一种新的气候突变分析方法及其在西北地区东部的应用

本文在探讨目前气候突变方法的基础上，针对其存在的缺陷，引入费希尔（Ｆｉｓｈｅｒ）最优分割法，并把它和原方法的统计检验结合起来，得到一种新的研究气候突变的方法。运用它对西北地区东部的西安、宝鸡、汉中三地的旱涝等级序列进行气候突变研究，可知西北地区东部旱涝气候突变存在局地性和非局地性的特征。     

历史上10~1～10~2年尺度气候跃变的分析

利用史料重建了华北海河流域和陕西关中地区两千多年来的旱涝变化概况。采用移动符号检验法和移动T检验法分析了其中的几十和几百年尺度的跃变现象。通过比较海河、关中以及河南等地区的同期变化,区分出局地性和非局地性两类跃变事件;并通过个例分析指出了华北地区气候跃变和季风环流形势的可能联系。本文还对10~1～10~2年尺度气候跃变的发生频率和变化程度作了一般估计。     

历史上10年—100年尺度气候跃变的分析

利用史料重建了华北海河流域和陕西关中地区两千多年来的旱涝变化概况.采用移动符号检验法和移动T检验法分析了其中的几十和几百年尺度的跃变现象.通过比较海河、关中以及河南等地区的同期变化,区分出局地性和非局地性两类跃变事件;并通过个例分析指出了华北地区气候跃变和季风环流形势的可能联系.本文还对10~1—10~2年尺度气候跃变的发生频率和变化程度作了一般估计.     

西北地区东部旱涝气候特征

利用中国气象科学研究院收集、整理的西北地区东部代表站1470~2003年的旱涝等级资料,根据不同的地形地貌特征和气候特征,将西北地区东部分为3个气候区,利用周期分析、coif3小波变换等统计分析方法对3个气候区534年旱涝指数的年代际气候特征及地域之间旱涝变化的差异进行分析。结果表明,西北地区东部不同区域旱涝的时空分布特征不尽相同,旱涝演变趋势、旱涝周期变化既有一致性,也存在明显的差异。534年以来北部、中部由偏旱趋于正常或偏涝,南部1724年以前的变化趋势由偏旱趋于偏涝,1724年以后由偏涝趋于偏旱;3个气候区都存在25年和10年的显著周期,其中中部还存在14~15年的显著周期,说明中部旱涝交替较北部和南部明显。     

新书架

《中国西北地区东部汛期降水异常成因及预测研究》该书系统介绍了西北地区东部汛期降水异常大气环流特征、持续性旱涝和旱涝急转环流特征,海温、北亚洲地面感热、青藏高原热状况、北半球高纬度海洋热状况对西北地区东部降水影响与机理,及其预测方法、模型和预测系统等方面的最新研究成果。该书是一本资料翔实,结构严谨,内容丰富全面,阐述简明及理论性、针对性和实用性强的专著,具有较高的学术价值,对气候预测业务服务有重要的指导作用,可供气象、地理、环境、生态.     

我国西北地区春季旱涝气候特征研究

利用西北地区160个台站1950～2000年春季降水量资料,讨论了西北5个区域的旱涝气候特征,发现西北东部和北疆山前地带降水气候变化最为激烈,旱涝事件频繁.整个西北地区春季干旱虽较雨涝多见,但严重雨涝的发生多于严重干旱,且严重旱涝的发生自20世纪80年代以来有增加的趋势.西北各区的旱涝演变具有阶段性和群发性的特点,存在年代际的变化周期和5～6年的准周期振荡.西北东部春季严重雨涝和严重干旱发生时,中高纬度大尺度环流及副热带大气环流特征迥然不同,且分别对赤道中东太平洋海温和北太平洋西风漂流区海温异常表现出遥响应的关系.     

我国西北地区近50年降水和温度的变化

用近50年的每月温度和降水资料研究了我国西北地区的气候变化.结果表明:(1)该地区在1986年附近发生了一次明显的气候跃变,要比全国气候跃变晚6～8年;(2)跃变后比跃变前全区年平均气温上升了0.51℃,冬季上升了1.27℃;(3)跃变后比跃变前全区年降水总量上升了5.2%,夏季上升了6.8%.进而讨论了温度和降水的增加对该地区生态环境的影响.     

