reflection term was introduced. A separate consideration of specular reflection from surface snow grains has been objected to as being ad hoc. Results based on a new parameterization of shortwave radiation are discussed. Compared to the previous radiation models, new model gives higher diffuse insolation and predicts higher albedos. The difference between observed and predicted albedos is substantially reduced without invoking surface reflection.

  13. Early Student Support to Investigate the Role of Sea Ice-Albedo Feedback in Sea Ice Predictions

    Science.gov (United States)

    2014-09-30

    Ice - Albedo Feedback in Sea Ice Predictions Cecilia M. Bitz Atmospheric Sciences MS351640 University of Washington Seattle, WA 98196-1640 phone...TERM GOALS The overarching goals of this project are to understand the role of sea ice - albedo feedback on sea ice predictability, to improve how...sea- ice albedo is modeled and how sea ice predictions are initialized, and then to evaluate how these improvements influence inherent sea ice

  14. DIRECT SOLUTIONS OF THE MAXWELL EQUATIONS EXPLAIN OPPOSITION PHENOMENA OBSERVED FOR HIGH-ALBEDO SOLAR SYSTEM OBJECTS

    International Nuclear Information System (INIS)

    Mishchenko, Michael I.; Liu Li; Dlugach, Janna M.; Rosenbush, Vera K.; Kiselev, Nikolai N.; Shkuratov, Yuri G.

    2009-01-01

    Several spectacular backscattering effects observed for particulate planetary surfaces have been interpreted in terms of the effect of weak localization (WL) of electromagnetic waves. However, the interference concept of WL explicitly relies on the notion of phase of an electromagnetic wave and is strictly applicable only when particles forming the surface are widely separated. Therefore, one needs a definitive quantitative proof of the WL nature of specific optical effects observed for densely packed particulate media. We use numerically exact computer solutions of the Maxwell equations to simulate electromagnetic scattering by realistic models consisting of large numbers of randomly positioned, densely packed particles. By increasing the particle packing density from zero to ∼40%, we track the onset and evolution of the full suite of backscattering optical effects predicted by the low-density theory of WL, including the brightness and polarization opposition effects (BOE and POE). We find that all manifestations of WL, except the circular polarization ratio and POE, are remarkably immune to packing-density effects. Even POE can survive packing densities typical of planetary regolith surfaces. Our numerical data coupled with the results of unique observations at near-backscattering geometries demonstrate that the BOE and POE detected simultaneously for high-albedo solar system objects are caused by the effect of WL.

  15. Assessing the possibility of a runaway ice-albedo feedback

    Science.gov (United States)

    Eisenman, I.

    2012-12-01

    If the ice-albedo feedback becomes dominant in high latitudes at some point as the climate warms, a runaway feedback will ensue in which the climate transitions to a new state. Such a transition occurs at a bifurcation point and is characterized by a discontinuity in the stable states available to the climate system. The possibility of such a runaway feedback in the Arctic has been investigated previously in a number of studies using both single-column models and comprehensive global models, and they have produced widely differing results. Here, I will use a toy model to evaluate the varied previously published results. The toy model represents the physics of sea ice growth and melt below a single column of the atmosphere, and the strength of interacting climate feedbacks such as albedo, clouds, and water vapor are controlled by scalable parameters. The toy model results suggest a novel measure, which can be assessed based on the current climate state, of how prone to instability the sea ice cover will be under global warming. I will demonstrate this measure in simulations from two state-of-the-art climate models, one of which has been shown to simulate a runaway ice-albedo feedback in the Arctic climate response to substantial greenhouse forcing and the other of which has been shown not to. This measure, which is based only on the simulated 20th century climate in each model, correctly identifies the model more prone to Arctic sea ice instability under substantial global warming.

  16. Assessment of the accuracy of snow surface direct beam spectral albedo under a variety of overcast skies derived by a reciprocal approach through radiative transfer simulation.

    Science.gov (United States)

    Li, Shusun; Zhou, Xiaobing

    2003-09-20

    With radiative transfer simulations it is suggested that stable estimates of the highly anisotropic direct beam spectral albedo of snow surface can be derived reciprocally under a variety of overcast skies. An accuracy of +/- 0.008 is achieved over a solar zenith angle range of theta0 snow surface albedo for the polar regions where direct measurement of clear-sky surface albedo is limited to large theta0's only. The enhancement will assist in the validation of snow surface albedo models and improve the representation of polar surface albedo in global circulation models.

  17. Spatial and temporal variations of albedo and absorbed solar radiation during 2009 - 2016 from IKOR-M satellite program

    Science.gov (United States)

    Cherviakov, Maksim; Bogdanov, Mikhail; Spiryakhina, Anastasia; Shishkina, Elena; Surkova, Yana; Kulkova, Eugenia

    2017-04-01

    This report describes Earth's radiation budget IKOR-M satellite program which has been started in Russia. The first satellite "Meteor-M» No 1 of this project was put into orbit in September, 2009. The IKOR-M radiometer is a satellite instrument that measures reflected shortwave radiation (0.3-4.0 µm). It was created in Saratov State University and installed on Russian hydrometeorological satellites "Meteor-M" No 1 and No 2. Radiometer IKOR-M designed for satellite monitoring of the outgoing reflected short-wave radiation, which is one of the components of Earth's radiation budget. Such measurements can be used to derive Earth's surface albedo and absorbed solar radiation. This information also can be used in different models of long-term weather forecasts and in researches of climate change trends (Sklyarov et al., 2016). Satellite "Meteor-M" No 1 and No 2 are heliosynchronous that allows observing from North to South Poles. The basic products of data processing are given in the form of global maps of distribution outgoing short-wave radiation (OSR), albedo and absorbed solar radiation (ASR). Such maps were made for each month during observation period. The IKOR-M product archive is available online at all times. A searchable catalogue of data products is continually updated and users may search and download data products via the Earth radiation balance components research laboratory website (http://www.sgu.ru/structure/geographic/metclim/balans) as soon as they become available. Two series of measurements from two different IKOR-M are available. The first radiometer had worked from October, 2009 to August, 2014 and second - from August, 2014 to the present. Therefore, there is a period when both radiometers work at the same time. Top-of-atmosphere fluxes deduced from the "Meteor-M" No 1 measurements in August, 2014 show very good agreement with the fluxes determined from "Meteor-M" No 2 (Bogdanov et al., 2016). The effect of aging is investigated for first IKOR

  18. Planetary seismology and interiors

    Science.gov (United States)

    Toksoz, M. N.

    1979-01-01

    This report briefly summarizes knowledge gained in the area of planetary seismology in the period 1969-1979. Attention is given to the seismic instruments, the seismic environment (noise, characteristics of seismic wave propagation, etc.), and the seismicity of the moon and Mars as determined by the Apollo missions and Viking Lander experiments, respectively. The models of internal structures of the terrestrial planets are discussed, with the earth used for reference.

  19. Albedo of a hybrid poplar plantation in central Alberta, Canada

    Science.gov (United States)

    Price, D. T.; Bernier, P. Y.; Orchansky, A.; Thomas, B.

    2012-04-01

    Canada's boreal forest resources are coming under increasing pressure from competing land-uses, including establishment of protected areas, and losses of harvestable forest to mining and oil and gas exploration. In the prairie region, concerns about lack of wood supply for pulpmills and potential opportunities for bioenergy production and carbon sequestration for climate change mitigation, have spurred interest in afforestation of marginal agricultural land, notably with fast-growing hybrid poplars (HP). However, global modelling studies suggest that a shift from grassland or crops to forest cover in temperate and boreal regions could result in reduced surface albedo, particularly in winter, causing an increase in radiative forcing and reducing any climate mitigation benefits due to net GHG removal. We report on seven growing seasons of measurements of short-wave canopy albedo using tower-mounted instruments, along with eddy covariance measurements of carbon, water and energy balance, at a site in central Alberta planted with HP cuttings in spring 2005. The data show little systematic change in average albedo as vegetation has changed from bare ground to a plantation of 6 m trees. Reasons for this include very wide (3 m) spacing between the trees, and snow cover which often persists for 4-5 months and is highly visible below the bare canopies during winter. While measurements should continue as the trees grow larger, we postulate that extensive afforestation with HP is unlikely to have major effects on regional-scale surface albedo compared to the agricultural systems they replace. Normal rotation lengths are 15-20 years, hence even if older plantations have significantly lower winter albedo, their contribution to the regional average would be relatively small because they will cover only a small fraction of the landscape (e.g., compared to forests of boreal conifers or temperate broadleaved species).

  20. The Impact of Microphysics and Planetary Boundary Layer Physics on Model Simulation of U.S. Deep South Summer Convection

    Science.gov (United States)

    McCaul, Eugene W., Jr.; Case, Jonathan L.; Zavodsky, Bradley T.; Srikishen, Jayanthi; Medlin, Jeffrey M.; Wood, Lance

    2014-01-01

    Inspection of output from various configurations of high-resolution, explicit convection forecast models such as the Weather Research and Forecasting (WRF) model indicates significant sensitivity to the choices of model physics pararneterizations employed. Some of the largest apparent sensitivities are related to the specifications of the cloud microphysics and planetary boundary layer physics packages. In addition, these sensitivities appear to be especially pronounced for the weakly-sheared, multicell modes of deep convection characteristic of the Deep South of the United States during the boreal summer. Possible ocean-land sensitivities also argue for further examination of the impacts of using unique ocean-land surface initialization datasets provided by the NASA Short-term Prediction Research and Transition (SPoRn Center to select NOAAlNWS weather forecast offices. To obtain better quantitative understanding of these sensitivities and also to determine the utility of the ocean-land initialization data, we have executed matrices of regional WRF forecasts for selected convective events near Mobile, AL (MOB), and Houston, TX (HGX). The matrices consist of identically initialized WRF 24-h forecasts using any of eight microphysics choices and any of three planetary boWldary layer choices. The resulting 24 simulations performed for each event within either the MOB or HGX regions are then compared to identify the sensitivities of various convective storm metrics to the physics choices. Particular emphasis is placed on sensitivities of precipitation timing, intensity, and coverage, as well as amount and coverage oflightuing activity diagnosed from storm kinematics and graupel in the mixed phase layer. The results confirm impressions gleaned from study of the behavior of variously configured WRF runs contained in the ensembles produced each spring at the Center for the Analysis and Prediction of Storms, but with the benefit of more straightforward control of the

  1. From red giants to planetary nebulae

    International Nuclear Information System (INIS)

    Kwok, S.

    1982-01-01

    The transition from red giants to planetary nebulae is studied by comparing the spectral characteristics of red giant envelopes and planetary nebulae. Observational and theoretical evidence both suggest that remnants of red giant envelopes may still be present in planetary nebula systems and should have significant effects on their formation. The dynamical effects of the interaction of stellar winds from central stars of planetary nebulae with the remnant red giant envelopes are evaluated and the mechanism found to be capable of producing the observed masses and momenta of planetary nebulae. The observed mass-radii relation of planetary nebulae may also be best explained by the interacting winds model. The possibility that red giant mass loss, and therefore the production of planetary nebulae, is different between Population I and II systems is also discussed

  2. ISLSCP II NOAA 5-year Average Monthly Snow-free Albedo from AVHRR

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The objective of this work was to produce a monthly climatology of broadband surface albedos for use in global numerical weather prediction models at the...

  3. ISLSCP II NOAA 5-year Average Monthly Snow-free Albedo from AVHRR

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this work was to produce a monthly climatology of broadband surface albedos for use in global numerical weather prediction models at the National...

  4. Estimation of Instantaneous TOA Albedo at 670 nm over Ice Clouds from POLDER Multidirectional Measurements

    Science.gov (United States)

    Sun, W.; Loeb, N. G.; Kato, S.

    2003-01-01

    An algorithm that determines the 670-nm top-of-atmosphere (TOA) albedo of ice clouds over ocean using Polarization and Directionality of the Earth's Reflectance ( POLDER) multidirectional measurements is developed. A plane-parallel layer of ice cloud with various optical thicknesses and light scattering phase functions is assumed. For simplicity, we use a double Henyey-Greenstein phase function to approximate the volume-averaged phase function of the ice clouds. A multidirectional reflectance best-fit match between theoretical and POLDER reflectances is used to infer effective cloud optical thickness, phase function and TOA albedo. Sensitivity tests show that while the method does not provide accurate independent retrievals of effective cloud optical depth and phase function, TOA albedo retrievals are accurate to within similar to 3% for both a single layer of ice clouds or a multilayer system of ice clouds and water clouds. When the method is applied to POLDER measurements and retrieved albedos are compared with albedos based on empirical angular distribution models (ADMs), zonal albedo differences are generally smaller than similar to 3%. When albedos are compared with those on the POLDER-I ERB and Cloud product, the differences can reach similar to 15% at small solar zenith angles.

  5. Mapping Surface Broadband Albedo from Satellite Observations: A Review of Literatures on Algorithms and Products

    Directory of Open Access Journals (Sweden)

    Ying Qu

    2015-01-01

    Full Text Available Surface albedo is one of the key controlling geophysical parameters in the surface energy budget studies, and its temporal and spatial variation is closely related to the global climate change and regional weather system due to the albedo feedback mechanism. As an efficient tool for monitoring the surfaces of the Earth, remote sensing is widely used for deriving long-term surface broadband albedo with various geostationary and polar-orbit satellite platforms in recent decades. Moreover, the algorithms for estimating surface broadband albedo from satellite observations, including narrow-to-broadband conversions, bidirectional reflectance distribution function (BRDF angular modeling, direct-estimation algorithm and the algorithms for estimating albedo from geostationary satellite data, are developed and improved. In this paper, we present a comprehensive literature review on algorithms and products for mapping surface broadband albedo with satellite observations and provide a discussion of different algorithms and products in a historical perspective based on citation analysis of the published literature. This paper shows that the observation technologies and accuracy requirement of applications are important, and long-term, global fully-covered (including land, ocean, and sea-ice surfaces, gap-free, surface broadband albedo products with higher spatial and temporal resolution are required for climate change, surface energy budget, and hydrological studies.

  6. Number Albedo of Low-Energy Photons

    International Nuclear Information System (INIS)

    Ljubenov, V.; Simovic, R.; Markovic, S.

    2007-01-01

    Number albedo of water, aluminum and iron for incident photons in energy range from 20 keV to 100 keV is presented in this paper. Results are obtained through the Monte Carlo simulations of photon reflection by using the MCNP, FOTELP and PENELOPE computer codes. Calculated values are compared with the classical data published by B. P. Bulatov and his collaborators. Influence of the fluorescence yield to the photon number albedo of iron target is analyzed in detail. (author)

  7. A framework for consistent estimation of leaf area index, fraction of absorbed photosynthetically active radiation, and surface albedo from MODIS time-series data

    DEFF Research Database (Denmark)

    Xiao, Zhiqiang; Liang, Shunlin; Wang, Jindi

    2015-01-01

    model and the MODIS surface reflectance data. The estimated LAI values were then input into the ACRM to calculate the surface albedo and the fraction of absorbed photosynthetically active radiation (FAPAR). For snow-covered areas, the surface albedo was calculated as the underlying vegetation canopy...... albedo plus the weighted distance between the underlying vegetation canopy albedo and the albedo over deep snow. The LAI/FAPAR and surface albedo values estimated using this framework were compared with MODIS collection 5 eight-day 1-km LAI/FAPAR products (MOD15A2) and 500-m surface albedo product (MCD43......-series MODerate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data. If the reflectance data showed snow-free areas, an ensemble Kalman filter (EnKF) technique was used to estimate leaf area index (LAI) for a two-layer canopy reflectance model (ACRM) by combining predictions from a phenology...

  8. Albedo Corrections for High Albedo Near Earth Objects Observed With Spitzer

    Science.gov (United States)

    Gustafsson, Annika; Trilling, David E.; Mommert, Michael; Hora, Joseph L.

    2017-10-01

    Thermal infrared observations are the most effective way to measure asteroid diameter and albedo. Major surveys like NEOWISE and NEOSurvey return a small fraction of objects with albedo values higher than that believed to exist in the near-Earth object (NEO) population. About 10% of Spitzer-observed NEOs have nominal albedo solutions greater than 0.5. There are many possible causes for these unrealistically high albedos, including thermal lightcurves (leading to a mis-estimate of asteroid diameter) or inaccurate absolute visual magnitudes (either from poor photometry or lightcurve effects). We present here the results of a ground-based optical photometric study of 36 high albedo NEOs from NEOSurvey (Trilling et al. 2016) using measurements from the Discovery Channel Telescope. Our findings indicate that uncertainty in the diameter has the most impact on the derived albedo of our targets, while the uncertainty in the H-magnitude and slope parameter have smaller effects. We supply corrected albedos for our target list, as well as a systematic offset dependent on the solar phase angle of the object (Mommert el al. 2017). These corrected albedo values will help constrain the albedo range in the population to better reflect its physical characteristics. This work is based in part on the observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

  9. Monitoring land surface albedo and vegetation dynamics using high spatial and temporal resolution synthetic time series from Landsat and the MODIS BRDF/NBAR/albedo product

    Science.gov (United States)

    Wang, Zhuosen; Schaaf, Crystal B.; Sun, Qingsong; Kim, JiHyun; Erb, Angela M.; Gao, Feng; Román, Miguel O.; Yang, Yun; Petroy, Shelley; Taylor, Jeffrey R.; Masek, Jeffrey G.; Morisette, Jeffrey T.; Zhang, Xiaoyang; Papuga, Shirley A.

    2017-07-01

    Seasonal vegetation phenology can significantly alter surface albedo which in turn affects the global energy balance and the albedo warming/cooling feedbacks that impact climate change. To monitor and quantify the surface dynamics of heterogeneous landscapes, high temporal and spatial resolution synthetic time series of albedo and the enhanced vegetation index (EVI) were generated from the 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) operational Collection V006 daily BRDF/NBAR/albedo products and 30 m Landsat 5 albedo and near-nadir reflectance data through the use of the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM). The traditional Landsat Albedo (Shuai et al., 2011) makes use of the MODIS BRDF/Albedo products (MCD43) by assigning appropriate BRDFs from coincident MODIS products to each Landsat image to generate a 30 m Landsat albedo product for that acquisition date. The available cloud free Landsat 5 albedos (due to clouds, generated every 16 days at best) were used in conjunction with the daily MODIS albedos to determine the appropriate 30 m albedos for the intervening daily time steps in this study. These enhanced daily 30 m spatial resolution synthetic time series were then used to track albedo and vegetation phenology dynamics over three Ameriflux tower sites (Harvard Forest in 2007, Santa Rita in 2011 and Walker Branch in 2005). These Ameriflux sites were chosen as they are all quite nearby new towers coming on line for the National Ecological Observatory Network (NEON), and thus represent locations which will be served by spatially paired albedo measures in the near future. The availability of data from the NEON towers will greatly expand the sources of tower albedometer data available for evaluation of satellite products. At these three Ameriflux tower sites the synthetic time series of broadband shortwave albedos were evaluated using the tower albedo measurements with a Root Mean Square Error (RMSE) less than 0.013 and a

  10. An investigation of ozone and planetary boundary layer dynamics over the complex topography of Grenoble combining measurements and modeling

    Directory of Open Access Journals (Sweden)

    O. Couach

    2003-01-01

    Full Text Available This paper concerns an evaluation of ozone (O3 and planetary boundary layer (PBL dynamics over the complex topography of the Grenoble region through a combination of measurements and mesoscale model (METPHOMOD predictions for three days, during July 1999. The measurements of O3 and PBL structure were obtained with a Differential Absorption Lidar (DIAL system, situated 20 km south of Grenoble at Vif (310 m ASL. The combined lidar observations and model calculations are in good agreement with atmospheric measurements obtained with an instrumented aircraft (METAIR. Ozone fluxes were calculated using lidar measurements of ozone vertical profiles concentrations and the horizontal wind speeds measured with a Radar Doppler wind profiler (DEGREANE. The ozone flux patterns indicate that the diurnal cycle of ozone production is controlled by local thermal winds. The convective PBL maximum height was some 2700 m above the land surface while the nighttime residual ozone layer was generally found between 1200 and 2200 m. Finally we evaluate the magnitude of the ozone processes at different altitudes in order to estimate the photochemical ozone production due to the primary pollutants emissions of Grenoble city and the regional network of automobile traffic.

  11. Regional climate modelling of the 2006 West African monsoon: sensitivity to convection and planetary boundary layer parameterisation using WRF

    Energy Technology Data Exchange (ETDEWEB)

    Flaounas, Emmanouil; Bastin, Sophie [UPMC, CNRS/INSU, LATMOS/IPSL, Paris cedex 05 (France); Janicot, Serge [UPMC, IRD, LOCEAN-IPSL, Paris (France)

    2011-03-15

    Regional climate model (RCM) is a valuable scientific tool to address the mechanisms of regional atmospheric systems such as the West African monsoon (WAM). This study aims to improve our understanding of the impact of some physical schemes of RCM on the WAM representation. The weather research and forecasting model has been used by performing six simulations of the 2006 summer WAM season. These simulations use all combinations of three convective parameterization schemes (CPSs) and two planetary boundary layer schemes (PBLSs). By comparing the simulations to a large set of observations and analysis products, we have evaluated the ability of these RCM parameterizations to reproduce different aspects of the regional atmospheric circulation of the WAM. This study focuses in particular on the WAM onset and the rainfall variability simulated over this domain. According to the different parameterizations tested, the PBLSs seem to have the strongest effect on temperature, humidity vertical distribution and rainfall amount. On the other hand, dynamics and precipitation variability are strongly influenced by CPSs. In particular, the Mellor-Yamada-Janjic PBLS attributes more realistic values of humidity and temperature. Combined with the Kain-Fritsch CPS, the WAM onset is well represented. The different schemes combination tested also reveal the role of different regional climate features on WAM dynamics, namely the low level circulation, the land-atmosphere interactions and the meridional temperature gradient between the Guinean coast and the Sahel. (orig.)

  12. Regional Climate Responses To Planetary-Scale Geoengineering Activities, as Modeled Using climateprediction.net/HadCM3L

    Science.gov (United States)

    Ricke, K.

    2009-12-01

    Concerns that climate mitigation is occurring too slowly, or that there may be a rapid "climate surprise," have lead to renewed dialogue within the scientific community about cooling the planet through geoengineering, specifically stratospheric albedo modification (SAM). There is little consensus about regional hydrological effects of such activities despite a recent spate of climate modeling studies looking at its potential impacts. Here we present the results from one large-ensemble experiment that used Hadley Centre Coupled Model, version 3 with reduced resolution over the ocean (HadCM3L), implemented through climateprediction.net. The analysis examines 54 globally-uniform stratospheric optical depth modification scenarios designed to stabilize global temperatures under SRES A1B. We present normalized regional temperature anomalies versus normalized regional precipitation and subsurface runoff anomalies (for example, see Figure 1) and the results of regression analyses to quantify the relationships between level of stratospheric optical property modification (i.e., geoengineering) and regional hydrology. Results show that while such shortwave compensations for longwave anthropogenic forcings does generally return regional climates to closer to their baseline climate states than the no-geoengineering, business-as-usual scenarios, the magnitudes and sensitivities of regional responses to this type of activity, as modeled in HadCM3L, are highly variable. Regions, such as Eastern China and India, migrate away from their baseline climate states in different ways, illustrating the impossibility of simultaneous stabilization of regional climates. The linearity of the effect of incrementally increasing stratospheric optical depth also varies regionally. Figure 1: Normalized regional temperature and precipitation anomalies (- and -) in units of baseline standard deviations for each region). Each grayscale point in-series near the origin represents data from 60

  13. Albedo enhancement over land to counteract global warming: impacts on hydrological cycle

    Energy Technology Data Exchange (ETDEWEB)

    Bala, Govindasamy; Nag, Bappaditya [Indian Institute of Science, Divecha Center for Climate Change and Center for Atmospheric and Oceanic Sciences, Bangalore (India)

    2012-09-15

    A recent modelling study has shown that precipitation and runoff over land would increase when the reflectivity of marine clouds is increased to counter global warming. This implies that large scale albedo enhancement over land could lead to a decrease in runoff over land. In this study, we perform simulations using NCAR CAM3.1 that have implications for Solar Radiation Management geoengineering schemes that increase the albedo over land. We find that an increase in reflectivity over land that mitigates the global mean warming from a doubling of CO{sub 2} leads to a large residual warming in the southern hemisphere and cooling in the northern hemisphere since most of the land is located in northern hemisphere. Precipitation and runoff over land decrease by 13.4 and 22.3%, respectively, because of a large residual sinking motion over land triggered by albedo enhancement over land. Soil water content also declines when albedo over land is enhanced. The simulated magnitude of hydrological changes over land are much larger when compared to changes over oceans in the recent marine cloud albedo enhancement study since the radiative forcing over land needed (-8.2 W m{sup -2}) to counter global mean radiative forcing from a doubling of CO{sub 2} (3.3 W m{sup -2}) is approximately twice the forcing needed over the oceans (-4.2 W m{sup -2}). Our results imply that albedo enhancement over oceans produce climates closer to the unperturbed climate state than do albedo changes on land when the consequences on land hydrology are considered. Our study also has important implications for any intentional or unintentional large scale changes in land surface albedo such as deforestation/afforestation/reforestation, air pollution, and desert and urban albedo modification. (orig.)

  14. Spatially Complete Surface Albedo Data Sets: Value-Added Products Derived from Terra MODIS Land Products

    Science.gov (United States)

    Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng

    2004-01-01

    Spectral land surface albedo is an important parameter for describing the radiative properties of the Earth. Accordingly it reflects the consequences of natural and human interactions, such as anthropogenic, meteorological, and phenological effects, on global and local climatological trends. Consequently, albedos are integral parts in a variety of research areas, such as general circulation models (GCMs), energy balance studies, modeling of land use and land use change, and biophysical, oceanographic, and meteorological studies. Recent observations of diffuse bihemispherical (white-sky) and direct beam directional hemispherical (black-sky ) land surface albedo included in the MOD43B3 product from MODIS instruments aboard NASA's Terra and Aqua satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal characteristics. Cloud and seasonal snow cover, however, curtail retrievals to approximately half the global land surfaces on an annual equal-angle basis, precluding MOD43B3 albedo products from direct inclusion in some research projects and production environments.

  15. Development of a Multilayer MODIS IST-Albedo Product of Greenland

    Science.gov (United States)

    Hall, D. K.; Comiso, J. C.; Cullather, R. I.; Digirolamo, N. E.; Nowicki, S. M.; Medley, B. C.

    2017-01-01

    A new multilayer IST-albedo Moderate Resolution Imaging Spectroradiometer (MODIS) product of Greenland was developed to meet the needs of the ice sheet modeling community. The multiple layers of the product enable the relationship between IST and albedo to be evaluated easily. Surface temperature is a fundamental input for dynamical ice sheet models because it is a component of the ice sheet radiation budget and mass balance. Albedo influences absorption of incoming solar radiation. The daily product will combine the existing standard MODIS Collection-6 ice-surface temperature, derived melt maps, snow albedo and water vapor products. The new product is available in a polar stereographic projection in NetCDF format. The product will ultimately extend from March 2000 through the end of 2017.

  16. Modelling Velocity Spectra in the Lower Part of the Planetary Boundary Layer

    DEFF Research Database (Denmark)

    Olesen, H.R.; Larsen, Søren Ejling; Højstrup, Jørgen

    1984-01-01

    Principles used when constructing models for velocity spectra are reviewed. Based upon data from the Kansas and Minnesota experiments, simple spectral models are set up for all velocity components in stable air at low heights, and for the vertical spectrum in unstable air through a larger part of...

  17. Arctic sea ice albedo from AVHRR

    Science.gov (United States)

    Lindsay, R. W.; Rothrock, D. A.

