On the suitability of current atmospheric reanalyses for regional warming studies over China

摘要

Reanalyses are widely used because they add value to routine observations by generating physically or dynamically consistent and spatiotemporally complete atmospheric fields. Existing studies include extensive discussions of the temporal suitability of reanalyses in studies of global change. This study adds to this existing work by investigating the suitability of reanalyses in studies of regional climate change, in which land–atmosphere interactions play a comparatively important role. In this study, surface air temperatures (Tsuba/sub) from 12 current reanalysis products are investigated; in particular, the spatial patterns of trends in Tsuba/sub are examined using homogenized measurements of Tsuba/sub made at ～ 2200 meteorological stations in China from 1979 to 2010. The results show that ～ 80?% of the mean differences in Tsuba/sub between the reanalyses and the in situ observations can be attributed to the differences in elevation between the stations and the model grids. Thus, the Tsuba/sub climatologies display good skill, and these findings rebut previous reports of biases in Tsuba/sub. However, the biases in theTsuba/sub trends in the reanalyses diverge spatially (standard deviation = 0.15–0.30?°C?decadesup?1/sup using 1° × 1° grid cells). The simulated biases in the trends in Tsuba/sub correlate well with those of precipitation frequency, surface incident solar radiation (Rsubs/sub) and atmospheric downward longwave radiation (Lsubd/sub) among the reanalyses (r?=??0.83, 0.80 and 0.77; p?Tsuba/sub over southern China (on the order of ?0.07?°C?decadesup?1/sup) are caused by biases in the trends in Rsubs/sub, Lsubd/sub and precipitation frequency on the order of 0.10, ?0.08 and ?0.06?°C?decadesup?1/sup, respectively. The biases in the trends in Tsuba/sub over northern China (on the order of ?0.12?°C?decadesup?1/sup) result jointly from those in Lsubd/sub and precipitation frequency. Therefore, improving the simulation of precipitation frequency and Rsubs/sub helps to maximize the signal component corresponding to regional climate. In addition, the analysis of Tsuba/sub observations helps represent regional warming in ERA-Interim and JRA-55. Incorporating vegetation dynamics in reanalyses and the use of accurate aerosol information, as in the Modern-Era Retrospective Analysis for Research and Applications, version?2 (MERRA-2), would lead to improvements in the modelling of regional warming. The use of the ensemble technique adopted in the twentieth-century atmospheric model ensemble ERA-20CM significantly narrows the uncertainties associated with regional warming in reanalyses (standard deviation = 0.15?°C?decadesup?1/sup).