首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 875 毫秒
1.
利用实测资料对NCEP-1、ERA-40和20CR再分析降水资料在中国范围内均值、年际变化、相关性和长期趋势等方面进行比较评估。结果表明,平均而言ERA-40年降水量和实测值最为接近,而20CR和NCEP-1年降水量明显偏多,三者差值百分比分别为-1.3%,55.0%和36.9%;三种再分析降水偏差最大区均出现在西南地区,最大偏差值都在600 mm以上;年际变化上,ERA-40和NCEP-1自20世纪70年代中期开始年降水差值百分比出现一定波动性,而20CR在整个研究时段年降水差值百分比基本稳定;三套资料和实测资料的相关性具有明显的区域性特征,东部相关系数明显高于西部,值得一提的是ERA-40在大部地区的相关性好于其他两套资料;ERA-40和20CR则对大部分区域降水变化趋势的描述好于NCEP-1资料。  相似文献   

2.
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。  相似文献   

3.
刘刚  徐士琦  廉毅 《气象学报》2019,77(2):303-314
基于阻塞高压（阻高）客观识别方法,利用1979-2016年夏季（6-8月）NCEP-Ⅰ、NCEP-Ⅱ逐日再分析资料和ERA-interim逐6 h再分析资料对识别结果进行对比分析;并以D类（130°-160°E）阻高为例,讨论其对6月中国东北地区气候的可能影响。结果表明:NCEP-Ⅰ和NCEP-Ⅱ再分析资料对阻高活动天数、发生频次及年代际变化的识别结果差异较小,而ERA-interim与前两种资料的结果差别较大。3种再分析资料下,夏季各类阻高活动天数均与500 hPa高度场存在相应的显著相关区,且形态相近。但前两种资料对于各类阻高的表征结果较为一致,而ERA-interim再分析资料对各类阻高面积和范围的表征偏小。6月D类阻高活动日数与东北地区气温和降水关系密切,D类阻高活跃年,大气环流以经向型为主,东北地区低层低温、暖平流,高层高温、冷平流的结构指示大气层结不稳定,且东北上空为异常低压环流控制,上升气流较强,有利于6月东北地区出现低温多雨天气。鄂霍次克海地区是6月罗斯贝波的重要来源地之一,而6月D类阻高的形成可能与海-陆温差有关。   相似文献   

4.
Summer precipitation products from the 45-Year European Centre for Medium-Range Weather Forecast (ECMWF) Reanalysis (ERA-40), and NCEP-Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (NCEP-2), and Climatic Research Unit (CRU) TS 2.1 dataset are compared with the corresponding observations over China in order to understand the quality and utility of the reanalysis datasets for the period 1979–2001. The results reveal that although the magnitude and location of the rainfall belts differ among the reanalysis, CRU, and station data over South and West China, the spatial distributions show good agreement over most areas of China. In comparison with the observations in most areas of China, CRU best matches the observed summer precipitation, while ERA-40 reports less precipitation and NCEP-2 reports more precipitation than the observations. With regard to the amplitude of the interannual variations, CRU is better than either of the reanalyses in representing the corresponding observations. The amplitude in NCEP-2 is stronger but that of ERA-40 is weaker than the observations in most study domains. NCEP-2 has a more obvious interannual variability than ERA-40 or CRU in most areas of East China. Through an Empirical orthogonal function (EOF) analysis, the main features of the rainfall belts produced by CRU agree better with the observations than with those produced by the reanalyses in the Yangtze-Huaihe River valley. In East of China, particularly in the Yangtze-Huaihe River valley, CRU can reveal the quasi-biennial oscillation of summer precipitation represented by the observations, but the signal of ERA-40 is comparatively weak and not very obvious, whereas that of NCEP-2 is also weak before 1990 but very strong after 1990. The results also suggest that the magnitude of the precipitation difference between ERA-40 and the observations is smaller than that between NCEP-2 and the observations, but the variations represented by NCEP-2 are more reasonable than those given by ERA-40 in most areas of East China to some extent.  相似文献   