    1994-01-01

    The seasonal cycle of surface albedo of sea ice in the Arctic is estimated from measurements made with the Advanced Very High Resolution Radiometer (AVHRR) on the polar-orbiting satellites NOAA-10 and NOAA-11. The albedos of 145 200-km-square cells are analyzed. The cells are from March through September 1989 and include only those for which the sun is more than 10 deg above the horizon. Cloud masking is performed manually. Corrections are applied for instrument calibration, nonisotropic reflection, atmospheric interference, narrowband to broadband conversion, and normalization to a common solar zenith angle. The estimated albedos are relative, with the instrument gain set to give an albedo of 0.80 for ice floes in March and April. The mean values for the cloud-free portions of individual cells range from 0.18 to 0.91. Monthly averages of cells in the central Arctic range from 0.76 in April to 0.47 in August. The monthly averages of the within-cell standard deviations in the central Arctic are 0.04 in April and 0.06 in September. The surface albedo and surface temperature are correlated most strongly in March (R = -0.77) with little correlation in the summer. The monthly average lead fraction is determined from the mean potential open water, a scaled representation of the temperature or albedo between 0.0 (for ice) and 1.0 (for water); in the central Arctic it rises from an average 0.025 in the spring to 0.06 in September. Sparse data on aerosols, ozone, and water vapor in the atmospheric column contribute uncertainties to instantaneous, area-average albedos of 0.13, 0.04, and 0.08. Uncertainties in monthly average albedos are not this large. Contemporaneous estimation of these variables could reduce the uncertainty in the estimated albedo considerably. The poor calibration of AVHRR channels 1 and 2 is another large impediment to making accurate albedo estimates.

  18. Multiplatform observations enabling albedo retrievals with high temporal resolution

    Science.gov (United States)

    Riihelä, Aku; Manninen, Terhikki; Key, Jeffrey; Sun, Qingsong; Sütterlin, Melanie; Lattanzio, Alessio; Schaaf, Crystal

    2017-04-01

    In this paper we show that combining observations from different polar orbiting satellite families (such as AVHRR and MODIS) is physically justifiable and technically feasible. Our proposed approach will lead to surface albedo retrievals at higher temporal resolution than the state of the art, with comparable or better accuracy. This study is carried out in the World Meteorological Organization (WMO) Sustained and coordinated processing of Environmental Satellite data for Climate Monitoring (SCOPE-CM) project SCM-02 (http://www.scope-cm.org/projects/scm-02/). Following a spectral homogenization of the Top-of-Atmosphere reflectances of bands 1 & 2 from AVHRR and MODIS, both observation datasets are atmospherically corrected with a coherent atmospheric profile and algorithm. The resulting surface reflectances are then fed into an inversion of the RossThick-LiSparse-Reciprocal surface bidirectional reflectance distribution function (BRDF) model. The results of the inversion (BRDF kernels) may then be integrated to estimate various surface albedo quantities. A key principle here is that the larger number of valid surface observations with multiple satellites allows us to invert the BRDF coefficients within a shorter time span, enabling the monitoring of relatively rapid surface phenomena such as snowmelt. The proposed multiplatform approach is expected to bring benefits in particular to the observation of the albedo of the polar regions, where persistent cloudiness and long atmospheric path lengths present challenges to satellite-based retrievals. Following a similar logic, the retrievals over tropical regions with high cloudiness should also benefit from the method. We present results from a demonstrator dataset of a global combined AVHRR-GAC and MODIS dataset covering the year 2010. The retrieved surface albedo is compared against quality-monitored in situ albedo observations from the Baseline Surface Radiation Network (BSRN). Additionally, the combined retrieval

  19. SURFACE ALBEDO AND SPECTRAL VARIABILITY OF CERES

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian-Yang; Reddy, Vishnu; Corre, Lucille Le; Sykes, Mark V.; Prettyman, Thomas H. [Planetary Science Institute, 1700 E. Ft. Lowell Road, Suite 106, Tucson, AZ 85719 (United States); Nathues, Andreas; Hoffmann, Martin; Schaefer, Michael [Max Planck Institute for Solar System Research, Göttingen (Germany); Izawa, Matthew R. M.; Cloutis, Edward A. [University of Winnipeg, Winnipeg, Manitoba (Canada); Carsenty, Uri; Jaumann, Ralf; Krohn, Katrin; Mottola, Stefano; Schröder, Stefan E. [German Aerospace Center (DLR), Institute of Planetary Research, Berlin (Germany); Castillo-Rogez, Julie C. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Schenk, Paul [Lunar and Planetary Institute, Houston, TX 77058 (United States); Williams, David A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Smith, David E. [Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Zuber, Maria T. [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); and others

    2016-02-01

    Previous observations suggested that Ceres has active, but possibly sporadic, water outgassing as well as possibly varying spectral characteristics over a timescale of months. We used all available data of Ceres collected in the past three decades from the ground and the Hubble Space Telescope, as well as the newly acquired images by the Dawn  Framing Camera, to search for spectral and albedo variability on Ceres, on both a global scale and in local regions, particularly the bright spots inside the Occator crater, over timescales of a few months to decades. Our analysis has placed an upper limit on the possible temporal albedo variation on Ceres. Sporadic water vapor venting, or any possibly ongoing activity on Ceres, is not significant enough to change the albedo or the area of the bright features in the Occator crater by >15%, or the global albedo by >3% over the various timescales that we searched. Recently reported spectral slope variations can be explained by changing Sun–Ceres–Earth geometry. The active area on Ceres is less than 1 km{sup 2}, too small to cause global albedo and spectral variations detectable in our data. Impact ejecta due to impacting projectiles of tens of meters in size like those known to cause observable changes to the surface albedo on Asteroid Scheila cannot cause detectable albedo change on Ceres due to its relatively large size and strong gravity. The water vapor activity on Ceres is independent of Ceres’ heliocentric distance, ruling out the possibility of the comet-like sublimation process as a possible mechanism driving the activity.

  20. Significantly high polarization degree of the very low-albedo asteroid (152679) 1998 KU2

    Science.gov (United States)

    Kuroda, Daisuke; Ishiguro, Masateru; Watanabe, Makoto; Hasegawa, Sunao; Sekiguchi, Tomohiko; Naito, Hiroyuki; Usui, Fumihiko; Imai, Masataka; Sato, Mitsuteru; Kuramoto, Kiyoshi

    2018-03-01

    We present a unique and significant polarimetric result regarding the near-Earth asteroid (152679) 1998 KU2, which has a very low geometric albedo. From our observations, we find that the linear polarization degrees of 1998 KU2 are 44.6 ± 0.5% in the RC band and 44.0 ± 0.6% in the V band at a solar phase angle of 81.0°. These values are the highest of any known airless body in the solar system (i.e., high-polarization comets, asteroids, and planetary satellites) at similar phase angles. This polarimetric observation is not only the first for primitive asteroids at large phase angles, but also for low-albedo (Based on spectroscopic similarities and polarimetric measurements of materials that have been sorted by size in previous studies, we conjecture that 1998 KU2 has a highly microporous regolith structure comprising nano-sized carbon grains on the surface.

  1. Albedo impact on the suitability of biochar systems to mitigate global warming.

    Science.gov (United States)

    Meyer, Sebastian; Bright, Ryan M; Fischer, Daniel; Schulz, Hardy; Glaser, Bruno

    2012-11-20

    Biochar application to agricultural soils can change the surface albedo which could counteract the climate mitigation benefit of biochar systems. However, the size of this impact has not yet been quantified. Based on empirical albedo measurements and literature data of arable soils mixed with biochar, a model for annual vegetation cover development based on satellite data and an assessment of the annual development of surface humidity, an average mean annual albedo reduction of 0.05 has been calculated for applying 30-32 Mg ha(-1) biochar on a test field near Bayreuth, Germany. The impact of biochar production and application on the carbon cycle and on the soil albedo was integrated into the greenhouse gas (GHG) balance of a modeled pyrolysis based biochar system via the computation of global warming potential (GWP) characterization factors. The analysis resulted in a reduction of the overall climate mitigation benefit of biochar systems by 13-22% due to the albedo change as compared to an analysis which disregards the albedo effect. Comparing the use of the same quantity of biomass in a biochar system to a bioenergy district heating system which replaces natural gas combustion, bioenergy heating systems achieve 99-119% of the climate benefit of biochar systems according to the model calculation.

  2. STEM Engagement with NASA's Solar System Treks Portals for Lunar and Planetary Mapping and Modeling

    Science.gov (United States)

    Law, E. S.; Day, B. H.

    2018-01-01

    This presentation will provide an overview of the uses and capabilities of NASA's Solar System Treks family of online mapping and modeling portals. While also designed to support mission planning and scientific research, this presentation will focus on the Science, Technology, Engineering, and Math (STEM) engagement and public outreach capabilities of these web based suites of data visualization and analysis tools.

  3. Exponential law as a more compatible model to describe orbits of planetary systems

    Directory of Open Access Journals (Sweden)

    M Saeedi

    2012-12-01

    Full Text Available   According to the Titus-Bode law, orbits of planets in the solar system obey a geometric progression. Many investigations have been launched to improve this law. In this paper, we apply square and exponential models to planets of solar system, moons of planets, and some extra solar systems, and compare them with each other.

  4. A Model of Thermal Conductivity for Planetary Soils: 1. Theory for Unconsolidated Soils

    Science.gov (United States)

    Piqueux, S.; Christensen, P. R.

    2009-01-01

    We present a model of heat conduction for mono-sized spherical particulate media under stagnant gases based on the kinetic theory of gases, numerical modeling of Fourier s law of heat conduction, theoretical constraints on the gas thermal conductivity at various Knudsen regimes, and laboratory measurements. Incorporating the effect of the temperature allows for the derivation of the pore-filling gas conductivity and bulk thermal conductivity of samples using additional parameters (pressure, gas composition, grain size, and porosity). The radiative and solid-to-solid conductivities are also accounted for. Our thermal model reproduces the well-established bulk thermal conductivity dependency of a sample with the grain size and pressure and also confirms laboratory measurements finding that higher porosities generally lead to lower conductivities. It predicts the existence of the plateau conductivity at high pressure, where the bulk conductivity does not depend on the grain size. The good agreement between the model predictions and published laboratory measurements under a variety of pressures, temperatures, gas compositions, and grain sizes provides additional confidence in our results. On Venus, Earth, and Titan, the pressure and temperature combinations are too high to observe a soil thermal conductivity dependency on the grain size, but each planet has a unique thermal inertia due to their different surface temperatures. On Mars, the temperature and pressure combination is ideal to observe the soil thermal conductivity dependency on the average grain size. Thermal conductivity models that do not take the temperature and the pore-filling gas composition into account may yield significant errors.

  5. Arctic sea ice albedo - A comparison of two satellite-derived data sets

    Science.gov (United States)

    Schweiger, Axel J.; Serreze, Mark C.; Key, Jeffrey R.

    1993-01-01

    Spatial patterns of mean monthly surface albedo for May, June, and July, derived from DMSP Operational Line Scan (OLS) satellite imagery are compared with surface albedos derived from the International Satellite Cloud Climatology Program (ISCCP) monthly data set. Spatial patterns obtained by the two techniques are in general agreement, especially for June and July. Nevertheless, systematic differences in albedo of 0.05 - 0.10 are noted which are most likely related to uncertainties in the simple parameterizations used in the DMSP analyses, problems in the ISCCP cloud-clearing algorithm and other modeling simplifications. However, with respect to the eventual goal of developing a reliable automated retrieval algorithm for compiling a long-term albedo data base, these initial comparisons are very encouraging.

  6. MODELING OF MANUFACTURING ERRORS FOR PIN-GEAR ELEMENTS OF PLANETARY GEARBOX

    Directory of Open Access Journals (Sweden)

    Ivan M. Egorov

    2014-11-01

    Full Text Available Theoretical background for calculation of k-h-v type cycloid reducers was developed relatively long ago. However, recently the matters of cycloid reducer design again attracted heightened attention. The reason for that is that such devices are used in many complex engineering systems, particularly, in mechatronic and robotics systems. The development of advanced technological capabilities for manufacturing of such reducers today gives the possibility for implementation of essential features of such devices: high efficiency, high gear ratio, kinematic accuracy and smooth motion. The presence of an adequate mathematical model gives the possibility for adjusting kinematic accuracy of the reducer by rational selection of manufacturing tolerances for its parts. This makes it possible to automate the design process for cycloid reducers with account of various factors including technological ones. A mathematical model and mathematical technique have been developed giving the possibility for modeling the kinematic error of the reducer with account of multiple factors, including manufacturing errors. The errors are considered in the way convenient for prediction of kinematic accuracy early at the manufacturing stage according to the results of reducer parts measurement on coordinate measuring machines. During the modeling, the wheel manufacturing errors are determined by the eccentricity and radius deviation of the pin tooth centers circle, and the deviation between the pin tooth axes positions and the centers circle. The satellite manufacturing errors are determined by the satellite eccentricity deviation and the satellite rim eccentricity. Due to the collinearity, the pin tooth and pin tooth hole diameter errors and the satellite tooth profile errors for a designated contact point are integrated into one deviation. Software implementation of the model makes it possible to estimate the pointed errors influence on satellite rotation angle error and

  7. Modeling and Simulation of the Dynamics of Dissipative, Inelastic Spheres with Applications to Planetary Rovers and Gravitational Billiards

    Science.gov (United States)

    Hartl, Alexandre E.

    This dissertation provides a thorough treatment on the dynamic modeling and simulation of spherical objects, and its applications to planetary rovers and gravitational billiards. First, the equations governing the motion of a wind-driven spherical rover are developed, and a numerical procedure for their implementation is shown. Dynamic simulations (considering the Earth and Mars atmospheres) for several terrain types and conditions illustrate how a rover may maneuver across flat terrain, channels and craters. The effects of aerodynamic forces on the rover's motion is studied. The results show the wind force may both push and hinder the rover's motion while sliding, rolling and bouncing. The rover will periodically transition between these modes of movement when the rover impacts sloped surfaces. Combinations of rolling and bouncing may be a more effective means of transport for a rover traveling through a channel when compared to rolling alone. The aerodynamic effects, of drag and the Magnus force, are contributing factors to the possible capture of the rover by a crater. Next, a strategy is formulated for creating randomized Martian rock fields based on statistical models, where the rover's interactions with these fields are analyzed. Novel procedures for creating randomized Martian rock fields are presented, where optimization techniques allow terrain generation to coincide with the rover's motion. Efficient collision detection routines reduce the number of tests of potential collisions between the rover and the terrain while establishing new contact constraints. The procedures allow for the exploration of large regions of terrain while minimizing computational costs. Simulations demonstrate that bouncing is the rover's dominant mode of travel through the rock fields. Monte-Carlo simulations illustrate how the rover's down-range position depends on the rover design and atmospheric conditions. Moreover, the simulations verify the rover's capacity for long distance

  8. The Herschel Planetary Nebula Survey (HerPlaNS): A Comprehensive Dusty Photoionization Model of NGC6781.

    Science.gov (United States)

    Otsuka, Masaaki; Ueta, Toshiya; van Hoof, Peter A M; Sahai, Raghvendra; Aleman, Isabel; Zijlstra, Albert A; Chu, You-Hua; Villaver, Eva; Leal-Ferreira, Marcelo L; Kastner, Joel; Szczerba, Ryszard; Exter, Katrina M

    2017-08-01

    We perform a comprehensive analysis of the planetary nebula (PN) NGC 6781 to investigate the physical conditions of each of its ionized, atomic, and molecular gas and dust components and the object's evolution, based on panchromatic observational data ranging from UV to radio. Empirical nebular elemental abundances, compared with theoretical predictions via nucleosynthesis models of asymptotic giant branch (AGB) stars, indicate that the progenitor is a solar-metallicity, 2.25-3.0 M ⊙ initial-mass star. We derive the best-fit distance of 0.46 kpc by fitting the stellar luminosity (as a function of the distance and effective temperature of the central star) with the adopted post-AGB evolutionary tracks. Our excitation energy diagram analysis indicates high-excitation temperatures in the photodissociation region (PDR) beyond the ionized part of the nebula, suggesting extra heating by shock interactions between the slow AGB wind and the fast PN wind. Through iterative fitting using the Cloudy code with empirically derived constraints, we find the best-fit dusty photoionization model of the object that would inclusively reproduce all of the adopted panchromatic observational data. The estimated total gas mass (0.41 M ⊙ ) corresponds to the mass ejected during the last AGB thermal pulse event predicted for a 2.5 M ⊙ initial-mass star. A significant fraction of the total mass (about 70%) is found to exist in the PDR, demonstrating the critical importance of the PDR in PNe that are generally recognized as the hallmark of ionized/H + regions.

  9. Robotic Planetary Drill Tests

    Science.gov (United States)

    Glass, Brian J.; Thompson, S.; Paulsen, G.

    2010-01-01

    Several proposed or planned planetary science missions to Mars and other Solar System bodies over the next decade require subsurface access by drilling. This paper discusses the problems of remote robotic drilling, an automation and control architecture based loosely on observed human behaviors in drilling on Earth, and an overview of robotic drilling field test results using this architecture since 2005. Both rotary-drag and rotary-percussive drills are targeted. A hybrid diagnostic approach incorporates heuristics, model-based reasoning and vibration monitoring with neural nets. Ongoing work leads to flight-ready drilling software.

  10. FREQUENCY MODULATION OF DIRECTLY IMAGED EXOPLANETS: GEOMETRIC EFFECT AS A PROBE OF PLANETARY OBLIQUITY

    Energy Technology Data Exchange (ETDEWEB)

    Kawahara, Hajime, E-mail: kawahara@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033 (Japan); Research Center for the Early Universe, School of Science, The University of Tokyo, Tokyo 113-0033 (Japan)

    2016-05-10

    We consider the time–frequency analysis of a scattered light curve of a directly imaged exoplanet. We show that the geometric effect due to planetary obliquity and orbital inclination induce the frequency modulation of the apparent diurnal periodicity. We construct a model of the frequency modulation and compare it with the instantaneous frequency extracted from the pseudo-Wigner distribution of simulated light curves of a cloudless Earth. The model provides good agreement with the simulated modulation factor, even for the light curve with Gaussian noise comparable to the signal. Notably, the shape of the instantaneous frequency is sensitive to the difference between the prograde, retrograde, and pole-on spin rotations. While our technique requires the albedo map to be static, it does not need to solve the albedo map of the planet. The time–frequency analysis is complementary to other methods which utilize the amplitude modulation. This paper demonstrates the importance of the frequency domain of the photometric variability for the characterization of directly imaged exoplanets in future research.

  11. Mars Rover Model Celebration: Using Planetary Exploration To Enrich STEM Teaching In Elementary And Middle School

    Science.gov (United States)

    Bering, E. A.; Ramsey, J.; Dominey, W.; Kapral, A.; Carlson, C.; Konstantinidis, I.; James, J.; Sweaney, S.; Mendez, R.

    2011-12-01

    The present aerospace engineering and science workforce is ageing. It is not clear that the US education system will produce enough qualified replacements to meet the need in the near future. Unfortunately, by the time many students get to high school, it is often too late to get them pointed toward an engineering or science career. Since some college programs require 6 units of high school mathematics for admission, students need to begin consciously preparing for a science or engineering curriculum as early as 6th or 7th grade. The challenge for educators is to convince elementary school students that science and engineering are both exciting, relevant and accessible career paths. The recent NASA Mars Rover missions capture the imagination of children, as NASA missions have done for decades. The University of Houston is in the process of developing a prototype of a flexible program that offers children an in-depth educational experience culminating in the design and construction of their own model rover. The existing prototype program is called the Mars Rover Model Celebration. It focuses on students, teachers and parents in grades 3-8. Students will design and build a model of a Mars rover to carry out a student selected science mission on the surface of Mars. The model will be a mock-up, constructed at a minimal cost from art supplies. The students will build the models as part of a project on Mars. The students will be given design criteria for a rover and will do basic research on Mars that will determine the objectives and features of their rover. This project may be used either informally as an after school club or youth group activity or formally as part of a class studying general science, earth science, solar system astronomy or robotics, or as a multi-disciplinary unit for a gifted and talented program. The program culminates in a capstone event held at the University of Houston (or other central location in the other communities that will be involved

  12. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    Directory of Open Access Journals (Sweden)

    H. S. Negi

    2011-03-01

    Full Text Available In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20% using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

  13. PSUP: A Planetary SUrface Portal

    Science.gov (United States)

    Poulet, F.; Quantin-Nataf, C.; Ballans, H.; Dassas, K.; Audouard, J.; Carter, J.; Gondet, B.; Lozac'h, L.; Malapert, J.-C.; Marmo, C.; Riu, L.; Séjourné, A.

    2018-01-01

    The large size and complexity of planetary data acquired by spacecraft during the last two decades create a demand within the planetary community for access to the archives of raw and high level data and for the tools necessary to analyze these data. Among the different targets of the Solar System, Mars is unique as the combined datasets from the Viking, Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter missions provide a tremendous wealth of information that can be used to study the surface of Mars. The number and the size of the datasets require an information system to process, manage and distribute data. The Observatories of Paris Sud (OSUPS) and Lyon (OSUL) have developed a portal, called PSUP (Planetary SUrface Portal), for providing users with efficient and easy access to data products dedicated to the Martian surface. The objectives of the portal are: 1) to allow processing and downloading of data via a specific application called MarsSI (Martian surface data processing Information System); 2) to provide the visualization and merging of high level (image, spectral, and topographic) products and catalogs via a web-based user interface (MarsVisu), and 3) to distribute some of these specific high level data with an emphasis on products issued by the science teams of OSUPS and OSUL. As the MarsSI service is extensively described in a companion paper (Quantin-Nataf et al., companion paper, submitted to this special issue), the present paper focus on the general architecture and the functionalities of the web-based user interface MarsVisu. This service provides access to many data products for Mars: albedo, mineral and thermal inertia global maps from spectrometers; mosaics from imagers; image footprints and rasters from the MarsSI tool; high level specific products (defined as catalogs or vectors). MarsVisu can be used to quickly assess the visualized processed data and maps as well as identify areas that have not been mapped yet

  14. Mathematical models of non-linear phenomena, processes and systems: from molecular scale to planetary atmosphere

    CERN Document Server

    2013-01-01

    This book consists of twenty seven chapters, which can be divided into three large categories: articles with the focus on the mathematical treatment of non-linear problems, including the methodologies, algorithms and properties of analytical and numerical solutions to particular non-linear problems; theoretical and computational studies dedicated to the physics and chemistry of non-linear micro-and nano-scale systems, including molecular clusters, nano-particles and nano-composites; and, papers focused on non-linear processes in medico-biological systems, including mathematical models of ferments, amino acids, blood fluids and polynucleic chains.

  15. Planetary Data System (PDS)

    Data.gov (United States)

    National Aeronautics and Space Administration — The Planetary Data System (PDS) is an archive of data products from NASA planetary missions, which is sponsored by NASA's Science Mission Directorate. We actively...

  16. Laboratory measurements and modeling of molecular photoabsorption in the ultraviolet for planetary atmospheres applications: diatomic sulfur and sulfur monoxide

    Science.gov (United States)

    Stark, Glenn

    2016-07-01

    Our research program comprises the measurement and modeling of ultraviolet molecular photoabsorption cross sections with the highest practical resolution. It supports efforts to interpret and model observations of planetary atmospheres. Measurement and modeling efforts on diatomic sulfur (S _{2}) and sulfur monoxide (SO) are in progress. S _{2}: Interpretations of atmospheric (Io, Jupiter, cometary comae) S _{2} absorption features are hindered by a complete lack of laboratory cross section data in the ultraviolet. We are working to quantify the photoabsorption spectrum of S _{2} from 240 to 300 nm based on laboratory measurements and theoretical calculations. We have constructed an experimental apparatus to produce a stable column of S _{2} vapor at a temperature of 800 K. High-resolution measurements of the absorption spectrum of the strong B - X system of S _{2} were completed using the NIST VUV-FTS at Gaithersburg, Maryland. These measurements are currently being incorporated into a coupled-channel model of the absorption spectrum of S _{2} to quantify the contributions from individual band features and to establish the mechanisms responsible for the strong predissociation signature of the B - X system. A successful coupled channels model can then be used to calculate the B - X absorption spectrum at any temperature. SO: There has been a long-standing need for high-resolution cross sections of sulfur monoxide radicals in the ultraviolet and vacuum ultraviolet regions, where the molecule strongly predissociates, for modeling the atmospheres of Io and Venus, and most recently for understanding sulfur isotope effects in the ancient (pre-O _{2}) atmosphere of Earth. We have produced a measurable column of SO in a continuous-flow DC discharge cell, using SO _{2} as a parent molecule. Photoabsorption measurements were recently recorded on the DESIRS beamline of the SOLEIL synchrotron, taking advantage of the high-resolution VUV-FTS on that beamline. A number of

  17. Climate, ecosystems, and planetary futures: The challenge to predict life in Earth system models.

    Science.gov (United States)

    Bonan, Gordon B; Doney, Scott C

    2018-02-02

    Many global change stresses on terrestrial and marine ecosystems affect not only ecosystem services that are essential to humankind, but also the trajectory of future climate by altering energy and mass exchanges with the atmosphere. Earth system models, which simulate terrestrial and marine ecosystems and biogeochemical cycles, offer a common framework for ecological research related to climate processes; analyses of vulnerability, impacts, and adaptation; and climate change mitigation. They provide an opportunity to move beyond physical descriptors of atmospheric and oceanic states to societally relevant quantities such as wildfire risk, habitat loss, water availability, and crop, fishery, and timber yields. To achieve this, the science of climate prediction must be extended to a more multifaceted Earth system prediction that includes the biosphere and its resources. Copyright © 2018, American Association for the Advancement of Science.

  18. Single-column model and large eddy simulation of the evening transition in the planetary boundary layer

    Science.gov (United States)

    Cuchiara, Gustavo; Rappenglück, Bernhard

    2016-04-01

    The transition from the convective boundary layer during the daytime to the stable stratified boundary layer during nighttime after sunset plays an important role in the transport and dispersion of atmospheric pollutants. However, our knowledge regarding this transition and its feedback on the structure of the subsequent nocturnal boundary layer is still restricted. This also prevents forecast models from accurate prediction of the onset and development of the nighttime boundary layer, which determines the redistribution of pollutants within the nocturnal surface layer and the residual layer aloft. In the present study, the well-known case of day 33 of the Wangara experiment is resimulated using the Weather Research and Forecasting (WRF) model in an idealized single-column mode to assess the performance of a frequently used planetary boundary layer (PBL) scheme, the Yonsei University (YSU) PBL scheme. These results are compared with two large eddy simulations (LES) for the same case study imposing different surface fluxes: one using previous surface fluxes calculated for the Wangara experiment and a second one using output from the WRF model. The results show a reasonable agreement of the PBL scheme in WRF with the LES. Overall, all the simulations presented a cold bias of ~3 Kelvin for the potential temperature and underestimation of the wind speed, especially after the transition to nighttime conditions (biases were up to 4 ms-1). Finally, an alternative set of eddy diffusivity equations was tested to represent the transition characteristics of a sunset period, with a stable layer below and a new parameterization for the convective decay regime typically observed in the RL aloft. This set of equations led to a gradual decrease of the eddy diffusivity, which replaces the instantaneous collapse of traditional diagnostics for eddy diffusivities. More appreciable changes were observed in air temperature, wind speed and specific humidity (up to 0.5 K, 0.6 ms-1, and 0

  19. Ensemble using different Planetary Boundary Layer schemes in WRF model for wind speed and direction prediction over Apulia region

    Science.gov (United States)

    Tateo, Andrea; Marcello Miglietta, Mario; Fedele, Francesca; Menegotto, Micaela; Monaco, Alfonso; Bellotti, Roberto

    2017-04-01

    The Weather Research and Forecasting mesoscale model (WRF) was used to simulate hourly 10 m wind speed and direction over the city of Taranto, Apulia region (south-eastern Italy). This area is characterized by a large industrial complex including the largest European steel plant and is subject to a Regional Air Quality Recovery Plan. This plan constrains industries in the area to reduce by 10 % the mean daily emissions by diffuse and point sources during specific meteorological conditions named wind days. According to the Recovery Plan, the Regional Environmental Agency ARPA-PUGLIA is responsible for forecasting these specific meteorological conditions with 72 h in advance and possibly issue the early warning. In particular, an accurate wind simulation is required. Unfortunately, numerical weather prediction models suffer from errors, especially for what concerns near-surface fields. These errors depend primarily on uncertainties in the initial and boundary conditions provided by global models and secondly on the model formulation, in particular the physical parametrizations used to represent processes such as turbulence, radiation exchange, cumulus and microphysics. In our work, we tried to compensate for the latter limitation by using different Planetary Boundary Layer (PBL) parameterization schemes. Five combinations of PBL and Surface Layer (SL) schemes were considered. Simulations are implemented in a real-time configuration since our intention is to analyze the same configuration implemented by ARPA-PUGLIA for operational runs; the validation is focused over a time range extending from 49 to 72 h with hourly time resolution. The assessment of the performance was computed by comparing the WRF model output with ground data measured at a weather monitoring station in Taranto, near the steel plant. After the analysis of the simulations performed with different PBL schemes, both simple (e.g. average) and more complex post-processing methods (e.g. weighted average

  20. Multiple Scattering in Planetary Regoliths Using Incoherent Interactions

    Science.gov (United States)

    Muinonen, K.; Markkanen, J.; Vaisanen, T.; Penttilä, A.

