Energy Budget of a Cold Surge Process during the Winter Monsoon Period of 2004

Based on 6-hour reanalysis data with 1°×1° resolution from NCEP and station observed data, a cold surge during 28-31 Dec 2004 was analyzed, showing the following results: (1) During this period, the cold surge moved southward, crossed the equator and influenced the weather of the southern hemisphere. The background circulation was favorable for the breakout of the cold surge: A combination of two troughs in the westerly at 200 hPa and a transversal trough that transformed to a normal one at 500 hPa, which categorized this cold surge as a “transversal trough” type. The Mongolia high remained quasi-stationary, and the strong north wind to the east of it was favorable for the cold surge breakout. (2) The kinetic budget shows that the barotropic kinetic genesis (BTG) and baroclinic kinetic genesis (BCG) are the most important terms of the kinetic budget equation. Initially, the BTG term was dominant; later, the influence of the BCG term increased to equal that of the BTG. After 31 Dec, the kinetic genesis and strong wind zone both decreased obviously. (3) The available potential energy (APE) budget indicates a good correlation between the release of APE and the wind at 850 hPa. The release of APE was favorable for the wind increase at low tropospheric levels and influenced mostly the high levels while having only a slight influence on the middle levels of the troposphere.