5.
This study examines the ability of the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model (RegCM3) to reproduce seasonal mean climatologies, annual cycle and interannual variability over the entire African continent and different climate subregions. The new European Center for Medium Range Weather Forecast (ECMWF) ERA-interim reanalysis is used to provide initial and lateral boundary conditions for the RegCM3 simulation. Seasonal mean values of zonal wind profile, temperature, precipitation and associated low level circulations are shown to be realistically simulated, although the regional model still shows some deficiencies. The West Africa monsoon flow is somewhat overestimated and the Africa Easterly Jet (AEJ) core intensity is underestimated. Despite these biases, there is a marked improvement in these simulated model variables compared to previous applications of this model over Africa. The mean annual cycle of precipitation, including single and multiple rainy seasons, is well captured over most African subregions, in some cases even improving the quality of the ERA-interim reanalysis. Similarly, the observed precipitation interannual variability is well reproduced by the regional model over most regions, mostly following, and sometimes improving, the quality of the ERA-interim reanalysis. It is assessed that the performance of this model over the entire African domain is of sufficient quality for application to the study of climate change and climate variability over the African continent.  相似文献   

6.
This study investigates the recent extreme temperature trends across 19 stations in the Klang Valley, Malaysia, over the period 2006-16. Fourteen extreme index trends were analyzed using the Mann-Kendall non-parametric test, with Sen’s slope as a magnitude estimator. Generally, the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature in the Klang Valley increased significantly, by 0.07°C yr~(-1), 0.07°C yr~(-1)and 0.08°C yr~(-1),respectively. For the warm temperature indices, the results indicated a significant upward trend for the annual maximum of maximum temperature, by 0.09°C yr~(-1), and the annual maximum of minimum temperature, by 0.11°C yr~(-1). The results for the total number of warm days and warm nights showed significant increasing trends of 5.02 d yr~(-1)and 6.92 d yr~(-1),respectively. For the cold temperature indices, there were upward trends for the annual minimum of maximum temperature,by 0.09°C yr~(-1), and the annual minimum of minimum temperature, by 0.03°C yr~(-1), concurrent with the decreases in the total number cold days (TX10P), with-3.80 d yr~(-1), and cold nights (TN10P), with-4.33 d yr~(-1). The 34°C and 37°C summer days results showed significant upward trends of 4.10 d yr~(-1) and 0.25 d yr~(-1), respectively. Overall, these findings showed upward warming trends in the Klang Valley, with the minimum temperature rate increasing more than that of the maximum temperature, especially in urban areas.  相似文献   

7.
  相似文献   

8.
Using the regional terrestrial Net Primary Production (NPP) from different observations and models over China, we validated the NPP simulations and explored the relationship between NPP and climate variation at interannual and decadal scales in the Modified Sheffield Dynamic Global Vegetation Model (M-SDGVM) during 1981–2000. M-SDGVM shows agreement with the NPP data from 743 sites under the Global Primary Production Data Initiative (GPPDI). The spatial and the zonal averaged NPP of M-SDGVM agree well with ...  相似文献   

