The Variation of the Intensity, Height, and Size of Precipitation Systems with El Niño–Southern Oscillation in the Tropics and Subtropics

Abstract

A 16-yr (1998–2013) Tropical Rainfall Measuring Mission (TRMM) Precipitation Feature (PF) database is used to examine the impacts of El Niño–Southern Oscillation (ENSO) on the characteristics of precipitation systems in the tropics and subtropics. Noticeable differences in the fractions of deep systems (20-dBZ radar echo tops greater than 10 km) and mesoscale convective systems (MCSs) (an area greater than 2000 km2) between different phases of ENSO are found over specific regions, including the central Pacific (CPACI), the western Maritime Continent (WMC), the eastern Maritime Continent (EMC), Gulf of Mexico (GM), Argentina (ARGEN), and Australia (AUS). The coefficients of determination R2 between the multivariate ENSO index (MEI) and the population fractions of deep convection and MCSs are analyzed seasonally over these regions. The responses from these precipitation systems to ENSO are found to be more pronounced in the winter half-year than in the summer half-year. An increase of rainfall during El Niño periods over the CPACI, GM, and ARGEN is found to be associated with more precipitation events and a higher fraction of intense, deep, and large precipitation systems. AUS has fewer precipitation events and a higher fraction of shallow and small precipitation systems during El Niño conditions. Both EMC and WMC have a higher fraction of MCSs during La Niña than El Niño conditions. The EMC observes a higher fraction of deep convection during La Niña conditions. However, the WMC has a higher fraction of deep convection during El Niño conditions, possibly related to the effect of the Indian Ocean dipole.

Using TRMM Latent Heat as a Source to Estimate Convection Induced Gravity Wave Momentum Flux in the Lower Stratosphere

“…During the 16+ year TRMM era, there are several ENSO cycles that are closely tied to the strength of Walker circulation (Power & Smith, 2007), including strong ENSO cycles in 1998-2011. This provides enough samples to examine the general differences in convection and precipitation between two ENSO phases (e.g., Liu et al, 2019). Using the multi-variational ENSO index (Wolter & Timlin, 2011), we selected three Januarys with the highest positive and the lowest negative index values and repeated the process for February through December as shown in Figure 11.…”

“…Specifically, they have been analyzed in their intensity (Zipser et al., 2006), vertical structure (Houze et al., 2015), latent heat release (Shige et al., 2004; Tao et al., 2006), and variations at different time scales (e.g. Nesbitt & Zipser, 2003; Liu et al., 2019). During 16+ years of operation from December 1997 to September 2014, the TRMM precipitation radar has collected a significant number of observations and derived characteristics of precipitation and convection within 36°S–36°N.…”