The Role of Offshore Convergence on Coastal Rainfall during TAMEX IOP 3

Yeh, Hsi-Chyi; Chen, Yi-Leng

doi:10.1175/1520-0493(2002)130<2709:trooco>2.0.co;2

Cited by 43 publications

(39 citation statements)

References 44 publications

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“…Thus, in agreement with the observations, the effects of terrain (blocking) appeared to play a key role to initiate the rainband development, while the front helped provide and channel an enhanced background flow with its approach in the present case. Such a scenario is quite similar to those studied by Yeh and Chen (2002) and . Thus, the frontal forcing, LLJ, terrain effects, and the BB process all work together to lead to the quasi-linear MCS and heavy rainfall in northern Taiwan in the present case.…”

Section: Formation Of the Quasi-linear Mcssupporting

confidence: 83%

“…For the one in northern Taiwan Strait (Fig. 2a), in particular, the low-level convergence (from confluence) associated with the barrier jet can provide the forcing for quasi-linear MCSs near or south of the front (e.g., Yeh and Chen, 2002;Wang et al, 2005). The NCEP analyses every 6 h shows that the 950 hPa front reached northern Taiwan near 00:00 UTC on 12 June (Fig.…”

Section: Synoptic and Storm Environmentmentioning

confidence: 98%

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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: Formation Of the Quasi-linear Mcssupporting

confidence: 83%

Section: Synoptic and Storm Environmentmentioning

confidence: 98%

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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“…Unlike findings from previous studies (Li et al 1997;Yeh and Chen 2002), the drifting of pre-existing convection inland is the precursor for the occurrence of localized heavy rainfall in the northwestern Taiwan coast and the Taipei Basin. As the pre-existing convective areas move toward the northwestern coast and northern Taiwan, they are enhanced by orographic effects as a result of orographic blocking.…”

Section: Orographic Effects As the Low-level Trough Approaches Taiwancontrasting

confidence: 89%

“…15b and c), similar to the TAMEX # IOP 3 case reported by Yeh and Chen (2002). The simulated high reflectivity areas migrate from southeastern China coast and north of Taiwan (Fig.…”

Section: Orographic Effects As the Low-level Trough Approaches Taiwansupporting

confidence: 83%

“…Orographic effects are important for triggering and enhancing convection over Taiwan because of the presence of mountain slopes, including the Central Mountain Range (CMR) and Snow Mountain Range (SMR), which occupy about two-thirds of the landmass of Taiwan (Chen 2000;Lin 2007). In addition to favorable large-scale settings, orographic effects may play an important role for the occurrence of excessive rainfall (Li et al 1997;Chen 2000;Yeh and Chen 2002;Chen et al 2005Chen et al , 2007aChen et al , 2010aChen et al , 2010bChen et al , 2011Wang et al 2005). Although heavy rainfall events over northern Taiwan are not as frequent as in southwestern Taiwan (Chen et al 2007a), some heavy rainfall events in northern Taiwan have produced severe damage because of the dense population (Chen 1994;Chen et al 2007b).…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Heavy Rainfall Event over Northern Taiwan on 3 June 1984

Chen¹,

Chen²,

Chen³

et al. 2013

Terr. Atmos. Ocean. Sci.

Self Cite

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In this study, the mechanisms for the development of a localized heavy rainfall event during the evening of 2 June to the early morning of 3 June 1984 over northern Taiwan are investigated. This event occurred under favorable large-scale conditions including: upper-level divergence; low-level high equivalent potential temperature; low levels of free convection; and subsynoptic-scale ascending motion over the northern Taiwan Strait and northern Taiwan associated with a baroclinic front. In the late night of 2 June, pre-existing rainfall is simulated to the southeast of a trough axis over the southeastern China coast as well as in the frontal zone north of Taiwan. The pre-existing rainfall is enhanced as it moves over the northeastern Taiwan Strait where the prevailing southwesterly winds within the Taiwan Strait converge with the orographically deflected flow with a southerly wind component off the western/northwestern Taiwan coast. As the pre-existing convective rainfall continues to move toward northern Taiwan, it is further enhanced in a localized low-level convergence zone over the northwestern coast where a barrier jet along the coast converges with the northwesterly winds behind the surface front. Furthermore, on the morning of 3 June, focusing of rainfall is simulated where the barrier jet encounters the leading edge of the cold pool caused by rain evaporative cooling. As the convective rainfall areas drift inland, the orographic lifting of the pre-frontal southwesterly flow over the slopes south of the Taipei Basin also plays a role in the simulated enhanced heavy rainfall there.

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Convective intensity, vertical precipitation structures, and microphysics of two contrasting convective regimes during the 2008 TiMREX

Zipser

2015

JGR Atmospheres

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This study investigates the convective/microphysical properties and precipitation structures of seven rainfall events in southwest Taiwan during the 2008 Terrain-influenced Monsoon Rainfall Experiment (TiMREX). TiMREX heavy rainfall events (>50 mm d À1 ) are characterized by upstream low-level jets, unstable upstream conditions, and a nearly moist neutral stratification within the heavy rain region. Three heavy rainfall events (2, 5, and 16 June) have only weak to moderate convection and little lightning; e.g., less than 10% of their rainfall is associated with intense convective cells (maximum 40 dBZ height > 8 km). Polarimetric radar measurements indicate that large precipitation-size ice particles well above the freezing level (5 km) are rare in these events. Their vertical profiles of radar reflectivity (VPRR) decrease rapidly above the 0°C level but increase downward below that level. These VPRRs are believed to be associated with weak updrafts and active warm-rain collision and coalescence processes at low levels with raindrops falling through the updraft. In contrast, the 14 June heavy rainfall event is more intense, is ice-based, and exhibits continental characteristics; e.g., 60% of its rainfall is contributed by active thunderstorms (>10 flashes min À1 ). This and other intense storms (26 May and 13 June) have robust lightning (>500 strikes h À1) and pronounced radar reflectivity in the mixed-phase region, indicating strong updrafts and vigorous ice-based processes. Significant amounts of large graupel/small hail are present in the mixed-phase region of these events. Furthermore, their VPRRs decrease or stay constant downward below the freezing level.

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The Role of Offshore Convergence on Coastal Rainfall during TAMEX IOP 3

Cited by 43 publications

References 44 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

Revisiting the Heavy Rainfall Event over Northern Taiwan on 3 June 1984

Convective intensity, vertical precipitation structures, and microphysics of two contrasting convective regimes during the 2008 TiMREX

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