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The Tropical Subseasonal Variability Simulated in the NASA GISS General Circulation Model
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External Online Source: doi:10.1175/JCLI-D-11-00447.1
Author and Affiliation:
Kim, Daehyun(Columbia Univ., Lamont-Doherty Earth Observatory, Palisades, NY, United States);
Sobel, Adam H.(Columbia Univ., Lamont-Doherty Earth Observatory, Palisades, NY, United States);
DelGenio, Anthony D.(NASA Goddard Inst. for Space Studies, New York, NY, United States);
Chen, Yonghua(Columbia Univ., Dept. of Applied Physics and Applied Mathematics, New York, NY, United States);
Camargo, Suzana J.(Columbia Univ., Lamont-Doherty Earth Observatory, Palisades, NY, United States);
Yao, Mao-Sung(NASA Goddard Inst. for Space Studies, New York, NY, United States);
Kelley, Maxwell(Columbia Univ., Center for Climate Systems Research, New York, NY, United States);
Nazarenko, Larissa(Columbia Univ., Center for Climate Systems Research, New York, NY, United States)
Abstract: The tropical subseasonal variability simulated by the Goddard Institute for Space Studies general circulation model, Model E2, is examined. Several versions of Model E2 were developed with changes to the convective parameterization in order to improve the simulation of the Madden-Julian oscillation (MJO). When the convective scheme is modified to have a greater fractional entrainment rate, Model E2 is able to simulate MJO-like disturbances with proper spatial and temporal scales. Increasing the rate of rain reevaporation has additional positive impacts on the simulated MJO. The improvement in MJO simulation comes at the cost of increased biases in the mean state, consistent in structure and amplitude with those found in other GCMs when tuned to have a stronger MJO. By reinitializing a relatively poor-MJO version with restart files from a relatively better-MJO version, a series of 30-day integrations is constructed to examine the impacts of the parameterization changes on the organization of tropical convection. The poor-MJO version with smaller entrainment rate has a tendency to allow convection to be activated over a broader area and to reduce the contrast between dry and wet regimes so that tropical convection becomes less organized. Besides the MJO, the number of tropical-cyclone-like vortices simulated by the model is also affected by changes in the convection scheme. The model simulates a smaller number of such storms globally with a larger entrainment rate, while the number increases significantly with a greater rain reevaporation rate.
Publication Date: Jul 01, 2012
Document ID:
20140001058
(Acquired Mar 08, 2014)
Subject Category: METEOROLOGY AND CLIMATOLOGY
Report/Patent Number: GSFC-E-DAA-TN9005
Document Type: Technical Report
Publication Information: Journal of Climate; Volume 25; Issue 13; 4641-4659
Contract/Grant/Task Num: NNX10AU63A
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 19p; In English; Original contains color illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: ATMOSPHERIC GENERAL CIRCULATION MODELS; TROPICAL STORMS; CONVECTION; TROPICAL REGIONS; RAIN; VORTICES; STORMS; ENTRAINMENT
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