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

Abstract

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.

Microphysical Characteristics of the Coexisting Frontal and Warm‐Sector Heavy Rainfall in South China

“…This event occurred around coastal regions, where continental and maritime influences coexist (Lang et al., 2010). Consistent with previous studies focusing on convections at subtropical regions (e.g., Chang et al., 2015; Rowe et al., 2011, 2012; Xu & Zipser, 2015), results in this study show that different meteorological forcings can lead to the variability in the microphysical structure of different types of convections. Moreover, the low‐level rotation might be an important factor leading to more large raindrops.…”

Are Storm Characteristics the Same When Viewed Using Merged Surface Radars or a Merged Satellite Product?

“…Although storms appear larger in IMERG, MRMS represents the storms as having higher peak intensities (Fig. 4e), which may be caused by the aggregation of rain particles within the storms' cores at lower altitudes leading to the formation of heavier droplets, falling faster, compared to the precipitation at high levels within the cloud (Xu and Zipser 2015). In addition, the higher spatiotemporal resolution of MRMS compared to IMERG also contributes to a better representation of the heavy precipitation rate in the storm cores.…”

Microphysical Characteristics and Types of Precipitation for Different Seasons over North Taiwan

“…In addition, Zhang et al (2017) noticed a distinct RSD in different squall-line stages and different precipitation types. In Southern Taiwan, Xu and Zipser (2015) concluded that heavy rainfall is mostly associated with a quasi-stationary mei-yu front and that upstream low-level jets and unstable upstream conditions constrained with moist neutral storm environments trigger heavy precipitation. Besides, storm initiation and evolution (Xu et al 2012), as well as kinematic structures and microphysical characteristics (Chang et al 2015;Jung et al 2012), were observed by a Doppler radar.…”