Accounting for spatiotemporal errors of gauges: A critical step to evaluate gridded precipitation products

JOURNAL OF HYDROLOGY

卷:559

Article

Tang, Guoqiang^1,2,3  Behrangi, Ali^2,3,4,5  Long, Di¹  Li, Changming¹  Hong, Yang^1,6 

[1] Tsinghua Univ, Dept Hydraul Engn, State Key Lab Hydrosci & Engn, Room A207, Beijing 100084, Peoples R China

[2] Univ Calif Los Angeles, Joint Inst Reg Earth Syst Sci & Engn, Los Angeles, CA USA

[3] Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA USA

[4] Univ Arizona, Dept Hydrol & Atmospher Sci, Tucson, AZ USA

[5] CALTECH, Jet Prop Lab, Pasadena, CA USA

[6] Univ Oklahoma, Dept Civil Engn & Environm Sci, Norman, OK 73019 USA

关键词: Precipitation;    IMERG;    Rain gauge;    Gauge density;    Evaluation;    Error function;   

DOI  :  10.1016/j.jhydrol.2018.02.057

来源: Elsevier

【 摘 要 】

Rain gauge observations are commonly used to evaluate the quality of satellite precipitation products. However, the inherent difference between point-scale gauge measurements and areal satellite precipitation, i.e. a point of space in time accumulation v.s. a snapshot of time in space aggregation, has an important effect on the accuracy and precision of qualitative and quantitative evaluation results. This study aims to quantify the uncertainty caused by various combinations of spatiotemporal scales (0.1 degrees-0.8 degrees and 1-24 h) of gauge network designs in the densely gauged and relatively flat Ganjiang River basin, South China, in order to evaluate the state-of-the-art satellite precipitation, the Integrated Multi satellite Retrievals for Global Precipitation Measurement (IMERG). For comparison with the dense gauge network serving as ground truth, 500 sparse gauge networks are generated through random combinations of gauge numbers at each set of spatiotemporal scales. Results show that all sparse gauge networks persistently underestimate the performance of IMERG according to most metrics. However, the probability of detection is overestimated because hit and miss events are more likely fewer than the reference numbers derived from dense gauge networks. A nonlinear error function of spatiotemporal scales and the number of gauges in each grid pixel is developed to estimate the errors of using gauges to evaluate satellite precipitation. Coefficients of determination of the fitting are above 0.9 for most metrics. The error function can also be used to estimate the required minimum number of gauges in each grid pixel to meet a predefined error level. This study suggests that the actual quality of satellite precipitation products could be better than conventionally evaluated or expected, and hopefully enables non-subject-matter expert researchers to have better understanding of the explicit uncertainties when using point-scale gauge observations to evaluate areal products. (C) 2018 Elsevier B.V. All rights reserved.

【 授权许可】

Free