Radiative Effects on Torrential Rainfall during the Landfall of Typhoon Fitow(2013)

Cloud microphysical and rainfall responses to radiative processes are examined through analysis of cloud-resolving model sensitivity experiments of Typhoon Fitow（2013） during landfall.The budget analysis shows that the increase in the mean rainfall caused by the exclusion of radiative effects of water clouds corresponds to the decrease in accretion of raindrops by cloud ice in the presence of radiative effects of ice clouds,but the rainfall is insensitive to radiative effects of water clouds in the absence of radiative effects of ice clouds.The increases in the mean rainfall resulting from the removal of radiative effects of ice clouds correspond to the enhanced net condensation.The increases（decreases） in maximum rainfall caused by the exclusion of radiative effects of water clouds in the presence（absence） of radiative effects of ice clouds,or the removal of radiative effects of ice clouds in the presence（absence） of radiative effects of water clouds,correspond mainly to the enhancements（reductions） in net condensation.The mean rain rate is a product of rain intensity and fractional rainfall coverage.The radiation-induced difference in the mean rain rate is related to the difference in rain intensity.The radiation-induced difference in the maximum rain rate is associated with the difference in the fractional coverage of maximum rainfall.

Application of Tikhonov regularization method to wind retrieval from scatterometer data Ⅱ: cyclone wind retrieval with consideration of rain

According to the conclusion of the simulation experiments in paper I, the Tikhonov regularization method is applied to cyclone wind retrieval with a rain-effect-considering geophysical model function （called CMF＋Rain）. The CMF＋Rain model which is based on the NASA scatterometer-2 （NSCAT2） GMF is presented to compensate for the effects of rain on cyclone wind retrieval. With the multiple solution scheme （MSS）, the noise of wind retrieval is effectively suppressed, but the influence of the background increases. It will cause a large wind direction error in ambiguity removal when the background error is large. However, this can be mitigated by the new ambiguity removal method of Tikhonov regularization as proved in the simulation experiments. A case study on an extratropical cyclone of hurricane observed with SeaWinds at 25-km resolution shows that the retrieved wind speed for areas with rain is in better agreement with that derived from the best track analysis for the GMF＋Rain model, but the wind direction obtained with the two-dimensional variational （2DVAR） ambiguity removal is incorrect. The new method of Tikhonov regularization effectively improves the performance of wind direction ambiguity removal through choosing appropriate regularization parameters and the retrieved wind speed is almost the same as that obtained from the 2DVAR.

An improved wind speed algorithm for “Jason-1” altimeter under tropical cyclone conditions

Rain effect and lack of in situ validation data are two main causes of tropical cyclone wind retrieval errors. The National Oceanic and Atmospheric Administration＇s Climate Prediction Center Morphing technique （CMORPH） rain rate is introduced to a match-up dataset and then put into a rain correction model to remove rain effects on ＂Jason-1＂ normalized radar cross section （NRCS）; Hurricane Research Division （HRD） wind sPeed, which integrates all available surface weather observations, is used to substitute in situ data for establishing this relationship with ＂Jason-l＂ NRCS. Then, an improved ＂Jason-l＂ wind retrieval algorithm under tropical cyclone conditions is proposed. Seven tropical cyclones from 2003 to 2010 are studied to validate the new algorithm. The experimental results indicate that the standard deviation of this algorithm at C-band and Ku-band is 1.99 and 2.75 m/s respectively, which is better than the existing algorithms. In addition, the C-band algorithm is more suitable for sea surface wind retrieval than Ku-band under tropical cyclone conditions.