9.
Global monsoon: Dominant mode of annual variation in the tropics   总被引：13，自引：0，他引：13  
This paper discusses the concept of global monsoon. We demonstrate that the primary climatological features of the tropical precipitation and low-level circulation can be represented by a three-parameter metrics: the annual mean and two major modes of annual variation, namely, a solstitial mode and an equinoctial asymmetric mode. Together, the two major modes of annual cycle account for 84% of the annual variance and they represent the global monsoon. The global monsoon precipitation domain can be delineated by a simple monsoon precipitation index (MPI), which is the local annual range of precipitation (MJJAS minus NDJFM in the Northern Hemisphere and NDJFM minus MJJAS in the Southern Hemisphere) normalized by the annual mean precipitation. The monsoon domain can be defined by annual range exceeding 300 mm and the MPI exceeding 50%.The three-parameter precipitation climatology metrics and global monsoon domain proposed in the present paper provides a valuable objective tool for gauging the climate models’ performance on simulation and prediction of the mean climate and annual cycle. The metrics are used to evaluate the precipitation climatology in three global reanalysis products (ERA40, NCEP2, and JRA25) in terms of their pattern correlation coefficients and root mean square errors with reference to observations. The ensemble mean of the three analysis datasets is considerably superior to any of the individual reanalysis data in representing annual mean, annual cycle, and the global monsoon domain. A major common deficiency is found over the Southeast Asia-Philippine Sea and southeast North America-Caribbean Sea where the east–west land–ocean thermal contrast and meridional hemispheric thermal contrast coexist. It is speculated that the weakness is caused by models’ unrealistic representation of Subtropical High and under-represented tropical storm activity, as well as by neglecting atmosphere–ocean interaction in the reanalysis. It is recommended that ensemble mean of reanalysis datasets be used for improving global precipitation climatology and water cycle budget. This paper also explains why the latitudinal asymmetry in the tropical circulation decreases with altitude.  相似文献   

10.
Summary Meteorological and glaciological analyses are integrated to examine the precipitation trends during the last three decades over the ice sheets covering Antarctica and Greenland. For Antarctica, the best data source is provided by glaciologically-measured trends of snow accumulation, and for limited sectors of East Antarctica consistency with precipitation amounts calculated from the atmospheric water balance equation is obtained. For Greenland, precipitation rates parameterized from atmospheric analyses yield the only comprehensive depiction. The precipitation rate over Antarctica appears to have increased by about 5% over a time period spanning the accumulation means for the 1955–65 to 1965–75 periods, while over Greenland it has decreased by about 15% since 1983 with a secondary increase over the southern part of the ice sheet starting in 1977. At the end of the 10-year overlapping period, the global sea-level impact of the precipitation changes over Antarctica dominates that for Greenland and yields a net ice-sheet precipitation contribution of roughly 0.02 mm yr–1. These changes are likely due to marked variations in the cyclonic forcing affecting the ice sheets, but are only weakly reflected in the temperature regime, consistent with the episodic nature of cyclonic precipitation. These conclusions are not founded on high quality data bases. The importance of such changes for understanding global sea-level variations argues for a modest research effort to collect simultaneous meteorological and glaciological observations in order to describe and understand the current precipitation variations over both ice sheets. Some suggestions are offered for steps that could be taken.With 8 Figures  相似文献   

11.
This study analyzes the temporal change of Normalized Difference Vegetation Index (NDVI) for temperate grasslands in China and its correlation with climatic variables over the period of 1982–1999. Average NDVI of the study area increased at rates of 0.5% yr−1 for the growing season (April–October), 0.61% yr−1 for spring (April and May), 0.49% yr−1 for summer (June–August), and 0.6% yr−1 for autumn (September and October) over the study period. The humped-shape pattern between coefficient of correlation (R) of the growing season NDVI to precipitation and growing season precipitation documents various responses of grassland growth to changing precipitation, while the decreased R values of NDVI to temperature with increase of temperature implies that increased temperature declines sensitivity of plant growth to changing temperature. The results also suggest that the NDVI trends induced by climate changes varied between different vegetation types and seasons.  相似文献   

12.
The origin of bromoform in seawater and atmosphere, as well as possible sinks and breakdown mechanisms, is discussed. A bromoform budget is calculated for the Kattegatt area between Sweden and Denmark, where the input of bromoform from a power plant is significant. Both anthropogenically (250×106 g yr-1) and biogenically (350×106 g yr-1, 0.016 g m-2 yr-1) produced bromoform is likely to have a great impact locally on the inventory and the release to the atmosphere. Using measured surface concentrations of bromoform, the total annual release from the Kattegatt to the atmosphere is estimated to 550×106 g (0.025 g m-2 yr-1).  相似文献   

