WorldWideScience

Sample records for pseudolite tropospheric delay

  1. Performance Evaluation of Blind Tropospheric Delay correction ...

    African Journals Online (AJOL)

    Tropospheric delay is a major error source in positioning by Global Navigation Satellite Systems (GNSS). Many techniques are available for tropospheric delay mitigation consisting of surface meteorological models and global empirical models. Surface meteorological models need surface meteorological data to give high ...

  2. Integrity modelling of tropospheric delay models

    Science.gov (United States)

    Rózsa, Szabolcs; Bastiaan Ober, Pieter; Mile, Máté; Ambrus, Bence; Juni, Ildikó

    2017-04-01

    The effect of the neutral atmosphere on signal propagation is routinely estimated by various tropospheric delay models in satellite navigation. Although numerous studies can be found in the literature investigating the accuracy of these models, for safety-of-life applications it is crucial to study and model the worst case performance of these models using very low recurrence frequencies. The main objective of the INTegrity of TROpospheric models (INTRO) project funded by the ESA PECS programme is to establish a model (or models) of the residual error of existing tropospheric delay models for safety-of-life applications. Such models are required to overbound rare tropospheric delays and should thus include the tails of the error distributions. Their use should lead to safe error bounds on the user position and should allow computation of protection levels for the horizontal and vertical position errors. The current tropospheric model from the RTCA SBAS Minimal Operational Standards has an associated residual error that equals 0.12 meters in the vertical direction. This value is derived by simply extrapolating the observed distribution of the residuals into the tail (where no data is present) and then taking the point where the cumulative distribution has an exceedance level would be 10-7.While the resulting standard deviation is much higher than the estimated standard variance that best fits the data (0.05 meters), it surely is conservative for most applications. In the context of the INTRO project some widely used and newly developed tropospheric delay models (e.g. RTCA MOPS, ESA GALTROPO and GPT2W) were tested using 16 years of daily ERA-INTERIM Reanalysis numerical weather model data and the raytracing technique. The results showed that the performance of some of the widely applied models have a clear seasonal dependency and it is also affected by a geographical position. In order to provide a more realistic, but still conservative estimation of the residual

  3. Performance Evaluation of Blind Tropospheric Delay correction ...

    African Journals Online (AJOL)

    lekky

    2Hartebeesthoek Radio Astronomy Observatory (HartRAO), P. O. Box 443, Krugersdorp. 1740, South Africa, isioye@hartrao.ac.za. 3South African Weather Service, 442 Rigel Avenue South, Erasmusrand, Pretoria 0001,. South Africa. DOI: http://dx.doi.org/10.4314/sajg.v4i4.10. Abstract. Tropospheric delay is a major error ...

  4. Benchmarking ray-traced tropospheric delays

    Science.gov (United States)

    Nafisi, V.; Wijaya, D.; Boehm, J.; Schuh, H.; Hobiger, T.; Ichikawa, R.; Urquhart, L.; Santos, M. C.; Nievinski, F. G.; Zus, F.; Wickert, J.; Gegout, P.; Ardalan, A. A.

    2010-12-01

    Tropospheric propagation is a serious source of error in the analysis of space geodetic observations at radio wavelengths such as VLBI, GNSS, and DORIS. In recent years direct ray-tracing methods based on numerical weather models have been developed by different researchers in order to determine the true trajectory of a specific ray and its path delay in the troposphere. To evaluate and compare the results from different ray-tracing programs a benchmarking campaign was carried out under the umbrella of the International Association of Geodesy (IAG) Working Group 4.3.3 in the first half of 2010 with five institutions participating: German Research Centre for Geosciences (GFZ), Groupe de Recherche de Geodesie Spatiale (GRGS), National Institute of Information and Communication Technology (NICT), University of New Brunswick (UNB), and Institute of Geodesy and Geophysics (IGG). High-resolution ECMWF operational analysis pressure level data at the stations Tsukuba (Japan) and Wettzell (Germany) have been provided to the participants of the benchmarking campaign. The data consist of geopotential differences with respect to mean sea level, temperature, and specific humidity. Additionally, information about the geoid undulations was also provided and the participants were asked to compute the ray-traced total delays for various elevations (above 5 degrees) and azimuths. In general, we find good agreement with standard deviations below 1 cm between the ray-traced delays from the different solutions at 5 degrees elevation. Some small discrepancies are due to differences in the algorithm and the interpolation approaches. This benchmarking is very useful for the ray-tracers because it allows the validation of the results. Thus, these data sets and delays will be made available for the public, so that they can serve as reference for future ray-tracers.

  5. Combined zenithal tropospheric delay during CONT08

    Science.gov (United States)

    Pollet, A.; Coulot, D.; Bock, O.; Nahmani, S.

    2012-12-01

    CONT08 is a two-week campaign of continuous VLBI observations. The IERS working group on Combination at the Observation Level (COL) has chosen this campaign in order to study such combination. In the COL framework, the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies this approach, which directly combines the space geodetic observations of DORIS, GPS, SLR, and VLBI techniques using the same models and software for all the individual data processing. The purpose is to better use all the information provided by the different techniques through the interaction between the observations of the different techniques and to use more common parameters than a combination carried out at the solution level. In this work, combinations of DORIS, GPS, SLR, and VLBI technique measurements are studied during CONT08. We present different results concerning the use of common zenithal tropospheric delay (ZTD) during the combination. We compare the ZTD obtained separately with each individual technique data processing, the combined ZTD, and the ZTD derived from a meteorological model. We conclude with the benefit of the combined estimation of these parameters.

  6. Performance Evaluation of Blind Tropospheric Delay correction ...

    African Journals Online (AJOL)

    lekky

    2.0 Description of tropospheric correction models adopted in this study. 2.1 Saastamoinen model. Saastamoinen (1972) applied the gas laws to refractivity by considering the atmosphere as a mixture of dry air and water vapour. The model considers the temperature in the troposphere as decreasing with increasing height at ...

  7. Spatial Variability of Wet Troposphere Delays Over Inland Water Bodies

    Science.gov (United States)

    Mehran, Ali; Clark, Elizabeth A.; Lettenmaier, Dennis P.

    2017-11-01

    Satellite radar altimetry has enabled the study of water levels in large lakes and reservoirs at a global scale. The upcoming Surface Water and Ocean Topography (SWOT) satellite mission (scheduled launch 2020) will simultaneously measure water surface extent and elevation at an unprecedented accuracy and resolution. However, SWOT retrieval accuracy will be affected by a number of factors, including wet tropospheric delay—the delay in the signal's passage through the atmosphere due to atmospheric water content. In past applications, the wet tropospheric delay over large inland water bodies has been corrected using atmospheric moisture profiles based on atmospheric reanalysis data at relatively coarse (tens to hundreds of kilometers) spatial resolution. These products cannot resolve subgrid variations in wet tropospheric delays at the spatial resolutions (of 1 km and finer) that SWOT is intended to resolve. We calculate zenith wet tropospheric delays (ZWDs) and their spatial variability from Weather Research and Forecasting (WRF) numerical weather prediction model simulations at 2.33 km spatial resolution over the southwestern U.S., with attention in particular to Sam Rayburn, Ray Hubbard, and Elephant Butte Reservoirs which have width and length dimensions that are of order or larger than the WRF spatial resolution. We find that spatiotemporal variability of ZWD over the inland reservoirs depends on climatic conditions at the reservoir location, as well as distance from ocean, elevation, and surface area of the reservoir, but that the magnitude of subgrid variability (relative to analysis and reanalysis products) is generally less than 10 mm.

  8. Ray-traced tropospheric total slant delays for GNSS processing

    Science.gov (United States)

    Hobiger, T.; Ichikawa, R.; Hatanaka, Y.; Yutsudo, T.; Iwashita, C.; Miyahara, B.; Koyama, Y.; Kondo, T.

    2007-12-01

    Numerical weather models have undergone an improvement of spatial and temporal resolution in the recent years, which made their use for GNSS applications feasible. Ray-tracing through such models permits the computation of total troposphere delays and ray-bending angles. At the National Institute of Information and Communications Technology (NICT), Japan the so-called KAshima RAy-tracing Tools (KARAT) have been developed which allow to obtain troposphere delay corrections in real-time. Together with fine-mesh weather models from the Japanese Meteorological Agency (JMA) huge parts of the East Asian region, including Japan, Korea, Taiwan and East China, can be covered. The Japanese GEONET with its more than 1300 GNSS receivers represent an ideal test-bed for the evaluation of the performance of KARAT. In cooperation with the Geographical Survey Institute (GSI), Japan more than 1.6 billion observations, covering measurements from July 1st until August 31st, 2006, were processed and the corresponding troposphere delays were used to modify the original RINEX files by subtraction of code- and phase delays. These modified observations were processed by a dedicated analysis run of the GEONET operation center, taking advantage of the computer cluster at GSI. First results from this study, together with an in-depth discussion about the assets and drawbacks of the reduction of troposphere total slant delays will be given in this presentation. Additionally an overview about KARAT, the treatment of observational data and the impact of future refined numerical weather models on GNSS analysis will be included in this contribution.

  9. Modeling of GPS tropospheric delay wet Neill mapping function (NMF)

    Science.gov (United States)

    Sakidin, Hamzah; Ahmad, Asmala; Bugis, Ismadi

    2014-10-01

    The modeling of the GPS tropospheric delay mapping function should be revised by modifying or simplify its mathematical model. Some current mapping functions models are separated into hydrostatic and the wet part. The current tropospheric delay models use mapping functions in the form of continued fractions. This model is quite complex and need to be simplified. By using regression method, the wet mapping function models has been selected to be simplified. There are eleven operations for wet mapping function component of Neill Mapping Function (NMF), to be carried out before getting the mapping function scale factor. So, there is a need to simplify the mapping function models to allow faster calculation and also better understanding of the models.

  10. GPS pseudolites: Theory, design, and applications

    Science.gov (United States)

    Cobb, H. Stewart

    Pseudolites (ground-based pseudo-satellite transmitters) can initialize carrier-phase differential GPS (CDGPS) navigation systems in seconds to perform real-time dynamic positioning with one-sigma errors as low as 1 cm. Previous CDGPS systems were rarely used due to cumbersome initialization procedures requiring up to 30 minutes; initialization of the carrier-phase integer ambiguities via pseudolite removes these constraints. This work describes pseudolites optimized for this application which cost two orders of magnitude less than previous pseudolites. Synchrolites (synchronized pseudolites) which derive their timing from individual Global Positioning System (GPS) satellites are also described. Synchrolites can replace the CDGPS reference station and datalink, while simultaneously serving to initialize CDGPS navigation. A cluster of well-placed synchrolites could enable CDGPS navigation even if only one GPS satellite signal is available. A prototype CDGPS system initialized by pseudolites and synchrolites was designed and tested. The goal of this system, known as the Integrity Beacon Landing System (IBLS), was to provide navigation accurate and reliable enough to land aircraft in bad weather. Flight test results for prototype pseudolite and synchrolite systems, including results from 110 fully automatic landings of a Boeing 737 airliner controlled by IBLS, are presented. Existing pseudolite applications are described, including simulation of the GPS constellation for indoor navigation experiments. Synchrolite navigation algorithms are developed and analyzed. New applications for pseudolites and synchrolites are proposed. Theoretical and practical work on the near/far problem is presented.

  11. Evaluation of Empirical Tropospheric Models Using Satellite-Tracking Tropospheric Wet Delays with Water Vapor Radiometer at Tongji, China

    Directory of Open Access Journals (Sweden)

    Miaomiao Wang

    2016-02-01

    Full Text Available An empirical tropospheric delay model, together with a mapping function, is commonly used to correct the tropospheric errors in global navigation satellite system (GNSS processing. As is well-known, the accuracy of tropospheric delay models relies mainly on the correction efficiency for tropospheric wet delays. In this paper, we evaluate the accuracy of three tropospheric delay models, together with five mapping functions in wet delays calculation. The evaluations are conducted by comparing their slant wet delays with those measured by water vapor radiometer based on its satellite-tracking function (collected data with large liquid water path is removed. For all 15 combinations of three tropospheric models and five mapping functions, their accuracies as a function of elevation are statistically analyzed by using nine-day data in two scenarios, with and without meteorological data. The results show that (1 no matter with or without meteorological data, there is no practical difference between mapping functions, i.e., Chao, Ifadis, Vienna Mapping Function 1 (VMF1, Niell Mapping Function (NMF, and MTT Mapping Function (MTT; (2 without meteorological data, the UNB3 is much better than Saastamoinen and Hopfield models, while the Saastamoinen model performed slightly better than the Hopfield model; (3 with meteorological data, the accuracies of all three tropospheric delay models are improved to be comparable, especially for lower elevations. In addition, the kinematic precise point positioning where no parameter is set up for tropospheric delay modification is conducted to further evaluate the performance of tropospheric delay models in positioning accuracy. It is shown that the UNB3 model is best and can achieve about 10 cm accuracy for the N and E coordinate component while 20 cm accuracy for the U coordinate component no matter the meteorological data is available or not. This accuracy can be obtained by the Saastamoinen model only when

  12. Real-Time Tropospheric Delay Estimation using IGS Products

    Science.gov (United States)

    Stürze, Andrea; Liu, Sha; Söhne, Wolfgang

    2014-05-01

    The Federal Agency for Cartography and Geodesy (BKG) routinely provides zenith tropospheric delay (ZTD) parameter for the assimilation in numerical weather models since more than 10 years. Up to now the results flowing into the EUREF Permanent Network (EPN) or E-GVAP (EUMETNET EIG GNSS water vapour programme) analysis are based on batch processing of GPS+GLONASS observations in differential network mode. For the recently started COST Action ES1206 about "Advanced Global Navigation Satellite Systems tropospheric products for monitoring severe weather events and climate" (GNSS4SWEC), however, rapid updates in the analysis of the atmospheric state for nowcasting applications require changing the processing strategy towards real-time. In the RTCM SC104 (Radio Technical Commission for Maritime Services, Special Committee 104) a format combining the advantages of Precise Point Positioning (PPP) and Real-Time Kinematic (RTK) is under development. The so-called State Space Representation approach is defining corrections, which will be transferred in real-time to the user e.g. via NTRIP (Network Transport of RTCM via Internet Protocol). Meanwhile messages for precise orbits, satellite clocks and code biases compatible to the basic PPP mode using IGS products are defined. Consequently, the IGS Real-Time Service (RTS) was launched in 2013 in order to extend the well-known precise orbit and clock products by a real-time component. Further messages e.g. with respect to ionosphere or phase biases are foreseen. Depending on the level of refinement, so different accuracies up to the RTK level shall be reachable. In co-operation of BKG and the Technical University of Darmstadt the real-time software GEMon (GREF EUREF Monitoring) is under development. GEMon is able to process GPS and GLONASS observation and RTS product data streams in PPP mode. Furthermore, several state-of-the-art troposphere models, for example based on numerical weather prediction data, are implemented. Hence, it

  13. Inter-technique validation of tropospheric slant total delays

    Directory of Open Access Journals (Sweden)

    M. Kačmařík

    2017-06-01

    Full Text Available An extensive validation of line-of-sight tropospheric slant total delays (STD from Global Navigation Satellite Systems (GNSS, ray tracing in numerical weather prediction model (NWM fields and microwave water vapour radiometer (WVR is presented. Ten GNSS reference stations, including collocated sites, and almost 2 months of data from 2013, including severe weather events were used for comparison. Seven institutions delivered their STDs based on GNSS observations processed using 5 software programs and 11 strategies enabling to compare rather different solutions and to assess the impact of several aspects of the processing strategy. STDs from NWM ray tracing came from three institutions using three different NWMs and ray-tracing software. Inter-techniques evaluations demonstrated a good mutual agreement of various GNSS STD solutions compared to NWM and WVR STDs. The mean bias among GNSS solutions not considering post-fit residuals in STDs was −0.6 mm for STDs scaled in the zenith direction and the mean standard deviation was 3.7 mm. Standard deviations of comparisons between GNSS and NWM ray-tracing solutions were typically 10 mm ± 2 mm (scaled in the zenith direction, depending on the NWM model and the GNSS station. Comparing GNSS versus WVR STDs reached standard deviations of 12 mm ± 2 mm also scaled in the zenith direction. Impacts of raw GNSS post-fit residuals and cleaned residuals on optimal reconstructing of GNSS STDs were evaluated at inter-technique comparison and for GNSS at collocated sites. The use of raw post-fit residuals is not generally recommended as they might contain strong systematic effects, as demonstrated in the case of station LDB0. Simplified STDs reconstructed only from estimated GNSS tropospheric parameters, i.e. without applying post-fit residuals, performed the best in all the comparisons; however, it obviously missed part of tropospheric signals due to non-linear temporal and spatial variations

  14. Utilization of GPS Tropospheric Delays for Climate Research

    Science.gov (United States)

    Suparta, Wayan

    2017-05-01

    The tropospheric delay is one of the main error sources in Global Positioning Systems (GPS) and its impact plays a crucial role in near real-time weather forecasting. Accessibility and accurate estimation of this parameter are essential for weather and climate research. Advances in GPS application has allowed the measurements of zenith tropospheric delay (ZTD) in all weather conditions and on a global scale with fine temporal and spatial resolution. In addition to the rapid advancement of GPS technology and informatics and the development of research in the field of Earth and Planetary Sciences, the GPS data has been available free of charge. Now only required sophisticated processing techniques but user friendly. On the other hand, the ZTD parameter obtained from the models or measurements needs to be converted into precipitable water vapor (PWV) to make it more useful as a component of weather forecasting and analysis atmospheric hazards such as tropical storms, flash floods, landslide, pollution, and earthquake as well as for climate change studies. This paper addresses the determination of ZTD as a signal error or delay source during the propagation from the satellite to a receiver on the ground and is a key driving force behind the atmospheric events. Some results in terms of ZTD and PWV will be highlighted in this paper.

  15. Troposphere delay modeling using ray-traced delays around Tsukuba during a 14-days typhoon period in September 2007

    Science.gov (United States)

    Pany, A.; Boehm, J.; Hobiger, T.; Schuh, H.

    2009-04-01

    Accurate modeling of the tropospheric delay of microwave signals is of great importance for space geodetic techniques, such as Very Long Baseline Interferometry (VLBI) and the Global Navigation Satellite Systems (GNSS). In state-of-the-art VLBI analysis tropospheric zenith delays are estimated using mapping functions, and gradients are applied in order to account for azimuthal asymmetries. Monte Carlo simulations carried out within the International VLBI Service for Geodesy and Astrometry (IVS) to design the next generation VLBI system, VLBI2010, have clearly shown that the tropospheric delay is the limiting factor in VLBI analysis and that a simple gradient model, as currently applied, might be insufficient for VLBI2010 which will provide a much higher observation density. The Japan Meteorological Agency (JMA) provides high resolution numerical weather models. With KARAT, the Kashima Ray-Tracing Tools, we computed tropospheric slant delays around the VLBI site in Tsukuba for a 14-days typhoon period in September 2007. The resolution of these ray-traced delays is 1° in both azimuth and elevation, and three hours in time. The delays exhibit significant azimuthally asymmetric characteristics. We fit spherical harmonic functions of different degrees and orders to the ray-traced delays in order to test their ability of modeling the spatial structures of the troposphere, and we investigate whether further continuation of the continued fraction form, i.e. estimating more coefficients, might improve troposphere modeling.

  16. Impact of the initial tropospheric zenith path delay on precise point positioning convergence during active conditions

    Science.gov (United States)

    Kalita, J. Z.; Rzepecka, Z.

    2017-04-01

    Tropospheric delay is one of the key factors that influence the convergence time of the precise point positioning (PPP) method. Current models do not allow for the fixing of the zenith path delay tropospheric parameter, leaving the difference between nominal and final value to the estimation process. Here, we present an analysis of several PPP result-sets using the tropospheric parameter’s nominal value adopted from models: VMF1, GPT2w, MOPS, and ZERO-WET. The last variant assumes a zero value for the initial wet part of the zenith delay. The PPP results are subtracted from a solution based on the final tropospheric product from the International GNSS Service (IGS). Several days exhibiting the most active tropospheric conditions were selected for each of the 7 stations located in the mid-latitude Central European region. During the active days, application of the VMF1 model increases the resulting height component’s quality by about 33-36% when compared to the GPT2w and MOPS. The respective improvement in VMF1 latitude and longitude components is 27% and 15%. The average relative deterioration in the result standard deviations between active and calm tropospheric conditions reaches about 20-30% of the former. We discuss the impact of the initial tropospheric parameter’s variance and bias on positioning. In addition, we compare the results with those of other studies over the impact of active tropospheric conditions on the PPP method.

  17. Application of ray-traced tropospheric slant delays to geodetic VLBI analysis

    Science.gov (United States)

    Hofmeister, Armin; Böhm, Johannes

    2017-08-01

    The correction of tropospheric influences via so-called path delays is critical for the analysis of observations from space geodetic techniques like the very long baseline interferometry (VLBI). In standard VLBI analysis, the a priori slant path delays are determined using the concept of zenith delays, mapping functions and gradients. The a priori use of ray-traced delays, i.e., tropospheric slant path delays determined with the technique of ray-tracing through the meteorological data of numerical weather models (NWM), serves as an alternative way of correcting the influences of the troposphere on the VLBI observations within the analysis. In the presented research, the application of ray-traced delays to the VLBI analysis of sessions in a time span of 16.5 years is investigated. Ray-traced delays have been determined with program RADIATE (see Hofmeister in Ph.D. thesis, Department of Geodesy and Geophysics, Faculty of Mathematics and Geoinformation, Technische Universität Wien. http://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-3444, 2016) utilizing meteorological data provided by NWM of the European Centre for Medium-Range Weather Forecasts (ECMWF). In comparison with a standard VLBI analysis, which includes the tropospheric gradient estimation, the application of the ray-traced delays to an analysis, which uses the same parameterization except for the a priori slant path delay handling and the used wet mapping factors for the zenith wet delay (ZWD) estimation, improves the baseline length repeatability (BLR) at 55.9% of the baselines at sub-mm level. If no tropospheric gradients are estimated within the compared analyses, 90.6% of all baselines benefit from the application of the ray-traced delays, which leads to an average improvement of the BLR of 1 mm. The effects of the ray-traced delays on the terrestrial reference frame are also investigated. A separate assessment of the RADIATE ray-traced delays is carried out by comparison to the ray-traced delays from the

  18. A Robust and Multi-Weighted Approach to Estimating Topographically Correlated Tropospheric Delays in Radar Interferograms

    Directory of Open Access Journals (Sweden)

    Bangyan Zhu

    2016-07-01

    Full Text Available Spatial and temporal variations in the vertical stratification of the troposphere introduce significant propagation delays in interferometric synthetic aperture radar (InSAR observations. Observations of small amplitude surface deformations and regional subsidence rates are plagued by tropospheric delays, and strongly correlated with topographic height variations. Phase-based tropospheric correction techniques assuming a linear relationship between interferometric phase and topography have been exploited and developed, with mixed success. Producing robust estimates of tropospheric phase delay however plays a critical role in increasing the accuracy of InSAR measurements. Meanwhile, few phase-based correction methods account for the spatially variable tropospheric delay over lager study regions. Here, we present a robust and multi-weighted approach to estimate the correlation between phase and topography that is relatively insensitive to confounding processes such as regional subsidence over larger regions as well as under varying tropospheric conditions. An expanded form of robust least squares is introduced to estimate the spatially variable correlation between phase and topography by splitting the interferograms into multiple blocks. Within each block, correlation is robustly estimated from the band-filtered phase and topography. Phase-elevation ratios are multiply- weighted and extrapolated to each persistent scatter (PS pixel. We applied the proposed method to Envisat ASAR images over the Southern California area, USA, and found that our method mitigated the atmospheric noise better than the conventional phase-based method. The corrected ground surface deformation agreed better with those measured from GPS.

  19. A tunable closed form model for the structure function of tropospheric delay

    DEFF Research Database (Denmark)

    Merryman Boncori, John Peter; Mohr, Johan Jacob

    2008-01-01

    -specific information, describing the atmospheric state. In this letter, a closed-form expression for the zenith delay structure function of tropospheric propagation delay is derived from a two-regime power spectral density function reported in the literature. The power at a specific spatial frequency is used as a free...

  20. Determining the Tropospheric Delay of a Radio Signal by the Radiometric Method

    Science.gov (United States)

    Ilyin, G. N.; Troitsky, A. V.

    2017-10-01

    We present a method and algorithm for real-time determination of the tropospheric delay of a radio signal and the radiometric complex developed on their basis. The method is based on the measurement of the atmospheric thermal microwave radiation intensity at the frequencies ν 1 = 20.7 GHz, ν 2 = 32 GHz, and ν 3 = 56.7 GHz and solution of the corresponding inverse problem with respect to the atmospheric parameters (temperature, pressure, humidity, and water content) which completely determine the tropospheric delay of a radio signal. The method was experimentally tested by comparing the radio-signal delay series obtained by the radiometric method and the GLONASS/GPS data. The error of determining the wet component of the radio-signal delay was about 3 mm.

  1. Statistical description of tropospheric delay for InSAR : Overview and a new model

    DEFF Research Database (Denmark)

    Merryman Boncori, John Peter; Mohr, Johan Jacob

    2007-01-01

    of zenith tropospheric propagation delay is then derived from a two-regime power spectral density function presented in literature. The novelty lies in the fact that a closed form expression is derived and a free model parameter is allowed, which may be tuned to available measurements or, in the absence...

  2. Tropospheric delay modelling and the celestial reference frame at radio wavelengths

    Science.gov (United States)

    Mayer, D.; Böhm, J.; Krásná, H.; Landskron, D.

    2017-10-01

    Aims: We examine the relationship between Very Long Baseline Interferometry (VLBI) tropospheric delay modelling and source positions. In particular, the effect of a priori ray-traced slant delays on source declination is investigated. Methods: We estimated source coordinates as global positions from 5830 geodetic VLBI sessions incorporating about 10 million group delay measurements. This data set was used for the International Celestial Reference Frame 3 (ICRF3) prototype solutions as of December 2016. Results: We report on a significant bias in source declination of about 50 μas, which can be found between a normal solution and a solution where a priori ray-traced slant delays are used. More traditional tropospheric delay modelling techniques, such as a priori gradients, are tested as well. Significant differences of about 30 μas in declination can only be found when absolute constraints are used for a priori gradient models. Further, we find that none of these models decrease the declination bias between ICRF3 prototype solutions and ICRF2.

  3. Electromagnetic compatibility of ground system of near navigation, based on the use of GNSS and pseudolites

    Science.gov (United States)

    Kartsan, I. N.; Dmitriev, D. D.; Sokolovskii, A. V.; Ratushnyak, V. N.; Gladyshev, A. B.; Kovalev, I. V.

    2017-10-01

    Article describes the results of modeling the allowable power pseudolites in the ground system of near navigation, working together with GLONASS. Was justified pulsed operation of pseudolites and using weighting windows to improve electromagnetic compatibility of pseudolites signals with GNSS signals.

  4. Impacts of ionospheric electric fields on the GPS tropospheric delays during geomagnetic storms in Antarctica

    Science.gov (United States)

    Suparta, W.

    2017-05-01

    This paper aimed to overview the interaction of the thunderstorm with the ionospheric electric fields during major geomagnetic storms in Antarctica through the GPS tropospheric delays. For the purpose of study, geomagnetic activity and electric fields data for the period from 13 to 21 March 2015 representing the St. Patrick’s Day storm is analyzed. To strengthen the analysis, data for the period of 27 October to 1st November 2003 representing for the Halloween storm is also compared. Our analysis showed that both geomagnetic storms were severe (Ap ≥ 100 nT), where the intensity of Halloween storm is double compared to St. Patrick’s Day storm. For the ionospheric electric field, the peaks were dropped to -1.63 mV/m and -2.564 mV/m for St. Patrick and Halloween storms, respectively. At this time, the interplanetary magnetic field Bz component was significantly dropped to -17.31 nT with Ap > 150 nT (17 March 2015 at 19:20 UT) and -26.51 nT with Ap = 300 nT (29 October 2003 at 19:40 UT). For both geomagnetic storms, the electric field was correlated well with the ionospheric activity where tropospheric delays show a different characteristic.

  5. Estimating Zenith Tropospheric Delays from BeiDou Navigation Satellite System Observations

    Directory of Open Access Journals (Sweden)

    Xin Sui

    2013-04-01

    Full Text Available The GNSS derived Zenith Tropospheric Delay (ZTD plays today a very critical role in meteorological study and weather forecasts, as ZTDs of thousands of GNSS stations are operationally assimilated into numerical weather prediction models. Recently, the Chinese BeiDou Navigation Satellite System (BDS was officially announced to provide operational services around China and its neighborhood and it was demonstrated to be very promising for precise navigation and positioning. In this contribution, we concentrate on estimating ZTD using BDS observations to assess its capacity for troposphere remote sensing. A local network which is about 250 km from Beijing and comprised of six stations equipped with GPS- and BDS-capable receivers is utilized. Data from 5 to 8 November 2012 collected on the network is processed in network mode using precise orbits and in Precise Point Positioning mode using precise orbits and clocks. The precise orbits and clocks are generated from a tracking network with most of the stations in China and several stations around the world. The derived ZTDs are compared with that estimated from GPS data using the final products of the International GNSS Service (IGS. The comparison shows that the bias and the standard deviation of the ZTD differences are about 2 mm and 5 mm, respectively, which are very close to the differences of GPS ZTD estimated using different software packages.

  6. Precise troposphere delay model for Egypt, as derived from radiosonde data

    Directory of Open Access Journals (Sweden)

    M.A. Abdelfatah

    2015-06-01

    Real GPS data of six stations in 8-day period were used for the assessment of zenith part of PTD model against the available international models. These international models include Saastamoinen, Hopfield, and the local Egyptian dry model proposed by Mousa & El-Fiky. The data were processed using Bernese software version 5.0. The closure error results indicate that the PTD model is the best model in all session, but when the available radiosonde stations are less, the accuracy of PTD model is near to classic models. As radiosonde data for all ten stations are not available every session, it is recommended to use one of the regularization techniques for database to overcome missing data and derive consistent tropospheric delay information.

  7. Airborne Pseudolites in a Global Positioning System (GPS) Degraded Environment

    Science.gov (United States)

    2011-03-01

    of the ION GPS 2000 Meeting. School of Geomatic Engineering University of New South Wales, Sydney, NSW 2052, Australia, September 2000. 95 12...56, July 2002. 35. Wang, Jinling and Hung-Kyu Lee. “Impact of Pseudolite Location Errors in Positioning”. Geomatics Research Australasia, 81–94

  8. Troposphere delays from ground-based GNSS-R - self-calibration and new possibilites for atmosphere research

    Science.gov (United States)

    Hobiger, Thomas; Strandberg, Joakim; Haas, Rüdiger

    2017-04-01

    Ground-based GNSS reflectometry (GNSS-R) has been proven to be a useful tool for a variety of geophysical applications. In particular, the fact that in most cases existing GNSS sites can be used for reflectometry purposes makes this concept very appealing. Successful ground-based GNSS-R applications include sea-level monitoring, soil moisture , snow or vegetation. By a recent approach by Strandberg et al. (2016) it was demonstrated that it is feasible to carry out rigorous inverse modeling of signal to noise ratio (SNR) data in order to improve the retrieved parameters concerning accuracy and precision. Based on the concept of inverse modelling, as we discuss in this paper, it can be shown that it is possible to account for troposphere delays by means of self-calibration which means that target parameters will not be biased by unmodeled atmosphere excess path delays. This implies that also troposphere delay information can be deduced from the SNR pattern that is related to multi-path interference. Thus, we can access troposphere information related to domains which are below the antenna and laterally offset and thus are not sensed with classical GNSS applications. In order to motivate this new concept, we will discuss the idea of troposphere self-calibration in GNSS-R processing and demonstrate the effectiveness of this approach concerning accuracy and precision of the target parameters. It will be shown how troposphere contributions need to be considered in inverse modeling and a thorough interpretation of the obtained troposphere parameters will be given. We will also provide an outlook concerning the question how and to which extent ground-based GNSS-R observations could contribute to atmosphere research and which novel applications could emerge.

  9. Modeling tropospheric wet delays with national GNSS reference network in China for BeiDou precise point positioning

    Science.gov (United States)

    Zheng, Fu; Lou, Yidong; Gu, Shengfeng; Gong, Xiaopeng; Shi, Chuang

    2017-10-01

    During past decades, precise point positioning (PPP) has been proven to be a well-known positioning technique for centimeter or decimeter level accuracy. However, it needs long convergence time to get high-accuracy positioning, which limits the prospects of PPP, especially in real-time applications. It is expected that the PPP convergence time can be reduced by introducing high-quality external information, such as ionospheric or tropospheric corrections. In this study, several methods for tropospheric wet delays modeling over wide areas are investigated. A new, improved model is developed, applicable in real-time applications in China. Based on the GPT2w model, a modified parameter of zenith wet delay exponential decay wrt. height is introduced in the modeling of the real-time tropospheric delay. The accuracy of this tropospheric model and GPT2w model in different seasons is evaluated with cross-validation, the root mean square of the zenith troposphere delay (ZTD) is 1.2 and 3.6 cm on average, respectively. On the other hand, this new model proves to be better than the tropospheric modeling based on water-vapor scale height; it can accurately express tropospheric delays up to 10 km altitude, which potentially has benefits in many real-time applications. With the high-accuracy ZTD model, the augmented PPP convergence performance for BeiDou navigation satellite system (BDS) and GPS is evaluated. It shows that the contribution of the high-quality ZTD model on PPP convergence performance has relation with the constellation geometry. As BDS constellation geometry is poorer than GPS, the improvement for BDS PPP is more significant than that for GPS PPP. Compared with standard real-time PPP, the convergence time is reduced by 2-7 and 20-50% for the augmented BDS PPP, while GPS PPP only improves about 6 and 18% (on average), in horizontal and vertical directions, respectively. When GPS and BDS are combined, the geometry is greatly improved, which is good enough to get a

  10. An inter-comparison of zenith tropospheric delays derived from DORIS and GPS data

    Science.gov (United States)

    Bock, Olivier; Willis, Pascal; Lacarra, Maïté; Bosser, Pierre

    2010-12-01

    Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) and Global Positioning System (GPS) techniques are similarly affected by propagation delays in the neutral atmosphere (troposphere) and hence make use of similar data processing strategies for reducing this effect. We compare Zenith Tropospheric Delays (ZTDs) estimated from 52 DORIS and GPS station pairs co-located at 35 sites over the 2005-2008 period. We find an overall systematic negative mean bias of -4 mm and a median bias of -2 mm, with a large site-to-site scatter and especially stronger biases over South America, potentially linked to remaining problems related to the South Atlantic Anomaly (SAA) in the current DORIS data processing. The standard deviation of ZTD differences is in the range 4-12 mm over the globe (8 mm on average), with larger values located in the southern hemisphere. The spatial variability of differences is consistent with previous work but remains largely unexplained. DORIS is shown to be much less sensitive to instrumental changes than GPS (only the switch from Alcatel to Starec antenna at Toulouse is detected as an offset of -4 mm in the ZTD time series). On the opposite, discontinuities and spurious annual signals are found in the GPS ZTD solutions. A discontinuity of +5 mm is found on 5 November 2006, linked to the switch from relative to absolute GPS antenna models used in the data processing. The use of modified GPS antennas (e.g. at GODE) or improved antenna models is shown to reduce the spurious annual signal (e.g. from 5 mm to 2 mm at METS). Overall, the agreement between both techniques is good, though DORIS shows a significantly larger random scatter. The high stability and good spatial and temporal coverage make DORIS a potential candidate technique for meteorology and climate studies as long as reasonable time averaging can be applied (e.g. differences are reduced from 8.6 to 2.4 mm with 5-day averages) and no real-time application is considered. This

  11. Analysing the Zenith Tropospheric Delay Estimates in On-line Precise Point Positioning (PPP) Services and PPP Software Packages.

    Science.gov (United States)

    Mendez Astudillo, Jorge; Lau, Lawrence; Tang, Yu-Ting; Moore, Terry

    2018-02-14

    As Global Navigation Satellite System (GNSS) signals travel through the troposphere, a tropospheric delay occurs due to a change in the refractive index of the medium. The Precise Point Positioning (PPP) technique can achieve centimeter/millimeter positioning accuracy with only one GNSS receiver. The Zenith Tropospheric Delay (ZTD) is estimated alongside with the position unknowns in PPP. Estimated ZTD can be very useful for meteorological applications, an example is the estimation of water vapor content in the atmosphere from the estimated ZTD. PPP is implemented with different algorithms and models in online services and software packages. In this study, a performance assessment with analysis of ZTD estimates from three PPP online services and three software packages is presented. The main contribution of this paper is to show the accuracy of ZTD estimation achievable in PPP. The analysis also provides the GNSS users and researchers the insight of the processing algorithm dependence and impact on PPP ZTD estimation. Observation data of eight whole days from a total of nine International GNSS Service (IGS) tracking stations spread in the northern hemisphere, the equatorial region and the southern hemisphere is used in this analysis. The PPP ZTD estimates are compared with the ZTD obtained from the IGS tropospheric product of the same days. The estimates of two of the three online PPP services show good agreement (southern hemisphere stations. The results also show that the online PPP services perform better than the selected PPP software packages at all stations.

  12. The Positioning Performance Analysis of BeiDou/Pseudolites Collaboration by CNMC Method

    Directory of Open Access Journals (Sweden)

    FU Jingyang

    2017-05-01

    Full Text Available At present, the number of orbit satellites is limited for the Beidou satellite navigation system. In special terrain like “city Canyon” and other special circumstances, the signal of Beidou is easy to be blocked, which reduces positioning accuracy or interrupts positioning continuity of users. Joining pseudolites can effectively solve the problem of the insufficient number of BeiDou satellites visible to users. During cooperative positioning of Beidou satellites and pseudolites, the multi-path problem in pseudo-range observation values of the BeiDou satellite and the pseudolite shall be properly handled to obtain better positioning accuracy. The CNMC method (Code Noise and Multi-path Correction can effectively reduce the multi-path effect of the BeiDou satellite's pseudo-range observation value, but cannot be applied directly to pseudo-range data processing of the pseudolite due to different observation error characteristics caused by different signal propagation paths. To solve the multi-path processing problem of pseudolites, the CNMC method is improved in this paper. The BeiDou/Pseudolite dynamic cooperative positioning experiments were conducted in the actual field of pseudolites. The test results show that the three-dimensional positioning accuracy is increased from 2.326 m to 1.936 m with enhanced positioning stability after pseudo-range observation values of the BeiDou satellite and the ground pseudolite are processed by the CNMC method.

  13. Global positioning system pseudolite-based relative navigation.

    Energy Technology Data Exchange (ETDEWEB)

    Monda, Eric W. (University of Texas, Austin, TX)

    2004-03-01

    Though the Global Positioning System has revolutionized navigation in the modern age, it is limited in its capability for some applications because an unobstructed line of sight to a minimum of four satellites is required. One way of augmenting the system in small areas is by employing pseudolites to broadcast additional signals that can be used to improve the user's position solution. At the Navigation Systems Testing Laboratory (NSTL) at NASA's Johnson Space Center in Houston, TX, research has been underway on the use of pseudolites to perform precision relative navigation. Based on the findings of previous research done at the NSTL, the method used to process the pseudolite measurements is an extended Kalman filter of the double differenced carrier phase measurements. By employing simulations of the system, as well as processing previously collected data in a real time manner, sub-meter tracking of a moving receiver with carrier phase measurements in the extended Kalman filter appears to be possible.

  14. Precise Point Positioning (PPP) - an alternative processing technique to estimate the tropospheric wet delay of GNSS signals

    Science.gov (United States)

    Karabatic, A.; Weber, R.

    2009-04-01

    Microwave signals of the GNSS satellites (GPS, GLONASS and in future GALILEO) are time delayed when passing the atmosphere. Based on this signal delay, e.g. the humidity distribution within the troposphere can be determined. It has already been shown that delivery of the Zenith Wet Delays derived from a network solution with hourly resolution and accuracy of 1mm PW is achievable. In the case of very large networks along with an increased number of observation and computational demands, an alternative processing technique has to be applied - Precise Point Positioning (PPP). In this presentation we investigate how the atmospheric precipitable water content derived from GNSS data can be assimilated within an operational Nowcasting system (INCA) and how PPP results compare to the network solution. It is to be expected that the accuracy of the PPP estimates decreases due to several effects (satellite clocks, biases, no ambiguity resolution), but independency from the reference station data will significantly shorten the latency of the results (few min), and provide the regional/national service to enhance the prognosis in the numerical forecast model. It has been proved that e.g. passing weather fronts can be analysed much better by introduced GNSS derived tropospheric wet delays because this data is influenced by changes in humidity in the free atmosphere, whereas the data at the meteorological ground stations reacts to these changes with a considerable time delay. This allows to forecast heavy rainfall causing potentially local floodings more reliable and to narrow down the affected region.

  15. Predictions of Tropospheric Zenithal Delay for South America : Seasonal Variability and Quality Evaluation

    Directory of Open Access Journals (Sweden)

    Luiz Augusto Toledo Machado

    2006-12-01

    Full Text Available The Zenithal Tropospheric Delay (Z TD is an important error source in the observable involved in the positioning methods using artificial satellite. Frequently, the Z TD influence in the positioning is minimized by applying empirical models. However, such models are not able to supply the precision required to some real time applications, such as navigation and steak out. In 2010 it will be implanted the new navigation and administration system of the air traffic, denominated CNS-ATM (Communication Navigation Surveillance - Air Traffic Management. In this new system the application of positioning techniques by satellites in the air traffic will be quite explored because they provide good precision in real time. The predictions of Z TD values from Numeric Weather Prediction (NWP, denominated dynamic modeling, is an alternative to model the atmospheric gases effects in the radio-frequency signals in real time. The Center for Weather Forecasting and Climate Studies (CPTEC has generated operationally prediction of Z TD values to South American Continent since March, 2004. The aims of the present paper are to investigate the Z TD seasonal variability and evaluate the quality of predicted Z TD values. One year of GPS data from Brazilian Continuous GPS Network (RBMC was used in this evaluation. The RMS values resulting from this evaluation were in the range of 4 to 11 cm. Considering the Z TDtemporal variability, the advantages provide by this modeling, the results obtained in this evaluation and the future improvements, this work shows that the dynamic modeling has great potential to become the most appropriate alternative to model Z TD in real time.

  16. What is the impact of different VLBI analysis setups of the tropospheric delay on precipitable water vapor trends?

    Science.gov (United States)

    Balidakis, Kyriakos; Nilsson, Tobias; Heinkelmann, Robert; Glaser, Susanne; Zus, Florian; Deng, Zhiguo; Schuh, Harald

    2017-04-01

    The quality of the parameters estimated by global navigation satellite systems (GNSS) and very long baseline interferometry (VLBI) are distorted by erroneous meteorological observations applied to model the propagation delay in the electrically neutral atmosphere. For early VLBI sessions with poor geometry, unsuitable constraints imposed on the a priori tropospheric gradients is a source of additional hassle of VLBI analysis. Therefore, climate change indicators deduced from the geodetic analysis, such as the long-term precipitable water vapor (PWV) trends, are strongly affected. In this contribution we investigate the impact of different modeling and parameterization of the propagation delay in the troposphere on the estimates of long-term PWV trends from geodetic VLBI analysis results. We address the influence of the meteorological data source, and of the a priori non-hydrostatic delays and gradients employed in the VLBI processing, on the estimated PWV trends. In particular, we assess the effect of employing temperature and pressure from (i) homogenized in situ observations, (ii) the model levels of the ERA Interim reanalysis numerical weather model and (iii) our own blind model in the style of GPT2w with enhanced parameterization, calculated using the latter data set. Furthermore, we utilize non-hydrostatic delays and gradients estimated from (i) a GNSS reprocessing at GeoForschungsZentrum Potsdam, rigorously considering tropospheric ties, and (ii)) direct ray-tracing through ERA Interim, as additional observations. To evaluate the above, the least-squares module of the VieVS@GFZ VLBI software was appropriately modified. Additionally, we study the noise characteristics of the non-hydrostatic delays and gradients estimated from our VLBI and GNSS analyses as well as from ray-tracing. We have modified the Theil-Sen estimator appropriately to robustly deduce PWV trends from VLBI, GNSS, ray-tracing and direct numerical integration in ERA Interim. We disseminate all

  17. Analysing the Zenith Tropospheric Delay Estimates in On-line Precise Point Positioning (PPP Services and PPP Software Packages

    Directory of Open Access Journals (Sweden)

    Jorge Mendez Astudillo

    2018-02-01

    Full Text Available As Global Navigation Satellite System (GNSS signals travel through the troposphere, a tropospheric delay occurs due to a change in the refractive index of the medium. The Precise Point Positioning (PPP technique can achieve centimeter/millimeter positioning accuracy with only one GNSS receiver. The Zenith Tropospheric Delay (ZTD is estimated alongside with the position unknowns in PPP. Estimated ZTD can be very useful for meteorological applications, an example is the estimation of water vapor content in the atmosphere from the estimated ZTD. PPP is implemented with different algorithms and models in online services and software packages. In this study, a performance assessment with analysis of ZTD estimates from three PPP online services and three software packages is presented. The main contribution of this paper is to show the accuracy of ZTD estimation achievable in PPP. The analysis also provides the GNSS users and researchers the insight of the processing algorithm dependence and impact on PPP ZTD estimation. Observation data of eight whole days from a total of nine International GNSS Service (IGS tracking stations spread in the northern hemisphere, the equatorial region and the southern hemisphere is used in this analysis. The PPP ZTD estimates are compared with the ZTD obtained from the IGS tropospheric product of the same days. The estimates of two of the three online PPP services show good agreement (<1 cm with the IGS ZTD values at the northern and southern hemisphere stations. The results also show that the online PPP services perform better than the selected PPP software packages at all stations.

  18. Estimation of the Tropospheric Wet Delay of Radio waves Based on a Model and Microwave Radiometry Data

    Science.gov (United States)

    Gotyur, I. A.; Karavaev, D. M.; Krasnov, V. M.; Kuleshov, Y. V.; Lebedev, A. B.; Meshkov, A. N.; Shchukin, G. G.

    2017-08-01

    By combining the global atmospheric model NRLMSISE-00 and the humidity model of the Northern hemisphere (GOST 26352-84), we developed a model for calculation of the dielectric permittivity of the atmosphere along the radio-wave propagation path. Microwave radiometry data were used to test the model. The difference between the model and measured values of the zenith wet delay of radio waves in the troposphere averaged 1-3 cm for a r.m.s. deviation of 4.7-5.3 cm.

  19. Atmospheric oscillations comparison on long term tropospheric delay time series derived from ray-tracing and GPS

    Science.gov (United States)

    Nikolaidou, Thalia; Santos, Marcelo

    2017-04-01

    The caused time delay induced by the atmosphere on the GNSS signals (NAD), depends primarily on the amount of atmosphere the signal traverses till it reaches to the Earth's surface and can exceed t 20 m for low elevation angles (around 3 degrees). For a particular ray i.e. satellite/quasar-antenna link, the delay depends on the atmospheric parameters of total pressure, temperature, and the partial pressure of water vapor. Because of that, numerical weather models (NWM) have already proven beneficial for atmospheric modelling and geodesy. By direct raytracing, inside NWM, the VMF1 and the University of New Brunswick VMF1 (UNB-VMF1) (Urquhart et al. 2011), access the 3D variation of the meteorological parameters that determine the delay thus being the state-the-art mapping functions used today. The raytracing procedure is capable of providing NADs delays for any point on the Earth's surface. In this study we study the impact of regional numerical weather models, with high spatial and temporal resolution, namely 25km and 6h. These models outweigh the currently used NWM by having about 2.6 times better spatial resolution. Raytracing through such NWM, using the independent raytracing algorithm develop at UNB (Nievinski, 2009), we acquire superior quality NADs with regional application. We ray-trace for the International GNSS service (IGS) network stations for a time span of 11 years. Benchmarking against the IGS troposphere product is performed to access the accuracy of our results. A periodicity analysis is conducted to examine the signature of atmospheric oscillations on the NAD time series. In order to recognize the NAD periodicities, we compared our product against the GPS-derived IGS troposphere product. Systematic effects within each single technique are identified and long-term NAD stability is accessed.

  20. A New Method for Single-Epoch Ambiguity Resolution with Indoor Pseudolite Positioning.

    Science.gov (United States)

    Li, Xin; Zhang, Peng; Guo, Jiming; Wang, Jinling; Qiu, Weining

    2017-04-21

    Ambiguity resolution (AR) is crucial for high-precision indoor pseudolite positioning. Due to the existing characteristics of the pseudolite positioning system, such as the geometry structure of the stationary pseudolite which is consistently invariant, the indoor signal is easy to interrupt and the first order linear truncation error cannot be ignored, and a new AR method based on the idea of the ambiguity function method (AFM) is proposed in this paper. The proposed method is a single-epoch and nonlinear method that is especially well-suited for indoor pseudolite positioning. Considering the very low computational efficiency of conventional AFM, we adopt an improved particle swarm optimization (IPSO) algorithm to search for the best solution in the coordinate domain, and variances of a least squares adjustment is conducted to ensure the reliability of the solving ambiguity. Several experiments, including static and kinematic tests, are conducted to verify the validity of the proposed AR method. Numerical results show that the IPSO significantly improved the computational efficiency of AFM and has a more elaborate search ability compared to the conventional grid searching method. For the indoor pseudolite system, which had an initial approximate coordinate precision better than 0.2 m, the AFM exhibited good performances in both static and kinematic tests. With the corrected ambiguity gained from our proposed method, indoor pseudolite positioning can achieve centimeter-level precision using a low-cost single-frequency software receiver.

  1. A hardware-software complex for modelling and research of near navigation based on pseudolites

    Science.gov (United States)

    Gladyshev, A. B.; Dmitriev, D. D.; Veysov, E. A.; Tyapkin, V. N.

    2017-01-01

    The paper considers a hardware-software complex for research of characteristics of accuracy and noise immunity of a near navigation system based on pseudolites. The complex is implemented on the basis of the “National Instruments” hardware platform and “LabView” coding environment. It provides a simulated navigation field, the analysis of the received signals, the determination of the errors of measurement of navigation parameters for pseudolites signals, comparing the measured error with the characteristics of a standard GNSS receiver.

  2. Hyperbolic Positioning with Antenna Arrays and Multi-Channel Pseudolite for Indoor Localization.

    Science.gov (United States)

    Fujii, Kenjirou; Sakamoto, Yoshihiro; Wang, Wei; Arie, Hiroaki; Schmitz, Alexander; Sugano, Shigeki

    2015-09-30

    A hyperbolic positioning method with antenna arrays consisting of proximately-located antennas and a multi-channel pseudolite is proposed in order to overcome the problems of indoor positioning with conventional pseudolites (ground-based GPS transmitters). A two-dimensional positioning experiment using actual devices is conducted. The experimental result shows that the positioning accuracy varies centimeter- to meter-level according to the geometric relation between the pseudolite antennas and the receiver. It also shows that the bias error of the carrier-phase difference observables is more serious than their random error. Based on the size of the bias error of carrier-phase difference that is inverse-calculated from the experimental result, three-dimensional positioning performance is evaluated by computer simulation. In addition, in the three-dimensional positioning scenario, an initial value convergence analysis of the non-linear least squares is conducted. Its result shows that initial values that can converge to a right position exist at least under the proposed antenna setup. The simulated values and evaluation methods introduced in this work can be applied to various antenna setups; therefore, by using them, positioning performance can be predicted in advance of installing an actual system.

  3. Hyperbolic Positioning with Antenna Arrays and Multi-Channel Pseudolite for Indoor Localization

    Directory of Open Access Journals (Sweden)

    Kenjirou Fujii

    2015-09-01

    Full Text Available A hyperbolic positioning method with antenna arrays consisting of proximately-located antennas and a multi-channel pseudolite is proposed in order to overcome the problems of indoor positioning with conventional pseudolites (ground-based GPS transmitters. A two-dimensional positioning experiment using actual devices is conducted. The experimental result shows that the positioning accuracy varies centimeter- to meter-level according to the geometric relation between the pseudolite antennas and the receiver. It also shows that the bias error of the carrier-phase difference observables is more serious than their random error. Based on the size of the bias error of carrier-phase difference that is inverse-calculated from the experimental result, three-dimensional positioning performance is evaluated by computer simulation. In addition, in the three-dimensional positioning scenario, an initial value convergence analysis of the non-linear least squares is conducted. Its result shows that initial values that can converge to a right position exist at least under the proposed antenna setup. The simulated values and evaluation methods introduced in this work can be applied to various antenna setups; therefore, by using them, positioning performance can be predicted in advance of installing an actual system.

  4. CDDIS_GNSS_products_troposphere

    Data.gov (United States)

    National Aeronautics and Space Administration — Troposphere Zenith Path Delay (ZPD) values by site derived from analysis of Global Navigation Satellite System (GNSS) data. These products are the generated by...

  5. Ozone, Tropospheric

    Science.gov (United States)

    Fishman, Jack

    1995-01-01

    In the early part of the 20th century, ground-based and balloon-borne measurements discovered that most of atmosphere's ozone is located in the stratosphere with highest concentrations located between 15 and 30 km (9,3 and 18.6 miles). For a long time, it was believed that tropospheric ozone originated from the stratosphere and that most of it was destroyed by contact with the earth's surface. Ozone, O3, was known to be produced by the photo-dissociation of molecular oxygen, O2, a process that can only occur at wavelengths shorter than 242 nm. Because such short-wave-length radiation is present only in the stratosphere, no tropospheric ozone production is possible by this mechanism. In the 1940s, however, it became obvious that production of ozone was also taking place in the troposphere. The overall reaction mechanism was eventually identified by Arie Haagen-Smit of the California Institute of Technology, in highly polluted southern California. The copious emissions from the numerous cars driven there as a result of the mass migration to Los Angeles after World War 2 created the new unpleasant phenomenon of photochemical smog, the primary component of which is ozone. These high levels of ozone were injuring vegetable crops, causing women's nylons to run, and generating increasing respiratory and eye-irritation problems for the populace. Our knowledge of tropospheric ozone increased dramatically in the early 1950s as monitoring stations and search centers were established throughout southern California to see what could be done to combat this threat to human health and the environment.

  6. A Method to Reduce Non-Nominal Troposphere Error

    OpenAIRE

    Wang, Zhipeng; Xin, Pumin; Li, Rui; Wang, Shujing

    2017-01-01

    Under abnormal troposphere, Ground-Based Augmentation System (GBAS) is unable to eliminate troposphere delay, resulting in non-nominal troposphere error. This paper analyzes the troposphere meteorological data of eight International GNSS Monitoring Assessment System (iGMAS) stations and 10 International GNSS Service (IGS) stations in China and records the most serious conditions during 2015 and 2016. Simulations show that the average increase in Vertical Protection Level (VPL) of all visible ...

  7. Tropospheric Aerosols

    Science.gov (United States)

    Buseck, P. R.; Schwartz, S. E.

    2003-12-01

    It is widely believed that "On a clear day you can see forever," as proclaimed in the 1965 Broadway musical of the same name. While an admittedly beautiful thought, we all know that this concept is only figurative. Aside from Earth's curvature and Rayleigh scattering by air molecules, aerosols - colloidal suspensions of solid or liquid particles in a gas - limit our vision. Even on the clearest day, there are billions of aerosol particles per cubic meter of air.Atmospheric aerosols are commonly referred to as smoke, dust, haze, and smog, terms that are loosely reflective of their origin and composition. Aerosol particles have arisen naturally for eons from sea spray, volcanic emissions, wind entrainment of mineral dust, wildfires, and gas-to-particle conversion of hydrocarbons from plants and dimethylsulfide from the oceans. However, over the industrial period, the natural background aerosol has been greatly augmented by anthropogenic contributions, i.e., those produced by human activities. One manifestation of this impact is reduced visibility (Figure 1). Thus, perhaps more than in other realms of geochemistry, when considering the composition of the troposphere one must consider the effects of these activities. The atmosphere has become a reservoir for vast quantities of anthropogenic emissions that exert important perturbations on it and on the planetary ecosystem in general. Consequently, much recent research focuses on the effects of human activities on the atmosphere and, through them, on the environment and Earth's climate. For these reasons consideration of the geochemistry of the atmosphere, and of atmospheric aerosols in particular, must include the effects of human activities. (201K)Figure 1. Impairment of visibility by aerosols. Photographs at Yosemite National Park, California, USA. (a) Low aerosol concentration (particulate matter of aerodynamic diameter less than 2.5 μm, PM2.5=0.3 μg m-3; particulate matter of aerodynamic diameter less than 10

  8. Tropospheric ozone trends

    NARCIS (Netherlands)

    Guicherit, R.; Roemer, M.

    2000-01-01

    Anthropogenic emissions of chemical reactive trace gases have substantially altered the composition of the troposphere. These perturbations have caused tropospheric O3 increases, in particular in the Northern Hemisphere. It remains, however, difficult to accurately establish O3 trends throughout the

  9. Chemistry in the Troposphere.

    Science.gov (United States)

    Chameides, William L.; Davis, Douglas D.

    1982-01-01

    Topics addressed in this review of chemistry in the troposphere (layer of atmosphere extending from earth's surface to altitude of 10-16km) include: solar radiation/winds; earth/atmosphere interface; kinetic studies of atmospheric reactions; tropospheric free-radical photochemistry; instruments for nitric oxide detection; sampling…

  10. A Method to Reduce Non-Nominal Troposphere Error

    Science.gov (United States)

    Wang, Zhipeng; Xin, Pumin; Li, Rui; Wang, Shujing

    2017-01-01

    Under abnormal troposphere, Ground-Based Augmentation System (GBAS) is unable to eliminate troposphere delay, resulting in non-nominal troposphere error. This paper analyzes the troposphere meteorological data of eight International GNSS Monitoring Assessment System (iGMAS) stations and 10 International GNSS Service (IGS) stations in China and records the most serious conditions during 2015 and 2016. Simulations show that the average increase in Vertical Protection Level (VPL) of all visible satellites under non-nominal troposphere is 2.32 m and that more satellites increase the VPL. To improve GBAS integrity, this paper proposes a satellite selection method to reduce the non-nominal troposphere error. First, the number of satellites in the optimal subset is determined to be 16 based on the relationship among VPL, non-nominal troposphere error and satellite geometry. Second, the distributions of the optimal satellites are determined. Finally, optimal satellites are selected in different elevation ranges. Results show that the average VPL increase caused by non-nominal troposphere error is 1.15 m using the proposed method. Compared with the brute method and greedy method, the running rate of the proposed method is improved by 390.91% and 111.65%, respectively. In summary, the proposed method balances the satellite geometry and non-nominal troposphere error while minimizing the VPL and improving the running rate. PMID:28758983

  11. Accuracy Assessment of the Precise Point Positioning for Different Troposphere Models

    Science.gov (United States)

    Oguz Selbesoglu, Mahmut; Gurturk, Mert; Soycan, Metin

    2016-04-01

    This study investigates the accuracy and repeatability of PPP technique at different latitudes by using different troposphere delay models. Nine IGS stations were selected between 00-800 latitudes at northern hemisphere and southern hemisphere. Coordinates were obtained for 7 days at 1 hour intervals in summer and winter. At first, the coordinates were estimated by using Niell troposphere delay model with and without including north and east gradients in order to investigate the contribution of troposphere delay gradients to the positioning . Secondly, Saastamoinen model was used to eliminate troposphere path delays by using standart atmosphere parameters were extrapolated for all station levels. Finally, coordinates were estimated by using RTCA-MOPS empirical troposphere delay model. Results demonstrate that Niell troposphere delay model with horizontal gradients has better mean values of rms errors 0.09 % and 65 % than the Niell troposphere model without horizontal gradients and RTCA-MOPS model, respectively. Saastamoinen model mean values of rms errors were obtained approximately 4 times bigger than the Niell troposphere delay model with horizontal gradients.

  12. Applying Kalman filtering to investigate tropospheric effects in VLBI

    Science.gov (United States)

    Soja, Benedikt; Nilsson, Tobias; Karbon, Maria; Heinkelmann, Robert; Liu, Li; Lu, Cuixian; Andres Mora-Diaz, Julian; Raposo-Pulido, Virginia; Xu, Minghui; Schuh, Harald

    2014-05-01

    Very Long Baseline Interferometry (VLBI) currently provides results, e.g., estimates of the tropospheric delays, with a delay of more than two weeks. In the future, with the coming VLBI2010 Global Observing System (VGOS) and increased usage of electronic data transfer, it is planned that the time between observations and results is decreased. This may, for instance, allow the integration of VLBI-derived tropospheric delays into numerical weather prediction models. Therefore, future VLBI analysis software packages need to be able to process the observational data autonomously in near real-time. For this purpose, we have extended the Vienna VLBI Software (VieVS) by a Kalman filter module. This presentation describes the filter and discusses its application for tropospheric studies. Instead of estimating zenith wet delays as piece-wise linear functions in a least-squares adjustment, the Kalman filter allows for more sophisticated stochastic modeling. We start with a random walk process to model the time-dependent behavior of the zenith wet delays. Other possible approaches include the stochastic model described by turbulence theory, e.g. the model by Treuhaft and Lanyi (1987). Different variance-covariance matrices of the prediction error, depending on the time of the year and the geographic latitude, have been tested. In winter and closer to the poles, lower variances and covariances are appropriate. The horizontal variations in tropospheric delays have been investigated by comparing three different strategies: assumption of a horizontally stratified troposphere, using north and south gradients modeled, e.g., as Gauss-Markov processes, and applying a turbulence model assuming correlations between observations in different azimuths. By conducting Monte-Carlo simulations of current standard VLBI networks and of future VGOS networks, the different tropospheric modeling strategies are investigated. For this purpose, we use the simulator module of VieVS which takes into

  13. Global tropospheric ozone investigations

    Science.gov (United States)

    Browell, Edward V.

    1998-01-01

    Ozone (O3) is one of the most important trace gases in the troposphere, and it is responsible for influencing many critical chemical and radiative processes. Ozone contributes to the formation of the hydroxyl radical (OH), which is central to most chemical reactions in the lower atmosphere, and it absorbs UV, visible, and infrared radiation which affects the energy budget and atmospheric temperatures. In addition, O3 can be used as a tracer of atmospheric pollution and stratosphere troposphere exchange. At elevated concentrations, O3 can also produce detrimental biological and human health effects. The US National Research Council (NRC) Board on Sustainable Development reviewed the US Global Change Research Program (USGCRP) [NRC, 1995], and it identified tropospheric chemistry as one of the high priority areas for the USGCRP in the next decade. The NRC identified the following specific challenges in tropospheric chemistry. Although we understand the reason for the high levels of 03 over several regions of the world, we need to better establish the distribution of O3 in the troposphere in order to document and understand the changes in the abundance of global tropospheric O3. This information is needed to quantify the contribution of O3 to the Earth' s radiative balance and to understand potential impacts on the health of the biosphere. Having recognized the importance of particles in the chemistry of the stratosphere, we must determine how aerosols and clouds affect the chemical processes in the troposphere. This understanding is essential to predict the chemical composition of the atmosphere and to assess the resulting forcing effects in the climate system. We must determine if the self-cleansing chemistry of the atmosphere is changing as a result of human activities. This information is required to predict the rate at which pollutants are removed from the atmosphere. Over nearly two decades, airborne Differential Absorption Lidar (DIAL) systems have been used in

  14. OMI tropospheric NO

    NARCIS (Netherlands)

    Castellanos, P.; Boersma, K.F.; Torres, O.; Haan, De J.F.

    2015-01-01

    Biomass burning is an important and uncertain source of aerosols and NOx (NO + NO2) to the atmosphere. Satellite observations of tropospheric NO2 are essential for characterizing this emissions source, but inaccuracies in the retrieval of NO2

  15. ITG: A New Global GNSS Tropospheric Correction Model.

    Science.gov (United States)

    Yao, Yibin; Xu, Chaoqian; Shi, Junbo; Cao, Na; Zhang, Bao; Yang, Junjian

    2015-07-21

    Tropospheric correction models are receiving increasing attentions, as they play a crucial role in Global Navigation Satellite System (GNSS). Most commonly used models to date include the GPT2 series and the TropGrid2. In this study, we analyzed the advantages and disadvantages of existing models and developed a new model called the Improved Tropospheric Grid (ITG). ITG considers annual, semi-annual and diurnal variations, and includes multiple tropospheric parameters. The amplitude and initial phase of diurnal variation are estimated as a periodic function. ITG provides temperature, pressure, the weighted mean temperature (Tm) and Zenith Wet Delay (ZWD). We conducted a performance comparison among the proposed ITG model and previous ones, in terms of meteorological measurements from 698 observation stations, Zenith Total Delay (ZTD) products from 280 International GNSS Service (IGS) station and Tm from Global Geodetic Observing System (GGOS) products. Results indicate that ITG offers the best performance on the whole.

  16. Diurnal variation of tropospheric temperature at a tropical station

    Directory of Open Access Journals (Sweden)

    K. Revathy

    2001-08-01

    Full Text Available The vertical velocity in the troposphere-lower stratosphere region measured using MST radar has been utilized to evaluate the temperature profile in the region. The diurnal variation of the tropospheric temperature on one day in August 1998 at the tropical station Gadanki (13.5° N, 79.2° E has been studied using the MST radar technique. The diurnal variation of the temperature revealed a prominent diurnal variation with the peak in the afternoon hours increasingly delayed in altitude. The tropopause temperature and altitude exhibited a clear diurnal cycle.Key words. Atmospheric composition and structure (pressure, density and temperature; troposphere - composition and chemistry; instruments and technique

  17. Tropospheric Emission Spectrometer (TES) Data

    Data.gov (United States)

    National Aeronautics and Space Administration — TES focuses on the troposphere, the layer of atmosphere that stretches from the ground to the altitude at which airplanes fly. With very high spectral resolution,...

  18. Source attribution of tropospheric ozone

    Science.gov (United States)

    Butler, T. M.

