Abstract:
Each extreme weather event may not be regarded because of climate change, but the scientists agree on the fact that the unprecedented pace of climate change is, at least, causing the increased frequency of occurrence of extreme weather events during the recent decades. On the other hand, under-developed countries like Pakistan lack in resources to properly monitor such extreme events, where model-based weather data could be considered as a promising alternative. The framework of this study is twofold: assessing if a model-based reanalysis data (ERA5 from European Centre for Medium-Range Weather Forecasts) could be a potential alternative to gauge-based observed data and investigating the performance accuracy of ERA5 in detection of hydrometeorological extremes in Pakistan. During the initial evaluation of ERA5 by using the observed data as a reference, the frequency analysis and accuracy assessment involved various statistical toolkits applied on climatic parameters. The initial evaluation results show ERA5 to be closely following the fluctuation patterns of observed monthly precipitation data while it displayed promising statistical performance regarding precipitation (Bias: 0.09 mm/month, Correlation: 0.76). However, ERA5 could not perform equally well in its statistical and time series performances especially for the peaks of observed temperature data patterns. Evaluation of ERA5 in accurately catching the observed hydrometeorological extremes such as floods and droughts concluded that it performed better over regions with relatively flatter topography (e.g., Gujjar Khan, Peshawar, Mardan and coastal belt etc.) as compared to regions with complex topography (e.g., Balakot, Dir, etc.). Although, ERA5 followed the fluctuation pattern of extreme events, yet it underestimated some extreme events causing floods and remained on the wetter side while matching very low precipitation events causing droughts. The results of this study might help in establishment of a certain statistical reliability on one of the model-based climate products over Pakistan regarding the hydrometeorological extremes.
