全球地面降水月值历史数据集研制

全球降水历史数据是开展气候、水循环等研究的基础。收集整理全球12个数据源降水历史月值资料,通过站号、站名甄别不同数据源中相同台站,对344个通过相关系数、一致率、均值t检验、方差F检验的台站多源资料进行拼接,尽可能多地融合各套数据产品优势,最终形成全球降水历史月值数据集(CMA Global PrecipitationV1.0, CGP)。数据集重点解决当前国际数据产品在东亚地区站点稀少、同时应用多套数据应用门槛较高等问题。数据集收录3.1万个台站共计1.87×107组月降水记录, 4152个台站序列长度达百年。与美国大气海洋局(NOAA)的全球降水数据集(GHCN-M V2.0)对比,CGP新增1万个站点、0.5×107组有效观测记录和1030条百年序列,其中141条百年序列通过多源整合技术获取。CGP的站点和数据量优势主要体现在东亚、东欧、西伯利亚等站点稀疏地区。基于CGP分析的全球降水时空特征与国际同类产品的结果较一致。新增的数据虽然没有改变全球降水分布的总体特征,但对区域性的百年降水变化检测有一定影响。基于CGP的全球降水百年序列结果显示,20世纪前半叶全球降水量偏小,近20年是1900年以来全球降水量最大的时期,各纬度带、各个国家或地区的降水长期变化趋势呈现显著的差异。      

The QBO signal in monthly precipitation fields over Europe

Summary Areal monthly precipitation totals of 24 West and Central European regions and of 74 regions of the European part of the former USSR are studied in respect to the westerly and easterly phases of the QBO for the longest available period from 1953 to the 1980s. A significant QBO signal has been detected in September and October in the region of the British Isles, in the Central European region and in Byelorussia (in the easterly phase more precipitation and its lower variability in September and higher variability in October), but also in small region of the south Ukraine in August and in October. Regions of the eastern Ukraine and adjoined regions of Russia had the significant QBO signal in May (more precipitation and its prevalent lower variability in the westerly phase). The observed effects are explained by circulation differences in the westerly and easterly phases of the QBO.With 2 Figures     

Estimation of the monthly and annual mean maximum and mean minimum air temperature values in Greece

In this study, regression equations to estimate the monthly and annual values of the mean maximum and mean minimum air temperatures in Greece are derived. For this purpose, data from 87 meteorological stations distributed all over Greece are used. Geographical parameters, i.e., altitude, latitude, longitude, minimum distance from the sea and an index of terrain morphology, are used as independent variables. These equations explain 79?C97% of the variance of the temperature values and have standard error of estimate between 0.59 and 1.20°C. Data from 37 other meteorological stations are used to validate the accuracy of the equations. Topographic or climatic factors, which could not be introduced into the equations, are responsible for most temperature residuals >0.5°C or <?0.5°C. Moreover, some particular emphasis has been given to the values of the regression coefficient for the altitude, since it is the estimator for the mean lapse rate of air temperature.     

Intraannual dissimilarities between monthly mean Northern Hemisphere temperature anomalies during the twentieth century

Summary Northern Hemisphere monthly mean temperature anomalies during the twentieth century exhibit seasonal differences. To expose the most significant intermonthly dissimilarities, here we investigate this issue in more details. We show that the trends significantly differ for the months close to the equinoxes. Using the technique of multidimensional scaling analysis we find that two underlying attributes are sufficient to acceptably describe the structure of the observed intermonthly dissimilarities. Namely, these are the monthly sample percentiles around the 30th and the 70th together with the linear trends. We find that intraannual temperature anomaly dissimilarities statistically depend on the seasonal cycles of the Northern Hemisphere oceanic heat content, sea ice and snow cover and the Arctic sea ice cover as well as on the seasonality of the chaoticity of the Northern Hemisphere atmospheric dynamics. We also speculate that the annual cycles of these ocean and cryosphere characteristics statistically set the pattern for the observed course of linear warming over the calendar months.     

Mapping the mean monthly precipitation of a small island using kriging with external drifts

This study focuses on the spatial distribution of mean annual and monthly precipitation in a small island (1128 km²) named Martinique, located in the Lesser Antilles. Only 35 meteorological stations are available on the territory, which has a complex topography. With a digital elevation model (DEM), 17 covariates that are likely to explain precipitation were built. Several interpolation methods, such as regression-kriging (????????, ????????, and ????????) and external drift kriging (??????) were tested using a cross-validation procedure. For the regression methods, predictors were chosen by established techniques whereas a new approach is proposed to select external drifts in a kriging which is based on a stepwise model selection by the Akaike Information Criterion (AIC). The prediction accuracy was assessed at validation sites with three different skill scores. Results show that using methods with no predictors such as inverse distance weighting (??????) or universal kriging (????) is inappropriate in such a territory. ?????? appears to outperform regression methods for any criteria, and selecting predictors by our approach improves the prediction of mean annual precipitation compared to kriging with only elevation as drift. Finally, the predicting performance was also studied by varying the size of the training set leading to less conclusive results for ?????? and its performance. Nevertheless, the proposed method seems to be a good way to improve the mapping of climatic variables in a small island.     

