The Impact of Orography and Latent Heating on the Location of the Tropical Easterly Jet

TL;DR

This study investigates the relative influence of Tibetan orography and latent heating on the location of the Tropical Easterly Jet using climate model simulations, highlighting the dominant role of latent heating.

Contribution

It demonstrates that latent heating, rather than Tibetan orography, primarily determines the TEJ's position through targeted climate model experiments.

Findings

Latent heating is crucial in determining TEJ location.

Orography has minimal impact on TEJ position.

Accurate precipitation simulation shifts TEJ to observed location.

Abstract

The Tropical Easterly Jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian Summer Monsoon. It is generally assumed that Tibet is an essential ingredient in determining the location of the TEJ. However studies have also suggested the importance of latent heating in determining the jet location. The relative importance of Tibetan orography and latent heating is explored through simulations with a general circulation model. The simulation of TEJ by the Community Atmosphere Model, version 3.1 (CAM-3.1) has been discussed in detail. Although the simulated TEJ replicated many observed features of the jet, the jet maximum was located too far to the west when compared to observation. The precipitation in the control simulation was high to the west of India and this caused the TEJ to shift westwards by approximately the same amount. Orography was found to have minimal impact on the simulated TEJ hence indicating that latent heating is the crucial parameter. The primacy of latent heating in determining the jet location was confirmed by additional simulations where the simulated precipitation was brought closer to observations. This made the TEJ to also shift to the correct position.