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The Madden-Julian Oscillation in an Aquaplanet-Like General Circulation Model With and Without Continents

Das, Surajit and Sengupta, Debasis and Chakraborty, Arindam (2019) The Madden-Julian Oscillation in an Aquaplanet-Like General Circulation Model With and Without Continents. In: JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, 11 (5). pp. 1459-1476.

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Official URL: https://dx.doi.org/10.1029/2018MS001455

Abstract

We have conducted experiments with the Community Atmospheric Model version 5.1 configured as an aquaplanet, with the sun at March equinox, in order to study how the model Madden-Julian oscillation (MJO) responds to (i) the introduction of continents and (ii) realistic sea surface temperature (SST) distribution. Model results are compared with ERA-Interim reanalysis and analyzed in terms of the moist static energy (MSE) budget to study the growth and propagation of MJO. With idealized zonally symmetric SST, the aquaplanet model produces a double Intertropical Convergence Zone (ITCZ) and an MJO-like mode with variance at intraseasonal (30- to 96-day) periods and zonal wave number 1. When we introduce continents with realistic orography and interactive surface temperature, soil moisture, and albedo, the variance of MJO is mainly confined to zonal wave numbers 1 and 2 but reduced by a factor of 3 due to weaker boundary layer moisture convergence. With prescribed climatological January SST boundary condition (which includes Indo-west Pacific warm pool) in the presence of continents, model MJO variance is enhanced and distributed across zonal wave numbers 1 to 5, in closer agreement with observation. Thus, the presence of land by itself is not enough, but realistic SST distribution is necessary for improved space-time characteristics of model MJO. Both in simulations and ERA-Interim data, meridional and vertical advection of MSE promotes eastward movement of MJO. In the model experiments, meridional advection of low-level MSE anomaly is most significant in the vicinity of the ITCZ, indicating the importance of processes that determine the location of (single or double) ITCZ.

Item Type: Journal Article
Additional Information: copyright for this article belongs to AMER GEOPHYSICAL UNION
Keywords: Madden Julian oscillation (MJO)); CAM; ITCZ; zonally symmetric SST; moist static energy budgets; aquaplanet with continents
Department/Centre: Division of Mechanical Sciences > Divecha Centre for Climate Change
Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Depositing User: Id for Latest eprints
Date Deposited: 14 Aug 2019 12:07
Last Modified: 14 Aug 2019 12:08
URI: http://eprints.iisc.ac.in/id/eprint/63436

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