An Orography-Associated Extreme Rainfall Event during TiMREX: Initiation, Storm Evolution, and Maintenance

Xu, Weixin; Zipser, Ed; Chen, Yi Leng; Liu, Chuntao; Liou, Yeuh−Yeong; Lee, Wen Chau; Jou, Ben Jong‐Dao

doi:10.1175/mwr-d-11-00208.1

Cited by 110 publications

(114 citation statements)

References 52 publications

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“…However, toward lower latitudes such as the subtropics and tropics, the environments may be less conducive to cold pool development (e.g., Tompkins, 2001). Some studies of extreme rainfall events in South China and Taiwan have shown that surface-based cold air produced by previous convection that had dissipated for hours or even in the day before, when impinged by the moist monsoonal flow, in particular the lowlevel jet (LLJ), can act to trigger new convection in succession (e.g., Zhang and Zhang, 2012;Xu et al, 2012;C.-C. Wang et al, 2014a;Luo et al, 2014). Such influences of "cold domes," however, are different from the lifting at gust fronts produced by coexisting, dissipating cells or those that had just dissipated, and the induced MCSs may be less organized if a linear forcing such as a front or low-level convergence zone is absent (e.g., Xu et al, 2012;C.-C. Wang et al, 2014b).…”

Section: Introductionmentioning

confidence: 99%

A numerical study of back-building process in a quasistationary rainband with extreme rainfall over northern Taiwan during 11–12 June 2012

et al. 2016

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Abstract. During 11-12 June 2012, quasistationary linear mesoscale convective systems (MCSs) developed near northern Taiwan and produced extreme rainfall up to 510 mm and severe flooding in Taipei. In the midst of background forcing of low-level convergence, the back-building (BB) process in these MCSs contributed to the extreme rainfall and thus is investigated using a cloud-resolving model in the case study here. Specifically, as the cold pool mechanism is not responsible for the triggering of new BB cells in this subtropical event during the meiyu season, we seek answers to the question why the location about 15-30 km upstream from the old cell is still often more favorable for new cell initiation than other places in the MCS.With a horizontal grid size of 1.5 km, the linear MCS and the BB process in this case are successfully reproduced, and the latter is found to be influenced more by the thermodynamic and less by dynamic effects based on a detailed analysis of convective-scale pressure perturbations. During initiation in a background with convective instability and near-surface convergence, new cells are associated with positive (negative) buoyancy below (above) due to latent heating (adiabatic cooling), which represents a gradual destabilization. At the beginning, the new development is close to the old convection, which provides stronger warming below and additional cooling at mid-levels from evaporation of condensates in the downdraft at the rear flank, thus yielding a more rapid destabilization. This enhanced upward decrease in buoyancy at low levels eventually creates an upward perturbation pressure gradient force to drive further development along with the positive buoyancy itself. After the new cell has gained sufficient strength, the old cell's rear-flank downdraft also acts to separate the new cell to about 20 km upstream. Therefore, the advantages of the location in the BB process can be explained even without the lifting at the leading edge of the cold outflow.

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Section: Introductionmentioning

confidence: 99%

A numerical study of back-building process in a quasistationary rainband with extreme rainfall over northern Taiwan during 11–12 June 2012

et al. 2016

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Zhong

Chen

2017

Atmosphere

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Warm Sector Torrential Rains (WSTRs) occurring during the outbreak of the monsoon in May of 2015 in South China were studied using surface automatic weather observational data, sounding, European Centre for Medium-Range Weather Forecasts Reanalysis interim Data (ERA-interim), satellite and radar data, and a four-level nested grid simulation with the finest grid spacing of 1 km using the Weather Research and Forecasting model (WRF). The results show that the extreme precipitation event, which had maximum rainfall amounts of 406.3 mm in 10 h and 542.2 mm in 24 h on 20 May 2015, and was characterized by its rapid development and its highly concentrated and long duration of heavy rainfall, occurred over the trumpet-shaped topography of Haifeng. The simulation results indicated that the South China Sea (SCS) atmospheric moisture transportation (AMT) was crucial in triggering the precipitation of the WSTR over South China. The simulation of the WSTR was conducted by using the total energy-mass flux scheme (TEMF), which provided a reasonable simulation of the circulation and the vertical profile in the Planetary Boundary Layer (PBL) as well as the estimation of the precipitation. The AMT, which extends from the Beibu Gulf and the South China Sea to the coastal areas and provides Shanwei with a considerable amount of moisture in the boundary layer, and the effects within the PBL, which include orographic effects, an extra low-level jet, and a high-energy tongue characterized by a high-potential pseudo-equivalent temperature tongue with a warm and moist southwesterly wind, were the important large-scale factors causing the WSTR.

