Global Hourly 0.5-degree Land Surface Air Temperature Datasets

Global hourly 0.5-degree Surface Air Temperature (SAT) datasets were developed based on four reanalysis products [Modern-Era Retrospective Analysis for Research and Applications (MERRA for 1979-2009), 40-year ECMWF Re-Analysis (ERA-40 for 1958-2001), ECMWF Interim Re-Analysis (ERA-Interim for 1979-2009), and NCEP/NCAR reanalysis for 1948-2009)] and the Climate Research Unit Time Series version 3.10 (CRU TS3.10) for 1948-2009. The three-step adjustments included the spatial downscaling to 0.5-degree grid cells, the temporal interpolation from 6-hourly (in ERA-40 and NCEP/NCAR reanalysis) to hourly using the MERRA hourly SAT climatology for each day (and the linear interpolation from 3-hourly in ERA-Interim to hourly), and the bias correction in both monthly-mean maximum (Tmax) and minimum (Tmin) SAT using the CRU data.

The final products have exactly the same monthly Tmax and Tmin as the CRU data, and perform well in comparison with in-situ hourly measurements over six sites and with a regional daily SAT dataset over Europe. They agree with each other much better than the original reanalyses, and the spurious SAT jumps of reanalyses over some regions are also substantially eliminated. One of the uncertainties in the final products can be quantified by the differences in the true monthly mean (using 24-hourly values) and the monthly averaged diurnal cycle from different final products.

全球每小时0.5度地表空气温度（SAT）数据集基于四种再分析产品（现代时代研究与应用回顾分析[MERRA for 1979-2009]、40年ECMWF再分析[ERA-40 for 1958-2001]、ECMWF临时再分析[ERA-Interim for 1979-2009]和NCEP/NCAR再分析[1948-2009]）以及气候研究单位时间序列版本3.10（CRU TS3.10[1948-2009]）构建而成。该数据集的调整过程包括三个步骤：空间降尺度至0.5度网格单元、时间插值从6小时（在ERA-40和NCEP/NCAR再分析中）至每小时，使用MERRA每小时SAT气候学数据为每一天提供数据（以及从3小时至每小时的线性插值），以及利用CRU数据进行月平均最大（Tmax）和最小（Tmin）SAT的偏差校正。最终产品与CRU数据的月平均Tmax和Tmin完全一致，与六个站点上的现场每小时测量值以及欧洲的区域每日SAT数据集相比表现良好。与原始再分析产品相比，它们之间的一致性更高，且某些区域再分析中的虚假SAT跳跃也得到了显著消除。最终产品中的一种不确定性可以通过不同最终产品中真实月平均值（使用24小时值）与月平均日循环值之间的差异进行量化。