    2017-12-01

    We consider scattering of light by a planetary regolith using novel numerical methods for discrete random media of particles. Understanding the scattering process is of key importance for spectroscopic, photometric, and polarimetric modeling of airless planetary objects, including radar studies. In our modeling, the size of the spherical random medium can range from microscopic to macroscopic sizes, whereas the particles are assumed to be of the order of the wavelength in size. We extend the radiative transfer and coherent backscattering method (RT-CB) to the case of dense packing of particles by adopting the ensemble-averaged first-order incoherent extinction, scattering, and absorption characteristics of a volume element of particles as input. In the radiative transfer part, at each absorption and scattering process, we account for absorption with the help of the single-scattering albedo and peel off the Stokes parameters of radiation emerging from the medium in predefined scattering angles. We then generate a new scattering direction using the joint probability density for the local polar and azimuthal scattering angles. In the coherent backscattering part, we utilize amplitude scattering matrices along the radiative-transfer path and the reciprocal path. Furthermore, we replace the far-field interactions of the RT-CB method with rigorous interactions facilitated by the Superposition T-matrix method (STMM). This gives rise to a new RT-RT method, radiative transfer with reciprocal interactions. For microscopic random media, we then compare the new results to asymptotically exact results computed using the STMM, succeeding in the numerical validation of the new methods.Acknowledgments. Research supported by European Research Council with Advanced Grant No. 320773 SAEMPL, Scattering and Absorption of ElectroMagnetic waves in ParticuLate media. Computational resources provided by CSC - IT Centre for Science Ltd, Finland.

  1. The LatHyS database for planetary plasma environment investigations: Overview and a case study of data/model comparisons

    Science.gov (United States)

    Modolo, R.; Hess, S.; Génot, V.; Leclercq, L.; Leblanc, F.; Chaufray, J.-Y.; Weill, P.; Gangloff, M.; Fedorov, A.; Budnik, E.; Bouchemit, M.; Steckiewicz, M.; André, N.; Beigbeder, L.; Popescu, D.; Toniutti, J.-P.; Al-Ubaidi, T.; Khodachenko, M.; Brain, D.; Curry, S.; Jakosky, B.; Holmström, M.

    2018-01-01

    We present the Latmos Hybrid Simulation (LatHyS) database, which is dedicated to the investigations of planetary plasma environment. Simulation results of several planetary objects (Mars, Mercury, Ganymede) are available in an online catalogue. The full description of the simulations and their results is compliant with a data model developped in the framework of the FP7 IMPEx project. The catalogue is interfaced with VO-visualization tools such AMDA, 3DView, TOPCAT, CLweb or the IMPEx portal. Web services ensure the possibilities of accessing and extracting simulated quantities/data. We illustrate the interoperability between the simulation database and VO-tools using a detailed science case that focuses on a three-dimensional representation of the solar wind interaction with the Martian upper atmosphere, combining MAVEN and Mars Express observations and simulation results.

  2. THOR: A NEW AND FLEXIBLE GLOBAL CIRCULATION MODEL TO EXPLORE PLANETARY ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Mendonça, João M.; Grimm, Simon L.; Grosheintz, Luc; Heng, Kevin, E-mail: joao.mendonca@csh.unibe.ch, E-mail: kevin.heng@csh.unibe.ch [University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012, Bern (Switzerland)

    2016-10-01

    We have designed and developed, from scratch, a global circulation model (GCM) named THOR that solves the three-dimensional nonhydrostatic Euler equations. Our general approach lifts the commonly used assumptions of a shallow atmosphere and hydrostatic equilibrium. We solve the “pole problem” (where converging meridians on a sphere lead to increasingly smaller time steps near the poles) by implementing an icosahedral grid. Irregularities in the grid, which lead to grid imprinting, are smoothed using the “spring dynamics” technique. We validate our implementation of spring dynamics by examining calculations of the divergence and gradient of test functions. To prevent the computational time step from being bottlenecked by having to resolve sound waves, we implement a split-explicit method together with a horizontally explicit and vertically implicit integration. We validate our GCM by reproducing the Earth and hot-Jupiter-like benchmark tests. THOR was designed to run on graphics processing units (GPUs), which allows for physics modules (radiative transfer, clouds, chemistry) to be added in the future, and is part of the open-source Exoclimes Simulation Platform (www.exoclime.org).

  3. MODEL-INDEPENDENT STELLAR AND PLANETARY MASSES FROM MULTI-TRANSITING EXOPLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    Montet, Benjamin T.; Johnson, John Asher

    2013-01-01

    Precise exoplanet characterization requires precise classification of exoplanet host stars. The masses of host stars are commonly estimated by comparing their spectra to those predicted by stellar evolution models. However, spectroscopically determined properties are difficult to measure accurately for stars that are substantially different from the Sun, such as M-dwarfs and evolved stars. Here, we propose a new method to dynamically measure the masses of transiting planets near mean-motion resonances and their host stars by combining observations of transit timing variations with radial velocity (RV) measurements. We derive expressions to analytically determine the mass of each member of the system and demonstrate the technique on the Kepler-18 system. We compare these analytic results to numerical simulations and find that the two are consistent. We identify eight systems for which our technique could be applied if follow-up RV measurements are collected. We conclude that this analysis would be optimal for systems discovered by next-generation missions similar to TESS or PLATO, which will target bright stars that are amenable to efficient RV follow-up.

  4. MODIS/Terra+Aqua BRDF/Albedo Parameters 16-Day L3 Global 0.05Deg CMG V005

    Data.gov (United States)

    National Aeronautics and Space Administration — The MODerate-resolution Imaging Spectroradiometer (MODIS) BRDF/Albedo Model Parameters product (MCD43C1) contains the weighting parameters for the models used to...

  5. Integrating the Teaching of Space Science, Planetary Exploration And Robotics In Elementary And Middle School with Mars Rover Models

    Science.gov (United States)

    Bering, E. A.; Ramsey, J.; Smith, H.; Boyko, B. S.; Peck, S.; Arcenaux, W. H.

    2005-05-01

    The present aerospace engineering and science workforce is ageing. It is not clear that the US education system will produce enough qualified replacements to meet the need in the near future. Unfortunately, by the time many students get to high school, it is often too late to get them pointed toward an engineering or science career. Since some college programs require 6 units of high school mathematics for admission, students need to begin consciously preparing for a science or engineering curriculum as early as 6th or 7th grade. The challenge for educators is to convince elementary school students that science and engineering are both exciting, relevant and accessible career paths. This paper describes a program designed to help provide some excitement and relevance. It is based on the task of developing a mobile robot or "Rover" to explore the surface of Mars. There are two components to the program, a curriculum unit and a contest. The curriculum unit is structured as a 6-week planetary science unit for elementary school (grades 3-5). It can also be used as a curriculum unit, enrichment program or extracurricular activity in grades 6-8 by increasing the expected level of scientific sophistication in the mission design. The second component is a citywide competition to select the most outstanding models that is held annually at a local college or University. Primary (Grades 3-5) and middle school (Grades 6-8) students interested in science and engineering will design and build of a model of a Mars Rover to carry out a specific science mission on the surface of Mars. The students will build the models as part of a 6-week Fall semester classroom-learning or homework project on Mars. The students will be given design criteria for a rover, and be required to do basic research on Mars that will determine the operational objectives and structural features of their rover. This module may be used as part of a class studying general science, earth science, solar system

  6. Enhanced albedo feedback in North Africa from possible combined vegetation and soil-formation processes

    Energy Technology Data Exchange (ETDEWEB)

    Knorr, Wolfgang [University of Bristol, Department of Earth Sciences, Bristol (United Kingdom); Schnitzler, Karl-Georg [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    2006-01-01

    It has long been recognized that albedo related vegetation feedbacks amplify climate variability in North Africa. Recent studies have revealed that areas of very high albedo associated with certain desert soil types contribute to the current dry climate of the region. We construct three scenarios of North African albedo, one based on satellite measurements, one where the highest albedo resembles that of soils in the desert transition zones, and one based on a vegetation map for the ''green Sahara'' state of the middle Holocene, ca. 6,000 years ago. Using a series of climate model simulations, we find that the additional amplitude of albedo change from the middle Holocene to the present caused by the very bright desert soils enhances the magnitude of the June-to-August precipitation change in the region of the present Sahara from 0.6 to 1.0 mm/day on average. We also find that albedo change has a larger effect on regional precipitation than changes in either the Earth's orbit or sea surface temperatures between 6,000 years ago and today. Simulated precipitation agrees rather well with present observations and mid Holocene reconstructions. Our results suggest that there may exist an important climate feedback from soil formation processes that has so far not been recognized. (orig.)

  7. Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen

    2010-02-12

    The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing and land surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe by 0.1. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the change in the total outgoing (outgoing shortwave+longwave) radiation and land surface temperature to a 0.1 increase in urban albedos for all global land areas. The global average increase in the total outgoing radiation was 0.5 Wm{sup -2}, and temperature decreased by {approx}0.008 K for an average 0.003 increase in surface albedo. These averages represent all global land areas where data were available from the land surface model used and are for the boreal summer (June-July-August). For the continental U.S. the total outgoing radiation increased by 2.3 Wm{sup -2}, and land surface temperature decreased by {approx}0.03 K for an average 0.01 increase in surface albedo. Based on these forcings, the expected emitted CO{sub 2} offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be {approx} 57 Gt CO{sub 2}. A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO{sub 2} offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.

  8. VARIATIONAL PRINCIPLE FOR PLANETARY INTERIORS

    International Nuclear Information System (INIS)

    Zeng, Li; Jacobsen, Stein B.

    2016-01-01

    In the past few years, the number of confirmed planets has grown above 2000. It is clear that they represent a diversity of structures not seen in our own solar system. In addition to very detailed interior modeling, it is valuable to have a simple analytical framework for describing planetary structures. The variational principle is a fundamental principle in physics, entailing that a physical system follows the trajectory, which minimizes its action. It is alternative to the differential equation formulation of a physical system. Applying the variational principle to the planetary interior can beautifully summarize the set of differential equations into one, which provides us some insight into the problem. From this principle, a universal mass–radius relation, an estimate of the error propagation from the equation of state to the mass–radius relation, and a form of the virial theorem applicable to planetary interiors are derived.

  9. NEOWISE DIAMETERS AND ALBEDOS V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This PDS data set represents a compilation of published diameters, optical albedos, near-infrared albedos, and beaming parameters for minor planets detected by...

  10. Comparison between Snow Albedo Obtained from Landsat TM, ETM+ Imagery and the SPOT VEGETATION Albedo Product in a Mediterranean Mountainous Site

    Directory of Open Access Journals (Sweden)

    Rafael Pimentel

    2016-02-01

    Full Text Available Albedo plays an important role in snow evolution modeling quantifying the amount of solar radiation absorbed and reflected by the snowpack, especially in mid-latitude regions with semiarid conditions. Satellite remote sensing is the most extensive technique to determine the variability of snow albedo over medium to large areas; however, scale effects from the pixel size of the sensor source may affect the results of snow models, with different impacts depending on the spatial resolution. This work presents the evaluation of snow albedo values retrieved from (1 Landsat images, L (16-day frequency with 30 × 30 m pixel size and (2 SPOT VEGETATION albedo products, SV (10-day frequency with 1 × 1 km pixel size in the Sierra Nevada mountain range in South Spain, a Mediterranean site representative of highly heterogeneous conditions. Daily snow albedo map series were derived from both sources, and used as input for the snow module in the WiMMed (Watershed Integrated Management in Mediterranean Environment hydrological model, which was operational at the study area for snow monitoring for two hydrological years, 2011–2012 and 2012–2013, in the Guadalfeo river basin in Sierra Nevada. The results showed similar albedo trends in both data sources, but with different values, the shift between both sources being distributed in space according to the altitude. This difference resulted in lower snow cover fraction values in the SV-simulations that affected the rest of snow variables included in the simulation. This underestimation, mainly due to the effects of mixed pixels composed by both snow and snow-free areas, produced higher divergences from both sources during the melting periods when the evapo-sublimation and melting fluxes are more relevant. Therefore, the selection of the albedo data source in these areas, where snow evapo-sublimation plays a very important role and the presence of snow-free patches is very frequent, can condition the final

  11. Planetary magnetism

    International Nuclear Information System (INIS)

    Dolginov, Sh.Sh.

    1977-01-01

    Experimental data on magnetic fields of planets are surveyed. The magnetic fields of the Earth, Jupiter, Mars, Mercury, Venus, and the Moon are considered in detail. A similarity of the physical models of both the planets of the Earth group and the giant planets was revealed. The fields of the planets and of the Earth are compared in the scheme of the precession dynamo and in the kinematic scheme. Proceeding from the assumption that the Poincare forces and their ratio to other forces are model-similar in the cores of all the planets, the values of Hsub(i)/Hsub(E) are calculated, where Hsub(i) and Hsub(E) are the field strengths of the i-th planet and that of the Earth. The experimental data on the dynamic compression of the Mercury confirm the calculations made. It is concluded that the problem of the origin and moving forces of the terrestrial magnetic field may be resolved only within the framework of comparative planetology

  12. The Impacts of Microphysics and Planetary Boundary Layer Physics on Model Simulations of U.S. Deep South Summer Convection

    Science.gov (United States)

    McCaul, Eugene W., Jr.; Case, Jonathan L.; Zavodsky, Bradley; Srikishen, Jayanthi; Medlin, Jeffrey; Wood, Lance

    2014-01-01

    Convection-allowing numerical weather simula- tions have often been shown to produce convective storms that have significant sensitivity to choices of model physical parameterizations. Among the most important of these sensitivities are those related to cloud microphysics, but planetary boundary layer parameterizations also have a significant impact on the evolution of the convection. Aspects of the simulated convection that display sensitivity to these physics schemes include updraft size and intensity, simulated radar reflectivity, timing and placement of storm initi- ation and decay, total storm rainfall, and other storm features derived from storm structure and hydrometeor fields, such as predicted lightning flash rates. In addition to the basic parameters listed above, the simulated storms may also exhibit sensitivity to im- posed initial conditions, such as the fields of soil temper- ature and moisture, vegetation cover and health, and sea and lake water surface temperatures. Some of these sensitivities may rival those of the basic physics sensi- tivities mentioned earlier. These sensitivities have the potential to disrupt the accuracy of short-term forecast simulations of convective storms, and thereby pose sig- nificant difficulties for weather forecasters. To make a systematic study of the quantitative impacts of each of these sensitivities, a matrix of simulations has been performed using all combinations of eight separate microphysics schemes, three boundary layer schemes, and two sets of initial conditions. The first version of initial conditions consists of the default data from large-scale operational model fields, while the second features specialized higher- resolution soil conditions, vegetation conditions and water surface temperatures derived from datasets created at NASA's Short-term Prediction and Operational Research Tran- sition (SPoRT) Center at the National Space Science and Technology Center (NSSTC) in Huntsville, AL. Simulations as

  13. Correction to "Influence of Dust and Black Carbon on the Snow Albedo in the NASA Goddard Earth Observing System Version 5 Land Surface Model"

    Science.gov (United States)

    Yasunari, Teppei J.; Koster, Randal D.; Kau, K. M.; Aoki, Teruo; Sud, Yogesh C.; Yamazaki, Takeshi; Motoyoshi, Hiroki; Kokdama, Yuji

    2012-01-01

    The website information describing the forcing meteorological data used for the land surface model (LSM) simulation, which were observed at an Automated Meteorological Station CAWS) at the Sapporo District Meteorological Observatory maintained by the Japan Meteorological Agency (JMA), was missing from the text. The 1-hourly data were obtained from the website of Kisyoutoukeijouhou (Information for available JMA-observed meteorological data in the past) on the website of JMA (in Japanese) (available at: http://www.jma.go.jpijmaimenulreport.html). The measurement height information of 59.5 m for the anemometer at the Sapporo Observatory was also obtained from the website of JMA (in Japanese) (available at: http://www.jma.go.jp/jma/menu/report.html). In addition, the converted 10-m wind speed, based on the AWS/JMA data, was further converted to a 2-m wind speed prior to its use with the land model as a usual treatment of off-line Catchment simulation. Please ignore the ice absorption data on the website mentioned in paragraph [15] which was not used for our calculations (but the data on the website was mostly the same as the estimated ice absorption coefficients by the following method because they partially used the same data by Warren [1984]). We calculated the ice absorption coefficients with the method mentioned in the same paragraph, for which some of the refractive index data by Warren [1984] were used and then interpolated between wavelengths, and also mentioned in paragraph [20] for the visible (VIS) and near-infrared (NIR) ranges. The optical data we used were interpolated between wavelengths as necessary.

  14. Variability of soil moisture and its relationship with surface albedo ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 119; Issue 4. Variability of soil moisture and its relationship with surface albedo and soil thermal ... The diurnal variation of surface albedo appears as a U-shaped curve on sunny days. Surface albedo decreases with the increase of solar elevation angle, and it tends ...

  15. Albedo decline on Greenland's Mittivakkat Gletscher in a warming climate

    DEFF Research Database (Denmark)

    Mernild, Sebastian H; Malmros, Jeppe K.; Yde, Jacob Clement

    2015-01-01

    balance year (EBY), MG's AWS observed bare ice albedo reached ∼0.3 only just exceeding values observed for proglacial bedrock (∼0.2). The analysis reveals negative mean trends in the MODIS-derived MG EBY albedo for the period 2000–2013 with a significant decline in mean glacier-wide albedo of 0...

  16. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    Directory of Open Access Journals (Sweden)

    M. M. Helsen

    2017-08-01

    Full Text Available The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB of the Greenland ice sheet (GrIS is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

  17. On the importance of the albedo parameterization for the mass balance of the Greenland ice sheet in EC-Earth

    Science.gov (United States)

    Helsen, Michiel M.; van de Wal, Roderik S. W.; Reerink, Thomas J.; Bintanja, Richard; Madsen, Marianne S.; Yang, Shuting; Li, Qiang; Zhang, Qiong

    2017-08-01

    The albedo of the surface of ice sheets changes as a function of time due to the effects of deposition of new snow, ageing of dry snow, bare ice exposure, melting and run-off. Currently, the calculation of the albedo of ice sheets is highly parameterized within the earth system model EC-Earth by taking a constant value for areas with thick perennial snow cover. This is an important reason why the surface mass balance (SMB) of the Greenland ice sheet (GrIS) is poorly resolved in the model. The purpose of this study is to improve the SMB forcing of the GrIS by evaluating different parameter settings within a snow albedo scheme. By allowing ice-sheet albedo to vary as a function of wet and dry conditions, the spatial distribution of albedo and melt rate improves. Nevertheless, the spatial distribution of SMB in EC-Earth is not significantly improved. As a reason for this, we identify omissions in the current snow albedo scheme, such as separate treatment of snow and ice and the effect of refreezing. The resulting SMB is downscaled from the lower-resolution global climate model topography to the higher-resolution ice-sheet topography of the GrIS, such that the influence of these different SMB climatologies on the long-term evolution of the GrIS is tested by ice-sheet model simulations. From these ice-sheet simulations we conclude that an albedo scheme with a short response time of decaying albedo during wet conditions performs best with respect to long-term simulated ice-sheet volume. This results in an optimized albedo parameterization that can be used in future EC-Earth simulations with an interactive ice-sheet component.

  18. NASA Airborne Snow Observatory: Measuring Spatial Distribution of Snow Water Equivalent and Snow Albedo

    Science.gov (United States)

    Joyce, M.; Painter, T. H.; Bormann, K. J.; Berisford, D. F.; Lai-Norling, J.

    2017-12-01

    The two most critical properties for understanding snowmelt runoff and timing are the spatial and temporal distributions of snow water equivalent (SWE) and snow albedo. Despite their importance in controlling volume and timing of runoff, snowpack albedo and SWE are still largely unquantified in the US and not at all in most of the globe, leaving runoff models poorly constrained. NASA Jet Propulsion Laboratory, in partnership with the California Department of Water Resources, has developed the Airborne Snow Observatory (ASO), an imaging spectrometer and scanning LiDAR system, to quantify SWE and snow albedo, generate unprecedented knowledge of snow properties for cutting edge cryospheric science, and provide complete, robust inputs to water management models and systems of the future. This poster will describe the NASA Airborne Snow Observatory, its outputs and their uses and applications, along with recent advancements to the system and plans for the project's future. Specifically, we will look at how ASO uses its imaging spectrometer to quantify spectral albedo, broadband albedo, and radiative forcing by dust and black carbon in snow. Additionally, we'll see how the scanning LiDAR is used to determine snow depth against snow-free acquisitions and to quantify snow water equivalent when combined with in-situ constrained modeling of snow density.

  19. Proto-planetary nebulae

    International Nuclear Information System (INIS)

    Zuckerman, B.

    1978-01-01

    A 'proto-planetary nebula' or a 'planetary nebula progenitor' is the term used to describe those objects that are losing mass at a rate >approximately 10 -5 Msolar masses/year (i.e. comparable to mass loss rates in planetary nebulae with ionized masses >approximately 0.2 Msolar masses) and which, it is believed, will become planetary nebulae themselves within 5 years. It is shown that most proto-planetary nebulae appear as very red objects although a few have been 'caught' near the middle of the Hertzsprung-Russell diagram. The precursors of these proto-planetaries are the general red giant population, more specifically probably Mira and semi-regular variables. (Auth.)end

  20. Strength of forest-albedo feedback in mid-Holocene climate simulations

    Directory of Open Access Journals (Sweden)

    J. Otto

    2011-09-01

    Full Text Available Reconstructions of the mid-Holocene climate, 6000 years before present, suggest that spring temperatures were higher at high northern latitudes compared to the pre-industrial period. A positive feedback between expansion of forest and climate presumably contributed to this warming. In the presence of snow, forests have a lower albedo than grass land. Therefore, the expansion of forest likely favoured a warming in spring, counteracting the lower insolation at the mid-Holocene.

    We investigate the sensitivity of the vegetation-atmosphere interaction under mid-Holocene orbital forcing with respect to the strength of the forest-albedo feedback by using a comprehensive coupled atmosphere-vegetation model (ECHAM5/JSBACH. We perform two sets of model simulations: a first set of simulations with a relatively weak reduction of albedo of snow by forest; and a second set of simulations with a relatively strong reduction of the albedo of snow by forest.

    We show that the parameterisation of the albedo of snow leads to uncertainties in the temperature signal. Compared to the set with weak snow masking, the simulations with strong snow masking reveal a spring warming that is three times higher, by 0.34 °C north of 60° N. This warming is related to a forest expansion of only 13%.

  1. Chemical Experiments Measuring ph and Gases on "Planetary" Soil by the HUSAR-5 NXT-based Rover Model

    Science.gov (United States)

    Lang, Agota; Bérczi, Szaniszló; Erdélyi, Soma; Nickl, Istvan; Kiss, Daniel; Erdősi, Ferenc; Panyi, Tamas; Szalay, Kristof

    2010-05-01

    program. II: For detecting the gases: We use CZGCO type gas-sensor for the detection of the liberated carbon monoxide or methane. This is a semiconductor based sensor which is heated up to working temperature (ca. 400 °C). The gas is measured as a resistance change signal lead into the NXT. The measured values are observed on the NXT as well as on the "terrestrial control" computer. Construction of the rover in the second mission: the skeleton of the rover was a field-rovering car model. We constructed two arms and a pump from LEGO elements. On the first arm we placed a wireless camera, which could rotate 360°, and also could bend down. The role of the second arm was to stretch and place the indicator ribbon to the surface and move it along a distance to contact with the wet soil. The role of the pump was to pour water on the soil surface. The main idea behind our solution is that water dissolves important chemical components from the soil and the indicator ribbon reports the main chemical characteristics of this chemistry, starting with the pH of the soil. Conclusion: Even the basic experiments can be interesting in the high school's chemistry teaching process if everyday materials are studied. It can be easily connected to planetary surface chemistry, where the soil, the rocks and the atmospheric gases form a common platform with their counterparts on the Earth. Both the experiment and the rover building was a big task for high school students, but they enjoyed the work and learned a lot.

  2. Planetary science: Haze cools Pluto's atmosphere

    Science.gov (United States)

    West, Robert A.

    2017-11-01

    Modelling suggests that Pluto's atmospheric temperature is regulated by haze, unlike the other planetary bodies in the Solar System. The finding has implications for our understanding of exoplanetary atmospheres. See Letter p.352

  3. Planetary Impacts by Clustered Quark Matter Strangelets

    OpenAIRE

    Labun, Lance; Rafelski, Jan

    2011-01-01

    We propose a model of clustered u-d-s quark matter that leads to stable bulk strange quark matter. We discuss qualitatively consequences of impacts by sub-planetary mass strangelets on rocky solar system bodies.

  4. Limb Darkening and Planetary Transits: Testing Center-to-limb Intensity Variations and Limb-darkening Directly from Model Stellar Atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Neilson, Hilding R.; Lester, John B. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); McNeil, Joseph T.; Ignace, Richard, E-mail: neilson@astro.utoronto.ca [Department of Physics and Astronomy, East Tennessee State University, Box 70652, Johnson City, TN 37614 (United States)

    2017-08-10

    The transit method, employed by Microvariability and Oscillation of Stars ( MOST ), Kepler , and various ground-based surveys has enabled the characterization of extrasolar planets to unprecedented precision. These results are precise enough to begin to measure planet atmosphere composition, planetary oblateness, starspots, and other phenomena at the level of a few hundred parts per million. However, these results depend on our understanding of stellar limb darkening, that is, the intensity distribution across the stellar disk that is sequentially blocked as the planet transits. Typically, stellar limb darkening is assumed to be a simple parameterization with two coefficients that are derived from stellar atmosphere models or fit directly. In this work, we revisit this assumption and compute synthetic planetary-transit light curves directly from model stellar atmosphere center-to-limb intensity variations (CLIVs) using the plane-parallel Atlas and spherically symmetric SAtlas codes. We compare these light curves to those constructed using best-fit limb-darkening parameterizations. We find that adopting parametric stellar limb-darkening laws leads to systematic differences from the more geometrically realistic model stellar atmosphere CLIV of about 50–100 ppm at the transit center and up to 300 ppm at ingress/egress. While these errors are small, they are systematic, and they appear to limit the precision necessary to measure secondary effects. Our results may also have a significant impact on transit spectra.

  5. A DETAILED MORPHO-KINEMATIC MODEL OF THE ESKIMO, NGC 2392: A UNIFYING VIEW WITH THE CAT'S EYE AND SATURN PLANETARY NEBULAE

    International Nuclear Information System (INIS)

    García-Díaz, Ma. T.; López, J. A.; Steffen, W.; Richer, M. G.

    2012-01-01

    The three-dimensional and kinematic structure of the Eskimo nebula, NGC 2392, has been notoriously difficult to interpret in detail given its complex morphology, multiple kinematic components and its nearly pole-on orientation along the line of sight. We present a comprehensive, spatially resolved, high-resolution, long-slit spectroscopic mapping of the Eskimo planetary nebula. The data consist of 21 spatially resolved, long-slit echelle spectra tightly spaced over the Eskimo and along its bipolar jets. This data set allows us to construct a velocity-resolved [N II] channel map of the nebula with a resolution of 10 km s –1 that disentangles its different kinematic components. The spectroscopic information is combined with Hubble Space Telescope images to construct a detailed three-dimensional morpho-kinematic model of the Eskimo using the code SHAPE. With this model we demonstrate that the Eskimo is a close analog to the Saturn and the Cat's Eye nebulae, but rotated 90° to the line of sight. Furthermore, we show that the main characteristics of our model apply to the general properties of the group of elliptical planetary nebulae with ansae or FLIERS, once the orientation is considered. We conclude that this kind of nebula belongs to a class with a complex common evolutionary sequence of events.