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“…Previous studies have improved our understanding of mechanisms related to orographically induced precipitation systems, examining factors such as low-level convergence, wind blocking (measured by the Froude number, Fr 0U/Nh, where U is the averaged wind speed at altitudes less than that of the maximum terrain height, h is the maximum terrain height and N is the BruntÁVaisala frequency), ambient wind direction and speed, terrain steepness and environmental stability induced by various sizes and shapes of terrains (Smith, 1979;Smolarkeiwicz et al, 1988;Smolarkeiwicz and Rotunno, 1989;Li et al, 1997;Olafsson, 2000;Chiao and Lin, 2003;Jiang, 2003;Petersen et al, 2003;Reeves and Lin, 2007;Houze, 2012;Xu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In a moist environment, a previously generated precipitation system approaching a mountainous region is significantly enhanced in the vicinity of the terrain due to flow modification. Although many studies have examined precipitation systems in mountainous regions, the effects of terrain on pre-existing precipitation systems approaching a terrain with a moist environment are relatively unexplored, and most previous studies have focussed on the Taiwan region (Lin et al, 1992;Jou and Deng, 1998;Chen et al, 2001;Wang et al, 2005;Reeves and Lin, 2007;Xu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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

Lee¹,

Uyeda²,

Lee³

2014

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C T A series of idealised experiments using a cloud-resolving storm simulator (CReSS) was performed to investigate the effects of the isolated elliptically shaped terrain of Jeju Island (oriented eastÁwest), southern Korea, on the enhancement of pre-existing rainfall systems under the influence of prevailing southwesterly moist flows. Control parameters were the low-altitude wind speed (Froude numbers: 0.2, 0.4, 0.55) and the initial location of the elongated (oriented northÁeast) rainfall system (off the northwestern or western shores of the island). Simulations were conducted for all combinations of initial location and wind regime. Overall, results indicate that weak southwesterlies flowing around the steep mountain on the island (height, 2 km) generate two local convergences, on the northern lateral side and on the lee side of the island, both in regions of moist environments, thus producing conditions favourable for enhanced rainfall. As an eastward-moving rainfall system approaches the northwestern shore of the island, the southwesterlies at low altitudes accelerate between the system and the terrain, generating a local updraft region that causes rainfall enhancement onshore in advance of the system's arrival over the terrain. Thus, the prevailing southwesterlies at low altitudes that are parallel to the terrain are a crucial element for the enhancement. Relatively weak southwesterlies at low altitudes allow system enhancement on the lee side by generating a convergence of relatively weak go-around northwesterlies from the northern island and relatively strong moist southwesterlies from the southern island, thus producing a relatively long-lived rainfall system. As the southwesterlies strengthen, a dry descending air mass intensifies on the northeastern downwind side of the terrain, rapidly dissipating rainfall and resulting in a relatively short-lived rainfall system. A coexisting terrain-generated local convergence, combined with the absence of dry descending air on the downwind side of the terrain, prolongs the lifetime of the rainfall system.

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An Orography-Associated Extreme Rainfall Event during TiMREX: Initiation, Storm Evolution, and Maintenance

Cited by 110 publications

References 52 publications

A numerical study of back-building process in a quasistationary rainband with extreme rainfall over northern Taiwan during 11–12 June 2012

A numerical study of back-building process in a quasistationary rainband with extreme rainfall over northern Taiwan during 11–12 June 2012

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

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

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