Stochastic projection of precipitation and wet and dry spells over Pakistan using IPCC AR5 based AOGCMs

Stochastic projections of precipitation amount, number of wet days and precipitation per wetday from 25 IPCC AR5 based AOGCMs under RCP4.5 and RCP8.5 are carried out in all climate regimes of Pakistan. In arid climate regime, the ensemble average annual precipitation is projected to decrease by about 5.56%, 3.43%, 4.94% during 2011-2030 (T-1), 2046-2065 (T-2), 2080-2099 (T-3), relative to baseline period (T-B) respectively, under RCP4.5, whereas average annual precipitation in semi-arid (humid) climate regime, is projected to increase by about 8.40% and 8.02% (2.12% and 2.61%) during T-2 and T-3, relative to T-B, respectively. Under RCP8.5, the average annual precipitation is projected to decrease in arid climate regime during T-1 and increase in semi-arid and humid climate regimes during T-2 and T-3, relative to T-B. There is a projected increase (decrease) in precipitation during T-2 (T-3) in all climate regimes, relative to T-1. Under RCP4.5 (RCP8.5), precipitation on wetdays in arid climate regime is projected to be 7.84 (7.64), in semi-arid climate regime it is projected to be 10.78 (10.96) and in humid climate regime it is projected to be 13.67 (13.95) mm wetday(-1), during T-1. During T-2, precipitation per wet day in arid climate regime is projected to be 7.86 (7.83), in semi-arid climate regime it is projected to be 11.32 (11.55), and in humid climate regime it is projected to be 14.40 (14.73) mm wetday(-1) under RCP4.5 (RCP8.5). Overall, under both RCPs, the average annual precipitation and number of wetdays in Pakistan are projected to progressively decrease, whereas precipitation per wetday in Pakistan is projected to progressively increase, all relative to T-B.