  6. Evaluation of MuSyQ land surface albedo based on LAnd surface Parameters VAlidation System (LAPVAS)

    Science.gov (United States)

    Dou, B.; Wen, J.; Xinwen, L.; Zhiming, F.; Wu, S.; Zhang, Y.

    2016-12-01

    satellite derived Land surface albedo is an essential climate variable which controls the earth energy budget and it can be used in applications such as climate change, hydrology, and numerical weather prediction. However, the accuracy and uncertainty of surface albedo products should be evaluated with a reliable reference truth data prior to applications. A new comprehensive and systemic project of china, called the Remote Sensing Application Network (CRSAN), has been launched recent years. Two subjects of this project is developing a Multi-source data Synergized Quantitative Remote Sensin g Production System ( MuSyQ ) and a Web-based validation system named LAnd surface remote sensing Product VAlidation System (LAPVAS) , which aims to generate a quantitative remote sensing product for ecosystem and environmental monitoring and validate them with a reference validation data and a standard validation system, respectively. Land surface BRDF/albedo is one of product datasets of MuSyQ which has a pentad period with 1km spatial resolution and is derived by Multi-sensor Combined BRDF Inversion ( MCBI ) Model. In this MuSyQ albedo evaluation, a multi-validation strategy is implemented by LAPVAS, including directly and multi-scale validation with field measured albedo and cross validation with MODIS albedo product with different land cover. The results reveal that MuSyQ albedo data with a 5-day temporal resolution is in higher sensibility and accuracy during land cover change period, e.g. snowing. But results without regard to snow or changed land cover, MuSyQ albedo generally is in similar accuracy with MODIS albedo and meet the climate modeling requirement of an absolute accuracy of 0.05.

  7. Escape from planetary neighbourhoods

    NARCIS (Netherlands)

    Waalkens, H.; Burbanks, A.; Wiggins, S.

    2005-01-01

    In this paper we use recently developed phase-space transport theory coupled with a so-called classical spectral theorem to develop a dynamically exact and computationally efficient procedure for studying escape from a planetary neighbourhood. The ‘planetary neighbourhood’ is a bounded region of

  8. Kinetic and isotherm studies of bisphenol A adsorption onto orange albedo(Citrus sinensis): Sorption mechanisms based on the main albedo components vitamin C, flavones glycosides and carotenoids.

    Science.gov (United States)

    Kamgaing, Theophile; Doungmo, Giscard; Melataguia Tchieno, Francis Merlin; Gouoko Kouonang, Jimmy Julio; Mbadcam, Ketcha Joseph

    2017-07-03

    Orange albedo and its adsorption capacity towards bisphenol A (BPA) were studied. Adsorption experiments were conducted in batch mode at 25-55°C. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy were used to characterise the biosorbent. The effects of various parameters including adsorption time, equilibrium pH, adsorbent dosage and initial adsorbate concentration were investigated. The optimum contact time and pH for the removal of BPA were 60 min and 2, respectively. It was found that the adsorption isotherms best matched the Freundlich model, the adsorption of BPA being multilayer and that of the albedo surface heterogeneous. From the kinetic studies, it was found that the removal of BPA best matched the pseudo-second order kinetic model. An adsorption mechanism based on the albedo surface molecules is proposed and gives a good account of π-π interactions and hydrogen bonding. Orange albedo, with a maximum BPA loading capacity of 82.36 mg g -1 (significantly higher than that of most agricultural residues), is a good candidate for BPA adsorption in aqueous media.

  9. Change in Urban Albedo in London: A Multi-scale Perspective

    Science.gov (United States)

    Susca, T.; Kotthaus, S.; Grimmond, S.

    2013-12-01

    Urbanization-induced change in land use has considerable implications for climate, air quality, resources and ecosystems. Urban-induced warming is one of the most well-known impacts. This directly and indirectly can extend beyond the city. One way to reduce the size of this is to modify the surface atmosphere exchanges through changing the urban albedo. As increased rugosity caused by the morphology of a city results in lower albedo with constant material characteristics, the impacts of changing the albedo has impacts across a range of scales. Here a multi-scale assessment of the potential effects of the increase in albedo in London is presented. This includes modeling at the global and meso-scale informed by local and micro-scale measurements. In this study the first order calculations are conducted for the impact of changing the albedo (e.g. a 0.01 increase) on the radiative exchange. For example, when incoming solar radiation and cloud cover are considered, based on data retrieved from NASA (http://power.larc.nasa.gov/) for ~1600 km2 area of London, would produce a mean decrease in the instantaneous solar radiative forcing on the same surface of 0.40 W m-2. The nature of the surface is critical in terms of considering the impact of changes in albedo. For example, in the Central Activity Zone in London pavement and building can vary from 10 to 100% of the plan area. From observations the albedo is seen to change dramatically with changes in building materials. For example, glass surfaces which are being used increasingly in the central business district results in dramatic changes in albedo. Using the documented albedo variations determined across different scales the impacts are considered. For example, the effect of the increase in urban albedo is translated into the corresponding amount of avoided emission of carbon dioxide that produces the same effect on climate. At local scale, the effect that the increase in urban albedo can potentially have on local

  10. Retrieval of the ultraviolet effective snow albedo during 1998 winter campaign in the French Alps.

    Science.gov (United States)

    Smolskaia, Irina; Masserot, Dominique; Lenoble, Jacqueline; Brogniez, Colette; de la Casinière, Alain

    2003-03-20

    A measurement campaign was carried out in February 1998 at Briançon Station, French Alps (44.9 degrees N, 6.65 degrees E, 1,310 m above sea level) in order to determine the UV effective snow albedo that was retrieved for both erythemal and UV-A irradiances from measurements and modeling enhancement factors. The results are presented for 15 cloudless days with very variable snow cover and a small snowfall in the middle of the campaign. Erythemal irradiance enhancement due to the surface albedo was found to decrease from approximately +15% to +5% with a jump to +22% after the snowfall, whereas UV-A irradiance enhancement decreased from 7% to 5% and increased to 15% after the snowfall. Thesevalues fit to effective surface albedos of 0.4, 0.1, and 0.5 for erythemal, and to effective albedos of 0.25, 0.1, and 0.4 for UV-A irradiances, respectively. An unexpected difference between the effective albedos retrieved in the two wavelength regions can be explained by the difference of the environment contribution.

  11. The Earth's Albedo - The other side to Tyndall's contributions to climate

    Science.gov (United States)

    Stephens, G. L.

    2011-12-01

    Graeme L Stephens Director, Center for Climate Sciences and Juilin Li Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive Mail Stop: 233-300 Pasadena, CA 91109 John Tyndall's contributions to understanding earth's climate are mostly thought of in terms of the planets absorbing gases and the greenhouse effect. However, there is another aspect of his contributions that lie in the so-called Tyndall effect that relates to scattering of sunlight by large particles. Such scattering is an important contribution to Earth's albedo. In the days of Tyndall's foundational work on Earth's greenhouse effect, the Earth's albedo was thought to be about 50%. Satellite observations in the late 1960s and early 1970s however led to a revision downwards to about 30%. Modern satellite observations suggest that more than half of this amount comes from reflection of sunlight by clouds. What is remarkable though is that the planet's albedo is almost invariant over the time of advanced satellite measurements despite large variability of cloudiness that has occurred. Furthermore, model projections imply that the albedo of Earth is not expected to change over the projected course of global warming. Thus a number of fundamental question emerge - why is the planet's albedo so constant, what factors really control its change and are there natural processes that act to buffer those changes expected from changes to clouds and other factor within the atmosphere? This talk will address these questions.

  12. Planetary heat flow measurements.

    Science.gov (United States)

    Hagermann, Axel

    2005-12-15

    The year 2005 marks the 35th anniversary of the Apollo 13 mission, probably the most successful failure in the history of manned spaceflight. Naturally, Apollo 13's scientific payload is far less known than the spectacular accident and subsequent rescue of its crew. Among other instruments, it carried the first instrument designed to measure the flux of heat on a planetary body other than Earth. The year 2005 also should have marked the launch of the Japanese LUNAR-A mission, and ESA's Rosetta mission is slowly approaching comet Churyumov-Gerasimenko. Both missions carry penetrators to study the heat flow from their target bodies. What is so interesting about planetary heat flow? What can we learn from it and how do we measure it?Not only the Sun, but all planets in the Solar System are essentially heat engines. Various heat sources or heat reservoirs drive intrinsic and surface processes, causing 'dead balls of rock, ice or gas' to evolve dynamically over time, driving convection that powers tectonic processes and spawns magnetic fields. The heat flow constrains models of the thermal evolution of a planet and also its composition because it provides an upper limit for the bulk abundance of radioactive elements. On Earth, the global variation of heat flow also reflects the tectonic activity: heat flow increases towards the young ocean ridges, whereas it is rather low on the old continental shields. It is not surprising that surface heat flow measurements, or even estimates, where performed, contributed greatly to our understanding of what happens inside the planets. In this article, I will review the results and the methods used in past heat flow measurements and speculate on the targets and design of future experiments.

  13. MODIS/Terra+Aqua BRDF/Albedo Black Sky Albedo Shortwave Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D51 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Black Sky Albedo near shortwave broadband data set is a daily 16-day...

  14. MODIS/Terra+Aqua BRDF/Albedo Black Sky Albedo VIS Daily L3 Global 30ArcSec CMG V006

    Data.gov (United States)

    National Aeronautics and Space Administration — The MCD43D49 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Black Sky Albedo visible broadband data set is a daily 16-day...

  15. Spatially Complete Global Surface Albedos Derived from Terra/MODIS Data

    Science.gov (United States)

    King, Michael D.; Moody, Eric G.; Schaaf, Crystal B.; Platnick, Steven

    2006-01-01

    Spectral land surface albedo is an important parameter for describing the radiative properties of the Earth. Accordingly it reflects the consequences of natural and human interactions, such as anthropogenic, meteorological, and phenological effects, on global and local climatological trends. Consequently, albedos are integral parts in a variety of research areas, such as general circulation models (GCMs), energy balance studies, modeling of land use and land use change, and biophysical, oceanographic, and meteorological studies. , Over five years of land surface anisotropy, diffuse bihemispherical (white-sky) albedo and direct beam directional hemispherical (black-sky) albedo from observations acquired by the MODIS instruments aboard NASA s Terra and Aqua satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal information on the land surface s radiative characteristics. However, roughly 30% of the global land surface, on an annual equal-angle basis, is obscured due to persistent and transient cloud cover, while another 207% is obscured due to ephemeral and seasonal snow effects. This precludes the MOD43B3 albedo products from being directly used in some remote sensing and ground-based applications, climate models, and global change research projects. To provide researchers with the requisite spatially complete global snow-free land surface albedo dataset, an ecosystem-dependent temporal interpolation technique was developed to fill missing or lower quality data and snow covered values from the official MOD43B3 dataset with geophysically realistic values. The method imposes pixel-level and local regional ecosystem-dependent phenological behavior onto retrieved pixel temporal data in such a way as to maintain pixel-level spatial and spectral detail and integrity. The phenological curves are derived from statistics based on the MODIS MOD12Q1 IGBP land cover classification product geolocated with the MOD43B3 data.

  16. Bipolar high temporal resolution measurements of snow UV albedo in Sodankylä and Marambio

    Science.gov (United States)

    Meinander, Outi; Kontu, Anna; Asmi, Eija; Sanchez, Ricardo; Mei, Miguel; de Leeuw, Gerrit

    2015-04-01

    In this presentation we will give an overview of our high temporal resolution polar snow UV albedo data from Arctic Sodankylä, and from Marambio, Antarctica. These both are WMO GAW stations with many measurement parameters relevant to the albedo data usage. We will also describe our campaign based polar albedo data (SNORTEX and SOS campaigns), and an important data set of light absorbing impurities (BC) in the Arctic snow. The black carbon (BC) has been estimated to be the second most important human emission after carbon dioxide, in terms of its climate forcing in the present-day atmosphere. The reflectance effect of BC deposited on snow surface is the bigger the smaller the wavelength, i.e. the albedo effect of BC is the biggest at UV. This is also shown in SNICAR-model simulated albedo values. In Sodankylä, our bipolar snow ultraviolet (UV) albedo research started within the International Polar Year (IPY) 2007-2008. In 2007, the continuous Sodankylä snow UV albedo measurements were installed in Sodankylä, in the operational albedo field of the Finnish Meteorological Institute Arctic Research Center (FMI-ARC). These Sodankylä 1-min data during snow time were soon compared with the German Antarctic Neumayer Station UV albedo data, also with the same sensor type. In both data we found an up to 10 % decrease in albedo as a function of time within a day, ranging from 0.77 to 0.67 in Sodankylä and from 0.96 to 0.86 in Neumeyer. Physical explanations to asymmetry were found for cases with high relative humidity and low surface temperature during the previous night, favorable to frost and higher albedo on the next morning; new snow on the previous night; snow melting during day time and refreezing during night. In Marambio, in the beginning of 2013, our new continuous Finnish-Argentinian co-operation snow UV albedo measurements were installed and started as part of a larger continuous meteorological and environmental instrumentation. These new UV radiation data

  17. Snow and albedo climate change impacts across the United States Northern Great Plains

    Science.gov (United States)

    Fassnacht, S. R.; Cherry, M. L.; Venable, N. B. H.; Saavedra, F.

    2016-02-01

    In areas with a seasonal snowpack, a warmer climate could cause less snowfall, a shallower snowpack, and a change in the timing of snowmelt, all which could reduce the winter albedo and yield an increase in net short-wave radiation. Trends in temperature, precipitation (total and as snow), days with precipitation and snow, and winter albedo were investigated over the 60-year period from 1951 to 2010 for 20 meteorological stations across the Northern Great Plains. This is an area where snow accumulation is shallow but persistent for most of the winter (November to March). The most consistent trends were minimum temperature and days with precipitation, both of which increased at a majority of the stations. Among the stations included, a decrease in the modelled winter albedo was more prevalent than an increase. There was substantial spatial variability in the climate trends. For most variables, the period of record used influenced the magnitude and sign of the significant trends.

  18. Approximate albedo boundary conditions for energy multigroup X,Y-geometry discrete ordinates nuclear global calculations

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Davi J.M.; Nunes, Carlos E.A.; Alves Filho, Hermes; Barros, Ricardo C., E-mail: davijmsilva@yahoo.com.br, E-mail: ceanunes@yahoo.com.br, E-mail: rcbarros@pq.cnpq.br [Secretaria Municipal de Educacao de Itaborai, RJ (Brazil); Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Universidade do Estado do Rio de Janeiro (UERJ), Novra Friburgo, RJ (Brazil). Instituto Politecnico. Departamento de Modelagem Computacional

    2017-11-01

    Discussed here is the accuracy of approximate albedo boundary conditions for energy multigroup discrete ordinates (S{sub N}) eigenvalue problems in two-dimensional rectangular geometry for criticality calculations in neutron fission reacting systems, such as nuclear reactors. The multigroup (S{sub N}) albedo matrix substitutes approximately the non-multiplying media around the core, e.g., baffle and reflector, as we neglect the transverse leakage terms within these non-multiplying regions. Numerical results to a typical model problem are given to illustrate the accuracy versus the computer running time. (author)

  19. Stream Lifetimes Against Planetary Encounters

    Science.gov (United States)

    Valsecchi, G. B.; Lega, E.; Froeschle, Cl.

    2011-01-01

    We study, both analytically and numerically, the perturbation induced by an encounter with a planet on a meteoroid stream. Our analytical tool is the extension of pik s theory of close encounters, that we apply to streams described by geocentric variables. The resulting formulae are used to compute the rate at which a stream is dispersed by planetary encounters into the sporadic background. We have verified the accuracy of the analytical model using a numerical test.

  20. Planetary Geophysics and Tectonics

    Science.gov (United States)

    Zuber, Maria

    2005-01-01

    The broad objective of this work is to improve understanding of the internal structures and thermal and stress histories of the solid planets by combining results from analytical and computational modeling, and geophysical data analysis of gravity, topography and tectonic surface structures. During the past year we performed two quite independent studies in the attempt to explain the Mariner 10 magnetic observations of Mercury. In the first we revisited the possibility of crustal remanence by studying the conditions under which one could break symmetry inherent in Runcorn's model of a uniformly magnetized shell to produce a remanent signal with a dipolar form. In the second we applied a thin shell dynamo model to evaluate the range of intensity/structure for which such a planetary configuration can produce a dipole field consistent with Mariner 10 results. In the next full proposal cycle we will: (1) develop numerical and analytical and models of thin shell dynamos to address the possible nature of Mercury s present-day magnetic field and the demise of Mars magnetic field; (2) study the effect of degree-1 mantle convection on a core dynamo as relevant to the early magnetic field of Mars; (3) develop models of how the deep mantles of terrestrial planets are perturbed by large impacts and address the consequences for mantle evolution; (4) study the structure, compensation, state of stress, and viscous relaxation of lunar basins, and address implications for the Moon s state of stress and thermal history by modeling and gravity/topography analysis; and (5) use a three-dimensional viscous relaxation model for a planet with generalized vertical viscosity distribution to study the degree-two components of the Moon's topography and gravity fields to constrain the primordial stress state and spatial heterogeneity of the crust and mantle.

  1. Effects of illumination differences on photometric stereo shape-and-albedo-from-shading for precision lunar surface reconstruction

    Science.gov (United States)

    Chung Liu, Wai; Wu, Bo; Wöhler, Christian

    2018-02-01

    Photoclinometric surface reconstruction techniques such as Shape-from-Shading (SfS) and Shape-and-Albedo-from-Shading (SAfS) retrieve topographic information of a surface on the basis of the reflectance information embedded in the image intensity of each pixel. SfS or SAfS techniques have been utilized to generate pixel-resolution digital elevation models (DEMs) of the Moon and other planetary bodies. Photometric stereo SAfS analyzes images under multiple illumination conditions to improve the robustness of reconstruction. In this case, the directional difference in illumination between the images is likely to affect the quality of the reconstruction result. In this study, we quantitatively investigate the effects of illumination differences on photometric stereo SAfS. Firstly, an algorithm for photometric stereo SAfS is developed, and then, an error model is derived to analyze the relationships between the azimuthal and zenith angles of illumination of the images and the reconstruction qualities. The developed algorithm and error model were verified with high-resolution images collected by the Narrow Angle Camera (NAC) of the Lunar Reconnaissance Orbiter Camera (LROC). Experimental analyses reveal that (1) the resulting error in photometric stereo SAfS depends on both the azimuthal and the zenith angles of illumination as well as the general intensity of the images and (2) the predictions from the proposed error model are consistent with the actual slope errors obtained by photometric stereo SAfS using the LROC NAC images. The proposed error model enriches the theory of photometric stereo SAfS and is of significance for optimized lunar surface reconstruction based on SAfS techniques.

  2. Iapetus: Tenth Anniversary of the Cassini Flyby and the Albedo Dichotomy Enigma

    Science.gov (United States)

    Denk, Tilmann

    2017-10-01

    Ten years ago, on 10 Sep 2007, Cassini (the spacecraft) performed the only targeted flyby of Saturn's outermost regular moon Iapetus and came as close as 1620 km to its surface [1]. Cassini approached Iapetus over the unlit low-albedo leading hemisphere, flew over the ridge on the anti-Saturn side during closest approach, and departed over the illuminated bright trailing side. This flyby was different in many aspects to all other satellite flybys of Cassini. For example, it occured near apoapsis of the spacecraft orbit, and the flyby velocity was much lower than ususal, allowing for an unusually intensive observing program. There was also a major change in the sub-spacecraft groundtrack implemented in 2006 primarily because of the discovery of the equatorial ridge in late 2004. Unexpected (and unpleasant) events like a spacecraft safing occuring just about 15 min after data playback start are also part of the story.Iapetus was originally discovered by Cassini (the man) in 1671, and only six years later, he published a paper where he correctly described the albedo dichotomy that Iapetus is famous for [2]. Over the following ~300 years, no progress was made with regard to the cause of this phenomenon. Since the 1970s, numerous ideas have been published, but all shared the common property of not being widely accepted. One of the top science tasks for Cassini (the spacecraft) to solve was this enigma which was among the oldest unresolved questions in planetary sciences.The talk recaps the efforts to explain the albedo dichotomy [3] and gives an overview of the Cassini Iapetus observation planning and execution with an emphasis on the 2007 targeted flyby.As a final sidenote, the monolith from Arthur Clarke's novel "2001 - A Space Odyssey" [4] was not detected in the images.[1] Denk, T. (2008): Cassini at Iapetus: A Bumpy but Successful Flyby. The Planetary Report, Vol. XXVIII, no. 1, pp. 10-16, Jan/Feb 2008.[2] Cassini, J.D. (1677): Some New Observations Made by Sig

  3. Planetary Landscape Geography

    Science.gov (United States)

    Hargitai, H.

    hydrosphere (no erosion). Adding new elements (differentiated body: horizon, atmosphere: blue/purple etc sky as visually important elements; complex lithology (mountains of tectonic ori- gin); atmosphere (which can alter temperature) and hydrosphere (erosion, rivers, de- position) a more complex landscape will appear. As a first step, by making a "landscape model", we can input general parameters of atmosphere, lithosphere, hydrosphere, biosphere, the distance from the Sun, orbital parameters, last resurfacing date, age of the planet and the model will output the pos- 1 sible landscape elements in the planet. This can be refined by inputing the actual pa- rameters (place on planet, climate region etc.) from which the actual landscape can be the result. The landscape altering processes are: exogenic (impact), mass movement, endogenic (volcanism, thermal conditions), weathering, aeolic, fluvial, glacial, biogenic, antro- pogenic processes. Comparing planets and moons, all of these processes work on Earth, only half of them works on Mars and Venus, and even fewer on Mercury and Moon [3], where most of the surface is an "post-impact" landscape. A Planetary view. Science-fiction writers often describe planets with one characteris- tic: "desert planet", "ocean planet", "forest planet". Generally, planetary flyby missions verify these images (Europa - ice plain planet or Io - volcano world), but a orbiter mis- sion makes clear than in any planet, several significantly different landcape units are present, but from planet to planet, the average climatic and lithologic conditions do change and characterize the given planet. LANDSCAPE RESOURCES, LANDSCAPE "HOT SPOTS" Landscape hot spots has "high values" in the factors listed below. Physical landscape values. Small object not detectable from orbiters: individual rocks or the local physical characteristics of the upper layer of the regolith, the sediment or bedrock characteristics along with relief forms will be the important factors of

  4. Albedo of the ice covered Weddell and Bellingshausen Seas

    OpenAIRE

    Weiss, A. I.; King, J. C.; Lachlan-Cope, T. A.; Ladkin, R. S.

    2012-01-01

    This study investigates the surface albedo of the sea ice areas adjacent to the Antarctic Peninsula during the austral summer. Aircraft measurements of the surface albedo, which were conducted in the sea ice areas of the Weddell and Bellingshausen Seas show significant differences between these two regions. The averaged surface albedo varied between 0.13 and 0.81. The ice cover of the Bellingshausen Sea consisted mainly of first year ice and the sea surface showed an averaged sea ice albedo o...

  5. Measurements of spectral snow albedo at Neumayer, Antarctica

    OpenAIRE

    Wuttke Sigrid; Seckmeyer G; König-Langlo Gert

    2006-01-01

    Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W) during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional...

  6. LUNAR TERRAIN AND ALBEDO RECONSTRUCTION FROM APOLLO IMAGERY

    Data.gov (United States)

    National Aeronautics and Space Administration — LUNAR TERRAIN AND ALBEDO RECONSTRUCTION FROM APOLLO IMAGERY ARA V NEFIAN*, TAEMIN KIM, MICHAEL BROXTON, AND ZACH MORATTO Abstract. Generating accurate three...

  7. The role of albedo and accumulation in the 2010 melting record in Greenland

    NARCIS (Netherlands)

    Tedesco, M.; Fettweis, X.; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; van de Wal, R.S.W.|info:eu-repo/dai/nl/101899556; Smeets, C.J.P.P.|info:eu-repo/dai/nl/191522236; van de Berg, W.J.|info:eu-repo/dai/nl/304831611; Serreze, M.C.; Box, J.E.

    2011-01-01

    Analyses of remote sensing data, surface observations and output from a regional atmosphere model point to new records in 2010 for surface melt and albedo, runoff, the number of days when bare ice is exposed and surface mass balance of the Greenland ice sheet, especially over its west and southwest

  8. Mars seasonal CO2 ice lifetimes and the angular dependence of albedo

    Science.gov (United States)

    Lindner, Bernhard Lee

    1992-01-01

    The albedo of the polar caps on Mars brightens appreciably at high solar zenith angle (Warren et al., J. Geophys. Res., 95, 14717, 1990), an effect not included in prior polar-cap energy-balance models. This decreases absorption of sunlight by the polar cap, hence decreasing sublimation of CO2 ice. Lindner (J. Geophys. Res., 95, 1367, 1990) has shown that the radiative effects of clouds and airborne dust will increase sublimation of CO2 ice over that predicted by prior polar-cap energy-balance models. Furthermore, observations hint that more clouds may exist in the Northern Hemisphere, which Lindner (1990) has shown would sublime CO2 ice more quickly in the north than in the south. I show here that the effects of the solar zenith angle dependence of albedo and the radiative effects of clouds and dust offset each other, but act to extend the lifetime of CO2 ice on the south pole more than on the north pole, possibly explaining the observed hemispherical asymmetry in the residual polar caps without the need of a hemispherical asymmetry in polar-cap albedo required by prior models. Another positive aspect of this solution is that neither the inclusion of the solar zenith angle dependence of albedo nor the radiative effects of clouds and dust should appreciably change prior model agreement with observations of the annual cycle of surface pressure and the recession of the polar caps equatorward of 75 degrees latitude.

  9. Calibration of an ALBEDO termoluminiscent dosimeter for its use in personal dosimetry

    International Nuclear Information System (INIS)

    Diaz Bernal, E.; Molina Perez, D.; Cornejo Diaz, N.; Carrazana Gonzalez, J.

    1996-01-01

    The dosimetric studies began after the Radiological Individuals Surveillance Department from the Radiation Protection and Hygiene Center acquired the albedo thermoluminescent dosimeters model JR1104. This paper reviews the response of those dosimeters to the different spectrums and incidence angles of neutronic radiation

  10. From red giants to planetary nebulae: Asymmetries, dust, and polarization

    International Nuclear Information System (INIS)

    Johnson, J.J.

    1990-01-01

    In order to investigate the development of aspherical planetary nebulae, polarimetry was obtained for a group of planetary nebulae and for objects that will evolve into planetary nebulae, i.e., red giants, late asymptotic giant branch (AGB) objects, proto-planetary nebulae, and young planetary nebulae. To study the dust around the objects in our sample, we also used data from the Infrared Astronomy Satellite (IRAS) mission. The youngest objects in our survey, red giants, had the hottest dust temperatures while planetary nebulae had the coolest. Most of the objects were intrinsically polarized, including the red giants. This indicated that the circumstellar dust shells of these objects were aspherical. Both carbon- and oxygen-rich objects could be intrinsically polarized. The intrinsic polarizations of a sample of our objects were modeled using an ellipsoidal circumstellar dust shell. The findings of this study suggest that the asphericities that lead to an aspherical planetary nebula originate when a red giant begins to undergo mass loss. The polarization and thus the asphericity as the star evolves, with both reaching a maximum during the proto-planetary nebula stage. The circumstellar dust shell will dissipate after the proto-planetary nebulae stage since no new material is being added. The polarization of planetary nebulae will thus be low. In the most evolved planetary nebulae, the dust has either been destroyed or dissipated into the interstellar medium. In these objects no polarization was observed

  11. Measurements of light-absorbing particles in snow across the Arctic, North America, and China: Effects on surface albedo

    Science.gov (United States)

    Dang, Cheng; Warren, Stephen G.; Fu, Qiang; Doherty, Sarah J.; Sturm, Matthew; Su, Jing

    2017-10-01

    Using field observations, we perform radiative transfer calculations on snowpacks in the Arctic, China, and North America to quantify the impact of light-absorbing particles (LAPs) on snow albedo and its sensitivity to different factors. For new snow, the regional-averaged albedo reductions caused by all LAPs in the Arctic, North America, and China are 0.009, 0.012, and 0.077, respectively, of which the albedo reductions caused by black carbon (BC) alone are 0.005, 0.005, and 0.031, corresponding to a positive radiative forcing of 0.06, 0.3, and 3 W m-2. For the same particulate concentrations, the albedo reduction for old melting snow is larger than that of new snow by a factor of 2; this leads to 3-8 times larger radiative forcing, in part due to higher solar irradiance in the melting season. These calculations used ambient snowpack properties; if all snowpacks were instead assumed to be optically thick, the albedo reduction would be 20-50% larger for new snow in the Arctic and North America and 120-300% larger for old snow. Accounting for non-BC LAPs reduces the albedo reduction by BC in the Arctic, North America, and China by 32%, 29%, and 70%, respectively, for new snow and 11%, 7%, and 51% for old snow. BC-in-snow albedo reduction computed using a two-layer model agrees reasonably with that computed using a multilayer model. Biases in BC concentration or snow depth often lead to nonlinear biases in BC-induced albedo reduction.