北太平洋海温的气候跃度及其对中国汛期降水的影响

应用滑动Ｔ检验方法对北太平洋海温１０年际的气候跃变进行了研究，指出在７０年代末至８０年代初确实存在着一次明显的气候跃变，而跃变前后北太产洋海温结构，厄尔尼诺事件的发展过程都明显不同，进而讨论了北太平洋海温跃变前后对我国６－８月汛期降水量的影响，指出海温跃变前我国汛期降水量在东北地区偏少，华北偏多，长江流域偏水，华南偏多，而跃变后则相反。     

中国西北地区东部近546年干旱事件特征分析

以西北地区东部的17个代表站1470—2008年的旱涝等级资料和1958—2015年5—9月气象站降水量数据为基础，建立了546年中国西北地区东部旱涝等级序列，采用经验正交函数分解、滑动t检验等统计方法，对其干湿演变规律进行分析，详细讨论了546年极端干旱事件及干旱持续性特征。结果表明:旱涝等级资料能够较好地反映西北地区东部干旱变化的时、空特征；在百年尺度上，20世纪发生旱、偏旱最为频繁，且高值区位于宁夏及陕北；干旱尺度因子的空间分布表明宁夏东部及陕北地区的干旱持续性相对较强，陇南及陕西南部地区的干旱持续性较差；空间范围较大且强度较大的重大干旱事件对干旱的持续发生起重要作用，历史上发生在1470—1500年和1910—1940年的两次西北地区东部百年甚至两百年一遇的极端干旱事件，对该地区干旱持续性的影响较为显著。      

《中国西北地区东部汛期降水异常成因及预测研究》

正该书系统介绍了西北地区东部汛期降水异常大气环流特征、持续性旱涝和旱涝急转环流特征,海温、北亚洲地面感热、青藏高原热状况、北半球高纬度海洋热状况对西北地区东部降水影响与机理,及其预测方法、模型和预测系统等方面的最新研究成果。该书是一本资料翔实,结构严谨,内容丰富全面,阐述简明及理论性、针对性和实用性强的专著,具有较高的学术价值,对气候预测业务服务有重要的指导作用,可供气象、地理、环境、生态、     

Analysis of temperature series in Europe in relation to the detection of the enhanced greenhouse effect

Summary A method is developed for analysing climate series. It is based on the assumption that climate undergoes abrupt changes by natural means. It is a generalization of an existing method for dividing a series into two parts. It is assumed that increasing concentrations of greenhouse gases will lead to a gradual climate change (trend) and that this change will be superimposed upon the natural abrupt changes (jumps). On the basis of these facts, jumps in the direction of a climate change resulting from the increased concentrations of greenhouse gases are expected to be stronger than those in the opposite direction and previous jumps in the same direction. Different criteria are used to support this assumption. The method of analysis is applied to time series of summer and winter temperatures of 13 European stations.The largest increases in temperature do not occur in the recent past; they occur around 1910 in winter and about 1930 in summer. As the test for detection of the enhanced greenhouse effect is made stricter, the assumption put forward becomes weaker. Most time series do not have significant trends within various sub-periods. Differences in variability between successive sub-periods are generally not significant. There is agreement between the results reported here and others in the literature. So far, there is no definite evidence that the increasing concentration of greenhouse gases is affecting the climate of Europe.With 6 Figures     

气候变化与气候层次结构初探

应用相空间经验正交展开方法，分析了四川降水、温度局地气候变化的主要特征及与其层次结构的关系。结果表明：气候作为一个多层次复杂系统，其变化表现出明显的层次结构特征，气候突变多反映在较高层次结构上，非突变变化多属于较低层次结构；高层次决定了气候变化的基本形态，低层次存在反馈作用；正（负）反馈作用可加强（减弱）气候变化的突变性；气候突变的强度和时问具有一定的层次结构差异性。     

The response of climatic jump in summer in north china to global warming

To reveal climatic variation over North China, the climatic jumps in summer in Beijing are analyzed using the data of precipitation of summer (June, July, August) during the period of 1841-1993, in which those missed before 1950 were reconstructed by the stepwise regression method with minimum forecast error. The climatic jumps at different scales are analyzed using different diagnostic methods with different decade (10-100 years) windows. Some new methods and ideas are proposed. The variance difference, the linear tendency difference, and the difference of power spectral distribution between the samples before and after the period at the moving point in the center of the series are compared with other methods (for example, Mann-Kendall test, t-test, and accumulative anomaly etc.). Considering the differences among the statistics above, a synthetic jump index is also proposed in order to get the definite jump points in the moving series. The results show that the climatic jumps in the area occurred in the 1890’s, the 1910s and the 1920s, and mostly in the 1920s, which suggests that the local climatic jumps in North China have a simultaneous response to the global warming in the hundred-year scales.     