13.
Various types of satellite (AIRS/AMSU, MODIS) and ground measurements are used to analyze temperature trends in the four vertical layers (skin/surface, mid-troposphere, and low stratosphere) around the Korean Peninsula (123–132°E, 33–44°N) during the period from September 2002 to August 2010. The ground-based observations include 72 Surface Meteorological Stations (SMSs), 6 radiosonde stations (RAOBs), 457 Automatic Weather Stations (AWSs) over the land, and 5 buoy stations over the ocean. A strong warming (0.052 K yr?1) at the surface, and a weak warming (0.004～0.010 K yr?1) in the mid-troposphere and low stratosphere have been found from satellite data, leading to an unstable atmospheric layer. The AIRS/AMSU warming trend over the ocean surface around the Korean Peninsula is about 2.5 times greater than that over the land surface. The ground measurements from both SMS and AWS over the land surface of South Korea also show a warming of 0.043～0.082 K yr?1, consistent with the satellite observations. The correlation average (r = 0.80) between MODIS skin temperature and ground measurement is significant. The correlations between AMSU and RAOB are very high (0.91～0.95) in the anomaly time series, calculated from the spatial averages of monthly mean temperature values. However, the warming found in the AMSU data is stronger than that from the RAOB at the surface. The opposite feature is present above the mid-troposphere, indicating that there is a systematic difference. Warming phenomena (0.012～0.078 K yr?1) are observed from all three data sets (SMS, AWS, MODIS), which have been corroborated by the coincident measurements at five ground stations. However, it should also be noted that the observed trends are subject to large uncertainty as the corresponding 95% confidence intervals tend to be larger than the observed signals due to large thermal variability and the relatively short periods of the satellitebased temperature records. The EOF analysis of monthly mean temperature anomalies indicates that the tropospheric temperature variability near Korea is primarily linked to the Arctic Oscillation (AO), and secondarily to ENSO (El Niño and Southern Oscillation). However, the low stratospheric temperature variability is mainly associated with Southern Oscillation and then additionally with Quasi-Biennial Oscillation (QBO). Uncertainties from the different spatial resolutions between satellite data are discussed in the trends.  相似文献   

14.
近30年全球干旱半干旱区的蒸散变化特征   总被引：2，自引：0，他引：2  
张霞  李明星  马柱国 《大气科学》2018,42(2):251-267
全球变暖加剧了气候系统能量和水分循环相互作用的变化,水分平衡变化导致极端旱涝事件频发。地表蒸散是能量水分循环的重要过程,是理解气候变化的关键环节。本文基于1982~2011年FLUXNET-MTE观测资料和ERA-Interim再分析资料,分析了全球干旱半干旱区蒸散的时空变化特征及典型区域的变幅、趋势和季节变化。结果表明:（1）干旱半干旱区多年平均蒸散量小于300 mm。冬季蒸散量最小,夏季最大且变率也最强。1990年代前后,干旱半干旱区蒸散发生了明显的年代际转变,暖季的年代际差异尤为明显。（2）近30年来,东半球干旱半干旱区蒸散量呈增加趋势,西半球呈减小趋势。典型区域来看,南非呈显著增加趋势[25.14 mm（10 a）-1],美国西南部呈显著减小趋势[-19.86 mm（10 a）-1];萨赫勒、中国北部和澳大利亚呈增加趋势,阿根廷及智利南部呈减小趋势。（3）蒸散变化与温度、降水的变化联系密切,三者具有相似的年循环变化,但三者间相关性在干旱半干旱区具有显著的差异性。  相似文献   

