A Subtropical Oceanic Mesoscale Convective Vortex Observed during SoWMEX/TiMREX

Abstract

This study examines a subtropical oceanic mesoscale convective vortex (MCV) that occurred from 1800 UTC 4 June to 1200 UTC 6 June 2008 during intensive observing period (IOP) 6 of the Southwest Monsoon Experiment (SoWMEX) and the Terrain-influenced Monsoon Rainfall Experiment (TiMREX). A dissipating mesoscale convective system reorganized within a nearly barotropic vorticity strip, which formed as a southwesterly low-level jet developed to the south of subsiding easterly flow over the southern Taiwan Strait. A cyclonic circulation was revealed on the northern edge of the mesoscale rainband with a horizontal scale of 200 km. An inner subvortex, on a scale of 25-30 km with maximum shear vorticity of 3 3 10 23 s 21 , was embedded in the stronger convection. The vortex-relative southerly flow helped create local potential instability favorable for downshear convection enhancement. Strong low-level convergence suggests that stretching occurred within the MCV. Higher u e air, associated with significant potential and conditional instability, and high reflectivity signatures near the vortex center suggest that deep moist convection was responsible for the vortex stretching. Dry rear inflow penetrated into the MCV and suppressed convection in the upshear direction. A mesolow was also roughly observed within the larger vortex. The presence of intense vertical wind shear in the higher troposphere limited the vortex vertical extent to about 6 km.

The Impacts of Atmospheric Moisture Transportation on Warm Sector Torrential Rains over South China

“…Atmosphere 2017, 8,116 10 of 15 reached 70 mm, and the corresponding lifted condensation pressures were 972 and 954 hPa, respectively. Moreover, the dew temperature was very close to the temperature below 500 hPa, and the wind shear was relatively small.…”

“…Atmosphere 2017, 8,116 3 of 15 duration of heavy rainfall with 13 h of hourly rainfall exceeding 20 mm. Figure 2 also shows that the surface temperature increased during the daytime before the occurrence of heavy rainfall and reached 34 °C at 1100 UTC on 19 May at station G1827.…”

“…WSTRs caused by the easterly reflux, especially the strong southwest monsoon burst, are directly influenced by low-level processes in the PBL [3]. WSTRs could be triggered by other mesoscale processes within the PBL caused by the mesoscale convective system (e.g., [4][5][6]) and the mesoscale vortex [7][8][9], as well as orographic effects [10][11][12].…”

“…Atmosphere 2017, 8,116 14 of 16 vertical profile in the PBL, as well as a better estimation of the precipitation, whereas the YSU scheme underestimated the precipitation and the AMT values. (2) The AMT, extending from the Beibu Gulf and the South China Sea to the coastal areas and providing Shanwei with considerable amounts of moisture in the boundary layer, was one of the important large-scale factors causing the WSTR.…”

Effect of an isolated elliptical terrain (Jeju Island) on rainfall enhancement in a moist environment

“…Previous studies have investigated the intensification of pre-existing convective systems on the Central Mountain Range (CMR; width, 120 km; length, 320 km; height, 4 km; extending southwestÁnortheast) of Taiwan (an isolated elliptically shaped terrain), under southwesterly monsoon flows dominant at low altitudes during the rainy season (May to mid-June) (Chen and Yu, 1988;Chen et al, 1991;Jou and Deng, 1992;Akaeda et al, 1995;Chen et al, 2001;Wang et al, 2005;Lai et al, 2011). Wang et al (2005) investigated the enhancement mechanisms of a northÁsouth elongated pre-existing rainfall system approaching the northwestern side of the CMR with low Fr.…”