  12. The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

    Directory of Open Access Journals (Sweden)

    F. S. E. Vamborg

    2011-02-01

    Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr−1 for the pre-industrial simulation and by about 80 mm yr−1 for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

  13. Gazetteer of Planetary Nomenclature

    Data.gov (United States)

    National Aeronautics and Space Administration — Planetary nomenclature, like terrestrial nomenclature, is used to uniquely identify a feature on the surface of a planet or satellite so that the feature can be...

  14. Evolution of planetary nebula nuclei

    International Nuclear Information System (INIS)

    Shaw, R.A.

    1985-01-01

    The evolution of planetary nebula nuclei (PNNs) is examined with the aid of the most recent available stellar evolution calculations and new observations of these objects. Their expected distribution in the log L-log T plane is calculated based upon the stellar evolutionary models of Paczynski, Schoenberner and Iben, the initial mass function derived by Miller and Scalo, and various assumptions concerning mass loss during post-main sequence evolution. The distribution is found to be insensitive both to the assumed range of main-sequence progenitor mass and to reasonable variations in the age and the star forming history of the galactic disk. Rather, the distribution is determined by the strong dependence of the rate of stellar evolution upon core mass, the steepness of the initial mass function, and to a lesser extent the finite lifetime of an observable planetary nebula. The theoretical distributions are rather different than any of those inferred from earlier observations. Possible observational selection effects that may be responsible are examined, as well as the intrinsic uncertainties associated with the theoretical model predictions. An extensive photometric and smaller photographic survey of southern hemisphere planetary nebulae (PNs) is presented

  15. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    OpenAIRE

    Y. Liu; W. Wu; M. P. Jensen; T. Toto

    2011-01-01

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surfaced-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fractio...

  16. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    OpenAIRE

    Y. Liu; W. Wu; M. P. Jensen; T. Toto

    2011-01-01

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction...

  17. Assessment of Planetary-Boundary-Layer Schemes in the Weather Research and Forecasting Model Within and Above an Urban Canopy Layer

    Science.gov (United States)

    Ferrero, Enrico; Alessandrini, Stefano; Vandenberghe, Francois

    2018-03-01

    We tested several planetary-boundary-layer (PBL) schemes available in the Weather Research and Forecasting (WRF) model against measured wind speed and direction, temperature and turbulent kinetic energy (TKE) at three levels (5, 9, 25 m). The Urban Turbulence Project dataset, gathered from the outskirts of Turin, Italy and used for the comparison, provides measurements made by sonic anemometers for more than 1 year. In contrast to other similar studies, which have mainly focused on short-time periods, we considered 2 months of measurements (January and July) representing both the seasonal and the daily variabilities. To understand how the WRF-model PBL schemes perform in an urban environment, often characterized by low wind-speed conditions, we first compared six PBL schemes against observations taken by the highest anemometer located in the inertial sub-layer. The availability of the TKE measurements allows us to directly evaluate the performances of the model; results of the model evaluation are presented in terms of quantile versus quantile plots and statistical indices. Secondly, we considered WRF-model PBL schemes that can be coupled to the urban-surface exchange parametrizations and compared the simulation results with measurements from the two lower anemometers located inside the canopy layer. We find that the PBL schemes accounting for TKE are more accurate and the model representation of the roughness sub-layer improves when the urban model is coupled to each PBL scheme.

  18. An Algorithm for the Retrieval of 30-m Snow-Free Albedo from Landsat Surface Reflectance and MODIS BRDF

    Science.gov (United States)

    Shuai, Yanmin; Masek, Jeffrey G.; Gao, Feng; Schaaf, Crystal B.

    2011-01-01

    We present a new methodology to generate 30-m resolution land surface albedo using Landsat surface reflectance and anisotropy information from concurrent MODIS 500-m observations. Albedo information at fine spatial resolution is particularly useful for quantifying climate impacts associated with land use change and ecosystem disturbance. The derived white-sky and black-sky spectral albedos maybe used to estimate actual spectral albedos by taking into account the proportion of direct and diffuse solar radiation arriving at the ground. A further spectral-to-broadband conversion based on extensive radiative transfer simulations is applied to produce the broadband albedos at visible, near infrared, and shortwave regimes. The accuracy of this approach has been evaluated using 270 Landsat scenes covering six field stations supported by the SURFace RADiation Budget Network (SURFRAD) and Atmospheric Radiation Measurement Southern Great Plains (ARM/SGP) network. Comparison with field measurements shows that Landsat 30-m snow-free shortwave albedos from all seasons generally achieve an absolute accuracy of +/-0.02 - 0.05 for these validation sites during available clear days in 2003-2005,with a root mean square error less than 0.03 and a bias less than 0.02. This level of accuracy has been regarded as sufficient for driving global and regional climate models. The Landsat-based retrievals have also been compared to the operational 16-day MODIS albedo produced every 8-days from MODIS on Terra and Aqua (MCD43A). The Landsat albedo provides more detailed landscape texture, and achieves better agreement (correlation and dynamic range) with in-situ data at the validation stations, particularly when the stations include a heterogeneous mix of surface covers.

  19. Global Climate Forcing from Albedo Change Caused by Large-scale Deforestation and Reforestation: Quantification and Attribution of Geographic Variation

    Science.gov (United States)

    Jiao, Tong; Williams, Christopher A.; Ghimire, Bardan; Masek, Jeffrey; Gao, Feng; Schaaf, Crystal

    2017-01-01

    Large-scale deforestation and reforestation have contributed substantially to historical and contemporary global climate change in part through albedo-induced radiative forcing, with meaningful implications for forest management aiming to mitigate climate change. Associated warming or cooling varies widely across the globe due to a range of factors including forest type, snow cover, and insolation, but resulting geographic variation remain spoorly described and has been largely based on model assessments. This study provides an observation-based approach to quantify local and global radiative forcings from large-scale deforestation and reforestation and further examines mechanisms that result in the spatial heterogeneity of radiative forcing. We incorporate a new spatially and temporally explicit land cover-specific albedo product derived from Moderate Resolution Imaging Spectroradiometer with a historical land use data set (Land Use Harmonization product). Spatial variation in radiative forcing was attributed to four mechanisms, including the change in snow-covered albedo, change in snow-free albedo, snow cover fraction, and incoming solar radiation. We find an albedo-only radiative forcing (RF) of -0.819 W m(exp -2) if year 2000 forests were completely deforested and converted to croplands. Albedo RF from global reforestation of present-day croplands to recover year 1700 forests is estimated to be 0.161 W m)exp -2). Snow-cover fraction is identified as the primary factor in determining the spatial variation of radiative forcing in winter, while the magnitude of the change in snow-free albedo is the primary factor determining variations in summertime RF. Findings reinforce the notion that, for conifers at the snowier high latitudes, albedo RF diminishes the warming from forest loss and the cooling from forest gain more so than for other forest types, latitudes, and climate settings.

  20. ALBEDO PROPERTIES OF MAIN BELT ASTEROIDS BASED ON THE ALL-SKY SURVEY OF THE INFRARED ASTRONOMICAL SATELLITE AKARI

    Energy Technology Data Exchange (ETDEWEB)

    Usui, Fumihiko; Hasegawa, Sunao; Matsuhara, Hideo [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210 (Japan); Kasuga, Toshihiro [Public Relations Center, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, San 56-1, Shillim-dong Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata-cho, Asakuchi, Okayama 719-0232 (Japan); Mueller, Thomas G. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Ootsubo, Takafumi, E-mail: usui@ir.isas.jaxa.jp [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578 (Japan)

    2013-01-01

    We present an analysis of the albedo properties of main belt asteroids (MBAs) detected by the All-Sky Survey of the infrared astronomical satellite AKARI. The characteristics of 5120 asteroids detected by the survey, including their sizes and albedos, were cataloged in the Asteroid Catalog Using AKARI (AcuA). Size and albedo measurements were based on the standard thermal model, using inputs of infrared fluxes and absolute magnitudes measured at optical wavelengths. MBAs, which account for 4722 of the 5120 AcuA asteroids, have semimajor axes of 2.06-3.27 AU, except for the near-Earth asteroids. AcuA provides a complete data set of all MBAs brighter than the absolute magnitude of H < 10.3, which corresponds to the diameter of d > 20 km. We confirmed that the albedo distribution of the MBAs is strongly bimodal as was already known from the past observations, and that the bimodal distribution occurs not only in the total population, but also within inner, middle, and outer regions of the main belt. The bimodal distribution in each group consists of low-albedo components in C-type asteroids and high-albedo components in S-type asteroids. We found that the small asteroids have much more variety in albedo than the large asteroids. In spite of the albedo transition process like space weathering, the heliocentric distribution of the mean albedo of asteroids in each taxonomic type is nearly flat. The mean albedo of the total, on the other hand, gradually decreases with an increase in semimajor axis. This can be explained by the compositional ratio of taxonomic types; that is, the proportion of dark asteroids such as C- and D-types increases, while that of bright asteroids such as S-type decreases, with increasing heliocentric distance. The heliocentric distributions of X-subclasses: E-, M-, and P-types, which can be divided based on albedo values, are also examined. P-types, which are the major component in X-types, are distributed throughout the main belt regions, and the

  1. Snow driven Radiative Forcing in High Latitude Areas of Disturbance Using Higher Resolution Albedo Products from Landsat and Sentinel-2

    Science.gov (United States)

    Erb, A.; Li, Z.; Schaaf, C.; Wang, Z.; Rogers, B. M.

    2017-12-01

    Land surface albedo plays an important role in the surface energy budget and radiative forcing by determining the proportion of absorbed incoming solar radiation available to drive photosynthesis and surface heating. In Arctic regions, albedo is particularly sensitive to land cover and land use change (LCLUC) and modeling efforts have shown it to be the primary driver of effective radiative forcing from the biogeophysical effects of LCLUC. In boreal forests, the effects of these changes are complicated during snow covered periods when newly exposed, highly reflective snow can serve as the primary driver of radiative forcing. In Arctic biomes disturbance scars from fire, pest and harvest can remain in the landscape for long periods of time. As such, understanding the magnitude and persistence of these disturbances, especially in the shoulder seasons, is critical. The Landsat and Sentinel-2 Albedo Products couple 30m and 20m surface reflectances with concurrent 500m BRDF Products from the MODerate resolution Imaging Spectroradiometer (MODIS). The 12 bit radiometric fidelity of Sentinel-2 and Landsat-8 allow for the inclusion of high-quality, unsaturated albedo calculations over snow covered surfaces at scales more compatible with fragmented landscapes. Recent work on the early spring albedo of fire scars has illustrated significant post-fire spatial heterogeneity of burn severity at the landscape scale and highlights the need for a finer spatial resolution albedo record. The increased temporal resolution provided by multiple satellite instruments also allows for a better understanding of albedo dynamics during the dynamic shoulder seasons and in historically difficult high latitude locations where persistent cloud cover limits high quality retrievals. Here we present how changes in the early spring albedo of recent boreal forest disturbance in Alaska and central Canada affects landscape-scale radiative forcing. We take advantage of the long historical Landsat record

  2. Neither Dust Nor Black Carbon Causing Apparent Albedo Decline in Greenland's Dry Snow Zone; Uncorrected Sensor Degradation Impacting MODIS C5 Results

    Science.gov (United States)

    Polashenski, C.; Dibb, J. E.; Flanner, M.; Chen, J.; Courville, Z.; Lai, A.; Schauer, J. J.; Shafer, M. M.; Bergin, M. H.

    2015-12-01

    Observations suggest the Greenland ice sheet albedo has declined since 2001, even in the dry snow zone (DSZ). We seek to explain the apparent DSZ albedo decline. We analyze samples representing 2012-2014 snowfall across NW Greenland for absorbing impurities (black carbon and dust) and model their impacts on snow albedo. Albedo reductions due to absorbing impurities are small, averaging 0.003, with episodic enhancements resulting in reductions of 0.01-0.02. No significant increase in black carbon or dust concentrations relative to recent decades is indicated. Enhanced deposition of absorbing impurities is not, therefore, causing significant albedo reduction in the DSZ or driving recent melt events. Analysis of MODIS surface reflectance indicates that the decline and spectral shift in DSZ albedo seen in C5 MODIS data contains contributions from uncorrected Terra sensor degradation. The discrepancies between Terra and Aqua are generally below the stated accuracy of MODIS products (0.05), but since discussions of Greenland albedo trends below this level are common in the literature, the identification of these discrepancies likely requires revisiting conclusions about the trends and spectral signature of Greenland DSZ albedo after C6 data is released.

  3. Land Surface Albedo From EPS/AVHRR : Method For Retrieval and Validation

    Science.gov (United States)

    Jacob, G.

    2015-12-01

    The scope of Land Surface Analysis Satellite Applications Facility (LSA-SAF) is to increase benefit from EUMETSAT Satellites (MSG and EPS) data by providing added value products for the meteorological and environmental science communities with main applications in the fields of climate modelling, environmental management, natural hazards management, and climate change detection. The MSG/SEVIRI daily albedo product is disseminated operationally by the LSA-SAF processing centre based in Portugal since 2009. This product so-called MDAL covers Europe and Africa includes in the visible, near infrared and shortwave bands at a resolution of 3km at the equator. Recently, an albedo product at 1km so-called ETAL has been built from EPS/AVHRR observations in order to primarily MDAL product outside the MSG disk, while ensuring a global coverage. The methodology is common to MSG and EPS data and relies on the inversion of the BRDF (Bidirectional Reflectance Distribution Function) model of Roujean et al. On a given target, ETAL products exploits the variability of viewing angles whereas MDAL looks at the variations of solar illumination. The comparison of ETAL albedo product against MODIS and MSG/SEVIRI products over the year 2015 is instructive in many ways and shows in general a good agreement between them. The dispersion may be accounted by different factors that will be explained The additional information provided by EPS appears to be particularly beneficial for high latitudes during winter and for snow albedo.

  4. Planetary Image Geometry Library

    Science.gov (United States)

    Deen, Robert C.; Pariser, Oleg

    2010-01-01

    The Planetary Image Geometry (PIG) library is a multi-mission library used for projecting images (EDRs, or Experiment Data Records) and managing their geometry for in-situ missions. A collection of models describes cameras and their articulation, allowing application programs such as mosaickers, terrain generators, and pointing correction tools to be written in a multi-mission manner, without any knowledge of parameters specific to the supported missions. Camera model objects allow transformation of image coordinates to and from view vectors in XYZ space. Pointing models, specific to each mission, describe how to orient the camera models based on telemetry or other information. Surface models describe the surface in general terms. Coordinate system objects manage the various coordinate systems involved in most missions. File objects manage access to metadata (labels, including telemetry information) in the input EDRs and RDRs (Reduced Data Records). Label models manage metadata information in output files. Site objects keep track of different locations where the spacecraft might be at a given time. Radiometry models allow correction of radiometry for an image. Mission objects contain basic mission parameters. Pointing adjustment ("nav") files allow pointing to be corrected. The object-oriented structure (C++) makes it easy to subclass just the pieces of the library that are truly mission-specific. Typically, this involves just the pointing model and coordinate systems, and parts of the file model. Once the library was developed (initially for Mars Polar Lander, MPL), adding new missions ranged from two days to a few months, resulting in significant cost savings as compared to rewriting all the application programs for each mission. Currently supported missions include Mars Pathfinder (MPF), MPL, Mars Exploration Rover (MER), Phoenix, and Mars Science Lab (MSL). Applications based on this library create the majority of operational image RDRs for those missions. A

  5. Variability of soil moisture and its relationship with surface albedo ...

    Indian Academy of Sciences (India)

    30 N latitude) are used to study the diurnal, monthly and seasonal soil moisture variations. The effect of rainfall on diurnal and seasonal soil moisture is discussed. We have investigated relationships of soil moisture with sur- face albedo and soil thermal diffusivity. The diurnal variation of surface albedo appears as a.

  6. The effect of pulverization on the albedo of lunar rocks

    NARCIS (Netherlands)

    Minnaert, Marcel Gilles Jozef

    1969-01-01

    Measures of the albedo under full-moon conditions have been made on two samples of very dark rocks, pulverized and sieved so as to obtain powders of different grain size. Below a size of 0.05 mm the albedo suddenly increases, obviously because the individual grains become transparent. By a rough

  7. Coupling of Important Physical Processes in the Planetary Boundary Layer between Meteorological and Chemistry Models for Regional to Continental Scale Air Quality Forecasting: An Overview

    Directory of Open Access Journals (Sweden)

    Pius Lee

    2011-08-01

    Full Text Available A consensus among many Air Quality (AQ modelers is that planetary boundary layer processes are the most influential processes for surface concentrations of air pollutants. Due to the many uncertainties intrinsically embedded in the parameterization of these processes, parameter optimization is often employed to determine an optimal set or range of values of the sensitive parameters. In this review study, we focus on the two of the most important physical processes: turbulent mixing and dry deposition. An emphasis was put on surveying AQ models that have been proven to resolve meso-scale features and cover a large geographical area, such as large regional, continental, or trans-continental boundary extents. Five AQ models were selected. Four of the models were run in real-time operational forecasting settings for continental scale AQ. The models use various forms of level 2.5 closure algorithms to calculate turbulent mixing. Tuning and parameter optimization has been used to tailor these algorithms to better suit their AQ models which are typically comprised of a coupled chemistry and meteorology model. Longer forecasts and long lead-times are inevitably under increasing demand for these models. Land Surface Models that have the capability for soil moisture and temperature data assimilation will have an advantage to constrain the key variables that govern the partitioning of surface sensible and latent heat fluxes and thus attain the potential to perform better in longer forecasts than those models that do not have this capability. Dry deposition velocity is a very significant model parameter that governs a major surface exchange activity. An exploratory study has been conducted to see the upper bound of roughness length in the similarity equation for aerodynamic resistance.

  8. NEOWISE REACTIVATION MISSION YEAR TWO: ASTEROID DIAMETERS AND ALBEDOS

    Energy Technology Data Exchange (ETDEWEB)

    Nugent, C. R.; Cutri, R. M. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Mainzer, A.; Bauer, J.; Kramer, E. A.; Masiero, J.; Sonnett, S. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Grav, T. [Planetary Science Institute, Tucson, AZ (United States); Wright, E. L., E-mail: cnugent@ipac.caltech.edu [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

    2016-09-01

    The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids (NEAs) and 8885 other asteroids. Of the NEAs, 84% NEAs did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes shows accuracy consistent with previous NEOWISE publications. Diameters and albedos fall within ±∼20% and ±∼40%, 1-sigma, respectively, of those measured by these alternate techniques. NEOWISE continues to preferentially discover near-Earth objects which are large (>100 m), and have low albedos.

  9. Use of wrist albedo neutron dosimeters

    International Nuclear Information System (INIS)

    Hankins, D.E.

    1983-01-01

    We are developing a wrist dosimeter that can be used to measure the exposure at the wrist to x-rays, gamma rays, beta-particles, thermal neutrons and fast neutrons. It consists of a modified Hankins Type albedo neutron dosimeter and also contains three pieces of CR-39 plastic. ABS plastic in the form of an elongated hemisphere provides the beta and low energy x-ray shielding necessary to meet the requirement of depth dose measurements at 1 cm. The dosimeter has a beta window located in the side of the hemisphere oriented towards an object being held in the hands. A TLD 600 is positioned under the 1 cm thick ABS plastic and is used to measure the thermal neutron dose. At present we are using Velcro straps to hold the dosimeter on the inside of the wrist. 9 figures

  10. Non-planetary Science from Planetary Missions

    Science.gov (United States)

    Elvis, M.; Rabe, K.; Daniels, K.

    2015-12-01

    Planetary science is naturally focussed on the issues of the origin and history of solar systems, especially our own. The implications of an early turbulent history of our solar system reach into many areas including the origin of Earth's oceans, of ores in the Earth's crust and possibly the seeding of life. There are however other areas of science that stand to be developed greatly by planetary missions, primarily to small solar system bodies. The physics of granular materials has been well-studied in Earth's gravity, but lacks a general theory. Because of the compacting effects of gravity, some experiments desired for testing these theories remain impossible on Earth. Studying the behavior of a micro-gravity rubble pile -- such as many asteroids are believed to be -- could provide a new route towards exploring general principles of granular physics. These same studies would also prove valuable for planning missions to sample these same bodies, as techniques for anchoring and deep sampling are difficult to plan in the absence of such knowledge. In materials physics, first-principles total-energy calculations for compounds of a given stoichiometry have identified metastable, or even stable, structures distinct from known structures obtained by synthesis under laboratory conditions. The conditions in the proto-planetary nebula, in the slowly cooling cores of planetesimals, and in the high speed collisions of planetesimals and their derivatives, are all conditions that cannot be achieved in the laboratory. Large samples from comets and asteroids offer the chance to find crystals with these as-yet unobserved structures as well as more exotic materials. Some of these could have unusual properties important for materials science. Meteorites give us a glimpse of these exotic materials, several dozen of which are known that are unique to meteorites. But samples retrieved directly from small bodies in space will not have been affected by atmospheric entry, warmth or

  11. Global color and albedo variations on Io

    Science.gov (United States)

    McEwen, A.S.

    1988-01-01

    Three multispectral mosaics of Io have been produced from Voyager imaging data: a global mosaic from each of the Voyager 1 and Voyager 2 data sets and a high-resolution mosaic of the region surrounding the volcano Ra Patera. The mosaics are maps of normal albedo and color in accurate geometric map formats. Io's photometric behavior, mapped with a two-image technique, is spatially variable, especially in the bright white areas. The disk-integrated color and albedo of the satellite have been remarkably constant over recent decades, despite the volcanic activity and the many differences between Voyager 1 and 2 images (acquired just 4 months apart). This constancy is most likely due to the consistent occurrence of large Pele-type plumes with relatively dark, red deposits in the region from long 240 to 360??. A transient brightening southeast of Pele during the Voyager 1 encounter was probably due to real changes in surface and/or atmospheric materials, rather than to photometric behavior. The intrinsic spectral variability of Io, as seen in a series of two-dimensional histograms of the multispectral mosaics, consists of continuous variation among three major spectral end members. The data were mapped into five spectral units to compare them with laboratory measurements of candidate surface materials and to show the planimetric distributions. Unit 1 is best fit by the spectral reflectance of ordinary elemental sulfur, and it is closely associated with the Peletype plume deposits. Unit 2 is strongly confined to the polar caps above about latitude ??50??, but its composition is unknown. Unit 5 is probably SO2 with relatively minor contamination; it is concentrated in the equatorial region and near the long-lived Prometheus-type plumes. Units 3 and 4 are gradational between units 1 and 5. In addition to SO2 and elemental sulfur, other plausible components of the surface are polysulfur oxides, FeCl2, Na2S, and NaHS. ?? 1988.

  12. A Synthetical Estimation of Northern Hemisphere Sea-ice Albedo Radiative Forcing and Feedback between 1982 and 2009

    Science.gov (United States)

    Cao, Y.

    2014-12-01

    The decreasing surface albedo caused by continously vanishing sea ice over the Arctic plays a very important role in Arctic warming amplification. However, the quantification of the change of radiative forcing at top of atmosphere (TOA) introduced by the decreasing sea ice albedo and its generated feedback to the climate remain uncertain. Two recent representative studies showed a large difference with each other: Flanner et al. (2011) used a method of synthesis of surface albedo and radiative kernels and found that the change of sea ice radiative forcing (ΔSIRF) in Northern Hemisphere (NH) from 1979 to 2008 was 0.22 (0.15 - 0.32) W m-2, and the corresponding sea ice albedo feedback (SIAF) over NH was 0.28 (0.19 - 0.41) W m-2 K-1; while Pistone et al. (2014) directly used the observed planetary albedo to estimate the NH ΔSIRF and SIAF from 1979 to 2011 and draw a NH ΔSIRF of 0.43 ± 0.07 W m-2, which was nearly twice as larger as Flanner's result, and the estimated global SIAF was 0.31 ± 0.04 W m-2 K-1. Motivated by reconciling the difference between these two studies and obtaining a more accurate qualification of the NH ΔSIRF, we used a newly released satellite-retrieved surface albedo product CLARA-A1 and made an attempt in two steps: Firstly, based on synthesising the surface albedo and raditive kernels, we calcualted the ΔSIRF from 1982 to 2009 was 0.20 ± 0.05 W m-2, and the NH SIAF was 0.25 W m-2 K-1; After comparing with TOA observed radiative flux, we found it's quite likely the kernel methods yield an underestimation for the all-sky ΔSIRF. Then, we tried to use TOA observed broadband radiative flux to adjust the estimation with kernels. After an adjustment, the NH all-sky ΔSIRF was 0.34 ± 0.09 W m-2, and the corresponding SIAF was 0.43 W m-2 K-1 over NH and 0.31 W m-2 K-1 over the entire globe.

  13. Fire disturbance effects on land surface albedo in Alaskan tundra

    Science.gov (United States)

    French, Nancy H. F.; Whitley, Matthew A.; Jenkins, Liza K.

    2016-03-01

    The study uses satellite Moderate Resolution Imaging Spectroradiometer albedo products (MCD43A3) to assess changes in albedo at two sites in the treeless tundra region of Alaska, both within the foothills region of the Brooks Range, the 2007 Anaktuvuk River Fire (ARF) and 2012 Kucher Creek Fire (KCF). Results are compared to each other and other studies to assess the magnitude of albedo change and the longevity of impact of fire on land surface albedo. In both sites there was a marked decrease of albedo in the year following the fire. In the ARF, albedo slowly increased until 4 years after the fire, when it returned to albedo values prior to the fire. For the year immediately after the fire, a threefold difference in the shortwave albedo decrease was found between the two sites. ARF showed a 45.3% decrease, while the KCF showed a 14.1% decrease in shortwave albedo, and albedo is more variable in the KCF site than ARF site 1 year after the fire. These differences are possibly the result of differences in burn severity of the two fires, wherein the ARF burned more completely with more contiguous patches of complete burn than KCF. The impact of fire on average growing season (April-September) surface shortwave forcing in the year following fire is estimated to be 13.24 ± 6.52 W m-2 at the ARF site, a forcing comparable to studies in other treeless ecosystems. Comparison to boreal studies and the implications to energy flux are discussed in the context of future increases in fire occurrence and severity in a warming climate.

  14. Estimate of Top-of-Atmosphere Albedo for a Molecular Atmosphere over Ocean using Clouds and the Earth's Radiant Energy System (CERES) Measurements

    Science.gov (United States)

    Kato, S.; Loeb, N. G.; Rutledge, C. K.

    2002-01-01

    The shortwave broadband albedo at the top of a molecular atmosphere over ocean between 40deg N and 40deg S is estimated using radiance measurements from the Clouds and the Earth's Radiant Energy System (CERES) instrument and the Visible Infrared Scanner (VIRS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The albedo monotonically increases from 0.059 at a solar zenith angle of 10deg to 0.107 at a solar zenith angle of 60deg. The estimated uncertainty in the albedo is 3.5 x 10(exp -3) caused by the uncertainty in CERES-derived irradiances, uncertainty in VIRS-derived aerosol optical thicknesses, variations in ozone and water vapor, and variations in surface wind speed. The estimated uncertainty is similar in magnitude to the standard deviation of 0.003 that is derived from 72 areas divided by 20deg latitude by 20deg longitude grid boxes. The empirically estimated albedo is compared with the modeled albedo using a radiative transfer model combined with an ocean surface bidirectional reflectivity model. The modeled albedo with standard tropical atmosphere is 0.061 and 0.111 at the solar zenith angles of 10deg and 60deg, respectively. This empirically estimated albedo can be used to estimate the direct radiative effect of aerosols at the top of the atmosphere over oceans.