    2015-12-01

    Tropospheric ozone is a harmful pollutant with adverse effects on human health and ecosystems. As well as these effects, tropospheric ozone is also a powerful greenhouse gas, with an anthropogenic radiative forcing one quarter of that of CO2. Along with methane and atmospheric aerosol, tropospheric ozone belongs to the so-called Short Lived Climate forcing Pollutants, or SLCP. Recent work has shown that efforts to reduce concentrations of SLCP in the atmosphere have the potential to slow the rate of near-term climate change, while simultaneously improving public health and reducing crop losses. Unlike many other SLCP, tropospehric ozone is not directly emitted, but is instead influenced by two distinct sources: transport of air from the ozone-rich stratosphere; and photochemical production in the troposphere from the emitted precursors NOx (oxides of nitrogen), CO (Carbon Monoxide), and VOC (volatile organic compounds, including methane). Better understanding of the relationship between ozone production and the emissions of its precursors is essential for the development of targeted emission reduction strategies. Several modeling methods have been employed to relate the production of tropospheric ozone to emissions of its precursors; emissions perturbation, tagging, and adjoint sensitivity methods all deliver complementary information about modelled ozone production. Most studies using tagging methods have focused on attribution of tropospheric ozone production to emissions of NOx, even though perturbation methods have suggested that tropospheric ozone is also sensitive to VOC, particularly methane. In this study we describe the implementation into a global chemistry-climate model of a scheme for tagging emissions of NOx and VOC with an arbitrary number of labels, which are followed through the chemical reactions of tropospheric ozone production in order to perform attribution of tropospehric ozone to its emitted precursors. Attribution is performed to both

  19. Tropospheric Halogen Chemistry

    Science.gov (United States)

    von Glasow, R.; Crutzen, P. J.

    2003-12-01

    Halogens are very reactive chemicals that are known to play an important role in anthropogenic stratospheric ozone depletion chemistry, first recognized by Molina and Rowland (1974). However, they also affect the chemistry of the troposphere. They are of special interest because they are involved in many reaction cycles that can affect the oxidation power of the atmosphere indirectly by influencing the main oxidants O3 and its photolysis product OH and directly, e.g., by reactions of the Cl radical with hydrocarbons (e.g., CH4).Already by the middle of the nineteenth century, Marchand (1852) reported the presence of bromine and iodine in rain and other natural waters. He also mentions the benefits of iodine in drinking water through the prevention of goitres and cretinism. In a prophetic monograph "Air and Rain: The Beginnings of a Chemical Climatology," Smith (1872) describes measurements of chloride in rain water, which he states to originate partly from the oceans by a process that he compares with the bursting of "soap bubbles" which produces "small vehicles" that transfer small spray droplets of seawater to the air. From deviations of the sulfate-to-chloride ratio in coastal rain compared to seawater, Smith concluded that chemical processes occur once the particles are airborne.For almost a century thereafter, however, atmospheric halogens received little attention. One exception was the work by Cauer (1939), who reported that iodine pollution has been significant in Western and Central Europe due to the inefficient burning of seaweed, causing mean gas phase atmospheric concentrations as high as or greater than 0.5 μg m-3. In his classical textbook Air Chemistry and Radioactivity, Junge (1963) devoted less than three pages to halogen gas phase chemistry, discussing chlorine and iodine. As reviewed by Eriksson (1959a, b), the main atmospheric source of halogens is sea salt, derived from the bursting of bubbles of air which are produced by ocean waves and other

  20. The New Tropospheric Product of the International GNSS Service

    Science.gov (United States)

    Byun, Sung H.; Bar-Sever, Yoaz E.; Gendt, Gerd

    2005-01-01

    We compare this new approach for generating the IGS tropospheric products with the previous approach, which was based on explicit combination of total zenith delay contributions from the IGS ACs. The new approach enables the IGS to rapidly generate highly accurate and highly reliable total zenith delay time series for many hundreds of sites, thus increasing the utility of the products to weather modelers, climatologists, and GPS analysts. In this paper we describe this new method, and discuss issues of accuracy, quality control, utility of the new products and assess its benefits.

  1. Some tests of wet tropospheric calibration for the CASA Uno Global Positioning System experiment

    Science.gov (United States)

    Dixon, T. H.; Wolf, S. Kornreich

    1990-01-01

    Wet tropospheric path delay can be a major error source for Global Positioning System (GPS) geodetic experiments. Strategies for minimizing this error are investigted using data from CASA Uno, the first major GPS experiment in Central and South America, where wet path delays may be both high and variable. Wet path delay calibration using water vapor radiometers (WVRs) and residual delay estimation is compared with strategies where the entire wet path delay is estimated stochastically without prior calibration, using data from a 270-km test baseline in Costa Rica. Both approaches yield centimeter-level baseline repeatability and similar tropospheric estimates, suggesting that WVR calibration is not critical for obtaining high precision results with GPS in the CASA region.

  2. Three dimensional ray tracing technique for tropospheric water vapor tomography using GPS measurements

    Science.gov (United States)

    Haji Aghajany, Saeid; Amerian, Yazdan

    2017-11-01

    Tropospheric water vapor has a key role in tropospheric processes and it is an important parameter in meteorology studies. Because of its non-uniform spatiotemporal distribution, modeling the spatiotemporal variations of water vapor is a challenging subject in meteorology. The GNSS tomography of the troposphere is a promising method to assess the spatiotemporal distribution of water vapor parameter in this layer. The tomography method efficiency is dependent on the ray tracing technique and GPS derived tropospheric slant wet delays. Implementing constraints and regularization methods are necessary in order to achieve the regularized solution in troposphere tomography. In this paper, the three dimensional (3D) ray tracing technique based on Eikonal equations and ERA-I data are used to perform the reconstruction the signal path, Iranian Permanent GPS Network (IPGN) measurements are used to calculate slant wet delays and the LSQR regularization technique is used to obtain a regularized tomographic solution for tropospheric water vapor. The modeled water vapor profiles are validated using radiosonde observations.

  3. Plant responses to tropospheric ozone

    Science.gov (United States)

    Tropospheric ozone is the second most abundant air pollutant and an important component of the global climate change. Over five decades of research on the phytotoxicity of ozone in model plants systems, crop plants and forest trees have provided some insight into the physiological, biochemical and m...

  4. Ozone in the Tropical Troposphere

    NARCIS (Netherlands)

    Peters, Wouter

    2002-01-01

    The aim of the research presented here is to acquire knowledge of the past, present, and future composition, stability, sensitivity, and variability of the troposphere. We focus mostly on the tropical regions because it has received little attention so far, measurements here are scarce, and large

  5. Software for Generating Troposphere Corrections for InSAR Using GPS and Weather Model Data

    Science.gov (United States)

    Moore, Angelyn W.; Webb, Frank H.; Fishbein, Evan F.; Fielding, Eric J.; Owen, Susan E.; Granger, Stephanie L.; Bjoerndahl, Fredrik; Loefgren, Johan; Fang, Peng; Means, James D.; hide

    2013-01-01

    Atmospheric errors due to the troposphere are a limiting error source for spaceborne interferometric synthetic aperture radar (InSAR) imaging. This software generates tropospheric delay maps that can be used to correct atmospheric artifacts in InSAR data. The software automatically acquires all needed GPS (Global Positioning System), weather, and Digital Elevation Map data, and generates a tropospheric correction map using a novel algorithm for combining GPS and weather information while accounting for terrain. Existing JPL software was prototypical in nature, required a MATLAB license, required additional steps to acquire and ingest needed GPS and weather data, and did not account for topography in interpolation. Previous software did not achieve a level of automation suitable for integration in a Web portal. This software overcomes these issues. GPS estimates of tropospheric delay are a source of corrections that can be used to form correction maps to be applied to InSAR data, but the spacing of GPS stations is insufficient to remove short-wavelength tropospheric artifacts. This software combines interpolated GPS delay with weather model precipitable water vapor (PWV) and a digital elevation model to account for terrain, increasing the spatial resolution of the tropospheric correction maps and thus removing short wavelength tropospheric artifacts to a greater extent. It will be integrated into a Web portal request system, allowing use in a future L-band SAR Earth radar mission data system. This will be a significant contribution to its technology readiness, building on existing investments in in situ space geodetic networks, and improving timeliness, quality, and science value of the collected data

  6. Southern Hemisphere tropospheric aerosol microphysics

    Science.gov (United States)

    Gras, John L.

    1991-01-01

    Aerosol particle-size distribution data have been obtained in the Southern Hemisphere from approximately 4-deg S to 44-deg S and between ground level and 5 km, in the vicinity of eastern Australia. The relative shape of the free-tropospheric size distribution for particles with radii larger than approximately 0.04 micron was found to be remarkably stable with time, altitude, and location for the autumn-winter periods considered. This was despite some large concentration changes, which were found to be typical of the southeastern Australian coastal region. The majority of free-troposphere large particles were found to have sulfuric acid or lightly ammoniated sulfate morphology. Large particles in the boundary layer almost exclusively had a sea-salt morphology.

  7. Satellite Observations of Tropospheric Ammonia

    Science.gov (United States)

    Shephard, M. W.; Luo, M.; Rinsland, C. P.; Cady-Pereira, K. E.; Beer, R.; Pinder, R. W.; Henze, D.; Payne, V. H.; Clough, S.; Rodgers, C. D.; Osterman, G. B.; Bowman, K. W.; Worden, H. M.

    2008-12-01

    Global high-spectral resolution (0.06 cm-1) nadir measurements from TES-Aura enable the simultaneous retrieval of a number of tropospheric pollutants and trace gases in addition to the TES standard operationally retrieved products (e.g. carbon monoxide, ozone). Ammonia (NH3) is one of the additional species that can be retrieved in conjunction with the TES standard products, and is important for local, regional, and global tropospheric chemistry studies. Ammonia emissions contribute significantly to several well-known environmental problems, yet the magnitude and seasonal/spatial variability of the emissions are poorly constrained. In the atmosphere, an important fraction of fine particulate matter is composed of ammonium nitrate and ammonium sulfate. These particles are statistically associated with health impacts. When deposited to ecosystems in excess, nitrogen, including ammonia can cause nutrient imbalances, change in ecosystem species composition, eutrophication, algal blooms and hypoxia. Ammonia is also challenging to measure in-situ. Observations of surface concentrations are rare and are particularly sparse in North America. Satellite observations of ammonia are therefore highly desirable. We recently demonstrated that tropospheric ammonia is detectable in the TES spectra and presented some corresponding preliminary retrievals over a very limited range of conditions (Beer et al., 2008). Presented here are results that expand upon these initial TES ammonia retrievals in order to evaluate/validate the retrieval results utilizing in-situ surface observations (e.g. LADCO, CASTNet, EPA /NC State) and chemical models (e.g. GEOS-Chem and CMAQ). We also present retrievals over regions of interest that have the potential to help further understand air quality and the active nitrogen cycle. Beer, R., M. W. Shephard, S. S. Kulawik, S. A. Clough, A. Eldering, K. W. Bowman, S. P. Sander, B. M. Fisher, V. H. Payne, M. Luo, G. B. Osterman, and J. R. Worden, First

  8. The Tropospheric Products of the International VLBI Service for Geodesy and Astrometry

    Science.gov (United States)

    Heinkelmann, Robert; Schwatke, Christian

    2010-01-01

    The IVS runs two tropospheric products: The IVS tropospheric parameter rapid combination monitors the zenith wet delay (ZWD) and zenith total delay (ZTD) of the rapid turnaround sessions R1 and R4. Goal of the combination is the identification and the exclusion of outliers by comparison and the assessment of the precision of current VLBI solutions in terms of tropospheric parameters. The rapid combination is done on a weekly basis four weeks after the observation files are released on IVS Data Centers. Since tropospheric and geodetic parameters, such as vertical station components, can significantly correlate, the consistency of the ZTD can be a measure of the consistency of the corresponding TRF as well. The ZWD mainly rely on accurate atmospheric pressure data. Thus, besides estimation techniques, modeling and analyst s noise, ZWD reflects differences in the atmospheric pressure data applied to the VLBI analysis. The second product, called tropospheric parameter long-term combination, aims for an accurate determination of climatological signals, such as trends of the atmospheric water vapor observed by VLBI. Therefore, the long-term homogeneity of atmospheric pressure data plays a crucial role for this product. The paper reviews the methods applied and results achieved so far and describes the new maintenance through DGFI.

  9. Instrumentation for tropospheric aerosol characterization

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.; Young, S.E.; Becker, C.H.; Coggiola, M.J. [SRI International, Menlo Park, CA (United States); Wollnik, H. [Giessen Univ. (Germany)

    1997-12-31

    A new instrument has been developed that determines the abundance, size distribution, and chemical composition of tropospheric and lower stratospheric aerosols with diameters down to 0.2 {mu}m. In addition to aerosol characterization, the instrument also monitors the chemical composition of the ambient gas. More than 25.000 aerosol particle mass spectra were recorded during the NASA-sponsored Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) field program using NASA`s DC-8 research aircraft. (author) 7 refs.

  10. The TROPOspheric Monitoring Instrument (TROPOMI)

    Science.gov (United States)

    Veefkind, Pepijn; Kleipool, Quintus; Aben, Ilse; Levelt, Pieternel

    2015-04-01

    The Copernicus Sentinel 5 Precursor (S5P), scheduled for launch in 2016, is the first of the sentinels dedicated to monitoring of the atmospheric composition. The main application areas of the mission are air quality, climate and the ozone layer. The single payload of the S5P mission is TROPOspheric Monitoring Instrument (TROPOMI). TROPOMI is a nadir viewing shortwave spectrometer that will measure in the UV-visible wavelength range (270-500 nm), the near infrared (710-770 nm) and the shortwave infrared (2314-2382 nm). TROPOMI will have an unprecedented spatial resolution of about 7x7 km2 at nadir. The spatial resolution is combined with a wide swath to allow for daily global coverage. The high spatial resolution serves two goals: (1) emissions sources can be detected with more accuracy and (2) the number of cloud-free ground pixels will increase substantially. The TROPOMI/S5P geophysical (Level 2) data products include nitrogen dioxide, carbon monoxide, ozone (total column, tropospheric column & profile), methane, sulphur dioxide, formaldehyde and aerosol and cloud parameters. In this contribution we will present the TROPOMI instrument performance and the new science opportunities that it will enable.

  11. Impact of geoengineered aerosols on the troposphere and stratosphere

    Energy Technology Data Exchange (ETDEWEB)

    Tilmes, S.; Garcia, Rolando R.; Kinnison, Douglas E.; Gettelman, A.; Rasch, Philip J.

    2009-06-27

    A coupled chemistry climate model, the Whole Atmosphere Community Climate Model was used to perform a transient climate simulation to quantify the impact of geoengineered aerosols on atmospheric processes. In contrast to previous model studies, the impact on stratospheric chemistry, including heterogeneous chemistry in the polar regions, is considered in this simulation. In the geoengineering simulation, a constant stratospheric distribution of volcanic-sized, liquid sulfate aerosols is imposed in the period 2020–2050, corresponding to an injection of 2 Tg S/a. The aerosol cools the troposphere compared to a baseline simulation. Assuming an Intergovernmental Panel on Climate Change A1B emission scenario, global warming is delayed by about 40 years in the troposphere with respect to the baseline scenario. Large local changes of precipitation and temperatures may occur as a result of geoengineering. Comparison with simulations carried out with the Community Atmosphere Model indicates the importance of stratospheric processes for estimating the impact of stratospheric aerosols on the Earth’s climate. Changes in stratospheric dynamics and chemistry, especially faster heterogeneous reactions, reduce the recovery of the ozone layer in middle and high latitudes for the Southern Hemisphere. In the geoengineering case, the recovery of the Antarctic ozone hole is delayed by about 30 years on the basis of this model simulation. For the Northern Hemisphere, a onefold to twofold increase of the chemical ozone depletion occurs owing to a simulated stronger polar vortex and colder temperatures compared to the baseline simulation, in agreement with observational estimates.

  12. Constrained isentropic models of tropospheric dynamics

    NARCIS (Netherlands)

    Bokhove, Onno; Verkley, W.T.M.

    2003-01-01

    A two-layer isentropic model consisting of a tropospheric and a stratospheric layer is simplified using perturbation analysis while preserving the Hamiltonian structure. The first approximation applies when the thickness of the stratospheric layer is much larger than the tropospheric layer, such

  13. Tropospheric response to an 'ozone depletion'-like polar stratospheric cooling

    Science.gov (United States)

    Sun, L.; Chen, G.; Robinson, W. A.

    2013-12-01

    By following the setup of Kushner and Polvani (2006) in a simplified dynamical model, we add a polar stratospheric cooling in the springtime to mimic the ozone depletion, and try to investigate the role of polar vortex breakdown, also known as stratospheric final warming (SFW), in the tropospheric response to stratospheric changes. Overall, the circulation anomaly associated with such cooling bears a remarkable resemblance to the Southern Hemisphere climate trends due to ozone depletion, including poleward shift of the tropospheric jet and poleward expansion of the Hadley cell. We then categorize the 80 members into those SFWs are delayed, and those SFWs are not, and calculate the response separately. The response for the years in which SFWs are delayed are very similar to the total one, while the stratosphere is only characterized by the localized cooling for those years in which SFWs are not delayed, without any clear downward influence. This suggests that ozone depletion affects the Southern Hemisphere climate through delaying the SFWs. We also find that interannual variability in the stratospheric and tropospheric circulation can be organized by the timing of SFWs, similar to the observed climate trends.

  14. Tropospheric radiowave propagation beyond the horizon

    CERN Document Server

    Du Castel, François

    1966-01-01

    Tropospheric Radiowave Propagation Beyond the Horizon deals with developments concerning the tropospheric propagation of ultra-short radio waves beyond the horizon, with emphasis on the relationship between the theoretical and the experimental. Topics covered include the general conditions of propagation in the troposphere; general characteristics of propagation beyond the horizon; and attenuation in propagation. This volume is comprised of six chapters and begins with a brief historical look at the various stages that have brought the technique of transhorizon links to its state of developmen

  15. Delayed Puberty

    DEFF Research Database (Denmark)

    Kolby, Nanna; Busch, Alexander Siegfried; Juul, Anders

    2017-01-01

    Delayed puberty can be a source of great concern and anxiety, although it usually is caused by a self-limiting variant of the normal physiological timing named constitutional delay of growth and puberty (CDGP). Delayed puberty can, however, also be the first presentation of a permanent condition...... of diagnostic evaluation today remain in distinguishing the benign CDGP from underlying pathological causes such as hypogonadotropic hypogonadism (HH) and hypergonadotropic hypogonadism. Several techniques have been investigated for this purpose and are reviewed in this chapter; however, no single test is yet...

  16. Delayed growth

    Science.gov (United States)

    ... 4 years Developmental milestones record - 5 years Causes Constitutional growth delay refers to children who are small ... nutrition expert who can help you choose the right foods to offer your child. What to Expect ...

  17. Delayed Ejaculation

    Science.gov (United States)

    ... bladder rather than out of the penis Psychological causes of delayed ejaculation include: Depression, anxiety or other mental health conditions Relationship problems due to stress, poor communication or other concerns ...

  18. Delayed Ejaculation

    Science.gov (United States)

    ... of stress Delayed ejaculation Symptoms & causes Diagnosis & treatment Advertisement Mayo Clinic does not endorse companies or products. ... a Job Site Map About This Site Twitter Facebook Google YouTube Pinterest Mayo Clinic is a not- ...

  19. Application of GPS Measurements for Ionospheric and Tropospheric Modelling

    Science.gov (United States)

    Rajendra Prasad, P.; Abdu, M. A.; Furlan, Benedito. M. P.; Koiti Kuga, Hélio

    solar maximum period. In the equatorial region the irregularity structures are highly elongated in the north-south direction and are discrete in the east-west direction with dimensions of several hundred km. With such spatial distribution of irregularities needs to determine how often the GPS receivers fails to provide navigation aid with the available constellation. The effects of scintillation on the performance of GPS navigation systems in the equatorial region can be analyzed through commissioning few ground receivers. Incidentally there are few GPS receivers near these latitudes. Despite the recent advances in the ionosphere and tropospheric delay modeling for geodetic applications of GPS, the models currently used are not very precise. The conventional and operational ionosphere models viz. Klobuchar, Bent, and IRI models have certain limitations in providing very precise accuracies at all latitudes. The troposphere delay modeling also suffers in accuracy. The advances made in both computing power and knowledge of the atmosphere leads to make an effort to upgrade some of these models for improving delay corrections in GPS navigation. The ionospheric group delay corrections for orbit determination can be minimized using duel frequency. However in single frequency measurements the group delay correction is an involved task. In this paper an investigation is carried out to estimate the model coefficients of ionosphere along with precise orbit determination modeling using GPS measurements. The locations of the ground-based receivers near equator are known very exactly. Measurements from these ground stations to a precisely known satellite carrying duel receiver is used for orbit determination. The ionosphere model parameters can be refined corresponding to spatially distributed GPS receivers spread over Brazil. The tropospheric delay effects are not significant for the satellites by choosing appropriate elevation angle. However it needs to be analyzed for user like

  20. A directional model of tropospheric horizontal gradients in Global Positioning System and its application for particular weather scenarios

    Science.gov (United States)

    Masoumi, Salim; McClusky, Simon; Koulali, Achraf; Tregoning, Paul

    2017-04-01

    Improper modeling of horizontal tropospheric gradients in GPS analysis induces errors in estimated parameters, with the largest impact on heights and tropospheric zenith delays. The conventional two-axis tilted plane model of horizontal gradients fails to provide an accurate representation of tropospheric gradients under weather conditions with asymmetric horizontal changes of refractivity. A new parametrization of tropospheric gradients whereby an arbitrary number of gradients are estimated as discrete directional wedges is shown via simulations to significantly improve the accuracy of recovered tropospheric zenith delays in asymmetric gradient scenarios. In a case study of an extreme rain event that occurred in September 2002 in southern France, the new directional parametrization is able to isolate the strong gradients in particular azimuths around the GPS stations consistent with the "V" shape spatial pattern of the observed precipitation. In another study of a network of GPS stations in the Sierra Nevada region where highly asymmetric tropospheric gradients are known to exist, the new directional model significantly improves the repeatabilities of the stations in asymmetric gradient situations while causing slightly degraded repeatabilities for the stations in normal symmetric gradient conditions. The average improvement over the entire network is ˜31%, while the improvement for one of the worst affected sites P631 is ˜49% (from 8.5 mm to 4.3 mm) in terms of weighted root-mean-square (WRMS) error and ˜82% (from -1.1 to -0.2) in terms of skewness. At the same station, the use of the directional model changes the estimates of zenith wet delay by 15 mm (˜25%).

  1. Tropospheric products of the second GOP European GNSS reprocessing (1996–2014

    Directory of Open Access Journals (Sweden)

    J. Dousa

    2017-09-01

    Full Text Available In this paper, we present results of the second reprocessing of all data from 1996 to 2014 from all stations in International Association of Geodesy (IAG Reference Frame Sub-Commission for Europe (EUREF Permanent Network (EPN as performed at the Geodetic Observatory Pecný (GOP. While the original goal of this research was to ultimately contribute to the realization of a new European Terrestrial Reference System (ETRS, we also aim to provide a new set of GNSS (Global Navigation Satellite System tropospheric parameter time series with possible applications to climate research. To achieve these goals, we improved a strategy to guarantee the continuity of these tropospheric parameters and we prepared several variants of troposphere modelling. We then assessed all solutions in terms of the repeatability of coordinates as an internal evaluation of applied models and strategies and in terms of zenith tropospheric delays (ZTDs and horizontal gradients with those of the ERA-Interim numerical weather model (NWM reanalysis. When compared to the GOP Repro1 (first EUREF reprocessing solution, the results of the GOP Repro2 (second EUREF reprocessing yielded improvements of approximately 50 and 25 % in the repeatability of the horizontal and vertical components, respectively, and of approximately 9 % in tropospheric parameters. Vertical repeatability was reduced from 4.14 to 3.73 mm when using the VMF1 mapping function, a priori ZHD (zenith hydrostatic delay, and non-tidal atmospheric loading corrections from actual weather data. Raising the elevation cut-off angle from 3 to 7° and then to 10° increased RMS from coordinates' repeatability, which was then confirmed by independently comparing GNSS tropospheric parameters with the NWM reanalysis. The assessment of tropospheric horizontal gradients with respect to the ERA-Interim revealed a strong sensitivity of estimated gradients to the quality of GNSS antenna tracking performance. This impact was

  2. Tropospheric products of the second GOP European GNSS reprocessing (1996-2014)

    Science.gov (United States)

    Dousa, Jan; Vaclavovic, Pavel; Elias, Michal

    2017-09-01

    In this paper, we present results of the second reprocessing of all data from 1996 to 2014 from all stations in International Association of Geodesy (IAG) Reference Frame Sub-Commission for Europe (EUREF) Permanent Network (EPN) as performed at the Geodetic Observatory Pecný (GOP). While the original goal of this research was to ultimately contribute to the realization of a new European Terrestrial Reference System (ETRS), we also aim to provide a new set of GNSS (Global Navigation Satellite System) tropospheric parameter time series with possible applications to climate research. To achieve these goals, we improved a strategy to guarantee the continuity of these tropospheric parameters and we prepared several variants of troposphere modelling. We then assessed all solutions in terms of the repeatability of coordinates as an internal evaluation of applied models and strategies and in terms of zenith tropospheric delays (ZTDs) and horizontal gradients with those of the ERA-Interim numerical weather model (NWM) reanalysis. When compared to the GOP Repro1 (first EUREF reprocessing) solution, the results of the GOP Repro2 (second EUREF reprocessing) yielded improvements of approximately 50 and 25 % in the repeatability of the horizontal and vertical components, respectively, and of approximately 9 % in tropospheric parameters. Vertical repeatability was reduced from 4.14 to 3.73 mm when using the VMF1 mapping function, a priori ZHD (zenith hydrostatic delay), and non-tidal atmospheric loading corrections from actual weather data. Raising the elevation cut-off angle from 3 to 7° and then to 10° increased RMS from coordinates' repeatability, which was then confirmed by independently comparing GNSS tropospheric parameters with the NWM reanalysis. The assessment of tropospheric horizontal gradients with respect to the ERA-Interim revealed a strong sensitivity of estimated gradients to the quality of GNSS antenna tracking performance. This impact was demonstrated at the

  3. Overview on Role of the Troposphere

    Science.gov (United States)

    Newman, Paul A.

    2003-01-01

    The troposphere is the lower boundary for the stratosphere. As such, it provides a radiative boundary that is a large source of IR flux into for the stratosphere and scattered UV-Vis energy. Planetary-scale waves that are forced in the troposphere can propagate into the stratosphere, providing a large additional source of energy for the stratosphere. This wave energy is the principal energy source for the Brewer-Dobson circulation. Medium-scale wave can also propagate into the lower stratosphere, but have a smaller effect. The final source of energy for the stratosphere comes from smaller scale disturbances such as gravity waves, mixed Rossby-gravity modes, and Kelvin waves. These smaller scale waves provide an important source of energy for the stratosphere. In this presentation we will cover these tropospheric sources of energy that effect the stratosphere. In particular, we will focus attention on planetary scale waves and their forcings.

  4. Tropospheric Ozone and Photochemical Smog

    Science.gov (United States)

    Sillman, S.

    2003-12-01

    emitted species, in a process that is driven by sunlight and is accelerated by warm temperatures. This smog is largely the product of gasoline-powered engines (especially automobiles), although coal-fired industry can also generate photochemical smog. The process of photochemical smog formation was first identified by Haagen-Smit and Fox (1954) in association with Los Angeles, a city whose geography makes it particularly susceptible to this type of smog formation. Sulfate aerosols and organic particulates are often produced concurrently with ozone, giving rise to a characteristic milky-white haze associated with this type of air pollution.Today ozone and particulates are recognized as the air pollutants that are most likely to affect human health adversely. In the United States, most major metropolitan areas have periodic air pollution events with ozone in excess of government health standards. Violations of local health standards also occur in major cities in Canada and in much of Europe. Other cities around the world (especially Mexico City) also experience very high ozone levels. In addition to urban-scale events, elevated ozone occurs in region-wide events in the eastern USA and in Western Europe, with excess ozone extending over areas of 1,000 km2 or more. Ozone plumes of similar extent are found in the tropics (especially in Central Africa) at times of high biomass burning (e.g., Jenkins et al., 1997; Chatfield et al., 1998). In some cases ozone associated with biomass burning has been identified at distances up to 104 km from its sources (Schultz et al., 1999).Ozone also has a significant impact on the global troposphere, and ozone chemistry is a major component of global tropospheric chemistry. Global background ozone concentrations are much lower than urban or regional concentrations during pollution events, but there is evidence that the global background has increased as a result of human activities (e.g., Wang and Jacob, 1998; Volz and Kley, 1988). A rise in

  5. Semi-Lagrangian modelling of tropospheric ozone

    Science.gov (United States)

    Pudykiewicz, Janusz A.; Kallaur, A.; Smolarkiewicz, Piotr K.

    1997-07-01

    The occurrence of high concentrations of ozone in the lower part of the troposphere is considered as one of the most important issues of tropospheric chemistry. The chemical mechanisms of tropospheric ozone formation are complex, and highly variable meteorological conditions contribute additionally to difficulties in an accurate prediction of ozone episodes. An effective way to increase our understanding of the problem and eventually improve our ability to predict the concentration of tropospheric ozone and to formulate emission control strategies is by applying a comprehensive model representing accurately the interaction between meteorological processes and chemical reactions. This paper presents a 3-dimensional semi-Lagrangian, chemical tracer model (CTM) featuring an accurate transport algorithm, comprehensive oxidants chemistry and deposition modules. The CTM is executed in off line mode with a semi-Lagrangian, nonhydrostatic, mesoscale meteorological model that contains an extensive parameterization of physical processes (including a boundary layer scheme and clouds). The system of models was run for a time period of 6days in order to generate a tropospheric ozone field during a smog episode observed in the eastern part of North America, in the beginning of August 1988. The numerical simulation was performed on grids with resolution of 20 and 40km with 25 vertical levels. The emissions inventory considered in the simulation included point sources, surface biogenic sources, surface mobile sources and surface non-mobile sources. An evaluation of the model results against observations clearly indicates the ability of the system to simulate regional aspects of a tropospheric ozone episode. The model performance compares well to other models' results reported in the literature. An important achievement of this work is improving the physical realism of simulations by using highly accurate, nonoscillatory semi-Lagrangian advection transport algorithms.

  6. Impact of climate variability on tropospheric ozone

    Energy Technology Data Exchange (ETDEWEB)

    Grewe, Volker [Institut fuer Physik der Atmosphaere, DLR-Oberpfaffenhofen, 82234 Wessling (Germany)

    2007-03-01

    A simulation with the climate-chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of realistic external forcings, like observed sea surface temperatures (e.g. El Nino), major volcanic eruption, solar cycle, concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate-chemistry interactions are included, like the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning). However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NO{sub x} emissions are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early 90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere-troposphere exchange (related to Northern Hemisphere

  7. Stratospheric ozone transboundary transport to upper troposphere North Africa

    CSIR Research Space (South Africa)

    Ture, K

    2011-09-01

    Full Text Available Stratosphere-troposphere exchange (STE) influences the chemical composition of both the stratosphere and the troposphere and represents an important aspect of global change [Butchart and Scaife, 2001]. It is also often associated with severe weather...

  8. Tropospheric Ozone from the TOMS TDOT (TOMS-Direct-Ozone-in-Troposphere) Technique During SAFARI-2000

    Science.gov (United States)

    Stone, J. B.; Thompson, A. M.; Frolov, A. D.; Hudson, R. D.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    There are a number of published residual-type methods for deriving tropospheric ozone from TOMS (Total Ozone Mapping Spectrometer). The basic concept of these methods is that within a zone of constant stratospheric ozone, the tropospheric ozone column can be computed by subtracting stratospheric ozone from the TOMS Level 2 total ozone column, We used the modified-residual method for retrieving tropospheric ozone during SAFARI-2000 and found disagreements with in-situ ozone data over Africa in September 2000. Using the newly developed TDOT (TOMS-Direct-Ozone-in-Troposphere) method that uses TOMS radiances and a modified lookup table based on actual profiles during high ozone pollution periods, new maps were prepared and found to compare better to soundings over Lusaka, Zambia (15.5 S, 28 E), Nairobi and several African cities where MOZAIC aircraft operated in September 2000. The TDOT technique and comparisons are described in detail.

  9. Performance Comparison of Tropospheric Propagation Models: Ray-Trace Analysis Results Using Worldwide Tropospheric Databases

    National Research Council Canada - National Science Library

    Choi, Junho

    1997-01-01

    The report describes the performance of three databases and tropospheric models and covers the analysis results for several selected refractivity and range/angle error models, three empirical database...

  10. Weakening of lower tropospheric temperature gradient between ...

    Indian Academy of Sciences (India)

    e-mail: bawiskar@hotmail.com bawiskar@tropmet.res.in. The study shows that in the scenario of global warming temperature gradient (TG) between Indian landmass and Arabian Sea/Bay of Bengal is significantly decreasing in the lower troposphere with maxima around 850hPa. TG during pre-monsoon (March to May) is ...

  11. Tropospheric Emission Spectrometer and Airborne Emission Spectrometer

    Science.gov (United States)

    Glavich, T.; Beer, R.

    1996-01-01

    The Tropospheric Emission Spectrometer (TES) is an instrument being developed for the NASA Earth Observing System Chemistry Platform. TES will measure the distribution of ozone and its precursors in the lower atmosphere. The Airborne Emission Spectrometer (AES) is an aircraft precursor to TES. Applicable descriptions are given of instrument design, technology challenges, implementation and operations for both.

  12. New Directions: Watching over tropospheric hydroxyl (OH)

    NARCIS (Netherlands)

    Lelieveld, J.|info:eu-repo/dai/nl/411295810; Brenninkmeijer, C.A.M.; Joeckel, P.; Isaksen, I.S.A.; Krol, M.C.|info:eu-repo/dai/nl/078760410; Mak, J.E.; Dlugokencky, E.; Montzka, S.A.; Novelli, P.C.; Peters, W.; Tans, P.P.

    2006-01-01

    Mean tropospheric hydroxyl radical (OH) abundance is often used as a measure of the oxidation capacity (or “self-cleansing”) of the atmosphere. The primary mechanism by which atmospheric pollutant gases are removed from the atmosphere is initiated by the reaction with OH. As a result, large

  13. TROPOSPHERIC AEROSOL PROGRAM, PROGRAM PLAN, MARCH 2001

    Energy Technology Data Exchange (ETDEWEB)

    SCHWARTZ,S.E.; LUNN,P.

    2001-03-01

    The goal of Tropospheric Aerosol Program (TAP) will be to develop the fundamental scientific understanding required to construct tools for simulating the life cycle of tropospheric aerosols--the processes controlling their mass loading, composition, and microphysical properties, all as a function of time, location, and altitude. The TAP approach to achieving this goal will be by conducting closely linked field, modeling, laboratory, and theoretical studies focused on the processes controlling formation, growth, transport, and deposition of tropospheric aerosols. This understanding will be represented in models suitable for describing these processes on a variety of geographical scales; evaluation of these models will be a key component of TAP field activities. In carrying out these tasks TAP will work closely with other programs in DOE and in other Federal and state agencies, and with the private sector. A forum to directly work with our counterparts in industry to ensure that the results of this research are translated into products that are useful to that community will be provided by NARSTO (formerly the North American Research Strategy on Tropospheric Ozone), a public/private partnership, whose membership spans government, the utilities, industry, and university researchers in Mexico, the US, and Canada.

  14. Tropospheric ozone as a fungal elicitor

    Indian Academy of Sciences (India)

    Tropospheric ozone has been proven to trigger biochemical plant responses that are similar to the ones induced by an attack of fungal pathogens, i.e. it resembles fungal elicitors. This suggests that ozone can represent a valid tool for the study of stress responses and induction of resistance to pathogens. This review ...

  15. Characteristics of microwave propagation in vapourised troposphere ...

    African Journals Online (AJOL)

    Microwave communication equipment design in temperate region may not be very suitable in the tropics because the characteristics of the troposphere as the medium of propagation differ ... The meteorological vertical data taken from radiosonde confirms evidence of super-refraction and ducting of the microwave signal.

  16. Delayed Puberty

    DEFF Research Database (Denmark)

    Kolby, Nanna; Busch, Alexander Siegfried; Juul, Anders

    2017-01-01

    or a symptom of an underlying disease. The diagnosis delayed puberty is made if there are no signs of puberty at an age corresponding to 2 SD above the population mean age at pubertal onset, often translated into 14 years in boys. Delayed puberty among boys is a frequent presentation in pediatrics....... The underlying reasons for the large variation in the age at pubertal onset are not fully established; however, nutritional status and socioeconomic and environmental factors are known to be influencing, and a significant amount of influencing genetic factors have also been identified. The challenges...... of diagnostic evaluation today remain in distinguishing the benign CDGP from underlying pathological causes such as hypogonadotropic hypogonadism (HH) and hypergonadotropic hypogonadism. Several techniques have been investigated for this purpose and are reviewed in this chapter; however, no single test is yet...

  17. Upper tropospheric ice sensitivity to sulfate geoengineering

    Science.gov (United States)

    Visioni, Daniele; Pitari, Giovanni; Mancini, Eva

    2017-04-01

    In light of the Paris Agreement which aims to keep global warming under 2 °C in the next century and considering the emission scenarios produced by the IPCC for the same time span, it is likely that to remain below that threshold some kind of geoengineering technique will have to be deployed. Amongst the different methods, the injection of sulfur into the stratosphere has received much attention considering its effectiveness and affordability. Aside from the rather well established surface cooling sulfate geoengineering (SG) would produce, the investigation on possible side-effects of this method is still ongoing. For instance, some recent studies have investigated the effect SG would have on upper tropospheric cirrus clouds, expecially on the homogenous freezing mechanisms that produces the ice particles (Kuebbeler et al., 2012). The goal of the present study is to better understand the effect of thermal and dynamical anomalies caused by SG on the formation of ice crystals via homogeneous freezing by comparing a complete SG simulation with a RCP4.5 reference case and with a number of sensitivity studies where atmospheric temperature changes in the upper tropospheric region are specified in a schematic way as a function of the aerosol driven stratospheric warming and mid-lower tropospheric cooling. These changes in the temperature profile tend to increase atmospheric stabilization, thus decreasing updraft and with it the amount of water vapor available for homogeneous freezing in the upper troposphere. However, what still needs to be assessed is the interaction between this dynamical effect and the thermal effects of tropospheric cooling (which would increase ice nucleation rates) and stratospheric warming (which would probably extend to the uppermost troposphere via SG aerosol gravitational settling, thus reducing ice nucleation rates), in order to understand how they combine together. Changes in ice clouds coverage could be important for SG, because cirrus ice

  18. A grid-based tropospheric product for China using a GNSS network

    Science.gov (United States)

    Zhang, Hongxing; Yuan, Yunbin; Li, Wei; Zhang, Baocheng; Ou, Jikun

    2017-11-01

    Tropospheric delay accounts for one source of error in global navigation satellite systems (GNSS). To better characterize the tropospheric delays in the temporal and spatial domain and facilitate the safety-critical use of GNSS across China, a method is proposed to generate a grid-based tropospheric product (GTP) using the GNSS network with an empirical tropospheric model, known as IGGtrop. The prototype system generates the GTPs in post-processing and real-time modes and is based on the undifferenced and uncombined precise point positioning (UU-PPP) technique. GTPs are constructed for a grid form (2.0{°}× 2.5{°} latitude-longitude) over China with a time resolution of 5 min. The real-time GTP messages are encoded in a self-defined RTCM3 format and broadcast to users using NTRIP (networked transport of RTCM via internet protocol), which enables efficient and safe transmission to real-time users. Our approach for GTP generation consists of three sequential steps. In the first step, GNSS-derived zenith tropospheric delays (ZTDs) for a network of GNSS stations are estimated using UU-PPP. In the second step, vertical adjustments for the GNSS-derived ZTDs are applied to address the height differences between the GNSS stations and grid points. The ZTD height corrections are provided by the IGGtrop model. Finally, an inverse distance weighting method is used to interpolate the GNSS-derived ZTDs from the surrounding GNSS stations to the location of the grid point. A total of 210 global positioning system (GPS) stations from the crustal movement observation network of China are used to generate the GTPs in both post-processing and real-time modes. The accuracies of the GTPs are assessed against with ERA-Interim-derived ZTDs and the GPS-derived ZTDs at 12 test GPS stations, respectively. The results show that the post-processing and real-time GTPs can provide the ZTDs with accuracies of 1.4 and 1.8 cm, respectively. We also apply the GTPs in real-time kinematic GPS PPP

  19. Tracking the sources of tropospheric ozone

    Science.gov (United States)

    Butler, T. M.; Churkina, G.; Coates, J.; Grote, R.; Mar, K.; von Schneidemesser, E.; Zhu, S.

    2013-12-01

    Tropospheric ozone is a harmful pollutant with adverse effects on human health and ecosystems. As well as these effects, tropospheric ozone is also a powerful greenhouse gas, with an anthropogenic radiative forcing one quarter of that of CO2. Along with methane and atmospheric aerosol, tropospheric ozone belongs to the so-called Short Lived Climate forcing Pollutants, or SLCP. Recent work has shown that efforts to reduce concentrations of SLCP in the atmosphere have the potential to slow the rate of near-term climate change, while simultaneously improving public health and reducing crop losses. Unlike many other SLCP, tropospehric ozone is not directly emitted, but is instead influenced by two distinct sources: transport of air from the ozone-rich stratosphere; and photochemical production in the troposphere from the emitted precursors NOx (oxides of nitrogen), CO (Carbon Monoxide), and VOC (volatile organic compounds, including methane). Better understanding of the relationship between ozone production and the emissions of its precursors is essential for the development of targeted emission reduction strategies. Several modeling methods have been employed to relate the production of tropospheric ozone to emissions of its precursors; emissions perturbation, tagging, and adjoint sensitivity methods all deliver complementary information about modelled ozone production. Most studies using tagging methods have focused on attribution of tropospheric ozone production to emissions of NOx, even though perturbation methods have suggested that tropospheric ozone is also sensitive to VOC, particularly methane. In this set of studies we examine the attribution of tropospheric ozone to emissions of VOC using a tagging approach, whereby each VOC oxidation intermediate in model chemical mechanisms is tagged with the identity of its primary emitted compound, allowing modelled ozone production to be directly attributed to all emitted VOCs in the model. Using a global model we

  20. Extratropical Stratosphere-Troposphere Mass Exchange

    Science.gov (United States)

    Schoeberl, Mark R.

    2004-01-01

    Understanding the exchange of gases between the stratosphere and the troposphere is important for determining how pollutants enter the stratosphere and how they leave. This study does a global analysis of that the exchange of mass between the stratosphere and the troposphere. While the exchange of mass is not the same as the exchange of constituents, you can t get the constituent exchange right if you have the mass exchange wrong. Thus this kind of calculation is an important test for models which also compute trace gas transport. In this study I computed the mass exchange for two assimilated data sets and a GCM. The models all agree that amount of mass descending from the stratosphere to the troposphere in the Northern Hemisphere extra tropics is approx. 10(exp 10) kg/s averaged over a year. The value for the Southern Hemisphere by about a factor of two. ( 10(exp 10) kg of air is the amount of air in 100 km x 100 km area with a depth of 100 m - roughly the size of the D.C. metro area to a depth of 300 feet.) Most people have the idea that most of the mass enters the stratosphere through the tropics. But this study shows that almost 5 times more mass enters the stratosphere through the extra-tropics. This mass, however, is quickly recycled out again. Thus the lower most stratosphere is a mixture of upper stratospheric air and tropospheric air. This is an important result for understanding the chemistry of the lower stratosphere.

  1. Anthropogenic perturbations of tropospheric ion composition

    Science.gov (United States)

    Beig, G.; Brasseur, G.

    This paper presents a simple model of the vertical distribution of the most abundant positive ions in the troposphere. The model is based on a simple ion chemical scheme, measured rate constants, and observed or calculated atmospheric densities of parent neutral compounds. It suggests that in many cases the most abundant gaseous ions are heavy protonated water cluster ions of pyridine, picoline and lutidine with ammonia molecules attached (pyridinated cluster ions) in the lower troposphere (below 7 km altitude), acetone cluster ions in the upper troposphere (between 7 and 15 km) and methyl cyanide cluster ions above 15 km. The relative abundance of heavy clustered aerosol ions is predicted to be highest near the surface. The model suggests that ion composition could be perturbed as a result of human activities (i.e., increasing emissions of parent neutral species including alkaline compounds), and that in particular, the relative atmospheric abundance of pyridinated water cluster ions is increasing dramatically and should further increase in the future.

  2. Global tropospheric hydroxyl distribution, budget and reactivity

    Science.gov (United States)

    Lelieveld, Jos; Gromov, Sergey; Pozzer, Andrea; Taraborrelli, Domenico

    2016-10-01

    The self-cleaning or oxidation capacity of the atmosphere is principally controlled by hydroxyl (OH) radicals in the troposphere. Hydroxyl has primary (P) and secondary (S) sources, the former mainly through the photodissociation of ozone, the latter through OH recycling in radical reaction chains. We used the recent Mainz Organics Mechanism (MOM) to advance volatile organic carbon (VOC) chemistry in the general circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry) and show that S is larger than previously assumed. By including emissions of a large number of primary VOC, and accounting for their complete breakdown and intermediate products, MOM is mass-conserving and calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Whereas previously P and S were found to be of similar magnitude, the present work indicates that S may be twice as large, mostly due to OH recycling in the free troposphere. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. With a mean OH recycling probability of about 67 %, global OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary primary and secondary OH formation mechanisms in pristine and polluted environments in the continental and marine troposphere, connected through long-range transport of O3, can maintain stable global OH levels.

  3. Tropospheric Composition Change observed from Space (Invited)

    Science.gov (United States)

    Richter, A.; Hilboll, A.; Leitao, J.; Vrekoussis, M.; Wittrock, F.; Burrows, J. P.

    2010-12-01

    The composition of the troposphere is largely influenced by surface emissions of both natural and anthropogenic origins. These emissions change over time as result of human activities and natural variability, leading to varying atmospheric levels of primary and secondary pollutants. Satellite observations of sun light scattered back by the surface and the atmosphere can be used to retrieve information on atmospheric trace gases by application of optical absorption spectroscopy. In the UV and visible part of the spectrum, these measurements have good sensitivity to the lower troposphere providing information on relevant species such as O3, NO2, SO2, HCHO or glyoxal. Here, we report on recent results on tropospheric composition changes obtained from the GOME, SCIAMACHY and GOME-2 instruments which have a combined data record of nearly 15 years. The focus is on NO2 which shows an increasing trend over Asia and many large cities in countries with growing economies. At the same time, significant reductions are observed over the US and Europe, probably as result of changes in environmental legislation. SO2 signals have been decreasing over the US since 1996 while a strong upward trend was evident over China until recently when desulphurisation of power plant emissions came into effect. There also is evidence for increases in VOC levels over China which could be either of anthropogenic origin or from biogenic emissions.

  4. Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    Science.gov (United States)

    Chance, Kelly; Liu, Xiong; Suleiman, Raid M.; Flittner, David E.; Al-Saadi, Jassim; Janz, Scott J.

    2014-06-01

    TEMPO, selected by NASA as the first Earth Venture Instrument, will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest-cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, reducing uncertainty in air quality predictions by 50 %. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO makes the first tropospheric trace gas measurements from GEO, by building on the heritage of five spectrometers flown in low-earth-orbit (LEO). These LEO instruments measure the needed spectra, although at coarse spatial and temporal resolutions, to the precisions required for TEMPO and use retrieval algorithms developed for them by TEMPO Science Team members and currently running in operational environments. This makes TEMPO an innovative use of a well-proven technique, able to produce a revolutionary data set. TEMPO provides much of the atmospheric measurement

  5. Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    Science.gov (United States)

    Zoogman, P.; Liu, X.; Suleiman, R. M.; Pennington, W. F.; Flittner, D. E.; Al-Saadi, J. A.; Hilton, B. B.; Nicks, D. K.; Newchurch, M. J.; Carr, J. L.; hide

    2016-01-01

    TEMPO (Tropospheric Emissions: Monitoring of Pollution) was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (approximately 2.1 kilometers N/S by 4.4 kilometers E/W at 36.5 degrees N, 100 degrees W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide),water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the

  6. VMF3/GPT3: refined discrete and empirical troposphere mapping functions

    Science.gov (United States)

    Landskron, Daniel; Böhm, Johannes

    2017-09-01

    Incorrect modeling of troposphere delays is one of the major error sources for space geodetic techniques such as Global Navigation Satellite Systems (GNSS) or Very Long Baseline Interferometry (VLBI). Over the years, many approaches have been devised which aim at mapping the delay of radio waves from zenith direction down to the observed elevation angle, so-called mapping functions. This paper contains a new approach intended to refine the currently most important discrete mapping function, the Vienna Mapping Functions 1 (VMF1), which is successively referred to as Vienna Mapping Functions 3 (VMF3). It is designed in such a way as to eliminate shortcomings in the empirical coefficients b and c and in the tuning for the specific elevation angle of 3° . Ray-traced delays of the ray-tracer RADIATE serve as the basis for the calculation of new mapping function coefficients. Comparisons of modeled slant delays demonstrate the ability of VMF3 to approximate the underlying ray-traced delays more accurately than VMF1 does, in particular at low elevation angles. In other words, when requiring highest precision, VMF3 is to be preferable to VMF1. Aside from revising the discrete form of mapping functions, we also present a new empirical model named Global Pressure and Temperature 3 (GPT3) on a 5°× 5° as well as a 1°× 1° global grid, which is generally based on the same data. Its main components are hydrostatic and wet empirical mapping function coefficients derived from special averaging techniques of the respective (discrete) VMF3 data. In addition, GPT3 also contains a set of meteorological quantities which are adopted as they stand from their predecessor, Global Pressure and Temperature 2 wet. Thus, GPT3 represents a very comprehensive troposphere model which can be used for a series of geodetic as well as meteorological and climatological purposes and is fully consistent with VMF3.

  7. The global troposphere - Biogeochemical cycles, chemistry, and remote sensing

    Science.gov (United States)

    Levine, J. S.; Allario, F.

    1982-01-01

    The chemical composition of the troposphere is controlled by various biogeochemical cycles that couple the atmosphere with the oceans, the solid earth and the biosphere, and by atmospheric photochemical/chemical reactions. These cycles and reactions are discussed and a number of key questions concerning tropospheric composition and chemistry for the carbon, nitrogen, oxygen and sulfur species are identified. Next, various remote sensing techniques and instruments capable of measuring and monitoring tropospheric species from the ground, aircraft and space to address some of these key questions are reviewed. Future thrusts in remote sensing of the troposphere are also considered.

  8. Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency

    Science.gov (United States)

    Flock, W. L.

    1981-01-01

    When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.

  9. Absolute determination of local tropospheric OH concentrations

    Science.gov (United States)

    Armerding, Wolfgang; Comes, Franz-Josef

    1994-01-01

    Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.

  10. Tropospheric Emissions: Monitoring of Pollution Overview

    Science.gov (United States)

    Chance, Kelly; Liu, Xiong; Suleiman, Raid M.; Flittner, David; Al-Saadi, Jay; Janz, Scott

    2015-01-01

    TEMPO is now well into its implementation phase, having passed both its Key Decision Point C and the Critical Design Review (CDR) for the instrument. The CDR for the ground systems will occur in March 2016 and the CDR for the Mission component at a later date, after the host spacecraft has been selected. TEMPO is on schedule to measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions by 50 percent. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO provides much of the atmospheric measurement capability recommended for GEO-CAPE in the 2007 National Research Council Decadal Survey, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond. Instruments from Europe (Sentinel 4) and Asia (GEMS) will

  11. Tropospheric emissions: Monitoring of pollution (TEMPO)

    Science.gov (United States)

    Zoogman, P.; Liu, X.; Suleiman, R. M.; Pennington, W. F.; Flittner, D. E.; Al-Saadi, J. A.; Hilton, B. B.; Nicks, D. K.; Newchurch, M. J.; Carr, J. L.; Janz, S. J.; Andraschko, M. R.; Arola, A.; Baker, B. D.; Canova, B. P.; Chan Miller, C.; Cohen, R. C.; Davis, J. E.; Dussault, M. E.; Edwards, D. P.; Fishman, J.; Ghulam, A.; González Abad, G.; Grutter, M.; Herman, J. R.; Houck, J.; Jacob, D. J.; Joiner, J.; Kerridge, B. J.; Kim, J.; Krotkov, N. A.; Lamsal, L.; Li, C.; Lindfors, A.; Martin, R. V.; McElroy, C. T.; McLinden, C.; Natraj, V.; Neil, D. O.; Nowlan, C. R.; O`Sullivan, E. J.; Palmer, P. I.; Pierce, R. B.; Pippin, M. R.; Saiz-Lopez, A.; Spurr, R. J. D.; Szykman, J. J.; Torres, O.; Veefkind, J. P.; Veihelmann, B.; Wang, H.; Wang, J.; Chance, K.

    2017-01-01

    TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution ( 2.1 km N/S×4.4 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide), water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring

  12. Evaluation of Atmospheric Loading and Improved Troposphere Modelling

    Science.gov (United States)

    Zelensky, Nikita P.; Chinn, Douglas S.; Lemoine, F. G.; Le Bail, Karine; Pavlis, Despina E.

    2012-01-01

    Forward modeling of non-tidal atmospheric loading displacements at geodetic tracking stations have not routinely been included in Doppler Orbitography and Radiopositionning Integrated by Satellite (DORIS) or Satellite Laser Ranging (SLR) station analyses for either POD applications or reference frame determination. The displacements which are computed from 6-hourly models such as the ECMWF and can amount to 3-10 mm in the east, north and up components depending on the tracking station locations. We evaluate the application of atmospheric loading in a number ways using the NASA GSFC GEODYN software: First we assess the impact on SLR & DORIS-determined orbits such as Jason-2, where we evaluate the impact on the tracking data RMS of fit and how the total orbits are changed with the application of this correction. Preliminary results show an RMS radial change of 0.5 mm for Jason-2 over 54 cycles and a total change in the Z-centering of the orbit of 3 mm peak-to-peak over one year. We also evaluate the effects on other DORIS-satellites such as Cryosat-2, Envisat and the SPOT satellites. In the second step, we produce two SINEX time series based on data from available DORIS satellites and assess the differences in WRMS, scale and Helmert translation parameters. Troposphere refraction is obviously an important correction for radiometric data types such as DORIS. We evaluate recent improvements in DORIS processing at GSFC including the application of the Vienna Mapping Function (VMF1) grids with a-priori hydrostatic (VZHDs) and wet (VZWDs) zenith delays. We reduce the gridded VZHD at the stations height using pressure and temperature derived from GPT (strategy 1) and Saastamoinen. We discuss the validation of the VMF1 implementation and its application to the Jason-2 POD processing, compared to corrections using the Niell mapping function and the GMF. Using one year of data, we also assess the impact of the new troposphere corrections on the DORIS-only solutions, most

  13. Near-real-time regional troposphere models for the GNSS precise point positioning technique

    Science.gov (United States)

    Hadas, T.; Kaplon, J.; Bosy, J.; Sierny, J.; Wilgan, K.

    2013-05-01

    The GNSS precise point positioning (PPP) technique requires high quality product (orbits and clocks) application, since their error directly affects the quality of positioning. For real-time purposes it is possible to utilize ultra-rapid precise orbits and clocks which are disseminated through the Internet. In order to eliminate as many unknown parameters as possible, one may introduce external information on zenith troposphere delay (ZTD). It is desirable that the a priori model is accurate and reliable, especially for real-time application. One of the open problems in GNSS positioning is troposphere delay modelling on the basis of ground meteorological observations. Institute of Geodesy and Geoinformatics of Wroclaw University of Environmental and Life Sciences (IGG WUELS) has developed two independent regional troposphere models for the territory of Poland. The first one is estimated in near-real-time regime using GNSS data from a Polish ground-based augmentation system named ASG-EUPOS established by Polish Head Office of Geodesy and Cartography (GUGiK) in 2008. The second one is based on meteorological parameters (temperature, pressure and humidity) gathered from various meteorological networks operating over the area of Poland and surrounding countries. This paper describes the methodology of both model calculation and verification. It also presents results of applying various ZTD models into kinematic PPP in the post-processing mode using Bernese GPS Software. Positioning results were used to assess the quality of the developed models during changing weather conditions. Finally, the impact of model application to simulated real-time PPP on precision, accuracy and convergence time is discussed.

  14. Representing the effects of stratosphere–troposphere ...

    Science.gov (United States)

    Downward transport of ozone (O3) from the stratosphere can be a significant contributor to tropospheric O3 background levels. However, this process often is not well represented in current regional models. In this study, we develop a seasonally and spatially varying potential vorticity (PV)-based function to parameterize upper tropospheric and/or lower stratospheric (UTLS) O3 in a chemistry transport model. This dynamic O3–PV function is developed based on 21-year ozonesonde records from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) with corresponding PV values from a 21-year Weather Research and Forecasting (WRF) simulation across the Northern Hemisphere from 1990 to 2010. The result suggests strong spatial and seasonal variations of O3 ∕ PV ratios which exhibits large values in the upper layers and in high-latitude regions, with highest values in spring and the lowest values in autumn over an annual cycle. The newly developed O3 ∕ PV function was then applied in the Community Multiscale Air Quality (CMAQ) model for an annual simulation of the year 2006. The simulated UTLS O3 agrees much better with observations in both magnitude and seasonality after the implementation of the new parameterization. Considerable impacts on surface O3 model performance were found in the comparison with observations from three observational networks, i.e., EMEP, CASTNET and WDCGG. With the new parameterization, the negative bias in spring is reduced from

  15. Effect of some climatic parameters on tropospheric and total ozone ...

    Indian Academy of Sciences (India)

    tions of tropospheric ozone are toxic. Moreover, tropospheric ozone itself acts as an effective green- .... lar traffic, thermal power plants, very busy ports, small and large industries of iron and jute mills of. Howrah city ...... Pekarek S 2008 Ozone production by a dc corona discharge in air contaminated by n-heptane; J. Phys.

  16. Halogens and the Chemistry of the Free Troposphere

    Science.gov (United States)

    Lary, David John

    2004-01-01

    The role of halogens in both the marine boundary layer and the stratosphere has long been recognized, while their role in the free troposphere is often not considered in global chemical models. However, a careful examination of free-tropospheric chemistry constrained by observations using a full chemical data assimilation system shows that halogens do play a significant role in the free troposphere. In particular, the chlorine initiation of methane oxidation in the free troposphere can contribute more than 10%, and in some regions up to 50%, of the total rate of initiation. The initiation of methane oxidation by chlorine is particularly important below the polar vortex and in northern mid-latitudes. Likewise, the hydrolysis of BrONO2 alone can contribute more than 35% of the HNO3 production rate in the free-troposphere.

  17. Climate-chemistry interaction affecting tropospheric ozone

    Science.gov (United States)

    Mao, Huiting

    1999-09-01

    Tropospheric ozone, an important radiative-chemical species, has been observed increasing especially at northern midlatitudes during the past few decades. This dissertation addresses climate-chemistry interaction associated with such increases in three aspects using observations as well as atmospheric chemistry and climate models. Ozone impact on climate is first evaluated by radiative forcing calculations due to observed ozone changes. It is found that a 10% increase in tropospheric ozone causes a radiative forcing of 0.17 Wm-2 using a fixed temperature (FT) method or 0.13 Wm-2 using a fixed dynamic heating (FDH) method, which is comparable to the radiative forcing 0.26 (FT) and -0.09 Wm-2 (FDH) caused by the stratospheric ozone depletion during the 1980s. Second, radiative forcing due to changes in ozone precursors is estimated. Ozone changes in response to a 20% reduction in surface NOx emission in six regions around the globe differ between regions. A maximum decrease in ozone column reaches 5% in southeast Asia and the central Atlantic Ocean, inducing a local radiative forcing of up to -0.1 Wm-2 in those regions. It indicates that surface NOx emission changes can potentially affect regional climate. Third, the effects of climate and climate changes on atmospheric chemistry are addressed with two studies. One study investigates the effects of global warming on methane and ozone, and another looks into cloud effects on photodissociation rate constants. Calculations based on the IPCC business-as-usual scenario indicate that by 2050, temperature and moisture increases can suppress methane and tropospheric ozone increases by 17% and 11%, respectively, in reference to the 1990 concentrations. The combined effects offset the global warming induced forcing 3.90 Wm -2 by -0.46 Wm-2. A one-dimensional study suggests that a typical cirrus cloud (τ = 2) can significantly increase J(O1D) and J(NO2) around the tropopause with a maximum of 21%. Geographical and seasonal

  18. Reactive Nitrogen, Ozone and Ozone Production in the Arctic Troposphere and the Impact of Stratosphere-Troposphere Exchange

    Science.gov (United States)

    Liang, Q.; Rodriquez, J. M.; Douglass, A. R.; Crawford, J. H.; Apel, E.; Bian, H.; Blake, D. R.; Brune, W.; Chin, M.; Colarco, P. R.; hide

    2011-01-01

    We analyze the aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellite (ARCTAS) mission together with the GEOS-5 CO simulation to examine O3 and NOy in the Arctic and sub-Arctic region and their source attribution. Using a number of marker tracers and their probability density distributions, we distinguish various air masses from the background troposphere and examine their contribution to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has mean O3 of approximately 60 ppbv and NOx of approximately 25 pptv throughout spring and summer with CO decreases from approximately 145 ppbv in spring to approximately 100 ppbv in summer. These observed CO, NOx and O3 mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in the past two decades in processes that could have changed the Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses with mean O3 concentration of 140-160 ppbv are the most important direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin is the only notable driver of net O3 formation in the Arctic due to its sustainable high NOx (75 pptv in spring and 110 pptv in summer) and NOy (approximately 800 pptv in spring and approximately 1100 pptv in summer) levels. The ARCTAS measurements present observational evidence suggesting significant conversion of nitrogen from HNO3 to NOx and then to PAN (a net formation of approximately 120 pptv PAN) in summer when air of stratospheric origin is mixed with tropospheric background during stratosphere-to-troposphere transport. These findings imply that an adequate representation of stratospheric O3 and NOy input are essential in accurately simulating O3

  19. Iodine chemistry in the troposphere and its effect on ozone

    Science.gov (United States)

    Saiz-Lopez, A.; Fernandez, R. P.; Ordóñez, C.; Kinnison, D. E.; Gómez Martín, J. C.; Lamarque, J.-F.; Tilmes, S.

    2014-12-01

    Despite the potential influence of iodine chemistry on the oxidizing capacity of the troposphere, reactive iodine distributions and their impact on tropospheric ozone remain almost unexplored aspects of the global atmosphere. Here we present a comprehensive global modelling experiment aimed at estimating lower and upper limits of the inorganic iodine burden and its impact on tropospheric ozone. Two sets of simulations without and with the photolysis of IxOy oxides (i.e. I2O2, I2O3 and I2O4) were conducted to define the range of inorganic iodine loading, partitioning and impact in the troposphere. Our results show that the most abundant daytime iodine species throughout the middle to upper troposphere is atomic iodine, with an annual average tropical abundance of (0.15-0.55) pptv. We propose the existence of a "tropical ring of atomic iodine" that peaks in the tropical upper troposphere (~11-14 km) at the equator and extends to the sub-tropics (30° N-30° S). Annual average daytime I / IO ratios larger than 3 are modelled within the tropics, reaching ratios up to ~20 during vigorous uplift events within strong convective regions. We calculate that the integrated contribution of catalytic iodine reactions to the total rate of tropospheric ozone loss (IOx Loss) is 2-5 times larger than the combined bromine and chlorine cycles. When IxOy photolysis is included, IOx Loss represents an upper limit of approximately 27, 14 and 27% of the tropical annual ozone loss for the marine boundary layer (MBL), free troposphere (FT) and upper troposphere (UT), respectively, while the lower limit throughout the tropical troposphere is ~9%. Our results indicate that iodine is the second strongest ozone-depleting family throughout the global marine UT and in the tropical MBL. We suggest that (i) iodine sources and its chemistry need to be included in global tropospheric chemistry models, (ii) experimental programs designed to quantify the iodine budget in the troposphere should include

  20. Understanding Tropospheric Ozone Variability in the Arctic

    Science.gov (United States)

    McClure-Begley, A.; Petropavlovskikh, I. V.; Crepinsek, S.; Uttal, T.; Skov, H.

    2016-12-01

    The Arctic is a region that has been subject to drastic changes in the climate partially due to transported pollutants which strongly impact the composition of the atmosphere and associated feedbacks. Tropospheric ozone is an atmospheric species formed by the reaction of precursor species (NOx, CO, VOC's) in the presence of UV radiation and drives complex interactions which can result in impacts on atmospheric conditions in the Arctic. As an important greenhouse gas, ozone has a significant influence on the photochemical characteristics, oxidation capacity, and radiative forcing of the atmosphere and at high levels has negative impacts on public health and overall ecosystem functioning. In the Arctic, tropospheric ozone has variable characteristics in time and space. Seasonal variation of ozone is controlled by many factors influencing the production and destruction of ozone. The arctic ozone conditions are strongly influenced by seasonal destruction events, arctic haze, transport of pollution from Asia and influence from precursor compounds released from wildfires. This study investigates long-term ozone variation, seasonal surface ozone conditions, and characterizes deviations from expected ozone levels at four arctic ozone measurement locations (Barrow Alaska, Tiksi Russia, Summit Greenland, and Villum Station Greenland). Frequency of ozone depletion events and high ozone episodes for each station over time provides a context for the changing conditions of ozone in the arctic. NOAA Hysplit back-trajectory analysis, satellite imagery, NOAA Smoke verification model, co-located carbon monoxide, carbon dioxide, and aerosol optical depth measurements are used to understand the dominant source of pollution, pollutant composition, and the interactions due to meteorological conditions that result in anomalies in the ozone mixing ratio records. Characterization of ozone behavior and influences on the measurement locations is essential for understanding the spatial and

  1. Upper-tropospheric moistening in response to anthropogenic warming

    Science.gov (United States)

    Chung, Eui-Seok; Soden, Brian; Sohn, B. J.; Shi, Lei

    2014-01-01

    Water vapor in the upper troposphere strongly regulates the strength of water-vapor feedback, which is the primary process for amplifying the response of the climate system to external radiative forcings. Monitoring changes in upper-tropospheric water vapor and scrutinizing the causes of such changes are therefore of great importance for establishing the credibility of model projections of past and future climates. Here, we use coupled ocean–atmosphere model simulations under different climate-forcing scenarios to investigate satellite-observed changes in global-mean upper-tropospheric water vapor. Our analysis demonstrates that the upper-tropospheric moistening observed over the period 1979–2005 cannot be explained by natural causes and results principally from an anthropogenic warming of the climate. By attributing the observed increase directly to human activities, this study verifies the presence of the largest known feedback mechanism for amplifying anthropogenic climate change. PMID:25071183

  2. Upper tropospheric water vapour variability over tropical latitudes ...

    Indian Academy of Sciences (India)

    Upper tropospheric water vapour variability over tropical latitudes observed using radiosonde and satellite measurements. Ghouse Basha ... Keywords. Water vapour; radiosonde; satellite measurements. ... National Atmospheric Research Laboratory (NARL), Department of Space, Government of India, Gadanki, PB No. 123 ...

