Application of Equivalent Black Body Temperature in the Forecast of Tropical Cyclone Intensity

Using equivalent black body temperature （TBB） data retrieved from meteorological satellite GMS-5 during 1996-2002, the correlation between the circular symmetric/asymmetric component of TBB and the intensity of tropical cyclone （TC） at various time lags from 0 to 48 h is analyzed for the Northwest Pacific （0^-50~N, 120%155~E）, excluding landed and near-coast samples. It is found that the total TBB near southeast of the eyewall, the circular symmetric component, and the sum of the amplitudes of tangential wave numbers 1-10 （SA10） of the TBB between the radii of 0.8^o and 1.7^o are significantly and negatively correlated with the TC intensity at various time lags from 0 to 48 h. Especially, the maximum 24-h lag correlation coefficients reach -0.52, -0.58, and -0.625, respectively. A statistical prediction scheme for TC intensity is developed based on climatic persistent, synoptic, and TBB factors by stepwise regression technique. It is found that the variance contribution of the averaged TBB over the ring between 1.0^o and 1.5^o from the TC center ranks the fourth in the equation for 12-h TC intensity prediction, and those of the total TBB near southeast of the eyewall and the difference between maximum and minimum TBB between 1.1^o and 1.5^o rank the third and fifth respectively in the 24-h forecast equation. It is also shown that, with TBB factors, the following predictions are improved compared to the scheme without TBB factors： 48-h prediction for severe tropical storm （STS）, 12-h prediction for TC with a weakening rate greater than 15 m s-1/12 h, 24-h intensity prediction for TC with almost no intensity change, and 48-h prediction for TC intensifying faster than 10 m s^-1/48 h.

The Impact of the Eastward Propagation of Convective Systems over the Tibetan Plateau on the Southwest Vortex Formation in Summer

Based on the temperature of the black body (TBB),station observed and NCEP reanalysis data,the impacts of the eastward propagation of convective cloud systems over the Tibetan Plateau on the southwest vortex (SWV) formation that occurred at 1800 UTC on 29 June 2003 are analyzed by using the Zwack-Okossi (Z-O) equation to diagnose the thermal and dynamic processes.It is found that,in summer,severe convective activities often occur over the Tibetan Plateau due to the abundant supply of moisture.The convective cloud near the east edge of the plateau could move eastward with a shortwave trough in the westerly.The divergent center that is induced by latent heat release,which is associated with severe convective activities,moves out with the convective cloud and contributes to the low level decompression which is favorable for the formation of plateau edge cyclogenesis (PEC).The Z-O equation indicates that,in this case,the latent heat release and convergence are the two most important factors for SWV formation,which amounts to about 42% and 15% of the term TOTAL,respectively.It is implied that the thermal process effect was more important than the dynamic process during SWV formation.

Transition from the Southern Mode of the Mei-yu Front Cloud System to Other Leading Modes

Based on normalized six-hourly black body temperature （TBB） data of three geostationary meteorological satellites,the leading modes of the mei-yu cloud system between 1998 and 2008 were extracted by the Empirical Orthogonal Function （EOF） method,and the transition processes from the first typical leading mode to other leading modes were discussed and compared.The analysis shows that,when the southern mode （EOF1） transforms to the northeastern mode （EOF3）,in the mid-troposphere,a low trough develops and moves southeastward over central and eastern China.The circulation pattern is characterized by two highs and one low in the lower troposphere.A belt of low pressure is sandwiched between the weak high over central and western China and the strong western North Pacific subtropical high （WNPSH）.Cold air moves southward along the northerly flow behind the low,and meets the warm and moist air between the WNPSH and the forepart of the low trough,which leads to continuous convection.At the same time,the central extent of the WNPSH increases while its ridge extends westward.In addition,transitions from the southern mode to the dual centers mode and the tropical-low-influenced mode were found to be atypical,and so no common points could be concluded.Furthermore,the choice of threshold value can affect the number of samples discussed.