THE THREE-LEVEL GLOBAL ATMOSPHERIC GENERAL CIRCULATION MODEL: FORMULATION AND RESULTS

The "climate draft" often occurs in the coupling process of the atmospheric general circulation model (AGCM) and oceanic general circulation model (OGCM).One of the main methods to overcome the "climate draft" is to simulate the flow and temperature fields in the low-layer correctly.Therefore we designed a three-level AGCM including a planetary boundary layer (PBL) and have run it seven model years to do climate simulation.The results show that the simulated lower level air flow,surface air temperature and sea-level pressure in January and July,approximate to the climate average fields,especially in Asian monsoon area.The simulated upper level flow and geopotential height are also in better agreement with the observed fields.Moreover,the two westerly jets over the northern and southern sides of the Qinghai-Xizang Plateau in winter,the disappearance of its southern subtropical jet during the seasonal transition from spring to summer,the establishment of the two easterly jets near the equator and over the subtropical region during the seasonal transition,are also simulated well.In the mainland of China,the seasonal abrupt shift of the rainfall belt,such as the Meiyu belt in South China during April to May,which jumps to the Changjiang River region in June,again jumps back to the north China in July,and rapidly withdraws to the south in August,are simulated very well.Now we are coupling this model to a global six-level OGCM and nesting a fine mesh (1°×1.25°)regional climate model over China area with it.     

东北地区近百年气候变化及突变检测

利用沈阳、大连、营口、长春、哈尔滨、黑河6个代表站1905~2001年的月平均气温和月降水观测数据,建立了东北地区近百年来季、年的气温和降水序列。对所建温度和降水序列分别与同一区域内26个代表站的温度序列和51个代表站的降水序列近40年同期资料做了相关分析,检验了序列的代表性。在所建序列的基础上,分析了东北地区百年气温的年代、年和季节等不同时间尺度的变化特点和地域分布特征,以及百年降水量的变化规律,采用谱分析方法探讨了序列的周期性变化特征,并采用Mann-Kendall和Yamamoto方法对经过滑动平均的气温和降水序列进行了突变分析。     

A comparison of explicit and implicit spatial downscaling of GCM output for soil erosion and crop production assessments

Spatial downscaling of climate change scenarios can be a significant source of uncertainty in simulating climatic impacts on soil erosion, hydrology, and crop production. The objective of this study is to compare responses of simulated soil erosion, surface hydrology, and wheat and maize yields to two (implicit and explicit) spatial downscaling methods used to downscale the A2a, B2a, and GGa1 climate change scenarios projected by the Hadley Centre’s global climate model (HadCM3). The explicit method, in contrast to the implicit method, explicitly considers spatial differences of climate scenarios and variability during downscaling. Monthly projections of precipitation and temperature during 1950–2039 were used in the implicit and explicit spatial downscaling. A stochastic weather generator (CLIGEN) was then used to disaggregate monthly values to daily weather series following the spatial downscaling. The Water Erosion Prediction Project (WEPP) model was run for a wheat–wheat–maize rotation under conventional tillage at the 8.7 and 17.6% slopes in southern Loess Plateau of China. Both explicit and implicit methods projected general increases in annual precipitation and temperature during 2010–2039 at the Changwu station. However, relative climate changes downscaled by the explicit method, as compared to the implicit method, appeared more dynamic or variable. Consequently, the responses to climate change, simulated with the explicit method, seemed more dynamic and sensitive. For a 1% increase in precipitation, percent increases in average annual runoff (soil loss) were 3–6 (4–10) times greater with the explicit method than those with the implicit method. Differences in grain yield were also found between the two methods. These contrasting results between the two methods indicate that spatial downscaling of climate change scenarios can be a significant source of uncertainty, and further underscore the importance of proper spatial treatments of climate change scenarios, and especially climate variability, prior to impact simulation. The implicit method, which applies aggregated climate changes at the GCM grid scale directly to a target station, is more appropriate for simulating a first-order regional response of nature resources to climate change. But for the site-specific impact assessments, especially for entities that are heavily influenced by local conditions such as soil loss and crop yield, the explicit method must be used.     

