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Regional Profiles and Precipitation Retrievals and Analysis Using FY-3C MWHTS  [PDF]
Jieying He, Shengwei Zhang
Atmospheric and Climate Sciences (ACS) , 2016, DOI: 10.4236/acs.2016.62023
Abstract: The 89 and 150 GHz channels operated in window are sensitive to precipitation and humidity. The 183 GHz humidity-sensitive channels and 118 GHz temperature-sensitive channels of the Microwave Humidity and Temperature Sounder (MWHTS) on the Chinese Feng Yun 3C MWHTS (FY-3C MWHTS) polar-orbit meteorological satellite responds in part to precipitation. Combining 118 and 183 GHz channels, the paper develops a passive sub-millimeter atmospheric profile and precipitation retrievals algorithm for MWHTS onboard the FY-3C (Feng Yun-3C) satellite. The retrieval algorithm employs a number of back propagation neural network estimators trained and evaluated using the validated global reference physical model NCEP/WRF/ARTS and works for land and seawater with latitude between -40 to 40 degree. NCEP data per 6 hours were downloaded to run the Weather Research and Forecast model WRF, and to derive the typical precipitation data for the whole world. The Atmospheric Radiative Transfer Simulator ARTS is feasible for performing simulations of atmospheric radiative transfer. The results show that the profile retrievals using BP-NN algorithm has the best correlation with those from radiosonde, which is less than 18% and 1 K of root mean square error, respectively. For precipitation rate retrievals, a much better agreement is reached with rain gauge and ECMWF datasets, the RMS is between 0.80 to 30.24 mm/h for sea surface and 0.789 to 33.11 mm/h for land surface according to the classification by precipitation type. Also, the analysis of retrievals located in Tibetan plateau is provided as an example to justify the robustness and performance of retrieving model.
THE SPACE PARTICLE COMPOSITION DETECTOR ABOARD FY-1C SATELLITE AND ANALYSIS OF PARTICLE RADIATION IN SOUTH ATLANTIC ANOMALY
风云一号C星空间粒子成分探测器及SAA区粒子辐射实测分析

LI Bao-Quan,ZHU Guang-Wu WANG Shi-Jin LIANG Jin-Bao WANG Chun-Qin Center for Space Science,Applied Research,Chinese Academy of Sciences,Beijing,China Graduate School,Chinese Academy of Sciences,Beijing,China,
李保权
,朱光武,王世金,梁金宝,王春琴

地球物理学报 , 2004,
Abstract: The space particle composition detector aboard FY-1C satellite can simultaneously detect proton spectrum, electron integrated flux and heavy ion composition. During the maximum of the 23 rd solar cycle, the high energy particle radiation in the South Atlantic Anomy (SAA) of 860 km altitude had been detected for more than three years by the space particle composition detector. The particle radiation characteristics in the SAA are obtained according to the observed data from space particle composition detector. The effects on particle radiation in the SAA by solar proton events and magnetostorms are analyzed.
Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP  [PDF]
S. Heise,J. Wickert,G. Beyerle,T. Schmidt,C. Reigber
Physics , 2005, DOI: 10.1016/j.asr.2005.06.066
Abstract: The paper deals with application of GPS radio occultation (RO) measurements aboard CHAMP for the retrieval of tropospheric water vapor profiles. The GPS RO technique provides a powerful tool for atmospheric sounding which requires no calibration, is not affected by clouds, aerosols or precipitation, and provides an almost uniform global coverage. We briefly overview data processing and retrieval of vertical refractivity, temperature and water vapor profiles from GPS RO observations. CHAMP RO data are available since 2001 with up to 200 high resolution atmospheric profiles per day. Global validation of CHAMP water vapor profiles with radiosonde data reveals a bias of about 0.2 g/kg and a standard deviation of less than 1 g/kg specific humidity in the lower troposphere. We demonstrate potentials of CHAMP RO retrievals for monitoring the mean tropospheric water vapor distribution on a global scale.
How to average logarithmic retrievals?
