选取热带测雨卫星(Tropical Rainfall Measuring Mission,TRMM)微波成像仪(TRMM Microwave Imager,TMI)液态水路径(liquid water path,LWP)轨道像元数据为研究对象,探讨了将瞬时探测以及逐月的像元数据进行格点化(0.1°、0.25°...选取热带测雨卫星(Tropical Rainfall Measuring Mission,TRMM)微波成像仪(TRMM Microwave Imager,TMI)液态水路径(liquid water path,LWP)轨道像元数据为研究对象,探讨了将瞬时探测以及逐月的像元数据进行格点化(0.1°、0.25°、0.5°、1.0°和2.5°五种格点分辨率)时,格点数据的失真情况。对TMI瞬时探测的个例分析结果表明,细分辨率(0.1°、0.25°和0.5°)格点能保留原始像元数据的细节;而随着网格变粗,细节受到较大的平滑。因此对于中尺度到天气尺度的天气系统分析而言,将卫星轨道数据处理到网格尺度不大于0.5°的格点更合适。对逐月LWP像元资料格点化处理的分析表明,细分辨率格点能保留LWP空间分布细节,尽管5种分辨率下LWP的概率密度分布(probability density function,PDF)均相近。因此,对月尺度及以上的气候分析研究而言,格点尺度大小对卫星像元数据格点化的影响不显著。最后利用本实验室计算的TMI/LWP格点数据与欧洲中期数值预报中心再分析资料(European Centre for Medium-range Weather Forecasts Interim reanalysis,ERA-Interim)和NCEP再分析资料(NCEP Climate Forecast System Reanalysis,NCEP CFSR)进行了对比,发现两种再分析资料都高估了LWP;TMI/LWP格点数据与两种再分析资料LWP的多年变化趋势大致相同。展开更多
Using a microwave radiative transfer model, atmospheric sounding profiles, satellite brightness temperatures, and some surface observed measurements under cloud-free conditions, surface emissivities at the frequencies...Using a microwave radiative transfer model, atmospheric sounding profiles, satellite brightness temperatures, and some surface observed measurements under cloud-free conditions, surface emissivities at the frequencies of TRMM/TMI (Tropical Rainfall Measuring Mission Microwave Imager) at Shouxian in HUBEX (Huaihe River Basin Energy and Water Cycle Experiment) are retrieved. Compared to the microwave surface emissivities with changing conditions of the surface, it is found that the microwave emissivities have some sensitive variability with the conditions of the surface, and the variability is reasonable. In the calculation, the surface air temperatures are assumed to equal the surface skin temperatures, and only the emissivity at Shouxian is calculated; the calculation of the emissivities over the region of HUBEX needs more measurements.展开更多
文章利用TRMM(Tropical Rainfall Measuring)卫星TMI(TRMM Microwave Imager)探测反演的云水、雨水和冰水新版改进资料,定量化检验了WRF(Weather Research and Forecasting)模式6种微物理方案(Lin,WSM6,Thompson,Morrison 2-mom,CAM5.1,...文章利用TRMM(Tropical Rainfall Measuring)卫星TMI(TRMM Microwave Imager)探测反演的云水、雨水和冰水新版改进资料,定量化检验了WRF(Weather Research and Forecasting)模式6种微物理方案(Lin,WSM6,Thompson,Morrison 2-mom,CAM5.1,NSSL 2-mom)对江苏近海及周边海域上空云中水凝物的预报能力。19次个例统计检验结果表明,6种微物理方案基本都能预报出水凝物的量级及大致范围,对于云水的预报,除NSSL2-mom方案误差较大外,其余5种方案误差均较小;CAM5.1方案对雨水含量较大时的预报效果较好,但对于雨水含量较小时的预报误差较大;Lin方案对于冰水的预报效果较好,更接近于实况。在此基础上,选用等权集成(EMN)和消除偏差集成(BREM)两种方法开展集成预报试验,结果发现,两种方法均可以减小预报的误差,且消除偏差集成的方法比等权集成的改进效果更好。展开更多
A 6-year dataset of summer monthly mean precipitation derived from Tropical Precipitation Measure-ment Mission (TRMM)-Microwave Imager (TMI) was used to delineate the spatial distribution patterns of precipitation thr...A 6-year dataset of summer monthly mean precipitation derived from Tropical Precipitation Measure-ment Mission (TRMM)-Microwave Imager (TMI) was used to delineate the spatial distribution patterns of precipitation throughout Asian areas, which indicates that there are three rainfall centers located at the northern coast of the Bay of Bengal, the South China Sea and the western equatorial Pacific Warm Pool, respectively. Based upon the analysis of horizontal distribution, the capability of TMI for characterizing terrestrial and maritime precipitation has been evaluated and compared with Global Precipitation Climatology Project (GPCP) dataset. It was found that TMI and GPCP are well consistent with each other, while a few significant differences occur at several regions over land. By investigating rainfall esti-mates over six specific locations in Asia, a systematic underestimation of TMI was demonstrated, which could be explained by the inherent deficiency within TMI terrestrial algorithm relying on scat-tering signal from ice particles in a precipitation system. A further analysis shows that the highly in-homogeneous distribution of rain gauges employed by GPCP contributes a great deal to the significant discrepancy between GPCP and TMI, especially over regions surrounding the Tibetan Plateau where rain gauges are quite scarce.展开更多
Quantitative estimates of liquid water path （LWP） in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship...Quantitative estimates of liquid water path （LWP） in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature （TB） and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager （TMI） onboard the Tropical Rainfall Measuring Mission （TRMM）, together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single,channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover,by using TMI measurements （1Bll）, this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP cl^anges from -1 to 1 g m-2, and its mean value is about 10^-5 g m^-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m^-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner （VIRS） on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h^-1, the LWP increases with increasing rainfall rate.展开更多
