WISHE-Moisture Mode in an Aquaplanet Simulation

Shi, Xiaoming and Kim, Daehyun and Adames, Angel F and Sukhatme, Jai (2018) WISHE-Moisture Mode in an Aquaplanet Simulation. In: JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, 10 (10). pp. 2393-2407.

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Abstract

This study aims to understand the nature of the tropical intraseasonal oscillations (ISOs) in an aquaplanet simulation performed using Geophysical Fluid Dynamics Laboratory's AM2.1 with a uniform sea surface temperature within the deep tropics. The simulated ISO resembles the observed Madden-Julian Oscillation in that the spectral peak in precipitation appears at zonal wave number 1 and a period of similar to 60days. Vertically integrated moist static energy budget of the simulated ISO shows that enhanced latent heat flux to the east of anomalously active convection causes eastward propagation of the ISO mode, which is weakly opposed by horizontal moisture advection. A series of mechanism denial experiments are conducted either by homogenizing select variablessurface wind stress, longwave radiative heating, and surface evaporationwith their zonal means from the control simulation or by suppressing free-tropospheric moisture variation. Results of the mechanism denial experiments show that the simulated ISO disappears when the interactive surface evaporation is disabled, suggesting that the wind-induced surface heat exchange (WISHE) mechanism is essential to the simulated ISO. Longwave cloud-radiation feedbacks and moisture-convection feedbacks affect horizontal scale and phase speed of the simulated ISO, respectively. Our results strongly suggest that the simulated ISO is the linear WISHE-moisture mode of Fuchs and Raymond under horizontally uniform boundary conditions.

Item Type:	Journal Article
Publication:	JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
Publisher:	AMER GEOPHYSICAL UNION
Additional Information:	Copyright of this article belongs to AMER GEOPHYSICAL UNION
Department/Centre:	Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	23 Dec 2018 06:44
Last Modified:	23 Dec 2018 06:44
URI:	http://eprints.iisc.ac.in/id/eprint/61252

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