PREDICTION OF SUB-SEASONALITY OF INDIAN MONSOON THROUGH KINETIC ENERGY OF WAVE ZERO

S Bawiskar, M Chipade
2012 Online) An Online International Journal Available at   unpublished
Analysis of sixty (1951-2010) years of daily Kinetic Energy of zonal waves derived from NCEP/NCAR u and v data and daily All India Monsoon Rainfall (AIMR) indicate that temporal variations of Kinetic Energy of wave zero (KE(0)) at 100 hPa have potential to predict the Intra-Seasonal Variations (ISV) of Indian Summer Monsoon one month in advance. The Principal Oscillation Patterns of KE (0) and AIMR are almost identical. The prediction method presented in the study is simple and clear. Observe
more » ... nd clear. Observe the temporal variation of KE (0) from mid-April and predict the variation of AIMR from June. In the present scenario, when none of the models (Statistical/Dynamical) in use in India are able to predict ISV, even the qualitative information like increase/decrease of rainfall during the next fortnight and that too one month in advance, is of immense importance to the farmers and planners and even to operational forecasters. INTRODUCTION Saltzman (1957) derived equations governing the energetics of the large-scale of the atmospheric turbulence in the domain of wave number. Saltzman and Fleisher (1960) studied rate of transfer of kinetic energy between different scales of eddies and showed that the intermediate waves (wave numbers 5-10) were source of kinetic energy to long waves (wave numbers 1-4) and short waves (wave numbers 11-16). Saltzman (1970) summarized the results of several studies of energy interactions in the Fourier domain in extra-tropical regions. Krishnamurti and Kanamitsu (1981) examined upper tropospheric large scale circulation features for two contrasting monsoon years and showed the contrasting behaviour of wave number 3. Murakami (1981) studied the energetics of standing and transient scales and observed that standing waves are source of kinetic energy to transient waves. Awade and Bawiskar (1982) pointed out that drought monsoon activity is associated with large divergence of heat at subtropics and large convergence of heat at extra tropics. Bawiskar et al (1989) computed transport of momentum for contrasting monsoon years over India and showed that small scale disturbances are intense during normal monsoon years. Bawiskar and Singh (1992) examined the upper tropospheric energetics of the standing eddies during four contrasting monsoon years over India and found that wave number 2 is stronger during normal monsoon years as compared drought monsoon years. Bawiskar et al (1995) studied energetics of standing and transient eddies of upper and lower troposphere and pointed out that standing wave number 1 plays a very important role in the dynamics of the monsoon circulation in the lower troposphere. Bawiskar et al (1998) studied intra-seasonal variation of kinetic energy of lower tropospheric zonal waves and showed that wave 1 is dominated by 30-40 day and biweekly oscillations while short waves are dominated by weekly oscillations. Bawiskar et al (2002a) studied the energetics of zonal waves during Onset, Established and Withdrawal phases of monsoon and found that wave 0 over equatorial belt, waves 1 and 2 over tropical belt and waves 3-10 over extra-tropical belt influence the monsoon activity over India on intra-seasonal scale. Most of the above mentioned studies are of diagnostic in nature. Bawiskar et al (2002b) were first to introduce a predictor based on the energetics of zonal waves by considering monthly global grid point data of ECMWF and showed that Northward (Southward) momentum transport by wave number zero in the lower troposphere over the latitudinal belt between 25°S and 5°N in the month of March leads to a
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