汉江流域1951-2003年降水气温时空变化趋势分析

利用1958-2017年长江中下游地区426个国家站逐日降水资料,通过线性趋势分析法、EOF分解法,使用五个降水特征量,分析了60 a来长江中下游地区降水的变化规律。结果表明：（1）长江中下游地区年降水量呈上升趋势,线性趋势为2.21 mm·a^-1,夏季的线性趋势为2.03 mm·a^-1,冬季雨量略增,而春、秋两季雨量略减;（2）年降水日数的线性趋势为-0.46 d·a1,春、秋、冬三季降水日数均有减少,夏季持平;（3）降水强度呈弱上升趋势,降水强度的高值中心在江西以东大部以及湖北东部、安徽南部边缘,夏季的降水强度最大,冬季的最小,四季的降水强度均有弱增加趋势;（4）降水变异系数的高值中心位于安徽西北部边缘,最高值为0.25,低值中心位于湖南西部,最低值为0.14;春季的降水变异系数最低,夏季整体稳定,秋冬两季的波动性较大;（5）以年降水量作为指标可以把长江中下游地区划分为三种空间分布型,即长江中下游流域区域一致型、长江中下游北部和南部南北反相变化空间型以及长江中下游东部和西部东西反相变化空间型。

     

CLM3模拟的1979-2003年中国土壤湿度及其对全球变暖的可能响应

利用NCAR公用陆面模式CLM3(Common Land Model 3),以1979—2003年NCEP/DOE再分析资料(Reanalysis-2)作为外界强迫,对在分辨率为0.5°纬度×0.5°经度下中国区域进行独立(off-line)模拟试验,并分析了土壤湿度对全球变暖的响应。模拟结果显示:土壤湿度随深度的增加调整(Spin-up)到稳态时间加长,最长可高达20年,这说明模式陆面过程对土壤初始状态的敏感性。模拟结果与台站实测资料及NCEP再分析资料输出的土壤湿度的对比表明,季节与年际变化及其空间分布基本一致。我们的结果还显示,随着近年来气候逐渐变暖,包括中国北方(30°N以北)在内的东亚北部地区夏季土壤湿度有逐渐减少趋势,最多减少15(mm3.mm-3).(100a)-1。     

A Variational Method for Estimating Near-Surface Soil Moisture and Surface Heat Fluxes

A variational data assimilation method is proposed to estimate the near-surface soil moisture and surface sensible and latent heat fluxes.The method merges the five parts into a cost function,i.e.,the differences of wind,potential temperature,anti specific humidity gradient between observations and those computed by the profile method,the difference of latent heat fluxes calculated using the ECMWF land surface evaporation scheme and the profile method,and a weak constraint for surface energy balance.By using an optimal algorithm,the best solutions are found.The method is tested with the data collected at Feixi Station (31.41°N,117.08°E) supported by the China Heavy Rain Experiment and Study (HeRES) during 7-30 June 2001.The results show that estimated near-surface soil moistures can quickly respond to rainfall,and their temporal variation is consistent with that of measurements of average soil moisture over 15-cm top depth with a maximum error less than 0.03 m~3 m~(-3).The surface heat fluxes calculated by this method are consistent with those by the Bowen ratio method,but at the same time it can overcome the instability problem occurring in the Bowen ratio method when the latter is about-1.Meanwhile,the variational method is more accurate than the profile method in terms of satisfying the surface energy balance.The sensitivity tests also show that the variational method is the most stable one among the three methods.     

用Palmer湿润指数作西北地区东部冬小麦旱涝评估

根据Palmer气象干旱指数 (PDSI) 的中间量Palmer湿润指数原理, 计算了西北地区东部冬小麦农气观测站延安、咸阳等多个站点1961—2000年逐月Palmer湿润指数, 对各站点的冬小麦不同发育期的旱涝情况做了初步的验证和应用。Palmer湿润指数与Z指数对比结果表明:Palmer湿润指数对农作物旱情分析更具有客观性, 分析结果更符合实际情况, 因而可以作为我国西北地区东部农作物旱涝的评估工具。     

A 10-Yr Global Land Surface Reanalysis Interim Dataset(CRA-Interim/Land):Implementation and Preliminary Evaluation

A land surface reanalysis dataset covering the most recent decades is able to provide temporally consistent initial conditions for weather and climate models, and thus is crucial to verifying/improving numerical weather/climate forecasts/predictions. In this paper, we report the development of a 10-yr China Meteorological Administration(CMA) global Land surface ReAnalysis Interim dataset(CRA-Interim/Land; 2007–2016, 6-h intervals, approximately 34-km horizontal resolution). The dataset was produced and evaluated by using the Global Land Data Assimilation System(GLDAS) and NCEP Climate Forecast System Reanalysis(CFSR) global land surface reanalysis datasets, as well as in situ observations in China. The results show that the global spatial patterns and monthly variations of the CRA-Interim/Land, GLDAS, and CFSR climatology are highly consistent, while the soil moisture and temperature values of the CRA-Interim/Land dataset are in between those of the GLDAS and CFSR datasets. Compared with ground observations in China, CRA-Interim/Land soil moisture is comparable to or better than that of GLDAS and CFSR datasets for the 0–10-cm soil layer and has higher correlations and slightly lower root mean square errors(RMSE) for the 10–40-cm soil layer. However, CRA-Interim/Land shows negative biases in 10–40-cm soil moisture in Northeast China and north of central China. For ground temperature and the soil temperature in different layers,CRA-Interim/Land behaves better than the CFSR, especially in East and central China. CRA-Interim/Land has added value over the land components of CRA-Interim due to the introduction of global precipitation observations and improved soil/vegetation parameters. Therefore, this dataset is potentially a critical supplement to the CRA-Interim.Further evaluation of the CRA-Interim/Land, assimilation of near-surface atmospheric forcing variables, and extension of the current dataset to 40 yr(1979–2018) are in progress.     

