The impact of latent heating on the location, strength and structure of the Tropical Easterly Jet in the Community Atmosphere Model, version 3.1: Aqua-planet simulations

TL;DR

This study investigates how latent heating influences the position, strength, and structure of the Tropical Easterly Jet in climate models, revealing that off-equatorial heating and rainfall patterns significantly affect jet characteristics.

Contribution

It demonstrates that latent heating, especially off-equatorial rainfall, is crucial for accurately simulating the TEJ's structure and location in climate models.

Findings

Latent heating is the key factor affecting TEJ simulation.

Off-equatorial rainfall causes the westward shift of the TEJ.

Deep tropical heating alone cannot reproduce observed TEJ features.

Abstract

The Tropical Easterly Jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian Summer Monsoon (ASM). The simulation of TEJ by the Community Atmosphere Model, version 3.1 (CAM-3.1) has been discussed in detail. Although the simulated TEJ replicates many observed features of the jet, the jet maximum is located too far to the west when compared to observation. Orography has minimal impact on the simulated TEJ hence indicating that latent heating is the crucial parameter. A series of aqua-planet experiments with increasing complexity was undertaken to understand the reasons for the extreme westward shift of the TEJ. The aqua-planet simulations show that a single heat source in the deep tropics is inadequate to explain the structure of the observed TEJ. Equatorial heating is necessary to impart a baroclinic structure and a realistic meridional structure. Jet zonal wind speeds are directly related to the magnitude of deep tropical heating. The location of peak zonal wind is influenced by off-equatorial heating which is closest to it. Hence the presence of excess rainfall in Saudi Arabia has been shown to be the primary reason for the extreme westward shift of the TEJ maximum.