Evaluation and Performance of SM2-Satellite Precipitation Product with Reference to Ground-Based Observations, in different cities of Pakistan
Rainfall is the fundamental component to drive globalized hydrological cycle. Satellite-based precipitation having great inherency over land with wider range of applications, but their validation is at risk due to lack of rain gauge observations in different regions of the world. All precipitation product community are used to monitor the substitute data of rainfall in water resources, climatology, hydrology, meteorology, and geography. This research paper calculated the performance of SM2 precipitation product on different region, climate, elevation, and rainfall rate. For investigation, the ten statistical metrics and three categorical statistic have been analyzed at 11 station over 12 years period from 2007 to 2018. The different statistical technique assessed the analysis of precipitation product at different temporal scales (monthly, seasonally, and yearly) to investigate performance score. On the monthly and yearly time scales, product was less reliable with low correlation (0.0057 to 0.67) vary with elevation but best correlation (0.81) and linear regression coefficient (1.02) was calculated at seasonal scale than rest scales. The rainfall captured rate at seasonal scale with (>80%) was more than another scale. The outcome of this product from satellite community is less at monthly scale with significantly under and overestimation and with BIAS (-34.08% to 132.45%) than seasonal and yearly scale. But slightly over and underestimation pattern exist at seasonal scale with BIAS score (5.13% to -19.61%). During winter, research product reduces its systematic bias, NMAE and NRMSE and maintains its potential at also another seasons. The impact of elevation and different rainfall events are also investigated to detect the performance of SM2 satellite. More intense precipitation was captured by SPPs SM2 with high score of POD (> 0.70 to 0.99) vary with respect to more elevation area. The elevation trend increasing gradually from south (near mean sea level) to the northwest (northern areas of Pakistan) that having complex topography with intense rainfall rate. Same interpolated pattern of precipitation were assessed from south to northern areas of Pakistan like elevation using Arc GIS software. The overall evaluated results shows that precipitation product can detect heavy precipitation events easily than less intense events at monthly and yearly scale but reliable to capture at seasonal scale. This SPP is not completely reliable for low precipitation event with high altitude.
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