美国NCEP/NCAR近50年全球再分析资料在我国气候变化研究中可信度的初步分析

对美国全球再分析资料在中国气候变化研究当中的可信度, 进行了初步的分析与检验, 结果表明: NCEP资料在对气候变化长期趋势变化的研究中, 不确定性较大, 通过对温度和气压的比较分析, 可看出, NCEP资料在我国东部和低纬的可信度比我国西部和高纬的高; 温度的可靠性比气压好; 1979年以后的NCEP资料的可信度高于前期。     

三种再分析气温资料在中国西部地区的可信度评价

再分析资料质量检验和可信度分析是其合理使用的必要前提,是提高气候变化研究成果可靠性的根本保证,为了评价NCEP-II、ERA-40和JRA-25三种再分析资料在中国西部地区的可信度,研究对比分析了2m气温产品的质量。结果表明,这三种再分析气温产品都能较好地反映中国西部地区气温的空间分布特征,在地形复杂区域与站点气温的差异比较大,而在地势相对平缓的地区这三种再分析资料都能提供高质量的气温产品。由于同化了地面观测资料,ERA-40、JRA-25气温产品的可信度相对较高,且能够提供更为详尽的大尺度气温变异性。总体上,ERA-40的质量优于其他两种再分析资料。     

中国区域ERA-40、NCEP-2再分析资料与观测资料的初步比较与分析

再分析资料在气候变化研究中有着广泛的应用,但是再分析资料在不同时空尺度上的可信度能够影响到研究结果。作者就中国区域的月平均地表(2 m)气温和降水两种基本气候变量在空间分布及其变化趋势上对ERA-40和NCEP-2与观测资料之间的差异做了一些比较和分析,对两套再分析资料的可信度进行了初步的检验。结果表明:两套再分析资料基本上都能反映出中国区域的温度场和降水场的时空分布,尽管在中国西部,尤其是青藏高原地区的差异比较较大;再分析资料在东部地区的可信度高于西部,温度场的可信度要高于降水场,ERA-40可信度要高于NCEP-2。     

封开县新旧站气象观测资料对比分析

基于新旧站2010年1、4、7、10月平行观测的气温、气压、相对湿度和全年风向风速资料,采用差值分析法和t检验,分析了气温、气压、相对湿度和风向风速在迁站前后的差异特征,结果表明:4个月份中,新站的定时观测气温、气压以及月平均气压、平均气温比旧站偏低;相对湿度7月份比旧站偏高,其他月份比旧站偏低;全年平均风速新站比旧站偏高,主导风向新旧站有差异;迁站前后气压和风速存在显著性差异。造成新旧站气象资料差异的主要原因可能是探测环境和海拔高度等因素发生变化。     

几种再分析地表气温资料在中国区域的适用性评估

应用台站观测资料对ERA-40、NCEP/NCAR、NCEP/DOE和JRA-25等几种再分析地表(2m)气温资料在中国不同区域、不同年代和季节的气候均值、年际变化和变率特征及其气候趋势等所反映出来的适用性问题进行了系统评估.结果表明,几种再分析产品在全国大多数地区的气候变化研究中都具有一定的合理性,特别是1979年以后的资料可靠性更高一些.但相比而言,它们在冬季的可信度一般要高于夏季,东部地区的可信度一般要高于西部地区;ERA-40和JRA-25再分析产品的适用性要高于NCEP/NCAR和NCEP/DOE再分析产品;其中,JRA-25在均值、年际变化和变率特征的描述上具有更高的可靠性,而ERA-40在长期气候变化趋势(44年)的描述上则要明显优于NCEP/NCAR再分析产品.     

