Intercomparison of CRA-Interim Precipitation Products with ERA5 and JRA-55

Based on the hourly observational data during 2007-2016 from surface meteorological stations in China,this paper compares the influence of 3-hourly precipitation data,mainly from the Chinese Reanalysis-Interim(CRA-Interim),ECMWF Reanalysis 5(ERA5)and Japanese Reanalysis-55(JRA-55),on the simulation of the spatial and temporal distribution of regional precipitation in China and the bias distribution of the simulation.The results show that:(1)The three sets of reanalysis datasets can all reflect the basic spatial distribution characteristics of annual average precipitation in China.The simulation of topographic forced precipitation in complex terrain by using CRA-interim is more detailed,while CRA-interim has larger negative bias in central and East China,and larger positive bias in southwest China.(2)In terms of seasonal precipitation,the three sets of reanalysis datasets overestimate the precipitation in the heavy rainfall zone in spring and summer,especially in southwest China.According to CRA-interim,location of the rain belt in the First Rainy Season in South China is west by south,and the summer precipitation has positive bias in southwest and South China.(3)All of the reanalysis datasets can basically reflect the distribution difference of inter-annual variation of drought and flood,but overall the CRA-Interim generally shows negative bias,while the ERA5 and JRA-55 exhibit positive bias.(4)For the diurnal variation of precipitation in summer,all the reanalysis datasets perform better in simulating the daytime precipitation than in the night,and the bias of CRA-interim is less in the Southeast and Northeast than elsewhere.(5)The ERA5 generally performs the best on the evaluation of quantitative precipitation forecast,the JRA-55 is the next,followed by the CRA-Interim.The CRA-Interim has higher missing rate and lower threat score for heavy rains;however,at the level of downpour,the CRA-Interim performs slightly better.

两种再分析月平均气温资料在蒙古国的适用性评估

利用蒙古国18个气象站1987-2006年实测月平均气温资料与JRA-55和ERA-interim两种再分析资料月平均气温进行了比较和分析。首先对比了两种再分析气温资料在蒙古国校正前后的质量状况,并分析了资料的误差来源;然后将再分析气温资料与实测气温资料变化趋势进行对比,评估其对于温度变化趋势的反映能力。结果表明,利用气温直减率对再分析资料校正可以显著提升再分析资料春、夏、秋季数据质量,再分析资料偏差主要源于冬季气温偏差;JRA-55和ERA-interim气温数据在蒙古国地区可信度都比较高并各具优势,ERA-interim相对JRA-55偏差略小,而JRA-55则可以更为精准的拟合气温的变化趋势。

不同初始场对WRF模式风场模拟效果的影响分析

利用不同初始场资料驱动WRF模式,对香港地区夏季一个月风场进行高分辨率数值模拟试验,选用15个地面自动气象站测风数据及1个探空站垂直风廓线实测资料与模拟结果进行比较分析。结果表明,3种初始场方案均能较好模拟风场变化及分布特点,不同初始场资料会在一定程度上影响风场模拟结果;JRA-55方案高估风速现象较为明显,风向日变化模拟误差相对较大;NCEP FNL与ERA-Interim方案模拟近地面风场精度相当,且优于JRA-55方案。3种方案模拟的垂直风廓线均存在近地层风速增幅过快、最大风速出现高度与实际不符等问题,此外,NCEP FNL与ERA-Interim方案能够准确反映近地层风向廓线的变化趋势,而JRA-55方案模拟效果与实际相差较大。

1980-2016年青藏高原变暖时空特征及其可能影响原因

为全面认识1980-2016年期间青藏高原气温的时空变化,利用气象台站地表气温(TO)数据,对比分析了JRA-55(TJ)、ERA-Interim(TE)和MERRA(TM)三种再分析2 m气温资料在高原东部的适用性,并选取最优数据集相关参数进一步探讨高原气温变化的可能机制。结果表明,TO、TJ、TE和TM均能够揭示高原呈现的显著增温趋势,其年平均增温趋势分别为0.52,0.37,0.29和0.26℃·(10a)-1。对比三种再分析资料与TO年、季时空变化发现,TJ在高原的适用性优于TE和TM,可用来弥补高原西部观测的不足。TJ显示高原整体存在“双中心”变暖区,相比于夏季,冬季的变暖中心会发生“南移”,且中心最大变暖趋势[0.9℃·(10a)^-1]大于夏季[0.8℃·(10a)-1]。夏季升温趋势存在南缓北快差异可能与降水潜热变化有关,而中东部冬季变暖显著则可能与积雪-反照率反馈调节地表净辐射收支相关。

主流海表风场资料在舟山群岛近海的性能评估

再分析风场资料已广泛应用于我国舟山群岛海域可再生能源评估、海洋灾害预防决策以及港口运维和船舶运输等涉海发展领域,然而不同业务机构所提供的再分析数据在舟山近海的性能表现不一,严重阻碍了此类数据的有效应用。基于2018年全年单点浮标观测资料,综合评价了舟山群岛近海面(10 m)风场的长期变化趋势,并利用误差分析和风玫瑰图等统计工具对6种主流海表风场再分析资料,包括:ECMWF第五代全球大气再分析数据(the 5th generation ECMWF atmospheric reanalysis,ERA5)、NECP第二版全球高分辨率再分析数据(climate forecast system version 2,CFSv2)、美国宇航局物理海洋学分布存档中心的多卫星融合资料(cross-calibrated multi-platform,CCMP)、日本55年再分析数据(Japanese 55-year reanalysis,JRA-55)、第二版现代研究与应用回顾性分析数据(modern-era retrospective analysis for research and applications version 2,MERRA-2)和ECMWF哥白尼大气监测服务再分析数据(the Copernicus Atmosphere Monitoring Service,CAMS)在时间变化特征上进行了对比与评估。研究表明:在综合性能方面,ERA5对风场的再现能力最优,其次为JRA-55;在要素可信度方面,ERA5对风速的再现情况相对较优,而CFSv2的风向再现情况较好;风场产品在不同季节的模拟能力有所差异;不同风场产品在不同风速区间的重构能力也有所不同;在全年风向分布方面,各再分析资料都存在显著的东向偏差。研究结果为不同应用场景下风场资料的选取提供评估依据,并为进一步开发适用于舟山群岛近海的高精度长周期风场数据产品奠定基础。