  15. The Role of NASA's Planetary Data System in the Planetary Spatial Data Infrastructure Initiative

    Science.gov (United States)

    Arvidson, R. E.; Gaddis, L. R.

    2017-12-01

    An effort underway in NASA's planetary science community is the Mapping and Planetary Spatial Infrastructure Team (MAPSIT, http://www.lpi.usra.edu/mapsit/). MAPSIT is a community assessment group organized to address a lack of strategic spatial data planning for space science and exploration. Working with MAPSIT, a new initiative of NASA and USGS is the development of a Planetary Spatial Data Infrastructure (PSDI) that builds on extensive knowledge on storing, accessing, and working with terrestrial spatial data. PSDI is a knowledge and technology framework that enables the efficient discovery, access, and exploitation of planetary spatial data to facilitate data analysis, knowledge synthesis, and decision-making. NASA's Planetary Data System (PDS) archives >1.2 petabytes of digital data resulting from decades of planetary exploration and research. The PDS charter focuses on the efficient collection, archiving, and accessibility of these data. The PDS emphasis on data preservation and archiving is complementary to that of the PSDI initiative because the latter utilizes and extends available data to address user needs in the areas of emerging technologies, rapid development of tailored delivery systems, and development of online collaborative research environments. The PDS plays an essential PSDI role because it provides expertise to help NASA missions and other data providers to organize and document their planetary data, to collect and maintain the archives with complete, well-documented and peer-reviewed planetary data, to make planetary data accessible by providing online data delivery tools and search services, and ultimately to ensure the long-term preservation and usability of planetary data. The current PDS4 information model extends and expands PDS metadata and relationships between and among elements of the collections. The PDS supports data delivery through several node services, including the Planetary Image Atlas (https

  16. Airships for Planetary Exploration

    Science.gov (United States)

    Colozza, Anthony

    2004-01-01

    The feasibility of utilizing an airship for planetary atmospheric exploration was assessed. The environmental conditions of the planets and moons within our solar system were evaluated to determine their applicability for airship flight. A station-keeping mission of 50 days in length was used as the baseline mission. Airship sizing was performed utilizing both solar power and isotope power to meet the baseline mission goal at the selected planetary location. The results show that an isotope-powered airship is feasible within the lower atmosphere of Venus and Saturn s moon Titan.

  17. Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ben; Qian, Yun; Berg, Larry K.; Ma, Po-Lun; Wharton, Sonia; Bulaevskaya, Vera; Yan, Huiping; Hou, Zhangshuan; Shaw, William J.

    2016-07-21

    We evaluate the sensitivity of simulated turbine-height winds to 26 parameters applied in a planetary boundary layer (PBL) scheme and a surface layer scheme of the Weather Research and Forecasting (WRF) model over an area of complex terrain during the Columbia Basin Wind Energy Study. An efficient sampling algorithm and a generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of modeled turbine-height winds. The results indicate that most of the variability in the ensemble simulations is contributed by parameters related to the dissipation of the turbulence kinetic energy (TKE), Prandtl number, turbulence length scales, surface roughness, and the von Kármán constant. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability. The parameter associated with the TKE dissipation rate is found to be the most important one, and a larger dissipation rate can produce larger hub-height winds. A larger Prandtl number results in weaker nighttime winds. Increasing surface roughness reduces the frequencies of both extremely weak and strong winds, implying a reduction in the variability of the wind speed. All of the above parameters can significantly affect the vertical profiles of wind speed, the altitude of the low-level jet and the magnitude of the wind shear strength. The wind direction is found to be modulated by the same subset of influential parameters. Remainder of abstract is in attachment.

  18. Influence of stellar duplicity on the form of planetary nebulae

    International Nuclear Information System (INIS)

    Kolesnik, I.G.; Pilyugin, L.S.

    1986-01-01

    Formation of planetary nebulae's spatial structures is considered. Simple expression for angular distribution of density in planetary nebulae is obtained. Bipolar structures are formed effectively in binary systems in which the velocity of the expanding shell around the main star is smaller than the orbital velocity of the satellite. Masses of satellites lie in the range 0.1-0.4Msub(sun). Theoretical isophotal contour map for the model of the planetary nebula NGC 3587 is consistent with observational data. It is shown that central stars of planetary nebulae are usually binary systems

  19. Understanding the drivers of post-fire albedo and radiative forcing across Alaska and Canada: implications for management.

    Science.gov (United States)

    Potter, S.; Solvik, K.; Erb, A.; Goetz, S. J.; Johnstone, J. F.; Mack, M. C.; Randerson, J. T.; Roman, M. O.; Schaaf, C. L.; Turetsky, M. R.; Veraverbeke, S.; Wang, Z.; Rogers, B. M.

    2017-12-01

    Boreal forest dynamics including succession, composition, carbon cycling, and surface-atmosphere energy exchanges are largely driven by fire. In Alaska and Canada, burned area and fire frequency have increased since the 1970s, and are projected to continue increasing into the 21st century. In contrast to other biomes, alterations to surface albedo from fires in North American boreal forests are one of the primary feedbacks to climate. Understanding how altered fire regimes impact vegetation composition and energy budgets is therefore critical to forecasting regional and global climate change. High-severity fires cause winter and spring albedo to increase due to increased snow exposure and replacement of evergreen conifers by deciduous broadleaf trees. Although summer albedo decreases initially due to the deposition of black carbon and charred surfaces, it typically increases for several decades thereafter when younger and brighter deciduous trees dominate. The net effect of these albedo changes is expected to result in substantive radiative cooling, but there has been little research to examine how albedo trajectories differ spatially and temporally as a result of differences in burn severity, species composition, topography, climate and soil properties, and what the associated implications for future energy balances are. Here we investigate drivers of post-fire monthly albedo trajectories across Canada and Alaska using a new Collection V006 500 m MODIS daily blue-sky albedo product and historical fires from the Canadian and Alaskan National Fire Databases. The impacts of varying fuel type, landscape position, soils, climate, and burn severity on monthly albedo trajectories are explored using a Random Forest model. This information is then used to predict long-term monthly albedo and radiative forcing for fires that occurred during the MODIS era (2001-2012). We find that higher severity burns in denser forests and environmental conditions that promote either

  20. Albedos and spectral signatures determination and it connection to geological processes: Simile between Earth and other solar system bodies

    Science.gov (United States)

    Suarez, J.; Ochoa, L.; Saavedra, F.

    2017-07-01

    Remote sensing has always been the best investigation tool for planetary sciences. In this research have been used data of Surface albedo, electromagnetic spectra and satelital imagery in search of understanding glacier dynamics in some bodies of the solar system, and how it's related to their compositions and associated geological processes, this methodology is very common in icy moons studies. Through analytic software's some albedos map's and geomorphological analysis were made that allow interpretation of different types of ice in the glacier's and it's interaction with other materials, almost all the images were worked in the visible and infrared ranges of the spectrum; spectral data were later used to connect the reflectance whit chemical and reologic properties of the compounds studied. It have been concluded that the albedo analysis is an effective tool to differentiate materials in the bodies surfaces, but the application of spectral data is necessary to know the exact compounds of the glaciers and to have a better understanding of the icy bodies.

  1. New and misclassified planetary nebulae

    International Nuclear Information System (INIS)

    Kohoutek, L.

    1978-01-01

    Since the 'Catalogue of Galactic Planetary Nebulae' 226 new objects have been classified as planetary nebulae. They are summarized in the form of designations, names, coordinates and the references to the discovery. Further 9 new objects have been added and called 'proto-planetary nebulae', but their status is still uncertain. Only 34 objects have been included in the present list of misclassified planetary nebulae although the number of doubtful cases is much larger. (Auth.)

  2. Dust in planetary nebulae

    International Nuclear Information System (INIS)

    Mathis, J.S.

    1978-01-01

    The author's review concentrates on theoretical aspects of dust in planetary nebulae (PN). He considers the questions: how much dust is there is PN; what is its composition; what effects does it have on the ionization structure, on the dynamics of the nebula. (Auth.)

  3. On Aryabhata's Planetary Constants

    OpenAIRE

    Kak, Subhash

    2001-01-01

    This paper examines the theory of a Babylonian origin of Aryabhata's planetary constants. It shows that Aryabhata's basic constant is closer to the Indian counterpart than to the Babylonian one. Sketching connections between Aryabhata's framework and earlier Indic astronomical ideas on yugas and cyclic calendar systems, it is argued that Aryabhata's system is an outgrowth of an earlier Indic tradition.

  4. The planetary scientist's companion

    CERN Document Server

    Lodders, Katharina

    1998-01-01

    A comprehensive and practical book of facts and data about the Sun, planets, asteroids, comets, meteorites, the Kuiper belt and Centaur objects in our solar system. Also covered are properties of nearby stars, the interstellar medium, and extra-solar planetary systems.

  5. Albedo's determination by the method of neutron impulse

    International Nuclear Information System (INIS)

    Flores Calderon, J.E.

    1982-01-01

    Experiments with non-stationary neutron transport in large cavity moderators (l>>Σsub(tr) -1 ) (where l is the characteristic cavity length and Σsub(tr) -1 the macroscopic transport section of the moderator) led to the method reported in this study which, based on neutron impulses for determining albedo of thermal neutrons, gave a precision greater by an order of magnitude over previous methods. A sufficient time interval after introduction of the neutron flux into the moderator chamber decreased exponentially the decay constant L, which was itself related to albedo by a function called f. Numerical calculations of albedo were assisted. (author)

  6. Evaluation of the global MODIS 30 arc-second spatially and temporally complete snow-free land surface albedo and reflectance anisotropy dataset

    Science.gov (United States)

    Sun, Qingsong; Wang, Zhuosen; Li, Zhan; Erb, Angela; Schaaf, Crystal B.

    2017-06-01

    Land surface albedo is an essential variable for surface energy and climate modeling as it describes the proportion of incident solar radiant flux that is reflected from the Earth's surface. To capture the temporal variability and spatial heterogeneity of the land surface, satellite remote sensing must be used to monitor albedo accurately at a global scale. However, large data gaps caused by cloud or ephemeral snow have slowed the adoption of satellite albedo products by the climate modeling community. To address the needs of this community, we used a number of temporal and spatial gap-filling strategies to improve the spatial and temporal coverage of the global land surface MODIS BRDF, albedo and NBAR products. A rigorous evaluation of the gap-filled values shows good agreement with original high quality data (RMSE = 0.027 for the NIR band albedo, 0.020 for the red band albedo). This global snow-free and cloud-free MODIS BRDF and albedo dataset (established from 2001 to 2015) offers unique opportunities to monitor and assess the impact of the changes on the Earth's land surface.

  7. Turbulence Dissipation Rates in the Planetary Boundary Layer from Wind Profiling Radars and Mesoscale Numerical Weather Prediction Models during WFIP2

    Science.gov (United States)

    Bianco, L.; McCaffrey, K.; Wilczak, J. M.; Olson, J. B.; Kenyon, J.

    2016-12-01

    When forecasting winds at a wind plant for energy production, the turbulence parameterizations in the forecast models are crucial for understanding wind plant performance. Recent research shows that the turbulence (eddy) dissipation rate in planetary boundary layer (PBL) parameterization schemes introduces significant uncertainty in the Weather Research and Forecasting (WRF) model. Thus, developing the capability to measure dissipation rates in the PBL will allow for identification of weaknesses in, and improvements to the parameterizations. During a preliminary field study at the Boulder Atmospheric Observatory in spring 2015, a 915-MHz wind profiling radar (WPR) measured dissipation rates concurrently with sonic anemometers mounted on a 300-meter tower. WPR set-up parameters (e.g., spectral resolution), post-processing techniques (e.g., filtering for non-atmospheric signals), and spectral averaging were optimized to capture the most accurate Doppler spectra for measuring spectral widths for use in the computation of the eddy dissipation rates. These encouraging results lead to the implementation of the observing strategy on a 915-MHz WPR in Wasco, OR, operating as part of the Wind Forecasting Improvement Project 2 (WFIP2). These observations are compared to dissipation rates calculated from the High-Resolution Rapid Refresh model, a WRF-based mesoscale numerical weather prediction model run for WFIP2 at 3000 m horizontal grid spacing and with a nest, which has 750-meter horizontal grid spacing, in the complex terrain region of the Columbia River Gorge. The observed profiles of dissipation rates are used to evaluate the PBL parameterization schemes used in the HRRR model, which are based on the modeled turbulent kinetic energy and a tunable length scale.

  8. Models of the Mass-ejection Histories of Pre-planetary Nebulae. II. The Formation of Minkowski’s Butterfly and its Proboscis in M2–9

    Science.gov (United States)

    Balick, Bruce; Frank, Adam; Liu, Baowei; Corradi, Romano

    2018-02-01

    M2–9, or the “Minkowski’s Butterfly,” is one of the most iconic outflow sources from an evolved star. In this paper we present a hydrodynamic model of M2–9 in which the nebula is formed and shaped by a steady, low-density (“light”), mildly collimated “spray” of gas injected at 200 km s‑1 that interacts with a far denser, intrinsically simple pre-existing AGB wind that has slowly formed all of the complex features within M2–9’s lobes (including the knot pairs N3/S3 and N4/S4 at their respective leading edges, and the radial gradient of Doppler shifts within 20″ of the nucleus). We emphasize that the knot pairs are not ejected from the star but formed in situ. In addition, the observed radial speed of the knots is only indirectly related to the speed of the gas injected by the star. The model allows us to probe the early history of the wind geometry and lobe formation. We also formulate a new estimate of the nebular distance D = 1.3 kpc. The physical mechanism that accounts for the linear radial speed gradient in M2–9 applies generally to many other pre-planetary nebulae whose hollow lobes exhibit similar gradients along their edges.

  9. Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model

    Science.gov (United States)

    Yang, Ben; Qian, Yun; Berg, Larry K.; Ma, Po-Lun; Wharton, Sonia; Bulaevskaya, Vera; Yan, Huiping; Hou, Zhangshuan; Shaw, William J.

    2017-01-01

    We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor-Yamada-Nakanishi-Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.

  10. PHOTOMETRIC STEREO SHAPE-AND-ALBEDO-FROM-SHADING FOR PIXEL-LEVEL RESOLUTION LUNAR SURFACE RECONSTRUCTION

    Directory of Open Access Journals (Sweden)

    W. C. Liu

    2017-07-01

    Full Text Available Shape and Albedo from Shading (SAfS techniques recover pixel-wise surface details based on the relationship between terrain slopes, illumination and imaging geometry, and the energy response (i.e., image intensity captured by the sensing system. Multiple images with different illumination geometries (i.e., photometric stereo can provide better SAfS surface reconstruction due to the increase in observations. Photometric stereo SAfS is suitable for detailed surface reconstruction of the Moon and other extra-terrestrial bodies due to the availability of photometric stereo and the less complex surface reflecting properties (i.e., albedo of the target bodies as compared to the Earth. Considering only one photometric stereo pair (i.e., two images, pixel-variant albedo is still a major obstacle to satisfactory reconstruction and it needs to be regulated by the SAfS algorithm. The illumination directional difference between the two images also becomes an important factor affecting the reconstruction quality. This paper presents a photometric stereo SAfS algorithm for pixel-level resolution lunar surface reconstruction. The algorithm includes a hierarchical optimization architecture for handling pixel-variant albedo and improving performance. With the use of Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC NAC photometric stereo images, the reconstructed topography (i.e., the DEM is compared with the DEM produced independently by photogrammetric methods. This paper also addresses the effect of illumination directional difference in between one photometric stereo pair on the reconstruction quality of the proposed algorithm by both mathematical and experimental analysis. In this case, LROC NAC images under multiple illumination directions are utilized by the proposed algorithm for experimental comparison. The mathematical derivation suggests an illumination azimuthal difference of 90 degrees between two images is recommended to achieve

  11. On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances

    Science.gov (United States)

    Henry, R. B. C.; Stephenson, B. G.; Miller Bertolami, M. M.; Kwitter, K. B.; Balick, B.

    2018-01-01

    The primary goal of this paper is to make a direct comparison between the measured and model-predicted abundances of He, C, and N in a sample of 35 well-observed Galactic planetary nebulae (PNe). All observations, data reductions, and abundance determinations were performed in house to ensure maximum homogeneity. Progenitor star masses (M ≤ 4 M⊙) were inferred using two published sets of post-asymptotic giant branch model tracks and L and Teff values. We conclude the following: (1) the mean values of N/O across the progenitor mass range exceeds the solar value, indicating significant N enrichment in the majority of our objects; (2) the onset of hot bottom burning appears to begin around 2 M⊙, i.e. lower than ∼5 M⊙ implied by theory; (3) most of our objects show a clear He enrichment, as expected from dredge-up episodes; (4) the average sample C/O value is 1.23, consistent with the effects of third dredge up; and (5) model grids used to compare to observations successfully span the distribution over metallicity space of all C/O and many He/H data points but mostly fail to do so in the case of N/O. The evident enrichment of N in PN and the general discrepancy between the observed and model-predicted N/O abundance ratios signal the need for extra mixing as an effect of rotation and/or thermohaline mixing in the models. The unexpectedly high N enrichment that is implied here for low-mass stars, if confirmed, will likely impact our conclusions about the source of N in the Universe.

  12. Changes in Snow Albedo Resulting from Snow Darkening Caused by Black Carbon

    Science.gov (United States)

    Engels, J.; Kloster, S.; Bourgeois, Q.

    2014-12-01

    We investigate the potential impact of snow darkening caused by pre-industrial and present-day black carbon (BC) emissions on snow albedo and subsequently climate. To assess this impact, we implemented the effect of snow darkening caused by BC emitted from natural as well as anthropogenic sources into the Max Planck Institute for Meteorology Earth System Model (MPI-M ESM). Considerable amounts of BC are emitted e.g. from fires and are transported through the atmosphere for several days before being removed by rain or snow precipitation in snow covered regions. Already very small quantities of BC reduce the snow reflectance significantly, with consequences for snow melting and snow spatial coverage. We implemented the snow albedo reduction caused by BC contamination and snow aging in the one layer land surface component (JSBACH) of the atmospheric general circulation model ECHAM6, developed at MPI-M. For this we used the single-layer simulator of the SNow, Ice, and Aerosol Radiation (SNICAR-Online (Flanner et al., 2007); http://snow.engin.umich.edu) model to derive snow albedo values for BC in snow concentrations ranging between 0 and 1500 ng(BC)/g(snow) for different snow grain sizes for the visible (0.3 - 0.7 μm) and near infrared range (0.7 - 1.5 μm). As snow grains grow over time, we assign different snow ages to different snow grain sizes (50, 150, 500, and 1000 μm). Here, a radius of 50 μm corresponds to new snow, whereas a radius of 1000 μm corresponds to old snow. The deposition rates of BC on snow are prescribed from previous ECHAM6-HAM simulations for two time periods, pre-industrial (1880-1889) and present-day (2000-2009), respectively. We perform a sensitivity study regarding the scavenging of BC by snow melt. To evaluate the newly implemented albedo scheme we will compare the modeled black carbon in snow concentrations to observed ones. Moreover, we will show the impact of the BC contamination and snow aging on the simulated snow albedo. The

  13. On the shape and albedo variegation of asteroids - Results from Fourier analysis of synthetic and observed asteroid lightcurves

    Science.gov (United States)

    Barucci, M. Antonietta; Capria, M. Teresa; Harris, Alan W.; Fulchignoni, Marcello

    1989-01-01

    Fourier analyses have been conducted of those asteroids in the Lagerkvist et al. (1987) lightcurves with substantially complete phase coverage and point density, and for which a unique period has been identified. Fourier coefficients are thereby obtained for 188 lightcurves of 91 asteroids, as well as for 868 synthetic lightcurves from a set of models different in shape and albedo markings; by comparing model and asteroid lightcurve coefficients, the possible shape and albedo variations for 18 asteroids are derived. An attempt is made to define the general distribution of shapes of all asteroid samples analyzed.

  14. PROVE Surface albedo of Jornada Experimental Range, New Mexico, 1997

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this study was to determine the spatial variations in field measurements of broadband albedo as related to the ground cover and under a range of...

  15. PROVE Surface albedo of Jornada Experimental Range, New Mexico, 1997

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The objective of this study was to determine the spatial variations in field measurements of broadband albedo as related to the ground cover and under a...

  16. Correcting the Response of an Albedo Neutron Dosimeter for Energy

    National Research Council Canada - National Science Library

    Riel, Gordon K; Winters, Patrick J; Cassata, James R; St. John, Ted; Benevides, Luis A

    2007-01-01

    The neutron response of an albedo neutron dosimeter varies greatly with energy. For example, the dosimeter, calibrated with moderated Californium fission neutrons, will read more than 30 times the dose from thermal neutrons and less than 3...

  17. ALBEDO PATTERN RECOGNITION AND TIME-SERIES ANALYSES IN MALAYSIA

    Directory of Open Access Journals (Sweden)

    S. A. Salleh

    2012-07-01

    Full Text Available Pattern recognition and time-series analyses will enable one to evaluate and generate predictions of specific phenomena. The albedo pattern and time-series analyses are very much useful especially in relation to climate condition monitoring. This study is conducted to seek for Malaysia albedo pattern changes. The pattern recognition and changes will be useful for variety of environmental and climate monitoring researches such as carbon budgeting and aerosol mapping. The 10 years (2000–2009 MODIS satellite images were used for the analyses and interpretation. These images were being processed using ERDAS Imagine remote sensing software, ArcGIS 9.3, the 6S code for atmospherical calibration and several MODIS tools (MRT, HDF2GIS, Albedo tools. There are several methods for time-series analyses were explored, this paper demonstrates trends and seasonal time-series analyses using converted HDF format MODIS MCD43A3 albedo land product. The results revealed significance changes of albedo percentages over the past 10 years and the pattern with regards to Malaysia's nebulosity index (NI and aerosol optical depth (AOD. There is noticeable trend can be identified with regards to its maximum and minimum value of the albedo. The rise and fall of the line graph show a similar trend with regards to its daily observation. The different can be identified in term of the value or percentage of rises and falls of albedo. Thus, it can be concludes that the temporal behavior of land surface albedo in Malaysia have a uniform behaviours and effects with regards to the local monsoons. However, although the average albedo shows linear trend with nebulosity index, the pattern changes of albedo with respects to the nebulosity index indicates that there are external factors that implicates the albedo values, as the sky conditions and its diffusion plotted does not have uniform trend over the years, especially when the trend of 5 years interval is examined, 2000 shows high

  18. Estimation of Sub Hourly Glacier Albedo Values Using Artificial Intelligence Techniques

    Science.gov (United States)

    Moya Quiroga, Vladimir; Mano, Akira; Asaoka, Yoshihiro; Udo, Keiko; Kure, Shuichi; Mendoza, Javier

    2013-04-01

    Glaciers are the most important fresh water reservoirs storing about 67% of total fresh water. Unfortunately, they are retreating and some small glaciers have already disappeared. Thus, snow glacier melt (SGM) estimation plays an important role in water resources management. Whether SGM is estimated by complete energy balance or a simplified method, albedo is an important data present in most of the methods. However, this is a variable value depending on the ground surface and local conditions. The present research presents a new approach for estimating sub hourly albedo values using different artificial intelligence techniques such as artificial neural networks and decision trees along with measured and easy to obtain data. . The models were developed using measured data from the Zongo-Ore station located in the Bolivian tropical glacier Zongo (68°10' W, 16°15' S). This station automatically records every 30 minutes several meteorological parameters such as incoming short wave radiation, outgoing short wave radiation, temperature or relative humidity. The ANN model used was the Multi Layer Perceptron, while the decision tree used was the M5 model. Both models were trained using the WEKA software and validated using the cross validation method. After analysing the model performances, it was concluded that the decision tree models have a better performance. The model with the best performance was then validated with measured data from the Equatorian tropical glacier Antizana (78°09'W, 0°28'S). The model predicts the sub hourly albedo with an overall mean absolute error of 0.103. The highest errors occur for albedo measured values higher than 0.9. Considering that this is an extreme value coincident with low measured values of incoming short wave radiation, it is reasonable to assume that such values include errors due to censored data. Assuming a maximum albedo of 0.9 improved the accuracy of the model reducing the MAE to less than 0.1. Considering that the

  19. IAU nomenclature for albedo features on the planet Mercury

    Science.gov (United States)

    Dollfus, A.; Chapman, C. R.; Davies, M. E.; Gingerich, O.; Goldstein, R.; Guest, J.; Morrison, D.; Smith, B. A.

    1978-01-01

    The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.

  20. Evaluation of coarse scale land surface remote sensing albedo product over rugged terrain

    Science.gov (United States)

    Wen, J.; Xinwen, L.; You, D.; Dou, B.

    2017-12-01

    Satellite derived Land surface albedo is an essential climate variable which controls the earth energy budget and it can be used in applications such as climate change, hydrology, and numerical weather prediction. The accuracy and uncertainty of surface albedo products should be evaluated with a reliable reference truth data prior to applications. And more literatures investigated the validation methods about the albedo validation in a flat or homogenous surface. However, the albedo performance over rugged terrain is still unknow due to the validation method limited. A multi-validation strategy is implemented to give a comprehensive albedo validation, which will involve the high resolution albedo processing, high resolution albedo validation based on in situ albedo, and the method to upscale the high resolution albedo to a coarse scale albedo. Among them, the high resolution albedo generation and the upscale method is the core step for the coarse scale albedo validation. In this paper, the high resolution albedo is generated by Angular Bin algorithm. And a albedo upscale method over rugged terrain is developed to obtain the coarse scale albedo truth. The in situ albedo located 40 sites in mountain area are selected globally to validate the high resolution albedo, and then upscaled to the coarse scale albedo by the upscale method. This paper takes MODIS and GLASS albedo product as a example, and the prelimarily results show the RMSE of MODIS and GLASS albedo product over rugged terrain are 0.047 and 0.057, respectively under the RMSE with 0.036 of high resolution albedo.

  1. Raising the Albedo of 2010 GY6: Fitting ATPM to Wise Data

    Science.gov (United States)

    Wooden, D. H.; Rozitis, B. D.; Jefferson, J. D.; Nelson, T. W.; Dotson, J. L.

    2017-01-01

    Near-Earth Asteroid 462775 (2010 GY6) is in the Apollo orbit-family with a 1.46 year orbital period. 2010 GY6 was measured by WISE and fitted with NEATM, yielding NEATM model parameters of D=1.1 km, pv=0.028 and eta=2.3.The NEATM-derived geometric albedo of 2010 GY6 is lower than the surface of comet 67P/C-G. The eta value is considerably higher than typical for its phase angle of 33 deg, indicating a cooler surface due to non-zero thermal inertia and/or surface roughness are important. If the thermal inertia and surface roughness are constrained by fitting the Advanced Thermophysical Model (ATPM) to the WISE data, what would the resulting geometric albedo? We find pv=0.06-0.08, in the same range as B- or C-type NEAs like Bennu or JU3.

  2. An analytical model for dispersion of material in the atmospheric planetary boundary layer in presence of precipitation

    International Nuclear Information System (INIS)

    Mayhoub, A.B.; Etman, S.M.

