Predictability of Indian Monsoon Circulation with High Resolution ECMWF Model in the Perspective of Tropical Forecast During the Tropical Convection Year 2008
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To address some of the issues of project Year of Tropical Convection (YOTC) and the project ATHENA as ongoing international activities, an endeavor has been made for the first time to study the predictability of Indian summer monsoon in the backdrop of tropical predictability using 850 hPa atmospheric circulations with the high resolution (T1279) ECMWF model during the boreal summer of 2008 as one of the focus years of YOTC. The major findings obtained from the statistical forecast have been substantiated by the dynamical prediction in terms of the systematic error energy, its growth rate and the attribution of the dominant nonlinear dynamical processes to error growth. The systematic error energy of T1279 (16 km resolution) ECMWF model are generated in African landmass, India and its adjoining oceanic region, in near equatorial west Pacific and around the Madagascar region where the root mean square errors are observed and the zonal wind anomaly shows poor forecast skill. As far as the inadequate predictability of Indian summer monsoon by T1279 ECMWF model (revealed from the results of project ATHENA) is concerned, the systematic error energy and the error growth over Arabian Sea, in the eastern and western India due to the nonlinear convergence and divergence of error flux along with the erroneous Mascarene high may possibly be the determining factors for not showing any discernable improvement in Indian monsoon during the medium range forecast up to 240 h. This work suggests that the higher resolution of ECMWF model may not necessarily lead to the better forecast of Indian monsoon circulations during 2008 unless a methodology can be devised to isolate the errors due to the nonlinear processes that are inherent within the system.
KeywordsPredictability project YOTC project ATHENA systematic error energy ECMWF model Indian summer monsoon
Authors are grateful to Director IITM for his constant encouragement and for giving permission to execute the program in high power computer deployed in IITM. Thanks are due to YOTC data portal for freely uploading the high resolution analysis-forecast system of ECMWF model. Authors are indebted to Dr. Emilia K. Jin, COLA and the project ATHENA team for giving permission to utilize one of the figures from their presentation. Thanks are also due to Brain Doty, COLA for GrADS software and Dr. J Sanjay, CCCR, IITM for helping us to preprocess the data. Authors are also thankful to Dr. H. S. Chaudhari, SSPM group for helping to find out the e-mail address of Emilia K. Jin. Anonymous reviewers’ comments are also gratefully acknowledged.
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