B. Funke,T. von Clarmann
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2012,
Abstract: Calculation of mean trace gas contributions from profiles obtained by retrievals of the logarithm of the abundance rather than retrievals of the abundance itself are prone to biases. By means of a system simulator, biases of linear versus logarithmic averaging were evaluated for both maximum likelihood and maximum a priori retrievals, for various signal to noise ratios and atmospheric variabilities. These biases can easily reach ten percent or more. As a rule of thumb we found for maximum likelihood retrievals that linear averaging better represents the true mean value in cases of large local natural variability and high signal to noise ratios, while for small local natural variability logarithmic averaging often is superior. In the case of maximum a posteriori retrievals, the mean is dominated by the a priori information used in the retrievals and the method of averaging is of minor concern. For larger natural variabilities, the appropriateness of the one or the other method of averaging depends on the particular case because the various biasing mechanisms partly compensate in an unpredictable manner. This complication arises mainly because of the fact that in logarithmic retrievals the weight of the prior information depends on abundance of the gas itself. No simple rule was found on which kind of averaging is superior, and instead of suggesting simple recipes we cannot do much more than to create awareness of the traps related with averaging of mixing ratios obtained from logarithmic retrievals.
How to average logarithmic retrievals  [PDF]
B. Funke,T. von Clarmann
Atmospheric Measurement Techniques Discussions , 2011, DOI: 10.5194/amtd-4-7159-2011
Abstract: Calculation of mean trace gas contributions from profiles obtained by retrievals of the logarithm of the abundance rather than retrievals of the abundance itself are prone to biases. By means of a system simulator, biases of linear versus logarithmic averaging were evaluated for both maximum likelihood and maximum a priori retrievals, for various signal to noise ratios and atmospheric variabilities. These biases can easily reach several ten percent. As a rule of thumb we found for maximum likelihood retrievals that linear averaging better represents the true mean value in cases of large local natural variability and high signal to noise ratios, while for small local natural variability logarithmic averaging often is superior. In the case of maximum a posteriori retrievals, the mean is dominated by the a priori information used in the retrievals and the method of averaging is of minor concern. For larger natural variabilities, the appropriateness of the one or the other method of averaging depends on the particular case because the various biasing mechanisms partly compensate in a hardly predictable manner. This complication arises mainly because of the fact that in logarithmic retrievals the weight of the prior information depends on abundance of the gas itself. No simple rule was found on which kind of averaging is superior, and instead of suggesting simple recipes we cannot do much more than to create awareness of the traps related with averaging of mixing ratios obtained from logarithmic retrievals.
Mapping the Dynamics of the Quasar 3C 48  [PDF]
Eleni T. Chatzichristou
Physics , 2000,
Abstract: The archetypical, nearby (z=0.37) quasar 3C 48 is an unusual CSS radio source with excess far-IR emission, whose one-sided radio jet is aligned with the extended ionized emission and a putative second nucleus. Because of its high AGN luminosity and proximity, 3C 48 is a good candidate to search for kinematic signatures of the radio jet-gas coupling and/or of a recent interaction. The radio morphology and our ground-based integral field spectroscopy suggest that the jet is interacting with its immediate environment. Using STIS aboard HST in several slit positions within the central 1", we map the kinematics and physical conditions of the extended emission line gas and their relations to near-nuclear star forming regions found in existing HST images.
FY-3MeteorologicalSatellitesandtheApplications  [PDF]
Tang,Yunqiu,Zhang,Jiashen,Wang,Jingsong
空间科学学报 , 2014, DOI: 10.11728/cjss2014.05.703
Abstract: FY-3isthesecondgenerationpolar-orbitingmeteorologicalsatelliteofChina.ThefirstsatellitenamedFY-3Aofthisserieswaslaunchedon27May2008.ThefirstoperationalsatellitenamedFY-3Cofthisserieswaslaunchedon23September,2013.Thenewgenerationsatellitesaretoprovidethree-dimensional,quantitative,multi-spectralglobalremotesensingdataunderallweatherconditions,whichwillgreatlyhelptheoperationalnumericalweatherprediction,globalclimatechangeresearch,climatediagnosticsandprediction,andnaturaldisastermonitoring.Theywillalsoprovidehelpformanyotherfieldssuchasagriculture,forestry,oceanographyandhydrology.Withtheabovementionedcapability,theFY-3satellitescanmakevaluablecontributionstoimprovingweatherforecasts,globalnatural-disasterandenvironmentalmonitoring.