    1985-05-01

    An analytical model for the dispersion of particulates and finely divided material released into the atmosphere near the ground is presented. The possible precipitation when the particles are dense enough and large enough to have deposition velocity, is taken into consideration. The model is derived analytically in the mixing layer or Ekman boundary layer where the mixing process is a direct consequence of turbulent and convective motions generated in the boundary layer. (author)

  3. CONFRONTING STANDARD MODELS OF PROTO-PLANETARY DISKS WITH NEW MID-INFRARED SIZES FROM THE KECK INTERFEROMETER

    Energy Technology Data Exchange (ETDEWEB)

    Millan-Gabet, Rafael [California Institute of Technology, NASA Exoplanet Science Institute, Pasadena, CA 91125 (United States); Che, Xiao; Monnier, John D.; Aarnio, Alicia N. [University of Michigan Astronomy Department, 1085 S. University Avenue 303B West Hall University of Michigan, Ann Arbor, MI 48109-1107 (United States); Sitko, Michael L.; Day, Amanda N. [Department of Physics, University of Cincinnati, Cincinnati OH 45221 (United States); Russell, Ray W. [The Aerospace Corporation, Los Angeles, CA 90009 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Perry, R. B. [NASA Langley Research Center, MS 160, Hampton, VA 23681 (United States); Harries, Tim J. [Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Colavita, Mark M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Wizinowich, Peter L.; Ragland, Sam; Woillez, Julien, E-mail: R.Millan-Gabet@caltech.edu [Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela, HI 96743 (United States)

    2016-08-01

    We present near- and mid-infrared (MIR) interferometric observations made with the Keck Interferometer Nuller and near-contemporaneous spectro-photometry from the infrared telescope facilities (IRTFs) of 11 well-known young stellar objects, several of which were observed for the first time in these spectral and spatial resolution regimes. With au-level spatial resolution, we first establish characteristic sizes of the infrared emission using a simple geometrical model consisting of a hot inner rim and MIR disk emission. We find a high degree of correlation between the stellar luminosity and the MIR disk sizes after using near-infrared data to remove the contribution from the inner rim. We then use a semi-analytical physical model to also find that the very widely used “star + inner dust rim + flared disk” class of models strongly fails to reproduce the spectral energy distribution (SED) and spatially resolved MIR data simultaneously; specifically a more compact source of MIR emission is required than results from the standard flared disk model. We explore the viability of a modification to the model whereby a second dust rim containing smaller dust grains is added, and find that the 2-rim model leads to significantly improved fits in most cases. This complexity is largely missed when carrying out SED modeling alone, although detailed silicate feature fitting by McClure et al. recently came to a similar conclusion. As has been suggested recently by Menu et al., the difficulty in predicting MIR sizes from the SED alone might hint at “transition disk”-like gaps in the inner au; however, the relatively high correlation found in our MIR disk size versus stellar luminosity relation favors layered disk morphologies and points to missing disk model ingredients instead.

  4. Effect of land albedo, CO2, orography, and oceanic heat transport on extreme climates

    Directory of Open Access Journals (Sweden)

    V. Romanova

    2006-01-01

    Full Text Available Using an atmospheric general circulation model of intermediate complexity coupled to a sea ice – slab ocean model, we perform a number of sensitivity experiments under present-day orbital conditions and geographical distribution to assess the possibility that land albedo, atmospheric CO2, orography and oceanic heat transport may cause an ice-covered Earth. Changing only one boundary or initial condition, the model produces solutions with at least some ice-free oceans in the low latitudes. Using some combination of these forcing parameters, a full Earth's glaciation is obtained. We find that the most significant factor leading to an ice-covered Earth is the high land albedo in combination with initial temperatures set equal to the freezing point. Oceanic heat transport and orography play only a minor role for the climate state. Extremely low concentrations of CO2 also appear to be insufficient to provoke a runaway ice-albedo feedback, but the strong deviations in surface air temperatures in the Northern Hemisphere point to the existence of a strong nonlinearity in the system. Finally, we argue that the initial condition determines whether the system can go into a completely ice covered state, indicating multiple equilibria, a feature known from simple energy balance models.

  5. Analysis of planetary boundary layer fluxes and land-atmosphere coupling in the regional climate model CLM

    Science.gov (United States)

    Jaeger, E. B.; Stöckli, R.; Seneviratne, S. I.

    2009-09-01

    Land-atmosphere interactions and associated boundary layer processes are crucial elements of the climate system and play a major role in several feedback processes, in particular for extreme events. In this article, we provide a detailed validation of land surface processes and land-atmosphere interactions in the climate version of the Lokal Modell (CLM), a regional climate model that has been recently developed and is now used by a wide research community. For the evaluation of the model, we use observations from the FLUXNET network and meteorological data. Moreover, we also compare the performance of the CLM with that of its driving data set, the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis, and simulations of the Inter-Continental Transferability Study (ICTS). The results show that most of the land-atmosphere coupling characteristics are consistent in CLM and the observations. Nonetheless, the analysis also allows identification of specific weaknesses of the CLM such as an underestimation of the incoming surface shortwave radiation due to cloud cover overestimation, leading to an underestimation of the sensible heat flux. The comparisons with the ECMWF operational analysis and the ICTS models suggest, however, that all models have biases of comparable magnitude. This study demonstrates the utility of flux observations for diagnosing biases in land-atmosphere exchanges and interactions in current climate models and highlights perspectives for our improved understanding of the relevant processes.

  6. Planetary nebulae and the interstellar magnetic field

    International Nuclear Information System (INIS)

    Heiligman, G.M.

    1980-01-01

    Previous workers have found a statistical correlation between the projected directions of the interstellar magnetic field and the major axes of planetary nebulae. This result has been examined theoretically using a numerical hydromagnetic model of a cold plasma nebula expanding into a uniform vacuum magnetic field, with nebular gas accreting on the surface. It is found that magnetic pressure alone is probably not sufficient to shape most planetary nebulae to the observed degree. Phenomena are discussed which could amplify simple magnetic pressure, alter nebular morphology and account for the observed correlation. (author)

  7. Planetary Radars Operating Centre PROC

    Science.gov (United States)

    Catallo, C.; Flamini, E.; Seu, R.; Alberti, G.

    2007-12-01

    Planetary exploration by means of radar systems, mainly using Ground Penetrating Radars (GPR) plays an important role in Italy. Numerous scientific international space programs are currently carried out jointly with ESA and NASA by Italian Space Agency, the scientific community and the industry. Three important experiments under Italian leadership ( designed and manufactured by the Italian industry), provided by ASI either as contribution to ESA programs either within a NASA/ASI joint venture framework, are now operating: MARSIS on-board Mars Express, SHARAD on-board Mars Reconnaissance Orbiter and CASSINI Radar on-board Cassini spacecraft. In order to support all the scientific communities, institutional customers and experiment teams operation three Italian dedicated operational centers have been realized, namely SHOC, (Sharad Operating Centre), MOC (Marsis Operating Center) and CASSINI PAD ( Processing Altimetry Data). Each center is dedicated to a single instrument management and control, data processing and distribution. Although they had been conceived to operate autonomously and independently one from each other, synergies and overlaps have been envisaged leading to the suggestion of a unified center, the Planetary Radar Processing Center (PROC). PROC is conceived in order to include the three operational centers, namely SHOC, MOC and CASSINI PAD, either from logistics point of view and from HW/SW capabilities point of view. The Planetary Radar Processing Center shall be conceived as the Italian support facility to the scientific community for on-going and future Italian planetary exploration programs. Therefore, scalability, easy use and management shall be the design drivers. The paper describes how PROC is designed and developed, to allow SHOC, MOC and CASSINI PAD to operate as before, and to offer improved functionalities to increase capabilities, mainly in terms of data exchange, comparison, interpretation and exploitation. Furthermore, in the frame of

  8. Decrease in Hysteresis of Planetary Climate for Planets with Long Solar Days

    Science.gov (United States)

    Abbot, Dorian S.; Bloch-Johnson, Jonah; Checlair, Jade; Farahat, Navah X.; Graham, R. J.; Plotkin, David; Popovic, Predrag; Spaulding-Astudillo, Francisco

    2018-02-01

    The ice-albedo feedback on rapidly rotating terrestrial planets in the habitable zone can lead to abrupt transitions (bifurcations) between a warm and a snowball (ice-covered) state, bistability between these states, and hysteresis in planetary climate. This is important for planetary habitability because snowball events may trigger rises in the complexity of life, but could also endanger complex life that already exists. Recent work has shown that planets tidally locked in synchronous rotation states will transition smoothly into the snowball state rather than experiencing bifurcations. Here we investigate the structure of snowball bifurcations on planets that are tidally influenced, but not synchronously rotating, so that they experience long solar days. We use PlaSIM, an intermediate-complexity global climate model, with a thermodynamic mixed layer ocean and the Sun’s spectrum. We find that the amount of hysteresis (the range in stellar flux for which there is bistability in climate) is significantly reduced for solar days with lengths of tens of Earth days, and disappears for solar days of hundreds of Earth days. These results suggest that tidally influenced planets orbiting M and K stars that are not synchronously rotating could have much less hysteresis associated with the snowball bifurcations than they would if they were rapidly rotating. This implies that the amount of time it takes them to escape a snowball state via CO2 outgassing would be greatly reduced, as would the period of cycling between the warm and snowball state if they have low CO2 outgassing rates.

  9. Impact of absorbing aerosol deposition on snow albedo reduction over the southern Tibetan plateau based on satellite observations

    Science.gov (United States)

    Lee, Wei-Liang; Liou, K. N.; He, Cenlin; Liang, Hsin-Chien; Wang, Tai-Chi; Li, Qinbin; Liu, Zhenxin; Yue, Qing

    2017-08-01

    We investigate the snow albedo variation in spring over the southern Tibetan Plateau induced by the deposition of light-absorbing aerosols using remote sensing data from moderate resolution imaging spectroradiometer (MODIS) aboard Terra satellite during 2001-2012. We have selected pixels with 100 % snow cover for the entire period in March and April to avoid albedo contamination by other types of land surfaces. A model simulation using GEOS-Chem shows that aerosol optical depth (AOD) is a good indicator for black carbon and dust deposition on snow over the southern Tibetan Plateau. The monthly means of satellite-retrieved land surface temperature (LST) and AOD over 100 % snow-covered pixels during the 12 years are used in multiple linear regression analysis to derive the empirical relationship between snow albedo and these variables. Along with the LST effect, AOD is shown to be an important factor contributing to snow albedo reduction. We illustrate through statistical analysis that a 1-K increase in LST and a 0.1 increase in AOD indicate decreases in snow albedo by 0.75 and 2.1 % in the southern Tibetan Plateau, corresponding to local shortwave radiative forcing of 1.5 and 4.2 W m-2, respectively.

  10. Improving accessibility and discovery of ESA planetary data through the new planetary science archive

    Science.gov (United States)

    Macfarlane, A. J.; Docasal, R.; Rios, C.; Barbarisi, I.; Saiz, J.; Vallejo, F.; Besse, S.; Arviset, C.; Barthelemy, M.; De Marchi, G.; Fraga, D.; Grotheer, E.; Heather, D.; Lim, T.; Martinez, S.; Vallat, C.

    2018-01-01

    The Planetary Science Archive (PSA) is the European Space Agency's (ESA) repository of science data from all planetary science and exploration missions. The PSA provides access to scientific data sets through various interfaces at http://psa.esa.int. Mostly driven by the evolution of the PDS standards which all new ESA planetary missions shall follow and the need to update the interfaces to the archive, the PSA has undergone an important re-engineering. In order to maximise the scientific exploitation of ESA's planetary data holdings, significant improvements have been made by utilising the latest technologies and implementing widely recognised open standards. To facilitate users in handling and visualising the many products stored in the archive which have spatial data associated, the new PSA supports Geographical Information Systems (GIS) by implementing the standards approved by the Open Geospatial Consortium (OGC). The modernised PSA also attempts to increase interoperability with the international community by implementing recognised planetary science specific protocols such as the PDAP (Planetary Data Access Protocol) and EPN-TAP (EuroPlanet-Table Access Protocol). In this paper we describe some of the methods by which the archive may be accessed and present the challenges that are being faced in consolidating data sets of the older PDS3 version of the standards with the new PDS4 deliveries into a single data model mapping to ensure transparent access to the data for users and services whilst maintaining a high performance.

  11. The price of snow: albedo valuation and a case study for forest management

    International Nuclear Information System (INIS)

    Lutz, David A; Howarth, Richard B

    2015-01-01

    Several climate frameworks have included the role of carbon storage in natural landscapes as a potential mechanism for climate change mitigation. This has resulted in an incentive to grow and maintain intact long-lived forest ecosystems. However, recent research has suggested that the influence of albedo-related radiative forcing can impart equal and in some cases greater magnitudes of climate mitigation compared to carbon storage in forests where snowfall is common and biomass is slow-growing. While several methodologies exist for relating albedo-associated radiative forcing to carbon storage for the analysis of the tradeoffs of these ecosystem services, they are varied, and they have yet to be contrasted in a case study with implications for future forest management. Here we utilize four methodologies for calculating a shadow price for albedo radiative forcing and apply the resulting eight prices to an ecological and economic forest model to examine the effects on optimal rotation periods on two different forest stands in the White Mountain National Forest in New Hampshire, USA. These pricing methodologies produce distinctly different shadow prices of albedo, varying from a high of 9.36 × 10 −4 and a low of 1.75 × 10 −5 $w −1 yr −1 in the initial year, to a high of 0.019 and a low of 3.55 × 10 −4 $w −1 yr −1 in year 200 of the simulation. When implemented in the forest model, optimal rotation periods also varied considerably, from a low of 2 to a high of 107 years for a spruce-fir stand and from 35 to 80 years for a maple-beech-birch stand. Our results suggest that the choice of climate metrics and pricing methodologies for use with forest albedo alter albedo prices considerably, may substantially adjust optimal rotation period length, and therefore may have consequences with respect to forest land cover change. (letter)

  12. Effect of satellite formations and imaging modes on global albedo estimation

    Science.gov (United States)

    Nag, Sreeja; Gatebe, Charles K.; Miller, David W.; de Weck, Olivier L.

    2016-05-01

    We confirm the applicability of using small satellite formation flight for multi-angular earth observation to retrieve global, narrow band, narrow field-of-view albedo. The value of formation flight is assessed using a coupled systems engineering and science evaluation model, driven by Model Based Systems Engineering and Observing System Simulation Experiments. Albedo errors are calculated against bi-directional reflectance data obtained from NASA airborne campaigns made by the Cloud Absorption Radiometer for the seven major surface types, binned using MODIS' land cover map - water, forest, cropland, grassland, snow, desert and cities. A full tradespace of architectures with three to eight satellites, maintainable orbits and imaging modes (collective payload pointing strategies) are assessed. For an arbitrary 4-sat formation, changing the reference, nadir-pointing satellite dynamically reduces the average albedo error to 0.003, from 0.006 found in the static referencecase. Tracking pre-selected waypoints with all the satellites reduces the average error further to 0.001, allows better polar imaging and continued operations even with a broken formation. An albedo error of 0.001 translates to 1.36 W/m2 or 0.4% in Earth's outgoing radiation error. Estimation errors are found to be independent of the satellites' altitude and inclination, if the nadir-looking is changed dynamically. The formation satellites are restricted to differ in only right ascension of planes and mean anomalies within slotted bounds. Three satellites in some specific formations show average albedo errors of less than 2% with respect to airborne, ground data and seven satellites in any slotted formation outperform the monolithic error of 3.6%. In fact, the maximum possible albedo error, purely based on angular sampling, of 12% for monoliths is outperformed by a five-satellite formation in any slotted arrangement and an eight satellite formation can bring that error down four fold to 3%. More than

  13. Galactic planetary science.

    Science.gov (United States)

    Tinetti, Giovanna

    2014-04-28

    Planetary science beyond the boundaries of our Solar System is today in its infancy. Until a couple of decades ago, the detailed investigation of the planetary properties was restricted to objects orbiting inside the Kuiper Belt. Today, we cannot ignore that the number of known planets has increased by two orders of magnitude nor that these planets resemble anything but the objects present in our own Solar System. Whether this fact is the result of a selection bias induced by the kind of techniques used to discover new planets--mainly radial velocity and transit--or simply the proof that the Solar System is a rarity in the Milky Way, we do not know yet. What is clear, though, is that the Solar System has failed to be the paradigm not only in our Galaxy but even 'just' in the solar neighbourhood. This finding, although unsettling, forces us to reconsider our knowledge of planets under a different light and perhaps question a few of the theoretical pillars on which we base our current 'understanding'. The next decade will be critical to advance in what we should perhaps call Galactic planetary science. In this paper, I review highlights and pitfalls of our current knowledge of this topic and elaborate on how this knowledge might arguably evolve in the next decade. More critically, I identify what should be the mandatory scientific and technical steps to be taken in this fascinating journey of remote exploration of planets in our Galaxy.

  14. Development, Deployment, and Assessment of Dynamic Geological and Geophysical Models Using the Google Earth APP and API: Implications for Undergraduate Education in the Earth and Planetary Sciences

    Science.gov (United States)

    de Paor, D. G.; Whitmeyer, S. J.; Gobert, J.

    2009-12-01

    We previously reported on innovative techniques for presenting data on virtual globes such as Google Earth using emergent Collada models that reveal subsurface geology and geophysics. We here present several new and enhanced models and linked lesson plans to aid deployment in undergraduate geoscience courses, along with preliminary results from our assessment of their effectiveness. The new Collada models are created with Google SketchUp, Bonzai3D, and MeshLab software, and are grouped to cover (i) small scale field mapping areas; (ii) regional scale studies of the North Atlantic Ocean Basin, the Appalachian Orogen, and the Pacific Ring of Fire; and (iii) global scale studies of terrestrial planets, moons, and asteroids. Enhancements include emergent block models with three-dimensional surface topography; models that conserve structural orientation data; interactive virtual specimens; models that animate plate movements on the virtual globe; exploded 3-D views of planetary mantles and cores; and server-generated dynamic KML. We tested volunteer students and professors using Silverback monitoring software, think-aloud verbalizations, and questionnaires designed to assess their understanding of the underlying geo-scientific phenomena. With the aid of a cohort of instructors across the U.S., we are continuing to assess areas in which users encounter difficulties with both the software and geoscientific concepts. Preliminary results suggest that it is easy to overestimate the computer expertise of novice users even when they are content knowledge experts (i.e., instructors), and that a detailed introduction to virtual globe manipulation is essential before moving on to geoscience applications. Tasks that seem trivial to developers may present barriers to non-technical users and technicalities that challenge instructors may block adoption in the classroom. We have developed new models using the Google Earth API which permits enhanced interaction and dynamic feedback and

  15. NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos

    Energy Technology Data Exchange (ETDEWEB)

    Masiero, Joseph R.; Mainzer, A. K.; Kramer, E. [Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 183-301, Pasadena, CA 91109 (United States); Nugent, C.; Cutri, R. M. [California Institute of Technology, Infrared Processing and Analysis Center, 1200 California Boulevard, Pasadena, CA 91125 (United States); Wright, E. L. [University of California, Los Angeles, CA 90095 (United States); Bauer, J. M. [University of Maryland, College Park, MD 20742 (United States); Grav, T.; Sonnett, S., E-mail: Joseph.Masiero@jpl.nasa.gov [Planetary Science Institute, 1700 E Fort Lowell Road #106, Tucson, AZ 85719 (United States)

    2017-10-01

    The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 and 4.6  μ m of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper, we present thermal model fits of asteroid diameters for 170 NEOs and 6110 Main Belt asteroids (MBAs) detected during the third year of the survey, as well as the associated optical geometric albedos. We compare our results with previous thermal model results from NEOWISE for overlapping sample sets, as well as diameters determined through other independent methods, and find that our diameter measurements for NEOs agree to within 26% (1 σ ) of previously measured values. Diameters for the MBAs are within 17% (1 σ ). This brings the total number of unique near-Earth objects characterized by the NEOWISE survey to 541, surpassing the number observed during the fully cryogenic mission in 2010.

  16. Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

    OpenAIRE

    H. S. Negi; A. Kokhanovsky

    2010-01-01

    In the present paper spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART) theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% measured error accuracy. Retrieved integrated albedo was found within ±6% difference with ground observed broa...

  17. High-albedo materials for reducing building cooling energy use

    Energy Technology Data Exchange (ETDEWEB)

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building`s envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  18. High-albedo materials for reducing building cooling energy use

    Energy Technology Data Exchange (ETDEWEB)

    Taha, H.; Sailor, D.; Akbari, H.

    1992-01-01

    One simple and effective way to mitigate urban heat islands, i.e., the higher temperatures in cities compared to those of the surrounds, and their negative impacts on cooling energy consumption is to use high-albedo materials on major urban surfaces such as rooftops, streets, sidewalks, school yards, and the exposed surfaces of parking lots. High-albedo materials can save cooling energy use by directly reducing the heat gain through a building's envelope (direct effect) and also by lowering the urban air temperature in the neighborhood of the building (indirect effect). This project is an attempt to address high-albedo materials for buildings and to perform measurements of roof coatings. We search for existing methods and materials to implement fighter colors on major building and urban surfaces. Their cost effectiveness are examined and the possible related technical, maintenance, and environmental problems are identified. We develop a method for measuring albedo in the field by studying the instrumentation aspects of such measurements. The surface temperature impacts of various albedo/materials in the actual outdoor environment are studied by measuring the surface temperatures of a variety of materials tested on an actual roof. We also generate an albedo database for several urban surfaces to serve as a reference for future use. The results indicate that high-albedo materials can have a large impact on the surface temperature regime. On clear sunny days, when the solar noon surface temperatures of conventional roofing materials were about 40{degrees}C (72{degrees}F) warmer than air, the surface temperature of high-albedo coatings were only about 5{degrees}C warmer than air. In the morning and in the late afternoon, the high-albedo materials were as cool as the air itself. While conventional roofing materials warm up by an average 0.055{degrees}C/(W m{sup {minus}2}), the high-albedo surfaces warm up by an average 0.015{degrees}C/(W m{sup {minus}2}).

  19. Climate warming feedback from mountain birch forest expansion: reduced albedo dominates carbon uptake.

    Science.gov (United States)

    de Wit, Heleen A; Bryn, Anders; Hofgaard, Annika; Karstensen, Jonas; Kvalevåg, Maria M; Peters, Glen P

    2014-07-01

    Expanding high-elevation and high-latitude forest has contrasting climate feedbacks through carbon sequestration (cooling) and reduced surface reflectance (warming), which are yet poorly quantified. Here, we present an empirically based projection of mountain birch forest expansion in south-central Norway under climate change and absence of land use. Climate effects of carbon sequestration and albedo change are compared using four emission metrics. Forest expansion was modeled for a projected 2.6 °C increase in summer temperature in 2100, with associated reduced snow cover. We find that the current (year 2000) forest line of the region is circa 100 m lower than its climatic potential due to land-use history. In the future scenarios, forest cover increased from 12% to 27% between 2000 and 2100, resulting in a 59% increase in biomass carbon storage and an albedo change from 0.46 to 0.30. Forest expansion in 2100 was behind its climatic potential, forest migration rates being the primary limiting factor. In 2100, the warming caused by lower albedo from expanding forest was 10 to 17 times stronger than the cooling effect from carbon sequestration for all emission metrics considered. Reduced snow cover further exacerbated the net warming feedback. The warming effect is considerably stronger than previously reported for boreal forest cover, because of the typically low biomass density in mountain forests and the large changes in albedo of snow-covered tundra areas. The positive climate feedback of high-latitude and high-elevation expanding forests with seasonal snow cover exceeds those of afforestation at lower elevation, and calls for further attention of both modelers and empiricists. The inclusion and upscaling of these climate feedbacks from mountain forests into global models is warranted to assess the potential global impacts. © 2013 John Wiley & Sons Ltd.

  20. Accounting for radiative forcing from albedo change in future global land-use scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Andrew D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Calvin, Katherine V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Collins, William D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Edmonds, James A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    We demonstrate the effectiveness of a new method for quantifying radiative forcing from land use and land cover change (LULCC) within an integrated assessment model, the Global Change Assessment Model (GCAM). The method relies on geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions derived from the Community Earth System Model. We find that conversion of 1 km² of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 and –0.71 nW/m² of globally averaged radiative forcing determined by the vegetation characteristics, snow dynamics, and atmospheric radiation environment characteristic within each of 151 regions we consider globally. Across a set of scenarios designed to span a range of potential future LULCC, we find LULCC forcing ranging from –0.06 to –0.29 W/m² by 2070 depending on assumptions regarding future crop yield growth and whether climate policy favors afforestation or bioenergy crops. Inclusion of this previously uncounted forcing in the policy targets driving future climate mitigation efforts leads to changes in fossil fuel emissions on the order of 1.5 PgC/yr by 2070 for a climate forcing limit of 4.5 Wm–2, corresponding to a 12–67 % change in fossil fuel emissions depending on the scenario. Scenarios with significant afforestation must compensate for albedo-induced warming through additional emissions reductions, and scenarios with significant deforestation need not mitigate as aggressively due to albedo-induced cooling. In all scenarios considered, inclusion of albedo forcing in policy targets increases forest and shrub cover globally.

  1. Merged Shape from Shading and Shape from Stereo for Planetary Topographic Mapping

    Science.gov (United States)

    Tyler, Laurence; Cook, Tony; Barnes, Dave; Parr, Gerhard; Kirk, Randolph

    2014-05-01

    Digital Elevation Models (DEMs) of the Moon and Mars have traditionally been produced from stereo imagery from orbit, or from the surface landers or rovers. One core component of image-based DEM generation is stereo matching to find correspondences between images taken from different viewpoints. Stereo matchers that rely mostly on textural features in the images can fail to find enough matched points in areas lacking in contrast or surface texture. This can lead to blank or topographically noisy areas in resulting DEMs. Fine depth detail may also be lacking due to limited precision and quantisation of the pixel matching process. Shape from shading (SFS), a two dimensional version of photoclinometry, utilizes the properties of light reflecting off surfaces to build up localised slope maps, which can subsequently be combined to extract topography. This works especially well on homogeneous surfaces and can recover fine detail. However the cartographic accuracy can be affected by changes in brightness due to differences in surface material, albedo and light scattering properties, and also by the presence of shadows. We describe here experimental research for the Planetary Robotics Vision Data Exploitation EU FP7 project (PRoViDE) into using stereo generated depth maps in conjunction with SFS to recover both coarse and fine detail of planetary surface DEMs. Our Large Deformation Optimisation Shape From Shading (LDOSFS) algorithm uses image data, illumination, viewing geometry and camera parameters to produce a DEM. A stereo-derived depth map can be used as an initial seed if available. The software uses separate Bidirectional Reflectance Distribution Function (BRDF) and SFS modules for iterative processing and to make the code more portable for future development. Three BRDF models are currently implemented: Lambertian, Blinn-Phong, and Oren-Nayar. A version of the Hapke reflectance function, which is more appropriate for planetary surfaces, is under development

  2. Short-Term Research Experiences with Teachers in Earth and Planetary Sciences and a Model for Integrating Research into Classroom Inquiry

    Science.gov (United States)

    Morgan, P.; Bloom, J. W.

    2006-12-01

    For the past three summers, we have worked with in-service teachers on image processing, planetary geology, and earthquake and volcano content modules using inquiry methods that ended with mini-research experiences. Although almost all were science teachers, very few could give a reasonable definition of science at the start of the modules, and very few had a basic grasp of the processes of scientific research and could not include substantive scientific inquiry into their lessons. To build research understanding and confidence, an instructor-student interaction model was used in the modules. Studies have shown that children who participate in classrooms as learning and inquiry communities develop more complex understandings. The same patterns of complex understandings have resulted in similarly structured professional communities of teachers. The model is based on professional communities, emphasizing from the beginning that inquiry is a form of research. Although the actual "research" component of the modules was short, the teachers were identified as professionals and researchers from the start. Research/inquiry participation is therefore an excellent example by which to allow their teachers to learn. Initially the teachers were very reluctant to pose questions. As they were encouraged to share, collaborate, and support each other, the role of the instructor became less of a leader and more of a facilitator, and the confidence of the teachers as professionals and researchers grew. One teacher even remarked, "This is how we should be teaching our kids!' Towards the end of the modules the teachers were ready for their mini- research projects and collaborated in teams of 2-4. They selected their own research topics, but were guided toward research questions that required data collection (from existing studies), some data manipulation, interpretation, and drawing conclusions with respect to the original question. The teachers were enthusiastic about all of their

  3. Visualization Tools for Planetary Data

    Science.gov (United States)

    DeWolfe, Alexandria; Larsen, Kristopher; Brain, David; Chaffin, Michael; Harter, Bryan; Putnam, Brian

    2017-04-01

    We have developed a set of software tools for displaying and analyzing data from the MAVEN and MMS missions. In order to better visualize the science data and models, we have constructed 3D visualizations of MAVEN orbiting Mars and MMS orbiting Earth using the CesiumJS library. These visualizations allow viewing of not only spacecraft orientation and position over time, but also scientific data from the spacecraft, and atmospheric models as well. We have also developed a Python toolkit which replicates the functionality of the widely-used IDL "tplot" toolkit for analyzing planetary atmospheric data. We use the bokeh and matplotlib libraries to generate interactive line plots and spectrograms, providing additional functionality beyond the capabilities of IDL graphics. These Python tools are generalized to work with missions beyond MAVEN, and our open-source software is available on Github.