  3. MSU (Microwave Sounding Unit) Daily Troposphere Temperatures and Precipitation

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of two MSU tropospheric temperatures levels and precipitation which are described in detail below. The NOAA satellites contributing to this...

  4. Upper-tropospheric moistening in response to anthropogenic warming.

    Science.gov (United States)

    Chung, Eui-Seok; Soden, Brian; Sohn, B J; Shi, Lei

    2014-08-12

    Water vapor in the upper troposphere strongly regulates the strength of water-vapor feedback, which is the primary process for amplifying the response of the climate system to external radiative forcings. Monitoring changes in upper-tropospheric water vapor and scrutinizing the causes of such changes are therefore of great importance for establishing the credibility of model projections of past and future climates. Here, we use coupled ocean-atmosphere model simulations under different climate-forcing scenarios to investigate satellite-observed changes in global-mean upper-tropospheric water vapor. Our analysis demonstrates that the upper-tropospheric moistening observed over the period 1979-2005 cannot be explained by natural causes and results principally from an anthropogenic warming of the climate. By attributing the observed increase directly to human activities, this study verifies the presence of the largest known feedback mechanism for amplifying anthropogenic climate change.

  5. The role of halogen species in the troposphere.

    Science.gov (United States)

    Platt, U; Hönninger, G

    2003-07-01

    While the role of reactive halogen species (e.g. Cl, Br) in the destruction of the stratospheric ozone layer is well known, their role in the troposphere was investigated only since their destructive effect on boundary layer ozone after polar sunrise became obvious. During these 'Polar Tropospheric Ozone Hole' events O(3) is completely destroyed in the lowest approximately 1000 m of the atmosphere on areas of several million square kilometres. Up to now it was assumed that these events were confined to the polar regions during springtime. However, during the last few years significant amounts of BrO and Cl-atoms were also found outside the Arctic and Antarctic boundary layer. Recently even higher BrO mixing ratios (up to 176 ppt) were detected by optical absorption spectroscopy (DOAS) in the Dead Sea basin during summer. In addition, evidence is accumulating that BrO (at levels around 1-2 ppt) is also occurring in the free troposphere at all latitudes. In contrast to the stratosphere, where halogens are released from species, which are very long lived in the troposphere, likely sources of boundary layer Br and Cl are autocatalytic oxidation of sea salt halides (the 'Bromine Explosion'), while precursors of free tropospheric BrO and coastal IO probably are short-lived organo-halogen species. At the levels suggested by the available measurements reactive halogen species have a profound effect on tropospheric chemistry: In the polar boundary layer during 'halogen events' ozone is usually completely lost within hours or days. In the free troposphere the effective O(3)-losses due to halogens could be comparable to the known photochemical O(3) destruction. Further interesting consequences include the increase of OH levels and (at low NO(X)) the decrease of the HO(2)/OH ratio in the free troposphere.

  6. A new diagnostic for tropospheric ozone production

    Science.gov (United States)

    Edwards, Peter M.; Evans, Mathew J.

    2017-11-01

    Tropospheric ozone is important for the Earth's climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain-like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

  7. A new diagnostic for tropospheric ozone production

    Directory of Open Access Journals (Sweden)

    P. M. Edwards

    2017-11-01

    Full Text Available Tropospheric ozone is important for the Earth's climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain-like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model–model comparisons to better identify the root causes of model differences.

  8. Aerosol composition of the tropical upper troposphere

    Directory of Open Access Journals (Sweden)

    K. D. Froyd

    2009-07-01

    Full Text Available Aerosol composition was measured by the NOAA single-particle mass spectrometer (PALMS aboard the NASA WB-57 high altitude aircraft platform during two Aura Validation Experiment (AVE campaigns based in Costa Rica in 2004 and 2006. These studies yielded the most complete set of aerosol composition measurements to date throughout the tropical tropopause layer (TTL and tropical lower stratosphere. We describe the aerosol properties of the tropical atmosphere and use composition tracers to examine particle sources, the role of recent convection, and cirrus-forming potential in the TTL. Tropical dynamics and regional air sources played principal roles in dictating tropospheric aerosol properties. There was a sharp change in aerosol chemical composition at about 12 km altitude coincident with a change in convective influence. Below this level, maritime convection lofted condensable material that generated acidic, sulfate-rich aerosol. These particles contained significant amounts of methanesulfonic acid (MSA and showed evidence of cloud processes. In contrast, continental convection injected particles and precursors directly into the TTL, yielding a population of neutralized, organic-rich aerosol. The organics were often highly oxidized and particles with oxidized organics also contained nitrate. Above the tropopause, chemical composition gradually changed toward sulfuric acid particles but neutralized particles were still abundant 2 km above the tropopause. Deep continental convection, though sporadic and geographically localized, may strongly influence TTL aerosol properties on a global scale. The abundance of organic-rich aerosol may inhibit ice nucleation and formation of tropopause level cirrus.

  9. Delayed Orgasm and Anorgasmia

    OpenAIRE

    JENKINS, Lawrence C.; Mulhall, John P.

    2015-01-01

    Delayed orgasm/anorgasmia defined as the persistent or recurrent difficulty, delay in, or absence of attaining orgasm after sufficient sexual stimulation, which causes personal distress. Delayed orgasm and anorgasmia are associated with significant sexual dissatisfaction. A focused medical history can shed light on the potential etiologies; which include: medications, penile sensation loss, endocrinopathies, penile hyperstimulation and psychological etiologies, amongst others. Unfortunately, ...

  10. Verification of the optimum tropospheric parameters setting for the kinematic PPP analysis

    Science.gov (United States)

    Hirata, Y.; Ohta, Y.

    2015-12-01

    Kinematic GNSS analysis is useful for extraction of the crustal deformation phenomena between seconds to one day such as coseismic and postseismic deformation after a large earthquake. The kinematic GNSS analysis, however, have fundamental difficulties for the separation between unknown parameters such as the site coordinate and tropospheric parameters, caused by a strong correlation between each other. Thus, we focused on the improvement of the separation precision between coordinate time series of kinematic PPP and wet zenith tropospheric delay (WZTD) based on the comprehensive search of the parameter space. We used GIPSY-OASIS II Ver. 6.3 software for kinematic PPP processing of whole GEONET sites in 10 March 2011. We applied the every 6 hours nominal WZTD value as a priori information based on the ECMWF global numerical climate model. For the coordinate time series and tropospheric parameters, we assumed white noise and random walk stochastic process, respectively. These unknown parameters are very sensitive to assumed process noise for each stochastic process. Thus, we searched for the optimum two variable parameters; wet zenith tropospheric parameter (named as TROP) and its gradient (named as GRAD). We defined the optimum parameters, which minimized the standard deviation of coordinate time series.We firstly checked the spatial distribution of optimum pair of TROP and GRAD. Even though the optimum parameters showed the certain range (TROP: 2×10-8 ~ 6×10-7 (horizontal), 5.5×10-9 ~ 2×10-8 (vertical); GRAD: 2×10-10 ~ 6×10-9 (horizontal), 2×10-10 ~ 1×10-8 (vertical) (unit: km·s-½)), we found they showed the large diversity. It suggests there are strong heterogeneity of atmospheric state. We also estimated temporal variations of optimum TROP and GRAD in specific site. We analyzed the data through 2010 at GEONET 940098 station located in the most southern part of Kyusyu, Japan. Obtained time series of optimum GRAD showed clear annual variation, and the

  11. Effect of clouds on photolysis and oxidants in the troposphere

    Science.gov (United States)

    Tie, Xuexi; Madronich, Sasha; Walters, Stacy; Zhang, Renyi; Rasch, Phil; Collins, William

    2003-10-01

    Cloud layers in the troposphere influence photolysis rates (J values) and hence concentrations of chemical species. In order to study the impact of clouds on photolysis rates and oxidants, we have developed a simplified version of the National Center for Atmospheric Research (NCAR) Tropospheric Ultraviolet-Visible (TUV) model and have coupled the simplified TUV (otherwise known as the fast TUV (FTUV)) into the NCAR/Atmospheric Chemistry Division global transport chemical model (Model for Ozone and Related Chemical Tracers (MOZART-2)). The FTUV model has the same physical processes as the TUV model, except that the wavelength bins between 121 and 750 nm are reduced from 140 to 17. As a result, FTUV is about 8 times faster than the original TUV. Differences in the calculated photolysis rates between TUV and FTUV are generally less than 5% in the troposphere. Subgrid vertical distributions of clouds are also considered in the calculation of photolysis rates in MOZART-2. The method used in this study is a mixed maximum and random overlap scheme. The subgrid method increases the computation time for photolysis rates by a factor of 3 compared to a simple method in which clouds are uniformly distributed over the MOZART-2 grids. Our calculation shows that the uniform cloud distribution method tends to significantly overestimate back scattering on the top of clouds and overestimates the impact on photochemistry in the troposphere. The results suggest that clouds have important impacts on tropospheric chemistry. Global mean OH concentration increases by about 20% due to the impact of clouds. As a result, the calculated CH4 lifetime changes to 11 years for clear sky and 9 years for cloudy sky. The latter value is closer to the methane lifetime estimated from previous studies. Calculated CO surface concentrations are compared with observed values, showing an improvement when the impact of clouds on the photolysis rates is taken into account. Clouds also have important impacts

  12. Tropospheric Ozone as a Short-lived Chemical Climate Forcer

    Science.gov (United States)

    Pickering, Kenneth E.

    2012-01-01

    Tropospheric ozone is the third most important greenhouse gas according to the most recent IPCC assessment. However, tropospheric ozone is highly variable in both space and time. Ozone that is located in the vicinity of the tropopause has the greatest effect on climate forcing. Nitrogen oxides (NOx) are the most important precursors for ozone In most of the troposphere. Therefore, pollution that is lofted upward in thunderstorm updrafts or NOx produced by lightning leads to efficient ozone production in the upper troposphere, where ozone is most important climatically. Global and regional model estimates of the impact of North American pollution and lightning on ozone radiative forcing will be presented. It will be shown that in the Northern Hemisphere summer, the lightning effect on ozone radiative forcing can dominate over that of pollution, and that the radiative forcing signal from North America extends well into Europe and North Africa. An algorithm for predicting lightning flash rates and estimating lightning NOx emissions is being incorporated into the NASA GEOS-5 Chemistry and Climate Model. Changes in flash rates and emissions over an ENSO cycle and in future climates will be assessed, along with the resulting changes in upper tropospheric ozone. Other research on the production of NOx per lightning flash and its distribution in the vertical based on cloud-resolving modeling and satellite observations will be presented. Distributions of NO2 and O3 over the Middle East from the OMI instrument on NASA's Aura satellite will also be shown.

  13. Rapid increases in tropospheric ozone production and export from China

    Science.gov (United States)

    Verstraeten, Willem W.; Neu, Jessica L.; Williams, Jason E.; Bowman, Kevin W.; Worden, John R.; Boersma, K. Folkert

    2015-09-01

    Rapid population growth and industrialization have driven substantial increases in Asian ozone precursor emissions over the past decade, with highly uncertain impacts on regional and global tropospheric ozone levels. According to ozonesonde measurements, tropospheric ozone concentrations at two Asian sites have increased by 1 to 3% per year since 2000, an increase thought to contribute to positive trends in the ozone levels observed at North America’s West Coast. However, model estimates of the Asian contribution to North American ozone levels are not well-constrained by observations. Here we interpret Aura satellite measurements of tropospheric concentrations of ozone and its precursor NO2, along with its largest natural source, stratospheric ozone, using the TM5 global chemistry-transport model. We show that tropospheric ozone concentrations over China have increased by about 7% between 2005 and 2010 in response to two factors: a rise in Chinese emissions by about 21% and increased downward transport of stratospheric ozone. Furthermore, we find that transport from China of ozone and its precursors has offset about 43% of the 0.42 DU reduction in free-tropospheric ozone over the western United States that was expected between 2005 and 2010 as a result of emissions reductions associated with federal, state and local air quality policies. We conclude that global efforts may be required to address regional air quality and climate change.

  14. Trends of tropospheric ozone over Europe

    Energy Technology Data Exchange (ETDEWEB)

    Roemer, M.

    1996-12-31

    The purpose of the study on the title subject is to investigate the phenomena which have contributed to the observed trends of surface concentrations of ozone (O{sub 3}) and related species in The Netherlands and nearby countries. The presence in the European troposphere of relatively high concentrations of so-called ozone precursors establish a net chemical production of ozone. Since the atmospheric residence time of methane (CH{sub 4}) is much longer than that of all other VOC-species the rest is often referred to as non-methane volatile organic compounds (NMVOCs). The photo-stationary state relations are a set of three chemical reactions which rapidly converts ozone and nitrogen monoxide (NO) into nitrogen dioxide and oxygen (O{sub 2}) and vice versa. In NO{sub x}-rich environments such as in The Netherlands, this set of reactions transforms much of the ozone into NO{sub 2} which therefore can be regarded as potential ozone. Under such conditions it is convenient to use oxidant which is a conserved quantity for the photo-stationary state relations. The combination of NO{sub x} and VOCs produces ozone, but also other secondary species such as peroxyacetylnitrate (PAN). There are, however, a few differences between the formation of ozone and PAN and there are differences in their background levels as well. PAN concentrations in Europe are strongly determined by local (European) production, much more than the ozone concentrations in Europe. Therefore, studying trends of PAN concentrations is useful in distinguishing the contributions of different processes to the trends of ozone. Important aspects which possibly have contributed to trends of ozone concentrations are mentioned and discussed. Several aspects concerning the quantitative analysis of trends of surface concentrations of ozone, oxidant, PAN, NOX and NMVOS were investigated. The emphasis in this study is on the contribution of European emission changes since 1980 to the trends of ozone and oxidant

  15. Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

    Directory of Open Access Journals (Sweden)

    Q. Liang

    2011-12-01

    Full Text Available We use aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS mission to examine the distributions and source attributions of O3 and NOy in the Arctic and sub-Arctic region. Using a number of marker tracers, we distinguish various air masses from the background troposphere and examine their contributions to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has a mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreasing from ~145 ppbv in spring to ~100 ppbv in summer. These observed mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in emissions and stratospheric ozone layer in the past two decades that influence Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses, with mean O3 concentrations of 140–160 ppbv, are significant direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin displays net O3 formation in the Arctic due to its sustainable, high NOx (75 pptv in spring and 110 pptv in summer and NOy (~800 pptv in spring and ~1100 pptv in summer. The air masses influenced by the stratosphere sampled during ARCTAS-B also show conversion of HNO3 to PAN. This active production of PAN is the result of increased degradation of ethane in the stratosphere-troposphere mixed air mass to form CH3CHO, followed by subsequent formation of PAN under high NOx conditions. These findings imply that an adequate representation of stratospheric NOy input, in addition to

  16. The Governing Processes and Timescales of Stratosphere-to-Troposphere Transport and its Contribution to Ozone in the Arctic Troposphere

    Science.gov (United States)

    Liang, Q.; Douglass, A. R.; Duncan, B. N.; Stolarski, R. S.; Witte, J. C.

    2009-01-01

    We used the seasonality of a combination of atmospheric trace gases and idealized tracers to examine stratosphere-to-troposphere transport and its influence on tropospheric composition in the Arctic. Maximum stratosphere-to-troposphere transport of CFCs and O3 occurs in April as driven by the Brewer-Dobson circulation. Stratosphere-troposphere exchange (STE) occurs predominantly between 40 deg N to 80 deg N with stratospheric influx in the mid-latitudes (30-70 deg N) accounting for 67.81 percent of the air of stratospheric origin in the Northern Hemisphere extratropical troposphere. Transport from the lower stratosphere to the lower troposphere (LT) takes three months on average, one month to cross the tropopause, the second month to travel from the upper troposphere (UT) to the middle troposphere (MT), and the third month to reach the LT. During downward transport, the seasonality of a trace gas can be greatly impacted by wet removal and chemistry. A comparison of idealized tracers with varying lifetimes suggests that when initialized with the same concentrations and seasonal cycles at the tropopause, trace gases that have shorter lifetimes display lower concentrations, smaller amplitudes, and earlier seasonal maxima during transport to the LT. STE contributes to O3 in the Arctic troposphere directly from the transport of O3 and indirectly from the transport of NOy . Direct transport of O3 from the stratosphere accounts for 78 percent of O3 in the Arctic UT with maximum contributions occurring from March to May. The stratospheric contribution decreases significantly in the MT/LT (20.25 percent of total O3) and shows a very weak March.April maximum. Our NOx budget analysis in the Arctic UT shows that during spring and summer, the stratospheric injection of NO y-rich air increases NOx concentrations above the 20 pptv threshold level, thereby shifting the Arctic UT from a regime of net photochemical ozone loss to one of net production with rates as high as +16 ppbv/month.

  17. Halogen chemistry reduces tropospheric O3 radiative forcing

    DEFF Research Database (Denmark)

    Sherwen, Tomás; Evans, Mat J.; Carpenter, Lucy J.

    2017-01-01

    to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3......  ∼ 50 % of this reduction to increased bromine flux from the stratosphere,  ∼ 35 % to the ocean–atmosphere iodine feedback, and  ∼ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm−2) is greater than that from...... the radiative forcing of stratospheric O3 (∼ 0.05 Wm−2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (∼ 25 %)...

  18. First determination of the tropospheric CO abundance in Saturn

    Science.gov (United States)

    Fouchet, Thierry; Lellouch, Emmanuel; Cavalié, Thibault; Bézard, Bruno

    2017-10-01

    In Giant Planets, CO has two potential origins: i) an external source in form of cometary impacts, infalling ring/satellite dust or/and interplanetary particles; ii) an internal origin that involves convective transport from the deep, dense, hot atmosphere where the thermodynamic equilibrium CO abundance is relatively large.In Saturn, submilimeter stratospheric CO emissions have been detected (Cavalié et al. A&A, 510, A88, 2010; Cavalié et al. Icarus, 203, 531, 2009), suggesting a cometary impact 200 years ago. In contrast, no observation was in position to confirm or rule out the presence of CO in Saturn's troposphere (Noll et al. Icarus, 89, 168, 1990).Here, we present CRIRES/ELT 5-μm observations of Saturn that definitely confirm the presence of CO in Saturn's troposphere. We will present the derived CO abundance and its implication for Saturn's tropospheric transport rate and water deep abundance.

  19. Tropospheric Emission Spectrometer for the Earth Observing System

    Science.gov (United States)

    Glavich, Thomas A.; Beer, Reinhard

    1991-01-01

    A Tropospheric Emission Spectrometer (TES) for the Earth Observing System (EOS) series of polar-orbiting platforms is described. TES is aimed at studying tropospheric chemistry, in particular, the exchange of gases between the surface and the atmosphere, urban and regional pollution, acid rain precursors, sources and sinks of greenhouse gases, and the interchange of gases between the troposphere and the stratosphere. TES is a high-resolution (0.025/cm) infrared Fourier transform spectrometer operating in the passive thermal-emission mode in a very wide spectral range (600 to 4350/cm; 2.3 to 16.7 microns). TES has 32 spatial pixels in each of four optically conjugated linear detector arrays, each optimized for a different spectral region.

  20. A search for solar related changes in tropospheric weather

    Science.gov (United States)

    Mohanakumar, K.

    1989-01-01

    The possibility that solar variations associated with the 11-year solar cycle may be the cause of the changes in tropospheric weather and climate has been the subject to scientific investigation for several decades. Meteorologists are greatly concerned with the changes in tropospheric phenomena. An attempt was made to find solar activity related changes in tropospheric weather, by the modulation of the quasi-biennial oscillation (QBO) of zonal wind at 50 mb. Rainfall and surface temperature data for a period of about three solar cycles, 1953 to 1988, from various stations in the Indian subcontinent were utilized. By extension, a possible teleconnection was looked for between the temperature changes in middle atmospheric levels and surface temperature when the data are stratified according to east or west phase of the QBO. The temperature data were averaged for January and February to represent the winter temperature and for July and August to represent the summer temperature.

  1. Tropospheric Ozone Over the North Pacific from Ozonesdonde Observations

    Science.gov (United States)

    Oltmans, S. J.; Johnson, B. J.; Harris, J. M.; Thompson, A. M.; Liu, H. Y.; Voemel, H.; Chan, C. Y.; Fujimoto, T.; Brackett, V. G.; Chang, W. L.

    2003-01-01

    As part of the TRACE-P mission, ozone vertical profile measurements were made at a number of locations in the North Pacific. At most of the sites there is also a multi-year record of ozonesonde observations. From seven locations in the western Pacific (Hong Kong; Taipei; Jeju Island, Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the central Pacific (Hilo, HI), and a site on the west coast of the U.S. (Trinidad Head, CA) both a seasonal and event specific picture of tropospheric ozone over the North Pacific emerges. At all of the sites there is a pronounced spring maximum through the troposphere. There are, however, differences in the timing and strength of this feature. Over Japan the northward movement of the jet during the spring and summer influences the timing of the seasonal maximum. The ozone profiles suggest that transport of ozone rich air from the stratosphere plays a strong role in the development of this maximum. During March and April at Hong Kong ozone is enhanced in a layer that extends from the lower free troposphere into the upper troposphere that likely has its origin in biomass burning in northern Southeast Asia and equatorial Africa. During the winter the Pacific subtropical sites (latitude -25N) are dominated by air with a low-latitude, marine source that gives low ozone amounts particularly in the upper troposphere. In the summer in the boundary layer at all of the sites marine air dominates and ozone amounts are generally quite low (less than 25 ppb). The exception is near large population centers (Tokyo and Taipei but not Hong Kong) where pollution events can give amounts in excess of 80 ppb. During the TRACE-P intensive campaign period (February-April 2001) tropospheric ozone amounts were rather typical of those seen in the long-term records of the stations with multi-year soundings.

  2. A Bayesian approach to constrain the time evolution of tropospheric parameters in GNSS data processing : implications for meteorology

    Science.gov (United States)

    Nahmani, S.; Rebischung, P.; Bock, O.

    2016-12-01

    The atmospheric water vapor induces a delay in the propagation time of GNSS signals when they cross the troposphere. Zenithal Wet Delays (ZWD) are thus estimated during GNSS data processing and used to retrieve Integrated Water Vapor (IWV) with a usual precision of around 1-2 kg.m-2. These GNSS-derived IWV are now routinely assimilated into numerical weather prediction models and are also used to validate satellite measurements and evaluate climate models. However, their accuracy remains to be precisely evaluated especially during intense weather events. Developing and evaluating advanced tropospheric products for monitoring severe weather events and climate is one of the main objectives of the COST Action ES1206 supported by the EU.In this study, we focus on a particular limitation of GNSS-derived IWV: in GNSS data processing, the temporal evolution of ZWD is usually modelled as a random walk (ZWD(t+dt) = ZWD(t) + ɛ(t)), where the variance of the white noise ɛ(t) is usually chosen arbitrarily, regardless of the location of the station and the local weather conditions. This approach is clearly not optimal, for instance in case of severe weather events, where an inappropriate variance choice for ɛ(t) can induce biases over 5 kg.m-2 on GNSS-derived IWV. We therefore use a Bayesian approach to determine optimal random walk variances for both ZWD and tropospheric gradients in PPP processing of GNSS data. We first present the methodology and validate it with simulated data. Then, we apply our method on real GNSS data and compare the obtained ZWD with those from a usual PPP processing. Finally, we plan to use data from microwave radiometers to get an external characterization of the temporal evolution of ZWD and to verify that the random walk variances obtained with our method adequately describe the variability of atmospheric water vapor.

  3. Delays in thick targets

    CERN Document Server

    Bennett, J R J

    2002-01-01

    The delays in the emission of radioactive particles from a thick target bombarded by high-energy protons is discussed in relation to the basic physical processes of diffusion and effusion through the target and ioniser. The delay time, relative to the decay time, is crucial to the efficiency of particle release at the exit of the ioniser. The principles of minimizing the delay times are discussed with reference to a mathematical model of the process, and some experimental examples are given.

  4. Delayed orgasm and anorgasmia.

    Science.gov (United States)

    Jenkins, Lawrence C; Mulhall, John P

    2015-11-01

    Delayed orgasm/anorgasmia defined as the persistent or recurrent difficulty, delay in, or absence of attaining orgasm after sufficient sexual stimulation, which causes personal distress. Delayed orgasm and anorgasmia are associated with significant sexual dissatisfaction. A focused medical history can shed light on the potential etiologies, which include medications, penile sensation loss, endocrinopathies, penile hyperstimulation, and psychological etiologies. Unfortunately, there are no excellent pharmacotherapies for delayed orgasm/anorgasmia, and treatment revolves largely around addressing potential causative factors and psychotherapy. Copyright © 2015 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  5. The effect of stratospheric sulfur from Mount Pinatubo on tropospheric oxidizing capacity and methane

    National Research Council Canada - National Science Library

    Banda, Narcissa|info:eu-repo/dai/nl/352222158; Krol, Maarten|info:eu-repo/dai/nl/078760410; van Noije, Twan; van Weele, Michiel; Williams, Jason E; Sager, Philippe Le; Niemeier, Ulrike; Thomason, Larry; Röckmann, Thomas|info:eu-repo/dai/nl/304838233

    2015-01-01

    .... Increased scattering and absorption of UV radiation by the enhanced stratospheric SO2 and aerosols decreased the amount of UV radiation reaching the troposphere, causing changes in tropospheric photochemistry...

  6. Solar-stratosphere-troposphere interaction as a mechanism of solar influence on climate

    Science.gov (United States)

    Ruzmaikin, A.

    2003-01-01

    We will briefly review recent studies showing that stratospheric disturbances propagate to the troposphere and that UV variability affects the atmospheric circulation in the stratosphere and troposphere in a coherent fashion. We will outline a mechanism by which solar-stratosphere-troposphere interaction may influence climate and discuss a simple model that includes the basic elements of this mechanism.

  7. Assimilating Tropospheric Airborne Meteorological Data Reporting (TAMDAR) Observations and the Relative Value of Other Observation Types

    Science.gov (United States)

    2014-08-01

    Assimilating Tropospheric Airborne Meteorological Data Reporting (TAMDAR) Observations and the Relative Value of Other Observation Types by...Army Research Laboratory Adelphi, MD 20783-1197 ARL-TR-7022 August 2014 Assimilating Tropospheric Airborne Meteorological Data...From - To) 15 August 2012–30 September 2013 4. TITLE AND SUBTITLE Assimilating Tropospheric Airborne Meteorological Data Reporting (TAMDAR

  8. American Dream Delayed

    DEFF Research Database (Denmark)

    Khorunzhina, Natalia; Miller, Robert A.

    This paper investigates the delay in homeownership and a subsequent reduction in homeownership rate observed over the past decades. We focus on the delay in giving birth to children and increased labor market participation as contributing factors to homeownership dynamics for prime-age female hou...

  9. Effect of some climatic parameters on tropospheric and total ozone ...

    Indian Academy of Sciences (India)

    Effect of some climatic parameters on tropospheric and total ozone column over Alipore (22.52°N, 88.33°E), India ... insolation obtained from Solar Geophysical Data Book and El-ñ index collected from National Climatic Data Center, US Department of Commerce, National Oceanic and Atmospheric Administration, USA.

  10. RIVM Tropospheric ozone LIDAR Measurements during TROLIX'91

    NARCIS (Netherlands)

    Apituley A

    1991-01-01

    For the intercomparison of several LIDAR systems for the vertical profiling of tropospheric ozone developed in the EUREKA/EUROTRAC subproject TESLAS a field campaign was held at the RIVM site in Bilthoven, the Netherlands, during the period from June 10 to June 28, 1991. In this report an overview

  11. Impact of global warming on the energetics of lower tropospheric ...

    Indian Academy of Sciences (India)

    Impact of global warming on the energetics of lower tropospheric ultra-long waves and the Indian summer monsoon. M D Chipade∗. , J R Kulkarni and S M Bawiskar. Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pune 411 008, India. ∗. Corresponding author. e-mail: mukundchipade@yahoo.co.in.

  12. Solitary Rossby waves in the lower tropical troposphere | Lenouo ...

    African Journals Online (AJOL)

    Weakly nonlinear approximation is used to study the theoretical comportment of large-scale disturbances around the inter-tropical mid-tropospheric jet. We show here that the Korteweg de Vries (KdV) theory is appropriated to describe the structure of the streamlines around the African easterly jet (AEJ) region.

  13. Influence of Chlorine Emissions on Ozone Levels in the Troposphere

    Science.gov (United States)

    Chlorine emissions from cooling towers are emitted mainly as hypochlous acid, not as molecular chlorine. Chlorine emissions from cooling towers in electric utilities in the U.S. are estimated to be 4,400 tons per year. Molecular chlorine increases more tropospheric ozone than hyp...

  14. Detection of iodine monoxide in the tropical free troposphere

    Science.gov (United States)

    Dix, Barbara; Baidar, Sunil; Bresch, James F.; Hall, Samuel R.; Schmidt, K. Sebastian; Wang, Siyuan; Volkamer, Rainer

    2013-01-01

    Atmospheric iodine monoxide (IO) is a radical that catalytically destroys heat trapping ozone and reacts further to form aerosols. Here, we report the detection of IO in the tropical free troposphere (FT). We present vertical profiles from airborne measurements over the Pacific Ocean that show significant IO up to 9.5 km altitude and locate, on average, two-thirds of the total column above the marine boundary layer. IO was observed in both recent deep convective outflow and aged free tropospheric air, suggesting a widespread abundance in the FT over tropical oceans. Our vertical profile measurements imply that most of the IO signal detected by satellites over tropical oceans could originate in the FT, which has implications for our understanding of iodine sources. Surprisingly, the IO concentration remains elevated in a transition layer that is decoupled from the ocean surface. This elevated concentration aloft is difficult to reconcile with our current understanding of iodine lifetimes and may indicate heterogeneous recycling of iodine from aerosols back to the gas phase. Chemical model simulations reveal that the iodine-induced ozone loss occurs mostly above the marine boundary layer (34%), in the transition layer (40%) and FT (26%) and accounts for up to 20% of the overall tropospheric ozone loss rate in the upper FT. Our results suggest that the halogen-driven ozone loss in the FT is currently underestimated. More research is needed to quantify the widespread impact that iodine species of marine origin have on free tropospheric composition, chemistry, and climate. PMID:23345444

  15. Variable influence on the equatorial troposphere associated with ...

    Indian Academy of Sciences (India)

    A cooling of the upper troposphere induces enhanced convective activity near the equatorial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial ... Institute for Meteorology, Freie Universit¨at, Berlin, Germany. ... Swedish Meteorological and Hydrological Institute, Norrkoping, Sweden.

  16. On the impact of temperature on tropospheric ozone concentration ...

    Indian Academy of Sciences (India)

    The influence of temperature on tropospheric ozone (O3)concentrations in urban and photochemically polluted areas in the greater Athens region are investigated in the present study.Hourly values of the ambient air temperature used for studying the urban heat island effect in Athens were recorded at twenty-three ...

  17. Linking Urban Air Pollution to Global Tropospheric Chemistry and Climate

    Science.gov (United States)

    Wang, Chien

    2005-01-01

    The two major tasks of this project are to study: (a) the impact of urban nonlinear chemistry on chemical budgets of key pollutants in non-urban areas; and (b) the influence of air pollution control strategies in selected metropolitan areas, particularly of emerging economies in East and South Asia, on tropospheric chemistry and hence on regional and global climate.

  18. Columnar Radio Refractivity Of The Troposphere At Ashodi And Kano

    African Journals Online (AJOL)

    Spatial-temporal, distributions of columnar radio refractive index in the troposphere of two tropical stations – Kano and Oshodi are considered. Monthly means of radio refractivity have been shown for the atmospheric columns, 0 – 3km (the lower atmosphere), 0- 10km (the first 10km column), and 3-10km (the upper ...

  19. Influence of sudden stratospheric warmings on tropospheric winds

    NARCIS (Netherlands)

    Hinssen, Y.B.L.; van Delden, A.J.; Opsteegh, T.

    2011-01-01

    The influence of changes in the zonal mean stratospheric potential vorticity, associated with sudden stratospheric warmings, on the zonal mean zonal wind in the troposphere is investigated by piecewise potential vorticity inversion. The focus is on the major sudden stratospheric warming that

  20. Upper tropospheric water vapour variability over tropical latitudes ...

    Indian Academy of Sciences (India)

    Upper tropospheric water vapour variability over tropical latitudes observed using radiosonde and satellite measurements. Ghouse Basha1, M Venkat Ratnam1,∗ and B V Krishna Murthy2. 1National Atmospheric Research Laboratory (NARL), Department of Space, Government of India,. Gadanki, PB No. 123, Tirupati 517 ...

  1. Internal variability in simulated and observed tropical tropospheric temperature trends

    Science.gov (United States)

    Suárez-Gutiérrez, Laura; Li, Chao; Thorne, Peter W.; Marotzke, Jochem

    2017-06-01

    We explore the extent to which internal variability can reconcile discrepancies between observed and simulated warming in the upper tropical troposphere. We compare all extant radiosonde-based estimates for the period 1958-2014 to simulations from the Coupled Model Intercomparison Project phase 5 multimodel ensemble and the 100 realization Max Planck Institute large ensemble. We consider annual mean temperatures and all available 30-and 15-year trends. Most observed trends fall within the ensemble spread for most of the record, and trends calculated over 15-year periods show better agreement than 30-year trends, with generally larger discrepancies for the older observational products. The simulated amplification of surface warming aloft in the troposphere is consistent with observations, and the linear correlation between surface and simultaneous tropospheric warming trends decreases with trend length. We conclude that trend differences between observations and simulations of tropical tropospheric temperatures are dominated by observational uncertainty and chaotic internal variability rather than by systematic errors in model performance.

  2. Tropospheric ozone from SCIAMACHY limb-nadir-measurements

    Energy Technology Data Exchange (ETDEWEB)

    Boetel, Stefan; Ebojie, Felix; Ladstaetter-Weissenmayer, Annette; Savigny, Christian von; Burrows, John P. [Institute of Environmental Physics, University of Bremen, Bremen (Germany)

    2011-07-01

    SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) launched in March 2002 measures sunlight, transmitted, reflected and scattered by the earth atmosphere or surface (240 nm-2380 nm). SCIAMACHY measurements yield the amounts and distribution of O{sub 3}, BrO, OClO, ClO, SO{sub 2}, H{sub 2}CO, NO{sub 2}, CO, CO{sub 2}, CH{sub 4}, H{sub 2}O, N{sub 2}O, p, T, aerosol, radiation, cloud cover and cloud top height in limb as well as nadir mode. With it's collocated limb and nadir measurements limb-nadir-matching can be used to determine tropospheric ozone columns from SCIAMACHY limb and nadir measurements. A comparison of tropospheric ozone columns determined from ozone-sonde measurements with tropospheric ozone columns determined from SCIAMACHY using limb-nadir-matching in various latitude bands. The variability of using limb-nadir-matching to determine global distributions of tropospheric ozone is investigated.

  3. Establishment of a Site-Specific Tropospheric Model Based on Ground Meteorological Parameters over the China Region

    Science.gov (United States)

    Zhou, Chongchong; Peng, Bibo; Li, Wei; Zhong, Shiming; Ou, Jikun; Chen, Runjing; Zhao, Xinglong

    2017-01-01

    China is a country of vast territory with complicated geographical environment and climate conditions. With the rapid progress of the Chinese BeiDou satellite navigation system (BDS); more accurate tropospheric models must be applied to improve the accuracy of navigation and positioning. Based on the formula of the Saastamoinen and Callahan models; this study develops two single-site tropospheric models (named SAAS_S and CH_S models) for the Chinese region using radiosonde data from 2005 to 2012. We assess the two single-site tropospheric models with radiosonde data for 2013 and zenith tropospheric delay (ZTD) data from four International GNSS Service (IGS) stations and compare them to the results of the Saastamoinen and Callahan models. The experimental results show that: the mean accuracy of the SAAS_S model (bias: 0.19 cm; RMS: 3.19 cm) at all radiosonde stations is superior to those of the Saastamoinen (bias: 0.62 cm; RMS: 3.62 cm) and CH_S (bias: −0.05 cm; RMS: 3.38 cm) models. In most Chinese regions; the RMS values of the SAAS_S and CH_S models are about 0.51~2.12 cm smaller than those of their corresponding source models. The SAAS_S model exhibits a clear improvement in the accuracy over the Saastamoinen model in low latitude regions. When the SAAS_S model is replaced by the SAAS model in the positioning of GNSS; the mean accuracy of vertical direction in the China region can be improved by 1.12~1.55 cm and the accuracy of vertical direction in low latitude areas can be improved by 1.33~7.63 cm. The residuals of the SAAS_S model are closer to a normal distribution compared to those of the Saastamoinen model. Single-site tropospheric models based on the short period of the most recent data (for example 2 years) can also achieve a satisfactory accuracy. The average performance of the SAAS_S model (bias: 0.83 cm; RMS: 3.24 cm) at four IGS stations is superior to that of the Saastamoinen (bias: −0.86 cm; RMS: 3.59 cm) and CH_S (bias: 0.45 cm; RMS: 3.38 cm

  4. Free tropospheric transport of microorganisms from Asia to North America

    Science.gov (United States)

    D. Smith,; Dan Jaffe,; Michele Birmele,; Griffin, Dale W.; Andrew Schuerger,; Hee, J.; Michael Roberts,

    2012-01-01

    Microorganisms are abundant in the troposphere and can be transported vast distances on prevailing winds. This study measures the abundance and diversity of airborne bacteria and fungi sampled at the Mt. Bachelor Observatory (located 2.7 km above sea level in North America) where incoming free tropospheric air routinely arrives from distant sources across the Pacific Ocean, including Asia. Overall deoxyribonucleic acid (DNA) concentrations for microorganisms in the free troposphere, derived from quantitative polymerase chain reaction assays, averaged 4.94 × 10(-5) ng DNA m(-3) for bacteria and 4.77 × 10(-3) ng DNA m(-3) for fungi. Aerosols occasionally corresponded with microbial abundance, most often in the springtime. Viable cells were recovered from 27.4 % of bacterial and 47.6 % of fungal samples (N = 124), with 49 different species identified by ribosomal DNA gene sequencing. The number of microbial isolates rose significantly above baseline values on 22-23 April 2011 and 13-15 May 2011. Both events were analyzed in detail, revealing distinct free tropospheric chemistries (e.g., low water vapor, high aerosols, carbon monoxide, and ozone) useful for ruling out boundary layer contamination. Kinematic back trajectory modeling suggested air from these events probably originated near China or Japan. Even after traveling for 10 days across the Pacific Ocean in the free troposphere, diverse and viable microbial populations, including presumptive plant pathogens Alternaria infectoria and Chaetomium globosum, were detected in Asian air samples. Establishing a connection between the intercontinental transport of microorganisms and specific diseases in North America will require follow-up investigations on both sides of the Pacific Ocean.

  5. Evaluating a Priori Ozone Profile Information Used in TEMPO (Tropospheric Emissions: Monitoring of Pollution) Tropospheric Ozone Retrievals

    Science.gov (United States)

    Johnson, Matthew Stephen

    2017-01-01

    A primary objective for TOLNet is the evaluation and validation of space-based tropospheric O3 retrievals from future systems such as the Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite. This study is designed to evaluate the tropopause-based O3 climatology (TB-Clim) dataset which will be used as the a priori profile information in TEMPO O3 retrievals. This study also evaluates model simulated O3 profiles, which could potentially serve as a priori O3 profile information in TEMPO retrievals, from near-real-time (NRT) data assimilation model products (NASA Global Modeling and Assimilation Office (GMAO) Goddard Earth Observing System (GEOS-5) Forward Processing (FP) and Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2)) and full chemical transport model (CTM), GEOS-Chem, simulations. The TB-Clim dataset and model products are evaluated with surface (0-2 km) and tropospheric (0-10 km) TOLNet observations to demonstrate the accuracy of the suggested a priori dataset and information which could potentially be used in TEMPO O3 algorithms. This study also presents the impact of individual a priori profile sources on the accuracy of theoretical TEMPO O3 retrievals in the troposphere and at the surface. Preliminary results indicate that while the TB-Clim climatological dataset can replicate seasonally-averaged tropospheric O3 profiles observed by TOLNet, model-simulated profiles from a full CTM (GEOS-Chem is used as a proxy for CTM O3 predictions) resulted in more accurate tropospheric and surface-level O3 retrievals from TEMPO when compared to hourly (diurnal cycle evaluation) and daily-averaged (daily variability evaluation) TOLNet observations. Furthermore, it was determined that when large daily-averaged surface O3 mixing ratios are observed (65 ppb), which are important for air quality purposes, TEMPO retrieval values at the surface display higher correlations and less bias when applying CTM a priori profile information

  6. Delay Choice vs. Delay Maintenance: Different Measures of Delayed Gratification in Capuchin Monkeys (Cebus apella)

    OpenAIRE

    Addessi, Elsa; Paglieri, Fabio; Beran, Michael J.; Evans, Theodore A.; Macchitella, Luigi; De Petrillo, Francesca; Focaroli, Valentina

    2013-01-01

    Delaying gratification involves two components: (i) delay choice (selecting a delayed reward over an immediate one), and (ii) delay maintenance (sustaining the decision to delay gratification even if the immediate reward is available during the delay). In primates, two tasks most commonly have explored these components, the Intertemporal choice task and the Accumulation task. It is unclear whether these tasks provide equivalent measures of delay of gratification. Here, we compared the perform...

  7. The Impact of Upper Tropospheric Humidity from Microwave Limb Sounder on the Midlatitude Greenhouse Effect

    Science.gov (United States)

    Hu, Hua; Liu, W. Timothy

    1998-01-01

    This paper presents an analysis of upper tropospheric humidity, as measured by the Microwave Limb Sounder, and the impact of the humidity on the greenhouse effect in the midlatitudes. Enhanced upper tropospheric humidity and an enhanced greenhouse effect occur over the storm tracks in the North Pacific and North Atlantic. In these areas, strong baroclinic activity and the large number of deep convective clouds transport more water vapor to the upper troposphere, and hence increase greenhouse trapping. The greenhouse effect increases with upper tropospheric humidity in areas with a moist upper troposphere (such as areas over storm tracks), but it is not sensitive to changes in upper tropospheric humidity in regions with a dry upper troposphere, clearly demonstrating that there are different mechanisms controlling the geographical distribution of the greenhouse effect in the midlatitudes.

  8. Delayed Puberty (For Teens)

    Science.gov (United States)

    ... developed later than usual, too. This is called constitutional delay (or being a late bloomer), and it ... eventually — and even when you believe they're right — it's difficult to wait for something that can ...

  9. Delayed Sequence Intubation

    DEFF Research Database (Denmark)

    Weingart, Scott D; Trueger, N Seth; Wong, Nelson

    2015-01-01

    , patients were paralyzed and intubated. The primary outcome of this study was the difference in oxygen saturations after maximal attempts at preoxygenation before delayed sequence intubation compared with saturations just before intubation. Predetermined secondary outcomes and complications were also...... assessed. RESULTS: A total of 62 patients were enrolled: 19 patients required delayed sequence intubation to allow nonrebreather mask, 39 patients required it to allow NIPPV, and 4 patients required it for nasogastric tube placement. Saturations increased from a mean of 89.9% before delayed sequence...... intubation to 98.8% afterward, with an increase of 8.9% (95% confidence interval 6.4% to 10.9%). Thirty-two patients were in a predetermined group with high potential for critical desaturation (pre-delayed sequence intubation saturations ≤93%). All of these patients increased their saturations post...

  10. Delayed puberty in boys

    Science.gov (United States)

    ... Allan CA, McLachlan RI. Androgen deficiency disorders. In: Jameson JL, De Groot LJ, de Kretser DM, et ... 350. Haddad NG, Eugster EA. Delayed puberty. In: Jameson JL, De Groot LJ, de Kretser DM, et ...

  11. Impacts of stratospheric sulfate geoengineering on tropospheric ozone

    Science.gov (United States)

    Xia, Lili; Nowack, Peer J.; Tilmes, Simone; Robock, Alan

    2017-10-01

    A range of solar radiation management (SRM) techniques has been proposed to counter anthropogenic climate change. Here, we examine the potential effects of stratospheric sulfate aerosols and solar insolation reduction on tropospheric ozone and ozone at Earth's surface. Ozone is a key air pollutant, which can produce respiratory diseases and crop damage. Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario. This allows us to compare the impacts of sulfate aerosols and solar dimming on atmospheric ozone concentrations. Despite nearly identical global mean surface temperatures for the two SRM approaches, solar insolation reduction increases global average surface ozone concentrations, while sulfate injection decreases it. A fundamental difference between the two geoengineering schemes is the importance of heterogeneous reactions in the photochemical ozone balance with larger stratospheric sulfate abundance, resulting in increased ozone depletion in mid- and high latitudes. This reduces the net transport of stratospheric ozone into the troposphere and thus is a key driver of the overall decrease in surface ozone. At the same time, the change in stratospheric ozone alters the tropospheric photochemical environment due to enhanced ultraviolet radiation. A shared factor among both SRM scenarios is decreased chemical ozone loss due to reduced tropospheric humidity. Under insolation reduction, this is the dominant factor giving rise to the global surface ozone increase. Regionally, both surface ozone increases and decreases are found for both scenarios; that is, SRM would affect regions of the world differently in terms of air pollution. In conclusion

  12. Impacts of stratospheric sulfate geoengineering on tropospheric ozone

    Directory of Open Access Journals (Sweden)

    L. Xia

    2017-10-01

    Full Text Available A range of solar radiation management (SRM techniques has been proposed to counter anthropogenic climate change. Here, we examine the potential effects of stratospheric sulfate aerosols and solar insolation reduction on tropospheric ozone and ozone at Earth's surface. Ozone is a key air pollutant, which can produce respiratory diseases and crop damage. Using a version of the Community Earth System Model from the National Center for Atmospheric Research that includes comprehensive tropospheric and stratospheric chemistry, we model both stratospheric sulfur injection and solar irradiance reduction schemes, with the aim of achieving equal levels of surface cooling relative to the Representative Concentration Pathway 6.0 scenario. This allows us to compare the impacts of sulfate aerosols and solar dimming on atmospheric ozone concentrations. Despite nearly identical global mean surface temperatures for the two SRM approaches, solar insolation reduction increases global average surface ozone concentrations, while sulfate injection decreases it. A fundamental difference between the two geoengineering schemes is the importance of heterogeneous reactions in the photochemical ozone balance with larger stratospheric sulfate abundance, resulting in increased ozone depletion in mid- and high latitudes. This reduces the net transport of stratospheric ozone into the troposphere and thus is a key driver of the overall decrease in surface ozone. At the same time, the change in stratospheric ozone alters the tropospheric photochemical environment due to enhanced ultraviolet radiation. A shared factor among both SRM scenarios is decreased chemical ozone loss due to reduced tropospheric humidity. Under insolation reduction, this is the dominant factor giving rise to the global surface ozone increase. Regionally, both surface ozone increases and decreases are found for both scenarios; that is, SRM would affect regions of the world differently in terms of air

  13. Hydroxyl radical reactions with volatile organic compounds under simulated tropospheric conditions: tropospheric lifetimes

    Energy Technology Data Exchange (ETDEWEB)

    Semadeni, M.

    1994-01-01

    Kinetic investigations of the hydroxyl radical reaction with volatile organic compounds (VOC) are important to estimate the potential of VOCs in air pollution. The temperature dependence of the rate coefficients of the hydroxyl radical reaction with members of two classes of organic compounds have been measured under simulated tropospheric conditions using a competitive technique rebuilt in this laboratory. A thermostat flow reactor was employed, which was specially constructed to investigate gas-phase reactions under atmospheric pressure. The hydroxyl radical reactions of the organic test compounds have been measured in the presence of given reference compounds over the temperature range (273-373) K using GC/FID. The rate coefficients obtained in the present study range from 11-42x10[sup -12] cm[sup 3] molecule[sup -1] s[sup -1] and from 1-52x10[sup -12] cm[sup 3] molecule[sup -1] s[sup -1] for the following ethers and aromatic compounds respectively: diethyl ether, methyl n-butyl ether, ethyl n-butyl ether, di-n-butyl ether, di-n-pentyl ether and benzene, toluene, benzaldehyde, phenol, o-cresol, m-cresol, p-cresol, arranged according to their increasing reactivity within their class. The temperature dependence of the hydroxyl radical with methyl n-butyl ether, di-n-butyl ether, m-cresol, p-cresol and benzaldehyde have been determined for the first time in this study. The Arrhenius parameters obtained confirm the negative temperature dependence often observed in this type of reaction. The results of the present study show, that the experimental system employed can provide accurate kinetic data and discrepancies occurred in previous studies have been resolved. (author) figs., tabs., refs.

  14. Stratospheric-Tropospheric Interaction and the 2002 Ozone Hole

    Science.gov (United States)

    Newman, Paul A.

    2003-01-01

    The 2002 ozone hole was remarkable for its small size and early break-up. This small size resulted from a series of wave events over the course of the 2002 winter. The major event of the 2002 winter was the major warming in late September 2002. This warming resulted from an extremely strong wave event that propagated out of the troposphere, reversed the zonal mean flow, and warmed the polar vortex. This late-September event was the culmination of a series of large wave events which occurred over the course of the 2002 winter. These waves collectively warmed the vortex and decelerated the stratospheric flow. In this talk, we will trace the origin of these wave events, and we will also analyze the feedback of the large disruption of the stratospheric flow on the troposphere.

  15. Lidar Measurements of Tropospheric Ozone in the Arctic

    Directory of Open Access Journals (Sweden)

    Seabrook Jeffrey

    2016-01-01

    Full Text Available This paper reports on differential absorption lidar (DIAL measurements of tropospheric ozone in the Canadian Arctic during springtime. Measurements at Eureka Weather Station revealed that mountains have a significant effect on the vertical structure of ozone above Ellesmere Island. Ozone depletion events were observed when air that had spent significant time near to the frozen surface of the Arctic Ocean reached Eureka. This air arrived at Eureka by flowing over the surrounding mountains. Surface level ozone depletions were not observed during periods when the flow of air from over the sea ice was blocked by mountains. In the case of blocking there was an enhancement in the amount of ozone near the surface as air from the mid troposphere descended in the lee of the mountains. Three case studies will be shown in the presentation, while one is described in this paper.

  16. Spatial and temporal variability of tropospheric ozone over Europe

    Energy Technology Data Exchange (ETDEWEB)

    Scheel, H.E.; Sladkovic, R. [Fraunhofer Inst. (IFU), Garmisch-Partenkirchen (Germany); Ancellet, G. [Universite Paris 6 (France). Service d`Aeronomie du CNRS; Areskoug, H. [Air Pollution Lab., Inst. of Applied Environmental Research, Stockholm Univ. (Sweden); Beck, J.; Waal, L. de [RIVM-LLO, Bilthoven (Netherlands); Boesenberg, J.; Grabbe, G. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Muer, D. de [Meteorological Inst. of Belgium (KMI), Brussels (Belgium); Dutot, A.L.; Etienne, A.; Perros, P.; Toupance, G. [Universite Paris XII-Creteil (France). Lab. de Physico-Chimie de l`Environment; Egelov, A.H.; Granby, K. [National Environmental Research Inst., Roskilde (Denmark); Esser, P.; Roemer, M. [IMW-TNO, Delft (Netherlands); Ferenczi, Z.; Haszpra, L. [Institute for Atmospheric Physics, Budapest (Hungary); Geiss, H.; Smit, H. [Forschungszentrum Juelich (Germany). Inst. fuer Chemie und Dynamik der Geosphaere (ICG-2); Gomiscek, B. [Ljubljana Univ. (Slovenia). Faculty of Chemistry and Chemical Technology; Kezele, N.; Klasinc, L. [Institut Rudjer Boskovic, Zagreb (Croatia); Laurila, T. [Finnish Meteorological Inst., Helsinki (Finland). Dept. of Air Quality; Lindskog, A.; Mowrer, J. [Swedish Environmental Research Inst. (IVL), Goeteborg (Sweden); Nielsen, T. [Risoe National Laboratory, Roskilde (Denmark); Schmitt, R. [Meteorologie Consult GmbH, Glashuetten (Germany); Simmonds, P. [International Science Consultants, Ringwood (United Kingdom); Solberg, S. [NILU, Kjeller (Norway); Varotsos, C. [Athens Univ. (Greece); TOR Task Group 1

    1997-12-31

    The first section is concerned with the characteristics of the TOR-measurement sites and the data used. It describes the methodologies employed for the selection of data in order to obtain representative ozone concentrations with minimum bias caused by the individual location. The question of representativeness of the O{sub 3} concentrations at the TOR sites was given special attention, since it is a crucial point for all conclusions drawn from the observations. Therefore several studies were focused on this issue. The further sections of the report deal with results on the spatial and seasonal variations of ozone concentrations over Europe. Results obtained from in-situ measurements in the boundary layer/lower free troposphere and from vertical soundings in the free troposphere are regarded separately. Finally, trend estimates are presented for ozone as well as for some of its precursors. (orig./KW)

  17. GPD+ wet tropospheric corrections for eight altimetric missions for the Sea Level ECV generation

    Science.gov (United States)

    Fernandes, Joana; Lázaro, Clara; Benveniste, Jérôme

    2016-04-01

    Due to its large spatio-temporal variability, the delay induced by the water vapour and liquid water content of the atmosphere in the altimeter signal or wet tropospheric correction (WTC) is still one of the largest sources of uncertainty in satellite altimetry. In the scope of the Sea Level (SL) Climate Change Initiative (cci) project, the University of Porto (UPorto) has been developing methods to improve the WTC (Fernandes et al., 2015). Started as a coastal algorithm to remove land effects in the microwave radiometers (MWR) on board altimeter missions, the GNSS-derived Path Delay (GPD) methodology evolved to cover the open ocean, including high latitudes, correcting for invalid observations due to land, ice and rain contamination, band instrument malfunction. The most recent version of the algorithm, GPD Plus (GPD+) computes wet path delays based on: i) WTC from the on-board MWR measurements, whenever they exist and are valid; ii) new WTC values estimated through space-time objective analysis of all available data sources, whenever the previous are considered invalid. In the estimation of the new WTC values, the following data sets are used: valid measurements from the on-board MWR, water vapour products derived from a set of 17 scanning imaging radiometers (SI-MWR) on board various remote sensing satellites and tropospheric delays derived from Global Navigation Satellite Systems (GNSS) coastal and island stations. In the estimation process, WTC derived from an atmospheric model such as the European Centre for Medium-range Weather Forecasts (ECMWF) ReAnalysis (ERA) Interim or the operational (Op) model are used as first guess, which is the adopted value in the absence of measurements. The corrections are provided for all missions used to generate the SL Essential Climate Variable (ECV): TOPEX/Poseidon- T/P, Jason-1, Jason-2, ERS-1, ERS-2, Envisat, CryoSat-2 and SARAL/ALtiKa. To ensure consistency and long term stability of the WTC datasets, the radiometers used

  18. Implementation of Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    Science.gov (United States)

    Chance, K.; Liu, X.; Suleiman, R. M.; Flittner, D. E.; Al-Saadi, J. A.; Janz, S. J.

    2014-12-01

    The updated status of TEMPO, as it proceeds from formulation phase into implementation phase is presented. TEMPO, the first NASA Earth Venture Instrument, will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, reducing uncertainty in air quality predictions by 50%. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. TEMPO provides much of the atmospheric measurement capability recommended for GEO-CAPE in the 2007 National Research Council Decadal Survey, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond. GEO-CAPE is not planned for implementation this decade. However, instruments from Europe (Sentinel 4) and Asia (GEMS) will form parts of a global GEO constellation for pollution monitoring later this decade, with a major focus on intercontinental

  19. Thermal Structure of Titan's Troposphere and Middle Atmosphere

    Science.gov (United States)

    Flasar, F. M.; Achterberg, R. K.; Schinder, P. J.

    2011-01-01

    The thermal structure of Titan's atmosphere is reviewed, with particular emphasis on recent Cassini-Huygens results. Titan's has a similar troposphere-stratosphere-mesosphere pattern like Earth, but with a much more extended atmosphere, because of the weaker gravity, and also much lower temperatures, because of its greater distance from the sun. Titan's atmosphere exhibits an unusually large range in radiative relaxation times. In the troposphere, these are long compared to seasonal time scales, but in the stratosphere they are much shorter than a season. An exception is near the winter pole, where the stratospheric relaxation times at 100-170 km become comparable to the seasonal time scale; at the warm stratopause, they are comparable to a Titan day. Hence, seasonal behavior in the troposphere should be muted, but significant in the stratosphere. This is reflected in the small meridional contrast observed in temperatures in the troposphere and the large stratospheric contrasts noted above. A surprising feature of the vertical profiles of temperature is the abrupt transition between these regimes in at high northern latitudes in winter, where the temperatures in the lower stratosphere exhibit a sudden drop with increasing altitude. This could be a radiative effect, not associated with spatial variations in gaseous opacity, but rather from an optically thick condensate at thermal-infrared wavelengths. A curious aspect of Titan's middle atmosphere is that the axis of symmetry of the temperature field is tilted by several degrees relative to the rotational axis of the moon itself. Whether this is driven by solar heating or gravitational perturbations is not known. Titan's surface exhibits weak contrasts in temperature, approximately 3 K in the winter hemisphere. At low latitudes, there is evidence of a weak nocturnal boundary layer on the morning terminator, which is not radiatively controlled, but can be explained in terms of vertical mixing with a small eddy

  20. Satellite Global and Hemispheric Lower Tropospheric Temperature Annual Temperature Cycle

    Directory of Open Access Journals (Sweden)

    Michael A. Brunke

    2010-11-01

    Full Text Available Previous analyses of the Earth’s annual cycle and its trends have utilized surface temperature data sets. Here we introduce a new analysis of the global and hemispheric annual cycle using a satellite remote sensing derived data set during the period 1979–2009, as determined from the lower tropospheric (LT channel of the MSU satellite. While the surface annual cycle is tied directly to the heating and cooling of the land areas, the tropospheric annual cycle involves additionally the gain or loss of heat between the surface and atmosphere. The peak in the global tropospheric temperature in the 30 year period occurs on 10 July and the minimum on 9 February in response to the larger land mass in the Northern Hemisphere. The actual dates of the hemispheric maxima and minima are a complex function of many variables which can change from year to year thereby altering these dates.Here we examine the time of occurrence of the global and hemispheric maxima and minima lower tropospheric temperatures, the values of the annual maxima and minima, and the slopes and significance of the changes in these metrics.  The statistically significant trends are all relatively small. The values of the global annual maximum and minimum showed a small, but significant trend. Northern and Southern Hemisphere maxima and minima show a slight trend toward occurring later in the year. Most recent analyses of trends in the global annual cycle using observed surface data have indicated a trend toward earlier maxima and minima.

  1. Variations of tropospheric methane over Japan during 1988–2010

    Directory of Open Access Journals (Sweden)

    Taku Umezawa

    2014-05-01

    Full Text Available We present observations of CH4 concentrations from the lower to upper troposphere (LT and UT over Japan during 1988–2010 based on aircraft measurements from the Tohoku University (TU. The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM. Tropospheric CH4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH4 sources, while LT CH4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH4-rich air from Asian regions elevates UT CH4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH4 decreases nearly monotonically with altitude in winter–spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH4 sources in South Asia and East Asia to the summertime high CH4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH4 emission signals particularly from Asia.

  2. Summertime tropospheric ozone distributions over central and eastern Canada

    Science.gov (United States)

    Anderson, B. E.; Gregory, G. L.; Barrick, J. D.; Collins, J. E., Jr.; Sachse, G. W.; Shipham, M. C.; Hudgins, C. H.

    1994-01-01

    Ozone measurements were obtained between the surface and the 6-km altitude on aircraft flights over central and eastern Canada during the summer 1990 NASA Global Tropospheric Experiment Arctic Boundary Layer Expedition (GTE/ABLE 3B). Tropospheric O3 budgets for these regions were observed to be highly variable and significantly impacted by long-range transport and regional scale air mass modification processes. For example, integrated O3 abundance below 5-km altitude averaged 40% and 30% greater in air masses influenced by anthropogenic sources and biomass burning, respectively, than in background (polar) air. Conversely, aged air transported from subtropical areas of the Pacific at times reduced O3 abundance in this height interval by up to 20%. Though intrusion of anthropogenic air was infrequent during the experiment period, the influence of biomass-burning emissions was particularly notable as two thirds of the flights sampled air influenced by plumes from fires burning in Alaska and western Canada. The impinging pollution, both natural and anthropogenic, not only elevated O3 levels directly but also was a source of reactive nitrogen (and nonmethane hydrocarbons) which generally increases the tropospheric lifetime of O3 via moderation of photochemical destruction rates.

  3. Impact of reactive bromine chemistry in the troposphere

    Directory of Open Access Journals (Sweden)

    R. von Glasow

    2004-01-01

    Full Text Available Recently several field campaigns and satellite observations have found strong indications for the presence of bromine oxide (BrO in the free troposphere. Using a global atmospheric chemistry transport model we show that BrO mixing ratios of a few tenths to 2 pmol mol-1 lead to a reduction in the zonal mean O3 mixing ratio of up to 18% in widespread areas and regionally up to 40% compared to a model run without bromine chemistry. A lower limit approach for the marine boundary layer, that does not explicitly include the release of halogens from sea salt aerosol, shows that for dimethyl sulfide (DMS the effect is even larger, with up to 60% reduction of its tropospheric column. This is accompanied by dramatic changes in DMS oxidation pathways, reducing its cooling effect on climate. In addition there are changes in the HO2:OH ratio that also affect NOx and PAN. These results imply that potentially significant strong sinks for O3 and DMS have so far been ignored in many studies of the chemistry of the troposphere.

  4. A troposphere tomography method considering the weighting of input information

    Science.gov (United States)

    Zhao, Qingzhi; Yao, Yibin; Yao, Wanqiang

    2017-12-01

    Troposphere tomography measurement using a global navigation satellite system (GNSS) generally consists of several types of input information including the observation equation, horizontal constraint equation, vertical constraint equation, and a priori constraint equation. The reasonable weightings of input information are a prerequisite for ensuring the reliability of the adjustment of the parameters. This forms the focus of this research, which tries to determine the weightings, including the observations, for the same type of equation and the optimal weightings for different types of equations. The optimal weightings of the proposed method are realized on the basis of the stable equilibrium relationship between different types of a posteriori unit weight variances, which are capable of adaptively adjusting the weightings for different types of equations and enables the ratio between the two arbitrary a posteriori unit weight variances to tend to unity. A troposphere tomography experiment, which was used to consider these weightings, was implemented using global positioning system (GPS) data from the Hong Kong Satellite Positioning Reference Station Network (SatRef). Numerical results show the applicability and stability of the proposed method for GPS troposphere tomography assessment under different weather conditions. In addition, the root mean square (RMS) error in the water vapor density differences between tomography-radiosonde and tomography-ECMWF (European Centre for Medium-Range Weather Forecasts) are 0.91 and 1.63 g m-3, respectively, over a 21-day test.

  5. Tropospheric ozone variations in polar regions; Troposphaerische Ozonvariationen in Polarregionen

    Energy Technology Data Exchange (ETDEWEB)

    Wessel, S.

    1997-08-01

    An extensive analysis for the description of chemical and dynamical processes during tropospheric ozone minima in the Arctic and Antarctic was carried out in this work. One main task was the analysis of the source regions of tropospheric ozone destruction and the following transport of ozone depleted air masses to the measuring site. Furtheron the ozone destruction mechanism itself should be examined as well as the efficiency of heterogeneous reactions for the regeneration of non-reative bromine compounds, which seems to be necessary because bromine may be the key component in the destruction of tropospheric ozone in polar regions. (orig./KW) [Deutsch] In der vorliegenden Arbeit wurde eine umfangreiche Analyse zur Beschreibung der chemischen und dynamischen Prozesse waehrend troposphaerischer Ozonminima in der Arktis und Antarktis durchgefuehrt. Ziel war es, die Quellregion des Ozonabbaus sowie den ausloesenden ozonabbauenden Mechanismus zu benennen, die Effizienz heterogener Reaktionen zur Regenerierung nichtreaktiver Bromverbindungen waehrend des Ozonabbaus zu ermitteln und den Transport der ozonarmen Luftmassen zum Messort zu untersuchen. (orig./KW)

  6. Long-term observations of tropospheric NO2 from satellite

    Science.gov (United States)

    Richter, Andreas; Hilboll, Andreas; Noguchi, Katsuyuki; Leitao, Joana; Burrows, John P.

