The Effect of Environmental Conditions on Tropical Deep Convective Systems Observed from the TRMM Satellite

Abstract

This study uses measurements of radiation and cloud properties taken between January and August 1998 by three Tropical Rainfall Measuring Mission (TRMM) instruments, the Clouds and the Earth's Radiant Energy System (CERES) scanner, the TRMM Microwave Imager (TMI), and the Visible and InfraRed Scanner (VIRS), to evaluate the variations of tropical deep convective systems (DCS) with sea surface temperature (SST) and precipitation.This study finds that DCS precipitation efficiency increases with SST at a rate of ~2%/K.Despite increasing rainfall efficiency, the cloud areal coverage rises with SST at a rate of about 7%/K in the warm tropical seas. There, the boundary layer moisture supply for deep convection and the moisture transported to the upper troposphere for cirrus-anvil cloud formation increase by ~6.3%/K and ~4.0%/K, respectively. The changes in cloud formation efficiency, along with the increased transport of moisture available for cloud formation, likely contribute to the large rate of increasing DCS areal coverage. Although no direct observations are available, the increase of cloud formation efficiency with rising SST is deduced indirectly from measurements of changes in the ratio of DCS ice water path and boundary layer water vapor amount with SST.Besides the cloud areal coverage, DCS cluster effective sizes also increase with precipitation.Furthermore, other cloud properties, such as cloud total water and ice water paths, increase with SST. These changes in DCS properties will produce a negative radiative feedback for the earth's climate system due to strong reflection of shortwave radiation by the DCS. These results significantly differ from some previous hypothesized dehydration scenarios for warmer climates, and have great potential in testing current cloud-system resolving models and convective parameterizations of general circulation models.

Influence of local and remote sea surface temperatures on precipitation as inferred from changes in boundary‐layer moisture convergence and moist thermodynamics over global oceans

“…Consequently, the bin-averaged precipitation decreases for SST >29°C where our simulation data also show more divergent and less convergent bin members. Such a feature was also seen in the Lin et al (2006) study. The sample size for the highest SST bin of the climatological SST simulation was also small.…”

“…Several aspects of relationships between atmospheric circulation and SST have been examined in both atmospheric and oceanic circulation scenarios using simulated data as well as observations (e.g. Yu et al, 1991;Harrison and Craig, 1993;Bony et al, 1997;Lau et al, 1997;Del Genio and Kovari, 2002;Lohmann et al, 2002;Seager et al, 2003;Gushchina et al, 2006;Lin et al, 2006). Specifically, Del Genio and Kovari (2002) examined the relationships between the rain-rate and storm radius and related them to key atmospheric diagnostics and SSTs following a regression technique.…”

“…Specifically, Del Genio and Kovari (2002) examined the relationships between the rain-rate and storm radius and related them to key atmospheric diagnostics and SSTs following a regression technique. Lin et al (2006) analyzed the increase in boundary-layer moisture convergence (BLqC) and precipitation efficiency as a function of local SST for tropical deep-convective systems and thereby demonstrated the need to include the BLqC contributions to the SST-precipitation relationship. Bony et al (1997) illustrated use of SST and vertical velocity binning to differentiate between local and remote SST effects on precipitation in the Tropics, while Lau et al (1997) used the 200 hPa divergence fields for categorizing different convective scenarios.…”

On the role of aerosols, humidity, and vertical wind shear in the transition of shallow-to-deep convection at the Green Ocean Amazon 2014/5 site

“…However, it is still not clear how deep or lower tropospheric VWS affects updraft buoyancy. In addition, aerosols can delay the formation of precipitation size hydrometeors, invigorating strong convection, while suppressing shallower and weaker convection (Rosenfeld et al, 2008;Koren et al, 2008;Lin et al, 2006;Andreae et al, 2004). Low-to-moderate aerosols enhance convective strength and such an influence depends on humidity (Chakraborty et al, 2016).…”

On the role of aerosols, humidity, and vertical wind shear in the transition of shallow to deep convection at the Green Ocean Amazon 2014/5 site

“…invigorating strong convection, while suppressing shallower and weaker convection (Rosenfeld 57 et al, 2008;Koren et al, 2008;Lin et al, 2006;Andreae et al, 2004). Low to moderate aerosols 58 enhance convective strength and such an influence depends on humidity (Chakraborty et al,59 2016).…”