The Effect of Eurasian Snow Cover on the Monsoon Rainfall of Pakistan

Abstract The Eurasian winter and spring snow cover anomalies along with spring snowmelt have been considered as the important factors affecting the Indian summer monsoon rainfall in particular and the Asian summer monsoon rainfall in general. No previous study has been found in which the effects of Eurasian snow cover on the monsoon of Pakistan would have been analyzed. In this study authors tried to examine the snow cover effects on summer monsoon rainfall of Pakistan (PSMR). Surprisingly, our findings appear as contrary to the findings of previous studies for Asian summer monsoon rainfall (ASMR) and Indian summer monsoon rainfall (ISMR) and no significant negative correlation is found between these above mentioned parameters and PSMR. Only monsoon rainfall of Punjab (may be due to its homogeneity with Indian monsoon dominated regions and smooth arrival of monsoon system from Bay of Bengal) appears to be negative for both winter snow cover and spring snowmelt and not for spring snow cover. Rainfall of NWFP in summer holds better negative correlation as compared to rest of the provinces only for spring snowmelt. Negative correlation is also found between spring snow cover and spring snowmelt. Summer snow cover shows good positive correlation with PSMR in general and with rainfall of Punjab in particular. As far as El Nino is concerned, area of winter snow cover is found above normal and below normal monsoon rainfall is observed while for La Nina, the areas of winter snow cover and spring snow cover are found below normal resulting into above normal rainfall in monsoon. Two snow cover data sets are obtained from two different sources for verifying the correlation. Spring snowmelt area has been calculated as a difference between snow cover of February and that of May.