15.
In this paper, we evaluate several timely, daily air-sea heat flux products (NCEP, NCEP2, ERA-Interim and OAFlux/ISCCP) against observations and present the newly developed TropFlux product. This new product uses bias-corrected ERA-interim and ISCCP data as input parameters to compute air-sea fluxes from the COARE v3.0 algorithm. Wind speed is corrected for mesoscale gustiness. Surface net shortwave radiation is based on corrected ISCCP data. We extend the shortwave radiation time series by using “near real-time” SWR estimated from outgoing longwave radiation. All products reproduce consistent intraseasonal surface net heat flux variations associated with the Madden-Julian Oscillation in the Indian Ocean, but display more disparate interannual heat flux variations associated with El Ni?o in the eastern Pacific. They also exhibit marked differences in mean values and seasonal cycle. Comparison with global tropical moored buoy array data, I-COADS and fully independent mooring data sets shows that the two NCEP products display lowest correlation to mooring turbulent fluxes and significant biases. ERA-interim data captures well temporal variability, but with significant biases. OAFlux and TropFlux perform best. All products have issues in reproducing observed longwave radiation. Shortwave flux is much better captured by ISCCP data than by any of the re-analyses. Our “near real-time” shortwave radiation performs better than most re-analyses, but tends to underestimate variability over the cold tongues of the Atlantic and Pacific. Compared to independent mooring data, NCEP and NCEP2 net heat fluxes display ~0.78 correlation and >65?W?m?2 rms-difference, ERA-I performs better (~0.86 correlation and ~48?W?m?2) while OAFlux and TropFlux perform best (~0.9 correlation and ~43?W?m?2). TropFlux hence provides a useful option for studying flux variability associated with ocean–atmosphere interactions, oceanic heat budgets and climate fluctuations in the tropics.  相似文献   

16.
In this study, the applicability of the statistical downscaling model (SDSM) in modeling five extreme precipitation indices including R10 (no. of days with precipitation ≥10?mm?day?1), SDI (simple daily intensity), CDD (maximum number of consecutive dry days), R1d (maximum 1-day precipitation total) and R5d (maximum 5-day precipitation total) in the Yangtze River basin, China was investigated. The investigation mainly includes the calibration and validation of SDSM model on downscaling daily precipitation, the validation of modeling extreme precipitation indices using independent period of the NCEP reanalysis data, and the projection of future regional scenarios of extreme precipitation indices. The results showed that: (1) there existed good relationship between the observed and simulated extreme precipitation indices during validation period of 1991–2000, the amount and the change pattern of extreme precipitation indices could be reasonably simulated by SDSM. (2) Under both scenarios A2 and B2, during the projection period of 2010–2099, the changes of annual mean extreme precipitation indices in the Yangtze River basin would be not obvious in 2020s; while slightly increase in the 2050s; and significant increase in the 2080s as compared to the mean values of the base period. The summer might be the more distinct season with more projected increase of each extreme precipitation indices than in other seasons. And (3) there would be distinctive spatial distribution differences for the change of annual mean extreme precipitation indices in the river basin, but the most of Yangtze River basin would be dominated by the increasing trend.  相似文献   

17.
The Weather Research and Forecast (WRF) model with its land surface model NOAH was set up and applied as regional climate model over Europe. It was forced with the latest ERA-interim reanalysis data from 1989 to 2008 and operated with 0.33° and 0.11° resolution. This study focuses on the verification of monthly and seasonal mean precipitation over Germany, where a high quality precipitation dataset of the German Weather Service is available. In particular, the precipitation is studied in the orographic terrain of southwestern Germany and the dry lowlands of northeastern Germany. In both regions precipitation data is very important for end users such as hydrologists and farmers. Both WRF simulations show a systematic positive precipitation bias not apparent in ERA-interim and an overestimation of wet day frequency. The downscaling experiment improved the annual cycle of the precipitation intensity, which is underestimated by ERA-interim. Normalized Taylor diagrams, i.e., those discarding the systematic bias by normalizing the quantities, demonstrate that downscaling with WRF provides a better spatial distribution than the ERA interim precipitation analyses in southwestern Germany and most of the whole of Germany but degrades the results for northeastern Germany. At the applied model resolution of 0.11°, WRF shows typical systematic errors of RCMs in orographic terrain such as the windward–lee effect. A convection permitting case study set up for summer 2007 improved the precipitation simulations with respect to the location of precipitation maxima in the mountainous regions and the spatial correlation of precipitation. This result indicates the high value of regional climate simulations on the convection-permitting scale.  相似文献   

