基于NCEP FNL资料的山西岢岚地区雨雪天气诊断可信度分析

基于山西岢岚地区2005—2014年共1218个雨雪天气日的NCEP FNL资料(1°×1°)与探空资料,采用偏差、绝对差、相关系数和偏差区间占有率的统计方法,对常规物理量(温度、相对湿度、纬向风和经向风)和诊断物理量(T_800-500、T_d800和TT_d700)进行统计分析。结果表明:常规物理量中的温度平均偏差值和绝对差值最小、相关系数值最大,分别为-0. 22℃、1. 02℃、0. 90,可信度最高;而相对湿度的平均偏差值和绝对差值最大、相关系数值最小,分别为12. 31%、19. 68%和0. 63,可信度最低;纬向风和经向风的可信度相差不大,略低于温度;诊断物理量T_800-500、T_d800和TT_d700的偏差值分别为-0. 08℃、1. 50℃和2. 79℃,绝对差值分别为1. 21℃、3. 33℃和4. 14℃,相关系数值分别为0. 95、0. 92和0. 74,偏差值为[-5,5]占总数百分比分别为98. 77%、80. 30%和75. 04%。即T_800-500可信度最高,TT_d700指数可信度最低。     

过去60年来南极冰盖近地面气温时空变化研究

如何将十分有限的器测资料和再分析资料有机联系起来,充分借助它们各自的优势,分析南极冰盖气温时空变化具有重要意义。以CFSR（the Climate Forecast System Reanalysis）、ERA5（the European Centre for Medium-Range Weather Forecasts Fifth-generation Reanalysis）和MERRA-2（the Modern-Era Retrospective Analysis for Research and Applications,version 2）再分析资料分别作为背景场,利用南极冰盖具有超过50年连续观测的站点气温观测资料,分别重建了1960~2019年冰盖近地面月气温时空数据集,借助于未参与重建的70个站点观测资料进行了验证分析。在此基础上,利用精度最高的重建数据集探讨了冰盖过去60年来气温时空变化特征。精度验证结果表明：基于ERA5重建的月气温数据集精度最高,相关系数为0.70,均方根误差为0.49℃。1960~2019年,南极半岛和西南极冰盖呈现显著增温趋势,而且显著变暖延伸到60°~180°E的东南极内陆大部分区域。全球变暖停滞事件在南极半岛和西南极冰盖发生,且增温减缓程度更明显：1999~2019年间年和春季平均气温均呈明显降低趋势。1960~1998年,整个东南极冰盖气温没有显著变化,但是1999~2019年东南极冰盖内陆较大区域呈现了显著变暖趋势。这些结果有助于增进对不同时间尺度南极冰盖气温变化区域差异性的理解。

     

Analysis and comparison of heat flux of landfast ice during 2016 in the Prydz Bay,Antarctica

Long term in situ atmospheric observation of the landfast ice nearby Zhongshan Station in the Prydz Bay was performed from April to November 2016. The in situ observation, including the conventional meteorological elements and turbulent flux, enabled this study to evaluate the sea ice surface energy budget process. Using in situ observations, three different reanalysis datasets from the European Centre for Medium-Range Weather Forecasts Interim Re-analysis(ERA-Interim), National Centers for Environmental Prediction Reanalysis2(NCEP R2), and Japanese 55-year Reanalysis(JRA55), and the Los Alamos sea ice model, CICE, output for surface fluxes were evaluated. The observed sensible heat flux(SH) and net longwave radiation showed seasonal variation with increasing temperature. Air temperature rose from the middle of October as the solar elevation angle increased.The ice surface lost more energy by outgoing longwave radiation as temperature increased, while the shortwave radiation showed obvious increases from the middle of October. The oceanic heat flux demonstrated seasonal variation and decreased with time, where the average values were 21 W/m~2 and 11 W/m~2, before and after August,respectively. The comparisons with in situ observations show that, SH and LE(latent heat flux) of JRA55 dataset had the smallest bias and mean absolute error(MAE), and those of NCEP R2 data show the largest differences.The ERA-Interim dataset had the highest spatial resolution, but performance was modest with bias and MAE between JRA55 and NCEP R2 compare with in situ observation. The CICE results(SH and LE) were consistent with the observed data but did not demonstrate the amplitude of inner seasonal variation. The comparison revealed better shortwave and longwave radiation stimulation based on the ERA-Interim forcing in CICE than the radiation of ERA-Interim. The average sea ice temperature decreased in June and July and increased after September,which was similar to the temperature measured by buoys, with a bias and MAE of 0.9°C and 1.0°C, respectively.     

Seasonal and Monthly Variation of Vertical Structure of Temperature,Salinity and Heat Flux of the Bay of Bengal

Seasonal and monthly variations of heat flux have been investigated in this study using the Modular Ocean Model of version 3 (MOM 3) simulations and 52 years Simple Ocean Data Assimilation (SODA) products. These variations of the heat flux in different boxes of the Bay of Bengal (BOB) in different depths show the different behavior of the boxes. It is seen that the model and SODA results are comparable. The basin shows north-south variation in the surface from winter to spring whereas there is east-west variation in the mixed layer throughout the year except winter. The remote effect caused by warm water penetration from Pacific Ocean through the Strait of Malacca and coastal Kelvin waves keeps the basin warm most of the year. This article addresses the mechanisms of the seasonal variation of the vertical structure of the temperature and heat flux components.     

