Influence of tropical easterly jet on upper tropical cirrus: An observational study from CALIPSO, Aura-MLS, and NCEP/NCAR data

Abstract

The role of the redistribution of tropical upper tropospheric humidity in the formation of tropical cirrus is studied using three years (June 2006 to December 2008) of observations with the Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) as well as the Microwave Limb Sounder (MLS) onboard the Aura satellite. The National Centers for Environmental Prediction and Atmospheric Research reanalysis data are also used. Results show that the redistribution of upper tropospheric humidity from a highly convective zone to the Indian peninsular region leads to the formation of the tropical cirrus. Advection of upper layer humidity is caused by the tropical easterly jet (TEJ) associated with the Asian summer monsoon (ASM). Thus the present analysis brings out, for the first time, the role of the TEJ in the redistribution of upper tropospheric humidity and consequently in the formation of tropical cirrus. As little observational evidence exists in support of the generative mechanisms of the cirrus, the present results can be useful in quantifying the formation process of these clouds, which have implications for Earth's radiation budget and improving global climate models.

A comprehensive overview of the climatological composition of the Asian summer monsoon anticyclone based on 10 years of Aura Microwave Limb Sounder measurements

“…Ploeger et al [] likewise noted that simulated CO mixing ratios (from the CLaMS Lagrangian chemistry transport model) extend outside the PV contour they used to define the anticyclone transport barrier; they attributed an example of such a lack of trace gas confinement at the northeastern edge of the anticyclone at 380 K in July to the leakiness of the barrier. Similarly, Dethof et al [] pointed out that moisture from the ASM also spreads westward in the tropical easterly jet, and Das et al [] concluded that advection of upper tropospheric humidity by the tropical easterly jet facilitates formation of cirrus clouds over the Southeast Asian and Indian region during the monsoon season. Leakage of polluted air from the northeastern and southwestern edges of the anticyclone has also been diagnosed from in situ aircraft observations [ Rauthe‐Schöch et al , ; Vogel et al , ].…”

Midlatitude cirrus classification at Rome Tor Vergata through a multichannel Raman–Mie–Rayleigh lidar

“…Within this framework, similar to the studies conducted on tropical cirrus (Fortuin et al, 2007;Sunilkumar et al, 2010;Das et al, 2011), the next planned step will be to characterize in detail the meteorological condition of several cirrus cases with the objective of relating each class to one or more processes controlling cirrus formation and evolution. The RMR lidar configuration will be improved to increase the WV measurement accuracy in the upper troposphere, reducing the statistical error and correcting the wet bias.…”

MST radar observations of short‐period gravity wave during overhead tropical cyclone

“…Strong turbulence is also observed below tropopause. Thus, any gravity waves produced by convection could produce mixing around the tropopause level [Pavelin et al, 2002] and enhance the stratosphere-troposphere exchange (STE) processes [Kumar, 2006;Das, 2009;Das et al, 2011].…”