Study on snow depth anomaly over Eurasia, Indian rainfall and circulations

Abstract

Based on Historical Soviet Daily Snow Depth (HSDSD-II) data for the period 1941-1995, it is found that winter/spring snow depth anomalies over east Eurasia (70 E-160 E, 35 N-65 N) is positively correlated, while west Eurasia (25 E-70 E, 35 N-65 N) is negatively correlated with subsequent Indian summer monsoon rainfall (ISMR). The correlations become stronger and negative with winter snow depth anomaly over west Eurasia during the recent period of study (1975-1995). Four years of high snow (1966, 1968, 1979 and 1986), and two years of low snow (1961 and 1975), are selected on the basis of standardized winter snow depth anomaly over west Eurasia. The Pentad (Fivedays average) analysis of snow depth during the above contrasting snow years show that high/low snow is associated with late/ early snow disappearance. NCEP/NCAR reanalyzed data are used for the study of some important atmospheric characteristics of seasonal monsoon circulation during high/low snow years, followed by deficient/excess ISMR. The important findings of thi s study are: (1) the anomalous persistence of winter/spring snow delays the spring time continental heating, results in weak thermal low, and weak monsoon westerlies over India, (2) the difference fields of Velocity Potential shows complete phase reversal in the dipole structure from high to low snow years, and (3) the temperature and related circulation fields show that low level jet over east Asia is also considerably influenced by Eurasian snow anomaly. © 2005, Meteorological Society of Japan.