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A Diagnostic Study of Heavy Rainfall in Karachi Due to Merging of a Mesoscale Low and a Diffused Tropical Depression during South Asian Summer Monsoon 被引量:8
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作者 Ghulam RASUL Qamar-uz-Zaman CHAUDHRY +3 位作者 赵思雄 曾庆存 齐琳琳 张高英 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2005年第3期375-391,共17页
This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression.... This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression. The former low was located over Pakistan's desert region and the latter depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in the diagnosis. The relationship between the heavy precipitation process and large-scale circulations such as monsoon trough, subtropical high, westerly jet, low level jet and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It was found that: (1) the mesoscale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence on 24 July 2003 over the Indian Rajistan area. (2) On the same day, a low that formed over the Bay of Bengal was transformed into a monsoon depression and moved westward to the mesoscale low which existed over southwest India and the adjoining southeastern parts of Pakistan. (3) Initially, the mesoscale low received moisture supply from both the Bay of Bengal as well as the Arabian Sea, whereas the Bay of Bengal maintained the continuous supply of moisture to the monsoon depression. (4) After the depression crossed central India, the Bay's moisture supply was cut off and the Arabian Sea became the-only source of moisture to both the closely located systems. On 27 July, both of the systems merged together and the merger resulted in a heavy downpour in the Karachi metropolitan and in its surroundings. (5) With the intensification as well as the southeastward extension of the subtropical high and the shift of the monsoon trough axis from southwest-west to northeast-east, the monsoon depression moved southwestward. In this situation, there existed a very favourable condition for a merger of the two systems in the presence of cross-latitude influence. (6) A number of convective cloud clusters were developed and organized in the mesoscale low. Probably, interactions existed among the multi-scale systems. 展开更多
关键词 mesoscale low tropical depression heavy downpour cross-latitude influence
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Mesoscale Vortex Generation and Merging Process: A Case Study Associated with a Post-Landfall Tropical Depression 被引量:7
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作者 喻自凤 梁旭东 +1 位作者 余晖 Johnny C. L. CHAN 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第2期356-370,共15页
An observational analysis of satellite blackbody temperature (TBB) data and radar images suggests that the mesoscale vortex generation and merging process appeared to be essential for a tropical-depression-related h... An observational analysis of satellite blackbody temperature (TBB) data and radar images suggests that the mesoscale vortex generation and merging process appeared to be essential for a tropical-depression-related heavy rain event in Shanghai, China. A numerical simulation reproduced the observed mesoscale vortex generation and merging process and the corresponding rain pattern, and then the model outputs were used to study the related dynamics through diagnosing the potential vorticity (PV) equation. The tropical depression (TD) was found to weaken first at lower levels and then at upper levels due to negative horizontal PV advection and diabatic heating effects. The meso-vortices developed gradually, also from the lower to the upper levels, as a result of positive horizontal PV advection and diabatic heating effects in the downshear left quadrant of the TD. One of these newly-generated vortices, V1, replaced the TD ultimately, while the other two, V2 and V3, merged due to the horizontal PV advection process. Together with the redevelopment of V1, the merging of V2 and V3 triggered the very heavy rain in Shanghai. 展开更多
关键词 mesoscale vortex tropical depression heavy rain potential vorticity
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DIAGNOSTIC ANALYSIS OF A RAINSTORM IN SHANDONG PENINSULA INFLUENCED BY A DISTANT TROPICAL DEPRESSION
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作者 闫淑莲 周淑玲 李宏江 《Journal of Tropical Meteorology》 SCIE 2008年第1期73-76,共4页
