Utilization of Global Climate Models (GCMs) to Study Precipitation Extremes in Pakistan

Global Climate Model (GCM) downscaling projections of climate is important for future impact of climate change. The impact of climate change on the precipitation is studied from literature, modeling, and observations. The rainfall trend in this research was examined across the country using Global Climate Model (GCM) data from period of 1978 to 1999. Downscaling was done on the basis of ascertained relationships between historical observed precipitation records from 36 stations of Pakistan Meteorological Department (PMD). Mann-Kendall test and Taylor Diagrams were used to analyze the data. All of the selected precipitation products were validated at monthly, seasonal and annual time scales utilizing PMD data. The outcomes illustrated that: (1) the precipitation estimates from MIROC, ECHAM and CanESM products correlated well with the referenced PMD observations at monthly time scale. (2) Compared to the MIROC and CanESM, the precipitation estimates from ECHAM were more consistent in all seasons mainly in the winter season with lowest relative bias (2.61%) and highest Correlation Coefficient (0.92); (3) ECHAM showed an apparent dominance over MIROC and CanESM products in order to detain spatial distribution of precipitation over Pakistan. The results exposed a declining trend (-1.18 mm/decade) over southern part of the country, while northern area showed growing trends. The diminishing trend may be featured to the existence of drought period for next few years in various part of country. The results also indicate spatial and temporal change in precipitation.