东亚地区500 hPa位势高度场NCEP/NCAR再分析资料与ERA-40资料的比较

运用统计分析方法对3份500 hPa位势高度场资料,即NCEP/NCAR全球大气再分析月平均资料和欧洲中心ERA-40资料,国家气候中心的NMC资料(该资料的基础是站点观测资料的实测数据,并结合中央气象台的日常累积资料整编而成)进行比较,以讨论NCEP/NCAR再分析资料与ERA-40资料以及NMC资料的相关性,尤其在东亚地区的可靠性.3份资料综合分析得到如下结论:在东亚地区,特别是贝加尔湖以南至中国西北和中西部的大部分区域内(30°-50°N,80°-115°E),NCEP/NCAR资料和ERA-40资料各季的平均场、相关场均存在大范围的显著性差异区,差异最大的季节在夏季,时段为1958-1970年,而在冬季相关较好.同时NCEP/NCAR资料在20世纪60年代初出现异常低值,在60年代中期有突然的增长,而欧洲中心的ERA-40资料和国家气候中心的NMC资料均无此现象.针对以上问题,对北半球500 hPa资料的使用提出如下建议:在东亚地区应用NCEP/NCAR资料时,如果范围涉及贝加尔湖以南至中国西北和中西部地区(30°-50°N,80°-115°E),尽量应用20世纪70年代以后的资料,尤其在春、夏两季;而该区域内的ERA-40资料和NMC资料在这一时段内是基本一致,具有可信性.     

近40年青藏高原地区的气候变化--NCEP和ECMWF地面气温及降水再分析和实测资料对比分析

为了分析青藏高原地区的地面气候变化,利用我国高原地区的地面测站逐日平均气温和降水资料、NCEP(美国环境预报中心)、ECMWF(欧洲中期数值预报中心)的再分析值地面气温及降水量资料,对比分析了青藏高原的气候变化.分析发现,40年来所选地面代表测站气温变暖现象较明显(南部的帕里除外),特别是青藏高原北部的茫崖气温增暖非常显著,而40年再分析资料在青藏高原地区没有显示明显的气温变暖,没有大的地域差别,而再分析气温资料在华北平原地区却能显示出较明显的气温变暖,再分析气温资料尤其是NCEP地面气温资料在青藏高原上明显偏低.ECMWF再分析地面降水资料的年际变化显示,近40年来,青藏高原降水没有明显的变干或变湿趋势,但近十几年属于有资料以来较湿的时段.地面测站年降水观测值不像气温观测值那样有明显的变化趋势.     

自动站与人工站常规气象要素的对比分析

对比分析陕西省6个基准站2003—2005年自动站和人工观测的气压、气温和相对湿度,并对自动站观测的资料进行显著性检验。结果表明:自动站的气压和相对湿度观测值普遍低于人工观测值,偏差大都超出允许范围;气温月际变化不一,偏差基本在允许范围内,多数自动站观测值高于人工观测值,且夏季比冬季明显;自动站观测的气压、气温、相对湿度的月平均值与历史序列中的气压、气温、相对湿度无显著性差异。     

茂名新旧气象观测站观测资料对比分析

利用茂名新、旧气象站2002年1～8月的对比观测资料,对气压、气温、相对湿度和降水1～8月的月平均资料和1、4、7月逐日平均资料进行分析.结果表明:新站的平均气温、平均气压比旧站偏低,平均相对湿度偏高,降水总量持平但各月差值不一,造成差异的主要原因是2站的海拔高度和地理位置等气象探测环境差异较大.     

近33a亚洲高纬地区地面气温变化特征分析

利用1973～2005年地面气温资料,对亚洲高纬地区长期变化趋势进行了统计分析,结果表明:近33 a亚洲高纬度地区平均温度有明显的上升趋势,只有极少数站有明显的降温趋势;在逐站分析温度的年际变化后发现,亚洲高纬度地区年平均温度的变化又存在着明显的区域特征,105°E～110°E,55°N～65°N之间是增温最快的地区,...     

ERA5再分析数据适用性初步评估

利用山东省及周边地区10个站点的地面和高空观测资料对ERA5再分析资料的适用性进行了初步评估。结果表明：再分析的海平面气压和2 m温度与实况资料的相关性明显优于2 m相对湿度和10 m风场;高空温度和相对湿度在对流层中低层的适用性要好于高层,而位势高度和风场在中高层适用性较好;海平面气压再分析与实况的相关有着最明显的季节变化,2 m温度、2 m相对湿度和10 m风速则在部分站点有较明显的季节变化,而10 m风向的相关系数更多地表现出站点之间的差异,高空要素的适用性,季节和区域差异不明显。另外,对比发现,ERA5的适用性总体上要优于ERA-Interim再分析资料,地面和对流层低层的相对湿度、风场提高更为明显。     

Impacts of assimilated data on reanalysis climatology

Impacts of the observing systems and meteorological parameters on a reanalyzed climatology are investigated using an assimilation algorithm based on the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) reanalysis system. The one-year analyzed climatology is generated in a standard analysis using all of the observations, which is named the control run. Additional climatology data sets are produced by selectively choosing observational systems or meteorological variables in the reanalysis system. It is found that the radiosonde-only observation is sufficient for reproducing the reanalysis climatology. Satellite observations have no significant contribution to the large-scale fields. The importance of meteorological variables on the analyzed climatology is temperature, wind, and moisture in that order, where the mass observation is found to have a greater impact on the analyzed climatology than wind. It is, however, noted that the moisture field demonstrates a profound influence on the surface hydroclimate such as cloud cover, radiation flux, and land surface temperature.     