    Nitrogen oxides (NOx = NO + NO2 ) are key species in atmospheric chemistry. Together with volatile organic compounds they determine the amount of ozone present in the troposphere. Through the formation of nitric acid they are involved in acid rain formation and in addition they contribute to radiative forcing both directly and indirectly. As nitrogen dioxide adversely affects human health it is also regulated by environmental laws. While ground-based networks provide long-term data of surface concentrations of nitrogen oxides at high temporal resolution in many countries, truly global observations can only be performed from space. By using the Differential Optical Absorption Spectroscopy (DOAS) method on spectrally resolved UV/vis measurements of scattered sunlight, column amounts of NO2 can be determined from nadir satellite observations. With additional assumptions on stratospheric NO2 and the radiative transfer, the tropospheric NO2 amounts can be retrieved. In this work, satellite observations of NO2 from several sensors (GOME, SCIAMACHY, OMI, and GOME-2) are used to study the long-term evolution of tropospheric NO2 amounts on a global scale. A particular focus is on the comparison of results retrieved from the different sensors in times of overlapping measurements and the degree of consistency achieved in regions of both large and small pollution signals. The effects of sampling statistics, time of overpass and spatial resolution are discussed as well as the influence of clouds.

  7. The origin of Reactive Halogen Species in the Polar Troposphere

    Science.gov (United States)

    Platt, U.

    2011-12-01

    Reactive halogen species (RHS) play an important role in various parts of the troposphere e.g. in coastal regions, over salt pans, in volcanic plumes and in polar regions. Despite much progress in recent years the origin and some of the chemical interactions of reactive halogen species (RHS) in the polar troposphere are still not quantitatively understood. Among the many unanswered questions are: Why is there an Antarctic - Arctic asymmetry of reactive iodine species? What drives the autocatalytic bromine release from sea salt (the bromine explosion)? Why does the bromine explosion almost exclusively occur during springtime? What is the effect of coupling cycles involving different halogens? What is the vertical extent of the layer containing RHS? The presentation gives an overview of new ground-based field observations illustrating the above questions and providing answers to some of them. Also, recent advances in satellite observations of tropospheric BrO are discussed. In particular new insight is being gained from the synergistic use of satellite observations and ground based measurements of BrO. Also the question of a NOx - driven (rather than HOx - driven) bromine explosion is discussed.

  8. Tropospheric ozone trend over Beijing from 2002–2010: ozonesonde measurements and modeling analysis

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2012-09-01

    Full Text Available Using a combination of ozonesonde data and numerical simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS, the trend of tropospheric ozone (O3 during 2002–2010 over Beijing was investigated. Tropospheric ozone over Beijing shows a winter minimum and a broad summer maximum with a clear positive trend in the maximum summer ozone concentration over the last decade. The observed significant trend of tropospheric column ozone is mainly caused by photochemical production (3.1% yr−1 for a mean level of 52 DU. This trend is close to the significant trend of partial column ozone in the lower troposphere (0–3 km resulting from the enhanced photochemical production during summer (3.0% yr−1 for a mean level of 23 DU. Analysis of the CLaMS simulation shows that transport rather than chemistry drives most of the seasonality of tropospheric ozone. However, dynamical processes alone cannot explain the trend of tropospheric ozone in the observational data. Clearly enhanced ozone values and a negative vertical ozone gradient in the lower troposphere in the observational data emphasize the importance of photochemistry within the troposphere during spring and summer, and suggest that the photochemistry within the troposphere significantly contributes to the tropospheric ozone trend over Beijing during the last decade.

  9. On Experience in using the remote acoustic method of partial reflections in studies of the lower troposphere

    Science.gov (United States)

    Perepelkin, V. G.; Kulichkov, S. N.; Chunchuzov, I. P.; Kuznetsov, R. D.

    2011-02-01

    Using the phenomenon of the partial reflection of acoustic waves from anisotropic wind-velocity and temperature inhomogeneities in the lower troposphere is justified in determining the structure of these inhomogeneities. The data (obtained with the method of bistatic acoustic sounding) on signals reflected from stratified inhomogeneities in the lower 600-m layer of the troposphere are given. A detonation-type pulsed acoustic source was used. The methods of isolating a small (in amplitude) reflected signal against the background of noise and determining the reflecting-layer height and the partial-reflection coefficient from the measured parameters (time delay and amplitude) of a reflected signal are presented. The method of estimating the vertical gradients of the effective sound speed and the squared acoustic refractive index from the partial-reflection coefficient previously calculated is described on the basis of an Epstein transition-layer model. The indicated parameters are experimentally estimated for concrete cases of recording reflected signals. A comparison of our estimates with independent analogous data simultaneously obtained for the same parameters with monitoring instruments (a sodar and a temperature profiler) has yielded satisfactory results.

  10. Assessment of the global impact of aerosols on tropospheric oxidants

    Science.gov (United States)

    Tie, Xuexi; Madronich, Sasha; Walters, Stacy; Edwards, David P.; Ginoux, Paul; Mahowald, Natalie; Zhang, Renyi; Lou, Chao; Brasseur, Guy

    2005-02-01

    We present here a fully coupled global aerosol and chemistry model for the troposphere. The model is used to assess the interactions between aerosols and chemical oxidants in the troposphere, including (1) the conversion from gas-phase oxidants into the condensed phase during the formation of aerosols, (2) the heterogeneous reactions occurring on the surface of aerosols, and (3) the effect of aerosols on ultraviolet radiation and photolysis rates. The present study uses the global three-dimensional chemical/transport model, Model for Ozone and Related Chemical Tracers, version 2 (MOZART-2), in which aerosols are coupled with the model. The model accounts for the presence of sulfate, soot, primary organic carbon, ammonium nitrate, secondary organic carbon, sea salt, and mineral dust particles. The simulated global distributions of the aerosols are analyzed and evaluated using satellite measurements (Moderate-Resolution Imaging Spectroradiometer (MODIS)) and surface measurements. The results suggest that in northern continental regions the tropospheric aerosol loading is highest in Europe, North America, and east Asia. Sulfate, organic carbon, black carbon, and ammonium nitrate are major contributions for the high aerosol loading in these regions. Aerosol loading is also high in the Amazon and in Africa. In these areas the aerosols consist primarily of organic carbon and black carbon. Over the southern high-latitude ocean (around 60°S), high concentrations of sea-salt aerosol are predicted. The concentration of mineral dust is highest over the Sahara and, as a result of transport, spread out into adjacent regions. The model and MODIS show similar geographical distributions of aerosol particles. However, the model overestimates the sulfate and carbonaceous aerosol in the eastern United States, Europe, and east Asia. In the region where aerosol loading is high, aerosols have important impacts on tropospheric ozone and other oxidants. The model suggests that

  11. Stripe delay filters

    OpenAIRE

    Zakharov, Alexander V.; Ilchenko, Mykhailo Ye.; Trubarov, Igor V.; Pinchuk, Ludmila S.

    2016-01-01

    There are considered constructions of microsized stripe delay filters, which are realized on a basis of ceramic materials with high dielectric permittivity. Delay time of non-minimal phase filters is 7–12 ns at frequencies of 1900 MHz with relative bandwidth of 3.6–3.85%. Filters dimensions are comparable with ones used in portable communication devices. Dimensions of researched three-resonator filter at frequency of 1900 MHz are 8.4×5×2 mm with material dielectric permittivity εr = 92, and 5...

  12. Eliminating common PACU delays.

    Science.gov (United States)

    Jenkins, Jamie

    2007-01-01

    This article discusses how one hospital identified patient flow delays in its PACU By using lean methods focused on eliminating waste, the team was able to improve patient flow. Lean thinking required the team to keep issues that were important to patients at top of mind. The improvements not only saved staff time, but they also helped the department prepare for the addition of six beds by focusing on methods to eliminate delays. The team, assigned by the vice president of surgical services, included a process engineer two decision support analysts, the PACU charge nurse, the nursing manager and ad hoc department nurses. The team recommended and implemented changes to improve operational effectiveness.

  13. Tropospheric ozone trend over Beijing from 2002–2010: ozonesonde measurements and modeling analysis

    OpenAIRE

    Wang, Y.; Konopka, P.; Liu, Y.; Chen, H.; Müller, R.; F. Plöger; Riese, M.; Cai, Z.; D. Lü

    2012-01-01

    Using a combination of ozonesonde data and numerical simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS), the trend of tropospheric ozone (O3) during 2002–2010 over Beijing was investigated. Tropospheric ozone over Beijing shows a winter minimum and a broad summer maximum with a clear positive trend in the maximum summer ozone concentration over the last decade. The observed significant trend of tropospheric column ozone is mainly caused by photoche...

  14. Measurements of selected C2-C5 hydrocarbons in the troposphere - Latitudinal, vertical, and temporal variations

    Science.gov (United States)

    Singh, Hanwant B.; Viezee, William; Salas, Louis J.

    1988-01-01

    The tropospheric distribution of 1077 C2-C5 hydrocarbon samples was determined. Shipboard measurements obtained over the eastern Pacific Ocean reveal large north-to-south gradients for most nonmethane hydrocarbons (NMHCs). The results show that NMHC concentrations can decrease by a factor of two or more during the passage of cold fronts in winter and spring, and that upper tropospheric concentrations were lower than those in the lower troposphere.

  15. Delayed breast implant reconstruction

    DEFF Research Database (Denmark)

    Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne

    2012-01-01

    We evaluated the association between radiation therapy and severe capsular contracture or reoperation after 717 delayed breast implant reconstruction procedures (288 1- and 429 2-stage procedures) identified in the prospective database of the Danish Registry for Plastic Surgery of the Breast during...... reconstruction approaches other than implants should be seriously considered among women who have received radiation therapy....

  16. Permissible Delay in Payments

    Directory of Open Access Journals (Sweden)

    Yung-Fu Huang

    2007-01-01

    Full Text Available The main purpose of this paper wants to investigate the optimal retailer's lot-sizing policy with two warehouses under partially permissible delay in payments within the economic order quantity (EOQ framework. In this paper, we want to extend that fully permissible delay in payments to the supplier would offer the retailer partially permissible delay in payments. That is, the retailer must make a partial payment to the supplier when the order is received. Then the retailer must pay off the remaining balance at the end of the permissible delay period. In addition, we want to add the assumption that the retailer's storage space is limited. That is, the retailer will rent the warehouse to store these exceeding items when the order quantity is larger than retailer's storage space. Under these conditions, we model the retailer's inventory system as a cost minimization problem to determine the retailer's optimal cycle time and optimal order quantity. Three theorems are developed to efficiently determine the optimal replenishment policy for the retailer. Finally, numerical examples are given to illustrate these theorems and obtained a lot of managerial insights.

  17. Delayed visual maturation.

    OpenAIRE

    Harel, S; Holtzman, M; Feinsod, M

    1983-01-01

    Three infants, recognised as blind during the first 4 months of life, were found to be normal on neurological and ophthalmological examinations. Visual electro-diagnostic studies showed normal retinal responses, but delayed conduction velocities and impaired visually-evoked responses over the occipital cortex. After age 6 months, normal vision developed gradually and all abnormalities disappeared.

  18. Delayed visual maturation.

    Science.gov (United States)

    Harel, S; Holtzman, M; Feinsod, M

    1983-01-01

    Three infants, recognised as blind during the first 4 months of life, were found to be normal on neurological and ophthalmological examinations. Visual electro-diagnostic studies showed normal retinal responses, but delayed conduction velocities and impaired visually-evoked responses over the occipital cortex. After age 6 months, normal vision developed gradually and all abnormalities disappeared. PMID:6189454

  19. Modulation of Terrestrial Convection by Tropospheric Humidity, and Implications for Other Planets

    Science.gov (United States)

    Genio, Anthony Del

    2013-01-01

    For decades, deep cumulus convection was viewed as consisting partly of undilute plumes that do not interact with their surrounding environment in order to explain their observed tendency to reach or penetrate the tropical tropopause. This behavior was built into all cumulus parameterizations used in terrestrial global climate and numerical weather prediction models, and it still persists in some models today. In the past decade, though, some embarrassing failures of global models have come to light, notably their tendency to rain over land near noon rather than in late afternoon or evening as observed, and the absence in the models of the Madden-Julian Oscillation (MJO), the major source of intraseasonal (30-90 day) precipitation variability in the Indian Ocean, West Pacific, and surrounding continental regions. In the past decade it has become clear that an important missing component of parameterizations is strong turbulent entrainment of drier environmental air into cumulus updrafts, which reduces the buoyancy of the updrafts and thus limits their vertical development. Tropospheric humidity thus serves as a throttle on convective penetration to high altitudes and delays the convective response to large-scale destabilizing influences in the environment.

  20. Troposphere Parameters Derived from Multi-GNSS Data Processing at GFZ

    Science.gov (United States)

    Deng, Zhiguo; Uhlemann, Maik; Fritsche, Mathias; Dick, Galina; Wickert, Jens

    2015-04-01

    Usually, the processing of Global Navigation Satellite System (GNSS) observations requires a thorough consideration of atmospheric parameters for precise applications. Accordingly, GPS meteorology has become a tool which uses measurements from ground-based GPS receivers for atmospheric water vapor sounding. Zenith total delay (ZTD) products derived from GNSS complement different other meteorological observing systems. GPS-based ZTD estimates have also been assimilated into numerical weather prediction (NWP) models. In addition to GPS and GLONASS, the new and emerging satellite navigation systems BeiDou and Galileo provide the potential for extended and more precise GNSS applications. Accordingly, the International GNSS Service (IGS) has initiated the Multi-GNSS Experiment (MGEX) to acquire and analyze data from all four constellations. In view of the increased number of actively transmitting satellites, the ZTD parameter estimation will particularly benefit from an improved spatial distribution of observations tracked by the ground-based receivers. In this contribution, we report on the status of our multi-system (GPS, GLONASS, BeiDou, Galileo) data processing at GFZ. Based on data from the MGEX network we produce multi-GNSS solutions including parameter estimates for satellite orbits, clock, station coordinates and site-specific ZTDs. Our presentation focusses on the validation of ZTDs from the multi-GNSS processing and a comparison with single-system ZTD solutions and GFZ's operational near real-time troposphere products.

  1. Delayed fluorescence in photosynthesis.

    Science.gov (United States)

    Goltsev, Vasilij; Zaharieva, Ivelina; Chernev, Petko; Strasser, Reto J

    2009-01-01

    Photosynthesis is a very efficient photochemical process. Nevertheless, plants emit some of the absorbed energy as light quanta. This luminescence is emitted, predominantly, by excited chlorophyll a molecules in the light-harvesting antenna, associated with Photosystem II (PS II) reaction centers. The emission that occurs before the utilization of the excitation energy in the primary photochemical reaction is called prompt fluorescence. Light emission can also be observed from repopulated excited chlorophylls as a result of recombination of the charge pairs. In this case, some time-dependent redox reactions occur before the excitation of the chlorophyll. This delays the light emission and provides the name for this phenomenon-delayed fluorescence (DF), or delayed light emission (DLE). The DF intensity is a decreasing polyphasic function of the time after illumination, which reflects the kinetics of electron transport reactions both on the (electron) donor and the (electron) acceptor sides of PS II. Two main experimental approaches are used for DF measurements: (a) recording of the DF decay in the dark after a single turnover flash or after continuous light excitation and (b) recording of the DF intensity during light adaptation of the photosynthesizing samples (induction curves), following a period of darkness. In this paper we review historical data on DF research and recent advances in the understanding of the relation between the delayed fluorescence and specific reactions in PS II. An experimental method for simultaneous recording of the induction transients of prompt and delayed chlorophyll fluorescence and decay curves of DF in the millisecond time domain is discussed.

  2. SAFARI 2000 MOPITT Tropospheric Carbon Monoxide, Southern Africa, Dry Season 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — The MOPITT (Measurements Of Pollution In The Troposphere) instrument on the NASA Terra Satellite makes measurements of infrared radiation originating from the...

  3. SAFARI 2000 MOPITT Tropospheric Carbon Monoxide, Southern Africa, Dry Season 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The MOPITT (Measurements Of Pollution In The Troposphere) instrument on the NASA Terra Satellite makes measurements of infrared radiation originating from...

  4. Lidar Atmospheric Sensing Experiment (LASE) Data Obtained During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The Lidar Atmospheric Sensing Experiment (LASE) Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) data set was collected over the Western...

  5. Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) MODIS Airborne Simulator (MAS) Level-1B Data Products

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the Tropospheric Aerosol Radiative ForcingObservational Experiment (TARFOX) was to Determine the directradiative impact and (chemical, physical,...

  6. Seasonal and interannual variations in HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

    Science.gov (United States)

    Glatthor, N.; Höpfner, M.; Stiller, G. P.; von Clarmann, T.; Funke, B.; Lossow, S.; Eckert, E.; Grabowski, U.; Kellmann, S.; Linden, A.; Walker, K. A.; Wiegele, A.

    2015-01-01

    We present a HCN climatology of the years 2002-2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5-6 months and a stratospheric lifetime of about 2 years. The MIPAS climatology is in good agreement with the HCN distribution obtained by the spaceborne ACE-FTS experiment and with airborne in situ measurements performed during the INTEX-B campaign. The HCN amounts observed by MIPAS in the southern tropical and subtropical upper troposphere have an annual cycle peaking in October-November, i.e. 1-2 months after the maximum of southern hemispheric fire emissions. The probable reason for the time shift is the delayed onset of deep convection towards austral summer. Because of overlap of varying biomass burning emissions from South America and southern Africa with sporadically strong contributions from Indonesia, the size and strength of the southern hemispheric plume have considerable interannual variations, with monthly mean maxima at, for example, 14 km between 400 and more than 700 pptv. Within 1-2 months after appearance of the plume, a considerable portion of the enhanced HCN is transported southward to as far as Antarctic latitudes. The fundamental period of HCN variability in the northern upper troposphere is also an annual cycle with varying amplitude, which in the tropics peaks in May after and during the biomass burning seasons in northern tropical Africa and southern Asia, and in the subtropics peaks in July due to trapping of pollutants in the Asian monsoon anticyclone (AMA). However, caused by extensive biomass burning in Indonesia and by northward transport of part of the southern hemispheric plume, northern HCN maxima also occur around October/November in several years

  7. Long-term observations of tropospheric ozone: GAW Measurement Guidelines

    Science.gov (United States)

    Tarasova, Oksana; Galbally, Ian E.; Schultz, Martin G.

    2013-04-01

    The Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) coordinates long-term observations of the chemical composition and physical properties of the atmosphere which are relevant for understanding of atmospheric chemistry and climate change. Atmospheric observations of reactive gases (tropospheric ozone, carbon monoxide, volatile organic compounds and nitrogen oxides) coordinated by the GAW Programme complement local and regional scale air quality monitoring efforts. As part of the GAW quality assurance (QA) system detailed measurement guidelines for atmospheric trace species are developed by international expert teams at irregular intervals. The most recent report focuses on continuous in-situ measurements of ozone in the troposphere, performed in particular at continental or island sites with altitudes ranging from sea level to mountain tops. Data Quality Objectives (DQOs) are defined for different applications of the data (e.g. trend analysis and verification of global model forecasts). These DQOs include a thorough discussion of the tolerable level of measurement uncertainty and data completeness. The guidelines present the best practices and practical arrangements adopted by the GAW Programme in order to enable the GAW station network to approach or achieve the defined tropospheric ozone DQOs. The document includes information on the selection of station and measurement locations, required skills and training of staff, recommendations on the measurement technique and the necessary equipment to perform highest quality measurements, rules for conducting the measurements, preparing the data and archiving them, and more. Much emphasis is given to discussions about how to ensure the quality of the data through tracing calibrations back to primary standards, proper calibration and data analysis, etc. In the GAW Programme the QA system is implemented through Central Facilities (Central Calibration Laboratories, World and Regional

  8. Free-Tropospheric Moisture Convergence and Tropical Convective Regimes

    Science.gov (United States)

    Masunaga, H.

    2014-12-01

    It is known that quiescent periods with only shallow cumuli prevalent are frequently observed even in the deep Tropics, which is considered from the climatological perspectives as an area harboring vigorous deep convection. It is argued in this work that the free-tropospheric (FT) moisture convergence is a crucial factor for separating the stable maintenance of isolated shallow cumuli in the quiescent periods from the self-sustaining growth of organized convective systems in the dynamic periods over tropical oceans. The analysis is based on a variety of satellite measurements including Aqua AIRS T and q soundings and QuikSCAT surface wind, composited with reference to the time before or after the occurrence of precipitating clouds detected by TRMM PR. The FT moisture convergence and updraft moisture flux at cloud base are then derived from this dataset under large-scale moisture budget constraint (see Figure). Free-tropospheric precipitation efficiency (FTPE), or the ratio of precipitation to updraft moisture flux at cloud base, is introduced as a measure of convective intensity (rather than the population) over the large-scale domain. The following hypothesis is discussed in light of the analysis results. Isolated shallow cumuli would stay shallow when large-scale FT moisture is diverging (although moisture is weakly converging when integrated over the whole troposphere) since an increase in cumulus population would be counteracted by an additional moisture divergence in the FT. When large-scale FT convergence is positive, in contrast, developing clouds would induce a more moisture input and allow an unstable growth to a highly organized convective system. Zero FT moisture convergence may serve as the neutrality separating the negative feedback acting in the quiescent regime from the positive feedback instrumental for the dynamic regime.

  9. On tropospheric adjustment to forcing and climate feedbacks

    Energy Technology Data Exchange (ETDEWEB)

    Colman, R.A.; McAvaney, B.J. [Bureau of Meteorology, Centre for Australian Weather and Climate Research, GPO Box 1289, Melbourne, VIC (Australia)

    2011-05-15

    Motivated by findings that major components of so-called cloud 'feedbacks' are best understood as rapid responses to CO{sub 2} forcing (Gregory and Webb in J Clim 21:58-71, 2008), the top of atmosphere (TOA) radiative effects from forcing, and the subsequent responses to global surface temperature changes from all 'atmospheric feedbacks' (water vapour, lapse rate, surface albedo, 'surface temperature' and cloud) are examined in detail in a General Circulation Model. Two approaches are used: applying regressions to experiments as they approach equilibrium, and equilibrium experiments forced separately by CO{sub 2} and patterned sea surface temperature perturbations alone. Results are analysed using the partial radiative perturbation ('PRP') technique. In common with Gregory and Webb (J Clim 21:58-71, 2008) a strong positive addition to 'forcing' is found in the short wave (SW) from clouds. There is little evidence, however, of significant global scale rapid responses from long wave (LW) cloud, nor from surface albedo, SW water vapour or 'surface temperature'. These responses may be well understood to first order as classical 'feedbacks' - i.e. as a function of global mean temperature alone and linearly related to it. Linear regression provides some evidence of a small rapid negative response in the LW from water vapour, related largely to decreased relative humidity (RH), but the response here, too, is dwarfed by subsequent response to warming. The large rapid SW cloud response is related to cloud fraction changes - and not optical properties - resulting from small cloud decreases ranging from the tropical mid troposphere to the mid latitude lower troposphere, in turn associated with decreased lower tropospheric RH. These regions correspond with levels of enhanced heating rates and increased temperatures from the CO{sub 2} increase. The pattern of SW cloud fraction response to SST changes differs

  10. Tropospheric haze and colors of the clear daytime sky.

    Science.gov (United States)

    Lee, Raymond L

    2015-02-01

    To casual observers, haze's visible effects on clear daytime skies may seem mundane: significant scattering by tropospheric aerosols visibly (1) reduces the luminance contrast of distant objects and (2) desaturates sky blueness. However, few published measurements of hazy-sky spectra and chromaticities exist to compare with these naked-eye observations. Hyperspectral imaging along sky meridians of clear and hazy skies at one inland and two coastal sites shows that they have characteristic colorimetric signatures of scattering and absorption by haze aerosols. In addition, a simple spectral transfer function and a second-order scattering model of skylight reveal the net spectral and colorimetric effects of haze.

  11. Direct Measurements of the Convective Recycling of the Upper Troposphere

    Science.gov (United States)

    Bertram, Timothy H.; Perring, Anne E.; Wooldridge, Paul J.; Crounse, John D.; Kwan, Alan J.; Wennberg, Paul O.; Scheuer, Eric; Dibb, Jack; Avery, Melody; Sachse, Glen; hide

    2007-01-01

    We present a statistical representation of the aggregate effects of deep convection on the chemistry and dynamics of the Upper Troposphere (UT) based on direct aircraft observations of the chemical composition of the UT over the Eastern United States and Canada during summer. These measurements provide new and unique observational constraints on the chemistry occurring downwind of convection and the rate at which air in the UT is recycled, previously only the province of model analyses. These results provide quantitative measures that can be used to evaluate global climate and chemistry models.

  12. Delayed crosslinker composition

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, R.M.

    1989-01-10

    A crosslinker composition is described that can produce delayed crosslinking of an aqueous solution of a crosslinkable organic polymer. It consists of about 1% to about 10% by weight of an organic zirconium complex and about 2% to about 37% by weight organic hydroxycarboxylic acid selected from the group consisting of lactic, mandelic and hydroxyacetic acids the pH of the composition being no greater than 4.8.

  13. Delayed visual maturation.

    OpenAIRE

    Cole, G F; Hungerford, J.; Jones, R B

    1984-01-01

    Sixteen blind babies who were considered to be showing the characteristics of delayed visual maturation were studied prospectively. The diagnosis was made on clinical grounds, and the criteria for this are discussed. All of these infants developed visual responses between 4 and 6 months of age and had normal or near normal visual acuities by 1 year of age. Long term follow up, however, has shown neurological abnormalities in some of these children.

  14. Delayed visual maturation.

    Science.gov (United States)

    Fielder, A R; Russell-Eggitt, I R; Dodd, K L; Mellor, D H

    1985-01-01

    Fifty-three infants with delayed visual maturation (DVM) are presented. These have been classified according to their ocular and systemic features into three groups: DVM as an isolated anomaly, in association with mental retardation, and ocular abnormalities accompanied by DVM. The clinical features are discussed, particularly regarding the time and speed of visual improvement in the three groups. Infants with DVM who experienced difficulties in the perinatal period have an increased risk of developing permanent neurological sequelae.

  15. Delayed breast implant reconstruction

    DEFF Research Database (Denmark)

    Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne

    2011-01-01

    Studies of complications following reconstructive surgery with implants among women with breast cancer are needed. As the, to our knowledge, first prospective long-term study we evaluated the occurrence of complications following delayed breast reconstruction separately for one- and two-stage pro......Studies of complications following reconstructive surgery with implants among women with breast cancer are needed. As the, to our knowledge, first prospective long-term study we evaluated the occurrence of complications following delayed breast reconstruction separately for one- and two......-stage procedures. From the Danish Registry for Plastic Surgery of the Breast, which has prospectively registered data for women undergoing breast implantations since 1999, we identified 559 women without a history of radiation therapy undergoing 592 delayed breast reconstructions following breast cancer during...... the period 1999 to 2006; 239 one-stage procedures and 353 two-stage procedures. The postoperative course through November 2009 was evaluated by cumulative incidence adjusting for competing risks for the selected outcomes; hematoma, infection, seroma, implant rupture, severe capsular contracture (modified...

  16. Delay in atomic photoionization

    CERN Document Server

    Kheifets, A S

    2010-01-01

    We analyze the time delay between emission of photoelectrons from the outer valence $ns$ and $np$ sub-shells in noble gas atoms following absorption of an attosecond XUV pulse. By solving the time dependent Schr\\"odinger equation and carefully examining the time evolution of the photoelectron wave packet, we establish the apparent "time zero" when the photoelectron leaves the atom. Various processes such as elastic scattering of the photoelectron on the parent ion and many-electron correlation affect the quantum phase of the dipole transition matrix element, the energy dependence of which defines the emission timing. This qualitatively explains the time delay between photoemission from the $2s$ and $2p$ sub-shells of Ne as determined experimentally by attosecond streaking [{\\em Science} {\\bf 328}, 1658 (2010)]. However, with our extensive numerical modeling, we were only able to account for less than a half of the measured time delay of $21\\pm5$~as. We argue that the XUV pulse alone cannot produce such a larg...

  17. Time-Delay Interferometry

    Directory of Open Access Journals (Sweden)

    Massimo Tinto

    2014-08-01

    Full Text Available Equal-arm detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set the overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers, the laser noise experiences different delays in the two arms and will hence not directly cancel at the detector. In order to solve this problem, a technique involving heterodyne interferometry with unequal arm lengths and independent phase-difference readouts has been proposed. It relies on properly time-shifting and linearly combining independent Doppler measurements, and for this reason it has been called time-delay interferometry (TDI. This article provides an overview of the theory, mathematical foundations, and experimental aspects associated with the implementation of TDI. Although emphasis on the application of TDI to the Laser Interferometer Space Antenna (LISA mission appears throughout this article, TDI can be incorporated into the design of any future space-based mission aiming to search for gravitational waves via interferometric measurements. We have purposely left out all theoretical aspects that data analysts will need to account for when analyzing the TDI data combinations.

  18. Climate change, tropospheric ozone and particulate matter, and health impacts.

    Science.gov (United States)

    Ebi, Kristie L; McGregor, Glenn

    2008-11-01

    Because the state of the atmosphere determines the development, transport, dispersion, and deposition of air pollutants, there is concern that climate change could affect morbidity and mortality associated with elevated concentrations of these gases and fine particles. We review how climate change could affect future concentrations of tropospheric ozone and particulate matter (PM), and what changing concentrations could mean for population health. We review studies projecting the impacts of climate change on air quality and studies projecting the impacts of these changes on morbidity and mortality. Climate change could affect local to regional air quality through changes in chemical reaction rates, boundary layer heights that affect vertical mixing of pollutants, and changes in synoptic airflow patterns that govern pollutant transport. Sources of uncertainty include the degree of future climate change, future emissions of air pollutants and their precursors, and how population vulnerability may change in the future. Given these uncertainties, projections suggest that climate change will increase concentrations of tropospheric ozone, at least in high-income countries when precursor emissions are held constant, which would increase morbidity and mortality. Few projections are available for low- and middle-income countries. The evidence is less robust for PM, primarily because few studies have been conducted. Additional research is needed to better understand the possible impacts of climate change on air pollution-related health impacts. If improved models continue to project higher ozone concentrations with climate change, then reducing greenhouse gas emissions would enhance the health of current and future generations.

  19. Characterising the Venezuelan Troposphere for Radio-Astronomy Studies

    Science.gov (United States)

    Pacheco, R.; Muñoz, A. G.; Brito, A.; Cubillán, N.

    2009-05-01

    Venezuela possesses a very useful geographical location for doing Radioastronomy. Recently, the Venezuelan Government (via FIDETEL-Ministerio de Ciencia y Tecnología) has aproved to the Laboratorio de Astronomía y Física Teórica (LAFT) of La Universidad del Zulia (Venezuela) the adquisition of four 3 meter diameter parabolic dishes that will be set as a radio-interferometer receiver and that can be used for certain Radioastronomy purposes. The specifications of the instrument will be treated elsewhere (Muñoz and Hernández 2007). To this aim, as ussually, the first step is to characterize the losses due to the atmosphere, and their evolution over time. In previous works (Muñoz et al. 2004, Memoires of V RIAO/VIII OPTILAS, M10-5 Modelling Tropospheric Radio-Attenuation Parameters for Venezuela, 359; Muñoz et al. 2006, CIENCIA, Vol. 14, 4, 428) we have studied some relevant electromagnetic (e-m) attenuation parameters dueto hydrometeors and absortion gases in the lower atmosphere, focused in local telecommunication applications (surface e-m trajectories). In this work we extend our results to include the cenital and quasi-cenital e-m trajectories, characterizing thus the medium losses in the 0.4-4.0 GHz spectral window for several Venezuelan locations. We report refractivity values and their gradients, tropospheric indexes, extinction coefficients and the total rain attenuation for the whole territory under study.

  20. Tropospheric Degradation of Perfluorinated Aromatics: A Case of Hexafluorobenzene

    Directory of Open Access Journals (Sweden)

    Goran Kovačević

    2015-12-01

    Full Text Available The major tropospheric removal process for hexafluorobenzene is its oxidation by hydroxyl (OH radicals. However, there is no information on the reaction mechanism of this important process. All geometries and energies significant for the tropospheric degradation of hexafluorobenzene were characterized using the MP2/6-311+G(d,p and/or G3 methods. It was found out that the addition of OH radical to hexafluorobenzene proceeds via a prereaction complex. In the prereaction complex the OH radical is almost perpendicular to the aromatic ring and oxygen is pointing to its center. The reaction rate constants for addition of OH radical to hexafluorobenzene were determined for the temperature range 230–330 K, using RRKM theory and corrected G3 energies. For the whole range of environmentally relevant temperatures (230–330 K there is a very good qualitative agreement between the calculated and experimental rate constants. Finally, our results almost perfectly reproduce the unusually weak temperature dependence for OH radical addition to hexafluorobenzene.

  1. Infrasound propagation in tropospheric ducts and acoustic shadow zones.

    Science.gov (United States)

    de Groot-Hedlin, Catherine D

    2017-10-01

    Numerical computations of the Navier-Stokes equations governing acoustic propagation are performed to investigate infrasound propagation in the troposphere and into acoustic shadow zones. An existing nonlinear finite-difference, time-domain (FDTD) solver that constrains input sound speed models to be axisymmetric is expanded to allow for advection and rigid, stair-step topography. The FDTD solver permits realistic computations along a given azimuth. It is applied to several environmental models to examine the effects of nonlinearity, topography, advection, and two-dimensional (2D) variations in wind and sound speeds on the penetration of infrasound into shadow zones. Synthesized waveforms are compared to a recording of a rocket motor fuel elimination event at the Utah Test and Training Range. Results show good agreement in the amplitude, duration, and spectra of synthesized and recorded waveforms for propagation through 2D atmospheric models whether or not topography, advection, or nonlinearity is explicitly included. However, infrasound propagation through a one-dimensional, range-averaged, atmospheric model yields waveforms with lower amplitudes and frequencies, suggesting that small-scale atmospheric variability causes significant scatter within the troposphere, leading to enhanced infrasound penetration into shadow zones. Thus, unresolved fine-scale atmospheric dynamics are not required to explain infrasound propagation into shadow zones.

  2. Technical Note: Using DEG CPCs at upper tropospheric temperatures

    CERN Document Server

    Wimmer, D; Nieminen, T; Duplissy, J; Ehrhart, S; Almeida, J; Rondo, L; Franchin, A; Kreissl, F; Manninen, H E; Kulmala, M; Curtius, J; Petäjä, T

    2014-01-01

    Over the last few years, several Condensation Particle Counters (CPC) capable of measuring in the sub-3 nm size range have been developed. Here we study the performance of Diethylene glycol (DEG) based CPCs at different temperatures during Cosmics Leaving Outdoor Droplets (CLOUD) measurements at CERN. The data shown here is the first set of verification measurements for sub-3 nm CPCs under upper tropospheric temperatures using atmospherically relevant aerosol particles. To put the results in perspective we calibrated the DEG-CPC at room temperature, resulting in a cut-off diameter of 1.4 nm. All diameters refer to mobility equivalent diameters in this manuscript. At upper tropospheric temperatures between −25 °C and −65 °C, we found cut-off sizes in the range of 2.5 and 2.8 nm. Due to low number concentration after size classification, the cut-off diameters have a high uncertainty (±0.3 nm) associated with them. Operating two laminar flow DEG CPCs with different cut-off sizes together with other aeroso...

  3. Simplified Modeling of Tropospheric Ozone Formation Considering Alternative Fuels Using

    Directory of Open Access Journals (Sweden)

    Leonardo Aragão Ferreira da Silva

    2014-07-01

    Full Text Available Brazilian cities have been constantly exposed to air quality episodes of high ozone concentrations (O3 . Known for not be emitted directly into the environment, O3 is a result of several chemical reactions of other pollutants emitted to atmosphere. The growth of vehicle fleet and government incentives for using alternative fuels like ethanol and Compressed Natural Gas (CNG are changing the Brazilian Metropolitan Areas in terms of acetaldehyde and formaldehyde emissions, Volatile Organic Compounds (VOC's present in the atmosphere and known to act on the kinetics of ozone. Driven by high concentrations of tropospheric ozone in urban/industry centers and its implications for environment and population health, the target of this work is understand the kinetics of ozone formation through the creation of a mathematical model in FORTRAN 90, describing a system of coupled ordinary differential equations able to represent a simplified mechanism of photochemical reactions in the Brazilian Metropolitan Area. Evaluating the concentration results of each pollutant were possible to observe the precursor’s influence on tropospheric ozone formation, which seasons were more conducive to this one and which are the influences of weather conditions on formation of photochemical smog.

  4. Evidence of Tropospheric 90 Day Oscillations in the Thermosphere

    Science.gov (United States)

    Gasperini, F.; Hagan, M. E.; Zhao, Y.

    2017-10-01

    In the last decade evidence demonstrated that terrestrial weather greatly impacts the dynamics and mean state of the thermosphere via small-scale gravity waves and global-scale solar tidal propagation and dissipation effects. While observations have shown significant intraseasonal variability in the upper mesospheric mean winds, relatively little is known about this variability at satellite altitudes (˜250-400 km). Using cross-track wind measurements from the Challenging Minisatellite Payload and Gravity field and steady-state Ocean Circulation Explorer satellites, winds from a Modern-Era Retrospective Analysis for Research and Applications/Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model simulation, and outgoing longwave radiation data, we demonstrate the existence of a prominent and global-scale 90 day oscillation in the thermospheric zonal mean winds and in the diurnal eastward propagating tide with zonal wave number 3 (DE3) during 2009-2010 and present evidence of its connection to variability in tropospheric convective activity. This study suggests that strong coupling between the troposphere and the thermosphere occurs on intraseasonal timescales.

  5. Photooxidants in the marine Arctic troposphere in summer

    Science.gov (United States)

    Weller, R.; Schrems, O.

    1996-04-01

    The air chemistry investigations, performed on R/V Polarstern during the expedition ARK X/1 in July/August 1994, comprised a mapping of the vertical ozone distribution by ozone soundings and the surface mixing ratios of H2O2 and NO above the East Greenland Sea between 70°N and 80°N. The observed H2O2 mixing ratios varied from about 100 parts per trillion by volume (pptv) up to around 1000 pptv. Surface ozone concentrations can be correlated with the source region of the advected air masses. Ozone mixing ratios from around 33 parts per billion by volume (ppbv) up to 60 ppbv have been observed in air parcels emanating from industrialized regions. In contrast, pristine Arctic air masses showed low ozone mixing ratios of about 23 ppbv. The tropospheric part of the vertical ozone profiles occasionally exhibited significant maxima above the planetary boundary layer. Apart from cases where intrusions of stratospheric ozone were obvious, photochemical ozone formation along trajectories originating from polluted regions was most probably the reason for layers with enhanced ozone concentrations. The measured surface NO mixing ratios were extremely low, typically between 3 and 8 pptv. Thus local photochemical surface ozone production could be largely ruled out. In conclusion it can be stated that in summer, intrusion of ozone rich stratospheric air and advection of polluted air masses from lower latitudes appeared to be the dominant ozone sources of the marine Arctic troposphere.

  6. Mie lidar observations of lower tropospheric aerosols and clouds.

    Science.gov (United States)

    Veerabuthiran, S; Razdan, A K; Jindal, M K; Dubey, D K; Sharma, R C

    2011-12-15

    Mie lidar system is developed at Laser Science and Technology Centre, Delhi (28.38°N, 77.12°E) by using minimal number of commercially available off-the-shelf components. Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser operating at 1064nm with variable pulse energies between 25 and 400 mJ with 10 Hz repetition rate and 7ns pulse duration is used as a transmitter and off-axis CASSEGRAIN telescope with 100mm diameter as a receiver. Silicon avalanche photodiode (Si-APD) module with built-in preamplifier and front-end optics is used as detector. This system has been developed for the studies of lower tropospheric aerosols and clouds. Some experiments have been conducted using this set up and preliminary results are discussed. The characteristics of backscattered signals for various transmitter pulse energies are also studied. Atmospheric aerosol extinction coefficient values are calculated using Klett lidar inversion algorithm. The extinction coefficient, in general, falls with range in the lower troposphere and the values lie typically in the range 7.5×10(-5) m(-1) to 1.12×10(-4) m(-1) in the absence of any cloud whereas this value shoots maximum up to 1.267×10(-3) m(-1) (peak extinction) in the presence of clouds. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Current Vaccine Shortages and Delays

    Science.gov (United States)

    ... value="Submit" /> Related Links Vaccines & Immunizations Current Vaccine Shortages & Delays Recommend on Facebook Tweet Share Compartir ... vaccination are included in this update. Chart of Vaccines* in Delay or Shortage National Vaccine Supply Shortages ...

  8. A model study of ozone in the eastern Mediterranean free troposphere during MINOS (August 2001)

    NARCIS (Netherlands)

    Roelofs, GJ; Scheeren, HA; Heland, J; Ziereis, H; Lelieveld, J

    2003-01-01

    A coupled tropospheric chemistry-climate model is used to analyze tropospheric ozone distributions observed during the MINOS campaign in the eastern Mediterranean region ( August, 2001). Modeled ozone profiles are generally in good agreement with the observations. Our analysis shows that the

  9. Detection of lightning-produced NO in the midlatitude upper troposphere during STREAM 1998

    NARCIS (Netherlands)

    Lange, L; Hoor, P; Helas, G; Fischer, H; Brunner, D; Scheeren, B; Williams, J; Wong, S; Wohlfrorn, KH; Arnold, F; Strom, J; Krejci, R; Lelieveld, J; Andreae, Meinrat O.

    2001-01-01

    Simultaneous in situ measurements of NO, NOy, HNO3, CO, CO2, O-3, and aerosols were performed in the midlatitude upper troposphere (UT) and lower stratosphere during the Stratosphere-Troposphere Experiment by Aircraft Measurements (STREAM) 1998 summer campaign. The campaign focused on the region

  10. Adaptive radiointerferometer with microprocessor of a signal in the mobile station of a troposphere communication

    OpenAIRE

    Rudakov, V. I.

    2009-01-01

    In the presentation is decides scientific problem of the application of adaptive radiointerferometer in the mobile station of a troposphere communication by modern realization of digital regimes for two-contours processing of troposphere signals, which is allow to increase signals stability and information reliability of the mobile station.

  11. Science Accomplishments from a Decade of Aura OMI/MLS Tropospheric Ozone Measurements

    Science.gov (United States)

    Ziemke, Jerald R.; Douglass, Anne R.; Joiner, Joanna; Duncan, Bryan N.; Olsen, Mark A.; Oman, Luke D.; Witte, Jacquelyn C.; Liu, X.; Wargan, K.; Schoeberl, Mark R.; hide

    2014-01-01

    Measurements of tropospheric ozone from combined Aura OMI and MLS instruments have yielded a large number of new and important science discoveries over the last decade. These discoveries have generated a much greater understanding of biomass burning, lightning NO, and stratosphere-troposphere exchange sources of tropospheric ozone, ENSO dynamics and photochemistry, intra-seasonal variability-Madden-Julian Oscillation including convective transport, radiative forcing, measuring ozone pollution from space, improvements to ozone retrieval algorithms, and evaluation of chemical-transport and chemistry-climate models. The OMI-MLS measurements have been instrumental in giving us better understanding of the dynamics and chemistry involving tropospheric ozone and the many drivers affecting the troposphere in general. This discussion will provide an overview focusing on our main science results.

  12. Delay Choice vs. Delay Maintenance: Different Measures of Delayed Gratification in Capuchin Monkeys (Cebus apella)

    Science.gov (United States)

    Addessi, Elsa; Paglieri, Fabio; Beran, Michael J.; Evans, Theodore A.; Macchitella, Luigi; De Petrillo, Francesca; Focaroli, Valentina

    2013-01-01

    Delaying gratification involves two components: (i) delay choice (selecting a delayed reward over an immediate one), and (ii) delay maintenance (sustaining the decision to delay gratification even if the immediate reward is available during the delay). In primates, two tasks most commonly have explored these components, the Intertemporal choice task and the Accumulation task. It is unclear whether these tasks provide equivalent measures of delay of gratification. Here, we compared the performance of the same capuchin monkeys, belonging to two study populations, between these tasks. We found only limited evidence of a significant correlation in performance. Consequently, in contrast to what is often assumed, our data provide only partial support to the hypothesis that these tasks provide equivalent measures of delay of gratification. PMID:23544770

  13. Delay choice versus delay maintenance: different measures of delayed gratification in capuchin monkeys (Cebus apella).

    Science.gov (United States)

    Addessi, Elsa; Paglieri, Fabio; Beran, Michael J; Evans, Theodore A; Macchitella, Luigi; De Petrillo, Francesca; Focaroli, Valentina

    2013-11-01

    Delaying gratification involves 2 components: (1) delay choice (selecting a delayed reward over an immediate one) and (2) delay maintenance (sustaining the decision to delay gratification even if the immediate reward is available during the delay). Two tasks most commonly have explored these components in primates: the intertemporal choice task and the accumulation task. It is unclear whether these tasks provide equivalent measures of delay of gratification. Here, we compared the performance on the intertemporal choice task and the accumulation task of capuchin monkeys (Cebus apella) belonging to 2 study populations. We found only limited evidence of a significant correlation in performance. Consequently, in contrast to what is often assumed, our data provide only partial support for the hypothesis that these tasks provide equivalent measures of delay of gratification.

  14. Delaying information search

    Directory of Open Access Journals (Sweden)

    Yaniv Shani

    2012-11-01

    Full Text Available In three studies, we examined factors that may temporarily attenuate information search. People are generally curious and dislike uncertainty, which typically encourages them to look for relevant information. Despite these strong forces that promote information search, people sometimes deliberately delay obtaining valuable information. We find they may do so when they are concerned that the information might interfere with future pleasurable activities. Interestingly, the decision to search or to postpone searching for information is influenced not only by the value and importance of the information itself but also by well-being maintenance goals related to possible detrimental effects that negative knowledge may have on unrelated future plans.

  15. OMI Ozone Profile and Tropospheric Ozone and Cross Evaluations with Chemical Transport Models

    Science.gov (United States)

    Liu, X.; Liu, J.; Duncan, B. N.; Yang, K.; Strahan, S. E.; Chance, K.; Bhartia, P. K.

    2013-05-01

    About five years of ozone profile and tropospheric ozone (October 2004-December 2009) from OMI are presented. The seasonal and inter-annual variations of tropospheric ozone in different regions are analyzed. To improve our understanding about processes controlling tropospheric ozone, we cross-evaluate the consistency of ozone profiles from the stratosphere to the troposphere between OMI retrievals, GMI combo model simulations (with two GMAO meteorological fields, GEOS-4 and MERRA reanalysis, called Aura4 and MERRA runs, respectively), and the GEOS-Chem model simulations, and investigate their differences in spatiotemporal distribution. The GMI ozone fields in both runs and the GEOS-Chem simulations generally show consistent seasonal, latitudinal variation and global distribution. Aura4 total ozone show positive biases of 10-30 DU at southern middle and high latitudes and negative biases of ~10-30 DU in the tropics, most of the biases originating from the lower stratosphere and upper troposphere (up to 20-50%). However, tropospheric ozone column usually agrees well to within 5 DU. MERRA total ozone generally compares well with OMI total ozone except with positive biases of ~10-20 DU at northern high latitudes. MERRA ozone profiles generally show positives of ~10-30% from the southern hemisphere to 20N. Aura-4 tropospheric ozone columns generally agree well with OMI to within 5 DU except in the tropics, where MERRA run has some positive biases of 5-10 DU. Differences between Aura4 and MERRA tropospheric ozone are investigated by examining various ozone precursors. The larger MERRA tropical tropospheric ozone likely results from the weak convection in the MERRA, which causes stronger stratospheric tropospheric exchange and weaker convection transport of typically poorer ozone and richer CO tropical air near the surface.

  16. Using Satellite Observations of Cloud Vertical Distribution to Improve Global Model Estimates of Cloud Radiative Effect on Key Tropospheric Oxidants

    Science.gov (United States)

    Liu, Hongyu; Crawford, James; Ham, Seung-Hee; Zhang, Bo; Kato, Seiji; Voulgarakis, Apostolos; Chen, Gao; Fairlie, Duncan; Duncan, Bryan; Yantosca, Robert

    2017-01-01

    Clouds directly affect tropospheric photochemistry through modification of solar radiation that determines photolysis frequencies. This effect is an important component of global tropospheric chemistry-climate interaction, and its understanding is thus essential for predicting the feedback of climate change on tropospheric chemistry.

  17. Status of Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    Science.gov (United States)

    Chance, K.; Liu, X.; Suleiman, R. M.; Flittner, D. E.; Al-Saadi, J. A.; Janz, S. J.

    2016-12-01

    TEMPO is now in the Assembly, Integration and Test (AI&T) phase, having passed its Key Decision Point C, Critical Design Reviews (CDRs) for the instrument and the ground systems, and the Test Readiness Review (TRR). The TEMPO instrument is scheduled for delivery in August 2017. The request for proposals to host TEMPO on a commercial geostationary satellite is scheduled for release by May 2017, with host selection hopefully completed by the end of calendar 2017. TEMPO is thus on schedule to measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City and Cuba to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution. It provides a measurement suite that includes the key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the high variability in the diurnal cycle of emissions and chemistry. The small spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies.TEMPO takes advantage of a GEO host spacecraft to provide a mission that measures the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available.TEMPO provides much of the atmospheric measurement capability recommended for GEO-CAPE in the 2007 National Research Council Decadal Survey, Earth Science and Applications from Space

  18. The Seasonal Response of Titan's Troposphere and Stratosphere

    Science.gov (United States)

    Flasar, F. M.; Schinder, P. J.; Achterberg, R. K.; Marouf, E. A.; French, R. G.; Kliore, A. J.; Rappaport, N. J.

    2009-01-01

    The radiative response of Titan's atmosphere varies by several orders of magnitude with altitude. This presents an interesting situation in which most of the stratosphere----at least that part above 100km is characterized by radiative relaxation times that are short compared to the length of a Titan season, and the troposphere and tropopause region by times that are larger than seasonal timescales. Consistent with this, Cassini CIRS spectra indicate stratospheric temperatures at 100-170 kin that are 20-30 K cooler at high northern latitudes in winter than those at equatorial and southern latitudes. Given the expectation that the situation will largely reverse in southern winter, the observed large meridional contrast is likely indicative of the expected seasonal variation at polar latitudes in both hemispheres. CIRS spectra do not as easily yield temperatures below 100 km in the lower stratosphere and tropopause region, because of the contribution of heterogeneously distributed aerosols and condensates to the infrared opacity. However, Cassini radio occultations probe both the stratosphere and troposphere, and below 80 km they show the thermal contrast with latitude to be muted, e.g,, approx.5 K near the tropopause at 40-50 km and approx.3 K just above the surface. This is consistent with the large radiative relaxation times at these altitudes and with efficient meridional heat transport. What is curious is the manner in which temperatures in the north winter polar atmosphere make the transition between the troposphere and lower stratosphere, where seasonal variations are relatively small, and higher altitudes, where they are large. Temperatures at all latitudes sounded by the radio occultations exhibit similar behavior in the lower stratosphere, increasing with altitude. Between 80 and 100 kin, however, the temperatures at high northern latitudes exhibit a sudden drop with increasing altitude, producing the meridional contrast in the upper stratosphere described

  19. Understanding Wave-mean Flow Feedbacks and Tropospheric Annular Variability

    Science.gov (United States)

    Lorenz, D. J.

    2016-12-01

    The structure of internal tropospheric variability is important for determining the impact of the stratosphere on the troposphere. This study aims to better understand the fundamental dynamical mechanisms that control the feedbacks between the eddies and the mean flow, which in turn select the tropospheric annular mode. Recent work using Rossby Wave Chromatography suggests that "barotropic processes", which directly impact the meridional propagation of wave activity (specifically the reflectivity of the poleward flank of the mid-latitude jet), are more important for the positive feedback between the annular mode and the eddies than "baroclinic processes", which involve changes in the generation of wave activity by baroclinic instability. In this study, experiments with a fully nonlinear quasi-geostrophic model are discussed which provide independent confirmation of the importance of barotropic versus baroclinic processes. The experiments take advantage of the steady-state balance at upper-levels between the meridional gradient in diabatic heating and the second derivative of the upper-level EP flux divergence. Simulations with standard Newtonian heating are compared to simulations with constant-in-time heating taken from the climatology of the standard run and it is found that the forced annular mode response to changes in surface friction is very similar. Moreover, as expected from the annular mode response, the eddy momentum fluxes are also very similar. This is despite the fact that the upper-level EP flux divergence is very different between the two simulations (upper-level EP flux divergence must remain constant in the constant heating simulation while in the standard simulation there is no such constraint). The upper-level balances are maintained by a large change in the baroclinic wave source (i.e. vertical EP flux), which is accompanied by little momentum flux change. Therefore the eddy momentum fluxes appear to be relatively insensitive to the wave

  20. Constraints on Saturn's Tropospheric General Circulation from Cassini ISS Images

    Science.gov (United States)

    DelGenio, Anthony D.; Barbara, John M.

    2013-01-01

    An automated cloud tracking algorithm is applied to Cassini Imaging Science Subsystem high-resolution apoapsis images of Saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near-global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze. Improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors, a more objective assessment at any latitude of the quality of the mean zonal wind, and a population of winds comparable in size to that available for the much higher contrast atmosphere of Jupiter. Zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled. Upper troposphere zonal winds derived from methane band images are approx. 10 m/s weaker than cloud level winds in the cores of eastward jets and approx. 5 m/s stronger on either side of the jet core, i.e., eastward jets appear to broaden with increasing altitude. In westward jet regions winds are approximately the same at both altitudes. Lateral eddy momentum fluxes are directed into eastward jet cores, including the strong equatorial jet, and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets, consistent with the upward broadening of these jets. The conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions (5.2x10(exp -5) sq m/s) and smaller in westward jet regions (1.6x10(exp -5) sqm/s) than the global mean value (4.1x10(ep -5) sq m/s). Overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on Saturn are maintained at least in part by eddies due to instabilities of the large-scale flow near and/or below the cloud level.

  1. Epidemiology of delayed ejaculation

    Science.gov (United States)

    Di Sante, Stefania; Mollaioli, Daniele; Gravina, Giovanni Luca; Ciocca, Giacomo; Limoncin, Erika; Carosa, Eleonora; Lenzi, Andrea

    2016-01-01

    A large body of literature on diminished ejaculatory disorders has been generated without the use of a clear diagnostic definition. Many studies have not distinguished between the orgasm and ejaculation disorders leading to doubtful results. Delayed ejaculation (DE) is one of the diminished ejaculatory disorders, which range from varying delays in ejaculatory latency to a complete inability to ejaculate. The present review is aimed at providing a comprehensive overview of the current knowledge on the definition and epidemiology of diminished ejaculatory disorders. We focus on the acquired diseases, such as benign prostatic hyperplasia (BPH) and specific drug regimens that may cause an iatrogenic form of ejaculatory disorder. In addition, the impact of aging is discussed since the prevalence of DE appears to be moderately but positively related to age. Finally, we also focus on the importance of the hormonal milieu on male ejaculation. To date, evidence on the endocrine control of ejaculation is derived from small clinical trials, but the evidence suggests that hormones modulate the ejaculatory process by altering its overall latency. PMID:27652226

  2. Epidemiology of delayed ejaculation.

    Science.gov (United States)

    Di Sante, Stefania; Mollaioli, Daniele; Gravina, Giovanni Luca; Ciocca, Giacomo; Limoncin, Erika; Carosa, Eleonora; Lenzi, Andrea; Jannini, Emmanuele A

    2016-08-01

    A large body of literature on diminished ejaculatory disorders has been generated without the use of a clear diagnostic definition. Many studies have not distinguished between the orgasm and ejaculation disorders leading to doubtful results. Delayed ejaculation (DE) is one of the diminished ejaculatory disorders, which range from varying delays in ejaculatory latency to a complete inability to ejaculate. The present review is aimed at providing a comprehensive overview of the current knowledge on the definition and epidemiology of diminished ejaculatory disorders. We focus on the acquired diseases, such as benign prostatic hyperplasia (BPH) and specific drug regimens that may cause an iatrogenic form of ejaculatory disorder. In addition, the impact of aging is discussed since the prevalence of DE appears to be moderately but positively related to age. Finally, we also focus on the importance of the hormonal milieu on male ejaculation. To date, evidence on the endocrine control of ejaculation is derived from small clinical trials, but the evidence suggests that hormones modulate the ejaculatory process by altering its overall latency.

  3. Delayed Choice Quantum Cryptography

    Science.gov (United States)

    Jeffrey, Evan; Kwiat, Paul

    2002-05-01

    Quantum Cryptography has recently gained attention as a method of communication with security guaranteed by the laws of physics. In particular, according to quantum mechanics, any measurement of an unknown quantum state perturbs the state in an easily detectable manner. One practical difficulty in implementing quantum cryptography is that Alice must encode each bit in a random basis, and Bob must choose the correct basis to get a shared bit of the final key. This necessarily introduces at least a 50% loss of data rate, and higher in protocols that use more than two bases in order to be more sensitive to eavesdroppers. We show that Bob can solve this by storing his photon until Alice has send the basis to use, allowing him to measure in the correct basis 100% of the time, while preventing Eve from having that information in time to use it maliciously. Bob accomplishes this storage by means of an optical delay line -- a pair of mirrors arranged so that his photon makes many round trips through the cavity before emerging and entering the detector. By using mirrors with a slight astigmatism, hope to achieve hundreds of round trips and a few microseconds of delay time.

  4. Pseudotumoral delayed cerebral radionecrosis

    Energy Technology Data Exchange (ETDEWEB)

    Ciaudo-Lacroix, C.; Lapresle, J. (Centre Hospitalier de Bicetre, 94 - Le Kremlin-Bicetre (France))

    1985-01-01

    A 60 year-old woman with a scalp epithelioma underwent radiotherapy, the dose being 57 Gray. A first epileptic seizure occurred twenty months later. Neurological examination revealed signs of left hemisphere involvement. ..gamma..EG, angiography, CT scans, demonstrated a pseudotumoral avascular process. On account of the localisation, the patient being right-handed, no surgical procedure was performed. In spite of corticotherapy and anticonvulsive treatment, seizures recurred and neurological signs slowly progressed. The patient died, 22 months after the first seizure, of an associated disseminated carcinoma with cachexia. Neuropathological examination showed a massive lesion presenting all the features of delayed radionecrosis in the left hemisphere: situated mainly in the white matter; numerous vascular abnormalities; wide-spread demyelination; disappearance of oligoglial cells. The Authors recall the clinical and anatomical aspects of this condition for which the only successful treatment is surgical removal when location and size of the lesion permit. Finally, the mechanisms which have been proposed to explain this delayed cerebral radionecrosis are discussed.

  5. Tropospheric correction of InSAR time-series with the weather research forecasting model: an application to volcanic deformation monitoring

    Science.gov (United States)

    Gong, W.; Meyer, F.; Webley, P.; Lu, Z.

    2010-12-01

    The potential of Interferometric Synthetic Aperture Radar (InSAR) for surveying volcanic deformation has been proven extensively over the last few decades. However, the value and applicability of InSAR for detecting the subtle signs of the onset of an eruptive even is limited by the influence of temporal decorrelation and electromagnetic path delay variations (e.g. the troposphere and ionosphere effects), as they reduce the sensitivity and accuracy of the technique. In this paper, we will present an integration of time series InSAR processing with predictions from the high-resolution Weather Research and Forecasting (WRF) Model to improve the performance of InSAR for volcano monitoring application, especially to increase InSAR ability to detect subtle pre-eruptive deformation. The non-hydrostatic WRF model is part of the latest generation of numerical weather prediction (NWP) and atmospheric simulation systems. WRF can be implemented with a nested grid system, allowing atmospheric delay phase maps to be created at a spatial resolution down to the 500 m and is expected to outperform other NWPs in term of prediction accuracy. We show that the integration of WRF with InSAR measurements allows reducing the amplitude and variance of atmospheric phase delay signals which increases the sensitivity of InSAR to deformation signals. Moreover, for some InSAR algorithms that select Phase-stable-points based on an analysis of phase variance, the mitigation of atmospheric signals with WRF leads to an increase of the density of detected coherent points. We apply the WRF-assisted InSAR technique to Unimak Island at the eastern Aleutians, where three active volcanic systems exist. By comparing the deformation monitoring results from the InSAR time series with and without the tropospheric correction, we demonstrate the advantage of applying WRF simulation result in InSAR tropospheric correction and the contribution this technique will provide to volcano monitoring. Structure

  6. Tropospheric haze and colors of the clear twilight sky.

    Science.gov (United States)

    Lee, Raymond L; Mollner, Duncan C

    2017-07-01

    At the earth's surface, clear-sky colors during civil twilights depend on the combined spectral effects of molecular scattering, extinction by tropospheric aerosols, and absorption by ozone. Molecular scattering alone cannot produce the most vivid twilight colors near the solar horizon, for which aerosol scattering and absorption are also required. However, less well known are haze aerosols' effects on twilight sky colors at larger scattering angles, including near the antisolar horizon. To analyze this range of colors, we compare 3D Monte Carlo simulations of skylight spectra with hyperspectral measurements of clear twilight skies over a wide range of aerosol optical depths. Our combined measurements and simulations indicate that (a) the purest antisolar twilight colors would occur in a purely molecular, multiple-scattering atmosphere, whereas (b) the most vivid solar-sky colors require at least some turbidity. Taken together, these results suggest that multiple scattering plays an important role in determining the redness of the antitwilight arch.

  7. Measurements of Pollution In The Troposphere (MOPITT) Validation through 2006

    Science.gov (United States)

    Emmons, L. K.; Edwards, D. P.; Deeter, M. N.; Gille, J. C.; Campos, T.; Nedelec, P.; Novelli, P.; Sachse, G.

    2009-01-01

    Comparisons of aircraft measurements of carbon monoxide (CO) to the retrievals of CO using observations from the Measurements of Pollution in The Troposphere (MOPITT) instrument onboard the Terra satellite are presented. Observations made as part of the NASA INTEX-B and NSF MIRAGE field campaigns during March May 2006 are used to validate the MOPITT CO retrievals, along with routine samples from 2001 through 2006 from NOAA and the MOZAIC measurements from commercial aircraft. A significant positive bias, around 20% for total column CO, in MOPITT CO was found in the comparison to in situ measurements during 2006. Comparisons to the long-term records of measurements from NOAA and MOZAIC revealed an increasing bias in the V3 MOPITT CO retrievals over time. The impact of an instrumental drift is illustrated through retrieval simulations.

  8. Measurements of Pollution In The Troposphere (MOPITT validation through 2006

    Directory of Open Access Journals (Sweden)

    L. K. Emmons

    2009-03-01

    Full Text Available Comparisons of aircraft measurements of carbon monoxide (CO to the retrievals of CO using observations from the Measurements of Pollution in The Troposphere (MOPITT instrument onboard the Terra satellite are presented. Observations made as part of the NASA INTEX-B and NSF MIRAGE field campaigns during March–May 2006 are used to validate the MOPITT CO retrievals, along with routine samples from 2001 through 2006 from NOAA and the MOZAIC measurements from commercial aircraft. A significant positive bias, around 20% for total column CO, in MOPITT CO was found in the comparison to in situ measurements during 2006. Comparisons to the long-term records of measurements from NOAA and MOZAIC revealed an increasing bias in the V3 MOPITT CO retrievals over time. The impact of an instrumental drift is illustrated through retrieval simulations.

  9. NOx cycle and tropospheric ozone isotope anomaly: an experimental investigation

    Science.gov (United States)

    Michalski, G.; Bhattacharya, S. K.; Girsch, G.

    2013-04-01

    The oxygen isotope composition of nitrogen oxides (NOx) in the atmosphere may be a useful tool for understanding the oxidation of NOx into nitric acid/nitrate in the atmosphere. A set of experiments were conducted to examine changes in isotopic composition of NOx due to O3-NOx photochemical cycling. At low NO2/O2 mixing ratios, NO2 becomes progressively and nearly equally enriched in 17O and 18O over time until it reaches a steady state with Δ17O values of 40.6 ± 1.9‰ and δ18O values of 84.2 ± 4‰, relative to the isotopic composition of the O2 gas. As the mixing ratio increases, isotopic exchange between O atoms and O2 and NOx suppresses the isotopic enrichments. A kinetic model simulating the observed data shows that the isotope effects during ozone formation play a more dominant role compared to kinetic isotope effects during NO oxidation or exchange of NO2. The model results are consistent with the data when the NO + O3 reaction occurs mainly via the transfer of the terminal atom of O3. The model predicts that under tropospheric concentrations of the three reactants, the timescale of NOx isotopic equilibrium ranges from hours (ppbv mixing ratios) to days/weeks (pptv) and yields steady state Δ17O and δ18O values of 46‰ and 115‰ respectively with respect to Vienna Standard Mean Ocean Water. Interpretation of tropospheric nitrate isotope data can now be done with the derived rate coefficients of the major isotopologue reactions at various pressures.

  10. Trends and annual cycles in soundings of Arctic tropospheric ozone

    Directory of Open Access Journals (Sweden)

    B. Christiansen

    2017-08-01

    Full Text Available Ozone soundings from nine Nordic stations have been homogenized and interpolated to standard pressure levels. The different stations have very different data coverage; the longest period with data is from the end of the 1980s to 2014. At each pressure level the homogenized ozone time series have been analysed with a model that includes both low-frequency variability in the form of a polynomial, an annual cycle with harmonics, the possibility for low-frequency variability in the annual amplitude and phasing, and either white noise or noise given by a first-order autoregressive process. The fitting of the parameters is performed with a Bayesian approach not only giving the mean values but also confidence intervals. The results show that all stations agree on a well-defined annual cycle in the free troposphere with a relatively confined maximum in the early summer. Regarding the low-frequency variability, it is found that Scoresbysund, Ny Ålesund, Sodankylä, Eureka, and Ørland show similar, significant signals with a maximum near 2005 followed by a decrease. This change is characteristic for all pressure levels in the free troposphere. A significant change in the annual cycle was found for Ny Ålesund, Scoresbysund, and Sodankylä. The changes at these stations are in agreement with the interpretation that the early summer maximum is appearing earlier in the year. The results are shown to be robust to the different settings of the model parameters such as the order of the polynomial, number of harmonics in the annual cycle, and the type of noise.

