The 2010 Pakistan floods in a future climate

Schrier, G. van der; Rasmijn, L.M.; Barkmeijer, J.; Sterl, A.; Hazeleger, W.


The summer 2010 floods hitting Pakistan were the severest on record. Coinciding with these events was the 2010 heatwave over eastern Europe and Russia, which also ranks among the severest ever recorded in the region. Both events were related to an anomalously widespread and intense quasi-stationary anticyclonic circulation anomaly over western Russia which provided favourable conditions, in combination with monsoonal forcing factors, for the Pakistan precipitation events. Here, a data assimilation technique is used which results in a climate model simulation which has its mean upper atmospheric circulation shifted in the direction of the anomalous anticyclonic circulation of summer 2010. This primes the climate model to reproduce, much more frequently than in a climate simulation without this technique, to simulate the conditions which led to the Pakistan 2010 floodings. These experiments are conducted under both present-day and future climatic conditions. In the present-day climate, the main features of the 2010 Pakistan precipitation events are modeled realistically, although the amplitude of the extreme precipitation is underestimated. The simulated future equivalent of the observed extreme precipitation events shows a stronger precipitation over the Bay of Bengal to Kashmir in northern India and northern Pakistan, and from the Arabian Sea to northern Pakistan. In the model context, these precipitation increases are substantial with 50100% increases in rainfall rates. This implies that the future equivalent of the 2010 Pakistan floodings may have even stronger socio-economic impacts.