ERA-Interim气温数据在中国区域的适用性评估

运用中国756个观测站点的逐月平均气温数据,对比分析了ERA-Interim再分析资料的误差。结果发现:ERA-Interim再分析资料能够很好地反映观测值的年际变化,相关性达到0.955~0.995。ERA-Interim在580个站点的冷偏差或暖偏差小于1℃,占站点总数的76.7%,可信度较高。64个站点的冷偏差或暖偏差大于5℃,可信度较低。ERA-Interim在东部地区的暖偏差多于西部地区,冷偏差的高值主要集中在西部地区的高海拔站点。海拔低于200 m的站点偏差最小,适用性好,多数海拔3 000 m以上的站点呈现较大冷偏差,适用性较差。通过回归分析发现,观测站点与ERA-Interim格点的高度差是导致误差的主要原因,因此通过高程校正能够有效降低误差,提高ERA-Interim适用性。     

我国中部和南部地区降水再循环率评估

利用1976～1995 年20 年NCEP 再分析资料,对我国中、南部地区降水再循环率进行了评估,发现长江上游总的降雨有20%来自我国中、南部地区水汽蒸发,长江中下游总的降雨则有40%来自这一地区. 降水再循环率有很强的季节变化规律,8、9、10三个月的降水再循环率最高,达四成左右,而5、6、7三个月的降水再循环率不到四分之一.蒸发率和降水再循环率在20年中均有增加的趋势,这可能与气候变暖有关.     

中国日降雨量变化特征分析

将旋转主成分分析和复变量莫莱特小波分析应用于14a中国境内实测与ECMWF再分析日降雨量资料,研究其年际、季际与季节内变化的时空分布特征和再分析日降雨量资料的有效性。结果表明:从实测资料中分析的降水特征,都可以由再分析资料再现出来。除周内振荡大有出入外,其余频率的振荡二者大致相符或基本吻合。因此,周内振荡还不能被再分析数据较好地刻划,但是与旱涝灾害和季风爆发联系密切的周际以上振荡,在再分析日降雨量中基本上能被正确地表现出来。     

近45年全球海域波浪能资源研究及等级区划

基于来自ECMWF的资料将1957年09月---2002年08月风浪、涌浪分离的ERA-40 wave reanalysis,对全球海域的波浪能资源进行重新审视．充分依据涌浪具有能量大、稳定性好等优点,利于波浪能的采集与转换,从提高波浪能资源有效利用率的角度出发,综合考虑能流密度的大小、能级频率、能流密度的稳定性和长期变化趋势等,对全球海域的波浪能资源进行系统性研究,并构建一套波浪能资源评估系统,对全球海域的波浪能资源进行功能区划,为海浪发电、海水淡化等波浪能资源开发工作提供科学依据．     

南极洲低层两种位势高度再分析资料的比较

比较NCEP/NCAR和ECMWF两种再分析资料南半球低层等压面(700 hPa及以下)的平均位势高度场,结果表明:两者在南极洲差异显著,除12月、1月(南半球夏季)外,NCEP/NCAR资料存在一个虚假的很强的极地高压,而ECMWF资料正常。分析表明该两种再分析资料的上述差异来源于南极洲地面以下虚拟气压场的产生过程;NCEP/NCAR资料较ECMWF少了一个对南极洲过低地面温度的修正。由此得到的NCEP/NCAR资料若用于南半球低层大气环流整体结构的分析,会导致严重的错误。     

风云三号C星微波全球地表温度产品精度评估

地表温度是衡量地表水热平衡的关键参数,微波地表温度因其范围大、全天候等独特的优势,在气候、农业和环境等领域得到广泛应用。基于经质量控制的MODIS地表温度产品对风云三号卫星C星的微波地表温度日产品和月平均产品进行验证评估,结果显示:FY-3C卫星升轨(夜晚)和降轨(白天)微波地表温度日产品平均分别高估8. 7 K、低估13. 2 K,月平均产品平均分别高估7. 9 K、低估12. 0 K,日产品和月平均产品的反演误差都在15K以内。在全球空间分布上,升轨(夜晚)和降轨(白天)月产品误差分别呈现高估和低估,热带雨林区和沙漠、荒漠区域在夜晚分别高估5 K以内和30 K以内,白天则分别低估10 K以内和10～30 K。不同土地覆盖类型间FY-3C微波地表温度反演精度存在差异,总体上升轨(夜晚)比降轨(白天)的精度高,反演精度最高和最低的土地类型分别是常绿阔叶林和荒漠、稀疏植被,不同土地覆盖类型间的地表温度反演精度在季节上存在明显差异。根据分析结果,改进FY-3C微波地表温度的反演算法,可进一步提高微波地表温度的反演精度。