  11. Trends and annual cycles in soundings of Arctic tropospheric ozone

    Science.gov (United States)

    Christiansen, Bo; Jepsen, Nis; Kivi, Rigel; Hansen, Georg; Larsen, Niels; Smith Korsholm, Ulrik

    2017-08-01

    Ozone soundings from nine Nordic stations have been homogenized and interpolated to standard pressure levels. The different stations have very different data coverage; the longest period with data is from the end of the 1980s to 2014. At each pressure level the homogenized ozone time series have been analysed with a model that includes both low-frequency variability in the form of a polynomial, an annual cycle with harmonics, the possibility for low-frequency variability in the annual amplitude and phasing, and either white noise or noise given by a first-order autoregressive process. The fitting of the parameters is performed with a Bayesian approach not only giving the mean values but also confidence intervals. The results show that all stations agree on a well-defined annual cycle in the free troposphere with a relatively confined maximum in the early summer. Regarding the low-frequency variability, it is found that Scoresbysund, Ny Ålesund, Sodankylä, Eureka, and Ørland show similar, significant signals with a maximum near 2005 followed by a decrease. This change is characteristic for all pressure levels in the free troposphere. A significant change in the annual cycle was found for Ny Ålesund, Scoresbysund, and Sodankylä. The changes at these stations are in agreement with the interpretation that the early summer maximum is appearing earlier in the year. The results are shown to be robust to the different settings of the model parameters such as the order of the polynomial, number of harmonics in the annual cycle, and the type of noise.

  12. Satellite bulk tropospheric temperatures as a metric for climate sensitivity

    Science.gov (United States)

    Christy, John R.; McNider, Richard T.

    2017-11-01

    We identify and remove the main natural perturbations (e.g. volcanic activity, ENSOs) from the global mean lower tropospheric temperatures ( T LT ) over January 1979 - June 2017 to estimate the underlying, potentially human-forced trend. The unaltered value is +0.155 K dec-1 while the adjusted trend is +0.096 K dec-1, related primarily to the removal of volcanic cooling in the early part of the record. This is essentially the same value we determined in 1994 (+0.09 K dec-1, Christy and McNider, 1994) using only 15 years of data. If the warming rate of +0.096 K dec-1 represents the net T LT response to increasing greenhouse radiative forcings, this implies that the T LT tropospheric transient climate response (Δ T LT at the time CO2 doubles) is +1.10 ± 0.26 K which is about half of the average of the IPCC AR5 climate models of 2.31 ± 0.20 K. Assuming that the net remaining unknown internal and external natural forcing over this period is near zero, the mismatch since 1979 between observations and CMIP-5 model values suggests that excessive sensitivity to enhanced radiative forcing in the models can be appreciable. The tropical region is mainly responsible for this discrepancy suggesting processes that are the likely sources of the extra sensitivity are (a) the parameterized hydrology of the deep atmosphere, (b) the parameterized heat-partitioning at the oceanatmosphere interface and/or (c) unknown natural variations.

  13. Stability and delay sensitivity of neutral fractional-delay systems

    Science.gov (United States)

    Xu, Qi; Shi, Min; Wang, Zaihua

    2016-08-01

    This paper generalizes the stability test method via integral estimation for integer-order neutral time-delay systems to neutral fractional-delay systems. The key step in stability test is the calculation of the number of unstable characteristic roots that is described by a definite integral over an interval from zero to a sufficient large upper limit. Algorithms for correctly estimating the upper limits of the integral are given in two concise ways, parameter dependent or independent. A special feature of the proposed method is that it judges the stability of fractional-delay systems simply by using rough integral estimation. Meanwhile, the paper shows that for some neutral fractional-delay systems, the stability is extremely sensitive to the change of time delays. Examples are given for demonstrating the proposed method as well as the delay sensitivity.

  14. Sources of Springtime Tropospheric Ozone Over North China: A Modeling Analysis of Ozonesonde and Satellite Observations

    Science.gov (United States)

    Liu, H.; Chan, C.; Huang, J.; Zhang, Y.; Choi, H.; Crawford, J. H.; Considine, D. B.; Zheng, X.; Oltmans, S. J.; Liu, S. C.; Zhang, L.; Liu, X.; Thouret, V.

    2012-12-01

    Tropospheric ozone concentrations and emissions of NOx have both increased significantly over China as a result of rapid industrialization during the past decade. These trends degrade local and regional air quality and have important effects on background tropospheric ozone and surface ozone over downwind North Pacific and North America. In-situ observations of tropospheric ozone over China are therefore essential to testing and improving our understanding of the impact of Asian anthropogenic (versus natural) emissions and various chemical, physical, and dynamical processes on both regional and global tropospheric ozone. Despite their critical importance, in-situ observations of tropospheric ozone profiles over China have been few and far between in most of the country. To investigate the ensemble of processes that control the distribution, variability, and sources of springtime tropospheric ozone over China and its surrounding regions, an intensive ozonesonde sounding campaign, called Transport of Air Pollutants and Tropospheric Ozone over China (TAPTO-China), was conducted at nine locations across China in the springs of 2004 (South China) and 2005 (North China). In this paper, we use a global 3-D model of tropospheric chemistry (GEOS-Chem) to examine the characteristics of distribution and variability and quantify various sources of tropospheric ozone over North China by analysis of intensive ozonesonde data obtained at four stations in North / Northwest China during the second phase of TAPTO-China (April-May 2005). These four stations include Xining (36.43N, 101.45E), Beijing (39.80N, 116.18E), Longfengshan (44.44N, 127.36E), and Aletai (47.73N, 88.08E). We drive GEOS-Chem with two sets of assimilated meteorological observations (GEOS-4 and GEOS-5) from the Goddard Earth Observing System (GEOS) of the NASA Global Modeling and Assimilation Office (GAMO), allowing us to examine the impacts of variability in meteorology. We show that the observed tropospheric

  15. GPD+ Wet Tropospheric Corrections for CryoSat-2 and GFO Altimetry Missions

    Directory of Open Access Journals (Sweden)

    M. Joana Fernandes

    2016-10-01

    Full Text Available Due to its large space-time variability, the wet tropospheric correction (WTC is still considered a significant error source in satellite altimetry. This paper presents the GNSS (Global Navigation Satellite Systems derived Path Delay Plus (GPD+, the most recent algorithm developed at the University of Porto to retrieve improved WTC for radar altimeter missions. The GPD+ are WTC estimated by space-time objective analysis, by combining all available observations in the vicinity of the point: valid measurements from the on-board microwave radiometer (MWR, from GNSS coastal and island stations and from scanning imaging MWR on board various remote sensing missions. The GPD+ corrections are available both for missions which do not possess an on-board microwave radiometer such as CryoSat-2 (CS-2 and for all missions which carry this sensor, by addressing the various error sources inherent to the MWR-derived WTC. To ensure long-term stability of the corrections, the large set of radiometers used in this study have been calibrated with respect to the Special Sensor Microwave Imager (SSM/I and the SSM/I Sounder (SSM/IS. The application of the algorithm to CS-2 and Geosat Follow-on (GFO, as representative altimetric missions without and with a MWR aboard the respective spacecraft, is described. Results show that, for both missions, the new WTC significantly reduces the sea level anomaly (SLA variance with respect to the model-based corrections. For GFO, the new WTC also leads to a large reduction in SLA variance with respect to the MWR-derived WTC, recovering a large number of observations in the coastal and polar regions and full sets of tracks and several cycles when MWR measurements are missing or invalid. Overall, the algorithm allows the recovery of a significant number of measurements, ensuring the continuity and consistency of the correction in the open-ocean/coastal transition zone and at high latitudes.

  16. On the relationship between tropospheric conditions and widespread hot days in Iran

    Science.gov (United States)

    Asakereh, Hossein; Shadman, Hassan

    2018-01-01

    The present study investigated how the tropospheric conditions relate to the occurrence of widespread hot days (WHD) in Iran using the data of maximum daily temperature and other tropospheric variables. To better understand the tropospheric conditions during WHD, different patterns of tropospheric circulation were examined systematically. Four tropospheric types were identified based on sea level pressure (SLP). SLP, 500 hPa height, anomaly patterns, and warm advection maps were constructed for typical days of each group. The tropospheric conditions associated with hot days occurred simultaneously with a low-pressure system at sea level, a ridge at middle troposphere over Iran, and a pronounced trough over the Mediterranean Sea at 500 hPa. These conditions caused air mass from subtropical regions toward Iran. That is, northward, northeastward, and even eastward winds injected heat with warm origins toward the country. Hot days compounded by drought conditions have affected many parts of the country in different ways such as decrease in the agricultural products in numerous areas and significant discharge reduction in many rivers. The society is also very likely to face considerable challenges to cope with hot days. The findings of the study can be utilized in climate modeling and climate prediction of hot days in the country. Accordingly, water and electricity consumption can be planned with further precision and water consumption can be managed in crises.

  17. Origins of Tropospheric Ozone Interannual Variation (IAV) over Reunion: A Model Investigation

    Science.gov (United States)

    Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Francoise

    2016-01-01

    Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Reunion Island (21.1 degrees South Latitude, 55.5 degrees East Longitude) in June-August. Here we examine possible causes of the observed ozone variation at Reunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Reunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Reunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Reunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited tothe lower troposphere near the surface in August-September.

  18. Origins of tropospheric ozone interannual variation over Réunion: A model investigation

    Science.gov (United States)

    Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Françoise

    2016-01-01

    Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Réunion Island (21.1°S, 55.5°E) in June-August. Here we examine possible causes of the observed ozone variation at Réunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications meteorological fields. Réunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Réunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Réunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited to the lower troposphere near the surface in August-September.

  19. Estimating the climate significance of halogen-driven ozone loss in the tropical marine troposphere

    Directory of Open Access Journals (Sweden)

    A. Saiz-Lopez

    2012-05-01

    Full Text Available We have integrated observations of tropospheric ozone, very short-lived (VSL halocarbons and reactive iodine and bromine species from a wide variety of tropical data sources with the global CAM-Chem chemistry-climate model and offline radiative transfer calculations to compute the contribution of halogen chemistry to ozone loss and associated radiative impact in the tropical marine troposphere. The inclusion of tropospheric halogen chemistry in CAM-Chem leads to an annually averaged depletion of around 10% (~2.5 Dobson units of the tropical tropospheric ozone column, with largest effects in the middle to upper troposphere. This depletion contributes approximately −0.10 W m−2 to the radiative flux at the tropical tropopause. This negative flux is of similar magnitude to the ~0.33 W m−2 contribution of tropospheric ozone to present-day radiative balance as recently estimated from satellite observations. We find that the implementation of oceanic halogen sources and chemistry in climate models is an important component of the natural background ozone budget and we suggest that it needs to be considered when estimating both preindustrial ozone baseline levels and long term changes in tropospheric ozone.

  20. Delayed cure bismaleimide resins

    Science.gov (United States)

    Adams, Johnnie E.; Jamieson, Donald R.

    1984-08-07

    Polybismaleimides prepared by delayed curing of bis-imides having the formula ##STR1## wherein R.sub.1 and R.sub.2 each independently is H, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, Cl or Br, or R.sub.1 and R.sub.2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R.sub.1 and R.sub.2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the --(CH.sub.2).sub.n -- group, optionally, is substituted by 1-3 methyl groups or by fluorine.

  1. Delay tolerant networks

    CERN Document Server

    Gao, Longxiang; Luan, Tom H

    2015-01-01

    This brief presents emerging and promising communication methods for network reliability via delay tolerant networks (DTNs). Different from traditional networks, DTNs possess unique features, such as long latency and unstable network topology. As a result, DTNs can be widely applied to critical applications, such as space communications, disaster rescue, and battlefield communications. The brief provides a complete investigation of DTNs and their current applications, from an overview to the latest development in the area. The core issue of data forward in DTNs is tackled, including the importance of social characteristics, which is an essential feature if the mobile devices are used for human communication. Security and privacy issues in DTNs are discussed, and future work is also discussed.

  2. Synchronizing time delay systems using variable delay in coupling

    Energy Technology Data Exchange (ETDEWEB)

    Ambika, G., E-mail: g.ambika@iiserpune.ac.in [Indian Institute of Science Education and Research, Pune 411 021 (India); Amritkar, R.E., E-mail: amritkar@prl.res.in [Physical Research Laboratory, Ahmedabad 380 009 (India)

    2011-11-15

    Highlights: > Delay and anticipation in coupling function varies with system dynamics. > Delay or anticipation of the synchronized state is independent of system delay. > Stability analysis developed is quite general. > We demonstrate enhanced security in communication. > Generalized synchronization possible over a wide range of parameter mismatch. - Abstract: We present a mechanism for synchronizing time delay systems using one way coupling with a variable delay in coupling that is reset at finite intervals. We present the analysis of the error dynamics that helps to isolate regions of stability of the synchronized state in the parameter space of interest for single and multiple delays. We supplement this by numerical simulations in a standard time delay system like Mackey Glass system. This method has the advantage that it can be adjusted to be delay or anticipatory in synchronization with a time which is independent of the system delay. We demonstrate the use of this method in communication using the bi channel scheme. We show that since the synchronizing channel carries information from transmitter only at intervals of reset time, it is not susceptible to an easy reconstruction.

  3. Concurrent Delay in Construction Disputes

    DEFF Research Database (Denmark)

    Cavaleri, Sylvie Cécile

    Delay is one of the issues most frequently encountered in today’s construction industry; it causes significant economic damage to all parties involved. Construction contracts, standard and bespoke, almost invariably consider delay from a perspective of single liability. If the event causing...... solutions to the issue of concurrent delay in a comparative perspective between common and civil law systems, with an emphasis on Danish and English law....

  4. Location Estimation using Delayed Measurements

    DEFF Research Database (Denmark)

    Bak, Martin; Larsen, Thomas Dall; Nørgård, Peter Magnus

    1998-01-01

    When combining data from various sensors it is vital to acknowledge possible measurement delays. Furthermore, the sensor fusion algorithm, often a Kalman filter, should be modified in order to handle the delay. The paper examines different possibilities for handling delays and applies a new...... technique to a sensor fusion system for estimating the location of an autonomous guided vehicle. The system fuses encoder and vision measurements in an extended Kalman filter. Results from experiments in a real environment are reported...

  5. Modeling delay in genetic networks: from delay birth-death processes to delay stochastic differential equations.

    Science.gov (United States)

    Gupta, Chinmaya; López, José Manuel; Azencott, Robert; Bennett, Matthew R; Josić, Krešimir; Ott, William

    2014-05-28

    Delay is an important and ubiquitous aspect of many biochemical processes. For example, delay plays a central role in the dynamics of genetic regulatory networks as it stems from the sequential assembly of first mRNA and then protein. Genetic regulatory networks are therefore frequently modeled as stochastic birth-death processes with delay. Here, we examine the relationship between delay birth-death processes and their appropriate approximating delay chemical Langevin equations. We prove a quantitative bound on the error between the pathwise realizations of these two processes. Our results hold for both fixed delay and distributed delay. Simulations demonstrate that the delay chemical Langevin approximation is accurate even at moderate system sizes. It captures dynamical features such as the oscillatory behavior in negative feedback circuits, cross-correlations between nodes in a network, and spatial and temporal information in two commonly studied motifs of metastability in biochemical systems. Overall, these results provide a foundation for using delay stochastic differential equations to approximate the dynamics of birth-death processes with delay.

  6. Time Delay of CGM Sensors

    Science.gov (United States)

    Schmelzeisen-Redeker, Günther; Schoemaker, Michael; Kirchsteiger, Harald; Freckmann, Guido; Heinemann, Lutz; del Re, Luigi

    2015-01-01

    Background: Continuous glucose monitoring (CGM) is a powerful tool to support the optimization of glucose control of patients with diabetes. However, CGM systems measure glucose in interstitial fluid but not in blood. Rapid changes in one compartment are not accompanied by similar changes in the other, but follow with some delay. Such time delays hamper detection of, for example, hypoglycemic events. Our aim is to discuss the causes and extent of time delays and approaches to compensate for these. Methods: CGM data were obtained in a clinical study with 37 patients with a prototype glucose sensor. The study was divided into 5 phases over 2 years. In all, 8 patients participated in 2 phases separated by 8 months. A total number of 108 CGM data sets including raw signals were used for data analysis and were processed by statistical methods to obtain estimates of the time delay. Results: Overall mean (SD) time delay of the raw signals with respect to blood glucose was 9.5 (3.7) min, median was 9 min (interquartile range 4 min). Analysis of time delays observed in the same patients separated by 8 months suggests a patient dependent delay. No significant correlation was observed between delay and anamnestic or anthropometric data. The use of a prediction algorithm reduced the delay by 4 minutes on average. Conclusions: Prediction algorithms should be used to provide real-time CGM readings more consistent with simultaneous measurements by SMBG. Patient specificity may play an important role in improving prediction quality. PMID:26243773

  7. Delayed visual maturation and autism.

    Science.gov (United States)

    Goodman, R; Ashby, L

    1990-09-01

    Three boys are described with a mixed developmental disorder, which so far appears to have a relatively good prognosis. Each boy presented in early infancy with visual unresponsiveness, which spontaneously resolved. This delayed visual maturation was accompanied or followed by severe autistic impairment, general developmental delay, hypotonia and clumsiness. Subsequent progress has been unexpectedly favourable, with striking improvements in language, play, social interest and social competence. Widespread, patchy delay in brain maturation could possibly account for this combination of delayed visual maturation and autism, with a good prognosis.

  8. The Structure and Dynamics of Titan's Middle Atmosphere and Troposphere

    Science.gov (United States)

    Flasar, F.M.; Achterberg, R.K.; Schinder, P.J.

    2009-01-01

    Titan, after Venus, is the second example in the solar system of an atmosphere with a global cyclostrophic circulation. The origin and maintenance of these superrotating atmospheres is not well understood, but Titan has a strong seasonal modulation in the middle atmosphere, and the seasonal changes in the winds may offer clues. The pole in winter and early spring is characterized by temperatures 20-30 K cooler at 140-170 km than those at low latitudes, and strong circumpolar winds as high as 190 m/s at 200- 250 km. At these levels the polar region is characterized by enhanced concentrations of several organic gases, and also detectable condensates. All this suggests that the polar vortex provides a mixing barrier between winter polar and lower-latitude air masses, analogous to the polar ozone holes on Earth. Because the concentrations of organic gases increase with altitude in the middle atmosphere, the observed enhancements suggest subsidence over the winter pole. Consistent with this are the observed temperatures approximately 200 K at the winter-polar stratopause (280 km), making it the warmest part of the atmosphere. The warm stratopause likely results from adiabatic heating associated with the subsidence. Recent observations in late northern winter and early spring indicate that the warm anomaly at the winter-polar stratopause is weakening;. In contrast to the middle atmosphere, latitude contrasts in tropospheric temperatures are muted. During the northern winter season, they were approximately 5 K at the tropopause and 3 K or less near the surface, being coldest at high northern latitudes. This is understandable in terms of the long radiative relaxation times in the troposphere, compared to times that are much shorter than a season in the upper stratosphere and higher. Curiously, the transition between the small meridional contrast (and presumably seasonal variations) in temperatures observed in the troposphere and the large variations observed at higher

  9. Delay of gratification and delay discounting in rats.

    Science.gov (United States)

    Reynolds, Brady; de Wit, Harriet; Richards, Jerry

    2002-09-30

    Delay discounting (DD) and delay of gratification (DG) are two measures of impulsive behavior often viewed as reflecting the same or equivalent processes. However, there are some key differences in the contingencies of reinforcement between the procedures that may have implications for understanding impulsivity. This study used DD and DG procedures to determine if differences in contingencies of reinforcement specified by DD and DG alters how much organisms discount the value of delayed reinforcers. Twenty-four water-deprived rats performed one of two Adjusting Amount procedures, which consisted of repeated choices between a fixed amount of water (250 &mgr;l) delivered after a delay (0, 4, 8, 16, or 32 s) and an adjusting, usually lesser amount delivered immediately. Half of the rats (n=12) performed a DD procedure designed to assess preference for immediate over delayed reinforcers in which they had discrete choices between the immediate and delayed amounts of water. A DG procedure was used for the other half of the rats (n=12). In the DG procedure rats also selected between immediate and delayed alternatives, but if they chose the delayed alternative they could switch to and receive the immediate alternative at any time during the delay to the larger reward. In the DD procedure switching responses were not reinforced but were still recorded and used for analyses. The DD functions of the two groups did not differ significantly. However, at the longer delays, the DG group made significantly fewer switching responses than the DD group. A possible role of response inhibition in the DG procedure is discussed.

  10. Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) - meteorological data from Wallops ground station

    Data.gov (United States)

    National Aeronautics and Space Administration — TARFOX_WALLOPS_MET is the Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) Surface Meteorological data set Wallops ground station.The TARFOX...

  11. Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) - Vaisala Radiosonde data from Wallops ground station

    Data.gov (United States)

    National Aeronautics and Space Administration — TARFOX_WALLOPS_SONDE is the Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) Vaisala radiosonde data set from balloons launched at Wallops...

  12. Acidification and tropospheric ozone in Europe: towards a dynamic economic analysis

    NARCIS (Netherlands)

    Schmieman, E.C.

    2001-01-01

    Acidification and tropospheric ozone are important transboundary environmental problems with many economic and environmental aspects related to their role in the biogeochemical cycles. The main acidic substances are sulphur dioxide, nitrogen oxides and ammonia. The most important precursors

  13. Improving the Horizontal Transport in the Lower Troposphere with Four Dimensional Data Assimilation

    Science.gov (United States)

    The physical processes involved in air quality modeling are governed by dynamically-generated meteorological model fields. This research focuses on reducing the uncertainty in the horizontal transport in the lower troposphere by improving the four dimensional data assimilation (F...

  14. Potential Vorticity based parameterization for specification of Upper troposphere/lower stratosphere ozone in atmospheric models

    Data.gov (United States)

    U.S. Environmental Protection Agency — Potential Vorticity based parameterization for specification of Upper troposphere/lower stratosphere ozone in atmospheric models - the data set consists of 3D O3...

  15. SAFARI 2000 TOMS Tropospheric Ozone Data, Southern Africa Subset, Dry Season 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — Tropical Tropospheric Ozone (TTO) data from Earth Probe (EP) Total Ozone Mapping Spectrometer (TOMS) for the period of August 8-September 29, 2000 were processed and...

  16. NOAA Climate Data Record for Mean Layer Temperature (Upper Troposphere & Lower Stratosphere) from UCAR, Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Temperatures of Troposphere / Stratosphere (TTS) (AMSU channel 7 and MSU channel 3) CDR is generated by using National Oceanic and Atmospheric Administration...

  17. Overview of mercury measurements in the Antarctic troposphere

    Directory of Open Access Journals (Sweden)

    A. Dommergue

    2010-04-01

    Full Text Available Polar ecosystems are considered to be the last pristine environments of the earth relatively uninfluenced by human activities. Antarctica in particular, compared to the Arctic is considered to be even less affected by any kind of anthropogenic influences. Once contaminants reach the Polar Regions, their lifetime in the troposphere depends on local removal processes. Atmospheric mercury, in particular, has unique characteristics that include long-range transport to Polar Regions and the transformation to more toxic and water-soluble compounds that may potentially become bioavailable. These chemical-physical properties have placed mercury on the priority list of an increasing number of International, European and National conventions, and agreements, aimed at the protection of the ecosystems including human health (i.e. GEO, UNEP, AMAP, UN-ECE, HELCOM, OSPAR. This interest, in turn, stimulates a significant amount of research including measurements of gaseous elemental mercury reaction rate constant with atmospheric oxidants, experimental and modelling studies in order to understand the cycling of mercury in Polar Regions, and its impact to these ecosystems. Special attention in terms of contamination of Polar Regions is paid to the consequences of the springtime phenomena, referred to as "Atmospheric Mercury Depletion Events" (AMDEs, during which elemental mercury through a series of photochemically-initiated reactions involving halogens, may be converted to a reactive form that may accumulate in polar coastal, or sea ice, ecosystems. The discovery of the AMDEs, first noted in the Arctic, has also been observed at both poles and was initially considered to result in an important net input of atmospheric mercury into the polar surfaces. However, recent studies point out that complex processes take place after deposition that may result in less significant net-inputs from the atmosphere since a fraction, sometimes significant, of deposited mercury

  18. Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

    Science.gov (United States)

    Newsome, Ben; Evans, Mat

    2017-12-01

    Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global, use these rate constants. Expert panels evaluate laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the Jet Propulsion Laboratory (JPL) and International Union of Pure and Applied Chemistry (IUPAC) evaluations we assess the influence of 50 mainly inorganic rate constants and 10 photolysis rates on tropospheric composition through the use of the GEOS-Chem chemistry transport model. We assess the impact on four standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH →M HNO3 and O3 + NO → NO2 + O2 are the two largest sources of uncertainty in these metrics. The absolute magnitude of the change in the metrics is similar if rate constants are increased or decreased by their σ values. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 10, 11, 16 and 16 %, respectively. These are larger than the spread between models in recent model intercomparisons. Remote regions such as the tropics, poles and upper

  19. Delay dynamic equations with stability

    Directory of Open Access Journals (Sweden)

    Krueger Robert J

    2006-01-01

    Full Text Available We first give conditions which guarantee that every solution of a first order linear delay dynamic equation for isolated time scales vanishes at infinity. Several interesting examples are given. In the last half of the paper, we give conditions under which the trivial solution of a nonlinear delay dynamic equation is asymptotically stable, for arbitrary time scales.

  20. Registration Delay and Student Performance

    Science.gov (United States)

    Siefken, Jason

    2017-01-01

    Tracking the difference between the time a first-year student is allowed to register for a course and the time he or she does register for a course (a student's registration delay), we notice a negative correlation between registration delay and final grade in a course. The difference between a student who registers within the first two minutes…

  1. Delayed Reinforcement of Operant Behavior

    Science.gov (United States)

    Lattal, Kennon A.

    2010-01-01

    The experimental analysis of delay of reinforcement is considered from the perspective of three questions that seem basic not only to understanding delay of reinforcement but also, by implication, the contributions of temporal relations between events to operant behavior. The first question is whether effects of the temporal relation between…

  2. #FakeNobelDelayReasons

    CERN Document Server

    2013-01-01

    Tuesday’s hour-long delay of the Nobel Prize in Physics announcement was (and still is) quite the cause for speculation. But on the Twittersphere, it was simply the catalyst for some fantastic puns, so-bad-they're-good physics jokes and other shenanigans. Here are some of our favourite #FakeNobelDelayReasons.    

  3. Classification of tropospheric ozone profiles over Johannesburg based on mozaic aircraft data

    Directory of Open Access Journals (Sweden)

    R. D. Diab

    2003-01-01

    Full Text Available Each ozone profile is a unique response to the photochemical and dynamic processes operating in the troposphere and hence is critical to our understanding of processes and their relative contributions to the tropospheric ozone budget. Traditionally, mean profiles, together with some measure of variability, averaged by season or year at a particular location have been presented as a climatology. However, the mean profile is difficult to interpret because of the counteracting influences present in the micro-structure. On the other hand, case study analysis, whilst revealing, only applies to isolated conditions. In a search for pattern and order within ozone profiles, a classification based on a cluster analysis technique has been applied in this study. Ozone profiles are grouped according to the magnitude and altitude of ozone concentration. This technique has been tested with 56 ozone profiles at Johannesburg, South Africa, recorded by aircraft as part of the MOZAIC (Measurement of Ozone and Water Vapor aboard Airbus In-service Aircraft program. Six distinct groups of ozone profiles have been identified and their characteristics described. The widely recognized spring maximum in tropospheric ozone is identified through the classification, but a new summertime mid-tropospheric enhancement due to the penetration of tropical air masses from continental regions in central Africa has been identified. Back trajectory modeling is used to provide evidence of the different origins of ozone enhancements in each of the classes. Continental areas over central Africa are shown to be responsible for the low to mid-tropospheric enhancement in spring and the mid-tropospheric peak in summer, whereas the winter low-tropospheric enhancement is attributed to local sources. The dominance of westerly winds through the troposphere associated with the passage of a mid-latitude cyclone gives rise to reduced ozone values.

  4. The Influence of Radiation on Ice Crystal Spectrum in the Upper Troposphere

    Science.gov (United States)

    Zeng, Xiping

    2008-01-01

    This theoretical study is carried out to investigate the effect of radiation on ice crystal spectrum in the upper troposphere. First, an explicit expression is obtained for the ice crystal growth rate that takes account of radiative and kinetic effects. Second, the expression is used to quantitatively analyze how radiation broadens the ice crystal spectrum and then reveal a new precipitation mechanism in the upper troposphere and the stratosphere. Third, the radiative effect is used to explain the subvisual clouds near the tropopause.

  5. Contributions of the troposphere and stratosphere to CH4 model biases

    Science.gov (United States)

    Wang, Zhiting; Warneke, Thorsten; Deutscher, Nicholas M.; Notholt, Justus; Karstens, Ute; Saunois, Marielle; Schneider, Matthias; Sussmann, Ralf; Sembhi, Harjinder; Griffith, David W. T.; Pollard, Dave F.; Kivi, Rigel; Petri, Christof; Velazco, Voltaire A.; Ramonet, Michel; Chen, Huilin

    2017-11-01

    Inverse modelling is a useful tool for retrieving CH4 fluxes; however, evaluation of the applied chemical transport model is an important step before using the inverted emissions. For inversions using column data one concern is how well the model represents stratospheric and tropospheric CH4 when assimilating total column measurements. In this study atmospheric CH4 from three inverse models is compared to FTS (Fourier transform spectrometry), satellite and in situ measurements. Using the FTS measurements the model biases are separated into stratospheric and tropospheric contributions. When averaged over all FTS sites the model bias amplitudes (absolute model to FTS differences) are 7.4 ± 5.1, 6.7 ± 4.8, and 8.1 ± 5.5 ppb in the tropospheric partial column (the column from the surface to the tropopause) for the models TM3, TM5-4DVAR, and LMDz-PYVAR, respectively, and 4.3 ± 9.9, 4.7 ± 9.9, and 6.2 ± 11.2 ppb in the stratospheric partial column (the column from the tropopause to the top of the atmosphere). The model biases in the tropospheric partial column show a latitudinal gradient for all models; however there are no clear latitudinal dependencies for the model biases in the stratospheric partial column visible except with the LMDz-PYVAR model. Comparing modelled and FTS-measured tropospheric column-averaged mole fractions reveals a similar latitudinal gradient in the model biases but comparison with in situ measured mole fractions in the troposphere does not show a latitudinal gradient, which is attributed to the different longitudinal coverage of FTS and in situ measurements. Similarly, a latitudinal pattern exists in model biases in vertical CH4 gradients in the troposphere, which indicates that vertical transport of tropospheric CH4 is not represented correctly in the models.

  6. Tropospheric Gradient Estimation at CODE : Results from Global Solutions (1.Ground-Based GPS Meteorology)

    OpenAIRE

    Micheal, MEINDL; Stefan, SCHAER; Urs, HUGENTOBLER; Gerhard, BEUTLER; Astronomical Institute, University of Berne; Astronomical Institute, University of Berne; Astronomical Institute, University of Berne; Astronomical Institute, University of Berne

    2004-01-01

    Observations at low elevation angles are gathered and used for high accuracy GPS analyses. Introducing tropospheric gradient parameters in the estimation process allows it to take into account of azimuthal variations of tropospheric refraction. This measure significantly improves the repeatability of station coordinates. Most of the mean gradients for stations in the northern and the southern hemisphere show a similar behavior. By combining several years of data from a global solution results...

  7. Observations and Model Analysis of Enhanced Oxidized Mercury in the Free Troposphere during NOMADSS

    Science.gov (United States)

    Gratz, L.; Shah, V.; Ambrose, J. L., II; Jaffe, D. A.; Jaegle, L.; Selin, N. E.; Song, S.; Festa, J.; Stutz, J.

    2014-12-01

    Mercury (Hg) is a hazardous neurotoxic pollutant with complex atmospheric speciation and chemistry. It exists in the atmosphere primarily as gaseous elemental Hg (GEM), with a lifetime on the order of months, while oxidized Hg is more water soluble and deposits readily. Thus, Hg is considered both a local and a global pollutant. There are significant limitations in our understanding of global Hg cycling, including the sources and chemical mechanisms producing enhanced oxidized Hg in the free troposphere. Ground-based and airborne studies have associated free tropospheric oxidized Hg with GEM oxidation and atmospheric subsidence. Chemical transport models suggest that free tropospheric GEM oxidation is largely attributable to bromine (Br) atoms. During the 2013 Nitrogen Oxidants Mercury and Aerosol Distributions Sources and Sinks (NOMADSS) campaign, we sought to quantify the distribution and chemical transformation of Hg species in the free troposphere over the southeastern US. Enhanced oxidized Hg over North Texas was associated with long-range transport and subsidence from the sub-tropical Pacific free troposphere, where GEOS-Chem predicts air enriched in oxidized Hg. Bromine oxide (BrO) concentrations were also elevated over North Texas, perhaps supporting halogen oxidation as a source of free tropospheric oxidized Hg. Over the Atlantic Ocean, oxidized Hg up to 680 pg m-3 was associated with GEM oxidation and subsidence within the Atlantic high pressure system. The standard GEOS-Chem model underestimates free tropospheric oxidized Hg in these locations by a factor of three to ten, possibly due to underestimation of Br concentrations and/or uncertainty in the Hg+Br rate constant. We investigate GEOS-Chem's improved ability to reproduce the observed concentrations by tripling free tropospheric Br in the tropics and implementing a faster Hg+Br oxidation mechanism. Results have important implications for our understanding of global-scale atmospheric Hg chemistry and

  8. Improvement of OMI Ozone Profile Retrievals in the Troposphere and Lower Troposphere by the Use of the Tropopause-Based Ozone Profile Climatology

    Science.gov (United States)

    Bak, Juseon; Liu, X.; Wei, J.; Kim, J. H.; Chance, K.; Barnet, C.

    2011-01-01

    An advance algorithm based on the optimal estimation technique has beeen developed to derive ozone profile from GOME UV radiances and have adapted it to OMI UV radiances. OMI vertical resolution : 7-11 km in the troposphere and 10-14 km in the stratosphere. Satellite ultraviolet measurements (GOME, OMI) contain little vertical information for the small scale of ozone, especially in the upper troposphere (UT) and lower stratosphere (LS) where the sharp O3 gradient across the tropopause and large ozone variability are observed. Therefore, retrievals depend greatly on the a-priori knowledge in the UTLS

  9. Continuous generation of delayed light

    Science.gov (United States)

    Smartsev, Slava; Eger, David; Davidson, Nir; Firstenberg, Ofer

    2017-11-01

    We use a four-wave mixing process to read-out light from atomic coherence which is continuously written. The light is continuously generated after an effective delay, allowing the atomic coherence to evolve during the process. Contrary to slow-light delay, which depends on the medium optical depth, here the generation delay is determined solely by the intensive properties of the system, approaching the atomic coherence lifetime at the weak driving limit. The atomic evolution during the generation delay is further manifested in the spatial profile of the generated light due to atomic diffusion. Continuous generation of light with a long intrinsic delay can replace discrete write–read procedures when the atomic evolution is the subject of interest.

  10. Delayed radiation neuropathy

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, T.; Miyamoto, K.; Beppu, H.; Hirose, K.; Yamada, K. (Tokyo Metropolitan Neurological Hospital (Japan))

    1981-07-01

    A case of cervical plexus neuropathy was reported in association with chronic radio-dermatitis, myxedema with thyroid adenoma and epiglottic tumor. A 38-year-old man has noticed muscle weakness and wasting of the right shoulder girdle since age 33. A detailed history taking revealed a previous irradiation to the neck because of the cervical lymphadenopathy at age 10 (X-ray 3,000 rads), keroid skin change at age 19, obesity and edema since 26, and hoarseness at 34. Laryngoscopic examination revealed a tumor on the right vocal cord, diagnosed as benign papilloma by histological study. In addition, there were chronic radio-dermatitis around the neck, primary hypothyroidism with a benign functioning adenoma on the right lobe of the thyroid, the right phrenic nerve palsy and the right recurrent nerve palsy. All these lesions were considered to be the late sequellae of radiation to the neck in childhood. Other neurological signs were weakness and amyotrophy of the right shoulder girdle with patchy sensory loss, and areflexia of the right arm. Gross power was fairly well preserved in the right hand. EMG showed neurogenic changes in the tested muscles, suggesting a peripheral nerve lesion. Nerve conduction velocities were normal. No abnormal findings were revealed by myelography and spinal CT. The neurological findings of the patient were compatible with the diagnosis of middle cervical plexus palsy apparently due to late radiation effect. In the literature eight cases of post-radiation neuropathy with a long latency have been reported. The present case with the longest latency after the radiation should be included in the series of the reported cases of ''delayed radiation neuropathy.'' (author).

  11. Tropospheric temperature response to stratospheric ozone recovery in the 21st century

    Directory of Open Access Journals (Sweden)

    Y. Hu

    2011-08-01

    Full Text Available Recent simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a result of the decline of ozone depleting substances under the Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of stratospheric ozone may have significant impact on tropospheric-surface climate. Here, using multi-model results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4 models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global and annual mean magnitude of ~0.41 K for 2001–2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres, while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The global and annual mean enhancement of surface warming is about 0.16 K for 2001–2050, with maximum enhancement in the winter Arctic.

  12. The tropospheric emission spectrometer (TES) for the Earth Observing System (EOS)

    Science.gov (United States)

    Beer, R.

    1992-01-01

    In recent years, increasing concern has been expressed about Global Change - the natural and anthropogenic alteration of the Earth's environment involving global greenhouse warming and the associated climate change, urban and regional atmospheric pollution, acid deposition, regional increases in tropospheric zone, and the decrease in stratospheric ozone. A common theme among these problems is that they all involve those tropospheric trace gases which are fundamental to the biosphere-troposphere interaction, the chemistry of the free troposphere itself, and troposphere-stratosphere exchange. The chemical species involved all have spectral signatures within the near and mid infrared that can now be measured by advanced techniques of remote-sensing infrared spectroradiometry. Such a system is the Tropospheric Emission Spectrometer (TES), now in Phase B definition for the Earth Observing System (EOS) polar platforms. TES addresses these objectives by obtaining radiometrically calibrated, linewidth-limited spectral resolution, infrared spectra of the lower atmosphere using both natural thermal emission and reflected sunlight (where appropriate) in three different, but fully programmable, modes: a gobal mode, a pointed mode, and a limb-viewing mode. The goals of TES, its instrumentation, operational modes, sensitivity and data handling are discussed.

  13. A model study of ozone in the eastern Mediterranean free troposphere during MINOS (August 2001

    Directory of Open Access Journals (Sweden)

    G. J. Roelofs

    2003-01-01

    Full Text Available A coupled tropospheric chemistry-climate model is used to analyze tropospheric ozone distributions observed during the MINOS campaign in the eastern Mediterranean region (August, 2001. Modeled ozone profiles are generally in good agreement with the observations. Our analysis shows that the atmospheric dynamics in the region are strongly influenced by the occurrence of an upper tropospheric anti-cyclone, associated with the Asian summer monsoon and centered over the Tibetan Plateau. The anti-cyclone affects the chemical composition of the upper troposphere, where ozone concentrations of about 50 ppbv were measured, through advection of boundary layer air from South-East Asia. A layer between 4-6 km thickness was present beneath, containing up to 120 ppbv of ozone with substantial contributions by transport from the stratosphere and through lightning NOx. Additionally, pollutant ozone from North America was mixed in. Ozone in the lower troposphere originated mainly from the European continent. The stratospheric influence may be overestimated due to too strong vertical diffusion associated with the relatively coarse vertical resolution. The estimated tropospheric ozone column over the eastern Mediterranean is ~50 DU in summer, to which ozone from recent stratospheric origin contributes about 30%, ozone from lightning 13%, and from South-East Asia, North America and Europe about 7%, 8% and 14%, respectively, adding to a long-term hemispheric background of 25% of the column.

  14. Modeling and Observations of the Response of Tropical Tropospheric Ozone to ENSO

    Science.gov (United States)

    Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Lang, C.; Rodriquez, J. M.; Nielsen, J. E.

    2012-01-01

    The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere, Recent results have revealed an ENSO induced wave-1 anomaly in observed tropical tropospheric column ozone, This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years, An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region, We will show targeted comparisons with SHADOZ ozonesondes over these regions to provide insight into the vertical structure. Also, comparisons with NASA's Aura satellite Microwave Limb Sounder (MLS) and Tropospheric Emissions Spectrometer (TES) instruments and other appropriate data sets will be shown. In addition, the water vapor response to ENSO will be compared to help illuminate its role relative to dynamics in impacting ozone concentrations. These results indicate that the tropospheric ozone response to ENSO is potentially a very useful chemistry-climate diagnostic and should be considered in future modeling assessments.

  15. Eurotrac: a co-ordinated project for applied tropospheric research

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, P. [EUROTRAC International Scientific Secretariat, Garmisch-Partenkirchen (Germany)

    1995-12-31

    It was with the realisation that the scientific problems associated with regional air pollution could only be solved within the framework of an international interdisciplinary approach that in 1985 EUROTRAC, the European co-ordinated research project, was formed. Such an approach provides the scientific consensus necessary for the acceptance of regional air-pollution abatement measures by the countries affected. EUROTRAC is a EUREKA environmental project, studying the transport and chemical transformation of trace substances and pollutants in the troposphere. Three goals were specified the outset: (1) to increase the basic knowledge in atmospheric science, (2) to promote the technological development of sensitive, specific and fast response instruments for environmental research and development, and (3) to improve the scientific basis for taking future political decisions on environmental management in the European countries. Thus EUROTRAC was founded as a scientific project but had the specific intention that its results should be utilised in the formulation of policy. This presentation reviews the progress made towards each of the three goals and also indicates the proposed direction which a follow-on project is likely to take when EUROTRAC finishes at the end of 1995. (author)

  16. Proceedings of the heavy lift launch vehicle tropospheric effects workshop

    Energy Technology Data Exchange (ETDEWEB)

    1979-12-01

    A workshop, sponsored by the Argonne National Laboratory, on Heavy Lift Launch Vehicle (HLLV) troposheric effects was held in Chicago, Illinois, on September 12, 13, and 14, 1978. Briefings were conducted on the latest HLLV congigurations, launch schedules, and proposed fuels. The geographical, environmental, and ecological background of three proposed launch sites were presented in brief. The sites discussed were launch pads near the Kennedy Space Center (KSC), a site in the southwestern United States near Animus, New Mexico, and an ocean site just north of the equator off the coast of Ecuador. A review of past efforts in atmospheric dynamics modeling, source term prediction, atmospheric effects, cloud rise modeling, and rainout/washout effects for the Space Shuttle tropospheric effects indicated that much of the progress made in these areas has direct applicability to the HLLV. The potential pollutants from the HLLV are different and their chymical interactions with the atmosphere are more complex, but the analytical techniques developed for the Space Shuttle can be applied, with the appropriate modification, to the HLLV. Reviews were presented of the ecological baseline monitoring being performed at KSC and the plant toxicology studies being conducted at North Carolina State. Based on the proposed launch sites, the latest HLLV configuration fuel, and launch schedule, the attendees developed a lit of possible environmental issues associated with the HLLV. In addition, a list of specific recommendations for short- and long-term research to investigate, understand, and possibly mitigate the HLLV environmental impacts was developed.

  17. Water vapour and ozone profiles in the midlatitude upper troposphere

    Directory of Open Access Journals (Sweden)

    G. Vaughan

    2005-01-01

    Full Text Available We present an investigation of upper tropospheric humidity profiles measured with a standard radiosonde, the Vaisala RS80-A, and a commercial frost-point hygrometer, the Snow White. Modifications to the Snow White, to enable the mirror reflectivity and Peltier cooling current to be monitored during flight, were found to be necessary to determine when the instrument was functioning correctly; a further modification to prevent hydrometeors entering the inlet was also implemented. From 23 combined flights of an ozonesonde, radiosonde and Snow White between September 2001 and July 2002, clear agreement was found between the two humidity sensors, with a mean difference of <2% in relative humidity from 2 to 10km, and 2.2% between 10 and 13km. This agreement required a correction to the radiosonde humidity, as described by Miloshevich et al. (2001. Using this result, the dataset of 324 ozonesonde/RS80-A profiles measured from Aberystwyth between 1991 and 2002 was examined to derive statistics for the distribution of water vapour and ozone. Supersaturation with respect to ice was frequently seen at the higher levels - 24% of the time in winter between 8 and 10km. The fairly uniform distribution of relative humidity persisted to 120% in winter, but decreased rapidly above 100% in summer.

  18. Electrical discharge source for tropospheric ``ozone-rich transients''

    Science.gov (United States)

    Zahn, A.; Brenninkmeijer, C. A. M.; Crutzen, P. J.; Parrish, D. D.; Sueper, D.; Heinrich, G.; Güsten, H.; Fischer, H.; Hermann, M.; Heintzenberg, J.

    2002-11-01

    In situ trace gas (O3, NO, NO2, NOy) and ultrafine aerosol particle data from a passenger aircraft (project CARIBIC) and the NOAA WP-3D research aircraft are used to identify the origin of "ozone-rich transients" that occasionally appear in aircraft ozone data sets along flight distances of 5-80 km. Evidence of ozone import from the stratosphere, once suggested as the most likely cause, cannot be found. Our data rather reveal that the majority of the recorded ozone transients are artifacts caused by electrical discharges on the aircraft fuselage and the sample air inlet system. These discharges produce not solely O3 but also nitric oxide (NO) which rapidly reacts with O3 to form nitrogen dioxide (NO2). Further evidence is, however, provided showing that some of the less pronounced and broader O3-NO-NO2-rich transients are of atmospheric origin. We hypothesize that they are formed in an early (i.e., prelightning) phase of thunderstorms due to cold electrical discharges on the surface of charged hydrometeors. Simple considerations suggest that the amount of O3 and NO produced through these mechanisms is negligible with regard to the global tropospheric budget for the two gases.

  19. UV Lidar Receiver Analysis for Tropospheric Sensing of Ozone

    Science.gov (United States)

    Pliutau, Denis; DeYoung, Russell J.

    2013-01-01

    A simulation of a ground based Ultra-Violet Differential Absorption Lidar (UV-DIAL) receiver system was performed under realistic daytime conditions to understand how range and lidar performance can be improved for a given UV pulse laser energy. Calculations were also performed for an aerosol channel transmitting at 3 W. The lidar receiver simulation studies were optimized for the purpose of tropospheric ozone measurements. The transmitted lidar UV measurements were from 285 to 295 nm and the aerosol channel was 527-nm. The calculations are based on atmospheric transmission given by the HITRAN database and the Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological data. The aerosol attenuation is estimated using both the BACKSCAT 4.0 code as well as data collected during the CALIPSO mission. The lidar performance is estimated for both diffuseirradiance free cases corresponding to nighttime operation as well as the daytime diffuse scattered radiation component based on previously reported experimental data. This analysis presets calculations of the UV-DIAL receiver ozone and aerosol measurement range as a function of sky irradiance, filter bandwidth and laser transmitted UV and 527-nm energy

  20. Climatic effects of NOx emissions through changes in tropospheric O{sub 3} and CH{sub 4}. A global 3-D model studt

    Energy Technology Data Exchange (ETDEWEB)

    Fuglestvedt, Jan S.; Berntsen, Terje K.; Isaksen, Ivar S.A.; Mao, Huiting; Liang, Xin Zhong; Wang, Wei Chyung

    1997-12-31

    The overall objective of the work discussed in this report is to obtain more reliable estimates of the impacts of emissions of NOx from surface sources on climate through the responses in tropospheric ozone and methane. The report considers in detail how the climate impacts as quantified in terms of radiative forcing vary with geographical location of the emission changes, and it focuses on monthly mean values of ozone. It is found that, for ozone changes, the highest sensitivities to NOx reductions are calculated for Southeast Asia and Australia, while USA and Scandinavia have the lowest sensitivities. For methane, Australia and Southeast Asia are much more sensitive to NOx changes than any other region. The climatic impacts in terms of radiative forcing shows significant regional variation. The chemistry calculations show that changes in the emissions of NOx lead to changes in methane that are of opposite sign compared to the ozone response. Emissions of NOx have potentially important impacts on climate. But these impacts are very different in nature; one global methane effect with a delay of approximately a decade, while the ozone effect is of regional character with an almost instantaneous adjustment. Both mechanisms may affect climate on a hemispheric to global scale through changes in local heating rates and dynamics. It is also found that the effects of NOx emissions on ozone in the free troposphere depend on changes in the levels of gases providing the HOx precursors for ozone production. 50 refs., 23 figs., 5 tabs.

  1. Delay of Gratification and Delay Discounting: A Unifying Feedback Model of Delay-Related Impulsive Behavior

    Science.gov (United States)

    Reynolds, Brady; Schiffbauer, Ryan

    2005-01-01

    Delay of Gratification (DG) and Delay Discounting (DD) represent two indices of impulsive behavior often treated as though they represent equivalent or the same underlying processes. However, there are key differences between DG and DD procedures, and between certain research findings with each procedure, that suggest they are not equivalent. In…

  2. Changes in tropospheric composition and air quality due to stratospheric ozone depletion.

    Science.gov (United States)

    Solomon, Keith R; Tang, Xiaoyan; Wilson, Stephen R; Zanis, Prodromos; Bais, Alkiviadis F

    2003-01-01

    Increased UV-B through stratospheric ozone depletion leads to an increased chemical activity in the lower atmosphere (the troposphere). The effect of stratospheric ozone depletion on tropospheric ozone is small (though significant) compared to the ozone generated anthropogenically in areas already experiencing air pollution. Modeling and experimental studies suggest that the impacts of stratospheric ozone depletion on tropospheric ozone are different at different altitudes and for different chemical regimes. As a result the increase in ozone due to stratospheric ozone depletion may be greater in polluted regions. Attributable effects on concentrations are expected only in regions where local emissions make minor contributions. The vertical distribution of NOx (NO + NO2), the emission of volatile organic compounds and the abundance of water vapor, are important influencing factors. The long-term nature of stratospheric ozone depletion means that even a small increase in tropospheric ozone concentration can have a significant impact on human health and the environment. Trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA) are produced by the atmospheric degradation of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). TFA has been measured in rain, rivers, lakes, and oceans, the ultimate sink for these and related compounds. Significant anthropogenic sources of TFA other than degradation HCFCs and HFCs have been identified. Toxicity tests under field conditions indicate that the concentrations of TFA and CDFA currently produced by the atmospheric degradation of HFCs and HCFCs do not present a risk to human health and the environment. The impact of the interaction between ozone depletion and future climate change is complex and a significant area of current research. For air quality and tropospheric composition, a range of physical parameters such as temperature, cloudiness and atmospheric transport will modify the impact of UV-B. Changes in the

  3. Time Delay in Molecular Photoionization

    CERN Document Server

    Hockett, P; Villeneuve, D M; Corkum, P B

    2015-01-01

    Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, the time-delays expected from molecular ionization present a much richer phenomenon, with a strong spatial dependence due to the anisotropic nature of the molecular scattering potential. We investigate this from a scattering theory perspective, and make use of molecular photoionization calculations to examine this effect in representative homonuclear and hetronuclear diatomic molecules, nitrogen and carbon monoxide. We present energy and angle-resolved maps of the Wigner delay time for single-photon valence ionization, and discuss the possibilities for experimental measurements.

  4. Synoptic tracer gradients in the upper troposphere over central Canada during the Stratosphere-Troposphere Experiments by Aircraft Measurements 1998 summer campaign

    NARCIS (Netherlands)

    Fischer, H.; Brunner, D; Harris, GW; Hoor, P; Lelieveld, J; McKenna, DS; Rudolph, J; Scheeren, HA; Siegmund, P; Wernli, H; Williams, J; Wong, S

    [1] During the July 1998 Stratosphere-Troposphere Experiments by Aircraft Measurements (STREAM) intensive campaign, eight measurement flights were conducted from Timmins airport (Ontario, Canada, 48.2degreesN, 79.3degreesW). In situ measurements of ozone, carbon monoxide, carbon dioxide, and

  5. Tightly Coupled Integration of GPS Ambiguity Fixed Precise Point Positioning and MEMS-INS through a Troposphere-Constrained Adaptive Kalman Filter

    Science.gov (United States)

    Han, Houzeng; Xu, Tianhe; Wang, Jian

    2016-01-01

    Precise Point Positioning (PPP) makes use of the undifferenced pseudorange and carrier phase measurements with ionospheric-free (IF) combinations to achieve centimeter-level positioning accuracy. Conventionally, the IF ambiguities are estimated as float values. To improve the PPP positioning accuracy and shorten the convergence time, the integer phase clock model with between-satellites single-difference (BSSD) operation is used to recover the integer property. However, the continuity and availability of stand-alone PPP is largely restricted by the observation environment. The positioning performance will be significantly degraded when GPS operates under challenging environments, if less than five satellites are present. A commonly used approach is integrating a low cost inertial sensor to improve the positioning performance and robustness. In this study, a tightly coupled (TC) algorithm is implemented by integrating PPP with inertial navigation system (INS) using an Extended Kalman filter (EKF). The navigation states, inertial sensor errors and GPS error states are estimated together. The troposphere constrained approach, which utilizes external tropospheric delay as virtual observation, is applied to further improve the ambiguity-fixed height positioning accuracy, and an improved adaptive filtering strategy is implemented to improve the covariance modelling considering the realistic noise effect. A field vehicular test with a geodetic GPS receiver and a low cost inertial sensor was conducted to validate the improvement on positioning performance with the proposed approach. The results show that the positioning accuracy has been improved with inertial aiding. Centimeter-level positioning accuracy is achievable during the test, and the PPP/INS TC integration achieves a fast re-convergence after signal outages. For troposphere constrained solutions, a significant improvement for the height component has been obtained. The overall positioning accuracies of the height

  6. Tightly Coupled Integration of GPS Ambiguity Fixed Precise Point Positioning and MEMS-INS through a Troposphere-Constrained Adaptive Kalman Filter

    Directory of Open Access Journals (Sweden)

    Houzeng Han

    2016-07-01

    Full Text Available Precise Point Positioning (PPP makes use of the undifferenced pseudorange and carrier phase measurements with ionospheric-free (IF combinations to achieve centimeter-level positioning accuracy. Conventionally, the IF ambiguities are estimated as float values. To improve the PPP positioning accuracy and shorten the convergence time, the integer phase clock model with between-satellites single-difference (BSSD operation is used to recover the integer property. However, the continuity and availability of stand-alone PPP is largely restricted by the observation environment. The positioning performance will be significantly degraded when GPS operates under challenging environments, if less than five satellites are present. A commonly used approach is integrating a low cost inertial sensor to improve the positioning performance and robustness. In this study, a tightly coupled (TC algorithm is implemented by integrating PPP with inertial navigation system (INS using an Extended Kalman filter (EKF. The navigation states, inertial sensor errors and GPS error states are estimated together. The troposphere constrained approach, which utilizes external tropospheric delay as virtual observation, is applied to further improve the ambiguity-fixed height positioning accuracy, and an improved adaptive filtering strategy is implemented to improve the covariance modelling considering the realistic noise effect. A field vehicular test with a geodetic GPS receiver and a low cost inertial sensor was conducted to validate the improvement on positioning performance with the proposed approach. The results show that the positioning accuracy has been improved with inertial aiding. Centimeter-level positioning accuracy is achievable during the test, and the PPP/INS TC integration achieves a fast re-convergence after signal outages. For troposphere constrained solutions, a significant improvement for the height component has been obtained. The overall positioning accuracies

  7. Diagnosing changes in European tropospheric ozone: A model study of past and future changes

    Science.gov (United States)

    Tummon, Fiona; Revell, Laura; Stenke, Andrea; Staehelin, Johannes; Peter, Thomas

    2016-04-01

    In recent decades, the negative impacts of tropospheric ozone on human and ecosystem health have led to policy changes aimed at reducing emissions of ozone precursor gases such as nitrogen oxides (NOx) and carbon monoxide (CO). Although emissions of these species have significantly decreased in Europe and North America since the early 1990s, observational data indicate that free tropospheric ozone over Europe has not decreased as expected. Uncertainty remains as to how much of a role the transport of stratospheric ozone or tropospheric ozone from remote source regions has played in recent trends, as well as to how this will evolve in a changing climate. The global chemistry-climate model SOCOL (SOlar Chemistry Ozone Links) is used to investigate tropospheric ozone over Europe from 1960 to 2100. To fully disentangle the effects of both long-range transport and input from the stratosphere, simulations are run with ozone tracers from 21 different atmospheric regions. In addition to a standard reference run, several sensitivity simulations are run: one with emissions of NOx and CO held constant at 1960 levels, one with methane (CH4) held at constant 1960 levels (in addition to the NOx and CO), and a third with NOx and CO emissions from Asia fixed at 1960 levels. Results suggest that the largest contributions to European tropospheric ozone originate from the tropical and northern mid-latitude boundary layer and free troposphere. Contributions from these regions increase over the historical period (1960-2010), indicating that changes in source gas emissions have affected ozone concentrations in the European free troposphere most strongly. Contributions from these regions then decrease from 2010-2100, but remain considerably larger than input from the stratosphere, which is relatively small in all simulations throughout the entire simulated period (1960-2100). The stratospheric contribution does, however, increase slightly over the 21st century, in tandem with ozone

  8. Impact of Intercontinental Transport of North American Ozone on Tropospheric Ozone over East Asia

    Science.gov (United States)

    Zhu, Ye; Liu, Jane; Wang, Tijian; Zhuang, Bingliang; Han, Han; Wang, Hengmao; Chang, Yi; Ding, Ke

    2017-04-01

    Ozone is an important trace gas in the troposphere as a major pollutant and greenhouse gas. In this study, we analyzed results from a global 3-dimentional chemical transport, GEOS-Chem, which simulates ozone concentrations from different regions, tracks their transport to each of the regions and thus provides a valuable dataset to study contributions of long-range transport of ozone from different regions to East Asia. With a particular focus on the influence of North American ozone, we compared the simulations with ozonesonde measurements at two sites in USA and found the model can best capture the ozone's interannual variations in the middle and upper troposphere in the region. We also used air parcel trajectory analysis and found that North American ozone can reach the western East Asia within 4-6 days. In the middle and upper troposphere, North American ozone can influence East Asia most significantly in spring and fall. In the lower troposphere, North American ozone's influence is the largest in winter. In fall, the fractional contribution of North American ozone appears to be the largest in the lower troposphere over Europe, while in the upper troposphere it can affect most regions of Eurasia, especially above 30°N. Ozone generated from North American's boundary layer is mainly transported to the west coast of Europe with so-called warm conveyor belts associated with extratropical cyclones, and along with the westerlies to the entire northern hemisphere. It is transported to the lower troposphere with the downdraft in Europe and East Asia. The underlying mechanisms for the seasonal variation on NA ozone influences will be discussed.

  9. Evaluation of ACCMIP outgoing longwave radiation from tropospheric ozone using TES satellite observations

    Directory of Open Access Journals (Sweden)

    K. W. Bowman

    2013-04-01

    Full Text Available We use simultaneous observations of tropospheric ozone and outgoing longwave radiation (OLR sensitivity to tropospheric ozone from the Tropospheric Emission Spectrometer (TES to evaluate model tropospheric ozone and its effect on OLR simulated by a suite of chemistry-climate models that participated in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP. The ensemble mean of ACCMIP models show a persistent but modest tropospheric ozone low bias (5–20 ppb in the Southern Hemisphere (SH and modest high bias (5–10 ppb in the Northern Hemisphere (NH relative to TES ozone for 2005–2010. These ozone biases have a significant impact on the OLR. Using TES instantaneous radiative kernels (IRK, we show that the ACCMIP ensemble mean tropospheric ozone low bias leads up to 120 mW m−2 OLR high bias locally but zonally compensating errors reduce the global OLR high bias to 39 ± 41 m Wm−2 relative to TES data. We show that there is a correlation (R2 = 0.59 between the magnitude of the ACCMIP OLR bias and the deviation of the ACCMIP preindustrial to present day (1750–2010 ozone radiative forcing (RF from the ensemble ozone RF mean. However, this correlation is driven primarily by models whose absolute OLR bias from tropospheric ozone exceeds 100 m Wm−2. Removing these models leads to a mean ozone radiative forcing of 394 ± 42 m Wm−2. The mean is about the same and the standard deviation is about 30% lower than an ensemble ozone RF of 384 ± 60 m Wm−2 derived from 14 of the 16 ACCMIP models reported in a companion ACCMIP study. These results point towards a profitable direction of combining satellite observations and chemistry-climate model simulations to reduce uncertainty in ozone radiative forcing.

  10. The remote sensing of tropospheric composition from space

    Energy Technology Data Exchange (ETDEWEB)

    Burrows, John P. [Bremen Univ. (DE). Inst. fuer Umweltphysik (IUP); Platt, Ulrich [Heidelberg Univ. (Germany). Inst. fuer Umweltphysik; Borrell, Peter (eds.) [P and PMB Consultants, Newcastle-under-Lyme (United Kingdom)

    2011-07-01

    The impact of anthropogenic activities on our atmospheric environment is of growing public concern and satellite-based techniques now provide an essential component of observational strategies on regional and global scales. The purpose of this book is to summarise the state of the art in the field in general, while describing both key techniques and findings in particular. It opens with an historical perspective of the field together with the basic principles of remote sensing from space. Three chapters follow on the techniques and on the solutions to the problems associated with the various spectral regions in which observations are made. The particular challenges posed by aerosols and clouds are covered in the next two chapters. Of special importance is the accuracy and reliability of remote sensing data and these issues are covered in a chapter on validation. The final section of the book is concerned with the exploitation of data, with chapters on observational aspects, which includes both individual and synergistic studies, and on the comparison of global and regional observations with chemical transport and climate models and the added value that the interaction brings to both. The book concludes with scientific needs and likely future developments in the field, and the necessary actions to be taken if we are to have the global observation system that the Earth needs in its present, deteriorating state. The appendices provide a comprehensive list of satellite instruments, global representations of some ancillary data such as fire counts and light pollution, a list of abbreviations and acronyms, and a set of colourful timelines indicating the satellite coverage of tropospheric composition in the foreseeable future. Altogether, this book will be a timely reference and overview for anyone working at the interface of environmental, atmospheric and space sciences. (orig.)

  11. Statistics of lower tropospheric inversions over the continental United States

    Directory of Open Access Journals (Sweden)

    Y. H. Zhang

    2011-02-01

    Full Text Available The basic structure parameters of lower tropospheric inversions (LTIs have been derived from 10 years (1998–2007 of high vertical resolution (~50 m radiosonde observations over 56 United States stations. Seasonal and longitudinal variability of these parameters are presented and the formation mechanisms of LTI are also discussed. It is found that LTI seems to be a common feature over the continental United States. The LTI occurrence rates (defined as the fraction of measurements with LTI, which is calculated from the number of LTI cases divided by the number of measurements of the whole 10 years at these 56 stations vary from 3.7% to 14.5%; the averaged base heights of LTI have a range of 3–5 km above mean sea level (a.m.s.l.; the averaged thicknesses and temperature jump ranges from 420–465 m and 1.9–2.2 K, respectively. These parameters have an obvious seasonal variation. In winter, all the occurrence rates, thicknesses and temperature jumps of LTI have much larger values than those in summer. LTI occurrence rate shows an obvious west-east increasing trend in all 4 seasons. Detailed analyses reveal that dynamical instability induced by strong zonal wind shear is responsible for LTI in winter, spring and autumn; the frontal system tends to generate LTI in summer. Since the higher occurrence rate, larger temperature jump and larger thickness of LTI occur in winter, we believe strong zonal wind shear plays a more important role in the formation of LTI.

  12. Geospatial Interpolation and Mapping of Tropospheric Ozone Pollution Using Geostatistics

    Science.gov (United States)

    Kethireddy, Swatantra R.; Tchounwou, Paul B.; Ahmad, Hafiz A.; Yerramilli, Anjaneyulu; Young, John H.

    2014-01-01

    Tropospheric ozone (O3) pollution is a major problem worldwide, including in the United States of America (USA), particularly during the summer months. Ozone oxidative capacity and its impact on human health have attracted the attention of the scientific community. In the USA, sparse spatial observations for O3 may not provide a reliable source of data over a geo-environmental region. Geostatistical Analyst in ArcGIS has the capability to interpolate values in unmonitored geo-spaces of interest. In this study of eastern Texas O3 pollution, hourly episodes for spring and summer 2012 were selectively identified. To visualize the O3 distribution, geostatistical techniques were employed in ArcMap. Using ordinary Kriging, geostatistical layers of O3 for all the studied hours were predicted and mapped at a spatial resolution of 1 kilometer. A decent level of prediction accuracy was achieved and was confirmed from cross-validation results. The mean prediction error was close to 0, the root mean-standardized-prediction error was close to 1, and the root mean square and average standard errors were small. O3 pollution map data can be further used in analysis and modeling studies. Kriging results and O3 decadal trends indicate that the populace in Houston-Sugar Land-Baytown, Dallas-Fort Worth-Arlington, Beaumont-Port Arthur, San Antonio, and Longview are repeatedly exposed to high levels of O3-related pollution, and are prone to the corresponding respiratory and cardiovascular health effects. Optimization of the monitoring network proves to be an added advantage for the accurate prediction of exposure levels. PMID:24434594

  13. Geospatial Interpolation and Mapping of Tropospheric Ozone Pollution Using Geostatistics

    Directory of Open Access Journals (Sweden)

    Swatantra R. Kethireddy

    2014-01-01

    Full Text Available Tropospheric ozone (O3 pollution is a major problem worldwide, including in the United States of America (USA, particularly during the summer months. Ozone oxidative capacity and its impact on human health have attracted the attention of the scientific community. In the USA, sparse spatial observations for O3 may not provide a reliable source of data over a geo-environmental region. Geostatistical Analyst in ArcGIS has the capability to interpolate values in unmonitored geo-spaces of interest. In this study of eastern Texas O3 pollution, hourly episodes for spring and summer 2012 were selectively identified. To visualize the O3 distribution, geostatistical techniques were employed in ArcMap. Using ordinary Kriging, geostatistical layers of O3 for all the studied hours were predicted and mapped at a spatial resolution of 1 kilometer. A decent level of prediction accuracy was achieved and was confirmed from cross-validation results. The mean prediction error was close to 0, the root mean-standardized-prediction error was close to 1, and the root mean square and average standard errors were small. O3 pollution map data can be further used in analysis and modeling studies. Kriging results and O3 decadal trends indicate that the populace in Houston-Sugar Land-Baytown, Dallas-Fort Worth-Arlington, Beaumont-Port Arthur, San Antonio, and Longview are repeatedly exposed to high levels of O3-related pollution, and are prone to the corresponding respiratory and cardiovascular health effects. Optimization of the monitoring network proves to be an added advantage for the accurate prediction of exposure levels.