18.
基于1992~2010年全国778个农业气象站土壤湿度观测资料、ERA-Interim、JRA55、NCEP-DOE R2和20CR土壤湿度再分析资料,通过平均差值、相关系数、差值标准差、标准差比四个参数,利用Brunke排名方法和EOF(Empirical Orthogonal Function)分析,对四套土壤湿度再分析资料在中国西北东部—华北—江淮区域的适用性进行了分析。主要结论如下:不同季节的平均偏差空间分布上,JRA55资料同观测数据的平均偏差在±0.08m~3 m~(-3)之间,春、夏季西北东部JRA55土壤湿度偏小,ERA-Interim、NCEP-DOE R2、20CR资料较观测数据偏湿,华北南部、江淮地区平均偏差小于西北东部、华北北部。在年际变化上,各个季节ERA-Interim资料同观测资料最为接近,能稳定地再现西北东部、华北、江淮地区土壤湿度干湿变化趋势,反映出重要的旱涝年。整体而言,四套再分析资料中ERA-Interim资料同观测资料接近,JRA55、NCEP-DOE R2资料次之,20CR资料最差。  相似文献   

19.
本文通过多套观测与再分析降水资料的比较,分析了雅鲁藏布江流域夏季降水的特征,从水汽含量与水汽输送的角度检验了雅鲁藏布江水汽通道的特点,研究了流域夏季降水的年际变化及其原因。分析表明:（1）该流域夏季降水大值位于雅鲁藏布江出海口至大峡谷一带,观测中流域平均降水可达5.8 mm d-1。不同资料表现的降水空间分布一致,但再分析降水普遍强于观测,平均为观测的2倍左右。（2）该流域夏季的水汽主要来自印度洋和孟加拉湾的偏南暖湿水汽输送,自孟加拉湾出海口沿布拉马普特拉河上溯至大峡谷,即雅鲁藏布江水汽通道。水汽收支诊断表明,夏季流域南部（即水汽通道所在处）是水汽辐合中心,流域平均的辐合约9.5 mm d-1,主要来自风场辐合与地形坡度的贡献。（3）不同再分析资料表现的流域降水和水汽分布特征总体一致,但量值差异较大。NCEP（美国国家环境预报中心）气候预报系统再分析资料CFSR、日本气象厅再分析资料JRA-25较欧洲中期天气预报中心再分析ERA-Interim资料更适于研究该流域（青藏高原东南部）的水汽特征,因为后者给出的流域降水和水汽偏强。（4）近30年该流域夏季降水无显著趋势,以年际变率为主。年际异常的水汽辐合（约为气候态的35.4%）源自异常西南风导致的局地水汽辐合（纬向、经向辐合分别贡献了16.5%、83.5%）,地形作用很小。流域夏季降水的年际变化是由印度夏季风活动导致的异常水汽输送造成的,其关键系统是印度季风区北部的异常气旋（反气旋）式水汽输送。  相似文献   

20.
采用哈密地区6站1975—2014年逐日地面水汽压和降水量资料,计算了哈密各站的大气可降水量、有效空中水资源量、自然降水产出率和人工增水潜力值,并分析了各量的时空分布特征。结果表明:哈密地区年平均整层大气可降水量为2560~4327 mm,年均有效空中水资源量约为232~828 mm,占整层大气可降水量的1/4~1/10;年均自然降水产出率在9%~28%,自然降水产出率与降水量成正比关系。哈密地区的年人工增水潜力理论计算值在844~2399 mm之间,潜力值在夏季最大,巴里坤和伊吾明显多于其它区域。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号