A dynamical comparison between two recent drought southwest monsoon seasons 2002 and 2009 over India

An attempt has been made to compare dynamically the recent two drought years, viz., 2002 and 2009, from energetics aspects. For that different energy terms, their generation and conversion among different terms have been computed during 1(st) May - 30(th) September for the above two years over a limited region between 65 degrees E & 95 degrees E, 5 degrees N & 35 degrees N. These computations are based on daily NCEP 2.5 degrees a 2.5 degrees data during 1(st) May - 30(th) September of the above two years. The study shows that although for both the years we had drought, the mean monsoon circulation itself was much weaker in 2009 as compared to 2002, in daily, monthly as well as in the seasonal scale. The weaker mean monsoon circulation, in daily scale, has been demonstrated by comparatively longer spells during June-September 2009 with negative value of conversion of zonal available potential energy to zonal kinetic energy [C(A(z), K(z))]. Large negative values of the monthly total as well as seasonal total of [C(A(z), K(z))] indicate weaker mean monsoon circulation in monthly and in the seasonal scale. The study also shows that in both years, the Seasonal total (June-September) of conversion of zonal available potential energy to eddy available potential energy [C(A(z), K(E))] was positive, but in 2009 its order of magnitude was 10(4) J/kg/cm(2)/sec where as in 2002 it was 10(-6) J/kg/cm(2)/sec, indicating that the influence of mid-latitude westerly was much more in 2009, which may have attributed towards weaker mean monsoon circulation in 2009.