In terms of NCEP/NCAR daily reanalysis data and some remote sensing data, effects of diabatic heating on the
short-term position variation of the west Pacific subtropical high (WPSH) during persistent heavy rain event in June
2005 in South China are analyzed based on the complete vertical vorticity equation. The results show that the position
variation of WPSH is associated with the diabatic heating. In comparison with the climatology, there is strong heating on
the north side of WPSH and relatively weak ITCZ convection on the south.. Each of westward extension of WPSH
corresponds to a significantly enhanced heating to the west of WPSH. In mid-troposphere, the vertical variation of
heating on the north (south) of WPSH during 12~24 June, 2005 is basically greater(less) than the climatology, which is
unfavorable for the northward movement of WPSH. In the mid and late of June 2005, the vertical variation of heating
over the eastern coast of the Arabian Sea and the Bay of Bengal (to the west of WPSH) is largely higher than the
climatology, which is in favor of the increase of anti-cyclonic vorticity on the west of WPSH, inducing westward
extension of WPSH. As a result, the heating on the north and south, and to the west of WPSH work together to make
WPSH extend more southward and westward in June 2005, which is in favorable for rainbelts maintaining in South
China.
KEYWORDS: Composites, Data centers, Convection, Remote sensing, Environmental sensing, Atmospheric sensing, Information science, Information technology, Numerical simulations, Data processing
By using the NCEP/NCAR daily reanalysis data, CMAP precipitation data , daily precipitation data of 740 stations
in China and some remote sensing data, features of the short-term position variation of the west Pacific subtropical
high(WPSH) during the torrential rain in Yangtze-Huaihe river valley and its possible cause are analyzed. Results show
that the short-term position variation of WPSH is closely associated with the diabatic heating. During the torrential rain
period, the apparent heating source and apparent moisture sink are exceptionally strong over Yangtze-Huaihe river
valley( on the northwest side of WPSH )and the Bay of Bengal (to the west of WPSH). Based on the complete form of
vertical vorticity tendency equation, it is found that the heating field over Yangtze-Huaihe river valley during the
torrential rain period, which is in favor of the increase of cyclonic vorticity on the north side of WPSH, is unfavorable to
the WPSH moving northward. And the heat source over the Bay of Bengal ,which is in favor of the increase of
anti-cyclonic vorticity on the west of WPSH, may induce the westward extension of WPSH.
Based on NCEP/NCAR daily reanalysis data and precipitation data, the circulation background of the extremely
heavy rain causing severe floods in Huaihe River valley (HHRV) in 2003 and its relationships to the apparent heating
were analyzed. The results showed that the El Nino events with middling intensity during 2002~2003 was the previous
background of this extremely heavy rain. The abnormal apparent heating source (Q1) and vapor sink (Q2) may be
one of the important causes for subtropical high maintaining southward than usual. Compared with summer in 2003, the
positive abnormal (Q1) and (Q2) were located to the HHRV during June 21~July 22. The centers of high value bands of (Q1) and (Q2) were in agreement with those of rainfall. But the negative abnormal (Q1) and (Q2) were situated in South China and most of South China Sea areas. The abnormal heating source over the Bay of Bengal
forced an abnormal anticyclonic circulation over its northwest high level leading to the South Asian High enhancing and
maintaining over the Tibetan Plateau, the south of Yangtze River valley and South China, so HHRV areas just located
the updraft areas which was in the south of the high-level jet, making for heavy rain and severe floods.
Based on NCAR/NCEP daily reanalysis, a study is performed of the circulation background for the South-China
torrential rains leading to flash floods in June 2005 with the possible causes explored. Results show that a weak El Nino
episode in 2004-2005 is the climate background of the flooding. Compared to the situation of the summer 2005, the
apparent heat source
(Q1) and the apparent vapor sink (Q2) are anomalously intense in the rainy period June 17~26 over the study region, with their high-value belts resembling the rainfall distribution and their centers roughly coincident
with the rainfall cores. The anomalous heating source from the eastern coast of the Arabian Sea to the Bay of Bengal
excites a high-level abnormal anticyclone to the northwest, making the south-Asian high intensified and westward of
normal, during which China mainland is under the effect of an anomalous cyclonic circulation that keeps the south-Asian
high from northward displacement, allowing it to stay in the south of the Tibetan plateau - South China, a situation that
South China is situated in the rising area on the south side of upper-air westerly jets, making for the occurrence and
maintenance of the intense rains, resulting in extensive flooding.