Evaluating MODIS cloud retrievals with in situ observations from VOCALS-REx
N. J. King, K. N. Bower, J. Crosier,I. Crawford
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2013,
Abstract: Microphysical measurements collected during eleven profiles, by the UK BAe-146 aircraft, through marine stratocumulus as part of the Variability of the American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) are compared to collocated overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua and Terra satellite platforms. The full depth of the cloud is sampled in each case using a Cloud Droplet Probe (CDP) and a Two-Dimensional Stereo Probe (2DS) together sizing cloud and precipitation droplets in the diameter range 2–1260 μm. This allows the total optical depth (τc) of the cloud and effective radius (re) of the droplet size distribution to be compared to MODIS cloud retrievals of the same quantities along with the secondarily derived total liquid water path. When compared to the effective radius at cloud top, the MODIS retrieved re using the 2.1 μm wavelength channel overestimates the in situ measurements on average by 13% with the largest overestimations coinciding with the detection by the 2DS of drizzle sized droplets. We show through consideration of the full vertical profile and penetration depths of the wavelengths used in the retrieval that the expected retrieved values are less than those at cloud top thus increasing the apparent bias in re retrievals particularly when using the 1.6 and 2.1 μm channels, with the 3.7 μm channel retrievals displaying the best agreement with in situ values. Retrievals of τc also tend to overestimate in situ values which, coupled with a high bias in re retrievals, lead to an overestimation of liquid water path. There is little apparent correlation between the variation of the three near-infrared re retrievals and the vertical structure of the cloud observed in situ. Retrievals are performed using measured profiles of water vapour and temperature along with an accurate knowledge of the width of the droplet size distribution which improve agreement between in situ and retrieved values but cannot completely explain the observed biases. Additionally we show that cloud heterogeneity and three-dimensional radiative effects may high skew the mean when averaging over comparison domains but cannot explain all of the apparent high bias. An intercomparison between in situ measurements from the BAe-146 and C-130 platforms is also presented, highlighting the uncertainties associated with in situ observations.
Evidence for Gamma-Ray Flares in 3C 279 and PKS 1622-297 at ~10 MeV  [PDF]
W. Collmar,V. Schoenfelder,H. Bloemen,J. J. Blom,W. Hermsen,M. McConnell,J. G. Stacy,K. Bennett,O. R. Williams
Physics , 1997, DOI: 10.1063/1.54054
Abstract: The EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) has observed at energies above 100 MeV strong gamma-ray flares with short-term time variability from the gamma-ray blazars 3C 279 and PKS 1622-297. During these flaring periods both blazars have been detected by the COMPTEL experiment aboard CGRO at photon energies of about 10 MeV, revealing simultaneous gamma-ray activity down to these energies. For both cases the derived fluxes exceed those measured in previous observations, and 3C 279 shows an indication for time variability within the observational period. Both sources show evidence for `hard' MeV spectra. In general the behaviour of both sources at gamma-ray energies is found to be quite similar supporting the conclusion that the underlying physical mechanism for both gamma-ray flares might be the same.
Influence of scintillation on GOMOS ozone retrievals  [PDF]
V. F. Sofieva,V. Kan,F. Dalaudier,E. Kyr?l?
Atmospheric Chemistry and Physics Discussions , 2009,
Abstract: The stellar light passed through the Earth atmosphere is affected by refractive effects, which should be taken into account in retrievals from stellar occultation measurements. Scintillation caused by air density irregularities is a nuisance for retrievals of atmospheric composition. In this paper, we consider the influence of scintillation on stellar occultation measurements and on quality of ozone retrievals from these measurements, based on experience of the GOMOS (Global Ozone Monitoring by Occultation of Stars) instrument on board the Envisat satellite. In the GOMOS retrievals, the scintillation effect is corrected using scintillation measurements by the fast photometer. We present quantitative estimates of the current scintillation correction quality and of the impact of scintillation on ozone retrievals by GOMOS. The analysis has shown that the present scintillation correction efficiently removes the distortion of transmission spectra caused by anisotropic scintillations. The impact of errors of dilution and anisotropic scintillation correction on quality of ozone retrievals is negligible. However, the current scintillation correction is not able to remove the wavelength-dependent distortion of transmission spectra caused by isotropic scintillations, which can be present in off-orbital-plane occultations. This distortion may result in error of ozone retrievals of 0.5–1.5% at altitudes 20–40 km. This contribution to the error budget is significant for bright stars. The advanced inversion methods that can minimize the influence of scintillation correction error are also discussed.
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