Abstract
Satellite quantitative precipitation estimation (QPE) can make up for the insufficiency of ground observations for monitoring precipitation. Using an Advanced Geosynchronous Radiation Imager (AGRI) on the FengYun-4A (FY-4A) satellite and rain gauges (RGs) for observations in the summer of 2020. The existing QPE of the FY-4A was evaluated and found to present poor accuracy over the complex topography of Western China. Therefore, to improve the existing QPE, first, cloud classification thresholds for the FY-4A were established with the dynamic clustering method to identify convective clouds. These thresholds consist of the brightness temperatures (TBs) of FY-4A water vapor and infrared channels, and their TB difference. Then, quantitative cloud growth rate correction factors were introduced to improve the QPE of the convective-stratiform technique. This was achieved using TB hourly variation rates of long-wave infrared channel 12, which is able to characterize the evolution of clouds. Finally, the dynamic time integration method was designed to solve the inconsistent time matching between the FY-4A and RGs. Consequently, the QPE accuracy of the FY-4A was improved. Compared with the existing QPE of the FY-4A, the correlation coefficient between the improved QPE of the FY-4A and the RG hourly precipitation increased from 0.208 to 0.492, with the mean relative error and root mean squared error decreasing from −47.4% and 13.78 mm to 8.3% and 10.04 mm, respectively. However, the correlation coefficient is not sufficiently high; thus, the algorithm needs to be further studied and improved.
Highlights
IntroductionPrecipitation plays an important role in the interaction of the hydrosphere, atmosphere and biosphere [1,2,3,4]; its uneven spatial and temporal distribution often lead to extreme weather events such as rainstorms and drought, which have a serious impact on human activities [5,6,7]
To validate the real-time quantitative precipitation estimation (QPE) of the FY-4A Advanced Geosynchronous Radiation Imager (AGRI) provided by NSMC, Figure 2 presents the comparison between rain gauges (RGs) hourly precipitation and NSMC QPE of the FY-4A AGRI from
QPE of the FY-4A is a national product that focuses on the whole national region and lacks specific validation over complex topography
Summary
Precipitation plays an important role in the interaction of the hydrosphere, atmosphere and biosphere [1,2,3,4]; its uneven spatial and temporal distribution often lead to extreme weather events such as rainstorms and drought, which have a serious impact on human activities [5,6,7]. It is vital to obtain accurate and timely spatial-temporal information of precipitation for meteorological study, flash flood monitoring, water resource management, climatological modeling and assessing groundwater storage [8,9,10]. The accurate acquisition of precipitation intensity and accumulated precipitation is conducive to understanding the global water cycle and the energy balance of the Earth system [11]
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