The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)for cloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the great sensitivity of the TMI 85.5 GHz channels to CL...The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)for cloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the great sensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)of nonprecipitating clouds over land can be successfully estimated using the VDISORT model based on the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and the polarization-difference of 85.5 GHz method were applied to the LWP estimates over land regions during the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.The retrieval results show reasonable agreement with the ground-based microwave radiometer measurements.When the surface emissivity or skin temperature is difficult to be made sure,the polarization-difference method shows advantages of providing estimates of LWP especially for low clouds because of its extremely insensitiveness to the surface skin temperature.展开更多
Remote sensing of rainfall parameters—rainfall rate and size distribution—by raindrop-induced laser bcam scintillation is a new kind of precipitation measurement technique. This paper presented the primary field exp...Remote sensing of rainfall parameters—rainfall rate and size distribution—by raindrop-induced laser bcam scintillation is a new kind of precipitation measurement technique. This paper presented the primary field experiment results based on the theory and numerical simulations by Wu and Lü (1984, 1985) and Lü and Wu (1984).Rainfall rate and size distribution were deduced from observations of laser beam scintillation and compared with those of the filter-paper sampling method. Qualitative analysis of the experiment error was also given here. All the work showed that the theory is applicable, and under proper experiment conditions, remote sensing of rainfall parameters by laser scintillation correlation is an advanced and accurate technique.展开更多
Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical para...Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.展开更多
Composite microwave index (CMI) method is used with the satellite SSM/I data to retrieve summer rainfall rate over 96°E-127°E, 17°N-44°N. The results of verification are : the root_of_mean_square e...Composite microwave index (CMI) method is used with the satellite SSM/I data to retrieve summer rainfall rate over 96°E-127°E, 17°N-44°N. The results of verification are : the root_of_mean_square error is 0.9 mm/h in the actual rain rate range from 2 to 2.9 mm/h; 1.6 mm/h in that from 3 to 5 mm/h and the maximum rms error is 4.2 mm/h in that from 5.1 to 50 mm/h. Case study shows the decision tree and CMI method presented in the note are effective to the rainfall recognition and rain rate retrieval over land of East China.展开更多
文摘The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)for cloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the great sensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)of nonprecipitating clouds over land can be successfully estimated using the VDISORT model based on the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and the polarization-difference of 85.5 GHz method were applied to the LWP estimates over land regions during the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.The retrieval results show reasonable agreement with the ground-based microwave radiometer measurements.When the surface emissivity or skin temperature is difficult to be made sure,the polarization-difference method shows advantages of providing estimates of LWP especially for low clouds because of its extremely insensitiveness to the surface skin temperature.
文摘Remote sensing of rainfall parameters—rainfall rate and size distribution—by raindrop-induced laser bcam scintillation is a new kind of precipitation measurement technique. This paper presented the primary field experiment results based on the theory and numerical simulations by Wu and Lü (1984, 1985) and Lü and Wu (1984).Rainfall rate and size distribution were deduced from observations of laser beam scintillation and compared with those of the filter-paper sampling method. Qualitative analysis of the experiment error was also given here. All the work showed that the theory is applicable, and under proper experiment conditions, remote sensing of rainfall parameters by laser scintillation correlation is an advanced and accurate technique.
基金National Key R&D Program of China(2018YFC1506102)。
文摘Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.
文摘Composite microwave index (CMI) method is used with the satellite SSM/I data to retrieve summer rainfall rate over 96°E-127°E, 17°N-44°N. The results of verification are : the root_of_mean_square error is 0.9 mm/h in the actual rain rate range from 2 to 2.9 mm/h; 1.6 mm/h in that from 3 to 5 mm/h and the maximum rms error is 4.2 mm/h in that from 5.1 to 50 mm/h. Case study shows the decision tree and CMI method presented in the note are effective to the rainfall recognition and rain rate retrieval over land of East China.