  4. PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

    Science.gov (United States)

    Juvan, Ines G.; Lendl, M.; Cubillos, P. E.; Fossati, L.; Tregloan-Reed, J.; Lammer, H.; Guenther, E. W.; Hanslmeier, A.

    2018-02-01

    Several studies have shown that stellar activity features, such as occulted and non-occulted starspots, can affect the measurement of transit parameters biasing studies of transit timing variations and transmission spectra. We present PyTranSpot, which we designed to model multiband transit light curves showing starspot anomalies, inferring both transit and spot parameters. The code follows a pixellation approach to model the star with its corresponding limb darkening, spots, and transiting planet on a two dimensional Cartesian coordinate grid. We combine PyTranSpot with a Markov chain Monte Carlo framework to study and derive exoplanet transmission spectra, which provides statistically robust values for the physical properties and uncertainties of a transiting star-planet system. We validate PyTranSpot's performance by analyzing eleven synthetic light curves of four different star-planet systems and 20 transit light curves of the well-studied WASP-41b system. We also investigate the impact of starspots on transit parameters and derive wavelength dependent transit depth values for WASP-41b covering a range of 6200-9200 Å, indicating a flat transmission spectrum.

  5. Electron energy and charge albedos - calorimetric measurement vs Monte Carlo theory

    International Nuclear Information System (INIS)

    Lockwood, G.J.; Ruggles, L.E.; Miller, G.H.; Halbleib, J.A.

    1981-11-01

    A new calorimetric method has been employed to obtain saturated electron energy albedos for Be, C, Al, Ti, Mo, Ta, U, and UO 2 over the range of incident energies from 0.1 to 1.0 MeV. The technique was so designed to permit the simultaneous measurement of saturated charge albedos. In the cases of C, Al, Ta, and U the measurements were extended down to about 0.025 MeV. The angle of incidence was varied from 0 0 (normal) to 75 0 in steps of 15 0 , with selected measurements at 82.5 0 in Be and C. In each case, state-of-the-art predictions were obtained from a Monte Carlo model. The generally good agreement between theory and experiment over this extensive parameter space represents a strong validation of both the theoretical model and the new experimental method. Nevertheless, certain discrepancies at low incident energies, especially in high-atomic-number materials, and at all energies in the case of the U energy albedos are not completely understood

  6. HIGH-RESOLUTION IMAGING OF THE GEGENSCHEIN AND THE GEOMETRIC ALBEDO OF INTERPLANETARY DUST

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru; Yang, Hongu [Astronomy Program, Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Usui, Fumihiko [Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science (ISAS), JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Pyo, Jeonghyun [Korea Astronomy and Space Science Institute (KASI), Daejeon 305-348 (Korea, Republic of); Ueno, Munetaka [Institute of Space and Astronautical Science (ISAS), JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Ootsubo, Takafumi [Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Kwon, Suk Minn [Department of Science Education, Kangwon National University, 192-1 Hyoja-dong, Kangwon-do, Chunchon 200-701 (Korea, Republic of); Mukai, Tadashi, E-mail: ishiguro@astro.snu.ac.kr [Department of Earth and Planetary Sciences, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501 (Japan)

    2013-04-10

    We performed optical observations of the Gegenschein using a liquid-nitrogen-cooled wide-field camera, the Wide-field Imager of Zodiacal light with ARray Detector (WIZARD), between 2003 March and 2006 November. We found a narrow brightness enhancement superimposed on the smooth gradient of the Gegenschein at the exact position of the antisolar point. Whereas the Gegenschein morphology changed according to the orbital motion of the Earth, the maximum brightness coincided with the antisolar direction throughout the year. We compared the observed morphology of the Gegenschein with those of models in which the spatial density of the interplanetary dust cloud was considered and found that the volume scattering phase function had a narrow backscattering enhancement. The morphology was reproducible with a spatial distribution model for infrared zodiacal emission. It is likely that the zero-phase peak (the so-called opposition effect) was caused by coherent backscattering and/or shadow-hiding effects on the rough surfaces of individual dust particles. These results suggest that big particles are responsible for both zodiacal light and zodiacal emission. Finally, we derived the geometric albedo of the smooth component of interplanetary dust, assuming big particles, and obtained a geometric albedo of 0.06 {+-} 0.01. The derived albedo is in accordance with collected dark micrometeorites and observed cometary dust particles. We concluded that chondritic particles are dominant near Earth space, supporting the recent theoretical study by dynamical simulation.

  7. The role of sea-ice albedo in the climate of slowly rotating aquaplanets

    Science.gov (United States)

    Salameh, Josiane; Popp, Max; Marotzke, Jochem

    2018-04-01

    We investigate the influence of the rotation period (P_{rot}) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing P_{rot} and sea ice expands equatorwards. The cooling of the mean climate with increasing P_{rot} is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation.

  8. Derivation of high spatial resolution albedo from UAV digital imagery: application over the Greenland Ice Sheet

    Science.gov (United States)

    Ryan, Jonathan C.; Hubbard, Alun; Box, Jason E.; Brough, Stephen; Cameron, Karen; Cook, Joseph M.; Cooper, Matthew; Doyle, Samuel H.; Edwards, Arwyn; Holt, Tom; Irvine-Fynn, Tristram; Jones, Christine; Pitcher, Lincoln H.; Rennermalm, Asa K.; Smith, Laurence C.; Stibal, Marek; Snooke, Neal

    2017-05-01

    Measurements of albedo are a prerequisite for modelling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimetre resolution albedo products with accuracies of 5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique will likely become increasingly attractive in field studies and used in a wide range of applications for high temporal and spatial resolution surface mapping of debris, dust, cryoconite and bioalbedo and for directly constraining surface energy balance models.

  9. Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia

    Science.gov (United States)

    Evans, Jason P.; Meng, Xianhong; McCabe, Matthew F.

    2017-01-01

    In this study, we have examined the ability of a regional climate model (RCM) to simulate the extended drought that occurred throughout the period of 2002 through 2007 in south-east Australia. In particular, the ability to reproduce the two drought peaks in 2002 and 2006 was investigated. Overall, the RCM was found to reproduce both the temporal and the spatial structure of the drought-related precipitation anomalies quite well, despite using climatological seasonal surface characteristics such as vegetation fraction and albedo. This result concurs with previous studies that found that about two-thirds of the precipitation decline can be attributed to the El Niño-Southern Oscillation (ENSO). Simulation experiments that allowed the vegetation fraction and albedo to vary as observed illustrated that the intensity of the drought was underestimated by about 10 % when using climatological surface characteristics. These results suggest that in terms of drought development, capturing the feedbacks related to vegetation and albedo changes may be as important as capturing the soil moisture-precipitation feedback. In order to improve our modelling of multi-year droughts, the challenge is to capture all these related surface changes simultaneously, and provide a comprehensive description of land surface-precipitation feedback during the droughts development.

  10. Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia

    KAUST Repository

    Evans, Jason P.

    2017-01-24

    In this study, we have examined the ability of a regional climate model (RCM) to simulate the extended drought that occurred throughout the period of 2002 through 2007 in south-east Australia. In particular, the ability to reproduce the two drought peaks in 2002 and 2006 was investigated. Overall, the RCM was found to reproduce both the temporal and the spatial structure of the drought-related precipitation anomalies quite well, despite using climatological seasonal surface characteristics such as vegetation fraction and albedo. This result concurs with previous studies that found that about two-thirds of the precipitation decline can be attributed to the El Ninõ–Southern Oscillation (ENSO). Simulation experiments that allowed the vegetation fraction and albedo to vary as observed illustrated that the intensity of the drought was underestimated by about 10ĝ% when using climatological surface characteristics. These results suggest that in terms of drought development, capturing the feedbacks related to vegetation and albedo changes may be as important as capturing the soil moisture–precipitation feedback. In order to improve our modelling of multi-year droughts, the challenge is to capture all these related surface changes simultaneously, and provide a comprehensive description of land surface–precipitation feedback during the droughts development.

  11. Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet

    Directory of Open Access Journals (Sweden)

    Jonathan C. Ryan

    2017-05-01

    Full Text Available Measurements of albedo are a prerequisite for modeling surface melt across the Earth's cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimeter resolution albedo products with accuracies of ±5% using consumer-grade digital camera and unmanned aerial vehicle (UAV technologies. Our method comprises a workflow for processing, correcting and calibrating raw digital images using a white reference target, and upward and downward shortwave radiation measurements from broadband silicon pyranometers. We demonstrate the method with a set of UAV sorties over the western, K-sector of the Greenland Ice Sheet. The resulting albedo product, UAV10A1, covers 280 km2, at a resolution of 20 cm per pixel and has a root-mean-square difference of 3.7% compared to MOD10A1 and 4.9% compared to ground-based broadband pyranometer measurements. By continuously measuring downward solar irradiance, the technique overcomes previous limitations due to variable illumination conditions during and between surveys over glaciated terrain. The current miniaturization of multispectral sensors and incorporation of upward facing radiation sensors on UAV packages means that this technique could become increasingly common in field studies and used for a wide range of applications. These include the mapping of debris, dust, cryoconite and bioalbedo, and directly constraining surface energy balance models.

  12. Revised planetary protection policy for solar system exploration

    Science.gov (United States)

    Devincenzi, D. L.; Stabekis, P. D.

    1984-01-01

    In order to control contamination of planets by terrestrial microorganisms and organic constituents, U.S. planetary missions have been governed by a planetary protection (or planetary quarantine) policy which has changed little since 1972. This policy has recently been reviewed in light of new information obtained from planetary exploration during the past decade and because of changes to, or uncertainties in, some parameters used in the existing quantitative approach. On the basis of this analysis, a revised planetary protection policy with the following key features is proposed: deemphasizing the use of mathematical models and quantitative analyses; establishing requirements for target planet/mission type (i.e., Orbiter, Lander, etc.) combinations; considering sample return missions a separate category; simplifying documentation; and imposing implementing procedures (i.e., trajectory biasing, cleanroom assembly, spacecraft sterilization, etc.) by exception, i.e., only if the planet/mission combination warrants such controls.

  13. Constraining the instantaneous aerosol influence on cloud albedo

    Energy Technology Data Exchange (ETDEWEB)

    Gryspeerdt, Edward; Quaas, Johannes; Ferrachat, Sylvaine; Gettelman, Andrew; Ghan, Steven; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G.; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Wang, Minghuai; Zhang, Kai

    2017-04-26

    Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol–cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol–climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol–cloud interactions in satellite data.

  14. Constraining the instantaneous aerosol influence on cloud albedo

    Science.gov (United States)

    Quaas, Johannes; Ferrachat, Sylvaine; Gettelman, Andrew; Ghan, Steven; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G.; Takemura, Toshihiko; Wang, Hailong; Wang, Minghuai; Zhang, Kai

    2017-01-01

    Much of the uncertainty in estimates of the anthropogenic forcing of climate change comes from uncertainties in the instantaneous effect of aerosols on cloud albedo, known as the Twomey effect or the radiative forcing from aerosol–cloud interactions (RFaci), a component of the total or effective radiative forcing. Because aerosols serving as cloud condensation nuclei can have a strong influence on the cloud droplet number concentration (Nd), previous studies have used the sensitivity of the Nd to aerosol properties as a constraint on the strength of the RFaci. However, recent studies have suggested that relationships between aerosol and cloud properties in the present-day climate may not be suitable for determining the sensitivity of the Nd to anthropogenic aerosol perturbations. Using an ensemble of global aerosol–climate models, this study demonstrates how joint histograms between Nd and aerosol properties can account for many of the issues raised by previous studies. It shows that if the anthropogenic contribution to the aerosol is known, the RFaci can be diagnosed to within 20% of its actual value. The accuracy of different aerosol proxies for diagnosing the RFaci is investigated, confirming that using the aerosol optical depth significantly underestimates the strength of the aerosol–cloud interactions in satellite data. PMID:28446614

  15. Multiple zonal jets and convective heat transport barriers in a quasi-geostrophic model of planetary cores

    Science.gov (United States)

    Guervilly, C.; Cardin, P.

    2017-10-01

    We study rapidly rotating Boussinesq convection driven by internal heating in a full sphere. We use a numerical model based on the quasi-geostrophic approximation for the velocity field, whereas the temperature field is 3-D. This approximation allows us to perform simulations for Ekman numbers down to 10-8, Prandtl numbers relevant for liquid metals (˜10-1) and Reynolds numbers up to 3 × 104. Persistent zonal flows composed of multiple jets form as a result of the mixing of potential vorticity. For the largest Rayleigh numbers computed, the zonal velocity is larger than the convective velocity despite the presence of boundary friction. The convective structures and the zonal jets widen when the thermal forcing increases. Prograde and retrograde zonal jets are dynamically different: in the prograde jets (which correspond to weak potential vorticity gradients) the convection transports heat efficiently and the mean temperature tends to be homogenized; by contrast, in the cores of the retrograde jets (which correspond to steep gradients of potential vorticity) the dynamics is dominated by the propagation of Rossby waves, resulting in the formation of steep mean temperature gradients and the dominance of conduction in the heat transfer process. Consequently, in quasi-geostrophic systems, the width of the retrograde zonal jets controls the efficiency of the heat transfer.

  16. Large-Scale Flows and Magnetic Fields Produced by Rotating Convection in a Quasi-Geostrophic Model of Planetary Cores

    Science.gov (United States)

    Guervilly, C.; Cardin, P.

    2017-12-01

    Convection is the main heat transport process in the liquid cores of planets. The convective flows are thought to be turbulent and constrained by rotation (corresponding to high Reynolds numbers Re and low Rossby numbers Ro). Under these conditions, and in the absence of magnetic fields, the convective flows can produce coherent Reynolds stresses that drive persistent large-scale zonal flows. The formation of large-scale flows has crucial implications for the thermal evolution of planets and the generation of large-scale magnetic fields. In this work, we explore this problem with numerical simulations using a quasi-geostrophic approximation to model convective and zonal flows at Re 104 and Ro 10-4 for Prandtl numbers relevant for liquid metals (Pr 0.1). The formation of intense multiple zonal jets strongly affects the convective heat transport, leading to the formation of a mean temperature staircase. We also study the generation of magnetic fields by the quasi-geostrophic flows at low magnetic Prandtl numbers.

  17. Quasi-Stationary Planetary Wave in the MLT During Summer

    Science.gov (United States)

    Stray, N. H.; Espy, P. J.; Hibbins, R. E.

    2014-12-01

    A network of 8 northern hemispheric SuperDARN radars (51-66N) has been used to study planetary wave activity in the mesosphere lower thermosphere (MLT). The meridional meteor winds from the longitudinally spaced SuperDARN network are used to derive the planetary wave activity with zonal wave numbers 1 and 2 in the polar summer MLT (~95 km). In addition planetary wave amplitudes throughout the middle atmosphere have been retrieved from the meridional wind data of the Modern-Era Retrospective Analysis for Research and Application (MERRA) of the NASA Global Modelling and Assimilation Office. The fitting technique used to derive the planetary wave amplitudes will be presented, and it will be shown that there are strong quasi-stationary longitudinal differences in the strength of the meridional wind in the MLT during summer which can be described as a quasi-stationary planetary wave number 1. The ground-based network allows this planetary wave to be separated from tidal perturbations that are aliased in satellite observations, and the combination of these two data sets provides evidence that the mesopause planetary wave activity is produced in situ in the MLT rather than propagating upwards from lower altitudes. Finally, the impact of this planetary wave feature on Polar Mesospheric Clouds (PMC) and Polar Mesospheric Summer Echoes (PMSE) will be discussed.

  18. Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

    Science.gov (United States)

    2004-01-01

    Reports included:Long Term Stability of Mars Trojans; Horseshoe Asteroids and Quasi-satellites in Earth-like Orbits; Effect of Roughness on Visible Reflectance Spectra of Planetary Surface; SUBARU Spectroscopy of Asteroid (832) Karin; Determining Time Scale of Space Weathering; Change of Asteroid Reflectance Spectra by Space Weathering: Pulse Laser Irradiation on Meteorite Samples; Reflectance Spectra of CM2 Chondrite Mighei Irradiated with Pulsed Laser and Implications for Low-Albedo Asteroids and Martian Moons; Meteorite Porosities and Densities: A Review of Trends in the Data; Small Craters in the Inner Solar System: Primaries or Secondaries or Both?; Generation of an Ordinary-Chondrite Regolith by Repetitive Impact; Asteroid Modal Mineralogy Using Hapke Mixing Models: Validation with HED Meteorites; Particle Size Effect in X-Ray Fluorescence at a Large Phase Angle: Importance on Elemental Analysis of Asteroid Eros (433); An Investigation into Solar Wind Depletion of Sulfur in Troilite; Photometric Behaviour Dependent on Solar Phase Angle and Physical Characteristics of Binary Near-Earth-Asteroid (65803) 1996 GT; Spectroscopic Observations of Asteroid 4 Vesta from 1.9 to 3.5 micron: Evidence of Hydrated and/or Hydroxylated Minerals; Multi-Wavelength Observations of Asteroid 2100 Ra-Shalom: Visible, Infrared, and Thermal Spectroscopy Results; New Peculiarities of Cometary Outburst Activity; Preliminary Shape Modeling for the Asteroid (25143) Itokawa, AMICA of Hayabusa Mission; Scientific Capability of MINERVA Rover in Hayabusa Asteroid Mission; Characteristics and Current Status of Near Infrared Spectrometer for Hayabusa Mission; Sampling Strategy and Curation Plan of Hayabusa Asteroid Sample Return Mission; Visible/Near-Infrared Spectral Properties of MUSES C Target Asteroid 25143 Itokawa; Calibration of the NEAR XRS Solar Monitor; Modeling Mosaic Degradation of X-Ray Measurements of 433 Eros by NEAR-Shoemaker; Scattered Light Remediation and Recalibration of

  19. Size and Albedo of Irregular Saturnian Satellites from Spitzer Observations

    Science.gov (United States)

    Mueller, Michael; Grav, T.; Trilling, D.; Stansberry, J.; Sykes, M.

    2008-09-01

    Using MIPS onboard the Spitzer Space Telescope, we observed the thermal emission (24 and, for some targets, 70 um) of eight irregular satellites of Saturn: Albiorix, Siarnaq, Paaliaq, Kiviuq, Ijiraq, Tarvos, Erriapus, and Ymir. We determined the size and albedo of all targets. An analysis of archived MIPS observations of Phoebe reproduces Cassini results very accurately, thereby validating our method. For all targets, the geometric albedo is found to be low, probably below 10% and clearly below 15%. Irregular satellites are much darker than the large regular satellites. Their albedo is, however, quite similar to that of small bodies in the outer Solar System (such as cometary nuclei, Jupiter Trojans, or TNOs). This is consistent with color measurements as well as dynamical considerations which suggest a common origin of the said populations. There appear to be significant object-to-object albedo differences. Similar albedos found for some members of dynamical clusters support the idea that they may have originated in the breakup of a parent body. For three satellites, thermal data at two wavelengths are available, enabling us to constrain their thermal properties. Sub-solar temperatures are similar to that found from Cassini's Phoebe fly-by. This suggests a rather low thermal inertia, as expected for regolith-covered objects. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL under a contract with NASA. Support for this work was provided by NASA.

  20. Occurrence of lower cloud albedo in ship tracks

    Directory of Open Access Journals (Sweden)

    Y.-C. Chen

    2012-09-01

    Full Text Available The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air, nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

  1. Tundra vegetation effects on pan-Arctic albedo

    International Nuclear Information System (INIS)

    Loranty, Michael M; Goetz, Scott J; Beck, Pieter S A

    2011-01-01

    Recent field experiments in tundra ecosystems describe how increased shrub cover reduces winter albedo, and how subsequent changes in surface net radiation lead to altered rates of snowmelt. These findings imply that tundra vegetation change will alter regional energy budgets, but to date the effects have not been documented at regional or greater scales. Using satellite observations and a pan-Arctic vegetation map, we examined the effects of shrub vegetation on albedo across the terrestrial Arctic. We included vegetation classes dominated by low shrubs, dwarf shrubs, tussock-dominated graminoid tundra, and non-tussock graminoid tundra. Each class was further stratified by bioclimate subzones. Low-shrub tundra had higher normalized difference vegetation index values and earlier albedo decline in spring than dwarf-shrub tundra, but for tussock tundra, spring albedo declined earlier than for low-shrub tundra. Our results illustrate how relatively small changes in vegetation properties result in differences in albedo dynamics, regardless of shrub growth, that may lead to differences in net radiation upwards of 50 W m -2 at weekly time scales. Further, our findings imply that changes to the terrestrial Arctic energy budget during this important seasonal transition are under way regardless of whether recent satellite observed productivity trends are the result of shrub expansion. We conclude that a better understanding of changes in vegetation productivity and distribution in Arctic tundra is essential for accurately quantifying and predicting carbon and energy fluxes and associated climate feedbacks.

  2. Thermal-Infrared Surveys of Near-Earth Object Diameters and Albedos with Spitzer and IRTF/MIRSI

    Science.gov (United States)

    Mommert, Michael; Trilling, David; Hora, Joseph L.; Chesley, Steven; Emery, Josh; Fazio, Giovanni; Harris, Alan W.; Moskovitz, Nick; Mueller, Michael; Smith, Howard

    2015-08-01

    More than 12000 Near-Earth Objects (NEOs) have been discovered over the past few decades and current discovery surveys find on average 4 new NEOs every night. In comparison to asteroid discovery, the physical characterization of NEOs lags far behind: measured diameters and albedos exist only for roughly 10% of all known NEOs. We describe a current and a future observing program that provide diameter and albedo measurements of a large number of NEOs.In our Spitzer Space Telescope Exploration Science program 'NEOSurvey', we are performing a fast and efficient flux-limited survey in which we measure the diameters and albedos of ~600 NEOs in a total of 710 hrs of observing time. We measure the thermal emission of our targets at 4.5 micron and combine these measurements with optical data in a thermal model. Our diameters and albedos come with highly realistic uncertainties that account for a wide range of potential asteroid properties. Our primary goal is to create a large and uniform catalog of NEO properties, including diameters, albedos, and flux density data. This catalog is publicly accessible and provides the latest results usually within 2 weeks after the observation.Starting in 2016, we will also make use of the refurbished and recommissioned MIRSI mid-infrared imaging camera on NASA's InfraRed Telescope Facility (IRTF) to derive the diameters and albedos of up to 750 NEOs over a period of 3 yrs. MIRSI will be equipped with an optical camera that will allow for simultaneous optical imaging, which will improve our thermal modeling results. With MIRSI, we will focus on newly discovered NEOs that are close to Earth and hence relatively bright.The results from both programs, together with already exisiting diameter and albedo results from the literature, will form the largest database of NEO physical properties available to date. With this data set, we will be able to refine the size distribution of small NEOs and the corresponding impact frequency, and compare the

  3. The Influence of green areas and roof albedos on air temperatures during Extreme Heat Events in Berlin, Germany

    Directory of Open Access Journals (Sweden)

    Sebastian Schubert

    2013-04-01

    Full Text Available The mesoscale atmospheric model COSMO-CLM (CCLM with the Double Canyon Effect Parametrization Scheme (DCEP is applied to investigate possible adaption measures to extreme heat events (EHEs for the city of Berlin, Germany. The emphasis is on the effects of a modified urban vegetation cover and roof albedo on near-surface air temperatures. Five EHEs with a duration of 5 days or more are identified for the period 2000 to 2009. A reference simulation is carried out for each EHE with current vegetation cover, roof albedo and urban canopy parameters (UCPs, and is evaluated with temperature observations from weather stations in Berlin and its surroundings. The derivation of the UCPs from an impervious surface map and a 3-D building data set is detailed. Characteristics of the simulated urban heat island for each EHE are analysed in terms of these UCPs. In addition, six sensitivity runs are examined with a modified vegetation cover of each urban grid cell by -25%, 5% and 15%, with a roof albedo increased to 0.40 and 0.65, and with a combination of the largest vegetation cover and roof albedo, respectively. At the weather stations' grid cells, the results show a maximum of the average diurnal change in air temperature during each EHE of 0.82 K and -0.48 K for the -25% and 15% vegetation covers, -0.50 K for the roof albedos of 0.65, and -0.63 K for the combined vegetation and albedo case. The largest effects on the air temperature are detected during midday.

  4. MORSE/STORM: A generalized albedo option for Monte Carlo calculations

    International Nuclear Information System (INIS)

    Gomes, I.C.; Stevens, P.N.

    1991-09-01

    The advisability of using the albedo procedure for the Monte Carlo solution of deep penetration shielding problems that have ducts and other penetrations has been investigated. The use of albedo data can dramatically improve the computational efficiency of certain Monte Carlo calculations. However, the accuracy of these results may be unacceptable because of lost information during the albedo event and serious errors in the available differential albedo data. This study was done to evaluate and appropriately modify the MORSE/BREESE package, to develop new methods for generating the required albedo data, and to extend the adjoint capability to the albedo-modified calculations. Major modifications to MORSE/BREESE include an option to save for further use information that would be lost at the albedo event, an option to displace the point of emergence during an albedo event, and an option to use spatially dependent albedo data for both forward and adjoint calculations, which includes the point of emergence as a new random variable to be selected during an albedo event. The theoretical basis for using TORT-generated forward albedo information to produce adjuncton albedos was derived. The MORSE/STORM package was developed to perform both forward and adjoint modes of analysis using spatially dependent albedo data. Results obtained with MORSE/STORM for both forward and adjoint modes were compared with benchmark solutions. Excellent agreement and improved computational efficiency were achieved, demonstrating the full utilization of the albedo option in the MORSE code. 7 refs., 17 figs., 15 tabs

  5. A Multilayer Surface Temperature, Surface Albedo, and Water Vapor Product of Greenland from MODIS

    Directory of Open Access Journals (Sweden)

    Dorothy K. Hall

    2018-04-01

    Full Text Available A multilayer, daily ice surface temperature (IST–albedo–water vapor product of Greenland, extending from March 2000 through December 2016, has been developed using standard MODerate-resolution Imaging Spectroradiometer (MODIS data products from the Terra satellite. To meet the needs of the ice sheet modeling community, this new Earth Science Data Record (ESDR is provided in a polar stereographic projection in NetCDF format, and includes the existing standard MODIS Collection 6.1 IST and derived melt maps, and Collection 6 snow albedo and water vapor maps, along with ancillary data, and is provided at a spatial resolution of ~0.78 km. This ESDR enables relationships between IST, surface melt, albedo, and water vapor to be evaluated easily. We show examples of the components of the ESDR and describe some uses of the ESDR such as for comparison with skin temperature, albedo, and water vapor output from Modern Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2. Additionally, we show validation of the MODIS IST using in situ and aircraft data, and validation of MERRA-2 skin temperature maps using MODIS IST and in situ data. The ESDR has been assigned a DOI and will be available through the National Snow and Ice Data Center by the summer of 2018.

  6. Albedo Observation by Hayabusa2 LIDAR: Instrument Performance and Error Evaluation

    Science.gov (United States)

    Yamada, Ryuhei; Senshu, Hiroki; Namiki, Noriyuki; Mizuno, Takahide; Abe, Shinsuke; Yoshida, Fumi; Noda, Hirotomo; Hirata, Naru; Oshigami, Shoko; Araki, Hiroshi; Ishihara, Yoshiaki; Matsumoto, Koji

    2017-07-01

    The Japanese asteroid explorer Hayabusa2 was launched at the end of 2014. Hayabusa2 is supposed to observe the near-Earth C-type asteroid 162173 Ryugu (1999 JU3) and bring surface material samples back to Earth in 2020. It is equipped with Light Detection and Ranging (LIDAR) instrument for laser ranging which can be used to measure the intensities of transmitted and received pulses. The intensity data can be used to estimate the normal albedo of Ryugu at a laser wavelength of 1.064 μm. To perform this estimation, we determined the transfer functions of the laser module and receiver to convert the intensity data into pulse energies, along with the utilization ratio of the returned pulse energy, through verification tests of the LIDAR flight model. Then, we evaluated the error of the normal albedo. This error is affected not only by the performance of the LIDAR but also by the slope and roughness of the asteroid's surface. In this paper, we focus on the error in the normal albedo due only to the instrument error, which will be 18.0 % in an observation at a nominal altitude of 20 km.