Stratiform and Convective Precipitation Properties of Tropical Cyclones in the Northwest Pacific

Abstract

The properties of stratiform and the convective precipitation of tropical cyclones (TCs) over the northwest Pacific are examined using the Tropical Rainfall Measuring Mission data for 1998–2013. TCs are classified into inner core (IC), inner rainband (IB), and outer rainband (OB) regions, and the results show that TCs are dominated by stratiform precipitation, which accounts for more than 78% of the total raining area. The highest fraction of the stratiform raining area exists in the IB region and increases as the TC intensity increases (from 80% to 93%). Strong convective signatures generally occur in the IC region, less often in the IB region, and least often in the OB region. Stratiform precipitation in the IC region generally has comparable or even stronger ice scattering signatures and higher 20 dBZ radar echo heights than the convective precipitation in the IB and OB regions. Weak convection decreases significantly as the TC intensity increases, which leads to increased convective intensity. Stratiform (convective) precipitation accounts for 61% (39%) of the total TC volumetric rain and 25% (75%) of the total TC lightning flash, respectively. Moreover, stratiform precipitation's contribution to the total TC volumetric rain and lightning flash increases as the TC intensity increases, which indicates that stronger TCs are favorable for maintaining more stratiform precipitation. The stratiform and convective precipitation properties in different TC regions and intensities cooperatively change with the enhanced ascending branch in the IC region and the radial outflow at the upper levels of the secondary circulation.

Regional Variability of Precipitation in Tropical Cyclones Over the Western North Pacific Revealed by the GPM Dual‐Frequency Precipitation Radar and Microwave Imager

“…This is mainly due to the warm core structure and the existence of a downdraft in the vicinity of the TC eye (Houze, ; Wallace & Hobbs, ). As the radius expands from 20 km to nearly 100 km (recognized as the EW region), valleys in the PCT89 values and peaks in the Z e values (Figures a and d) occur for both convective and stratiform precipitation, consistent with previous studies (Jiang et al, ; Yang, Yuan, et al, ). As the radius increases beyond 100 km, the Z e values generally decrease for stratiform precipitation.…”

“…It is also worth noting that the PCT89 values for convective precipitation are comparable to those for stratiform precipitation between 180 and 300 km. In addition, the stratiform precipitation near the TC center has comparable, or even stronger, ice scattering signatures than the convective precipitation in the outer regions (beyond the radius of 350 km), similar to the results revealed by TRMM observations (Yang, Yuan, et al, ).…”

“…There are 1,493, 4,334, and 7,710 pixels of convective precipitation samples in the EW, IB, and OB regions, respectively, which account for 10.3%, 8.0%, and 12.7% of the total precipitating samples in each TC region. The frequency of convective precipitation is highest in the OB region and lowest in the IB region (Yang, Yuan, et al, ).…”

“…The microphysics of the eyewall (EW) and rainbands in TCs that make landfall have been revealed using disdrometers and polarimetric radars in many studies (Chang et al, ; Didlake & Kumjian, ; Feng & Bell, ; May et al, ; Tokay et al, ; Wang et al, ; Wang et al, ; Wu et al, ). However, TCs spend most of their lifetime over the open ocean, where conventional ground‐based radar observations are scarce (Cecil et al, ; Hence & Houze, , ; Jiang et al, ; Yang et al, ). The precipitation radar, microwave imager, and lightning imaging sensor on board the Tropical Rainfall Measuring Mission (TRMM) satellite are effective for acquiring TC measurements over the open ocean (Cecil et al, ; Hence & Houze, , ; Jiang et al, ; Yang, Yuan, et al, ).…”

“…However, TCs spend most of their lifetime over the open ocean, where conventional ground‐based radar observations are scarce (Cecil et al, ; Hence & Houze, , ; Jiang et al, ; Yang et al, ). The precipitation radar, microwave imager, and lightning imaging sensor on board the Tropical Rainfall Measuring Mission (TRMM) satellite are effective for acquiring TC measurements over the open ocean (Cecil et al, ; Hence & Houze, , ; Jiang et al, ; Yang, Yuan, et al, ). Using these observations, Cecil et al () studied the characteristics of radar reflectivity, the 85‐GHz ice scattering signature, and lightning in three TC regions [the EW, the inner rainband (IB), and the outer rainband (OB)]; they revealed that the weakest convective features mainly occur in the IB region.…”