Predictability of Indian Monsoon Circulation with High Resolution ECMWF Model in the Perspective of Tropical Forecast Du
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Pure and Applied Geophysics
Predictability of Indian Monsoon Circulation with High Resolution ECMWF Model in the Perspective of Tropical Forecast During the Tropical Convection Year 2008 S. DE1 and A. K. SAHAI1 Abstract—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. Key words: Predictability, project YOTC, project ATHENA, systematic error energy, ECMWF model, Indian summer monsoon.
1. Introduction The objective of numerical weather prediction (NWP) is to forecast the weather from several hours
1 Extended Range Prediction, Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharastra, India. E-mail: [email protected]
to days with the numerical model of atmosphere which is a collection of mathematical equations, representing the atmosphere and its prognostic evolution. But the inadequate initial conditions/analysis as well as the model deficiencies leading to the forecast error inhibit the ability to predict the atmospheric system accurately. With the advent of tremendous growth in the computing facilities and the improvement in the global observing system after the introduction of high power computing systems as well as the satellite and remote sensing technologies, NWP model has acquired a substantial capacity to go into the finer scales and thereby, representing the atmospheric systems having w
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