A 10-Yr Global Land Surface Reanalysis Interim Dataset (CRA-Interim/Land): Implementation and Preliminary Evaluation

A land surface reanalysis dataset covering the most recent decades is able to provide temporally consistent initial conditions for weather and climate models, and thus is crucial to verifying/improving numerical weather/climate forecasts/predictions. In this paper, we report the development of a 10-yr China Meteorological Administration (CMA) global Land surface ReAnalysis Interim dataset (CRA-Interim/Land; 2007–2016, 6-h intervals, approximately 34-km horizontal resolution). The dataset was produced and evaluated by using the Global Land Data Assimilation System (GLDAS) and NCEP Climate Forecast System Reanalysis (CFSR) global land surface reanalysis datasets, as well as in situ observations in China. The results show that the global spatial patterns and monthly variations of the CRA-Interim/Land, GLDAS, and CFSR climatology are highly consistent, while the soil moisture and temperature values of the CRA-Interim/Land dataset are in between those of the GLDAS and CFSR datasets. Compared with ground observations in China, CRA-Interim/Land soil moisture is comparable to or better than that of GLDAS and CFSR datasets for the 0-10-cm soil layer and has higher correlations and slightly lower root mean square errors (RMSE) for the 10-40-cm soil layer. However, CRA-Interim/Land shows negative biases in 10-40-cm soil moisture in Northeast China and north of central China. For ground temperature and the soil temperature in different layers, CRA-Interim/Land behaves better than the CFSR, especially in East and central China. CRA-Interim/Land has added value over the land components of CRA-Interim due to the introduction of global precipitation observations and improved soil/vegetation parameters. Therefore, this dataset is potentially a critical supplement to the CRA-Interim. Further evaluation of the CRA-Interim/Land, assimilation of near-surface atmospheric forcing variables, and extension of the current dataset to 40 yr (1979–2018) are in progress.     

全球变暖背景下中国近海表层海温变异及其与东亚季风的关系

利用长时间序列HadISST、ERA-40高分辨率的海洋大气再分析资料和经验正交函数(EOF)及回归分析等方法,分析了近50年来中国近海表层海温(SST)、东亚季风的时空变化特征及两者的关系.结果表明:中国近海冬、夏季SST有明显的年际和年代际变化,并均在1980年代中期发生了位相转折,之后呈现显著的上升趋势.其中,冬...     

7月南半球500hPa极涡异常的度量及其与极区增暖的联系

利用ECMWF月平均再分析资料,构造了500hPa7月南极极涡面积、强度指数。结果表明,定义的面积及强度指数为两个独立参数,通过分析南半球高纬度地区500hPa位势高度场EOF的主要模态以及典型年份的南极极涡差异,表明强度指数比面积指数更能代表极涡的强度变化。7月500hPa南极极涡强度指数与同期南半球高纬地表温度的变化趋势一致,下垫面的加热作用与南极极涡强度变化联系密切,在全球变暖背景下极涡面积收缩与热带扩张存在联系。     

Possible Effects of Global Warming on Agriculture and Water Resources in Saudi Arabia: Impacts and Responses

This study assesses the possible impact of climatic change on Saudi Arabia's agriculture and water supplies using climatic change scenarios from GCMs (General Circulation Models) and related research. The resulting assessment indicates that an increase in temperature and decrease in precipitation could have a major negative impact on agriculture and water supplies in Saudi Arabia. To find signs of climatic change in Saudi Arabia a preliminaryassessment of systematic changes in temperature and precipitation was made, based on the records of four Saudi weather stations. The analysis of this data, which dates back to 1961, shows no discernable signs of climatic change during the study period. Such data is, however, limited both spatially and temporally and cannot provide conclusive evidence to confirm climatic changes projected by GCMs. Nevertheless, in the light of recent climatic conditions and rapid population growth, Saudi decision-makers are urged to adopt a `no regret' policy. Ideally, such a policy would include measures to avoid future environmental or socioeconomic problems that may occur in the event of significant climatic change.     

干旱山区地堰不同保墒措施与树木生长的试验分析

通过高分子吸水剂、树盘盖石板、覆盖地膜、松土保墒四种不同贮水保墒措施的试验研究，探讨改善树木生长的生态条件、促进树木生长的方法，为解决干旱山区地堰造林绿化技术难题提供了有效措施。