文摘选取热带测雨卫星(Tropical Rainfall Measuring Mission,TRMM)微波成像仪(TRMM Microwave Imager,TMI)液态水路径(liquid water path,LWP)轨道像元数据为研究对象,探讨了将瞬时探测以及逐月的像元数据进行格点化(0.1°、0.25°、0.5°、1.0°和2.5°五种格点分辨率)时,格点数据的失真情况。对TMI瞬时探测的个例分析结果表明,细分辨率(0.1°、0.25°和0.5°)格点能保留原始像元数据的细节;而随着网格变粗,细节受到较大的平滑。因此对于中尺度到天气尺度的天气系统分析而言,将卫星轨道数据处理到网格尺度不大于0.5°的格点更合适。对逐月LWP像元资料格点化处理的分析表明,细分辨率格点能保留LWP空间分布细节,尽管5种分辨率下LWP的概率密度分布(probability density function,PDF)均相近。因此,对月尺度及以上的气候分析研究而言,格点尺度大小对卫星像元数据格点化的影响不显著。最后利用本实验室计算的TMI/LWP格点数据与欧洲中期数值预报中心再分析资料(European Centre for Medium-range Weather Forecasts Interim reanalysis,ERA-Interim)和NCEP再分析资料(NCEP Climate Forecast System Reanalysis,NCEP CFSR)进行了对比,发现两种再分析资料都高估了LWP;TMI/LWP格点数据与两种再分析资料LWP的多年变化趋势大致相同。
基金This work was supported by the National Natural Science Foundation of China under Grant Nos. 49794030 and 40105001.
文摘Using a microwave radiative transfer model, atmospheric sounding profiles, satellite brightness temperatures, and some surface observed measurements under cloud-free conditions, surface emissivities at the frequencies of TRMM/TMI (Tropical Rainfall Measuring Mission Microwave Imager) at Shouxian in HUBEX (Huaihe River Basin Energy and Water Cycle Experiment) are retrieved. Compared to the microwave surface emissivities with changing conditions of the surface, it is found that the microwave emissivities have some sensitive variability with the conditions of the surface, and the variability is reasonable. In the calculation, the surface air temperatures are assumed to equal the surface skin temperatures, and only the emissivity at Shouxian is calculated; the calculation of the emissivities over the region of HUBEX needs more measurements.
文摘文章利用TRMM(Tropical Rainfall Measuring)卫星TMI(TRMM Microwave Imager)探测反演的云水、雨水和冰水新版改进资料,定量化检验了WRF(Weather Research and Forecasting)模式6种微物理方案(Lin,WSM6,Thompson,Morrison 2-mom,CAM5.1,NSSL 2-mom)对江苏近海及周边海域上空云中水凝物的预报能力。19次个例统计检验结果表明,6种微物理方案基本都能预报出水凝物的量级及大致范围,对于云水的预报,除NSSL2-mom方案误差较大外,其余5种方案误差均较小;CAM5.1方案对雨水含量较大时的预报效果较好,但对于雨水含量较小时的预报误差较大;Lin方案对于冰水的预报效果较好,更接近于实况。在此基础上,选用等权集成(EMN)和消除偏差集成(BREM)两种方法开展集成预报试验,结果发现,两种方法均可以减小预报的误差,且消除偏差集成的方法比等权集成的改进效果更好。
基金the NKBRDPC (Grant No. 2004CB418304)the State Key Task in the 11th Five-Year Plan (06013140B)+1 种基金the NSFC (Grant Nos. 40175015 and 40375018)NFC grant of the Joint Research Fund for Overseas Chinese Young Scholars (Grant No. 40428006)
文摘A 6-year dataset of summer monthly mean precipitation derived from Tropical Precipitation Measure-ment Mission (TRMM)-Microwave Imager (TMI) was used to delineate the spatial distribution patterns of precipitation throughout Asian areas, which indicates that there are three rainfall centers located at the northern coast of the Bay of Bengal, the South China Sea and the western equatorial Pacific Warm Pool, respectively. Based upon the analysis of horizontal distribution, the capability of TMI for characterizing terrestrial and maritime precipitation has been evaluated and compared with Global Precipitation Climatology Project (GPCP) dataset. It was found that TMI and GPCP are well consistent with each other, while a few significant differences occur at several regions over land. By investigating rainfall esti-mates over six specific locations in Asia, a systematic underestimation of TMI was demonstrated, which could be explained by the inherent deficiency within TMI terrestrial algorithm relying on scat-tering signal from ice particles in a precipitation system. A further analysis shows that the highly in-homogeneous distribution of rain gauges employed by GPCP contributes a great deal to the significant discrepancy between GPCP and TMI, especially over regions surrounding the Tibetan Plateau where rain gauges are quite scarce.
基金the NSFC under Grant Nos.40730950,40675027,and 40605010the Cooperate Project of LAPC,CAS(LAPCKF-2006-19),and AXA/EORC
文摘Quantitative estimates of liquid water path （LWP） in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature （TB） and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager （TMI） onboard the Tropical Rainfall Measuring Mission （TRMM）, together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single,channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover,by using TMI measurements （1Bll）, this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP cl^anges from -1 to 1 g m-2, and its mean value is about 10^-5 g m^-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m^-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner （VIRS） on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h^-1, the LWP increases with increasing rainfall rate.