The Temporal Climatic Variability in the ‘Río De La Plata’ Basin Displayed by the River Discharges

Streamflows have a direct dependence on precipitation and these are directly linked to the climate. Then, in this paper the temporal climatic variability in the Río de la Plata Basin is analysed through the changes in the river's discharges. These are the reflection of the climatic inputs areally integrated, and in consequence, contain more information on climate variability than that provided by the scarce punctual records of precipitation and temperature. The time series of streamflows correspond to monthly and annual means in stations selected in the basin for the period 1931–1992. However, in the present paper, the period 1901–1992 was considered in all cases whenever possible. The following changes and tendencies in the flow series were detected: 1. An important change of tendency between 1970 and 1972, and another not so significant before that date were detected in 1917–1918 and 1943–1944. 2. The jumps in the means in several sub-periods were detected using different methods. They showed jumps mainly in the period 1970–1972 in the annual streamflows series. The jumps in the annual streamflow series consist of an abrupt change in climatic variables affecting temporarily the averages of such variables during a certain period of time (years). The results are consistent with the conclusions obtained by other authors for the same region, both in precipitation and in the general circulation of the atmosphere. Keeping in mind this analysis of the series of streamflows, indicators of normal variability of tendencies relative to natural regional causes were detected, although the local causes were not anthropogenically analysed, and so no other manifestations of randomless in the zone of the Basin under study because of the lacking of data.     

时间序列转折突变点检测的线性函数方法

根据转折突变的定义，在引入线性半截多项式的前提下，提出检测时间序列转折突变点的一种新方法。此方法不仅能找出时间序列中存在的多个转折突变点，而且使得检测到的突变点通过统计显著性检验。应用此方法对北半球1851—1990年年平均气温距平及其11年滑动平均序列，1901—1999年昆明5月降水及其11年滑动平均的降水序列分别进行了检测。发现北半球年平均气温距平在1879、1889、1939和1973年附近出现了年际转折突变，在1878、1888和1941年以及1972年出现了年代际尺度的转折突变；昆明5月雨量不存在年际转折突变点，但昆明5月雨量在1918、1966以及1978年附近出现了年代际尺度转折突变。     

Comparing precipitation bias correction methods for high-resolution regional climate simulations using COSMO-CLM

A new parametric bias correction method for precipitation with an extension for extreme values is compared to an empirical and an existing parametric method. The bias corrections are applied to the regional climate model COSMO-CLM (consortium for small-scale modelling – climate limited area modelling) with a resolution of 4.5 km for the time periods 1991–2000 and 2091–2100. In addition to a comparison in a cross-validation framework, a focus is laid on the investigation of extreme value correction and the effect of the bias correction on the climate change signal. According to the statistical methods used in this study, it was found that the empirical method outperforms both parametric alternatives. However, due to the limited length of the available time series, some outliers occurred, and all methods had problems correcting extreme values. The climate change signal is moderately influenced by all three methods, and the power of climate change detection is reduced. The largest effect was found for the number of dry days and the mean daily intensity, which are considerably altered after correction.     

Evaluation of delta change and bias correction methods for future daily precipitation: intermodel cross-validation using ENSEMBLES simulations

Due to inherent limitations in climate models, their output is biased in relation to observed climate and as such does not provide reliable climate projections. In this study, nine methods used to account for biases in daily precipitation are tested. First, cross-validation tests were made using a set of ENSEMBLES regional model simulations to gain insights in the potential performance of the methods in the future climate. The results show that quantile mapping type methods, being able to modify the shape of the precipitation distribution, often outperform other types of methods. Yet, as the performance depends on time of the year, location and part of the distribution considered, it is not possible to distinguish one universally best performing method. In addition, the improvement relative to the projections that would have been obtained assuming unchanged climate is relatively modest, particularly in the early twentyfirst century conditions. Further tests with different method combinations show that the projections could be potentially improved by using several well performing methods in parallel. In the second part of the study, contributions of method and model differences to the overall variation of precipitation projections are assessed. It is shown that although intermodel differences play an important role, uncertainties related to intermethod differences are substantial, particularly in the tails of the distribution. This suggests that method uncertainty should be taken into account when constructing daily precipitation projections, possibly by using several methods in parallel.