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International Conference on

Recent Trends in Environmental Sustainability

ESCON22/CDMP/22
Comparative study of satellite and gauge-based rainfall by using advanced rainfall
correction methods

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Yusra Arif , Muhammad Nabeel Khalid , Muhammad Asif , Sajid Rashid , Saqib Hussain
1 College of Earth and Environmental Sciences, University of the Punjab, Lahore
2 Pakistan Meteorological Department Government of Pakistan
Correspondence: yusraarif08@gmail.com
Abstract
Rainfall data is the primary source for flood forecasting. Ungauged basins or the basin with
limited ground-based observation may need satellite rainfall products to compensate for the
scarcity of ground-based observations. This problem becomes serious in the rugged terrain
areas like River Jhelum catchment. The focus of this research is to evaluate the accuracy of
satellite-based GSMaP_NRT rainfall products with gauge-based rainfall data. The selected
area for this research is Jhelum catchment including 9 rainfall observatories. The methods
applied to evaluate the GSMaP_NRT accuracy include a regression method for comparison of
both datasets, and the correction methods for GSMaP_NRT to correct the rainfall data. The
result of GSMaP_NRT original data (without correction) is not satisfactory. So, there is a need
to apply a correction method to overcome the biases/errors. For this, bias correction methods
GSMaP_IF2 (interface 2) and IF3 (interface 3) have been applied. For calibration, the bias
correction results in IF2 and IF3, value of the weight coefficient with respect to distance of bias
correction methods also changed. The results show that GSMaP product and its bias correction
methods underestimate the precipitation amount at some specific locations and overestimate
where gauge-based rainfall is zero. It is also found that areas with lower elevation (e.g. Kotli,
Mangla and Jhelum) give better results than the highly elevated areas (Balakot, Kakul and
Garhi Dupatta). The results of IF3 are far better than GSMaP original and GSMaP_IF2
correction methods. The highest Correlation Coefficient is 0.90 which shows a strong linear
relationship between ground-based and GSMaP_NRT datasets using IF3. Between the two
correction methods i.e., IF2 and IF3, it is concluded that the IF2 follows the pattern of ground-
based rainfall and IF3 follows the peak but deviates temporally and spatially at some points.
However, in both cases GSMaP_NRT is underestimating and overestimating the precipitation
data, but by using correction methods the estimation of GSMaP_NRT reached nearer to the
ground-based data which is the primary purpose of this research.

Keywords: GSMaP_NRT, Rainfall, satellite, Forecast

Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus

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