Title: Sources of errors in the simulation of south Asian summer monsoon in the CMIP5 GCMs

Abstract

Accurate simulation of the South Asian summer monsoon (SAM) is still an unresolved challenge. There has not been a benchmark effort to decipher the origin of undesired yet virtually invariable unsuccessfulness of general circulation models (GCMs) over this region. Our study analyzes a large ensemble of CMIP5 GCMs to show that most of the simulation errors in the precipitation distribution and their driving mechanisms are systematic and of similar nature across the GCMs, with biases in meridional differential heating playing a critical role in determining the timing of monsoon onset over land, the magnitude of seasonal precipitation distribution and the trajectories of monsoon depressions. Furthermore, errors in the pre-monsoon heat low over the lower latitudes and atmospheric latent heating over the slopes of Himalayas and Karakoram Range induce significant errors in the atmospheric circulations and meridional differential heating. Lack of timely precipitation further exacerbates such errors by limiting local moisture recycling and latent heating aloft from convection. Most of the summer monsoon errors and their sources are reproducible in the land–atmosphere configuration of a GCM when it is configured at horizontal grid spacing comparable to the CMIP5 GCMs. And while an increase in resolution overcomes many modeling challenges, coarse resolutionmore » is not necessarily the primary driver in the exhibition of errors over South Asia. Our results highlight the importance of previously less well known pre-monsoon mechanisms that critically influence the strength of SAM in the GCMs and highlight the importance of land–atmosphere interactions in the development and maintenance of SAM.« less

Authors:

Ashfaq, Moetasim  ^[1];

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Rastogi, Deeksha ^[1]; Mei, Rui ^[1]; Touma, Danielle ^[2]; Ruby Leung, L. ^[3]

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Climate Change Science Inst.
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Climate Change Science Inst.; Stanford Univ., CA (United States). Dept. of Earth System Science
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Atmospheric Science and Global Change Div. (ASGC)

Publication Date:

Mon Sep 19 00:00:00 EDT 2016

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE Office of Science (SC); USDOD

OSTI Identifier:

1327572

Alternate Identifier(s):

OSTI ID: 1335868

Grant/Contract Number:  

AC05-00OR22725; 32112413; AC05-76RL01830; 3ERKP777; AC0576RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Climate Dynamics

Additional Journal Information:

Journal Name: Climate Dynamics; Journal ID: ISSN 0930-7575

Publisher:

Springer-Verlag

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Land–atmosphere interactions; South Asian monsoon; CMIP5