scholarly journals ASIAN SUMMER MONSOON UNDER THE GLOBAL WARMING USING A HIGH-RESOLUTION ATMOSPHERIC GENERAL CIRCULATION MODEL

2006 ◽  
Vol 50 ◽  
pp. 547-552
Author(s):  
Koji DAIRAKU ◽  
Seita EMORI
Keyword(s):  
Global Warming ◽  
High Resolution ◽  
General Circulation Model ◽  
Summer Monsoon ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Asian Summer Monsoon ◽  
Circulation Model ◽  
Atmospheric General Circulation ◽  
Asian Summer

scholarly journals On improving the ability of a high-resolution atmospheric general circulation model for dynamical seasonal prediction of the extreme seasons of the Indian summer monsoon

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 339-360
Author(s):  
D.R. SIKKA ◽  
SATYABANBISHOYI RATNA
Keyword(s):  
Boundary Condition ◽  
High Resolution ◽  
Summer Monsoon ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Monsoon Season ◽  
Circulation Model ◽  
Seasonal Prediction ◽  
Atmospheric General Circulation ◽  
Dynamical Seasonal Prediction

The paper is devoted to examine the ability of a high-resolution National Center for Environmental Prediction (NCEP) T170/L42 Atmospheric General Circulation Model (AGCM), for exploring its utility for long-range dynamical prediction of seasonal Indian summer monsoon rainfall (ISMR) based on 5-members ensemble for the hindcast mode 20-year (1985-2004) period with observed global sea surface temperatures (SSTs) as boundary condition and 6-year (2005-2010) period in the forecast-mode with NCEP Coupled Forecast System (CFS) SSTs as boundary condition. ISMR simulations are examined on five day (pentad) rainfall average basis. It is shown that the model simulated ISMR, based on 5-members ensemble average basis had limited skill in simulating extreme ISMR seasons (drought/excess ISMR). However, if the ensemble averaging is restricted to similar ensemble members either in the overall run of pentad-wise below (B) and above (A) normal rainfall events, as determined by the departure for thethreshold value given by coefficient of variability (CV) for the respective pentads based on IMD observed climatology, or during the season as a whole on the basis of percentage anomaly of ISMR from the seasonal climatology, the foreshadowing of drought/excess monsoon seasons improved considerably. Our strategy of improving dynamical seasonal prediction of ISMR was based on the premise that the intra-seasonal variability (ISV) and intra-annual variability (IAV) are intimately connected and characterized by large scale perturbations westward moving (10-20 day) and northward moving (30-60 day) modes of monsoon ISV during the summer monsoon season. As such the cumulative excess of B events in the simulated season would correspond to drought season and vice-versa. The paper also examines El Niño-Monsoon connections of the simulated ISMR series and they appear to have improved considerably in the proposed methodology. This strategy was particularly found to improve for foreshadowing of droughts. Based on results of the study a strategy is proposed for using the matched signal for simulated ISMR based on excess B over A events and vice-versa for drought or excess ISMR category. The probability distribution for the forecast seasonal ISMR on category basis is also proposed to be based on the relative ratio of similar ensemble members and total ensembles on percentage basis. The paper also discusses that extreme monsoon season are produced by the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) modes in a combined manner and hence stresses to improve prediction of IOD mode in ocean-atmosphere coupled model just as it has happened for the prediction ENSO mode six to nine months in advance.

Global Warming Projection by an Atmospheric Global Model with 20-km Grid

2008 ◽  
Vol 3 (1) ◽  
pp. 4-14 ◽  
Author(s):  
Shoji Kusunoki ◽  
◽  
Jun Yoshimura ◽  
Hiromasa Yoshimura ◽  
Ryo Mizuta ◽  
...  
Keyword(s):  
Global Warming ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
General Circulation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Circulation Model ◽  
Global Climate Models ◽  
Rain Band ◽  
Asian Summer

We projected global warming on the Earth Simulator using a very high horizontal resolution atmospheric global general circulation model with 20-km grids, targeting tropical cyclones (TCs) and the rain band (Baiu) during the East Asian summer monsoon season because these bring typical extreme events and global climate models have not yielded reliable simulations or projections due to insufficient resolutions. Our model reproduces TCs and a Baiu rain band reasonably well under present-day climate conditions. In a warmer climate at the end of this century, the model projects, under A1B scenario of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES), that the annual mean formation frequency of TCs decreases by about 30% globally but increased in the North Atlantic and TCs with largemaximumsurface winds increase. The Baiu rain band activity tends to intensify and last longer until August, suggesting more damages due to heavy rainfalls in a warmer climate. This is a review paper mainly originated from published articles on tropical cyclone by Oouchi et al. (2006) [26] and on the East Asian summer monsoon by Kusunoki et al. (2006) [17].

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