Modeling monthly mean air temperature for Brazil

Air temperature is one of the main weather variables influencing agriculture around the world. Its availability, however, is a concern, mainly in Brazil where the weather stations are more concentrated on the coastal regions of the country. Therefore, the present study had as an objective to develop models for estimating monthly and annual mean air temperature for the Brazilian territory using multiple regression and geographic information system techniques. Temperature data from 2,400 stations distributed across the Brazilian territory were used, 1,800 to develop the equations and 600 for validating them, as well as their geographical coordinates and altitude as independent variables for the models. A total of 39 models were developed, relating the dependent variables maximum, mean, and minimum air temperatures (monthly and annual) to the independent variables latitude, longitude, altitude, and their combinations. All regression models were statistically significant (α?≤?0.01). The monthly and annual temperature models presented determination coefficients between 0.54 and 0.96. We obtained an overall spatial correlation higher than 0.9 between the models proposed and the 16 major models already published for some Brazilian regions, considering a total of 3.67?×?10⁸?pixels evaluated. Our national temperature models are recommended to predict air temperature in all Brazilian territories.     

由卫星辐射测量资料计算候、旬和月平均海面温度场

本文介绍了一个从NOAA卫星AVHRR红外窗区通道辐射测量资料获取候、旬和月平均海面温度场的计算机软件系统,并提供了用1987年6月的NOAA-9卫星AVHRR资料,对软件系统进行测试得到的旬和月平均海面温度场。     

Structural characteristics of annual precipitation in Lake Urmia basin

Theoretical and Applied Climatology - Precipitation as the main process that brings evaporated water from the oceans to the land’s surface is a critical role player in Lake Urmia basin...     

A simple method of computing the variation of annual precipitation over mountainous terrain

A method for computing the distribution of annual precipitation for mountainous areas is presented. As a pilot study, the South Thompson River basin in British Columbia is examined. In addition to data from climatological (valley) stations, annual precipitation is estimated for snow course (mountain) locations from the water equivalent of the snowpack on April 1.An equation for the dependence of precipitation amount on orography is derived from simple physical considerations. Regression equations based on this are then computed and the calculated precipitation is checked with runoff data. A basic predictor is the mean vertical water vapor transport through a horizontal unit area due to flow over undulating terrain. This depends on the average slope of a region 3 deg long by 2 deg lat centered on each grid point. The transport at the earth's surface has a simple correlation coefficient with the combined valley and mountain precipitation data of 0.76. When the transport is computed at the mean cloud base (taken as 1800 m above sea-level), the correlation coefficient rises to 0.87.     

冬季各月北太平洋涛动的年际变化及其与我国降水异常的联系

利用ERA-Interim的海平面气压(Sea Level Pressure,SLP)再分析资料和中国160站的降水观测资料,分析了冬季各月(当年12月、次年1月和2月)北太平洋涛动(North Pacific Oscillation,NPO)的年际变化特征,及其与我国同期降水异常之间的联系。结果表明:1)冬季各月NPO指数的年际变化较为显著,但各月NPO指数年际变化之间的相关性较差,1979—2012年冬季12月与1月NPO指数年际变化之间的相关系数为0.09,而1月与2月NPO指数的相关系数仅为-0.003,均没有通过信度检验。2)1月和12月NPO指数年际变化与同期我国黄淮流域降水异常之间存在明显的正相关,而2月NPO指数年际变化与同期我国华北降水异常之间为明显的负相关。3)当1月(12月)NPO指数增加1个标准差时,我国黄淮流域降水量比多年平均值增加约50%(40%);而当2月NPO指数增加1个标准差时,我国华北降水量比多年平均值减少约30%。     

近30a来北半球对流层大气月均环流的涡动减弱现象

利用1980-2009年NCEP／NCAR月平均再分析资料,研究了在全球变暖背景下北半球对流层大气涡动减弱现象。结果表明：北半球涡度拟能30a来整体呈减弱趋势,在北太平洋地区和极地减弱尤为显著,12．5～50°N为影响北半球大气涡动变化的关键区域。由于对流层200hPa以下大气的增暖,特别是中高纬地区显著增暖,减弱了经向温度梯度,使得副热带西风急流的强度亦呈减弱趋势。这与涡度拟能的变化有显著的正相关关系。分析了北半球正压Rossby波动诊断量E和热量经向涡动通量的变化,表明中纬度波能传播在不同地区有不同趋势,而热量的经向涡动输送与涡度拟能的变化也呈现显著的正相关关系,减弱明显。研究结果对深刻认识大气环流变化规律和理解全球变暖的可能影响具有重要意义。