  14. Global impact of road traffic emissions on tropospheric ozone

    Science.gov (United States)

    Matthes, S.; Grewe, V.; Sausen, R.; Roelofs, G.-J.

    2005-10-01

    Road traffic is one of the major anthropogenic emission sectors for NOx, CO and NMHCs (non-methane hydrocarbons). We applied ECHAM4/CBM, a general circulation model coupled to a chemistry module, which includes higher hydrocarbons, to investigate the global impact of road traffic emissions on the atmosphere. Improving over previous global modelling studies, which concentrated on road traffic NOx and CO-emissions only, we assess the impact of NMHC-emissions from road traffic. It is revealed that NMHC-emissions from road traffic play a key role for the impact on ozone. They are responsible for (indirect) long-range transport of NOx from road traffic via the formation of PAN, which is not found in a simulation without NMHC emissions from road traffic. Long-range transport of NMHC-induced PAN impacts on the ozone distribution in northern hemisphere regions far away from the sources, especially in Arctic and remote maritime regions. There, during subsidence, PAN acts as a source for NOx, caused by thermal decay. Hence, ozone is produced. In July total road traffic emissions (NOx, CO and NMHCs) contribute to the zonally averaged ozone distribution by more than 12% near the surface in the northern hemisphere midlatitudes and arctic latitudes. In January road traffic emissions contribute near the surface in northern and southern extratropics more than 8%. Sensitivity studies for regional emission show that effective transport of road traffic emissions occurs mainly in the free troposphere. In tropical latitudes of America up to an altitude of 200 hPa, global road traffic emissions contribute about 4% to the ozone concentration.

  15. DELAYED PUBERTY: A LATE DIAGNOSIS

    Directory of Open Access Journals (Sweden)

    Helena Ferreira

    2017-04-01

    Discussion/Conclusion: We aimed to aware Crohn’s disease as one of the causes of pubertal and growth delay, highlighting the need for early diagnosis and therapy, in order to reach a favorable pubertal development.

  16. Delays and networked control systems

    CERN Document Server

    Hetel, Laurentiu; Daafouz, Jamal; Johansson, Karl

    2016-01-01

    This edited monograph includes state-of-the-art contributions on continuous time dynamical networks with delays. The book is divided into four parts. The first part presents tools and methods for the analysis of time-delay systems with a particular attention on control problems of large scale or infinite-dimensional systems with delays. The second part of the book is dedicated to the use of time-delay models for the analysis and design of Networked Control Systems. The third part of the book focuses on the analysis and design of systems with asynchronous sampling intervals which occur in Networked Control Systems. The last part of the book exposes several contributions dealing with the design of cooperative control and observation laws for networked control systems. The target audience primarily comprises researchers and experts in the field of control theory, but the book may also be beneficial for graduate students. .

  17. Parental Discipline and Delayed Gratification

    Science.gov (United States)

    Weller, Leonard; Berkowitz, Edith

    1975-01-01

    It was hypothesized that children brought up under coercive power would be more likely to exhibit immediate gratification, whereas children brought up under noncoercive power would be more likely to delay gratification. The hypothesis was confirmed. (Author)

  18. Fractional variational principles with delay

    Science.gov (United States)

    Baleanu, Dumitru; Maaraba Abdeljawad, Thabet; Jarad, Fahd

    2008-08-01

    The fractional variational principles within Riemann-Liouville fractional derivatives in the presence of delay are analyzed. The corresponding Euler-Lagrange equations are obtained and one example is analyzed in detail.

  19. Fractional variational principles with delay

    Energy Technology Data Exchange (ETDEWEB)

    Baleanu, Dumitru; Abdeljawad, Thabet Maaraba; Jarad, Fahd [Department of Mathematics and Computer Sciences, Faculty of Arts and Sciences, Cankaya University, 06530 Ankara (Turkey)], E-mail: dumitru@cankaya.edu.tr, E-mail: baleanu@venus.nipne.ro

    2008-08-08

    The fractional variational principles within Riemann-Liouville fractional derivatives in the presence of delay are analyzed. The corresponding Euler-Lagrange equations are obtained and one example is analyzed in detail.

  20. EAMJ Delayed April 10.indd

    African Journals Online (AJOL)

    2010-04-04

    Apr 4, 2010 ... INTRODUCTION. Breast cancer remains a leading cause of death of ... ABSTRACT. Objective: To determine the extent and nature of delayed presentation of patients .... symptomatic breast cancer: a systematic review. Lancet.

  1. Improvements to GPS Airborne Radio Occultation in the Lower Troposphere Through Implementation of the Phase Matching Method

    Science.gov (United States)

    Wang, K.-N.; Garrison, J. L.; Haase, J. S.; Murphy, B. J.

    2017-10-01

    Airborne radio occultation (ARO) is a remote sensing technique for atmospheric sounding using Global Positioning System signals received by an airborne instrument. The atmospheric refractivity profile, which depends on pressure, temperature, and water vapor, can be retrieved by measuring the signal delay due to the refractive medium through which the signal traverses. The ARO system was developed to make repeated observations within an individual meteorological event such as a tropical storm, regardless of the presence of clouds and precipitation, and complements existing observation techniques such as dropsondes and satellite remote sensing. RO systems can suffer multipath ray propagation in the lower troposphere if there are strong refractivity gradients, for example, due to a highly variable moisture distribution or a sharp boundary layer, interfering with continuous carrier phase tracking as well as complicating retrievals. The phase matching method has now been adapted for ARO and is shown to reduce negative biases in the refractivity retrieval by providing robust retrievals of bending angle in the presence of multipath. The retrieval results are presented for a flight campaign in September 2010 for Hurricane Karl in the Caribbean Sea. The accuracy is assessed through comparison with the European Centre for Medium Range Weather Forecasts Interim Reanalysis. The fractional difference in refractivity can be maintained at a standard deviation of 2% from flight level down to a height of 2 km. The phase matching method decreases the negative refractivity bias by as much as 4% over the classical geometrical optics retrieval method.

  2. Systematics in delayed neutron yields

    Energy Technology Data Exchange (ETDEWEB)

    Ohsawa, Takaaki [Kinki Univ., Higashi-Osaka, Osaka (Japan). Atomic Energy Research Inst.

    1998-03-01

    An attempt was made to reproduce the systematic trend observed in the delayed neutron yields for actinides on the basis of the five-Gaussian representation of the fission yield together with available data sets for delayed neutron emission probability. It was found that systematic decrease in DNY for heavier actinides is mainly due to decrease of fission yields of precursors in the lighter side of the light fragment region. (author)

  3. Measuring information-transfer delays.

    Directory of Open Access Journals (Sweden)

    Michael Wibral

    Full Text Available In complex networks such as gene networks, traffic systems or brain circuits it is important to understand how long it takes for the different parts of the network to effectively influence one another. In the brain, for example, axonal delays between brain areas can amount to several tens of milliseconds, adding an intrinsic component to any timing-based processing of information. Inferring neural interaction delays is thus needed to interpret the information transfer revealed by any analysis of directed interactions across brain structures. However, a robust estimation of interaction delays from neural activity faces several challenges if modeling assumptions on interaction mechanisms are wrong or cannot be made. Here, we propose a robust estimator for neuronal interaction delays rooted in an information-theoretic framework, which allows a model-free exploration of interactions. In particular, we extend transfer entropy to account for delayed source-target interactions, while crucially retaining the conditioning on the embedded target state at the immediately previous time step. We prove that this particular extension is indeed guaranteed to identify interaction delays between two coupled systems and is the only relevant option in keeping with Wiener's principle of causality. We demonstrate the performance of our approach in detecting interaction delays on finite data by numerical simulations of stochastic and deterministic processes, as well as on local field potential recordings. We also show the ability of the extended transfer entropy to detect the presence of multiple delays, as well as feedback loops. While evaluated on neuroscience data, we expect the estimator to be useful in other fields dealing with network dynamics.

  4. Language Delays in Toddlers: Information for Parents

    Science.gov (United States)

    ... Stages Listen Español Text Size Email Print Share Language Delays in Toddlers: Information for Parents Page Content ... situation or repeats scripts from TV Delays in language Delays in language are the most common types ...

  5. Tropospheric nitrogen dioxide column retrieval based on ground-based zenith-sky DOAS observations

    Science.gov (United States)

    Tack, Frederik; Hendrick, Francois; Goutail, Florence; Fayt, Caroline; Merlaud, Alexis; Pinardi, Gaia; Pommereau, Jean-Pierre; Van Roozendael, Michel

    2014-05-01

    Nitrogen dioxide (NO2) is one of the most important chemically active trace gases in the troposphere. Listed as primary pollutant, it is also a key precursor in the formation of tropospheric ozone, aerosols, and acid rain, and can contribute locally to radiative forcing. The long-term monitoring of this species is therefore of great relevance. Here we present a new method to retrieve tropospheric NO2 vertical column amounts from ground-based zenith-sky measurements of scattered sunlight. It is based on a four-step approach consisting of (1) the DOAS analysis of zenith radiance spectra using a fixed reference spectrum corresponding to low tropospheric NO2 content, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total slant column using stratospheric vertical columns measured at twilight and simulated stratospheric NO2 diurnal variation, (4) estimation of the tropospheric vertical columns by dividing the resulting tropospheric slant columns by appropriate air mass factors. The retrieval algorithm is tested on a 2 month dataset acquired from June to July 2009 by the BIRA MAX-DOAS instrument in the framework of the Cabauw (51.97° N, 4.93° E) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The tropospheric vertical column amounts derived from zenith-sky observations are compared to the vertical columns retrieved from the off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to data of a co-located SAOZ (Système d'Analyse par Observations Zénithales) spectrometer operated by LATMOS. First results show a good agreement between the different data sets with correlation coefficients and slopes close to or larger than 0.85. We observe that the main error sources arise from the uncertainties in the determination of the residual NO2 amount in the reference spectrum, the stratospheric NO2 abundance and

  6. High concentrations and photochemical fate of oxygenated hydrocarbons in the global troposphere

    Science.gov (United States)

    Singh, Hanwant B.; Kanakidou, M.; Crutzen, P. J.; Jacob, D. J.

    1995-11-01

    OXYGENATED species in the atmosphere are important sources of free radicals and are intricately linked with the fate of nitrogen oxides (NO x ), which are themselves necessary for tropospheric ozone formation1,2. With the exception of formaldehyde, oxygenated hydrocarbons have rarely been measured in the free troposphere. Here we report airborne measurements indicating the presence of high concentrations (compared to those of routinely measured C2-C6 tropospheric hydrocarbons3,4) of acetone and methanol. We use a three-dimensional model to show that acetone photochemistry provides a quantitatively significant (up to 50%) pathway for sequestering NO x in the form of peroxyacetylnitrate, a relatively unreactive temporary reservoir of NO x . Furthermore, in the dry regions of the upper troposphere, acetone can provide a large primary source of HOx (OH + HO2) radicals, resulting in increased ozone production. This surprisingly significant contribution of such oxygenated hydrocarbons to tropospheric NOx, HO x and ozone cycling is likely to be affected by their changing natural and anthropogenic emissions due to land-use change, biomass burning and alcohol-based biofuel use.

  7. Understanding the Laminar Distribution of Tropospheric Ozone from Ground-Based, Airborne, Spaceborne, and Modeling Perspectives

    Science.gov (United States)

    Newchurch, Mike; Johnson, Matthew S.; Huang, Guanyu; Kuang, Shi; Wang, Lihua; Chance, Kelly; Liu, Xiong

    2016-01-01

    Laminar ozone structure is a ubiquitous feature of tropospheric-ozone distributions resulting from dynamic and chemical atmospheric processes. Understanding the characteristics of these ozone laminae and the mechanisms responsible for producing them is important to outline the transport pathways of trace gases and to quantify the impact of different sources on tropospheric background ozone. In this study, we present a new method to detect ozone laminae to understand their climatological characteristics of occurrence frequency in terms of thickness and altitude. We employ both ground-based and airborne ozone lidar measurements and other synergistic observations and modeling to investigate the sources and mechanisms such as biomass burning transport, stratospheric intrusion, lightning-generated NOx, and nocturnal low-level jets that are responsible for depleted or enhanced tropospheric ozone layers. Spaceborne (e.g., OMI (Ozone Monitoring Instrument), TROPOMI (Tropospheric Monitoring Instrument), TEMPO (Tropospheric Emissions: Monitoring of Pollution)) measurements of these laminae will observe greater horizontal extent and lower vertical resolution than balloon-borne or lidar measurements will quantify. Using integrated ground-based, airborne, and spaceborne observations in a modeling framework affords insight into how to gain knowledge of both the vertical and horizontal evolution of these ubiquitous ozone laminae.

  8. Are there urban signatures in the tropospheric ozone column products derived from satellite measurements?

    Directory of Open Access Journals (Sweden)

    J. Kar

    2010-06-01

    Full Text Available In view of the proposed geostationary satellite missions to monitor air quality from space, it is important to first assess the capability of the current suite of satellite instruments to provide information on the urban scale pollution. We explore the possibility of detecting urban signatures in the tropospheric column ozone data derived from Total Ozone Mapping Spectrometer (TOMS/Solar Backscattered Ultraviolet (SBUV and Ozone Monitoring Instrument (OMI/Microwave Limb Sounder (MLS satellite data. We find that distinct isolated plumes of tropospheric ozone near several large and polluted cities around the world may be detected in these data sets. The ozone plumes generally correspond with the tropospheric column NO2 plumes around these cities as observed by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY instrument. Similar plumes are also seen in tropospheric mean ozone mixing ratio distribution after accounting for the surface and tropopause pressure variations. The total column ozone retrievals indicate fairly significant sensitivity to the lower troposphere over the polluted land areas, which might help explain these detections. These results indicate that ultraviolet (UV measurements may, in principle, be able to capture the urban signatures and may have implications for future missions using geostationary satellites.

  9. A cloud filtering method for microwave upper tropospheric humidity measurements

    Directory of Open Access Journals (Sweden)

    S. A. Buehler

    2007-11-01

    Full Text Available The paper presents a cloud filtering method for upper tropospheric humidity (UTH measurements at 183.31±1.00 GHz. The method uses two criteria: a viewing angle dependent threshold on the brightness temperature at 183.31±1.00 GHz, and a threshold on the brightness temperature difference between another channel and 183.31±1.00 GHz. Two different alternatives, using 183.31±3.00 GHz or 183.31±7.00 GHz as the other channel, are studied. The robustness of this cloud filtering method is demonstrated by a mid-latitudes winter case study.

    The paper then studies different biases on UTH climatologies. Clouds are associated with high humidity, therefore the possible dry bias introduced by cloud filtering is discussed and compared to the wet biases introduced by the clouds radiative effect if no filtering is done. This is done by means of a case study, and by means of a stochastic cloud database with representative statistics for midlatitude conditions.

    Both studied filter alternatives perform nearly equally well, but the alternative using 183.31±3.00 GHz as other channel is preferable, because that channel is less likely to see the Earth's surface than the one at 183.31±7.00 GHz.

    The consistent result of all case studies and for both filter alternatives is that both cloud wet bias and cloud filtering dry bias are modest for microwave data. The recommended strategy is to use the cloud filtered data as an estimate for the true all-sky UTH value, but retain the unfiltered data to have an estimate of the cloud induced uncertainty.

    The focus of the paper is on midlatitude data, since atmospheric data to test the filter for that case were readily available. The filter is expected to be applicable also to subtropical and tropical data, but should be further validated with case studies similar to the one presented here for those cases.

  10. On the impact of aircraft emitted NO{sub x} on upper troposphere photochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Wahner, A.; Rohrer, F.; Ehhalt, D.H. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Atmosphaerische Chemie

    1997-12-31

    The enhanced nitrogen oxide concentrations influence the photochemical production of ozone as well as the steady state concentrations of hydroxyl radicals, OH, in the upper troposphere. That increase is small compared to the impact of NO{sub x} from fossil fuel combustion on boundary layer ozone. A simple quasi 2-D model was used for the latitude band 40 deg - 50 deg N to analyze the reasons for that. The model includes a simplified CH{sub 4} - CO chemistry and the salient sources of upper tropospheric NO{sub x}, namely lightning, stratospheric input, aircraft emissions and fast upward transport of surface emissions. It is shown that the maximum of net O{sub 3} production and OH concentrations occur at much lower NO{sub x} mixing ratios than in the lower troposphere. (author)

  11. Western Pacific Tropospheric Ozone and Potential Vorticity: Implications for Asian Pollution

    Science.gov (United States)

    Browell, Edward V.; Newell, Reginald E.; Davis, Douglas D.; Liu, Shaw C.

    1997-01-01

    Tropospheric ozone (03) cross sections measured with lidar from a DC-8 aircraft over the western Pacific correspond closely with potential vorticity (PV). Both are transported from the middle latitude stratosphere, although this is not the only source of 03, and both have sinks in the tropical boundary layer. 03 and PV are good indicators of photochemical and transport process interactions. In summer, some Asian pollution, raised by convection to the upper troposphere, passes southward into the tropics and to the Southern Hemisphere. In winter, subsidence keeps the pollution at low altitudes where it moves over the ocean towards the Inter-Tropical Convergence Zone (ITCZ), with photochemical destruction and secondary pollutant generation occurring en route. Convection raises this modified air to the upper troposphere, where some re may enter the stratosphere. Thus winter Asian pollution may at have a smaller direct influence on the global atmosphere than it would if injected at other longitudes and seasons.

  12. IAG JWG 4.3.8: GNSS tropospheric products for Climate: Objectives and Future Plans

    Science.gov (United States)

    Pacione, Rosa; Pottiaux, Eric

    2017-04-01

    The Joint Working Group 'GNSS tropospheric products for Climate' is part of the IAG Sub-Commission 4.3 'Atmosphere Remote Sensing', which is embedded in the IAG Commission 4 'Positioning and Applications'. The main objective of the working group is to assess existing reprocessed GNSS tropospheric products, foster the development of forthcoming reprocessing activities, review and update GNSS-based product requirements and exchange format for climate and promote their use for climate research, including a possible data assimilation of GNSS troposphere products in climate models. We will describe the Term of Reference and Objectives of the Working Group. For each objective, a report of the state of the art along with its future plans will be given.

  13. Investigating Arctic Tropospheric Ozone Depletion Through a Flowing Chemical Reaction Method of Halogen Free Radical Measurement

    Science.gov (United States)

    Tackett, P. J.; Shepson, P. B.; Bottenheim, J. W.; Steffen, A.

    2008-12-01

    Arctic tropospheric halogen chemistry has been investigated through the measurement of halogen free radicals, ozone, and gaseous elemental mercury in the lower Arctic troposphere during spring 2008 in a unique sea ice surface environment onboard the research icebreaker CCGS Amundsen. Low-level ozone depletion events were observed beginning in early March, with more extensive events occurring later in the month. Bromine monoxide measurements were conducted using a new, flowing chemical reaction method in addition to established DOAS techniques, and was observed with good agreement at concentrations approaching 40 ppt during periods of significant ozone and mercury depletion. Air mass history was observed for the periods leading to depletion, suggesting a dependence on sea ice contact and ambient temperatures below -22 °C as necessary elements for the onset of halogen-induced tropospheric ozone depletion. Here we discuss our data further with the aim of better understanding how ozone depletion events are triggered.

  14. The effect of clouds on photolysis rates and ozone formation in the unpolluted troposphere

    Science.gov (United States)

    Thompson, A. M.

    1984-01-01

    The photochemistry of the lower atmosphere is sensitive to short- and long-term meteorological effects; accurate modeling therefore requires photolysis rates for trace gases which reflect this variability. As an example, the influence of clouds on the production of tropospheric ozone has been investigated, using a modification of Luther's two-stream radiation scheme to calculate cloud-perturbed photolysis rates in a one-dimensional photochemical transport model. In the unpolluted troposphere, where stratospheric inputs of odd nitrogen appear to represent the photochemical source of O3, strong cloud reflectance increases the concentration of NO in the upper troposphere, leading to greatly enhanced rates of ozone formation. Although the rate of these processes is too slow to verify by observation, the calculation is useful in distinguishing some features of the chemistry of regions of differing mean cloudiness.

  15. Impact of Tropospheric Aerosol Absorption on Ozone Retrieval from buv Measurements

    Science.gov (United States)

    Torres, O.; Bhartia, P. K.

    1998-01-01

    The impact of tropospheric aerosols on the retrieval of column ozone amounts using spaceborne measurements of backscattered ultraviolet radiation is examined. Using radiative transfer calculations, we show that uv-absorbing desert dust may introduce errors as large as 10% in ozone column amount, depending on the aerosol layer height and optical depth. Smaller errors are produced by carbonaceous aerosols that result from biomass burning. Though the error is produced by complex interactions between ozone absorption (both stratospheric and tropospheric), aerosol scattering, and aerosol absorption, a surprisingly simple correction procedure reduces the error to about 1%, for a variety of aerosols and for a wide range of aerosol loading. Comparison of the corrected TOMS data with operational data indicates that though the zonal mean total ozone derived from TOMS are not significantly affected by these errors, localized affects in the tropics can be large enough to seriously affect the studies of tropospheric ozone that are currently undergoing using the TOMS data.

  16. Deuterium excess in subtropical free troposphere water vapor: Continuous measurements from the Chajnantor Plateau, northern Chile

    Science.gov (United States)

    Samuels-Crow, Kimberly E.; Galewsky, Joseph; Sharp, Zachary D.; Dennis, Kate J.

    2014-12-01

    Water vapor measured continuously by cavity ring-down spectroscopy from July 2012 to March 2013 on the hyperarid Chajnantor Plateau, northern Chile (elevation = 5080 m, pressure ≈ 550 hPa), has a mean deuterium excess (d-excess = δD - 8*δ18O) of 46‰ ± 5‰ and frequently exceeds 100‰ at low water vapor mixing ratios (q ≤ 500 ppmv). These measurements provide empirical support for theoretical predictions of free troposphere d-excess. The d-excess measured at this site can be understood in terms of supersaturation with respect to ice at relative humidities between 100% and 130%, followed by mixing with moist midtropospheric or lower tropospheric air en route to the plateau. The d-excess measured at Chajnantor is consistent with predictions for d-excess in the upper troposphere from isotope-enabled general circulation models and with high vapor saturation over ice in cloud-resolving and microphysical models.

  17. Photo-tautomerization of acetaldehyde to vinyl alcohol: a potential route to tropospheric acids.

    Science.gov (United States)

    Andrews, Duncan U; Heazlewood, Brianna R; Maccarone, Alan T; Conroy, Trent; Payne, Richard J; Jordan, Meredith J T; Kable, Scott H

    2012-09-07

    Current atmospheric models underestimate the production of organic acids in the troposphere. We report a detailed kinetic model of the photochemistry of acetaldehyde (ethanal) under tropospheric conditions. The rate constants are benchmarked to collision-free experiments, where extensive photo-isomerization is observed upon irradiation with actinic ultraviolet radiation (310 to 330 nanometers). The model quantitatively reproduces the experiments and shows unequivocally that keto-enol photo-tautomerization, forming vinyl alcohol (ethenol), is the crucial first step. When collisions at atmospheric pressure are included, the model quantitatively reproduces previously reported quantum yields for photodissociation at all pressures and wavelengths. The model also predicts that 21 ± 4% of the initially excited acetaldehyde forms stable vinyl alcohol, a known precursor to organic acid formation, which may help to account for the production of organic acids in the troposphere.

  18. Monitoring the distribution of tropospheric ozone concentration over Pakistan by using OMI/MLS satellite observations

    Science.gov (United States)

    Noreen, Asma; Fahim Khokhar, Muhammad; Murtaza, Rabbia; Zeb, Naila

    2016-07-01

    Pakistan is a semi-arid, agricultural country located in Indian Sub-continent, Asia. Due to exponential population growth, poor control and regulatory measures and practices in industries, it is facing a major problem of air pollution. The concentration of greenhouse gases and aerosols are showing an increasing trend in general. One of these greenhouse gases is tropospheric ozone, one of the criteria pollutant, which has a radiative forcing (RF) of about 0.4 ± 0.2 Wm-2, contributing about 14% of the present total RF. Spatial distribution and temporal evolution of tropospheric ozone concentration over Pakistan during 2004 to 2014 was studied by using combined OMI/MLS product, which was derived by tropospheric ozone residual (TOR) method. Results showed an overall increase of 3.2 ± 2.2 DU in tropospheric ozone concentration over Pakistan since October 2004. The mean spatial distribution showed high concentrations of ozone in the Punjab and southern Sindh where there is high population densities along with rapid urbanization and enhanced anthropogenic activities. The seasonal variations were observed in the provinces of the country and TO3 VCDs were found to be high during summer while minimum during winter. The statistical analysis by using seasonal Mann Kendal test also showed strong positive trends over the four provinces as well as in major cities of Pakistan. These variations were driven by various factors such as seasonality in UV-B fluxes, seasonality in ozone precursor gases such as NOx and VOCs and agricultural fire activities in Pakistan. A strong correlation of 97% was found between fire events and tropospheric ozone concentration over the country. The results also depicted the influence of UV-B radiations on the tropospheric ozone concentration over different regions of Pakistan especially in Baluchistan and Sindh provinces.

  19. Budget of tropospheric ozone during TOPSE from two chemical transport models

    Science.gov (United States)

    Emmons, L. K.; Hess, P.; Klonecki, A.; Tie, X.; Horowitz, L.; Lamarque, J.-F.; Kinnison, D.; Brasseur, G.; Atlas, E.; Browell, E.; Cantrell, C.; Eisele, F.; Mauldin, R. L.; Merrill, J.; Ridley, B.; Shetter, R.

    2003-04-01

    The tropospheric ozone budget during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign has been studied using two chemical transport models (CTMs): HANK and the Model of Ozone and Related chemical Tracers, version 2 (MOZART-2). The two models have similar chemical schemes but use different meteorological fields, with HANK using MM5 (Pennsylvania State University, National Center for Atmospheric Research Mesoscale Modeling System) and MOZART-2 driven by European Centre for Medium-Range Weather Forecasts (ECMWF) fields. Both models simulate ozone in good agreement with the observations but underestimate NOx. The models indicate that in the troposphere, averaged over the northern middle and high latitudes, chemical production of ozone drives the increase of ozone seen in the spring. Both ozone gross chemical production and loss increase greatly over the spring months. The in situ production is much larger than the net stratospheric input, and the deposition and horizontal fluxes are relatively small in comparison to chemical destruction. The net production depends sensitively on the concentrations of H2O, HO2 and NO, which differ slightly in the two models. Both models underestimate the chemical production calculated in a steady state model using TOPSE measurements, but the chemical loss rates agree well. Measures of the stratospheric influence on tropospheric ozone in relation to in situ ozone production are discussed. Two different estimates of the stratospheric fraction of O3 in the Northern Hemisphere troposphere indicate it decreases from 30-50% in February to 15-30% in June. A sensitivity study of the effect of a perturbation in the vertical flux on tropospheric ozone indicates the contribution from the stratosphere is approximately 15%.

  20. Estimating Stratospheric and Tropospheric BrO columns using GEOSCCM and the Ozone Monitoring Instrument

    Science.gov (United States)

    Liang, Q.; Chance, K.; Suleiman, R. M.; Zhang, Y.

    2013-12-01

    Atmospheric BrO is an important gas - despite its very low abundance of parts per trillion, and it plays an important chemical role in the destruction of ozone in the troposphere and the stratosphere. The current atmospheric BrO abundance estimates are highly uncertain due to significant uncertainties in the contribution of very-short-lived (VSL) bromocarbons, in contrast to the well-quantified contribution from the long-lived bromine-containing compounds, i.e. Halons and CH3Br. This is particularly true in the troposphere with various measurements suggesting the presence of a global background BrO from 0.5 ppt to 2 ppt, and, locally, BrO can be as high as 30 ppt in the Arctic and Antarctic marine boundary layer. We will run a 10-year model simulation between 2001-2010 using the NASA GEOS Chemistry Climate Model (GEOSCCM) V2 which contains a detailed stratospheric chemistry coupled with an interactive VSL bromocarbon chemistry. BrO in the troposphere will be relaxed to monthly mean BrO fields previously archived during a GEOS-Chem full chemistry simulation. The simulated VSL bromocarbons and BrO from both models have been extensively evaluated and compare well with aircraft, balloon-borne and GOME-2 satellite observations. We will analyze the model simulated BrO together with satellite BrO measurements from the Ozone Monitoring Instrument (OMI) to address the following three questions: 1) How much BrO is present in the stratosphere and the troposphere? 2) What is the relative contribution of the stratosphere and the troposphere to total atmospheric BrO column abundance? 3) What drives the seasonal and geographical variability of stratospheric and tropospheric BrO columns?

  1. An Observationally Constrained Evaluation of the Oxidative Capacity in the Tropical Western Pacific Troposphere

    Science.gov (United States)

    Nicely, Julie M.; Anderson, Daniel C.; Canty, Timothy P.; Salawitch, Ross J.; Wolfe, Glenn M.; Apel, Eric C.; Arnold, Steve R.; Atlas, Elliot L.; Blake, Nicola J.; Bresch, James F.; hide

    2016-01-01

    Hydroxyl radical (OH) is the main daytime oxidant in the troposphere and determines the atmospheric lifetimes of many compounds. We use aircraft measurements of O3, H2O, NO, and other species from the Convective Transport of Active Species in the Tropics (CONTRAST) field campaign, which occurred in the tropical western Pacific (TWP) during January-February 2014, to constrain a photochemical box model and estimate concentrations of OH throughout the troposphere. We find that tropospheric column OH (OHCOL) inferred from CONTRAST observations is 12 to 40% higher than found in chemical transport models (CTMs), including CAM-chem-SD run with 2014 meteorology as well as eight models that participated in POLMIP (2008 meteorology). Part of this discrepancy is due to a clear-sky sampling bias that affects CONTRAST observations; accounting for this bias and also for a small difference in chemical mechanism results in our empirically based value of OHCOL being 0 to 20% larger than found within global models. While these global models simulate observed O3 reasonably well, they underestimate NOx (NO +NO2) by a factor of 2, resulting in OHCOL approx.30% lower than box model simulations constrained by observed NO. Underestimations by CTMs of observed CH3CHO throughout the troposphere and of HCHO in the upper troposphere further contribute to differences between our constrained estimates of OH and those calculated by CTMs. Finally, our calculations do not support the prior suggestion of the existence of a tropospheric OH minimum in the TWP, because during January-February 2014 observed levels of O3 and NO were considerably larger than previously reported values in the TWP.

  2. Active and Widespread Halogen Chemistry in the Tropical and Subtropical Free Troposphere

    Science.gov (United States)

    Wang, Siyuan; Schmidt, Johan A.; Baidar, Sunil; Coburn, Sean; Dix, Barbara; Koenig, Theodore K.; Apel, Eric; Bowdalo, Dene; Campos, Teresa; Eloranta, Ed; hide

    2015-01-01

    Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10degN to 40degS), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (approx.3.4 pptv at 13.5 km), and are 2-4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5-6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

  3. Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury

    Directory of Open Access Journals (Sweden)

    J. P. Parrella

    2012-08-01

    Full Text Available We present a new model for the global tropospheric chemistry of inorganic bromine (Bry coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM. Sources of tropospheric Bry include debromination of sea-salt aerosol, photolysis and oxidation of short-lived bromocarbons, and transport from the stratosphere. Comparison to a GOME-2 satellite climatology of tropospheric BrO columns shows that the model can reproduce the observed increase of BrO with latitude, the northern mid-latitudes maximum in winter, and the Arctic maximum in spring. This successful simulation is contingent on the HOBr + HBr reaction taking place in aqueous aerosols and ice clouds. Bromine chemistry in the model decreases tropospheric ozone mixing ratios by <1–8 nmol mol−1 (6.5% globally, with the largest effects in the northern extratropics in spring. The global mean tropospheric OH concentration decreases by 4%. Inclusion of bromine chemistry improves the ability of global models (GEOS-Chem and p-TOMCAT to simulate observed 19th-century ozone and its seasonality. Bromine effects on tropospheric ozone are comparable in the present-day and pre-industrial atmospheres so that estimates of anthropogenic radiative forcing are minimally affected. Br atom concentrations are 40% higher in the pre-industrial atmosphere due to lower ozone, which would decrease by a factor of 2 the atmospheric lifetime of elemental mercury against oxidation by Br. This suggests that historical anthropogenic mercury emissions may have mostly deposited to northern mid-latitudes, enriching the corresponding surface reservoirs. The persistent rise in background surface ozone at northern mid-latitudes during the past decades could possibly contribute to the observations of elevated mercury in subsurface waters of the North Atlantic.

  4. An observationally constrained evaluation of the oxidative capacity in the tropical western Pacific troposphere

    Science.gov (United States)

    Nicely, Julie M.; Anderson, Daniel C.; Canty, Timothy P.; Salawitch, Ross J.; Wolfe, Glenn M.; Apel, Eric C.; Arnold, Steve R.; Atlas, Elliot L.; Blake, Nicola J.; Bresch, James F.; Campos, Teresa L.; Dickerson, Russell R.; Duncan, Bryan; Emmons, Louisa K.; Evans, Mathew J.; Fernandez, Rafael P.; Flemming, Johannes; Hall, Samuel R.; Hanisco, Thomas F.; Honomichl, Shawn B.; Hornbrook, Rebecca S.; Huijnen, Vincent; Kaser, Lisa; Kinnison, Douglas E.; Lamarque, Jean-Francois; Mao, Jingqiu; Monks, Sarah A.; Montzka, Denise D.; Pan, Laura L.; Riemer, Daniel D.; Saiz-Lopez, Alfonso; Steenrod, Stephen D.; Stell, Meghan H.; Tilmes, Simone; Turquety, Solene; Ullmann, Kirk; Weinheimer, Andrew J.

    2016-06-01

    Hydroxyl radical (OH) is the main daytime oxidant in the troposphere and determines the atmospheric lifetimes of many compounds. We use aircraft measurements of O3, H2O, NO, and other species from the Convective Transport of Active Species in the Tropics (CONTRAST) field campaign, which occurred in the tropical western Pacific (TWP) during January-February 2014, to constrain a photochemical box model and estimate concentrations of OH throughout the troposphere. We find that tropospheric column OH (OHCOL) inferred from CONTRAST observations is 12 to 40% higher than found in chemical transport models (CTMs), including CAM-chem-SD run with 2014 meteorology as well as eight models that participated in POLMIP (2008 meteorology). Part of this discrepancy is due to a clear-sky sampling bias that affects CONTRAST observations; accounting for this bias and also for a small difference in chemical mechanism results in our empirically based value of OHCOL being 0 to 20% larger than found within global models. While these global models simulate observed O3 reasonably well, they underestimate NOx (NO + NO2) by a factor of 2, resulting in OHCOL ~30% lower than box model simulations constrained by observed NO. Underestimations by CTMs of observed CH3CHO throughout the troposphere and of HCHO in the upper troposphere further contribute to differences between our constrained estimates of OH and those calculated by CTMs. Finally, our calculations do not support the prior suggestion of the existence of a tropospheric OH minimum in the TWP, because during January-February 2014 observed levels of O3 and NO were considerably larger than previously reported values in the TWP.

  5. Summertime tropospheric ozone variability over the Mediterranean basin observed with IASI

    Science.gov (United States)

    Doche, C.; Dufour, G.; Foret, G.; Eremenko, M.; Cuesta, J.; Beekmann, M.; Kalabokas, P.

    2014-05-01

    The Mediterranean basin is one of the most sensitive regions of the world regarding climate change and air quality. This is partly due to the singular dynamical situation of the Mediterranean basin that leads to among the highest tropospheric ozone concentrations over the Northern Hemisphere. Six years of summertime tropospheric ozone observed by the IASI instrument from 2007 to 2012 have been analysed to document the variability of ozone over this region. The satellite observations have been also examined in parallel with meteorological analyses (from ECMWF) to understand the processes that drive this variability. This work confirmed the presence of a steep west-east ozone gradient in the lower troposphere with the highest concentrations observed over the eastern part of the Mediterranean basin. This gradient is mainly explained by the diabatic convection over the Persian Gulf during the Indian Monsoon, which induces an important subsidence of ozone rich air masses from the upper to the lower troposphere over the central and the eastern Mediterranean basin: IASI observations of ozone concentrations at 3 km height show a clear summertime maximum in July that is well correlated to the maximum of downward transport of rich-ozone air masses from the upper troposphere. Even if this feature is robust over the six analyzed years, we have also investigated monthly ozone anomalies, one positive (June 2008) and one negative (June and July 2009) using daily observations of IASI. We show that the relative position and the strength of the meteorological systems (Azores anticyclone and Middle eastern depression) present over the Mediterranean are key factors to explain both the variability and the anomalies of ozone in the lower troposphere in this region.

  6. Summertime tropospheric-ozone variability over the Mediterranean basin observed with IASI

    Science.gov (United States)

    Doche, C.; Dufour, G.; Foret, G.; Eremenko, M.; Cuesta, J.; Beekmann, M.; Kalabokas, P.

    2014-10-01

    The Mediterranean basin is one of the most sensitive regions in the world regarding climate change and air quality. This is partly due to the singular dynamical situation of the Mediterranean basin that leads to tropospheric-ozone concentrations that are among the highest over the Northern Hemisphere. Six years of summertime tropospheric ozone observed by the Infrared Atmospheric Sounding Interferometer (IASI) instrument from 2007 to 2012 have been analysed to document the variability of ozone over this region. The satellite observations have been examined together with meteorological analyses (from ECMWF) to understand the processes driving this variability. Our work confirmed the presence of a steep west-east ozone gradient in the lower troposphere with the highest concentrations observed over the eastern part of the Mediterranean basin. This gradient is mainly explained by diabatic convection over the Persian Gulf during the Indian monsoon season, which induces an important subsidence of ozone-rich air masses from the upper to the lower troposphere over the central and the eastern Mediterranean basin. IASI observations of ozone concentrations at a 3 km height show a clear summertime maximum in July that is well correlated to the maximum of downward transport of ozone-rich air masses from the upper troposphere. Even if this feature is robust over the six analysed years, we have also investigated monthly ozone anomalies - one positive (June 2008) and one negative (June and July 2009) - using daily IASI observations. We show that the relative position and the strength of the meteorological systems (Azores anticyclone and Middle Eastern depression) present over the Mediterranean are key factors in explaining both the variability and the anomalies of ozone in the lower troposphere in this region.

  7. Stochastic modelling of train delays and delay propagation in stations

    NARCIS (Netherlands)

    Yuan, J.

    2006-01-01

    A trade-off exists between efficiently utilizing the capacity of railway networks and improving the reliability and punctuality of train operations. This dissertation presents a new analytical probability model based on blocking time theory which estimates the knock-on delays of trains caused by

  8. Satellite remote sensing of tropospheric composition – principles, results, and challenges

    Directory of Open Access Journals (Sweden)

    Richter A.

    2010-12-01

    Full Text Available Over the last years, satellite observations of tropospheric composition have become an important data source for atmospheric chemistry and air pollution applications. Most of these measurements are performed using passive remote sensing in the UV, visible and IR spectral regions. The choice of wavelengths used determines the species that can be retrieved but also the vertical sensitivity and resolution of the measurements. Here, a brief introduction into space-borne remote sensing of the troposphere is given, a few typical examples are discussed and an outlook to future developments is given.

  9. The EOS AURA Tropospheric Emission Spectrometer (TES): Status of the Program

    Science.gov (United States)

    Beer, Reinhard

    2005-01-01

    This slide presentation is a programmatic overview covering some of the highlights of the mission and serve as an introduction to the accompanying presentations at the workshop. It reviews the goals and the products of the TES experiment, a simplified chemistry of ozone in both the stratosphere and troposphere, a description of the instrument, and the TES operational modes. Included are graphs showing some of the results of TES analysis of the key constituents of the tropospheric chemistry and the inter-regional transport.

  10. TOLNET – A Tropospheric Ozone Lidar Profiling Network for Satellite Continuity and Process Studies

    Directory of Open Access Journals (Sweden)

    Newchurch Michael J.

    2016-01-01

    Full Text Available Ozone lidars measure continuous, high-resolution ozone profiles critical for process studies and for satellite validation in the lower troposphere. However, the effectiveness of lidar validation by using single-station data is limited. Recently, NASA initiated an interagency ozone lidar observation network under the name TOLNet to promote cooperative multiple-station ozone-lidar observations to provide highly timeresolved (few minutes tropospheric-ozone vertical profiles useful for air-quality studies, model evaluation, and satellite validation. This article briefly describes the concept, stations, major specifications of the TOLNet instruments, and data archiving.

  11. Mars Reconnaissance Orbiter: Ka Band Radio Science Experiments and the Effect of the Troposphere

    Science.gov (United States)

    Asmar, Sami W.; Morabito, David

    2006-01-01

    This viewgraph presentation reviews the possibilities of utilizing the telecommunication links between spacecraft and Earth to examine changes in the phase/frequency, amplitude, and polarization of radio signals to investigate, specifically for the Mars Reconnaissance Orbiter (MRO)mission utilizes X-band coherent (uplink and downlink) carrier Doppler and range for its gravity investigation Gravity team will also take advantage of Ka-band downlink signal Tropospheric calibration data from Advanced Water Vapor Radiometer (AWVR) will be used. The calibration of the received Ka band signal for the effect of the troposphere is discussed.

  12. Detection of stratosphere troposphere exchange in cut-off low systems

    Science.gov (United States)

    Price, Jeremy D.; Vaughan, Geraint

    1994-01-01

    The Aberystwyth MST radar has been used as part of the TOASTE program to study the structure of the tropopause in cut-off-low system with an aim to identifying regions where stratosphere-troposphere exchange are taking place. Theory predicts that the vertical gradient in reflected power is proportional to the static stability of the reflecting region, and should therefore resolve tropopause structure. Comparisons of MST power profiles with radiosonde data are presented and show good agreement, revealing regions of indefinite tropopauses, where stratosphere-troposphere exchange is thought to take place. The continuous nature of MST data allows an estimation of the size of these regions.

  13. Mid-latitude tropospheric ozone columns from the MOZAIC program: climatology and interannual variability

    Directory of Open Access Journals (Sweden)

    R. M. Zbinden

    2006-01-01

    Full Text Available Several thousands of ozone vertical profiles collected in the course of the MOZAIC programme (Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft from August 1994 to February 2002 are investigated to bring out climatological and interannual variability aspects. The study is centred on the most frequently visited MOZAIC airports, i.e. Frankfurt (Germany, Paris (France, New York (USA and the cluster of Tokyo, Nagoya and Osaka (Japan. The analysis focuses on the vertical integration of ozone from the ground to the dynamical tropopause and the vertical integration of stratospheric-origin ozone throughout the troposphere. The characteristics of the MOZAIC profiles: frequency of flights, accuracy, precision, and depth of the troposphere observed, are presented. The climatological analysis shows that the Tropospheric Ozone Column (TOC seasonal cycle ranges from a wintertime minimum at all four stations to a spring-summer maximum in Frankfurt, Paris, and New York. Over Japan, the maximum occurs in spring presumably because of the earlier springtime sun. The incursion of monsoon air masses into the boundary layer and into the mid troposphere then steeply diminishes the summertime value. Boundary layer contributions to the TOC are 10% higher in New York than in Frankfurt and Paris during spring and summer, and are 10% higher in Japan than in New York, Frankfurt and Paris during autumn and early spring. Local and remote anthropogenic emissions, and biomass burning over upstream regions of Asia may be responsible for the larger low- and mid-tropospheric contributions to the tropospheric ozone column over Japan throughout the year except during the summer-monsoon season. A simple Lagrangian analysis has shown that a minimum of 10% of the TOC is of stratospheric-origin throughout the year. Investigation of the short-term trends of the TOC over the period 1995–2001 shows a linear increase 0.7%/year in

  14. Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

    Science.gov (United States)

    Greenslade, Jesse W.; Alexander, Simon P.; Schofield, Robyn; Fisher, Jenny A.; Klekociuk, Andrew K.

    2017-09-01

    Stratosphere-to-troposphere transport (STT) provides an important natural source of ozone to the upper troposphere, but the characteristics of STT events in the Southern Hemisphere extratropics and their contribution to the regional tropospheric ozone budget remain poorly constrained. Here, we develop a quantitative method to identify STT events from ozonesonde profiles. Using this method we estimate the seasonality of STT events and quantify the ozone transported across the tropopause over Davis (69° S, 2006-2013), Macquarie Island (54° S, 2004-2013), and Melbourne (38° S, 2004-2013). STT seasonality is determined by two distinct methods: a Fourier bandpass filter of the vertical ozone profile and an analysis of the Brunt-Väisälä frequency. Using a bandpass filter on 7-9 years of ozone profiles from each site provides clear detection of STT events, with maximum occurrences during summer and minimum during winter for all three sites. The majority of tropospheric ozone enhancements owing to STT events occur within 2.5 and 3 km of the tropopause at Davis and Macquarie Island respectively. Events are more spread out at Melbourne, occurring frequently up to 6 km from the tropopause. The mean fraction of total tropospheric ozone attributed to STT during STT events is ˜ 1. 0-3. 5 % at each site; however, during individual events, over 10 % of tropospheric ozone may be directly transported from the stratosphere. The cause of STTs is determined to be largely due to synoptic low-pressure frontal systems, determined using coincident ERA-Interim reanalysis meteorological data. Ozone enhancements can also be caused by biomass burning plumes transported from Africa and South America, which are apparent during austral winter and spring and are determined using satellite measurements of CO. To provide regional context for the ozonesonde observations, we use the GEOS-Chem chemical transport model, which is too coarsely resolved to distinguish STT events but is able to

  15. Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

    Directory of Open Access Journals (Sweden)

    J. W. Greenslade

    2017-09-01

    Full Text Available Stratosphere-to-troposphere transport (STT provides an important natural source of ozone to the upper troposphere, but the characteristics of STT events in the Southern Hemisphere extratropics and their contribution to the regional tropospheric ozone budget remain poorly constrained. Here, we develop a quantitative method to identify STT events from ozonesonde profiles. Using this method we estimate the seasonality of STT events and quantify the ozone transported across the tropopause over Davis (69° S, 2006–2013, Macquarie Island (54° S, 2004–2013, and Melbourne (38° S, 2004–2013. STT seasonality is determined by two distinct methods: a Fourier bandpass filter of the vertical ozone profile and an analysis of the Brunt–Väisälä frequency. Using a bandpass filter on 7–9 years of ozone profiles from each site provides clear detection of STT events, with maximum occurrences during summer and minimum during winter for all three sites. The majority of tropospheric ozone enhancements owing to STT events occur within 2.5 and 3 km of the tropopause at Davis and Macquarie Island respectively. Events are more spread out at Melbourne, occurring frequently up to 6 km from the tropopause. The mean fraction of total tropospheric ozone attributed to STT during STT events is  ∼ 1. 0–3. 5 % at each site; however, during individual events, over 10 % of tropospheric ozone may be directly transported from the stratosphere. The cause of STTs is determined to be largely due to synoptic low-pressure frontal systems, determined using coincident ERA-Interim reanalysis meteorological data. Ozone enhancements can also be caused by biomass burning plumes transported from Africa and South America, which are apparent during austral winter and spring and are determined using satellite measurements of CO. To provide regional context for the ozonesonde observations, we use the GEOS-Chem chemical transport model, which is too coarsely

  16. Contributions of the troposphere and stratosphere to CH4 model biases

    Directory of Open Access Journals (Sweden)

    Z. Wang

    2017-11-01

    Full Text Available Inverse modelling is a useful tool for retrieving CH4 fluxes; however, evaluation of the applied chemical transport model is an important step before using the inverted emissions. For inversions using column data one concern is how well the model represents stratospheric and tropospheric CH4 when assimilating total column measurements. In this study atmospheric CH4 from three inverse models is compared to FTS (Fourier transform spectrometry, satellite and in situ measurements. Using the FTS measurements the model biases are separated into stratospheric and tropospheric contributions. When averaged over all FTS sites the model bias amplitudes (absolute model to FTS differences are 7.4 ± 5.1, 6.7 ± 4.8, and 8.1 ± 5.5 ppb in the tropospheric partial column (the column from the surface to the tropopause for the models TM3, TM5-4DVAR, and LMDz-PYVAR, respectively, and 4.3 ± 9.9, 4.7 ± 9.9, and 6.2 ± 11.2 ppb in the stratospheric partial column (the column from the tropopause to the top of the atmosphere. The model biases in the tropospheric partial column show a latitudinal gradient for all models; however there are no clear latitudinal dependencies for the model biases in the stratospheric partial column visible except with the LMDz-PYVAR model. Comparing modelled and FTS-measured tropospheric column-averaged mole fractions reveals a similar latitudinal gradient in the model biases but comparison with in situ measured mole fractions in the troposphere does not show a latitudinal gradient, which is attributed to the different longitudinal coverage of FTS and in situ measurements. Similarly, a latitudinal pattern exists in model biases in vertical CH4 gradients in the troposphere, which indicates that vertical transport of tropospheric CH4 is not represented correctly in the models.

  17. Justice Delayed is Justice Denied

    Directory of Open Access Journals (Sweden)

    Naomi Burstyner

    2014-10-01

    Full Text Available This paper explores issues in the justice system that are related to timeliness and its interconnectedness to the definition of delay, whilst considering the impact of delay on the experience of the justice system user.Historical acknowledgements recognise the perspective of the accused or the disputant, and suggest that for a person seeking justice, the time taken for resolution of their issue is critical to the justice experience of this person and can render their treatment wholly ‘unjust’ in circumstances where closure takes ‘too long’.

  18. 49 CFR 236.563 - Delay time.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Delay time. 236.563 Section 236.563 Transportation... Cab Signal Systems Rules and Instructions; Locomotives § 236.563 Delay time. Delay time of automatic... requirements of § 236.24 shall take into consideration the delay time. ...

  19. Water vapour variability in the high-latitude upper troposphere – Part 2: Impact of volcanic eruptions

    Directory of Open Access Journals (Sweden)

    C. E. Sioris

    2016-02-01

    Full Text Available The impact of volcanic eruptions on water vapour in the high-latitude upper troposphere is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation and the Fourier Transform Spectrometer (ACE-FTS. The two eruptions with the greatest impact on the high-latitude upper troposphere during the time frame of this satellite-based remote sensing mission are chosen. The Puyehue–Cordón Caulle volcanic eruption in June 2011 was the most explosive in the past 24 years and is shown to be able to account for the observed (50 ± 12 % increase in water vapour in the southern high-latitude upper troposphere in July 2011 after a minor adjustment for the simultaneous influence of the Antarctic oscillation. Eyjafjallajökull erupted in the spring of 2010, increasing water vapour in the upper troposphere at northern high latitudes significantly for a period of  ∼  1 month. These findings imply that extratropical volcanic eruptions in windy environments can lead to significant perturbations to high-latitude upper tropospheric humidity mostly due to entrainment of lower tropospheric moisture by wind-blown plumes. The Puyehue–Cordón Caulle eruption must be taken into account to properly determine the magnitude of the trend in southern high-latitude upper tropospheric water vapour over the last decade.

  20. Model study of the influence of cross-tropopause O3 transports on tropospheric O3 levels

    NARCIS (Netherlands)

    Roelofs, G.J.; Lelieveld, J.

    1997-01-01

    Cross-tropopause transport of O3 is a significant factor in the tropospheric budget and distribution of O3. Nevertheless, the distribution in the troposphere of O3 that originates from the stratosphere is uncertain. We study this with a chemistry - general circulation model with relatively high

  1. Tropospheric profiles of wet refractivity and humidity from the combination of remote sensing data sets and measurements on the ground

    Directory of Open Access Journals (Sweden)

    F. Hurter

    2013-11-01

    Full Text Available We reconstruct atmospheric wet refractivity profiles for the western part of Switzerland with a least-squares collocation approach from data sets of (a zenith path delays that are a byproduct of the GPS (global positioning system processing, (b ground meteorological measurements, (c wet refractivity profiles from radio occultations whose tangent points lie within the study area, and (d radiosonde measurements. Wet refractivity is a parameter partly describing the propagation of electromagnetic waves and depends on the atmospheric parameters temperature and water vapour pressure. In addition, we have measurements of a lower V-band microwave radiometer at Payerne. It delivers temperature profiles at high temporal resolution, especially in the range from ground to 3000 m a.g.l., though vertical information content decreases with height. The temperature profiles together with the collocated wet refractivity profiles provide near-continuous dew point temperature or relative humidity profiles at Payerne for the study period from 2009 to 2011. In the validation of the humidity profiles, we adopt a two-step procedure. We first investigate the reconstruction quality of the wet refractivity profiles at the location of Payerne by comparing them to wet refractivity profiles computed from radiosonde profiles available for that location. We also assess the individual contributions of the data sets to the reconstruction quality and demonstrate a clear benefit from the data combination. Secondly, the accuracy of the conversion from wet refractivity to dew point temperature and relative humidity profiles with the radiometer temperature profiles is examined, comparing them also to radiosonde profiles. For the least-squares collocation solution combining GPS and ground meteorological measurements, we achieve the following error figures with respect to the radiosonde reference: maximum median offset of relative refractivity error is −16% and quartiles are 5% to

  2. Global distribution of tropospheric ozone from satellite measurements using the empirically corrected tropospheric ozone residual technique: Identification of the regional aspects of air pollution

    Directory of Open Access Journals (Sweden)

    J. Fishman

    2003-01-01

    Full Text Available Using coincident observations of total ozone from the Total Ozone Mapping Spectrometer (TOMS and stratospheric ozone profiles from the Solar Backscattered Ultraviolet (SBUV instruments, detailed maps of tropospheric ozone have been derived on a daily basis over a time period spanning more than two decades. The resultant climatological seasonal depictions of the tropospheric ozone residual (TOR show much more detail than an earlier analysis that had used coincident TOMS and Stratospheric Aerosol and Gas Experiment (SAGE ozone profiles, although there are many similarities between the TOMS/SAGE TOR and the TOMS/SBUV TOR climatologies. In particular, both TOR seasonal depictions show large enhancements in the southern tropics and subtropics in austral spring and at northern temperate latitudes during the summer. The much greater detail in this new data set clearly defines the regional aspect of tropospheric ozone pollution in northeastern India, eastern United States, eastern China, and west and southern Africa. Being able to define monthly climatologies for each year of the data record provides enough temporal resolution to illustrate significant interannual variability in some of these regions.

  3. Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

    Science.gov (United States)

    Shah, Viral; Jaeglé, Lyatt

    2017-07-01

    Oxidized mercury (Hg(II)) is chemically produced in the atmosphere by oxidation of elemental mercury and is directly emitted by anthropogenic activities. We use the GEOS-Chem global chemical transport model with gaseous oxidation driven by Br atoms to quantify how surface deposition of Hg(II) is influenced by Hg(II) production at different atmospheric heights. We tag Hg(II) chemically produced in the lower (surface-750 hPa), middle (750-400 hPa), and upper troposphere (400 hPa-tropopause), in the stratosphere, as well as directly emitted Hg(II). We evaluate our 2-year simulation (2013-2014) against observations of Hg(II) wet deposition as well as surface and free-tropospheric observations of Hg(II), finding reasonable agreement. We find that Hg(II) produced in the upper and middle troposphere constitutes 91 % of the tropospheric mass of Hg(II) and 91 % of the annual Hg(II) wet deposition flux. This large global influence from the upper and middle troposphere is the result of strong chemical production coupled with a long lifetime of Hg(II) in these regions. Annually, 77-84 % of surface-level Hg(II) over the western US, South America, South Africa, and Australia is produced in the upper and middle troposphere, whereas 26-66 % of surface Hg(II) over the eastern US, Europe, and East Asia, and South Asia is directly emitted. The influence of directly emitted Hg(II) near emission sources is likely higher but cannot be quantified by our coarse-resolution global model (2° latitude × 2.5° longitude). Over the oceans, 72 % of surface Hg(II) is produced in the lower troposphere because of higher Br concentrations in the marine boundary layer. The global contribution of the upper and middle troposphere to the Hg(II) dry deposition flux is 52 %. It is lower compared to the contribution to wet deposition because dry deposition of Hg(II) produced aloft requires its entrainment into the boundary layer, while rain can scavenge Hg(II) from higher altitudes more readily. We find

  4. Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

    Directory of Open Access Journals (Sweden)

    B. Newsome

    2017-12-01

    Full Text Available Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global, use these rate constants. Expert panels evaluate laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the Jet Propulsion Laboratory (JPL and International Union of Pure and Applied Chemistry (IUPAC evaluations we assess the influence of 50 mainly inorganic rate constants and 10 photolysis rates on tropospheric composition through the use of the GEOS-Chem chemistry transport model. We assess the impact on four standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH →M  HNO3 and O3 + NO  →  NO2 + O2 are the two largest sources of uncertainty in these metrics. The absolute magnitude of the change in the metrics is similar if rate constants are increased or decreased by their σ values. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 10, 11, 16 and 16 %, respectively. These are larger than the spread between models in recent model intercomparisons. Remote

  5. Livermore blasted for project delay

    CERN Multimedia

    1999-01-01

    In a 12 page report issued last week, a review committee set up by the University of California has concluded that mismanagement and poor planning are to blame for significant cost overruns and delays in the construction of NIF, the worlds largest laser (1 page).

  6. EAMJ Delayed April 10.indd

    African Journals Online (AJOL)

    2010-04-04

    Apr 4, 2010 ... Patient delay accounts for a large proportion of those who present with late stage disease especially ... Data collection: All patients diagnosed with breast cancer who certified the inclusion criteria were ..... Ingram, D.M., Huang, H.Y., Catchpole, B.N. and. Roberts, A. Do big breasts disadvantage women with.

  7. Diagnostic Delay in Rheumatoid Arthritis

    DEFF Research Database (Denmark)

    Mølbaek, Karen; Hørslev-Petersen, Kim; Primdahl, Jette

    2016-01-01

    BACKGROUND: To prevent joint damage among patients with rheumatoid arthritis (RA), there is a need to minimize delays from the onset of symptoms until the initiation of appropriate therapy. The present study explored the factors that have an impact on the time it takes for Danish patients with RA...

  8. Design flaw could delay collider

    CERN Multimedia

    Cho, Adrian

    2007-01-01

    "A magnet for the Large Hadron Collider (LHC) failed during a key test at the European particle physics laboratory CERN last week. Physicists and engineers will have to repair the damaged magnet and retrofit others to correct the underlynig design flaw, which could delay the start-up of the mammouth subterranean machine." (1,5 page)

  9. Delayed logistic population models revisited

    OpenAIRE

    Liz, Eduardo

    2014-01-01

    We discuss the global dynamics of some logistic models governed by delay-differential equations. We focus on models of exploited populations, and study the changes in the dynamics as the harvesting effort is increased. We get new results and highlight the link among different logistic equations usually employed in population models.

  10. Providing delay guarantees in Bluetooth

    NARCIS (Netherlands)

    Ait Yaiz, R.; Heijenk, Geert; Titsworth, F.

    2003-01-01

    Bluetooth polling, also referred to as Bluetooth MAC scheduling or intra-piconet scheduling, is the mechanism that schedules the traffic between the participants in a Bluetooth network. Hence, this mechanism is highly determining with respect to the delay packets experience in a Bluetooth network.

  11. Tooth formation - delayed or absent

    Science.gov (United States)

    ... tooth formation; Teeth - delayed or absent formation Images Tooth anatomy Development of baby teeth Development of permanent teeth References ... MO: Elsevier Mosby; 2016:chap 19. Tinanoff N. Development and developmental anomalies of the teeth. In: Kliegman RM, ... NIH MedlinePlus Magazine Read more ...

  12. Early-delayed radiation rhombencephalopathy

    Energy Technology Data Exchange (ETDEWEB)

    Nightingale, S.; Dawes, P.J.D.K.; Cartlidge, N.E.F. (Royal Victoria Infirmary, Newcastle upon Tyne (UK); Newcastle upon Tyne Univ. (UK). Newcastle General Hospital)

    1982-03-01

    A 37-year-old woman developed an early-delayed rhombencephalopathy 7 weeks after completing a course of radiotherapy to a glomus jugulare tumour. The clinical features, comprising nystagmus, skew strabismus, unilateral facial weakness, dysarthria and ataxia, are compared with four previously reported patients with this syndrome.

  13. Deconstructing delayed posttraumatic stress disorder

    NARCIS (Netherlands)

    Smid, G

    2011-01-01

    According to the Diagnostic and Statistical Manual of Mental Disorders, delayed posttraumatic stress disorder (PTSD) must be diagnosed in individuals fulfilling criteria for PTSD if the onset of symptoms is at least six months after the trauma. The purpose of this thesis was to establish the

  14. Study of Heterogeneouse Processes Related to the Chemistry of Tropospheric Oxidants and Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Davidovits, Paul; Worsnop, D R; Jayne, J T; Colb, C E

    2013-02-13

    The objective of the studies was to elucidate the heterogeneous chemistry of tropospheric aerosols. Experiments were designed to measure both specifically needed parameters, and to obtain systematic data required to build a fundamental understanding of the nature of gas-surface physical and chemical interactions

  15. Energetics of lower tropospheric ultra-long waves: A key to intra ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 118; Issue 2. Energetics of lower tropospheric ultra-long waves: A key to intra-seasonal variability of ... The relation is not only significant but also has a predictive potential.The normalised plot of both the series clearly indicates that the response period of rainfall to ...

  16. The Background Level of the Summer Tropospheric Aerosol over Greenland and the North Atlantic Ocean

    DEFF Research Database (Denmark)

    Flyger, H.; Hansen, K. A.; Megaw, W.J.

    1973-01-01

    An experiment to measure the concentration and size of Aitken nuclei, the concentration of cloud nuclei active at a supersaturation of 1%, the concentration of freezing nuclei activated at -20C, and the chemical nature of the tropospheric aerosol over Greenland and the seas surrounding it is desc...

  17. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    Science.gov (United States)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  18. Evaluation of Simulated Photochemical Partitioning of Oxidized Nitrogen in the Upper Troposphere

    Science.gov (United States)

    Regional and global chemical transport models underpredict NOx (NO +NO2) in the upper troposphere where it is a precursor to the greenhouse gas ozone. The NOx bias has been shown in model evaluations using aircraft data (Singh et al., 2007) and to...

  19. Long-term leaf production response to elevated atmospheric carbon dioxide and tropospheric ozone

    Science.gov (United States)

    Alan F. Talhelm; Kurt S. Pregitzer; Christian P. Giardina

    2011-01-01

    Elevated concentrations of atmospheric CO2 and tropospheric O3 will profoundly influence future forest productivity, but our understanding of these influences over the long-term is poor. Leaves are key indicators of productivity and we measured the mass, area, and nitrogen concentration of leaves collected in litter traps...

  20. Source attribution of interannual variability of tropospheric ozone over the southern hemisphere

    Science.gov (United States)

    Liu, J.; Rodriguez, J. M.; Logan, J. A.; Steenrod, S. D.; Douglass, A. R.; Olsen, M. A.; Wargan, K.; Ziemke, J. R.

    2015-12-01

    Both model simulations and GMAO assimilated ozone product derived from OMI/MLS show a high tropospheric ozone column centered over the south Atlantic from the equator to 30S. This ozone maximum extends eastward to South America and the southeast Pacific; it extends southwestward to southern Africa, south Indian Ocean. In this study, we use hindcast simulations from the GMI model of tropospheric and stratospheric chemistry, driven by assimilated MERRA meteorological fields, to investigate the factors controlling the interannual variations (IAV) of this ozone maximum during the last two decades. We also use various GMI tracer diagnostics, including a stratospheric ozone tracer to tag the impact of stratospheric ozone, and a tagged CO tracer to track the emission sources, to ascertain the contribution of difference processes to IAV in ozone at different altitudes, as well as partial columns above different pressure level. Our initial model analysis suggests that the IAV of the stratospheric contribution plays a major role on in the IAV of the upper tropospheric ozone and explains a large portion of variance during its winter season. Over the south Atlantic region, the IAV of surface emissions from both South America and southern Africa also contribute significantly to the IAV of ozone, especially in the middle and lower troposphere

  1. A Global Climatology of Tropospheric and Stratospheric Ozone Derived from Aura OMI and MLS Measurements

    Science.gov (United States)

    Ziemke, J.R.; Chandra, S.; Labow, G.; Bhartia, P. K.; Froidevaux, L.; Witte, J. C.

    2011-01-01

    A global climatology of tropospheric and stratospheric column ozone is derived by combining six years of Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone measurements for the period October 2004 through December 2010. The OMI/MLS tropospheric ozone climatology exhibits large temporal and spatial variability which includes ozone accumulation zones in the tropical south Atlantic year-round and in the subtropical Mediterranean! Asia region in summer months. High levels of tropospheric ozone in the northern hemisphere also persist in mid-latitudes over the eastern North American and Asian continents extending eastward over the Pacific Ocean. For stratospheric ozone climatology from MLS, largest ozone abundance lies in the northern hemisphere in the latitude range 70degN-80degN in February-April and in the southern hemisphere around 40degS-50degS during months August-October. The largest stratospheric ozone abundances in the northern hemisphere lie over North America and eastern Asia extending eastward across the Pacific Ocean and in the southern hemisphere south of Australia extending eastward across the dateline. With the advent of many newly developing 3D chemistry and transport models it is advantageous to have such a dataset for evaluating the performance of the models in relation to dynamical and photochemical processes controlling the ozone distributions in the troposphere and stratosphere.