A high resolution global reanalysis highlighting the winter monsoon. Part I, reanalysis fields

Summary This study entails a reanalysis of the TOGA-COARE, CEPEX period covering the months December 1992 through March 1993. Four times daily data sets were reanalyzed for the period. The unique aspect of this reanalysis is that (i) it incorporates physical initialization i.e. assimilation of rainfall from raingauge and satellite (OLR and microwave radiometric data), (ii) this reanalysis is carried out at a very high resolution, T170, global spectral model (space resolution of roughly 70 km at equator) and (iii) ECMWF reanalysis is used as a first guess field for this study.This analysis is global and is carried out at 15 vertical levels using the FSU global spectral model. In this study we have analyzed a large number of meterological variables such as wind, temperature, humidity, surface pressure, vertical velocity, cloud, rainfall, surface fluxes and diabatic heating. In this part of the paper we present the monthly mean and samples of daily fields of the reanalysis. Some of the major results of the reanalysis include the relationships among the flow fields and the ITCZ convection; the shallow northeast monsoon current and its rapid turning towards westerlies with height; an overabundance of middle clouds over the region of the ITCZ; and the distribution of heat sources and sinks. A motivation for this reanalysis is the forthcoming Indian Ocean Experiment (INDOEX), which is an international field experiment to be conducted during the winter monsoon time frame in 1999.With 25 Figures     

广东省冬季逐日最低气温的预报方法

为了能结合数值预报产品做好广东省逐日最低气温的预报,利用1998~2007年冬季(11月~次年2月)美国NCEP/NCAR再分析资料和常规气象观测资料,选取20°~27.5°N,107.5°~117.5°E区域内的海平面气压、850 hPa温度、850 hPa相对湿度、850 hPa纬向风(u)、850 hPa经向风分量(v)和500hPa位势高度等6个要素作为预报因子,以韶关、梅州、广州、阳江、汕头等5个站分别作为广东5个部分的代表站,采用能选取"最优"因子的逐步回归方法建立5个代表站的11月~次年2月逐日的最低气温预报方程,并对预报方程进行检验。结果表明:采用逐步回归预报方法建立的广东省5个代表站的逐日最低气温预报方程具有一定的预报能力,但也存在预报结果比实况偏低的不足。     

Modelling of Water Surface Temperature of Three Lakes on the Tibetan Plateau using a Physically Based Lake Model

ABSTRACT

This study was carried out to quantify the physical processes of lakes in the Tibetan Plateau using the Community Land Model, version 4.5 (CLM4.5), coupled with a physically based, 10-layer lake model developed by the National Center for Atmospheric Research. The CLM was forced with 10?km resolution reanalysis data to attempt to understand detailed lake processes and how these processes affect lake surface temperature. In this study, we simulated seasonal and interannual variations of lake surface temperature for Lake Qinghai, Zhaling Co, and Nam Co in the Tibetan Plateau and compared these simulations with observations. The results showed that the CLM4.5 lake model simulations reproduced the observed lake surface temperatures for Lake Qinghai and Zhaling Co well but reproduced those for Nam Co poorly. Through detailed analysis, we found that the simulated biases for Nam Co result largely from the unrealistic parameterization of eddy diffusivity. By expanding this parameter, the lake surface temperature simulations improved remarkably. In addition, erroneous lake ice cover simulations contributed to the simulated lake surface temperature bias in the cold seasons.     

