梅雨雨带北跳过程研究

利用19792007年逐日再分析资料和高分辨率逐日降水资料，通过定义确定了每年梅雨雨带北跳的日期，对梅雨雨带的北跳过程及其可能的物理机制进行了研究。分析结果表明：梅雨雨带北跳日期存在明显的年际变化，本文合成得到的雨带北跳过程与前人的工作相一致。水汽输送的变化和对流层中层的垂直运动是影响梅雨雨带位置分布的关键因素。Omega方程诊断结果表明，在梅雨雨带北跳前期，对流层高层的环流异常导致江淮流域出现异常下沉运动，不利于梅雨雨带的北跳；而涡度方程的诊断结果表明，江淮流域的异常下沉运动导致的非绝热冷却在中国东部的对流层低层引起异常反气旋涡度倾向，有利于副热带高压西伸，从而有利于梅雨雨带的北跳。因此，当对流层高层环流发生变化（主要受纬向涡度平流影响），使得江淮流域的异常下沉运动转变为异常上升运动时，高低层相互配合，造成了梅雨雨带的突然北跳。

中国夏季降水雨型雨带与印度洋海温变化特征分析

根据1979～1998年中国夏季(6～8月)逐月降水资料和同期的印度洋海温资料,分别运用经验正交函数和奇异值分解的方法,分析了我国夏季降水的时空分布及其与同期印度洋海温之间的联系。结果表明,我国夏季逐月降水存在着几种相对典型的空间分布形态;夏季印度洋海温与同期江淮流域降水之间呈正相关,而与我国其他大部地区降水之间呈负相关。

EFFECTS OF LOW-LATITUDE MONSOON SURGE ON THE INCREASE IN DOWNPOUR FROM TROPICAL STORM BILIS

By using the dataset of CMA-STI Tropical Cyclone Optimal Tracks, NCEP/NCAR reanalysis and intensive surface observations, a study is performed of the influences of a low-latitude monsoon surge on the longer persistence and increase in torrential rains from the landing tropical storm Bilis. Results suggest that the southwest monsoon was anomalously active after Bilis came ashore. The westerly winds in Bilis's south side might give rise to the poleward movement of the SW monsoon, thus enlarging the pressure gradient between Bilis and the anticyclonic circulation to the south with the result of greatly intensified SW monsoon, which fueled plentiful water vapor, heat and momentum into the declining Bilis and allowed its long stay over land instead of erosion and disappearance. Before Bilis's landfall, the 2006 East Asian monsoon surge, characterized by the atmospheric ISO, experienced remarkable northward propagation. After landfall, the strong surge and powerful low frequency vapor convergence were just on the south side of Bilis, resulting in sharply increased rainfall. In addition, a broad belt of high-valued vapor fluxes extended from the eastern Arabian Sea via the Bay of Bengal, Indochina Peninsula and the South China Sea into the south of China. The belt was linked with the SW monsoon surge forming a moist tongue stretching from the Bay of Bengal to the south of China, which supplied continuously abundant vapor for Bilis along with the surge propagating poleward.

Evaluation of Latest TMPA and CMORPH Precipitation Products with Independent Rain Gauge Observation Networks over High-latitude and Low-latitude Basins in China

The Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） and National Oceanic and Atmospheric Administration （NOAA） Climate Prediction Center （CPC） morphing technique （CMORPH） are two important multi-satellite precipitation products in TRMM-era and perform important functions in GPM-era. Both TMPA and CMORPH systems simultaneously upgraded their retrieval algorithms and released their latest version of precipitation data in 2013. In this study, the latest TMPA and CMORPH products （i.e., Version-7 real-time TMPA （T-rt） and gauge-adjusted TMPA （T-adj）, and Version- 1.0 real-time CMORPH （C-rt） and Version-l.0 gauge-adjusted CMORPH （C-adj）） are evaluated and intercompared by using independent rain gauge observations for a 12-year （2000--2011） period over two typical basins in China with different geographical and climate conditions. Results indicate that all TMPA and CMORPH products tend to overestimate precipitation for the high-latitude semiarid Laoha River Basin and underestimate it for the low-latitude humid Mishui Basin. Overall, the satellite precipitation products exhibit superior performance over Mishui Basin than that over Laoha River Basin. The C-adj presents the best performance over the high-latitude Laoha River Basin, whereas T-adj showed the best performance over the low-latitude Mishui Basin. The two gauge-adjusted products demonstrate potential in water resource management. However, the accuracy of two real-time satellite precipitation products demonstrates large variability in the two validation basins. The C-rt reaches a similar accuracy level with the gauge-adjusted satellite precipitation products in the high-latitude Laoha River Basin, and T-rt performs well in the low-latitude Mishui Basin. The study also reveals that all satellite precipitation products obviously overestimate light rain amounts and events over Laoha River Basin, whereas they underestimate the amount and events over Mishui Basin. The findings of the precision characteristics associated with the latest TMPA and CMORPH precipitation products at different basins will offer satellite pre- cipitation users an enhanced understanding of the applicability of the latest TMPA and CMORPH for water resource management, hydrologic process simulation, and hydrometeorological disaster prediction in other similar regions in China. The findings will also be useful for IMERG algorithm development and update in GPM-era.

COMPARATIVE ANALYSIS OF THE INTENSITY AND DISTRIBUTION OF HEAVY RAINS IN ZHEJIANG PROVINCE CAUSED BY TYPHOONS HAITANG AND MATSA

Study was carried out on two landfall typhoons Haitang and Matsa, which affected Zhejiang province seriously in 2005. Firstly, the similarity and difference between the two typhoon-induced heavy rains were compared and it was pointed out that both of them brought strong large-scale precipitation and the maximum centers of rainfall were located on the north side of the landfall site. Making landfall on Fujian, Haitang was weaker than Matsa in intensity but surpassed it in rainfall. Then with focus on intensity, moving speed, structure of typhoon, circulation and terrain, the two typhoon-related heavy rains were compared and analyzed. Results show that the asymmetrical distribution of rainfall was closely related to the structure of typhoons themselves, moisture transportation and mesoscale terrain. In contrast to the south side, the north side was hotter and wetter and water vapor was also more abundant. The phenomenon of more rainfall induced by Haitang was in connection with the following reasons. Invading cold air led to rainfall increases, weakened dynamic field and slower movement both benefited precipitation. For the last part, the cold characteristic of air mass over Zhejiang was also a favorable factor for the rain.

RELATIONSHIP BETWEEN WEST PACIFIC SUBTROPICAL HIGH AND ENSO AND ITS INFLUENCE ON RAINFALL DISTRIBUTION OF RAINY SEASON IN FUJIAN

Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino (La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.