  2. An Investigation of Multi-Satellite Stratospheric Measurements on Tropospheric Weather Predictions over Continental United States

    Science.gov (United States)

    Shao, Min

    The troposphere and stratosphere are the two closest atmospheric layers to the Earth's surface. These two layers are separated by the so-called tropopause. On one hand, these two layers are largely distinguished, on the other hand, lots of evidences proved that connections are also existed between these two layers via various dynamical and chemical feedbacks. Both tropospheric and stratospheric waves can propagate through the tropopause and affect the down streams, despite the fact that this propagation of waves is relatively weaker than the internal interactions in both atmospheric layers. Major improvements have been made in numerical weather predictions (NWP) via data assimilation (DA) in the past 30 years. From optimal interpolation to variational methods and Kalman Filter, great improvements are also made in the development of DA technology. The availability of assimilating satellite radiance observation and the increasing amount of satellite measurements enabled the generation of better atmospheric initials for both global and regional NWP systems. The selection of DA schemes is critical for regional NWP systems. The performance of three major data assimilation (3D-Var, Hybrid, and EnKF) schemes on regional weather forecasts over the continental United States during winter and summer is investigated. Convergence rate in the variational methods can be slightly accelerated especially in summer by the inclusion of ensembles. When the regional model lid is set at 50-mb, larger improvements (10˜20%) in the initials are obtained over the tropopause and lower troposphere. Better forecast skills (˜10%) are obtained in all three DA schemes in summer. Among these three DA schemes, slightly better (˜1%) forecast skills are obtained in Hybrid configuration than 3D-Var. Overall better forecast skills are obtained in summer via EnKF scheme. An extra 22% skill in predicting summer surface pressure but 10% less skills in winter are given by EnKF when compared to 3D

  3. Predicting the effects of tropospheric ozone on forest productivity in the Northeastern U.S.

    Science.gov (United States)

    Scott V. Ollinger; John D. Aber; Peter B. Reich

    1996-01-01

    It is widely believed that tropospheric ozone presents a significant anthropogenic stress on forest ecosystems. Although much information has been collected regarding ozone effects at the seedling and leaf level, we do not have a reliable means of estimating the effect on mature, native forests. For the present study, we incorporated leaf-level ozone response...

  4. Derivation of tropospheric methane from TCCON CH4 and HF total column observations

    Science.gov (United States)

    Saad, K. M.; Wunch, D.; Toon, G. C.; Bernath, P.; Boone, C.; Connor, B.; Deutscher, N. M.; Griffith, D. W. T.; Kivi, R.; Notholt, J.; Roehl, C.; Schneider, M.; Sherlock, V.; Wennberg, P. O.

    2014-09-01

    The Total Carbon Column Observing Network (TCCON) is a global ground-based network of Fourier transform spectrometers that produce precise measurements of column-averaged dry-air mole fractions of atmospheric methane (CH4). Temporal variability in the total column of CH4 due to stratospheric dynamics obscures fluctuations and trends driven by tropospheric transport and local surface fluxes that are critical for understanding CH4 sources and sinks. We reduce the contribution of stratospheric variability from the total column average by subtracting an estimate of the stratospheric CH4 derived from simultaneous measurements of hydrogen fluoride (HF). HF provides a proxy for stratospheric CH4 because it is strongly correlated to CH4 in the stratosphere, has an accurately known tropospheric abundance (of zero), and is measured at most TCCON stations. The stratospheric partial column of CH4 is calculated as a function of the zonal and annual trends in the relationship between CH4 and HF in the stratosphere, which we determine from ACE-FTS satellite data. We also explicitly take into account the CH4 column averaging kernel to estimate the contribution of stratospheric CH4 to the total column. The resulting tropospheric CH4 columns are consistent with in situ aircraft measurements and augment existing observations in the troposphere.

  5. RIVM Tropospheric ozone LIDAR report II. System description and first results

    NARCIS (Netherlands)

    Sunesson JA; Apituley A

    1991-01-01

    The construction of a LIDAR system for vertical profiling of tropospheric ozone is described. An overview of the first measurements of the system is given and the status of the system is discussed. The main conclusion are: - The construction of a laboratory version of the system is succesfully

  6. Measured and calculated optical property profiles in the mixed layer and free troposphere

    Science.gov (United States)

    Rosen, James M.; Bodhaine, Barry A.; Boatman, Joe F.; Deluisi, John J.; Post, M. J.; Kim, Young; Schnell, Russell C.; Sheridan, Patrick J.; Garvey, Dennis M.

    1992-01-01

    Nearly simultaneous measurements of the physical and optical properties of mixed layer and free tropospheric aerosols near Boulder, Colorado, were made on several occasions using aircraft, balloon, and ground-based sensors. This effort (Front Range Lidar, Aircraft, and Balloon experiment (FRLAB)) was conducted with the purpose of obtaining a diverse, self-consistent data set that could be used for testing optical model calculations based on measured physical characteristics such as apparent size distribution, composition, and shape. It was found that even with the uncertainties involved, the model predictions are in good agreement with the measurements in the visible and near infrared wavelength regions. At CO2 lidar wavelengths there is considerably more uncertainty in both the calculated and measured values; however, within the estimated errors there appears to be satisfactory agreement except for the highest free tropospheric layer studied. The results also indicate that during FRLAB the aerosol in the boundary layer and free troposphere behaved as spherical particles for optical modeling purposes. The utility of the observations for determining the extinction-to-backscatter ratio relevant to aerosols in the boundary layer and free troposphere is described with typical measured values being in the 20 to 30 sr range.

  7. Chemistry-transport modeling of the satellite observed distribution of tropical tropospheric ozone

    NARCIS (Netherlands)

    Peters, W.; Krol, M.; Dentener, F.; Thompson, A.; Lelieveld, J.

    2001-01-01

    We have compared the 14-year record of satellite derived tropical tropospheric ozone columns (TTOC) from the NIMBUS-7 Total Ozone Mapping Spectrometer (TOMS) to TTOC calculated by a chemistry-transport model (CTM). An objective measure of error, based on the zonal distribution of TTOC in the

  8. Towards development of optimal strategy for real-time troposphere products estimation

    Science.gov (United States)

    Václavovic, Pavel; Douša, Jan; Eben, Kryštof

    2017-04-01

    The Real-Time Demonstration campaign (RT-Demo) was established within the COST Action ES 1206 GNSS4SWEC in April 2015 for the development and improvement of ultra-fast GNSS tropospheric products. Additionally, we developed an estimation of tropospheric corrections for selected stations using the regional numerical weather forecast. Available real-time tropospheric products are visualized via a dedicated web portal monitoring and evaluated in long-term via the GOP-TropDB database capable of inter-comparing different solutions. Additionally, for the development and optimization of the processing strategy in offline mode, we used the GNSS4SWEC Benchmark data set providing observations from a dense GNSS network and orbit and clock corrections stored from real-time streams. Optimization from the simulated real-time solutions were applied in the RT-Demo processing afterwards. Findings from both campaigns together with the evaluation of results will be presented. In addition, we will validate results of GNSS-based tropospheric products supported with meteorological parameters from numerical weather forecasts including their conversion into maps of integrated water vapour content.

  9. The effect of stratospheric sulfur from Mount Pinatubo on tropospheric oxidizing capacity and methane

    NARCIS (Netherlands)

    Banda, Narcissa; Krol, Maarten; van Noije, Twan; van Weele, Michiel; Williams, Jason E.; Sager, Philippe Le; Niemeier, Ulrike; Thomason, Larry; Röckmann, Thomas

    2015-01-01

    The eruption of Mount Pinatubo in 1991 injected a large amount of SO2 into the stratosphere, which formed sulfate aerosols. Increased scattering and absorption of UV radiation by the enhanced stratospheric SO2 and aerosols decreased the amount of UV radiation reaching the troposphere, causing

  10. The influence of the stratosphere on the tropospheric zonal wind response to CO2 doubling

    NARCIS (Netherlands)

    Hinssen, Y.B.L.; Bell, C.J.; Siegmund, P.C.

    2011-01-01

    The influence of a CO2 doubling on the stratospheric potential vorticity (PV) is examined in two climate models. Subsequently, the influence of changes in the stratosphere on the tropospheric zonal wind response is investigated, by inverting the stratospheric PV. Radiative effects seem to dominate

  11. Tropospheric Bromine Chemistry: Implications for Present and Pre-industrial Ozone and Mercury

    Science.gov (United States)

    Parella, J. P.; Jacob, D. J.; Liang, Q.; Zhang, Y.; Mickley, L. J.; Miller, B.; Evans, M. J.; Yang, X.; Pyle, J. A.; Theys, N.; hide

    2012-01-01

    We present a new model for the global tropospheric chemistry of inorganic bromine (Bry) coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Sources of tropospheric Bry include debromination of sea-salt aerosol, photolysis and oxidation of short-lived bromocarbons, and transport from the stratosphere. Comparison to a GOME-2 satellite climatology of tropospheric BrO columns shows that the model can reproduce the observed increase of BrO with latitude, the northern mid-latitudes maximum in winter, and the Arctic maximum in spring. This successful simulation is contingent on the HOBr + HBr reaction taking place in aqueous aerosols and ice clouds. Bromine chemistry in the model decreases tropospheric ozone mixing ratios by mercury against oxidation by Br. This suggests that historical anthropogenic mercury emissions may have mostly deposited to northern mid-latitudes, enriching the corresponding surface reservoirs. The persistent rise in background surface ozone at northern mid-latitudes during the past decades could possibly contribute to the observations of elevated mercury in subsurface waters of the North Atlantic.

  12. The impact of lightning on tropospheric ozone chemistry using a new global lightning parametrisation

    Directory of Open Access Journals (Sweden)

    D. L. Finney

    2016-06-01

    Full Text Available A lightning parametrisation based on upward cloud ice flux is implemented in a chemistry–climate model (CCM for the first time. The UK Chemistry and Aerosols model is used to study the impact of these lightning nitric oxide (NO emissions on ozone. Comparisons are then made between the new ice flux parametrisation and the commonly used, cloud-top height parametrisation. The ice flux approach improves the simulation of lightning and the temporal correlations with ozone sonde measurements in the middle and upper troposphere. Peak values of ozone in these regions are attributed to high lightning NO emissions. The ice flux approach reduces the overestimation of tropical lightning apparent in this CCM when using the cloud-top approach. This results in less NO emission in the tropical upper troposphere and more in the extratropics when using the ice flux scheme. In the tropical upper troposphere the reduction in ozone concentration is around 5–10 %. Surprisingly, there is only a small reduction in tropospheric ozone burden when using the ice flux approach. The greatest absolute change in ozone burden is found in the lower stratosphere, suggesting that much of the ozone produced in the upper troposphere is transported to higher altitudes. Major differences in the frequency distribution of flash rates for the two approaches are found. The cloud-top height scheme has lower maximum flash rates and more mid-range flash rates than the ice flux scheme. The initial Ox (odd oxygen species production associated with the frequency distribution of continental lightning is analysed to show that higher flash rates are less efficient at producing Ox; low flash rates initially produce around 10 times more Ox per flash than high-end flash rates. We find that the newly implemented lightning scheme performs favourably compared to the cloud-top scheme with respect to simulation of lightning and tropospheric ozone. This alternative lightning scheme shows spatial and

  13. Assimilation of IASI partial tropospheric columns with an Ensemble Kalman Filter over Europe

    Directory of Open Access Journals (Sweden)

    A. Coman

    2012-03-01

    Full Text Available Partial lower tropospheric ozone columns provided by the IASI (Infrared Atmospheric Sounding Interferometer instrument have been assimilated into a chemistry-transport model at continental scale (CHIMERE using an Ensemble Square Root Kalman Filter (EnSRF. Analyses are made for the month of July 2007 over the European domain. Launched in 2006, aboard the MetOp-A satellite, IASI shows high sensitivity for ozone in the free troposphere and low sensitivity at the ground; therefore it is important to evaluate if assimilation of these observations can improve free tropospheric ozone, and possibly surface ozone. The analyses are validated against independent ozone observations from sondes, MOZAIC1 aircraft and ground based stations (AIRBASE – the European Air quality dataBase and compared with respect to the free run of CHIMERE. These comparisons show a decrease in error of 6 parts-per-billion (ppb in the free troposphere over the Frankfurt area, and also a reduction of the root mean square error (respectively bias at the surface of 19% (33% for more than 90% of existing ground stations. This provides evidence of the potential of data assimilation of tropospheric IASI columns to better describe the tropospheric ozone distribution, including surface ozone, despite the lower sensitivity.

    The changes in concentration resulting from the observational constraints were quantified and several geophysical explanations for the findings of this study were drawn. The corrections were most pronounced over Italy and the Mediterranean region, we noted an average reduction of 8–9 ppb in the free troposphere with respect to the free run, and still a reduction of 5.5 ppb at ground, likely due to a longer residence time of air masses in this part associated to the general circulation pattern (i.e. dominant western circulation and to persistent anticyclonic conditions over the Mediterranean basin. This is an important geophysical result, since the

  14. Consistency of tropospheric ozone observations made by different platforms and techniques in the global databases

    Directory of Open Access Journals (Sweden)

    Hiroshi Tanimoto

    2015-10-01

    Full Text Available A large quantity of tropospheric ozone observations are conducted all over the world using different platforms and techniques for different purposes and goals. These observations are commonly used to derive seasonal cycles, interannual variations and long-term trends of ozone in the troposphere. In addition, they are used for comparison with three-dimensional chemistry-transport models to evaluate their performance and hence to test our current understanding of the tropospheric ozone variability. It is still challenging to provide robust tropospheric ozone trends throughout the world because of the great variability of ozone, its complex photochemical reactions, the rarity of long-term records, the diversity of measurement techniques and platforms, and the issues with data quality. In this work, we evaluated, with emphasis on the lower troposphere, the consistency of tropospheric ozone observations made by means of multiple platforms, including surface sites, sondes and regular aircraft, that are publicly available in the global databases, but excluding space-borne platforms. Concomitant observations were examined on an hourly basis (except for ±3 hours for sonde versus aircraft for pairs of locations at less than 100-km distance. Generally, we found good agreement between sonde and surface observations. We also found that there was no need to apply any correction factor to ozonesonde observations except for Brewer–Mast sondes at Hohenpeissenberg. Because of a larger distance between the site pairs, the correlations found between the aircraft and surface measurements were poorer than those between sonde and surface measurements. However, a relatively simple wind segregation improved the agreement between the aircraft versus surface measurements. We found also that due to diurnal cycles, the sonde launching at a fixed local time led to positive or negative biases against the surface observations, suggesting that great attention should be paid

  15. Atmospheric anomalies over Mt.Etna using GPS signal delays and tomography of radio wave velocities

    Directory of Open Access Journals (Sweden)

    G. Puglisi

    2007-06-01

    Full Text Available Due to the prominent topography of Mt. Etna, the use of satellite geodetic techniques may significantly suffer from atmospheric heterogeneities. This problem mainly affects the DInSAR technique. To overcome these drawbacks the present study attempts to make headway in measuring and interpreting atmospheric anomalies. We used the GAMIT software to obtain the ZTD (Zenith Total Delay values for the GPS sessions performed on 1996-97, during ERS-2 passes at Mt. Etna. GAMIT software also allows to characterize the statistical behaviour of the tropospheric effects, by using residuals for each station-satellite pair, and to locate the atmospheric anomalies, present mostly at low altitudes. The attempt at using these results to produce a tomography of radio waves velocity of the troposphere suggests that the number of GPS stations used to investigate atmosphere is a critical point in such a study. The three stations are too few to invert anomalies eventually existing in the lower atmosphere. This result is a good starting point for better direct future study to verify the applicability of this tomographic technique to a geodetic network with a higher number of stations, with the aim of characterizing the lower atmosphere of Mt. Etna for a more accurate monitoring of ground deformations.

  16. OMI tropospheric NO2 air mass factors over South America: effects of biomass burning aerosols

    Science.gov (United States)

    Castellanos, P.; Boersma, K. F.; Torres, O.; de Haan, J. F.

    2015-09-01

    Biomass burning is an important and uncertain source of aerosols and NOx (NO + NO2) to the atmosphere. Satellite observations of tropospheric NO2 are essential for characterizing this emissions source, but inaccuracies in the retrieval of NO2 tropospheric columns due to the radiative effects of aerosols, especially light-absorbing carbonaceous aerosols, are not well understood. It has been shown that the O2-O2 effective cloud fraction and pressure retrieval is sensitive to aerosol optical and physical properties, including aerosol optical depth (AOD). Aerosols implicitly influence the tropospheric air mass factor (AMF) calculations used in the NO2 retrieval through the effective cloud parameters used in the independent pixel approximation. In this work, we explicitly account for the effects of biomass burning aerosols in the Ozone Monitoring Instrument (OMI) tropospheric NO2 AMF calculation for cloud-free scenes. We do so by including collocated aerosol extinction vertical profile observations from the CALIOP instrument, and aerosol optical depth (AOD) and single scattering albedo (SSA) retrieved by the OMI near-UV aerosol algorithm (OMAERUV) in the DISAMAR radiative transfer model. Tropospheric AMFs calculated with DISAMAR were benchmarked against AMFs reported in the Dutch OMI NO2 (DOMINO) retrieval; the mean and standard deviation of the difference was 0.6 ± 8 %. Averaged over three successive South American biomass burning seasons (2006-2008), the spatial correlation in the 500 nm AOD retrieved by OMI and the 532 nm AOD retrieved by CALIOP was 0.6, and 68 % of the daily OMAERUV AOD observations were within 30 % of the CALIOP observations. Overall, tropospheric AMFs calculated with observed aerosol parameters were on average 10 % higher than AMFs calculated with effective cloud parameters. For effective cloud radiance fractions less than 30 %, or effective cloud pressures greater than 800 hPa, the difference between tropospheric AMFs based on implicit and

  17. Impacts of Tropospheric Plumes From Icelandic Fissure Eruptions on the UK

    Science.gov (United States)

    Witham, C. S.

    2003-12-01

    A tropospheric plume from a large basaltic fissure eruption similar to the 934 AD Eldgja or 1783 AD Laki Craters eruptions would be expected to contain acid gases and aerosols including SO2, H2SO4, HCl and HF. High concentrations of these materials pose a hazard to human health and the environment. Reports from Europe during the early months of the 1783/4 Laki Craters eruption suggest that the region was affected by atmospheric pollution resulting from the presence of the eruption plume in the troposphere. We present results from an analysis of English historical mortality data, which show that an unusual and large increase in mortality during August and September 1783 can, in part, be linked to tropospheric pollution from the Laki Craters eruption. We find that a decrease in winter temperature in 1783/4, believed to have been caused by stratospheric volcanic pollution, also resulted in an increase in mortality. Our analysis of the English historical data suggests that elderly people were particularly badly effected by the eruption-induced tropospheric pollution. This finding has important implications for the health of regional populations following future eruptions of this type. To determine the potential impacts of a similar eruption on public health in the UK in a modern day situation, we have modelled the transport of a hypothetical plume from an Icelandic fissure eruption. Here, we present preliminary results from modelling using the UK Meteorological Office's NAME model. Meteorological data from 2002 and 2003 have been used to assess the probability of a tropospheric plume passing over the UK and Europe under modern day weather conditions and to examine whether there are particularly favourable conditions for such an event. Concentration ranges of some typical volcanic atmospheric pollutants that might be expected in the surface boundary layer are given and suggestions are made as to what impacts such occurrences might have on public health.

  18. Impact of biogenic terpene emissions from Brassica napus on tropospheric ozone over Saxony (Germany): numerical investigation.

    Science.gov (United States)

    Renner, Eberhard; Münzenberg, Annette

    2003-01-01

    The role of biogenic emissions in tropospheric ozone production is currently under discussion and major aspects are not well understood yet. This study aims towards the estimation of the influence of biogenic emissions on tropospheric ozone concentrations over Saxony in general and of biogenic emissions from brassica napus in special. MODELLING TOOLS: The studies are performed by utilizing a coupled numerical modelling system consisting of the meteorological model METRAS and the chemistry transport model MUSCAT. For the chemical part, the Euro-RADM algorithm is used. EMISSIONS: Anthropogenic and biogenic emissions are taken into account. The anthropogenic emissions are introduced by an emission inventory. Biogenic emissions, VOC and NO, are calculated within the chemical transport model MUSCAT at each time step and in each grid cell depending on land use type and on the temperature. The emissions of hydrocarbons from forest areas as well as biogenic NO especially from agricultural grounds are considered. Also terpene emissions from brassica napus fields are estimated. SIMULATION SETUP AND METEOROLOGICAL CONDITIONS: The simulations were performed over an area with an extension of 160 x 140 km2 which covers the main parts of Saxony and neighboring areas of Brandenburg, Sachsen-Anhalt and Thuringia. Summer smog with high ozone concentrations can be expected during high pressure conditions on hot summer days. Typical meteorological conditions for such cases were introduced in an conceptual way. It is estimated that biogenic emissions change tropospheric ozone concentrations in a noticeable way (up to 15% to 20%) and, therefore, should not be neglected in studies about tropospheric ozone. Emissions from brassica napus do have a moderate potential to enhance tropospheric ozone concentrations, but emissions are still under consideration and, therefore, results vary to a high degree. Summing up, the effect of brassica napus terpene emissions on ozone concentrations is

  19. Oxygenated organic chemicals in the Pacific troposphere: Distribution, sources and chemistr

    Science.gov (United States)

    Singh, H. B.; Team

    2003-04-01

    Airborne measurements of a large number of oxygenated organic chemicals (Ox-orgs) were carried out in the Pacific troposphere (0.1-12 km) in the Spring of 2001 (Feb. 24-April 10). Specifically these measurements included acetone, methylethyl ketone (MEK), methanol, ethanol, acetaldehyde, propionaldehyde, PANs, and organic nitrates. Complementary measurements of formaldehyde, organic peroxides, and tracers were also available. Ox-orgs were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Their mixing ratios were typically highest in the lower troposphere and declined towards the upper troposphere and the lowermost stratosphere. Their total abundance (_Ox-orgs) significantly exceeded that of NMHC (_C2-C8 NMHC). A comparison of these data with observations collected some seven years earlier (Feb.-March, 1994), did not reveal any significant changes. Throughout the troposphere mixing ratios of Ox-orgs were strongly correlated with each other as well as with tracers of fossil and biomass/biofuel combustion. Analysis of the relative enhancement of selected Ox-orgs with respect to CH3Cl and CO in twelve sampled plumes, originating from fires, is used to assess their primary and secondary sources from biomass combustion. The composition of these plumes also indicates a large shift of reactive nitrogen into the PAN reservoir thereby limiting ozone formation. The Harvard 3-D photochemical model, that uses state of the art chemistry and source information, is used to compare simulated and observed mixing ratios of selected species. A 1-D model is used to explore the chemistry of aldehydes. These results will be presented.

  20. Increasing Springtime Ozone Mixing Ratios in the Free Troposphere Over Western North America

    Science.gov (United States)

    Cooper, O. R.; Parrish, D. D.; Stohl, A.; Trainer, M.; Nedelec, P.; Thouret, V.; Cammas, J. P.; Oltmans, S. J.; Johnson, B. J.; Tarasick, D.; hide

    2010-01-01

    In the lowermost layer of the atmosphere - the troposphere - ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity1. Moreover, tropospheric ozone itself acts as an effective greenhouse gas. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors resulting in widespread increases in ozone concentrations since the late 1800s. At present, east Asia has the fastest-growing ozone precursor emissions. Much of the springtime east Asian pollution is exported eastwards towards western North America. Despite evidence that the exported Asian pollution produces ozone, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995-2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes, with western North America being particularly sensitive to rising Asian emissions. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA s compliance with its ozone air quality standard.

  1. Evaluating A Priori Ozone Profile Information Used in TEMPO Tropospheric Ozone Retrievals

    Science.gov (United States)

    Johnson, M. S.; Sullivan, J. T.; Liu, X.; Newchurch, M.; Kuang, S.; McGee, T. J.; Langford, A. O.; Senff, C. J.; Leblanc, T.; Berkoff, T.; Gronoff, G.; Chen, G.; Strawbridge, K. B.

    2016-12-01

    Ozone (O3) is a greenhouse gas and toxic pollutant which plays a major role in air quality. Typically, monitoring of surface air quality and O3 mixing ratios is primarily conducted using in situ measurement networks. This is partially due to high-quality information related to air quality being limited from space-borne platforms due to coarse spatial resolution, limited temporal frequency, and minimal sensitivity to lower tropospheric and surface-level O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite is designed to address these limitations of current space-based platforms and to improve our ability to monitor North American air quality. TEMPO will provide hourly data of total column and vertical profiles of O3 with high spatial resolution to be used as a near-real-time air quality product. TEMPO O3 retrievals will apply the Smithsonian Astrophysical Observatory profile algorithm developed based on work from GOME, GOME-2, and OMI. This algorithm uses a priori O3 profile information from a climatological data-base developed from long-term ozone-sonde measurements (tropopause-based (TB) O3 climatology). It has been shown that satellite O3 retrievals are sensitive to a priori O3 profiles and covariance matrices. During this work we investigate the climatological data to be used in TEMPO algorithms (TB O3) and simulated data from the NASA GMAO Goddard Earth Observing System (GEOS-5) Forward Processing (FP) near-real-time (NRT) model products. These two data products will be evaluated with ground-based lidar data from the Tropospheric Ozone Lidar Network (TOLNet) at various locations of the US. This study evaluates the TB climatology, GEOS-5 climatology, and 3-hourly GEOS-5 data compared to lower tropospheric observations to demonstrate the accuracy of a priori information to potentially be used in TEMPO O3 algorithms. Here we present our initial analysis and the theoretical impact on TEMPO retrievals in the lower troposphere.

  2. Global Free-tropospheric NO2 Abundances Derived Using a Cloud Slicing Technique from AURA OMI

    Science.gov (United States)

    Choi, S.; Joiner, J.; Choi, Y.; Duncan, B.N.; Vasilkov, A.; Krotkov, N.; Bucsela, E.J.

    2014-01-01

    We derive free-tropospheric NO2 volume mixing ratios (VMRs) by applying a cloud-slicing technique to data from the Ozone Monitoring Instrument (OMI) on the Aura satellite. In the cloud-slicing approach, the slope of the above-cloud NO2 column versus the cloud scene pressure is proportional to the NO2 VMR. In this work, we use a sample of nearby OMI pixel data from a single orbit for the linear fit. The OMI data include cloud scene pressures from the rotational-Raman algorithm and above-cloud NO2 vertical column density (VCD) (defined as the NO2 column from the cloud scene pressure to the top of the atmosphere) from a differential optical absorption spectroscopy (DOAS) algorithm. We compare OMI-derived NO2 VMRs with in situ aircraft profiles measured during the NASA Intercontinental Chemical Transport Experiment Phase B (INTEX-B) campaign in 2006. The agreement is generally within the estimated uncertainties when appropriate data screening is applied. We then derive a global seasonal climatology of free-tropospheric NO2 VMR in cloudy conditions. Enhanced NO2 in the free troposphere commonly appears near polluted urban locations where NO2 produced in the boundary layer may be transported vertically out of the boundary layer and then horizontally away from the source. Signatures of lightning NO2 are also shown throughout low and middle latitude regions in summer months. A profile analysis of our cloud-slicing data indicates signatures of lightning-generated NO2 in the upper troposphere. Comparison of the climatology with simulations from the global modeling initiative (GMI) for cloudy conditions (cloud optical depth less than10) shows similarities in the spatial patterns of continental pollution outflow. However, there are also some differences in the seasonal variation of free-tropospheric NO2 VMRs near highly populated regions and in areas affected by lightning-generated NOx.

  3. An upper tropospheric "ozone river" from Africa to India detected with the IASI sensor

    Science.gov (United States)

    Barret, B.; Sauvage, B.; Le Flochmoën, E.; De Wachter, E.; Cammas, J.

    2011-12-01

    Over the Indian Ocean, ozone (O3) profile measurements have shown the frequent occurence of elevated O3 concentrations in the mid- to upper-troposphere during the winter season. In particular O3 peaks reaching 120 ppbv were often found in the UT within shallow layers 1 to 2 km thick just below the tropopause. Some studies have attributed these UT O3 laminae to stratosphere to troposphere exchange (STE) along the subtrobical westerly jet (SWJ). O3 peaks in the mid-troposphere have also been atributed to STE and convective lofting of pollution from the Indian continental outflow. Other studies explain winter mid-tropospheric O3 peaks over the Indian Ocean with the eastward advection of air masses impacted by African biomass burning emissions caused by the propagation of waves along the SWJ. In the present study, we use new spaceborne O3 data together with airborne observations of both O3 and CO to document a strong event of pollution transport from Africa to northern India during early winter, supporting the role of Africa in contributing to tropospheric O3 enhancement over India. Thanks to their unprecedented spatio-temporal coverage, the data from the IASI sensor allowed us to follow a flow of O3 rich air masses from the coast of west Africa across the Arabian Sea. This afro-indian O3 river is corroborated over the north-western coast of India by measurements from the airborne MOZAIC program. The O3-CO relationships derived from MOZAIC data enable an unambiguous discrimination of the air masses encountered by the aircraft. Finally, a transport analysis based on particle dispersion lagrangian modeling link this O3 channel transport to the convective outflow of air masses that have been impacted by the emission of O3 precursors from African biomass burning and lightnings.

  4. Chemistry-Transport Modeling of the Satellite Observed Distribution of Tropical Tropospheric Ozone

    Science.gov (United States)

    Peters, Wouter; Krol, Maarten; Dentener, Frank; Thompson, Anne M.; Leloeveld, Jos; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    We have compared the 14-year record of satellite derived tropical tropospheric ozone columns (TTOC) from the NIMBUS-7 Total Ozone Mapping Spectrometer (TOMS) to TTOC calculated by a chemistry-transport model (CTM). An objective measure of error, based on the zonal distribution of TTOC in the tropics, is applied to perform this comparison systematically. In addition, the sensitivity of the model to several key processes in the tropics is quantified to select directions for future improvements. The comparisons indicate a widespread, systematic (20%) discrepancy over the tropical Atlantic Ocean, which maximizes during austral Spring. Although independent evidence from ozonesondes shows that some of the disagreement is due to satellite over-estimate of TTOC, the Atlantic mismatch is largely due to a misrepresentation of seasonally recurring processes in the model. Only minor differences between the model and observations over the Pacific occur, mostly due to interannual variability not captured by the model. Although chemical processes determine the TTOC extent, dynamical processes dominate the TTOC distribution, as the use of actual meteorology pertaining to the year of observations always leads to a better agreement with TTOC observations than using a random year or a climatology. The modeled TTOC is remarkably insensitive to many model parameters due to efficient feedbacks in the ozone budget. Nevertheless, the simulations would profit from an improved biomass burning calendar, as well as from an increase in NOX abundances in free tropospheric biomass burning plumes. The model showed the largest response to lightning NOX emissions, but systematic improvements could not be found. The use of multi-year satellite derived tropospheric data to systematically test and improve a CTM is a promising new addition to existing methods of model validation, and is a first step to integrating tropospheric satellite observations into global ozone modeling studies. Conversely

  5. Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

    Directory of Open Access Journals (Sweden)

    M. Schneider

    2012-12-01

    Full Text Available Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water, long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change. We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere to 8 km (in the upper troposphere and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model. We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.

  6. Oxygenated Organic Chemicals in the Pacific Troposphere: Distribution, Sources and Chemistry

    Science.gov (United States)

    Singh, Hanwant B.; Salas, L.; Chatfield, R.; Czech, E.; Fried, A.; Evans, M.; Jacob, D. J.; Blake, D.; Heikes, B.; Talbot, R.

    2003-01-01

    Airborne measurements of a large number of oxygenated organic chemicals (Oxorgs) were carried out in the Pacific troposphere (0.1-12 km) in the Spring of 2001 (Feb. 24-April 10). Specifically these measuremen ts included acetone, methylethyl ketone (MEK), methanol, ethanol, ace taldehyde, propionaldehyde, PANS, and organic nitrates. Complementary measurements of formaldehyde, organic peroxides, and tracers were al so available. Ox-orgs were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Their mixing ratios were typically highest in the lower troposphere and declined toward s the upper troposphere and the lowermost stratosphere. Their total a bundance (Ox-orgs) significantly exceeded that of NMHC (C2-C8 NMHC). A comparison of these data with observations collected some seven yea rs earlier (Feb.-March, 1994), did not reveal any significant changes . Throughout the troposphere mixing ratios of Ox-orgs were strongly c orrelated with each other as well as with tracers of fossil and bioma sshiof'uel combustion. Analysis of the relative enhancement of selected Oxorgs with respect to CH3Cl and CO in twelve sampled plumes, origi nating from fires, is used to assess their primary and secondary sour ces from biomass combustion. The composition of these plumes also ind icates a large shift of reactive nitrogen into the PAN reservoir ther eby limiting ozone formation. The Harvard 3-D photochemical model, th at uses state of the art chemistry and source information, is used to compare simulated and observed mixing ratios of selected species. A 1 -D model is used to explore the chemistry of aldehydes. These results will be presented.

  7. Reactions of lactones with tropospheric oxidants: A kinetics and products study

    Science.gov (United States)

    Walavalkar, M. P.; Sharma, A.; Dhanya, S.; Naik, P. D.

    2017-07-01

    Tropospheric lifetimes of two lactones, gamma-valerolactone (GVL) and alpha-methyl gamma-butyrolactone (AMGBL) in terms of their reactions with two important tropospheric oxidants- OH and Cl - are estimated, after determining the respective rate coefficients of their reactions in the gas phase using relative rate method. Values of the rate coefficients of the reactions of GVL (kOH = (1.95 ± 0.58) x 10-12; kCl = 2.26 ± 0.53 × 10-11 cm3molecule-1s-1) and AMGBL (kOH = 1.81 ± 0.43 × 10-12; kCl = 3.42 ± 0.63 × 10-11 cm3molecule-1s-1) at 298 K imply that reaction with OH is the dominant reaction in the ambient conditions, and that reaction with Cl atom becomes relevant under marine boundary layer (MBL) conditions, reducing the tropospheric lifetimes to almost half. The tropospheric life times of GVL and AMGBL based on their reaction with OH under ambient conditions are comparable, 71.2 and 76.7 h respectively. However, the products of the reactions are found to be different. In GVL, a promising second generation biofuel component, only ring opening reactions are important, acetic acid and CO2 being the only observed volatile products. In AMGBL, additional ring oxidized products are also formed, of which 3,4-dihydro-3-methyl-2,5-furandione is the most dominant one. The absence of such ring oxidized products in GVL is assigned to the difference in the preferred position of H atom abstraction, based on the computed rate coefficients of individual channels reported in the literature. This suggests that the impact in terms of aerosol generation in the troposphere may also be different for GVL and AMGBL, which differ only in the position of methyl substitution.

  8. Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

    Science.gov (United States)

    Schneider, M.; Barthlott, S.; Hase, F.; González, Y.; Yoshimura, K.; García, O. E.; Sepúlveda, E.; Gomez-Pelaez, A.; Gisi, M.; Kohlhepp, R.; Dohe, S.; Blumenstock, T.; Wiegele, A.; Christner, E.; Strong, K.; Weaver, D.; Palm, M.; Deutscher, N. M.; Warneke, T.; Notholt, J.; Lejeune, B.; Demoulin, P.; Jones, N.; Griffith, D. W. T.; Smale, D.; Robinson, J.

    2012-12-01

    Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.

  9. Delay of Vehicle Motion in Traffic Dynamics

    CERN Document Server

    Bando, M; Nakanishi, K; Nakayama, A; Bando, Masako; Hasebe, Katsuya; Nakanishi, Ken; Nakayama, Akihiro

    1996-01-01

    We demonstrate that in Optimal Velocity Model (OVM) delay times of vehicles coming from the dynamical equation of motion of OVM almost explain the order of delay times observed in actual traffic flows without introducing explicit delay times. Delay times in various cases are estimated: the case of a leader vehicle and its follower, a queue of vehicles controlled by traffic lights and many-vehicle case of highway traffic flow. The remarkable result is that in most of the situation for which we can make a reasonable definition of a delay time, the obtained delay time is of order 1 second.

  10. Minimum Delay Moving Object Detection

    KAUST Repository

    Lao, Dong

    2017-01-08

    We present a general framework and method for detection of an object in a video based on apparent motion. The object moves relative to background motion at some unknown time in the video, and the goal is to detect and segment the object as soon it moves in an online manner. Due to unreliability of motion between frames, more than two frames are needed to reliably detect the object. Our method is designed to detect the object(s) with minimum delay, i.e., frames after the object moves, constraining the false alarms. Experiments on a new extensive dataset for moving object detection show that our method achieves less delay for all false alarm constraints than existing state-of-the-art.

  11. Minimum Delay Moving Object Detection

    KAUST Repository

    Lao, Dong

    2017-11-09

    We present a general framework and method for detection of an object in a video based on apparent motion. The object moves relative to background motion at some unknown time in the video, and the goal is to detect and segment the object as soon it moves in an online manner. Due to unreliability of motion between frames, more than two frames are needed to reliably detect the object. Our method is designed to detect the object(s) with minimum delay, i.e., frames after the object moves, constraining the false alarms. Experiments on a new extensive dataset for moving object detection show that our method achieves less delay for all false alarm constraints than existing state-of-the-art.

  12. Air congestion delay: a review

    Directory of Open Access Journals (Sweden)

    Daniel Alberto Pamplona

    2016-04-01

    Full Text Available This article is a literature review of the air congestion delay and its costs. Air congestion is a worldwide problem. Its existence brings costs for airlines and discomfort for passengers. With the increasing demand for air transport, the study of air congestion has attracted the attention of many researchers around the world. The cause for the delays is erroneously attributed only to the lack of infrastructure investments. The literature review shows that other factors such as population growth, increasing standards of living, lack of operational planning and environmental issues exercise decisive influence. Several studies have been conducted in order to analyze and propose solutions to this problem that affects society as a whole.

  13. Assembly delay line pulse generators

    CERN Multimedia

    CERN PhotoLab

    1971-01-01

    Assembly of six of the ten delay line pulse generators that will power the ten kicker magnet modules. One modulator part contains two pulse generators. Capacitors, inductances, and voltage dividers are in the oil tank on the left. Triggered high-pressure spark gap switches are on the platforms on the right. High voltage pulse cables to the kicker magnet emerge under the spark gaps. In the centre background are the assembled master gaps.

  14. ATLAS calibration delay chip study

    CERN Document Server

    Massol, N

    2003-01-01

    The delay chip is an ASIC developed to precisely adjust signals within the range of 0-24ns in steps of 1ns. In this note, we report the study of the characteristics of this chip like the linearity and the jitter. We describe the influence of temperature and supply voltage on its behavior. Finally, we study its dependency due to the variations in process on a whole production.

  15. Teriparatide Induced Delayed Persistent Hypercalcemia

    Directory of Open Access Journals (Sweden)

    Nirosshan Thiruchelvam

    2014-01-01

    Full Text Available Teriparatide, a recombinant PTH, is an anabolic treatment for osteoporosis that increases bone density. Transient hypercalcemia is a reported side effect of teriparatide that is seen few hours following administration of teriparatide and resolves usually within 16 hours of drug administration. Persistent hypercalcemia, although not observed in clinical trials, is rarely reported. The current case describes a rare complication of teriparatide induced delayed persistent hypercalcemia.

  16. Minimum Delay Moving Object Detection

    KAUST Repository

    Lao, Dong

    2017-05-14

    This thesis presents a general framework and method for detection of an object in a video based on apparent motion. The object moves, at some unknown time, differently than the “background” motion, which can be induced from camera motion. The goal of proposed method is to detect and segment the object as soon it moves in an online manner. Since motion estimation can be unreliable between frames, more than two frames are needed to reliably detect the object. Observing more frames before declaring a detection may lead to a more accurate detection and segmentation, since more motion may be observed leading to a stronger motion cue. However, this leads to greater delay. The proposed method is designed to detect the object(s) with minimum delay, i.e., frames after the object moves, constraining the false alarms, defined as declarations of detection before the object moves or incorrect or inaccurate segmentation at the detection time. Experiments on a new extensive dataset for moving object detection show that our method achieves less delay for all false alarm constraints than existing state-of-the-art.

  17. Tropospheric Ozone Assessment Report: Assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

    Directory of Open Access Journals (Sweden)

    P. J. Young

    2018-01-01

    Full Text Available The goal of the Tropospheric Ozone Assessment Report (TOAR is to provide the research community with an up-to-date scientific assessment of tropospheric ozone, from the surface to the tropopause. While a suite of observations provides significant information on the spatial and temporal distribution of tropospheric ozone, observational gaps make it necessary to use global atmospheric chemistry models to synthesize our understanding of the processes and variables that control tropospheric ozone abundance and its variability. Models facilitate the interpretation of the observations and allow us to make projections of future tropospheric ozone and trace gas distributions for different anthropogenic or natural perturbations. This paper assesses the skill of current-generation global atmospheric chemistry models in simulating the observed present-day tropospheric ozone distribution, variability, and trends. Drawing upon the results of recent international multi-model intercomparisons and using a range of model evaluation techniques, we demonstrate that global chemistry models are broadly skillful in capturing the spatio-temporal variations of tropospheric ozone over the seasonal cycle, for extreme pollution episodes, and changes over interannual to decadal periods. However, models are consistently biased high in the northern hemisphere and biased low in the southern hemisphere, throughout the depth of the troposphere, and are unable to replicate particular metrics that define the longer term trends in tropospheric ozone as derived from some background sites. When the models compare unfavorably against observations, we discuss the potential causes of model biases and propose directions for future developments, including improved evaluations that may be able to better diagnose the root cause of the model-observation disparity. Overall, model results should be approached critically, including determining whether the model performance is acceptable for

  18. Evaluating trends in tropospheric ozone observations from TES with sonde data for the period 2005-2010

    Science.gov (United States)

    Verstraeten, W. W.; Zörner, J.; Boersma, K. F.

    2012-04-01

    Tropospheric ozone is a global air pollutant and an important greenhouse gas. It is mainly produced by the photochemical reaction of short wave radiation with precursor molecules such as NOx and VOC's originating from anthropogenic pollution and biogenic sources. Besides that, intrusions of stratospheric ozone into the higher troposphere contribute to the ozone abundance in the lower atmosphere. Balloon soundings are one way of measuring ozone. These sondes provide in situ measurements of temperature, pressure, humidity and ozone from balloons launched from stations located all over the world. As the distribution of ozone in the troposphere is not uniform both temporal as well as spatial variability in ozone concentrations must be considered. In contrast to the poor spatial sampling by sondes, spaceborne sensors provide a much better coverage and a fixed time retrieval of ozone enabling the understanding of patterns and origins of tropospheric ozone. These sensors, for instance TES (Tropospheric Emission Spectrometer onboard NASA's EOS-Aura satellite), however need to be evaluated with independent data, such as worldwide sonde ozone data (i.e. World Ozone and Ultraviolet Data Center, WOUDC). The objective of this study is to investigate any tropospheric ozone trends when evaluating the TES v4 data record with the worldwide WOUDC sonde dataset for the period 2005-2010. A comparison between the TES and the WOUDC data provides a detailed consistency check of the ozone spatial distribution as well as the seasonal and multi-year patterns in TES and sonde ozone. We used a maximum range of 300 km and a maximum time difference of ± 9 hours between the version 4 TES and sonde ozone data as coincidence criteria to increase the probability that the same air parcels are sampled. To ensure a valid comparison, the TES averaging kernel was applied on the sonde data. Validation of TES tropospheric ozone is conducted at the lower (surface - 500 hPa) and upper (> 500 h

  19. Tropospheric Ozone Changes, Radiative Forcing and Attribution to Emissions in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

    Science.gov (United States)

    Stevenson, D.S.; Young, P.J.; Naik, V.; Lamarque, J.-F.; Shindell, D. T.; Voulgarakis, A.; Skeie, R. B.; Dalsoren, S. B.; Myhre, G.; Berntsen, T. K.; hide

    2013-01-01

    Ozone (O3) from 17 atmospheric chemistry models taking part in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) has been used to calculate tropospheric ozone radiative forcings (RFs). All models applied a common set of anthropogenic emissions, which are better constrained for the present-day than the past. Future anthropogenic emissions follow the four Representative Concentration Pathway (RCP) scenarios, which define a relatively narrow range of possible air pollution emissions. We calculate a value for the pre-industrial (1750) to present-day (2010) tropospheric ozone RF of 410 mW m-2. The model range of pre-industrial to present-day changes in O3 produces a spread (+/-1 standard deviation) in RFs of +/-17%. Three different radiation schemes were used - we find differences in RFs between schemes (for the same ozone fields) of +/-10 percent. Applying two different tropopause definitions gives differences in RFs of +/-3 percent. Given additional (unquantified) uncertainties associated with emissions, climate-chemistry interactions and land-use change, we estimate an overall uncertainty of +/-30 percent for the tropospheric ozone RF. Experiments carried out by a subset of six models attribute tropospheric ozone RF to increased emissions of methane (44+/-12 percent), nitrogen oxides (31 +/- 9 percent), carbon monoxide (15 +/- 3 percent) and non-methane volatile organic compounds (9 +/- 2 percent); earlier studies attributed more of the tropospheric ozone RF to methane and less to nitrogen oxides. Normalising RFs to changes in tropospheric column ozone, we find a global mean normalised RF of 42 mW m(-2) DU(-1), a value similar to previous work. Using normalised RFs and future tropospheric column ozone projections we calculate future tropospheric ozone RFs (mW m(-2); relative to 1750) for the four future scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) of 350, 420, 370 and 460 (in 2030), and 200, 300, 280 and 600 (in 2100). Models show some

  20. Tropospheric ozone changes, radiative forcing and attribution to emissions in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP

    Directory of Open Access Journals (Sweden)

    D. S. Stevenson

    2013-03-01

    Full Text Available Ozone (O3 from 17 atmospheric chemistry models taking part in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP has been used to calculate tropospheric ozone radiative forcings (RFs. All models applied a common set of anthropogenic emissions, which are better constrained for the present-day than the past. Future anthropogenic emissions follow the four Representative Concentration Pathway (RCP scenarios, which define a relatively narrow range of possible air pollution emissions. We calculate a value for the pre-industrial (1750 to present-day (2010 tropospheric ozone RF of 410 mW m−2. The model range of pre-industrial to present-day changes in O3 produces a spread (±1 standard deviation in RFs of ±17%. Three different radiation schemes were used – we find differences in RFs between schemes (for the same ozone fields of ±10%. Applying two different tropopause definitions gives differences in RFs of ±3%. Given additional (unquantified uncertainties associated with emissions, climate-chemistry interactions and land-use change, we estimate an overall uncertainty of ±30% for the tropospheric ozone RF. Experiments carried out by a subset of six models attribute tropospheric ozone RF to increased emissions of methane (44±12%, nitrogen oxides (31 ± 9%, carbon monoxide (15 ± 3% and non-methane volatile organic compounds (9 ± 2%; earlier studies attributed more of the tropospheric ozone RF to methane and less to nitrogen oxides. Normalising RFs to changes in tropospheric column ozone, we find a global mean normalised RF of 42 mW m−2 DU−1, a value similar to previous work. Using normalised RFs and future tropospheric column ozone projections we calculate future tropospheric ozone RFs (mW m−2; relative to 1750 for the four future scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5 of 350, 420, 370 and 460 (in 2030, and 200, 300, 280 and 600 (in 2100. Models show some coherent responses of ozone to climate change

  1. severe organophosphate poisoning with delayed cholinergic crisis

    African Journals Online (AJOL)

    Abrham

    2011-01-06

    Jan 6, 2011 ... CASE REPORT. SEVERE ORGANOPHOSPHATE POISONING WITH DELAYED. CHOLINERGIC CRISIS, INTERMEDIATE SYNDROME AND. ORGANOPHOSPHATE. INDUCED. DELAYED. POLYNEUROPATHY ON SUCCESSION. Aklilu Azazh. ABSTRACT. Organophosphate compounds are the organic ...

  2. Utility of ionosphere and troposphere models for extending the range of high-accuracy GPS

    Science.gov (United States)

    Dodd, David William

    This dissertation studied the use of NOAA real-time ionosphere and troposphere products in extending the range of long-baseline, high-accuracy DGPS for real-time positioning. The question being addressed by this work is; can existing real-time ionosphere and troposphere models reduce the observation uncertainties to the level where they can be used to reliably resolve integer ambiguities, in real-time, over long baselines (>30km). In-house GPS processing software (USM_OTF) was developed to ingest the models and compute epoch-to-epoch, float and fixed ambiguity position solutions. Single baseline processing, ranging from 20 to 740 kin, over several days in four separate sessions (July 2004, January 2005, August 2005 and July 2006) incorporating four regions of the U.S.A. (Michigan, California, Central and the South East), were evaluated. The first session looked at the NOAA real-time troposphere model and the second session looked at the NOAA real-time ionosphere model. The third and fourth sessions looked at the use of both the NOAA real-time ionosphere and troposphere models. Results showed that the NOAA troposphere model reduced the height bias uncertainty by up to 30 cm, under high activity conditions. They also showed that the troposphere model increased the uncertainty standard deviation under these high activity conditions. The results from the first tests of the real-time NOAA ionosphere model showed that, due to satellite coverage issues, it produced worse results than other real-time models. The NOAA model suffered from lack of satellite coverage corrections, especially in areas near the limits of the model, and at the beginning and end of a satellite's flight path. A reduction in satellite numbers lead to weaker geometry and less reliable position solutions. These tests showed that it was better to provide less accurate ionosphere estimates than to leave the satellites out of the solution. These problems were addressed by NOAA prior to the final tests

  3. Detections and simulations of tropospheric water vapor fluctuations due to trapped lee waves by ALOS-2/PALSAR-2 ScanSAR interferometry

    Science.gov (United States)

    Kinoshita, Youhei; Morishita, Yu; Hirabayashi, Yukiko

    2017-08-01

    tropospheric propagation delay, increasing the accuracy in detecting surface deformations.[Figure not available: see fulltext.

  4. Delay Margin in Controlling a Furuta Pendulum

    OpenAIRE

    Hernández-Díez, José-Enrique; Niculescu, Silviu-Iulian; Méndez-Barrios, César-Fernando; González-Galván, Emilio-Jorge; Loredo-Flores, Ambrocio; Escareno, Juan-Antonio

    2017-01-01

    International audience; This paper focuses on the design of an LQR based control scheme for the stabilization of the Furuta Pendulum in its unstable equilibrium point at the upright position. More precisely, we are interested in characterizing the corresponding delay margin under the assumption that the feedback loop includes time-delay. The paper provides an explicit tool to compute the critical delay value in the state feedback loop and a delicate tuning to reach larger delay values. In ord...

  5. A Developmental Study on Delay of Gratification

    OpenAIRE

    Kobayashi, Sayoko; Mitsumoto, Takashi

    2009-01-01

    Two studies were conducted to investigate development of delay of gratification. In Study 1, the personal delay of gratification test, social delay of gratification inventory and personality inventory were administered to kindergarteners aged 3 to 6 years. The personal delay of gratification test included three reward pairs and subjects were instructed to choose between a less valuable reward which was immediately available and a more valuable reward which was available tomorrow. In the perso...

  6. Dynamic Cournot Duopoly Game with Delay

    Directory of Open Access Journals (Sweden)

    A. A. Elsadany

    2014-01-01

    Full Text Available The delay Cournot duopoly game is studied. Dynamical behaviors of the game are studied. Equilibrium points and their stability are studied. The results show that the delayed system has the same Nash equilibrium point and the delay can increase the local stability region.

  7. Synchronization analysis of coloured delayed networks under ...

    Indian Academy of Sciences (India)

    This paper investigates synchronization of coloured delayed networks under decentralized pinning intermittent control. To begin with, the time delays are taken into account in the coloured networks. In addition, we propose a decentralized pinning intermittent control for coloured delayed networks, which is different from that ...

  8. Academic Delay of Gratification and Academic Achievement

    Science.gov (United States)

    Bembenutty, Hefer

    2011-01-01

    The ability to delay gratification is the cornerstone of all academic achievement and education. It is by delaying gratification that learners can pursue long-term academic and career goals. In general, "delay of gratification" refers to an individual's ability to forgo immediate rewards for the sake of more valuable ones later (Mischel, 1996).…

  9. Delayed reinforcement and fixed-ratio performance.

    Science.gov (United States)

    Jarmolowicz, David P; Lattal, Kennon A

    2013-11-01

    Effects of delayed reinforcement on fixed-ratio (FR) maintained responding of pigeons were investigated. In Experiments 1-3, the delay of reinforcement was increased across successive sessions until pigeons paused for 300 s. Both signaled and unsignaled delays were studied across different conditions. Overall response rates and run rates (timed from the first to last response of a ratio) decreased and postreinforcement pauses increased as delays increased in each experiment. As delays increased, the likelihood of pausing during a ratio run also increased. When these measures were plotted as a function of obtained delays, signaled delays had less of an effect on the above measures than did unsignaled ones. In Experiment 2, delays had a greater effect on the above measures than did a control condition arranging equivalent interreinforcer intervals to those accompanying the delays. Experiments 3 and 4 examined the generality of the effects obtained in the first two experiments. In Experiment 3, delays imposed on FR or yoked-interval schedules had similar behavioral effects. In Experiment 4, effects similar to those found in Experiments 1-3 for 1, 10, and 20-s delays imposed on FR 50 schedules were found when the FR requirement increased across sessions. Despite the different contingencies relating response rate and reinforcement rates on interval and ratio schedules, delays of reinforcement generally affect performance on these schedules similarly. © Society for the Experimental Analysis of Behavior.

  10. User-centric video delay measurements

    NARCIS (Netherlands)

    A.J. Jansen (Jack); D.C.A. Bulterman (Dick)

    2013-01-01

    htmlabstractThe complexities and physical constraints associated with video transmission make the introduction of video playout delays unavoidable. Tuning systems to reduce delay requires an ability to effectively and easily gather delay metrics on a potentially wide range of systems. In order to

  11. Generation of layering in the upper arctic troposphere away from the jet stream

    Directory of Open Access Journals (Sweden)

    A. Karpetchko

    2003-07-01

    Full Text Available Ozone sounding databases for two stations, So-dankylä (67° N, 27° E and Ny-Ålesund (79° N, 12° E were used in order to investigate the generation of layering in the upper and middle troposphere of the Arctic. We concentrated on dry, ozone-rich and stable layers observed below the thermal tropopause under light wind conditions. This condition ensures that the observed layer is not a tropopause fold, a well-known phenomenon that develops within frontal zones near the jet stream. Selection criteria for ozone, humidity and stability anomalies of the tropopause fold detection algorithm were used here to pick out for detailed studies the most pronounced examples of laminae. For all these cases the meteorological situations were investigated in order to establish the origin of the observed layers. We found that layers could be classified into two groups. Laminae of the first group were observed equatorward of the jet stream and those of a second group were observed poleward of the jet. The meteorological situation for the first group resembles that for equatorward stratospheric streamer propagation. It was found that this group accounts for only a small fraction of the layers observed at Sodankylä and for none of those observed at Ny-Ålesund during the period investigated. A large case-to-case variability in the synoptic situation was observed for the second group of laminae, which were detected northward of the jet stream. Nevertheless, in about half of the cases, streamers of tropospheric air were found in the vicinity of the stations on the isentropic surfaces just above the detected stratospheric layers. Back trajectory analyses showed that these layers originated in the vicinity of the polar jet stream. We suppose that laminae-like structures in the troposphere were caused, in both groups, by equatorward (poleward advection of the stratospheric (tropospheric air, together with differential vertical shear. Forward-trajectory calculations

  12. Comparison between Satellite Water Vapour Observations and Atmospheric Models’ Predictions of the Upper Tropospheric Thermal Radiation

    Directory of Open Access Journals (Sweden)

    J. R. Dim

    2011-01-01

    Full Text Available Atmospheric profiles (temperature, pressure, and humidity are commonly used parameters for aerosols and cloud properties retrievals. In preparation of the launch of the Global Change Observation Mission-Climate/Second-Generation GLobal Imager (GCOM-C/SGLI satellite, an evaluation study on the sensitivity of atmospheric models to variations of atmospheric conditions is conducted. In this evaluation, clear sky and above low clouds water vapour radiances of the upper troposphere obtained from satellite observations and those simulated by atmospheric models are compared. The models studied are the Nonhydrostatic ICosahedral Atmospheric Model (NICAM and the National Center for Environmental Protection/Department Of Energy (NCEP/DOE. The satellite observations are from the Terra/Moderate Resolution Imaging Spectroradiometer (Terra/MODIS satellite. The simulations performed are obtained through a forward radiative transfer calculation procedure. The resulting radiances are transformed into the upper tropospheric brightness temperature (UTBT and relative humidity (UTRH. The discrepancies between the simulated data and the observations are analyzed. These analyses show that both the NICAM and the NCEP/DOE simulated UTBT and UTRH have comparable distribution patterns. However the simulations’ differences with the observations are generally lower with the NCEP/DOE than with the NICAM. The NCEP/DOE model outputs very often overestimate the UTBT and therefore present a drier upper troposphere. The impact of the lower troposphere instability (dry convection on the upper tropospheric moisture and the consequences on the models’ results are evaluated through a thunderstorm and moisture predictor (the K-stability index. The results obtained show a positive relation between the instability and the root mean square error (RMSE: observation versus models. The study of the impact of convective clouds shows that the area covered by these clouds increases with the

  13. Reanalysis comparisons of upper tropospheric-lower stratospheric jets and multiple tropopauses

    Science.gov (United States)

    Manney, Gloria L.; Hegglin, Michaela I.; Lawrence, Zachary D.; Wargan, Krzysztof; Millán, Luis F.; Schwartz, Michael J.; Santee, Michelle L.; Lambert, Alyn; Pawson, Steven; Knosp, Brian W.; Fuller, Ryan A.; Daffer, William H.

    2017-09-01

    The representation of upper tropospheric-lower stratospheric (UTLS) jet and tropopause characteristics is compared in five modern high-resolution reanalyses for 1980 through 2014. Climatologies of upper tropospheric jet, subvortex jet (the lowermost part of the stratospheric vortex), and multiple tropopause frequency distributions in MERRA (Modern-Era Retrospective analysis for Research and Applications), ERA-I (ERA-Interim; the European Centre for Medium-Range Weather Forecasts, ECMWF, interim reanalysis), JRA-55 (the Japanese 55-year Reanalysis), and CFSR (the Climate Forecast System Reanalysis) are compared with those in MERRA-2. Differences between alternate products from individual reanalysis systems are assessed; in particular, a comparison of CFSR data on model and pressure levels highlights the importance of vertical grid spacing. Most of the differences in distributions of UTLS jets and multiple tropopauses are consistent with the differences in assimilation model grids and resolution - for example, ERA-I (with coarsest native horizontal resolution) typically shows a significant low bias in upper tropospheric jets with respect to MERRA-2, and JRA-55 (the Japanese 55-year Reanalysis) a more modest one, while CFSR (with finest native horizontal resolution) shows a high bias with respect to MERRA-2 in both upper tropospheric jets and multiple tropopauses. Vertical temperature structure and grid spacing are especially important for multiple tropopause characterizations. Substantial differences between MERRA and MERRA-2 are seen in mid- to high-latitude Southern Hemisphere (SH) winter upper tropospheric jets and multiple tropopauses as well as in the upper tropospheric jets associated with tropical circulations during the solstice seasons; some of the largest differences from the other reanalyses are seen in the same times and places. Very good qualitative agreement among the reanalyses is seen between the large-scale climatological features in UTLS jet and

  14. Delay Variation Model with Two Service Queues

    Directory of Open Access Journals (Sweden)

    Filip Rezac

    2010-01-01

    Full Text Available Delay in VoIP technology is very unpleasant issue and therefore a voice packets prioritization must be ensured. To maintain the high call quality a maximum information delivery time from the sender to the recipient is set to 150 ms. This paper focuses on the design of a mathematical model of end-to-end delay of a VoIP connection, in particular on a delay variation. It describes all partial delay components and mechanisms, their generation, facilities and mathematical formulations. A new approach to the delay variation model is presented and its validation has been done by experimention.

  15. Controllability of Nonlinear Fractional Delay Dynamical Systems

    Science.gov (United States)

    Nirmala, R. Joice; Balachandran, K.; Rodríguez-Germa, L.; Trujillo, J. J.

    2016-02-01

    This paper is concerned with controllability of nonlinear fractional delay dynamical systems with delay in state variables. The solution representations of fractional delay differential equations have been established by using the Laplace transform technique and the Mittag-Leffler function. Necessary and sufficient conditions for the controllability criteria of linear fractional delay systems are established. Further sufficient condition for the controllability of nonlinear fractional delay dynamical system are obtained by using the fixed point argument. Examples and numerical simulation are presented to illustrate the results.

  16. Fuzzy delay model based fault simulator for crosstalk delay fault test ...

    Indian Academy of Sciences (India)

    The delays of a logic gates or interconnect are affected by various fabrication process parameters and however accurate the delay models are, it is very difficult to model the process uncertainties. In this paper, the fuzzy delay model is employed for test generation of crosstalk delay faults in asynchronous sequential circuits.

  17. Tropospheric Aerosol Radiative Forcing Observational eXperiment - University of Washington instrumented C-131A aircraft Data Set

    Data.gov (United States)

    National Aeronautics and Space Administration — TARFOX_UWC131A is the Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) - University of Washington instrumented C-131A aircraft data set. The...

  18. Tropospheric Aerosol Radiative Forcing Observational eXperiment - Ames Sun Photometer - University of Washington C-131A aircraft

    Data.gov (United States)

    National Aeronautics and Space Administration — TARFOX_UWC131A_SUNP Data Set was collected from the 6-channel Sun Photometer flown on the University of Washington C-131A aircraft during the Tropospheric Aerosol...

  19. Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) - Scanning Mobility Particle Sizer from Wallops ground station

    Data.gov (United States)

    National Aeronautics and Space Administration — TARFOX_WALLOPS_SMPS is the Tropospheric Aerosol Radiative Forcing Observational eXperiment (TARFOX) Scanning Mobility Particle Sizer (SMPS) data set from Wallops...

  20. Tropospheric Emission Spectrometer (TES) Satellite Validations of Ammonia, Methanol, Formic Acid, and Carbon Monoxide over the Canadian Oil Sands

    Data.gov (United States)

    U.S. Environmental Protection Agency — The URLs link to the data archive of the Troposphere Emission Spectrometer (TES) retrievals. These include the transects included in the Canadian Tar Sands study. A...

  1. Relationship between surface, free tropospheric and total column ozone in 2 contrasting areas in South-Africa

    CSIR Research Space (South Africa)

    Combrink, J

    1995-04-01

    Full Text Available Measurements of surface ozone in two contrasting areas of South Africa are compared with free tropospheric and Total Ozone Mapping Spectrometer (TOMS) total column ozone data. Cape Point is representative of a background monitoring station which...

  2. AIRS/Aqua Level 3 Daily CO2 in the free troposphere (AIRS-only) V005

    Data.gov (United States)

    National Aeronautics and Space Administration — This is the AIRS mid-tropospheric Carbon Dioxide (CO2) Level 3 Daily Gridded Retrieval, from the AIRS instrument on board of Aqua satellite. It is a daily gridded...

  3. AIRS/Aqua Level 3 Daily CO2 in the free troposphere (AIRS+AMSU) V005

    Data.gov (United States)

    National Aeronautics and Space Administration — This is the AIRS mid-tropospheric Carbon Dioxide (CO2) Level 3 Daily Gridded Retrieval, from the AIRS and AMSU instruments on board of Aqua satellite. It is a daily...

  4. Analysis of satellite-derived Arctic tropospheric BrO columns in conjunction with aircraft measurements during ARCTAS and ARCPAC

    National Research Council Canada - National Science Library

    Choi, S; Wang, Y Yuanyue; Salawitch, RJ; Canty, T; Joiner, J; Zeng, T; Kurosu, TP; Chance, K; Richter, A; Huey, LG; Liao, J; Neuman, JA; Nowak, JB; Dibb, JE; Weinheimer, AJ; Diskin, G; Ryerson, TB; Silva, A da; Curry, J; Kinnison, D; Tilmes, S; Levelt, PF Pieternel

    2012-01-01

    We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative...

  5. AIRS/Aqua Level 3 Monthly CO2 in the free troposphere (AIRS+AMSU) V005

    Data.gov (United States)

    National Aeronautics and Space Administration — This is the AIRS mid-tropospheric Carbon Dioxide (CO2) Level 3 Monthly Gridded Retrieval, from the AIRS and AMSU instruments on board of Aqua satellite. It is a...

  6. Role of deep cloud convection in the ozone budget of the troposphere.

    Science.gov (United States)

    Lelieveld, J; Crutzen, P J

    1994-06-17

    Convective updrafts in thunderstorms prolong the lifetime of ozone (O(3)) and its anthropogenic precursor NOx [nitric oxide (NO) + nitrogen dioxide (NO(2))] by carrying these gases rapidly upward from the boundary layer into a regime where the O(3) production efficiency is higher, chemical destruction is slower, and surface deposition is absent. On the other hand, the upper troposphere is relatively rich in O(3) and NOx from natural sources such as downward transport from the stratosphere and lightning; convective overturning conveys the O(3) and NOx toward the Earth's surface where these components are more efficiently removed from the atmosphere. Simulations with a three-dimensional global model suggest that the net result of these counteractive processes is a 20 percent overall reduction in total tropospheric O(3). However, the net atmospheric oxidation efficiency is enhanced by 10 to 20 percent.