Based on the TRMM (Tropical Rainfall Measuring Missio) remote sensing data, the relationship between the daily
precipitation and the SST (Sea Surface Temperature) in the low latitude ocean area were analyzed during the Asia
monsoon season in this paper. By calculated the corresponding and lag correlation coefficient of the precipitation and the
SST in the low latitude ocean area in different domain, the paper discussed the relationship between the daily
precipitation and the SST in these areas during the onset, the middle and the terminative period of Asia monsoon season.
The results shown that the relationship was differently in dissimilitude ocean area and period.
Through analyzing the mesoscale disturbance field of a Meiyu rainstorm, it is found that there are close relations between the development and propagation of inertia-gravitational waves, rain belts and low vortex. The propagating patterns of inertia-gravitational waves are different in the upper and lower levels. In the early period of precipitation, convective instability triggers the inertia-gravitational waves. When there are inertia-gravitational waves propagating southward in the upper and lower levels, it is favorable to form multi-rain belts. In the mid of precipitation, the inertia-gravitational waves in the upper-layer rotate anticlockwise with the lower-layer vortex center, and precipitation strengthens and moves eastward in the meantime. The inertia-gravitational waves propagating northward in the upperlayer may result in the development of the lower-layer vortex and precipitation.
Based on NCEP/NCAR reanalysis data, an investigation has been carried of climatic features of East Asian subtropical summer monsoon trough (sub-trough) and its comparison to South China Sea summer monsoon trough (SCS trough). The results show that the SCS trough is stronger than the sub-trough, whether convergence or convection. The sub-trough extends to higher level and inclines northward with altitude, but the SCS trough is reversed. The SCS trough onsets early and abruptly with the positive relative vorticity appearing suddenly and retreats slowly, but the sub-trough establishes step by step with the positive relative vorticity over Yunnan and Guizhou tableland and Guangxi areas spreading northeastward and withdraws rapidly. It is an obvious indicator that the easterly reverses the westerly during the SCS trough's onset, but the sub-trough establishment is characteristic of the westerly enhancement. The sub-trough has clearly frontal property, but the SCS trough is opposite.
Based on TBB data from GMS of Japan, NCEP/NCAR reanalysis data and precipitation data from CPC Merged Analysis of Precipitation (CMAP), an investigation is carried out of seasonal changes of precipitation and convection over Asian-Australian "land bridge" areas and its possible factors. The results show that the precipitation and convection over Sumatra take on clearly seasonal changes with abundant (less) rainfall in winter (summer). The convection over Sumatra moves northwestward rapidly along "land bridge" in the late-April and the early-May (the 25th pentad) and the rainfall shows similar variations. It is the rapid northwestward shifting of convection that affects directly the subsequent enhancement of the convection over Indo-China Peninsula (ICP) area followed by the rupture of the subtropical high (SH) bands in this region leading to South China Sea (SCS) summer monsoon establishment. The zonal wind at lower troposphere in the equatorial Indian Ocean and the cross equatorial flow in 105°E are the main factors associated with the rapid northwestward shifting of convection along "land bridge".
Using the sea surface temperature (SSTA) and wind anomalies (SSWA) of the tropical Pacific from January 1970 to December 1989,main spatial patterns of tropical Pacific SSTA and SSWA coupling features in the transform course from the warm phase to the cold phase of El Nino-southern oscillation (ENSO) cycles are discussed.
The main conclusions are as follows: 1) air-sea coupling patterns at the mature stage of El Nino (La Nina) are main spatial ones of tropical Pacific SSWA and SSTA coupling; 2) at the mature stage of El Nino, the interaction of the anticgclonic anomaly wind,generated by the forcing of distinct meridional SSTA gradient in the northern Hemisphere tropical central Pacific, with the California cold current and SSTA is mainly responsible for weakening of El Nino; 3) the second sea temperature increase along the south American coast in the decaying course of El Nino results from the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacific forced by anomalous west wind stress; 4) La Nina results from the joint effect of Walker circulation, Ekman drift and negative SSTA in the tropical central-eastern Pacific.
The high quality dataset from the South China Sea (SCS) Monsoon Experiment and 40-year NCEP/NCAR reanalysis data are used to investigate the large scale features and abrupt change in meteorological elements during the onset of the SCS summer monsoon. It is found that the SCS summer monsoon establishment is characterized by the South Asian High migrating swiftly from the eastern side of Philippines to the northern part of Indo-China Peninsula and the enhancement of the Bay of Bengal trough and equatorial westerly over the Indian Ocean associated with the equatorial westerly expanding towards northeastward, and followed by the mid-low latitude interaction and continuous retreat eastward of the western Pacific subtropical high. Numerical results reveal that the Indial Peninsula acts as a critical role for the enhancement of the Bay of Bengal trough with a cyclonic difference circulation excited to the east side of the peninsula through ground sensible heating in such a way that the SCS summer monsoon occurs prior to the Indian summer monsoon.
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