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Title: South Asian monsoon precipitation in CMIP5: a link between inter-model spread and the representations of tropical convection

Abstract

CMIP5 models exhibit a mean dry bias and a large inter-model spread in simulating Indian monsoon precipitation but the origins of the bias and spread have not been well understood. Using moisture and energy budget analysis that exploits the weak temperature gradients in the tropics, we show that they are linked to the convection simulated over the equatorial Indian Ocean. About half of the 21 models analyzed operate at the steep gradient of the non-linear relationship between the normalized precipitable water and normalized precipitation, where small differences in the former are amplified as large differences in precipitation. These models preferentially produce higher precipitation over the equatorial Indian Ocean, and contribute disproportionately to the inter-model spread and multi-model mean dry bias in monsoon precipitation. Conversely, models on the flat side of the relationship are in better agreement with each other and with observations. Under the RCP8.5 forcing scenario, models on the steep part of the relationship project stronger response to warming and dominate the inter-model spread in the projection. This study identified the normalized precipitable water as a key metric for understanding the behavior of model simulated equatorial and Indian monsoon precipitation.

Authors:
ORCiD logo; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1507355
Report Number(s):
PNNL-SA-122642
Journal ID: ISSN 0930-7575
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Climate Dynamics
Additional Journal Information:
Journal Volume: 52; Journal Issue: 1-2; Journal ID: ISSN 0930-7575
Publisher:
Springer-Verlag
Country of Publication:
United States
Language:
English

Citation Formats

Hagos, Samson, Leung, L. Ruby, Ashfaq, Moetasim, and Balaguru, Karthik. South Asian monsoon precipitation in CMIP5: a link between inter-model spread and the representations of tropical convection. United States: N. p., 2018. Web. doi:10.1007/s00382-018-4177-4.
Hagos, Samson, Leung, L. Ruby, Ashfaq, Moetasim, & Balaguru, Karthik. South Asian monsoon precipitation in CMIP5: a link between inter-model spread and the representations of tropical convection. United States. doi:10.1007/s00382-018-4177-4.
Hagos, Samson, Leung, L. Ruby, Ashfaq, Moetasim, and Balaguru, Karthik. Tue . "South Asian monsoon precipitation in CMIP5: a link between inter-model spread and the representations of tropical convection". United States. doi:10.1007/s00382-018-4177-4.
@article{osti_1507355,
title = {South Asian monsoon precipitation in CMIP5: a link between inter-model spread and the representations of tropical convection},
author = {Hagos, Samson and Leung, L. Ruby and Ashfaq, Moetasim and Balaguru, Karthik},
abstractNote = {CMIP5 models exhibit a mean dry bias and a large inter-model spread in simulating Indian monsoon precipitation but the origins of the bias and spread have not been well understood. Using moisture and energy budget analysis that exploits the weak temperature gradients in the tropics, we show that they are linked to the convection simulated over the equatorial Indian Ocean. About half of the 21 models analyzed operate at the steep gradient of the non-linear relationship between the normalized precipitable water and normalized precipitation, where small differences in the former are amplified as large differences in precipitation. These models preferentially produce higher precipitation over the equatorial Indian Ocean, and contribute disproportionately to the inter-model spread and multi-model mean dry bias in monsoon precipitation. Conversely, models on the flat side of the relationship are in better agreement with each other and with observations. Under the RCP8.5 forcing scenario, models on the steep part of the relationship project stronger response to warming and dominate the inter-model spread in the projection. This study identified the normalized precipitable water as a key metric for understanding the behavior of model simulated equatorial and Indian monsoon precipitation.},
doi = {10.1007/s00382-018-4177-4},
journal = {Climate Dynamics},
issn = {0930-7575},
number = 1-2,
volume = 52,
place = {United States},
year = {2018},
month = {3}
}