Validation of APHRODITE Precipitation Data for Humid and Sub Humid Regions of Pakistan

Ali G, G Rasul, T Mahmood, Q Zaman, S B Cheema


The Asian Precipitation Highly Resolved Observed Data Integration Towards Evaluation of water resources (APHRODITE’s water resources) data developed for Pakistan on a 0.05 degree resolution by Research Institute for Humanity and Nature (RIHN) and the Meteorological Research Institute of Japan Meteorological Agency (MRI/JMA), was analyzed on decadal basis for the humid and sub humid regions of Pakistan. Scatter plots of both the APHRODITE and observed daily precipitation datasets were constructed on decadal basis from 1971 to 2007. The coefficient of correlation (R2) values vary from very poor (e.g. 0.001 for Kotli, 2001–2007) to very good (e.g.0.98 for Astore, 2001–2007) for different stations in various decades. Monthly totals of both the datasets were averaged on decadal bases and scatter plots were again constructed. In this case the correlation coefficient (R2)
results are far better than those determined for daily precipitation datasets. The very poor correlation results in case of daily precipitation datasets for Islamabad and Kotli are more than 98% in case of mean monthly analysis. Biases between the two precipitation datasets were also calculated for every station in the region. This analysis shows that the APHRODITE data underestimates the observed data for most of the stations in those months in which heavy rainfall occurs. This bias reaches up to a maximum of 271mm for Muzaffarabad in the month of July. The
bias is less where the rainfall amount is small. A slight overestimation of APHRODITE precipitation data has also been recorded for some stations. The maximum overestimation of APHRODITE precipitation data (about 40mm) was observed for Islamabad in the month of March for the decade 1971–1980.

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