Comparison of Characteristics Between the South China Sea Summer Monsoon Outbreaks in 2004 and 2008

The South China Sea summer monsoon is an important system affecting the weather and climate in China;its outbreak and evolution vary from year to year.Using the reanalysis data from the U.S.National Centers for Environmental Prediction (NCEP) and outgoing longwave radiation (OLR) data from the National Oceanic and Atmospheric Administration (NOAA),USA,we analyze the circulation pattern,precipitation distribution,convection,temperature,and humidity around the monsoon outbreaks in 2004 and 2008.Results show that the monsoon had a late onset in 2004 (May 19) but an early outbreak in 2008 (May 4).Prior to the monsoon outbreak in 2008,cross-equatorial flows in Somalia were weaker than in 2004,subtropical precipitation did not arrive in southern China as it did in 2004,and the strongest convection was located more southward than in 2004.The results also indicate that accumulated rainfall in the Indochina Peninsula was about 61% of that in 2004 during a period of 25 days leading up to the monsoon outbreak,causing differences in land surface processes and then different activity levels for the summer monsoon.Post-onset warm and humid conditions in 2008 (2004) maintained through the end of October (mid-September),while the summer monsoon lasted longer in 2008 than in 2004.     

Validation of ECMWF and NCEP–NCAR Reanalysis Data in Antarctica

The European Center for Medium-Range Weather Forecast (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) ECMWF (ERA-40) and NCEP-NCAR reanalysis data were compared with Antarctic station observations, including surface-layer and upper-layer atmospheric observations, on intraseasonal and interannual timescales. At the interannual timescale, atmospheric pressure at different height levels in the ERA-40 data are in better agre...     

夏季西太平洋副热带高压南北位置变动特征及其影响

使用ECMWF再分析数据集资料中的位势高度场、三维风场、温度场、相对湿度场、海温场以及中国气象局730站地面降水资料和日最高温度资料,对比分析研究了7月份西太平洋副高位置偏南和偏北过程(持续满足南、北位置指标6天以上定义为一次南、北部型过程)所对应的动态气候特征及其演变.分析首先揭示出了西太平洋副高的南北位置变化存在季...     

Impacts of the Zonal Position of the East Asian Westerly Jet Core on Precipitation Distribution During Meiyu of China

The east-west location change of the East Asian westerly jet （EAWJ） at 200 hPa during Meiyu and the associated spatial distribution variation of precipitation in the middle-lower reaches of the Yangtze River （MLYR） are investigated by using the 40-yr NCEP/NCAR （National Centers for Environmental Prediction/National Center for Atmospheric Research） pentad mean reanalysis data and daily precipitation observation data from 1958 to 1997. The results show that there are two areas over which the 200-hPa EAWJ center appears most frequently during the Meiyu period： one is the western Pacific （WP） and the other is the East Asian continent （EAC）. During the Meiyu period, the westerly jet over the EAC is weak, and the core of the westerly jet over the WP splits up with reduced intensity and disappears by the end of Meiyu. The changes in the location and intensity of the westerly jet are associated not only with the starting and ending dates of Meiyu, but also with the spatial distribution and intensity of precipitation in the MLYR. It is found that when the westerly jet core in the upper troposphere is located over the WP and is coupled with an 850-hPa southwesterly jet, heavy precipitation accompanied by strong convergence and plenty supply of water vapor, occurs in the lower reaches of the Yangtze River. If the 200-hPa westerly jet core is located over the EAC, and without an 850-hPa southwesterly jet, only weak precipitation occurs in the MLYR. Therefore, the longitudinal location of the EAWJ core plays an important role in determining the upper- to lower-level circulation structure and the spatial distribution of heavy precipitation in the MLYR during the Meiyu period.     

华东高温期的大气环流特征分析

利用NCEP/NCAR再分析资料和地面气象站点资料,对1951—2005年华东高温日数较多（少）月和高温过程各阶段的500 hPa位势高度、850 hPa温度和相对湿度及700 hPa垂直速度的环流特征进行对比分析。结果表明：在高温日数较多月,副高西伸,850 hPa温度较高而相对湿度较低,华东中南部下沉气流明显,华东多为位势高度、温度和垂直速度正距平及相对湿度负距平;而在高温日数较少月,副高东退,850 hPa温度较低而相对湿度较高,整个华东为上升气流,并为位势高度、温度和垂直速度负距平及相对湿度正距平。与高温前期和衰退期相比,高温盛期副高北抬西进,华东850 hPa温度较高而相对湿度较低,华东南部下沉气流强盛,各要素距平值增加,多数要素距平中心移向华东或其周边。高温间断期则比盛期各要素距平减弱。大气环流要素场及其距平场的变动可以作为预报华东7—8月高温日数多寡和高温进程的参考依据。