Is equatorial Africa getting wetter or drier? Insights from an evaluation of long-term, satellite-based rainfall estimates for western Uganda
Is equatorial Africa getting wetter or drier? Insights from an evaluation of long-term, satellite-based rainfall estimates for western Uganda
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DOI：
10.1002/joc.6023
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发表时间：
2019-06-15
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影响因子：
--
通讯作者：
Hartter, Joel
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作者：
Diem, Jeremy E.;Konecky, Bronwen L.;Hartter, Joel
由于缺乏地面测量的降雨量数据，事实证明很难确定赤道非洲降雨量的长期趋势。现在，多种卫星产品以相对精细的空间分辨率提供1983年至今的每日降雨量估计数，但为了评估降雨量趋势，这些产品必须与地面测量数据一起加以验证。本文件的目的有两个：（a）评估乌干达西部过去几十年四种降雨量产品的准确性;（B）确定该区域年降雨量最近的几十年趋势。这四个产品是：非洲降雨气候学第二版、气候灾害小组用台站监测降雨量、利用人工神经网络-气候数据记录从遥感信息估计降雨量和TAMSAT非洲降雨气候学和时序。使用10个雨量计的大约10年的数据评估了这四种产品的10天、每月和季节降雨总量的偏差和准确性。使用变点分析评估多个时间段内产品的均匀性。四种产品的准确性随着时间尺度的增加而增加，CHIRPS是唯一可以被认为在估计整个区域大部分地区的季节性降雨总量时足够准确的产品。TARCAT倾向于低估总数，ARC 2和PERSIANN通常是最不准确的产品。只有CHIRPS和TARCAT的年降雨量估计值与地面测量的降雨总量显着相关。TARCAT是最均匀的产品，而ARC 2，CHIRPS和PERSIANN具有显著的负变化点，导致1983-2016年期间的干燥偏倚。在根据变化点的时间和幅度调整基于卫星的降雨量估计值后，从所有四个产品得出的年降雨量总和表明，乌干达西部在1983年至2016年期间降雨量显著增加。
Long-term trends in equatorial African rainfall have proven difficult to determine because of a dearth in ground-measured rainfall data. Multiple, satellite-based products now provide daily rainfall estimates from 1983 to the present at relatively fine spatial resolutions, but in order to assess trends in rainfall, they must be validated alongside ground-based measurements. The purpose of this paper is twofold: (a) to assess the accuracy of four rainfall products covering the past several decades in western Uganda; and (b) to ascertain recent, multi-decadal trends in annual rainfall for the region. The four products are African Rainfall Climatology Version 2 (ARC2), Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR), and TAMSAT African Rainfall Climatology And Timeseries (TARCAT). The bias and accuracy of 10-day, monthly, and seasonal rainfall totals of the four products were assessed using approximately 10 years of data from 10 rain gauges. The homogeneity of the products over multiple time periods was assessed using change-point analysis. The accuracy of the four products increased with an increase in temporal scale, and CHIRPS was the only product that could be considered sufficiently accurate at estimating seasonal rainfall totals throughout most of the region. TARCAT tended to underestimate totals, and ARC2 and PERSIANN were in general the least accurate products. Only annual rainfall estimates from CHIRPS and TARCAT were significantly correlated with ground-measured rainfall totals. TARCAT was the most homogeneous product, while ARC2, CHIRPS, and PERSIANN had significant negative change points that caused a drying bias over the 1983-2016 period. After adjusting the satellite-based rainfall estimates based on the timing and magnitude of the change points, annual rainfall totals derived from all four products indicated that western Uganda experienced significantly increasing rainfall from 1983 to 2016.