  7. How important is tropospheric humidity for coastal rainfall in the tropics?

    CERN Document Server

    Bergemann, Martin

    2016-01-01

    Recent research has community have shown that tropical convection and rainfall is sensitive to mid-tropospheric humidity. Therefore it has been suggested to improve the representation of moist convection by making cumulus parameterizations more sensitive to mid-tropospheric moisture. Climate models show considerable rainfall biases in coastal tropical areas, where approx. 33 % of the overall rainfall received is associated with coastal land-sea interaction. Building on an algorithm to objectively identify rainfall that is associated with land-sea interaction we investigate whether the relationship between rainfall in coastal regions and atmospheric humidity differs from that over the open ocean or over inland areas. We combine 3-hourly satellite estimates of rainfall with humidity estimates from reanalyses and investigate if coastal rainfall reveals the well known relationship between area-averaged precipitation and column integrated moisture. We find that rainfall that is associated with coastal land-sea eff...

  8. NO2 Total and Tropospheric Vertical Column Densities from OMI on EOS Aura: Update

    Science.gov (United States)

    Gleason, J.F.; Bucsela, E.J.; Celarier, E.A.; Veefkind, J.P.; Kim, S.W.; Frost, G.F.

    2009-01-01

    The Ozone Monitoring Instrument (OMI), which is on the EOS AURA satellite, retrieves vertical column densities (VCDs) of NO2, along with those of several other trace gases. The relatively high spatial resolution and daily global coverage of the instrument make it particularly well-suited to monitoring tropospheric pollution at scales on the order of 20 km. The OMI NO2 algorithm distinguishes polluted regions from background stratospheric NO2 using a separation algorithm that relies on the smoothly varying stratospheric NO2 and estimations of both stratospheric and tropospheric air mass factors (AMFs). Version 1 of OMI NO2 data has been released for public use. An overview of OMI NO2 data, some recent results and a description of the improvements for version 2 of the algorithm will be presented.

  9. A comparison of lightning and aircraft sources of NO{sub x} in the upper troposphere

    Energy Technology Data Exchange (ETDEWEB)

    Penner, J.E.; Walton, J.J. [Michigan Univ., Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic and Space Physics; Bergmann, D.J.; Kinnison, D.; Rotman, D. [Lawrence Livermore National Lab., CA (United States). Atmospheric Science Div.; Price, C. [Tel Aviv Univ. (Israel). Dept. of Geophysics and Planetary Sciences; Prather, M.J. [California Univ., Irvine, CA (United States). Dept. of Earth System Science; Pickering, K.E. [Maryland Univ., College Park, MD (United States). Dept. of Meteorology; Baughcum, S.L. [Boeing Commerial Airplane Group, Seatlle, WA (United States)

    1997-12-31

    Uncertainties in the assessment of the contribution of aircraft to upper tropospheric NO{sub x} arise from uncertainties in model treatment of transport, uncertainties in source strengths, and uncertainties in chemical rates and reactions determining the partitioning between NO{sub x} and NO{sub y}. Two different chemical transport models are used to examine the range of uncertainty in the contribution of aircraft to upper tropospheric NO{sub x} from model representations of transport. Uncertainties caused by uncertainties in the rate of production of NO{sub x} from lightning and uncertainties from the range of background concentrations of HNO{sub 3} are also examined. Uncertainties in the treatment of vertical transport and uncertainties in the source strength from lightning contribute to a large range in model results for background NO{sub x}. (author) 18 refs.

  10. Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

    Science.gov (United States)

    Tang, Mingjin; Huang, Xin; Lu, Keding; Ge, Maofa; Li, Yongjie; Cheng, Peng; Zhu, Tong; Ding, Aijun; Zhang, Yuanhang; Gligorovski, Sasho; Song, Wei; Ding, Xiang; Bi, Xinhui; Wang, Xinming

    2017-10-01

    Heterogeneous reactions of mineral dust aerosol with trace gases in the atmosphere could directly and indirectly affect tropospheric oxidation capacity, in addition to aerosol composition and physicochemical properties. In this article we provide a comprehensive and critical review of laboratory studies of heterogeneous uptake of OH, NO3, O3, and their directly related species as well (including HO2, H2O2, HCHO, HONO, and N2O5) by mineral dust particles. The atmospheric importance of heterogeneous uptake as sinks for these species is assessed (i) by comparing their lifetimes with respect to heterogeneous reactions with mineral dust to lifetimes with respect to other major loss processes and (ii) by discussing relevant field and modeling studies. We have also outlined major open questions and challenges in laboratory studies of heterogeneous uptake by mineral dust and discussed research strategies to address them in order to better understand the effects of heterogeneous reactions with mineral dust on tropospheric oxidation capacity.

  11. Evaluating Effects of H2O and overhead O3 on Global Mean Tropospheric OH Concentration

    Science.gov (United States)

    Nicely, Julie M.; Salawitch, R.J.; Canty, T.; Lang, Chang; Duncan, Bryan; Liang, Qing; Oman, Luke David; Stolarski, Richard S.; Waugh, Darryn

    2012-01-01

    The oxidizing capacity of the troposphere is controlled, to a large extent, by the abundance of hydroxyl radical (OH). The global mean concentration of OH, [OH]GLOBAL, inferred from measurements of methyl chloroform, has remained relatively constant during the past several decades, despite rising levels of CH4 that should have led to a steady decline. Here we examine other factors that may have affected [OH]GLOBAL, such as the overhead burden of stratospheric O3 and tropospheric H2O, using global OH fields from the GEOS-CHEM Chemistry-Climate Model. Our analysis suggests these factors may have contributed a positive trend to [OH]GLOBAL large enough to counter the decrease due to CH4.

  12. An Extended Tropospheric Scintillation Model for Free Space Optical Communication Systems

    Directory of Open Access Journals (Sweden)

    John O. Famoriji

    2014-09-01

    Full Text Available Fluctuations caused mostly by tropospheric scintillation at the free space optical receiver end have been a major problem in the rapid development of telecommunication and the increasing demands for larger bandwidth is forcing the use of free space optical (FSO technology. This paper examined existing tropospheric scintillation models of Karasawa, Van de Kamp model, Otung, Ortgies and ITU-R, and discovered that all of them operate at the microwave range, which limits their application in FSO laser beam technology that operates in PHz frequency-range. ITU-R model was later selected owing to its global application and modified for use in FSO communication system. The new model can serve as basis for communication engineers to use as platform in the link budgetary for planning and design of low margin systems of free space optical communication link.

  13. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    Directory of Open Access Journals (Sweden)

    C. E. Lund Myhre

    2004-01-01

    Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

  14. High Temporal Resolution Tropospheric Wind Profile Observations at NASA Kennedy Space Center During Hurricane Irma

    Science.gov (United States)

    Decker, Ryan; Barbre, Robert; Huddleston, Lisa; Wilfong, Tim; Brauer, Tom

    2018-01-01

    The NASA Kennedy Space Center (KSC) operates a 48-MHz Tropospheric/Stratospheric Doppler Radar Wind Profiler (TDRWP) on a continual basis generating wind profiles between 2-19 km in the support of space launch vehicle operations. A benefit of the continual operability of the system is the ability to provide unique observations of severe weather events such as hurricanes. On the evening of 10 September 2017, Hurricane Irma passed within 100 miles to the west of KSC through the middle of the Florida peninsula. The hurricane was responsible for power outages to approximately 2/3 of Florida's population. This paper will describe the characteristics of the tropospheric wind observations from the TDRWP during Irma, provide a comparison to previous TDRWP observations from Hurricane Matthew in 2016, and discuss lessons learned regarding dissemination of TDRWP data during the event.

  15. Importance of heterogeneous processes to tropospheric chemistry - Studies with a one-dimensional model

    Science.gov (United States)

    Turco, R. P.; Toon, O. B.; Whitten, R. C.; Keesee, R. G.; Hamill, P.

    1982-01-01

    A one-dimensional, time-dependent model of tropospheric air composition is developed which incorporates several heterogeneous physical and chemical processes. The model includes the interaction of gases, aerosols, and hydrometeors through the physical mechanisms of nucleation, condensation, evaporation, coagulation, coalescence, and deliquescence. Precipitation, sedimentation, and dry deposition act to remove material from the atmosphere, while chemical transformations occur both in the vapor and the condensed phases. The model also incorporates the sources and vertical diffusion of gases and particles, as well as changes in the solar intensity caused by light-scattering from aerosols and clouds. Preliminary simulations made using this model indicate that rainout and washout processes strongly influence the distributions of tropospheric gases and aerosols under certain conditions.

  16. Experimental particle formation rates spanning tropospheric sulfuric acid and ammonia abundances, ion production rates, and temperatures

    CERN Document Server

    Kürten, Andreas; Almeida, Joao; Kupiainen-Määttä, Oona; Dunne, Eimear M.; Duplissy, Jonathan; Williamson, Christina; Barmet, Peter; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Franchin, Alessandro; Gordon, Hamish; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Ickes, Luisa; Jokinen, Tuija; Kangasluoma, Juha; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Onnela, Antti; Ortega, Ismael K.; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schnitzhofer, Ralf; Schobesberger, Siegfried; Smith, James N.; Steiner, Gerhard; Stozhkov, Yuri; Tomé, António; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Wagner, Paul E.; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Ken; Kulmala, Markku; Curtius, Joachim

    2016-01-01

    Binary nucleation of sulfuric acid and water as well as ternary nucleation involving ammonia arethought to be the dominant processes responsible for new particle formation (NPF) in the cold temperaturesof the middle and upper troposphere. Ions are also thought to be important for particle nucleation inthese regions. However, global models presently lack experimentally measured NPF rates under controlledlaboratory conditions and so at present must rely on theoretical or empirical parameterizations. Here withdata obtained in the European Organization for Nuclear Research CLOUD (Cosmics Leaving OUtdoor Droplets)chamber, we present the first experimental survey of NPF rates spanning free tropospheric conditions. Theconditions during nucleation cover a temperature range from 208 to 298 K, sulfuric acid concentrationsbet ween 5 × 105and 1 × 109cm3, and ammonia mixing ratios from zero added ammonia, i.e., nominally purebinary, to a maximum of ~1400 parts per trillion by volume (pptv). We performed nucleation s...

  17. The meteorological environment of the tropospheric ozone maximum over the tropical South Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Krishnamurti, T.N.; Fuelberg, H.E.; Bensman, E.L.; Sinha, M.C.; Oosterhof, D.; Kumar, V.B. (Florida State University, Tallahassee, FL (United States). Department of Meteorology)

    1993-01-01

    This paper examines atmospheric flow patterns over the Southern Atlantic Ocean, where a maximum of tropospheric ozone is observed just west of Southern Africa. The climatology of the South Atlantic basin is shown to favour flow off from South America and Africa converging into the area of high tropospheric ozone. This ozone is initially attributable to byproducts of biomass burning over both these continents. A case study, carried out over 6 days during October 1989, was used to determine the effect of a purely advective scheme (no photochemistry) on the distribution of ozone over the basin. The results showed a pattern in which ozone accumulated off the west coast of South Africa within 72 hours after beginning with an homogenous, zonally-symmetric distribution of ozone. 11 refs.

  18. Tropospheric and Boundary-Layer Water Vapor Isotopes over the Boreal Forest and Mediterranean Sea: Validation of Aura Tropospheric Emission Spectrometer Retrievals of HDO and H2O

    Science.gov (United States)

    Herman, R. L.; Cherry, J. E.; Young, J. M.; Welker, J. M.; Noone, D. C.; Sodemann, H.; Worden, J.

    2013-12-01

    Water vapor and HDO retrievals from the Tropospheric Emission Spectrometer (TES) on the EOS Aura platform have been compared with nearly coincident in situ airborne measurements. These measurements were made with commercially available Picarro L2130-I isotopic water analyzers on aircraft platforms over in the Alaskan Boreal forest interior during summers of 2011 and 2012, as well as aircraft measurements over the Mediterranean Sea near Sicily in 2012. TES Transect special observations were utilized in these comparisons. The TES averaging kernels and a priori constraints have been applied to the in situ data, using water vapor constraint vectors from GMAO GEOS-5 analyses for Version Five (V005) of TES data. TES calculated errors are compared with the rms (root mean square) of scan-to-scan variability to assess how much of the variability is attributable to TES observation error. Spatial and temporal variations are assessed from the in situ aircraft measurements. Over Alaska, a significant portion of the scan-to-scan variability is due to this atmospheric heterogeneity and vertical mixing. This variability was not observed over the Mediterranean and suggest that the water vapor isotope flux (primarily transpiration) from the vegetated surface of the Boreal contributes to the vertical heterogeneity from the upper to the lower atmosphereof the troposphere. The TES V005 bias in HDO/H2O will be reported in this presentation.

  19. Large Deviations for Gaussian Diffusions with Delay

    Science.gov (United States)

    Azencott, Robert; Geiger, Brett; Ott, William

    2018-01-01

    Dynamical systems driven by nonlinear delay SDEs with small noise can exhibit important rare events on long timescales. When there is no delay, classical large deviations theory quantifies rare events such as escapes from metastable fixed points. Near such fixed points, one can approximate nonlinear delay SDEs by linear delay SDEs. Here, we develop a fully explicit large deviations framework for (necessarily Gaussian) processes X_t driven by linear delay SDEs with small diffusion coefficients. Our approach enables fast numerical computation of the action functional controlling rare events for X_t and of the most likely paths transiting from X_0 = p to X_T=q. Via linear noise local approximations, we can then compute most likely routes of escape from metastable states for nonlinear delay SDEs. We apply our methodology to the detailed dynamics of a genetic regulatory circuit, namely the co-repressive toggle switch, which may be described by a nonlinear chemical Langevin SDE with delay.

  20. Reasons for diagnostic delay in gynecological malignancies

    DEFF Research Database (Denmark)

    Vandborg, Mai Partridge; Christensen, René dePont Christensen; Kragstrup, Jakob

    2011-01-01

    Aim The primary aim of this study was to identify and describe different delay types in women with gynecologic cancer, and to analyze the relationship between diagnostic delay and a number of characteristics for patients, cancers and the health care system. Setting A cohort study of women newly......) and The Danish Gynecological Cancer Database (DGCD). 161 women were included; ovarian cancer: 63, endometrial cancer: 50, cervical cancer: 34 and vulvar cancer: 14. Outcome measures were different delay types counted in days and the influence of four clinical important variables: Presence of alarm symptoms, age...... (≤ or > 60 years), performance of gynecological examination by the GP and notification of cancer suspicion on first referral from GP’s on the diagnostic delay (short delay ≤90 days and long delay >90 days). Results Across cancer type a median total delay of 101 days was observed. The 10% of women...

  1. Cross delay line sensor characterization

    Energy Technology Data Exchange (ETDEWEB)

    Owens, Israel J [Los Alamos National Laboratory; Remelius, Dennis K [Los Alamos National Laboratory; Tiee, Joe J [Los Alamos National Laboratory; Buck, Steven E [Los Alamos National Laboratory; Whittemore, Stephen R [Los Alamos National Laboratory; Thompson, David C [Los Alamos National Laboratory; Shirey, Robert [Los Alamos National Laboratory

    2010-01-01

    There exists a wealth of information in the scientific literature on the physical properties and device characterization procedures for complementary metal oxide semiconductor (CMOS), charge coupled device (CCD) and avalanche photodiode (APD) format detectors. Numerous papers and books have also treated photocathode operation in the context of photomultiplier tube (PMT) operation for either non imaging applications or limited night vision capability. However, much less information has been reported in the literature about the characterization procedures and properties of photocathode detectors with novel cross delay line (XDL) anode structures. These allow one to detect single photons and create images by recording space and time coordinate (X, Y & T) information. In this paper, we report on the physical characteristics and performance of a cross delay line anode sensor with an enhanced near infrared wavelength response photocathode and high dynamic range micro channel plate (MCP) gain (> 10{sup 6}) multiplier stage. Measurement procedures and results including the device dark event rate (DER), pulse height distribution, quantum and electronic device efficiency (QE & DQE) and spatial resolution per effective pixel region in a 25 mm sensor array are presented. The overall knowledge and information obtained from XDL sensor characterization allow us to optimize device performance and assess capability. These device performance properties and capabilities make XDL detectors ideal for remote sensing field applications that require single photon detection, imaging, sub nano-second timing response, high spatial resolution (10's of microns) and large effective image format.

  2. PRECISION TIME-DELAY GENERATOR

    Science.gov (United States)

    Carr, B.J.; Peckham, V.D.

    1959-06-16

    A precision time-delay generator circuit with low jitter is described. The first thyratron has a series resonant circuit and a diode which is connected to the second thyratron. The first thyratron is triggered at the begin-ning of a time delay and a capacitor is discharged through the first thyratron and the diode, thereby, triggering the second thyratron. (T.R.H.) l6l9O The instrument described can measure pressures between sea level and 300,000 ft. The pressure- sensing transducer of the instrument is a small cylindrical tube with a thin foil of titanium-tritium fastened around the inside of the tube. Output is a digital signal which can be used for storage or telemetering more conveniently than an analog signal. (W.D.M.) l6l9l An experimental study was made on rolling contacts in the temperature range of 550 to 1000 deg F. Variables such as material composition, hardness, and operating conditions were investigated in a rolling test stand. Ball bearing tests were run to determine the effect of design parameters, bearing materials, lubricants, and operating conditions. (auth)

  3. Asymptotic Delay Analysis for Cross-Layer Delay-Based Routing in Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Philippe Jacquet

    2007-01-01

    Full Text Available This paper addresses the problem of the evaluation of the delay distribution via analytical means in IEEE 802.11 wireless ad hoc networks. We show that the asymptotic delay distribution can be expressed as a power law. Based on the latter result, we present a cross-layer delay estimation protocol and we derive new delay-distribution-based routing algorithms, which are well adapted to the QoS requirements of real-time multimedia applications. In fact, multimedia services are not sensitive to average delays, but rather to the asymptotic delay distributions. Indeed, video streaming applications drop frames when they are received beyond a delay threshold, determined by the buffer size. Although delay-distribution-based routing is an NP-hard problem, we show that it can be solved in polynomial time when the delay threshold is large, because of the asymptotic power law distribution of the link delays.

  4. Standard Positioning Performance Evaluation of a Single-Frequency GPS Receiver Implementing Ionospheric and Tropospheric Error Corrections

    OpenAIRE

    Alban Rakipi; Bexhet Kamo; Shkelzen Cakaj; Algenti Lala

    2015-01-01

    This paper evaluates the positioning performance of a single-frequency software GPS receiver using Ionospheric and Tropospheric corrections. While a dual-frequency user has the ability to eliminate the ionosphere error by taking a linear combination of observables, a single-frequency user must remove or calibrate this error by other means. To remove the ionosphere error we take advantage of the Klobuchar correction model, while for troposphere error mitigation the Hopfield correction model is...

  5. Large-scale circulation patterns associated with high concentrations of tropospheric ozone in the tropical South Atlantic Ocean

    Science.gov (United States)

    Fakhruzzaman, K. M.; Fishman, J.; Brackett, V. G.; Kendall, J. D.; Justice, C. O.

    1994-01-01

    Several years of satellite observations indicate the presence of enhanced amounts of tropospheric ozone over the tropical South Atlantic during the austral springs. Wide-spread biomass burning is prevalent over Africa and South America during the same time of the year. Another recent satellite technique has identified the locations of fires over the continents. In this study, we present an analysis of the prevailing meteorological conditions when the highest amounts of tropospheric ozone are present.

  6. Analysis of satellite-derived Arctic tropospheric BrO columns in conjunction with aircraft measurements during ARCTAS and ARCPAC

    Directory of Open Access Journals (Sweden)

    S. Choi

    2012-02-01

    Full Text Available We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL. Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7, for solar zenith angle <80° and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow.

  7. Predicting tropospheric ozone and hydroxyl radical in a global, three-dimensional, chemistry, transport, and deposition model

    Energy Technology Data Exchange (ETDEWEB)

    Atherton, C.S.

    1995-01-05

    Two of the most important chemically reactive tropospheric gases are ozone (O{sub 3}) and the hydroxyl radical (OH). Although ozone in the stratosphere is a necessary protector against the sun`s radiation, tropospheric ozone is actually a pollutant which damages materials and vegetation, acts as a respiratory irritant, and is a greenhouse gas. One of the two main sources of ozone in the troposphere is photochemical production. The photochemistry is initiated when hydrocarbons and carbon monoxide (CO) react with nitrogen oxides (NO{sub x} = NO + NO{sub 2}) in the presence of sunlight. Reaction with the hydroxyl radical, OH, is the main sink for many tropospheric gases. The hydroxyl radical is highly reactive and has a lifetime on the order of seconds. Its formation is initiated by the photolysis of tropospheric ozone. Tropospheric chemistry involves a complex, non-linear set of chemical reactions between atmospheric species that vary substantially in time and space. To model these and other species on a global scale requires the use of a global, three-dimensional chemistry, transport, and deposition (CTD) model. In this work, I developed two such three dimensional CTD models. The first model incorporated the chemistry necessary to model tropospheric ozone production from the reactions of nitrogen oxides with carbon monoxide (CO) and methane (CH{sub 4}). The second also included longer-lived alkane species and the biogenic hydrocarbon isoprene, which is emitted by growing plants and trees. The models` ability to predict a number of key variables (including the concentration of O{sub 3}, OH, and other species) were evaluated. Then, several scenarios were simulated to understand the change in the chemistry of the troposphere since preindustrial times and the role of anthropogenic NO{sub x} on present day conditions.

  8. Chemical processes related to net ozone tendencies in the free troposphere

    Directory of Open Access Journals (Sweden)

    H. Bozem

    2017-09-01

    Full Text Available Ozone (O3 is an important atmospheric oxidant, a greenhouse gas, and a hazard to human health and agriculture. Here we describe airborne in situ measurements and model simulations of O3 and its precursors during tropical and extratropical field campaigns over South America and Europe, respectively. Using the measurements, net ozone formation/destruction tendencies are calculated and compared to 3-D chemistry–transport model simulations. In general, observation-based net ozone tendencies are positive in the continental boundary layer and the upper troposphere at altitudes above  ∼  6 km in both environments. On the other hand, in the marine boundary layer and the middle troposphere, from the top of the boundary layer to about 6–8 km altitude, net O3 destruction prevails. The ozone tendencies are controlled by ambient concentrations of nitrogen oxides (NOx. In regions with net ozone destruction the available NOx is below the threshold value at which production and destruction of O3 balance. While threshold NO values increase with altitude, in the upper troposphere NOx concentrations are generally higher due to the integral effect of convective precursor transport from the boundary layer, downward transport from the stratosphere and NOx produced by lightning. Two case studies indicate that in fresh convective outflow of electrified thunderstorms net ozone production is enhanced by a factor 5–6 compared to the undisturbed upper tropospheric background. The chemistry–transport model MATCH-MPIC generally reproduces the pattern of observation-based net ozone tendencies but mostly underestimates the magnitude of the net tendency (for both net ozone production and destruction.

  9. Overview of Global/Regional Models Used to Evaluate Tropospheric Ozone in North America

    Science.gov (United States)

    Johnson, Matthew S.

    2015-01-01

    Ozone (O3) is an important greenhouse gas, toxic pollutant, and plays a major role in atmospheric chemistry. Tropospheric O3 which resides in the planetary boundary layer (PBL) is highly reactive and has a lifetime on the order of days, however, O3 in the free troposphere and stratosphere has a lifetime on the order of weeks or months. Modeling O3 mixing ratios at and above the surface is difficult due to the multiple formation/destruction processes and transport pathways that cause large spatio-temporal variability in O3 mixing ratios. This talk will summarize in detail the global/regional models that are commonly used to simulate/predict O3 mixing ratios in the United States. The major models which will be focused on are the: 1) Community Multi-scale Air Quality Model (CMAQ), 2) Comprehensive Air Quality Model with Extensions (CAMx), 3) Goddard Earth Observing System with Chemistry (GEOS-Chem), 4) Real Time Air Quality Modeling System (RAQMS), 5) Weather Research and Forecasting/Chemistry (WRF-Chem) model, National Center for Atmospheric Research (NCAR)'s Model for OZone And Related chemical Tracers (MOZART), and 7) Geophysical Fluid Dynamics Laboratory (GFDL) AM3 model. I will discuss the major modeling components which impact O3 mixing ratio calculations in each model and the similarities/differences between these models. This presentation is vital to the 2nd Annual Tropospheric Ozone Lidar Network (TOLNet) Conference as it will provide an overview of tools, which can be used in conjunction with TOLNet data, to evaluate the complex chemistry and transport pathways controlling tropospheric O3 mixing ratios.

  10. Chemical processes related to net ozone tendencies in the free troposphere

    Science.gov (United States)

    Bozem, Heiko; Butler, Tim M.; Lawrence, Mark G.; Harder, Hartwig; Martinez, Monica; Kubistin, Dagmar; Lelieveld, Jos; Fischer, Horst

    2017-09-01

    Ozone (O3) is an important atmospheric oxidant, a greenhouse gas, and a hazard to human health and agriculture. Here we describe airborne in situ measurements and model simulations of O3 and its precursors during tropical and extratropical field campaigns over South America and Europe, respectively. Using the measurements, net ozone formation/destruction tendencies are calculated and compared to 3-D chemistry-transport model simulations. In general, observation-based net ozone tendencies are positive in the continental boundary layer and the upper troposphere at altitudes above ˜ 6 km in both environments. On the other hand, in the marine boundary layer and the middle troposphere, from the top of the boundary layer to about 6-8 km altitude, net O3 destruction prevails. The ozone tendencies are controlled by ambient concentrations of nitrogen oxides (NOx). In regions with net ozone destruction the available NOx is below the threshold value at which production and destruction of O3 balance. While threshold NO values increase with altitude, in the upper troposphere NOx concentrations are generally higher due to the integral effect of convective precursor transport from the boundary layer, downward transport from the stratosphere and NOx produced by lightning. Two case studies indicate that in fresh convective outflow of electrified thunderstorms net ozone production is enhanced by a factor 5-6 compared to the undisturbed upper tropospheric background. The chemistry-transport model MATCH-MPIC generally reproduces the pattern of observation-based net ozone tendencies but mostly underestimates the magnitude of the net tendency (for both net ozone production and destruction).

  11. Symposium on the Tropospheric Chemistry of the Antarctic Region: Pre- Conference Abstracts

    Science.gov (United States)

    1991-06-01

    reaction for the halogens F2, Cl 2 and Br 2 . 4 LONG-TERM AEROSOL MEASUREMENTS AT THE SOUTH POLE B.A. Bodhaine, NOAA/ CMDL , 325 Broadway, Boulder, CO...80303-3328 The Climate Monitoring and Diagnostics Laboratory ( CMDL ) program of the National Oceanic and Atmospheric Administration (NOAA) conducts...carbon measurements. COVARIATION OF SOME COMPONENTS OF THE ANTARCTIC TROPOSPHERE B.A. Bodhaine, T. Conway NOAA/ CMDL , 325 Broadway, Boulder, CO 80303

  12. The Impact of Estimating High-Resolution Tropospheric Gradients on Multi-GNSS Precise Positioning.

    Science.gov (United States)

    Zhou, Feng; Li, Xingxing; Li, Weiwei; Chen, Wen; Dong, Danan; Wickert, Jens; Schuh, Harald

    2017-04-03

    Benefits from the modernized US Global Positioning System (GPS), the revitalized Russian GLObal NAvigation Satellite System (GLONASS), and the newly-developed Chinese BeiDou Navigation Satellite System (BDS) and European Galileo, multi-constellation Global Navigation Satellite System (GNSS) has emerged as a powerful tool not only in positioning, navigation, and timing (PNT), but also in remote sensing of the atmosphere and ionosphere. Both precise positioning and the derivation of atmospheric parameters can benefit from multi-GNSS observations. In this contribution, extensive evaluations are conducted with multi-GNSS datasets collected from 134 globally-distributed ground stations of the International GNSS Service (IGS) Multi-GNSS Experiment (MGEX) network in July 2016. The datasets are processed in six different constellation combinations, i.e., GPS-, GLONASS-, BDS-only, GPS + GLONASS, GPS + BDS, and GPS + GLONASS + BDS + Galileo precise point positioning (PPP). Tropospheric gradients are estimated with eight different temporal resolutions, from 1 h to 24 h, to investigate the impact of estimating high-resolution gradients on position estimates. The standard deviation (STD) is used as an indicator of positioning repeatability. The results show that estimating tropospheric gradients with high temporal resolution can achieve better positioning performance than the traditional strategy in which tropospheric gradients are estimated on a daily basis. Moreover, the impact of estimating tropospheric gradients with different temporal resolutions at various elevation cutoff angles (from 3° to 20°) is investigated. It can be observed that with increasing elevation cutoff angles, the improvement in positioning repeatability is decreased.

  13. Evaluation of a new middle-lower tropospheric CO2 product using data assimilation

    Science.gov (United States)

    Tangborn, A.; Strow, L. L.; Imbiriba, B.; Ott, L.; Pawson, S.

    2012-10-01

    Atmospheric CO2 retrievals with peak sensitivity in the mid- to lower troposphere from the Atmospheric Infrared Sounder (AIRS) have been assimilated into the Global Modeling and Assimilation Office (GMAO) constituent assimilation system for the period 1 January 2005 to 31 December 2006. A corresponding model simulation, using identical initial conditions, circulation, and CO2 boundary fluxes was also completed. The analyzed and simulated CO2 fields are compared with surface measurements globally and aircraft measurements over North America. Surface level monthly mean CO2 values show a marked improvement due to the assimilation in the Southern Hemisphere, while less consistent improvements are seen in the Northern Hemisphere. Mean differences with aircraft observations are reduced at all levels, with the largest decrease occurring in the mid-troposphere. The difference standard deviations are reduced slightly at all levels over the ocean, and all levels except the surface layer over land. These initial experiments indicate that the retrieved channel contains useful information on CO2 in the middle to lower troposphere. However, the benefits of assimilating these data are reduced over the land surface, where concentrations are dominated by uncertain local fluxes and where the observation density is quite low. Away from these regions, the study demonstrates the power of the data assimilation technique for evaluating data that are not co-located, in that the improvements in mid-tropospheric CO2 by the sparsely distributed partial-column retrievals are transported by the model to the fixed in-situ surface observation locations in more remote areas.

  14. Relative tropospheric photolysis rates of acetaldehyde and formaldehyde measured at the European Photoreactor Facility

    DEFF Research Database (Denmark)

    Nilsson, Elna Johanna Kristina; Bache-Andreassen, Lihn; Johnson, Matthew Stanley

    2009-01-01

    The photolysis rates of HCHO, DCDO, CH3CHO, and CH3CDO are studied by long-path FTIR spectroscopy in natural tropospheric conditions at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. Average relative photolysis rates jHCHO/jDCDO ) 3.15 ( 0.08 and jCH3CHO/jCH3CDO ) 1.26 ( 0.03 ar...

  15. Causes of interannual variability over the southern hemispheric tropospheric ozone maximum

    Science.gov (United States)

    Liu, Junhua; Rodriguez, Jose M.; Steenrod, Stephen D.; Douglass, Anne R.; Logan, Jennifer A.; Olsen, Mark A.; Wargan, Krzysztof; Ziemke, Jerald R.

    2017-03-01

    We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hPa), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hPa. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hPa in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hPa and drops to less than half but is still significant at 430 hPa. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hPa in austral winter, and emissions have little influence.

  16. Kinetics programs for simulation of tropospheric photochemistry on the global scale

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, S.; Kao, C.Y.J. [Los Alamos National Lab., NM (US); Turco, R.P.; Zhao, X.P. [California Univ., Los Angeles, CA (US). Dept. of Atmospheric Sciences

    1993-08-01

    The study of tropospheric kinetics underlies global change because key greenhouse gases are photochemically active. Modeling of tropospheric chemistry on a global scale is essential because some indirect greenhouse gases are short-lived and interact in a non-linear fashion. It is also extremely challenging, however; the global change grid is extensive in both the physical and temporal domains, and critical lower atmospheric species include the organics and their oxidized derivatives, which are numerous. Several types of optimization may be incorporated into kinetics modules to enhance their ability to simulate the complete lower atmospheric gas phase chemical system. (1) The photochemical integrator can be accelerated by avoiding matrix and iterative solutions and by establishing families. Accuracy and mass conservation are sacrificed in the absence of iteration, but atom balancing is restorable post hoc. (2) Chemistry can be arranged upon the massive grid to exploit parallel processing, and solutions to its continuity equations can be automated to permit experimentation with species and reaction lists or family definitions. Costs in programming effort will be incurred in these cases. (3) Complex hydrocarbon decay sequences can be streamlined either through structural lumping methods descended from smog investigations, which require considerable calibration, or by defining surrogates for classes of compounds, with a loss in constituent detail. From among the available options, the most advantageous permutations will vary with the specific nature of any eventual global scale study, and there is likely to be demand for many approaches. Tracer transport codes serve as a foundation upon which tropospheric chemistry packages will be tested. Encroachment of the NO{sub x} sphere of influence upon tropical rain forests and the upper free troposphere are two examples of specific problems to which full three-dimensional chemical simulations might be applied.

  17. The Ozone Budget in the Upper Troposphere from Global Modeling Initiative (GMI)Simulations

    Science.gov (United States)

    Rodriquez, J.; Duncan, Bryan N.; Logan, Jennifer A.

    2006-01-01

    Ozone concentrations in the upper troposphere are influenced by in-situ production, long-range tropospheric transport, and influx of stratospheric ozone, as well as by photochemical removal. Since ozone is an important greenhouse gas in this region, it is particularly important to understand how it will respond to changes in anthropogenic emissions and changes in stratospheric ozone fluxes.. This response will be determined by the relative balance of the different production, loss and transport processes. Ozone concentrations calculated by models will differ depending on the adopted meteorological fields, their chemical scheme, anthropogenic emissions, and treatment of the stratospheric influx. We performed simulations using the chemical-transport model from the Global Modeling Initiative (GMI) with meteorological fields from (It)h e NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), (2) the atmospheric GCM from NASA's Global Modeling and Assimilation Office(GMAO), and (3) assimilated winds from GMAO . These simulations adopt the same chemical mechanism and emissions, and adopt the Synthetic Ozone (SYNOZ) approach for treating the influx of stratospheric ozone -. In addition, we also performed simulations for a coupled troposphere-stratosphere model with a subset of the same winds. Simulations were done for both 4degx5deg and 2degx2.5deg resolution. Model results are being tested through comparison with a suite of atmospheric observations. In this presentation, we diagnose the ozone budget in the upper troposphere utilizing the suite of GMI simulations, to address the sensitivity of this budget to: a) the different meteorological fields used; b) the adoption of the SYNOZ boundary condition versus inclusion of a full stratosphere; c) model horizontal resolution. Model results are compared to observations to determine biases in particular simulations; by examining these comparisons in conjunction with the derived budgets, we may pinpoint

  18. FRESCO+: an improved O2 A-band cloud retrieval algorithm for tropospheric trace gas retrievals

    Science.gov (United States)

    Wang, P.; Stammes, P.; van der A, R.; Pinardi, G.; van Roozendael, M.

    2008-11-01

    The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. We compared FRESCO+ and FRESCO effective cloud fractions and cloud pressures using simulated spectra and one month of GOME measured spectra. As expected, FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar/lidar measurements of clouds show that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. The effect of FRESCO+ cloud parameters on O3 and NO2 vertical column density (VCD) retrievals is studied using SCIAMACHY data and ground-based DOAS measurements. We find that the FRESCO+ algorithm has a significant effect on tropospheric NO2 retrievals but a minor effect on total O3 retrievals. The retrieved SCIAMACHY tropospheric NO2 VCDs using FRESCO+ cloud parameters (v1.1) are lower than the tropospheric NO2VCDs which used FRESCO cloud parameters (v1.04), in particular over heavily polluted areas with low clouds. The difference between SCIAMACHY tropospheric NO2 VCDs v1.1 and ground-based MAXDOAS measurements performed in Cabauw, The Netherlands, during the DANDELIONS campaign is about -2.12×1014molec cm-2.

  19. FRESCO+: an improved O2 A-band cloud retrieval algorithm for tropospheric trace gas retrievals

    Directory of Open Access Journals (Sweden)

    M. van Roozendael

    2008-11-01

    Full Text Available The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. We compared FRESCO+ and FRESCO effective cloud fractions and cloud pressures using simulated spectra and one month of GOME measured spectra. As expected, FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar/lidar measurements of clouds show that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. The effect of FRESCO+ cloud parameters on O3 and NO2 vertical column density (VCD retrievals is studied using SCIAMACHY data and ground-based DOAS measurements. We find that the FRESCO+ algorithm has a significant effect on tropospheric NO2 retrievals but a minor effect on total O3 retrievals. The retrieved SCIAMACHY tropospheric NO2 VCDs using FRESCO+ cloud parameters (v1.1 are lower than the tropospheric NO2VCDs which used FRESCO cloud parameters (v1.04, in particular over heavily polluted areas with low clouds. The difference between SCIAMACHY tropospheric NO2 VCDs v1.1 and ground-based MAXDOAS measurements performed in Cabauw, The Netherlands, during the DANDELIONS campaign is about −2.12×1014molec cm−2.

  20. Detection of $^{133}$Xe from the Fukushima nuclear power plant in the upper troposphere above Germany

    OpenAIRE

    Simgen, Hardy; Arnold, Frank; Aufmhoff, Heinfried; Baumann, Robert; Kaether, Florian; Lindemann, Sebastian; Rauch, Ludwig; Schlager, Hans; Schlosser, Clemens; Schumann, Ulrich

    2013-01-01

    After the accident in the Japanese Fukushima Dai-ichi nuclear power plant in March 2011 large amounts of radioactivity were released and distributed in the atmosphere. Among them were also radioactive noble gas isotopes which can be used as tracers to test global atmospheric circulation models. This work presents unique measurements of the radionuclide $^{133}$Xe from Fukushima in the upper troposphere above Germany. The measurements involve air sampling in a research jet aircraft followed by...

  1. The meteorological environment of the tropospheric ozone maximum over the tropical South Atlantic Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Krishnamurti, T.N.; Fuelberg, H.E.; Sinha, M.C. [Florida State Univ., Tallahassee, FL (United States)] [and others

    1993-06-20

    Atmospheric flow patterns are examined over the South Atlantic Ocean where a maximum of tropospheric ozone has been observed just west of southern Africa. The authors investigate the flow climatology during October and perform a case study for 6 days during October 1989. Analyses from the European Center for Medium-Range Weather Forecasting are employed, and a high-resolution global spectral model is used to prepare forecasts during the period. Horizontal and vertical motions are examined and used to prepare three-dimensional backward trajectories from the region of greatest ozone. An initially zonally symmetric distribution of ozone is treated as a passive tracer and advected by three dimensional flows forecast by the global model. Results from the passive tracer and advected by three-dimensional advection alone can produce a maximum of tropospheric ozone in the observed location. In addition, the trajectories suggest that by-products of biomass burning could be transported to the area of maximum ozone. Low-level flow from commonly observed regions of burning in Africa streams westward to the area of interest. Over Brazil, if the burning by-products are carried into the upper troposphere by convective process, they then could be transported eastward to the ozone feature in approximately 5 days. There is considerable subsidence over the tropical southern Atlantic, such that stratospheric influences also are a factor in producing the ozone maximum. Both planetary-scale and transient synoptic-scale circulation features play major roles in the various transport processes that influence the region. In summary, the observed tropospheric ozone maximum appears to be caused by a complex set of horizontal and vertical advections, transport from regions of biomass burning, and stratospheric influences. 61 refs., 17 figs.

  2. Tropospheric ozone effects on chemical composition and decomposition rate of Quercus ilex L. leaves.

    Science.gov (United States)

    Baldantoni, Daniela; Fagnano, Massimo; Alfani, Anna

    2011-02-01

    We determined the effects of tropospheric ozone on the chemical composition of Quercus ilex L. leaves and their decomposition, with a view to assessing the influence of ozone on nutrient cycling and the sustainability of Mediterranean holm oak forests. Forming one of the most widespread thermophilous vegetation communities in the area, Q. ilex is a dominant and widespread evergreen oak in the Mediterranean, where concentrations of tropospheric ozone are particularly high. The dynamics of carbon, nitrogen, lignin and cellulose concentrations were monitored for six months during the decomposition of leaves from plants subjected to controlled ozone exposure in open-top chambers. Ozone-exposed leaves, compared to unexposed leaves, showed no significant differences in C, N, lignin and cellulose concentrations prior to the incubation in mesocosms. However, during decomposition, leaves from plants exposed to ozone lost C significantly more slowly and showed a higher C/N ratio than unexposed leaves. Ozone exposure significantly slowed down the decomposition rate, indicating a negative effect of tropospheric ozone on nutrient cycling, which may reduce long-term sustainability of the holm oak forest. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Upper Troposphere Lower Stratosphere structure during convective systems using GPS radio occultations

    DEFF Research Database (Denmark)

    Biondi, Riccardo

    The deep convective systems play a fundamental role in atmospheric circulation and climate. Thunderstorms and meso-scale convective systems produce fast vertical transport, redistributing water vapor and trace gases and influencing the thermal structure of the upper troposphere and lower stratosp......The deep convective systems play a fundamental role in atmospheric circulation and climate. Thunderstorms and meso-scale convective systems produce fast vertical transport, redistributing water vapor and trace gases and influencing the thermal structure of the upper troposphere and lower...... stratosphere (UTLS) contributing to the troposphere-stratosphere transport and affecting the Earth global circulation and the climate changes. The Global Positioning System (GPS) Radio Occultation (RO) technique enables measurement of atmospheric density structure in any meteorological condition...... providing a clear signature of these processes on the atmosphere. However the signal is not sensitive enough to detect the variation of water vapor in the UTLS. The ongoing GPS RO missions do not provide a suitable Earth coverage in order to allow a systematic study of convective systems and an increase...

  4. Structure and Variability of Water Vapor in the Upper Troposphere and Lower Stratosphere

    Science.gov (United States)

    Salby, Murry L.

    2003-01-01

    An algorithm has been developed to synoptically-map asynoptic measurements, while rejecting small-scale under-sampled variance that is intrinsic to satellite measurements of water vapor, cloud, and other convective properties. The algorithm has been validated against high-resolution Global Cloud Imagery (GCI) , constructed from 6 satellites simultaneously viewing the global convective pattern. It has been applied to synoptically map Upper-tropospheric humidity (UTH) from UARS/MLS. Mapped distributions of UTH have been used, jointly with the GCI, to study how the upper troposphere is humidified. The time-mean distribution of UTH is spatially correlated to the time-mean distribution of cold cloud fraction eta(sub c) (T less than 230 K). Regions of large UTH coincide with regions of large eta(sub c), which mark deep convection. They also coincide with regions of reduced vertical stability, in which the vertical gradient of Theta is weakened by convective mixing. Coldest cloud cover is attended convective overshoots above the local tropopause, which is simultaneously coldest and highest. Together, these features reflect the upper-troposphere being ventilated by convection, which mixes in air from lower levels.

  5. Removal of chlorofluorocarbons by increased mass exchange between the stratosphere and troposphere in a changing climate.

    Science.gov (United States)

    Butchart, N; Scaife, A A

    2001-04-12

    Chlorofluorocarbons (CFCs), along with bromine compounds, have been unequivocally identified as being responsible for most of the anthropogenic destruction of stratospheric ozone. With curbs on emissions of these substances, the recovery of the ozone layer will depend on their removal from the atmosphere. As CFCs have no significant tropospheric removal process, but are rapidly photolysed above the lower stratosphere, the timescale for their removal is set mainly by the rate at which air is transported from the troposphere into the stratosphere. Using a global climate model we predict that, in response to the projected changes in greenhouse-gas concentrations during the first half of the twenty-first century, this rate of mass exchange will increase by 3% per decade. This increase is due to more vigorous extra-tropical planetary waves emanating from the troposphere. We estimate that this increase in mass exchange will accelerate the removal of CFCs to an extent that recovery to levels currently predicted for 2050 and 2080 will occur 5 and 10 years earlier, respectively.

  6. Snow-sourced bromine and its implications for polar tropospheric ozone

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-08-01

    Full Text Available In the last two decades, significant depletion of boundary layer ozone (ozone depletion events, ODEs has been observed in both Arctic and Antarctic spring. ODEs are attributed to catalytic destruction by bromine radicals (Br plus BrO, especially during bromine explosion events (BEs, when high concentrations of BrO periodically occur. However, neither the exact source of bromine nor the mechanism for sustaining the observed high BrO concentrations is completely understood. Here, by considering the production of sea salt aerosol from snow lying on sea ice during blowing snow events and the subsequent release of bromine, we successfully simulate the BEs using a global chemistry transport model. We find that heterogeneous reactions play an important role in sustaining a high fraction of the total inorganic bromine as BrO. We also find that emissions of bromine associated with blowing snow contribute significantly to BrO at mid-latitudes. Modeled tropospheric BrO columns generally compare well with the tropospheric BrO columns retrieved from the GOME satellite instrument (Global Ozone Monitoring Experiment. The additional blowing snow bromine source, identified here, reduces modeled high latitude lower tropospheric ozone amounts by up to an average 8% in polar spring.

  7. Convection Signatures and the Age of Air in the Upper Troposphere

    Science.gov (United States)

    Perring, A. E.; Bertram, T. H.; Wooldridge, P. J.; Cohen, R. C.; Crounse, J. D.; Wennberg, P. O.; Dibb, J.; Scheuer, E.; Walega, J.; Fried, A.; Vay, S. A.; Hiekes, B.; Kim, S.; Huey, G.; Porter, M.; Fuelberg, H.

    2005-12-01

    Observations of Nitrogen Dioxide (NO2) over the continental United States reveal strong signatures of convective pumping of both boundary layer and lighting NOx to the Upper Troposphere (UT) (8-12.5km) during the summer (INTEX-NA July-August 2004). This influence may require adjustments to a priori assumptions about NO2 profiles used in OMI or SCIAMACHY NO2 retrievals. As expected, similar profiles during the winter (PAVE January 2005) show no signs of enhanced NOx in the UT. Quantifying the role of convection and lightning is a long standing challenge for tropospheric chemistry. Another challenge has been to provide a clock indicating the time that air has spent in the free troposphere since convection. Following on the suggestion of Jaegle et al. [1998] that convective injection of boundary layer and lightning NOx and concurrent precipitation scavenging of HNO3 offers an initial condition that can be used to provide timing information, we use the ratio of NOx/HNO3 as an indicator of convective influence and a measure of the timing of that influence.

  8. Link between Enhanced Arctic tropospheric BrO observed by Aura OMI and meteorological conditions

    Science.gov (United States)

    Choi, S.; Joiner, J.; Theys, N.; Salawitch, R. J.; Wales, P.; Canty, T. P.; Chance, K.; Suleiman, R. M.; Palm, S. P.; Cullather, R. I.; Darmenov, A.; da Silva, A.; Kurosu, T. P.

    2015-12-01

    Bromine radicals (Br + BrO) are important species owing to the ability to destroy ozone catalytically. They may also impact oxidative pathways of many trace gases including dimethylsulfide (DMS) and mercury. Bromine monoxide (BrO) is the most commonly observed bromine radical species. Since it absorbs ultraviolet (UV) radiation, it can be observed using remote sensing technique including Differential Optical Absorption Spectroscopy (DOAS). Previous studies have reported rapid enhancements tropospheric BrO (so called "bromine explosion") connected to near-surface ozone depletion events during springtime in the Arctic. Space-based observation of BrO through Ozone Monitoring Instrument (OMI) is an excellent tool for studying bromine chemistry particularly for the Arctic due to its frequent observations at high latitudes. We derive tropospheric columns BrO by subtracting estimates of stratospheric column BrO from OMI total column BrO and air mass factor (AMF) correction, and analyze the tropospheric columns BrO in conjunction with Modern-Era Retrospective analysis for Research and Application (MERRA) meteorological fields provided by NASA Global Modeling and Assimilation Office (GMAO) in order to investigate a link between bromine explosion and near-surface meteorological factors.

  9. Exposure to moderate concentrations of tropospheric ozone impairs tree stomatal response to carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Onandia, Gabriela [Department of Plant and Environmental Sciences, University of Gothenburg, P. O. Box 461, SE-405 30 Goeteborg (Sweden); Cavanilles Institute of Biodiversity and Evolutionary Biology, Department of Microbiology and Ecology, University of Valencia, E-46100 Burjassot, Valencia (Spain); Olsson, Anna-Karin; Barth, Sabine [Department of Plant and Environmental Sciences, University of Gothenburg, P. O. Box 461, SE-405 30 Goeteborg (Sweden); King, John S. [Department of Forestry and Environmental Resources, Campus Box 8002, North Carolina State University, Raleigh, NC 27695 (United States); Uddling, Johan, E-mail: johan.uddling@dpes.gu.se [Department of Plant and Environmental Sciences, University of Gothenburg, P. O. Box 461, SE-405 30 Goeteborg (Sweden)

    2011-10-15

    With rising concentrations of both atmospheric carbon dioxide (CO{sub 2}) and tropospheric ozone (O{sub 3}), it is important to better understand the interacting effects of these two trace gases on plant physiology affecting land-atmosphere gas exchange. We investigated the effect of growth under elevated CO{sub 2} and O{sub 3}, singly and in combination, on the primary short-term stomatal response to CO{sub 2} concentration in paper birch at the Aspen FACE experiment. Leaves from trees grown in elevated CO{sub 2} and/or O{sub 3} exhibited weaker short-term responses of stomatal conductance to both an increase and a decrease in CO{sub 2} concentration from current ambient level. The impairement of the stomatal CO{sub 2} response by O{sub 3} most likely developed progressively over the growing season as assessed by sap flux measurements. Our results suggest that expectations of plant water-savings and reduced stomatal air pollution uptake under rising atmospheric CO{sub 2} may not hold for northern hardwood forests under concurrently rising tropospheric O{sub 3}. - Exposure to moderate concentrations of tropospheric ozone impairs stomatal CO{sub 2} responsiveness of birch in the Aspen FACE experiment.

  10. Laboratory Studies of the Tropospheric Loss Processes for Acetic and Peracetic Acid

    Science.gov (United States)

    Orlando, J. J.; Tyndall, G. S.

    2002-12-01

    Organic acids are ubiquitous components of tropospheric air and contribute to acid precipitation, particularly in remote regions. These species are present in the troposphere as the result of direct emissions from anthropogenic and biogenic sources, and as the result of photochemical processing of hydrocarbons. Production of organic acids can occur following ozonolysis of unsaturated hydrocarbons, while both organic acids and peroxyacids are formed from the reactions of HO2 with acylperoxy radicals. For example, both acetic and peracetic acid are known products of the reaction of HO2 with acetylperoxy radicals. In this paper, data relevant to the gas-phase tropospheric destruction of both acetic and peracetic acid are reported, including studies of their UV absorption spectra and of their rate coefficients for reaction with OH radicals. The data, the first of their kind for peracetic acid, show that the gas-phase lifetime of this species will be on the order of 10 days, with OH reaction occurring more rapidly than photolysis. Data on the rate coefficient for reaction of OH with acetic acid appear to resolve some conflicting data in the previous literature, and show 1) that reaction of OH with the acetic acid dimer is slow compared to the monomer and 2) that the rate coefficient possesses a negative temperature dependence near room temperature.

  11. Influence of isentropic transport on seasonal ozone variations in the lower stratosphere and subtropical upper troposphere

    Science.gov (United States)

    Jing, P.; Cunnold, D. M.; Yang, E.-S.; Wang, H.-J.

    2005-01-01

    The isentropic cross-tropopause ozone transport has been estimated in both hemispheres in 1999 based on the potential vorticity mapping of Stratospheric Aerosol and Gas Experiment 11 ozone measurements and contour advection calculations using the NASA Goddard Space Flight Center Global and Modeling Assimilation Office analysis. The estimated net isentropic stratosphere-to-troposphere ozone flux is approx.118 +/- 61 x 10(exp9)kg/yr globally within the layer between 330 and 370 K in 1999; 60% of it is found in the Northern Hemisphere, and 40% is found in the Southern Hemisphere. The monthly average ozone fluxes are strongest in summer and weakest in winter in both hemispheres. The seasonal variations of ozone in the lower stratosphere (LS) and upper troposphere (UT) have been analyzed using ozonesonde observations from ozonesonde stations in the extratropics and subtropics, respectively. It is shown that observed ozone levels increase in the UT over subtropical ozonesonde stations and decrease in the LS over extratropical stations in late spring/early summer and that the ozone increases in the summertime subtropical UT are unlikely to be explained by photochemical ozone production and diabatic transport alone. We conclude that isentropic transport is a significant contributor to ozone levels in the subtropical upper troposphere, especially in summer.

  12. Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

    Science.gov (United States)

    Stevens, Bjorn; Brogniez, Hélène; Kiemle, Christoph; Lacour, Jean-Lionel; Crevoisier, Cyril; Kiliani, Johannes

    2017-11-01

    In situ, airborne and satellite measurements are used to characterize the structure of water vapor in the lower tropical troposphere—below the height, z_*, of the triple-point isotherm, T_*. The measurements are evaluated in light of understanding of how lower-tropospheric water vapor influences clouds, convection and circulation, through both radiative and thermodynamic effects. Lower-tropospheric water vapor, which concentrates in the first few kilometers above the boundary layer, controls the radiative cooling profile of the boundary layer and lower troposphere. Elevated moist layers originating from a preferred level of convective detrainment induce a profile of radiative cooling that drives circulations which reinforce such features. A theory for this preferred level of cumulus termination is advanced, whereby the difference between T_* and the temperature at which primary ice forms gives a `first-mover advantage' to glaciating cumulus convection, thereby concentrating the regions of the deepest convection and leading to more clouds and moisture near the triple point. A preferred level of convective detrainment near T_* implies relative humidity reversals below z* which are difficult to identify using retrievals from satellite-borne microwave and infrared sounders. Isotopologues retrievals provide a hint of such features and their ability to constrain the structure of the vertical humidity profile merits further study. Nonetheless, it will likely remain challenging to resolve dynamically important aspects of the vertical structure of water vapor from space using only passive sensors.

  13. What Do Observational Datasets Say about Modeled Tropospheric Temperature Trends since 1979?

    Directory of Open Access Journals (Sweden)

    David Douglass

    2010-09-01

    Full Text Available Updated tropical lower tropospheric temperature datasets covering the period 1979–2009 are presented and assessed for accuracy based upon recent publications and several analyses conducted here. We conclude that the lower tropospheric temperature (TLT trend over these 31 years is +0.09 ± 0.03 °C decade−1. Given that the surface temperature (Tsfc trends from three different groups agree extremely closely among themselves (~ +0.12 °C decade−1 this indicates that the “scaling ratio” (SR, or ratio of atmospheric trend to surface trend: TLT/Tsfc of the observations is ~0.8 ± 0.3. This is significantly different from the average SR calculated from the IPCC AR4 model simulations which is ~1.4. This result indicates the majority of AR4 simulations tend to portray significantly greater warming in the troposphere relative to the surface than is found in observations. The SR, as an internal, normalized metric of model behavior, largely avoids the confounding influence of short-term fluctuations such as El Niños which make direct comparison of trend magnitudes less confident, even over multi-decadal periods.

  14. Non-Migrating Tidal Effects on the Upper Atmosphere: New Tropospheric Forcing

    Science.gov (United States)

    Hagan, M. E.; Maute, A. I.; Zhang, X.; Forbes, J. M.; Roble, R. G.

    2009-12-01

    Space-borne observations of thermospheric temperature, wind, and airglow measurements, as well as ionosphereric density and drift diagnostics exhibit notable longitudinal variations during geomagnetically quiescent conditions. Many of these variations can been attributed to nonmigrating tides of tropospheric origin and have been successfully replicated by the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) when it includes Global-Scale Wave Model (GSWM-02) forcing at the lower boundary (ca. 30 km). However, these TIME-GCM/GSWM-02 results do not capture the observed seasonal variability of the nonmigrating tides. Recently, Zhang et al. (2009a,b) developed new tropospheric tidal forcing based upon International Satellite Cloud Climatology Project (ISCCP) and Tropical Rainfall Measuring Mission (TRMM) observations and reported updated GSWM-09 nonmigrating tidal climatologies. Herein, we present signatures of nonmigrating tides from a new set of TIME-GCM/GSWM-09 simulations and assess whether this updated model is better able to capture the observed seasonal variations of these tides in the thermosphere and ionosphere during solar minimum conditions. Zhang, X., J.M. Forbes, and M.E. Hagan (2009a) Longitudinal Variation of Tides in the MLT Region: Part 1, Tides Driven by Troposphere Solar Radiative Heating, submitted to Journal of Geophysical Research. Zhang, X., J.M. Forbes, and M.E. Hagan (2009b) Longitudinal Variation of Tides in the MLT Region: Part 2, Relative Effects of Solar Radiative and Latent Heating, submitted to Journal of Geophysical Research.

  15. Momentum flux associated with gravity waves in the low-latitude troposphere

    Directory of Open Access Journals (Sweden)

    S. R. Prabhakaran Nayar

    Full Text Available The vertical fluxes of horizontal momentum at tropospheric heights are calculated for four days, 25–28 August 1999. The mean zonal wind during these days show the presence of strong westward wind at the upper troposphere. Both the symmetric beam radar method and the power spectral method of evaluation of vertical flux of zonal and meridional momentum shows nearly the same result for quiet conditions. The temporal evolution of the momentum flux is estimated for a day with strong zonal shear and convection. These results indicate that on 28 August 1999, the strong downward vertical wind in the lower altitude range is associated with upward vertical flux of zonal momentum, and strong upward vertical wind is associated with downward vertical flux. Similarly, the strong shear in zonal wind is associated with the increase in negative values in vertical flux in the upper troposphere. Analysis of the role of wave periods in the transport of momentum flux indicates that the vertical momentum flux magnitude is not evenly distributed in all wave periods, but instead it peaks at certain wave periods in the range 10 to 100 min.

    Key words. Meteorology and atmospheric dynamics (convective process; tropical meteorology; precipitation

  16. Airborne observations of aerosol microphysical properties and particle ageing processes in the troposphere above Europe

    Directory of Open Access Journals (Sweden)

    T. Hamburger

    2012-12-01

    Full Text Available In-situ measurements of aerosol microphysical properties were performed in May 2008 during the EUCAARI-LONGREX campaign. Two aircraft, the FAAM BAe-146 and DLR Falcon 20, operated from Oberpfaffenhofen, Germany. A comprehensive data set was obtained comprising the wider region of Europe north of the Alps throughout the whole tropospheric column. Prevailing stable synoptic conditions enabled measurements of accumulating emissions inside the continental boundary layer reaching a maximum total number concentration of 19 000 particles cm−3 stp. Ultra-fine particles as indicators for nucleation events were observed within the boundary layer during high pressure conditions and after updraft of emissions induced by frontal passages above 8 km altitude in the upper free troposphere. Aerosol ageing processes during air mass transport are analysed using trajectory analysis. The ratio of particles containing a non-volatile core (250 °C to the total aerosol number concentration was observed to increase within the first 12 to 48 h from the particle source from 50 to 85% due to coagulation. Aged aerosol also features an increased fraction of accumulation mode particles of approximately 40% of the total number concentration. The presented analysis provides an extensive data set of tropospheric aerosol microphysical properties on a continental scale which can be used for atmospheric aerosol models and comparisons of satellite retrievals.

  17. Evidence of Convective Redistribution of Carbon Monoxide in Aura Tropospheric Emission Sounder (TES) and Microwave Limb Sounder (MLS) Observations

    Science.gov (United States)

    Manyin, Michael; Douglass, Anne; Schoeberl, Mark

    2010-01-01

    Vertical convective transport is a key element of the tropospheric circulation. Convection lofts air from the boundary layer into the free troposphere, allowing surface emissions to travel much further, and altering the rate of chemical processes such as ozone production. This study uses satellite observations to focus on the convective transport of CO from the boundary layer to the mid and upper troposphere. Our hypothesis is that strong convection associated with high rain rate regions leads to a correlation between mid level and upper level CO amounts. We first test this hypothesis using the Global Modeling Initiative (GMI) chemistry and transport model. We find the correlation is robust and increases as the precipitation rate (the strength of convection) increases. We next examine three years of CO profiles from the Tropospheric Emission Sounder (TES) and Microwave Limb Sounder (MLS) instruments aboard EOS Aura. Rain rates are taken from the Tropical Rainfall Measuring Mission (TRMM) 3B-42 multi-satellite product. Again we find a correlation between mid-level and upper tropospheric CO, which increases with rain rate. Our result shows the critical importance of tropical convection in coupling vertical levels of the troposphere in the transport of trace gases. The effect is seen most clearly in strong convective regions such as the Inter-tropical Convergence Zone.

  18. Northern Winter Climate Change: Assessment of Uncertainty in CMIP5 Projections Related to Stratosphere-Troposphere Coupling

    Science.gov (United States)

    Manzini, E.; Karpechko, A.Yu.; Anstey, J.; Shindell, Drew Todd; Baldwin, M.P.; Black, R.X.; Cagnazzo, C.; Calvo, N.; Charlton-Perez, A.; Christiansen, B.; hide

    2014-01-01

    Future changes in the stratospheric circulation could have an important impact on northern winter tropospheric climate change, given that sea level pressure (SLP) responds not only to tropospheric circulation variations but also to vertically coherent variations in troposphere-stratosphere circulation. Here we assess northern winter stratospheric change and its potential to influence surface climate change in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) multimodel ensemble. In the stratosphere at high latitudes, an easterly change in zonally averaged zonal wind is found for the majority of the CMIP5 models, under the Representative Concentration Pathway 8.5 scenario. Comparable results are also found in the 1% CO2 increase per year projections, indicating that the stratospheric easterly change is common feature in future climate projections. This stratospheric wind change, however, shows a significant spread among the models. By using linear regression, we quantify the impact of tropical upper troposphere warming, polar amplification, and the stratospheric wind change on SLP. We find that the intermodel spread in stratospheric wind change contributes substantially to the intermodel spread in Arctic SLP change. The role of the stratosphere in determining part of the spread in SLP change is supported by the fact that the SLP change lags the stratospheric zonally averaged wind change. Taken together, these findings provide further support for the importance of simulating the coupling between the stratosphere and the troposphere, to narrow the uncertainty in the future projection of tropospheric circulation changes.

  19. Overview of new GNSS tropospheric products for GNSS-meteorology and their assessment at Geodetic Observatory Pecny (CZ)

    Science.gov (United States)

    Dousa, J.; Vaclavovic, P.; Gyori, G.

    2012-12-01

    Geodetic Observatory Pecný (GOP) has a long-term experience in the estimation of precise tropospheric parameters from GNSS permanent stations, in particular under the limited timelines of near real time. More than a decade, the GOP zenith total delays (ZTD) contributed to various projects in Europe (COST-716, TOUGH, E-GVAP, E-GVAP II) and the operational ZTD hourly updated product flows via the meteorological observation exchange network - GTS - to the end users worldwide. Currently, the GOP regional ZTD product is operationally assimilated in Météo France and UK MetOffice at least and further exploited in various ways at many other meteorological institutions. New developments at GOP over last three years consist of a) implementation and assessment of the global hourly ZTD product of about 170 stations, b) implementation of routine multi-GNSS (GPS+GLONASS) ZTD European product, and c) implementation of ultra-fast/real-time ZTD product. The GOP global ZTD product has been implemented on request of the meteorological institutions running global numerical weather forecasting models. The global ZTD product was seriously evaluated over ten months (Oct 2009 - Aug 2011) when compared to reprocessed EUREF and IGS ZTDs, radiosondes and ZTDs derived from UK MetOffice's global numerical weather model. After the evaluation (and on special request of UK MetOffice) the product has been switched from testing to operational status within the framework of the EUMETNET EIG GPS Water Vapour Programme (E-GVAP) and officially disseminated via the GTS network. The GOP multi-GNSS ZTD solution has been tested since 2009 shortly after developing GOP ultra-rapid GPS+GLONASS orbits for the International GNSS Service (IGS). A specific bias of mean value 1.5 mm was identified between GPS- and GLONASS-only ZTD at that time, and relation to the IGS05 antenna phase centre offset and variation models (PCO+PCV) identified. Consequently, the implementation of a routine operation has been done

  20. Investigating vertical distribution patterns of lower tropospheric PM2.5 using unmanned aerial vehicle measurements

    Science.gov (United States)

    Li, Xiao-Bing; Wang, Dong-Sheng; Lu, Qing-Chang; Peng, Zhong-Ren; Wang, Zhan-Yong

    2018-01-01

    A lightweight unmanned aerial vehicle (UAV) was outfitted with miniaturized sensors to investigate the vertical distribution patterns and sources of fine aerosol particles (PM2.5) within the 1 000 m lower troposphere. A total of 16 UAV flights were conducted in the Yangtze River Delta (YRD) region, China, from the summer to winter in 2014. The associated ground-level measurements from two environmental monitoring stations were also used for background analysis. The results show that ground-level PM2.5 concentrations demonstrated a decreasing trend from Feb. to Jul. and an increasing trend from Aug. to Jan. (the following year). Higher PM2.5 concentrations during the day were mainly observed in the morning (Local Time, LT 05-09) in the spring and summer. However, higher PM2.5 concentrations occurred mainly in the late afternoon and evening (LT 16-20) in the autumn and winter, excluding severe haze pollution days when higher PM2.5 concentrations were also observed during the morning periods. Lower tropospheric PM2.5 concentrations exhibited similar diurnal vertical distribution patterns from the summer to winter. The PM2.5 concentrations decreased with height in the morning, with significantly large vertical gradients from the summer to winter. By contrast, the aerosol particles were well mixed with PM2.5 concentrations of lower than 35 μg ṡm-3 in the early afternoon (LT 12-16) due to sufficient expansions of the planetary boundary layer. The mean vertical PM2.5 concentrations within the 1 000 m lower troposphere in the morning were much larger in the winter (∼87.5 μg ṡm-3) than in the summer and autumn (∼20 μg ṡm-3). However, subtle differences of ∼11 μg ṡm-3 in the mean vertical PM2.5 concentrations were observed in the early afternoon from the summer to winter. The vertical distribution patterns of black carbon and its relationships with PM2.5 indicated that the lower tropospheric aerosol particles might be mainly derived from fossil