Based on the observational data as well as data of satellite, NCEP reanalysis and moist potential vortex, the heavy rainfall event that occurred away from the outer cycle of tropical depression Kaemi (No.0605) on July... Based on the observational data as well as data of satellite, NCEP reanalysis and moist potential vortex, the heavy rainfall event that occurred away from the outer cycle of tropical depression Kaemi (No.0605) on July 27, 2006 in Shandong Peninsula has been analyzed. The results show that there are three severe convective cloud clusters during the heavy rainfall. The uprightness of coupling pattern between upper-layer jet and low jet and a divergence area, which appeared in the right of upper-layer jet, provided favorable environmental conditions for convective cloud clusters. The strong convective weather happens over the prefrontal warm sector and the storm rainfall mainly distributes in the front of a high-energy area. Positive vorticity distribution and transportation of warm advection in low levels provide dynamic and thermal conditions for the rainstorm. The spatial-temporal evolvements of physical variable fields and MPV2 as the horizontal component of moist potential vorticity show that the rain intensity change is determined by upper and low level jets and the area of MPV2>0 occurs at the front of the low jet cores. 展开更多
关键词 RAINSTORM tropical depression trough upper and lower level-jet moist baroclinity moist potential vortexl Introduction
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Mesoscale Diagnosis of a Torrential Rainfall Caused by a Tropical Depression 被引量:2
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作者 余晖 梁旭东 +1 位作者 端义宏 漆梁波 《Acta meteorologica Sinica》 SCIE 2005年第2期226-230,共5页
On August 5, 2001, Shanghai was struck by a torrential rainfall due to thepassage of a tropical depression (TD). The rainfall intensity has been the strongest in recent 50years. In this paper, a set of mesoscale re-an... On August 5, 2001, Shanghai was struck by a torrential rainfall due to thepassage of a tropical depression (TD). The rainfall intensity has been the strongest in recent 50years. In this paper, a set of mesoscale re-analyses data and the planetary boundary layerobservation from a wind profiler are used to understand the possible mechanism of such a heavy rain.Results show that the outburst of a southerly jet in the lower atmosphere triggered the explosivedevelopment of cyclonically vertical vorticity in the region with steep potential temperaturesurfaces in front of the TD; while the cyclonic vorticity increased notably at higher levels due tpthe small atmospheric vertical stability of westerly currents in the vicinity of Shanghai. Thesimultaneous sharp development of cyclonic vorticity at different levels should be the main causefor the torrential rainfall. 展开更多
关键词 tropical depression torrential rainfall moist potential vorticity
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The Multiscale Factors Favorable for a Persistent Heavy Rain Event over Hainan Island in October 2010 被引量:3
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作者 汪汇洁 孙建华 +1 位作者 赵思雄 卫捷 《Journal of Meteorological Research》 SCIE CSCD 2016年第4期496-512,共17页
A case study is presented of the multiscale characteristics that produced the record-breaking persistent heavy rainfall event(PHRE) over Hainan Island,northern South China Sea(SCS),in autumn 2010.The study documen... A case study is presented of the multiscale characteristics that produced the record-breaking persistent heavy rainfall event(PHRE) over Hainan Island,northern South China Sea(SCS),in autumn 2010.The study documents several key weather systems,from planetary scale to mesoscale,that contributed to the extreme rainfall during this event.The main findings of this study are as follows.First,the convectively active phase of the MJO was favorable for the establishment of a cyclonic circulation and the northward expansion of the Intertropical Convergence Zone(ITCZ).The active disturbances in the northward ITCZ helped direct abundant moisture from adjacent oceans towards Hainan Island continuously throughout the event,where it interacted with cold air from the midlatitudes and caused heavy rain.Second,the 8-daylong PHRE can be divided into three processes according to different synoptic systems:peripheral cloud clusters of a tropical depression-type disturbance over the central SCS in process 1;interactions between the abnormally far north ITCZ and the invading cold air in process 2;and the newly formed tropical depression near Hainan Island in process 3.In the relatively stable synoptic background of each process,meso-α and meso-β-scale cloud clusters repeatedly traveled along the same path to Hainan Island.Finally,based on these analyses,a conceptual model is proposed for this type of PHRE in autumn over the northern SCS,which demonstrates the influences of multiscale systems. 展开更多
关键词 persistent heavy rainfall event multiscale Lagrangian moisture tracing tropical depression
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