用SSM/I微波遥感图像分析海上台风的螺旋云带

文中介绍了美国国防气象卫星专用微波成像仪 (SSM /I)上各通道的特性 ,分析了大气中各种粒子 (尤其是云滴和降水滴 )对各通道辐射的吸收和散射效应。通过对SSM /I图像上台风单通道剖面、双通道散点图的分析 ,揭示了台风在微波图像上表现形式的内在物理原因。在此基础上 ,设计了一个降水指数 ,方法是 :将 85 .5GHz的吸收段对称拉伸到散射段的延长线上 ,然后求归一化后的 19.35 ,37.0GHz和经拉伸处理的 85 .5GHz图像 3者的平均值。 3个通道合成降水指数克服了 37.0GHz对大雨滴不敏感 ,和 85 .5GHz对中等大小雨滴不敏感的缺点 ,比原始单通道微波图像更清楚地显示了台风的螺旋云带结构     

RETRIEVING OVER-OCEAN PRECIPITABLE WATER FROM THE SSM/I MEASUREMENTS WITH SEVERAL REGRESSION ALGORITHMS

A collocated SSM/I and radiosonde measurement data set provided by the NASDA(Japan)was used to retrieve the total precipitable water(PW)over oceans.The retrieval results obtainedwith several regression algorithms were compared against the radiosonde measurements.It isshown that:(a)the routinely operational algorithm of Alishouse et al.(1990)yields significantunderestimation in high PW regime and overestimation in low PW regime;(b)a cubic correctionby Colton and Poe(1994)is not sufficient and globally improves slightly the retrieval results;and(c)the regression algorithm with the form of brightness temperature(T_b)function In (280-T_b)gives a little largely scattered retrievals in whole PW range but without considerable over-andunderestimates in low and high PW regimes.To improve the estimation of the oceanic precipitablewater from the SSM/I measurements,a composite algorithm with different forms of T_b function inlow.medium and high PW regimes is proposed and tested.     

RETRIEVING OVER-OCEAN PRECIPITABLE WATER FROM THE SSM/I MEASUREMENTS WITH SEVERAL REGRESSION ALGORITHMS*

A collocated SSM/I and radiosonde measurement data set provided by the NASDA(Japan) was used to retrieve the total precipitable water(PW) over oceans.The retrieval results obtained with several regression algorithms were compared against the radiosonde measurements.It is shown that:(a) the routinely operational algorithm of Alishouse et al.(1990) yields significant underestimation in high PW regime and overestimation in low PW regime;(b) a cubic correction by Colton and Poe(1994) is not sufficient and globally improves slightly the retrieval results;and(c) the regression algorithm with the form of brightness temperature(T_b) function In(280-T_b) gives a little largely scattered retrievals in whole PW range but without considerable over-and underestimates in low and high PW regimes.To improve the estimation of the oceanic precipitable water from the SSM/I measurements,a composite algorithm with different forms of T_b function in low.medium and high PW regimes is proposed and tested.     

PREDICTION OF TROPICAL DISTURBANCE DEVELOPMENT OVER THE SOUTH CHINA SEA USING SSM/I DATA

This paper proposes a method for predicting the development of tropical disturbance over the South China Sea(SCS)based on the total latent heat release(TLHR)derived from the Special Sensor Microwave/Imager(SSM/I)satellite observations.A threshold value of daily mean TLHR(3×1014 W)for distinguishing the non-developing and developing tropical disturbances is obtained based on the analysis for 25 developing and 43 non-developing tropical disturbances over the SCS during 2000 to 2005.If the mean TLHR within 500 km of a disturbance on the latest day and its daily mean TLHR during previous life are both greater than 3×1014 W,the disturbance will be a developing one in the future.Otherwise,it is a non-developing one.A real-time testing prediction of tropical cyclogenesis over the SCS was conducted for the years 2007 and 2008 using this threshold value of TLHR.We find that the method is successful in detecting the development of 80%of all tropical disturbances over the SCS in 2007 and 2008.     

洋面水汽的微波SSM/I资料反演试验

结合1987年7月华北一次降水过程,利用SSM/I微波资料反演了渤海湾洋面大气柱水汽含量。反演结果与探空资料以及天气实况的对比分析表明,洋面大气柱水汽总含量的SSM/I微波反演结果与探空观测符合得较好,而且能够较好地反映非阵性降水的空间分布和时间变化。     

ESTIMATION OF CLOUD LIQUID WATER OVER THE HUBEX AREA USING THE TRMM MICROWAVE IMAGER

The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)forcloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the greatsensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)ofnonprecipitating clouds over land can be successfully estimated using the VDISORT model basedon the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and thepolarization-difference of 85.5 GHz method were applied to the LWP estimates over land regionsduring the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.Theretrieval results show reasonable agreement with the ground-based microwave radiometermeasurements.When the surface emissivity or skin temperature is difficult to be made sure,thepolarization-difference method shows advantages of providing estimates of LWP especially for lowclouds because of its extremely insensitiveness to the surface skin temperature.