Validation of the effects of temperature simulated by multi-model ensemble and prediction of mean temperature changes for the next three decades in China

Using series of daily average temperature observations over the period of 1961–1999 of 701 meteorological stations in China, and simulated results of 20 global climate models (such as BCCR_BCM2.0, CGCM3T47) during the same period as the observation, we validate and analyze the simulated results of the models by using three factor statistical method, achieve the results of multi- model ensemble, test and verify the results of multi-model ensemble by using the observation data during the period of 1991–1999. Finally, we analyze changes of the annual mean temperature result of multi-mode ensemble prediction for the period of 2011–2040 under the emission scenarios A2, A1B and B1. Analyzed results show that: (1) Global climate models can reproduce Chinese regional spatial distribution of annual mean temperature, especially in low latitudes and eastern China. (2) With the factor of the trend of annual mean temperature changes in reference period, there is an obvious bias between the model and the observation. (3) Testing the result of multi-model ensemble during the period of 1991–1999, we can simulate the trend of temperature increase. Compared to observation, the result of different weighing multi-model ensemble prediction is better than the same weighing ensemble. (4) For the period of 2011–2040, the growth of the annual mean temperature in China, which results from multi-mode ensemble prediction, is above 1 °C. In the spatial distribution of annual mean temperature, under the emission scenarios of A2, A1B and B1, the trend of growth in South China region is the smallest, the increment is less than or equals to 0.8 °C; the trends in the northwestern region and south of the Qinghai-Tibet Plateau are the largest, the increment is more than 1 °C.     

Impact of global warming on drought in China

Spatial and temporal change patterns of air temperature (T), precipitation (P), relative humidity (RH), lower vapor pressure (VP), potential evapotranspiration (PET) and drought situation of 690 meteorological stations for all of China were evaluated in this study to understand the effects of warming on regional drought and hydrological processes. Here, the drought extent is expressed by aridity index (AI), which is the ratio of precipitation and reference crop evapotranspiration (ET₀) calculated by FAO Penman-Monteith equation, taking into account air temperature, atmospheric humidity, solar radiation, and wind. Our results indicate that there are different patterns of climate change from 1961 to 2008 and from 1981 to 2008. Little precipitation change occurred in China and ET₀ decreased from 1961 to 2008. But, the warming trend has intensified and the area with significant increasing precipitation has reduced since the early 1980’s and ET₀ has increased in most areas of China from 1981 to 2008 and decreased from 1961 to 2008. The areas affected by drought have shifted from North China and Northeast China to East China and South China since 1981. It is speculated that the increasing warming intensity after 1981 possibly strengthened the power of potential evapotranspiration and resulted in drought in most areas of Northeast China, North China, eastern Southwest China, and especially in East China and South China.     

珠江三角洲交通通达性空间格局与人口变化关系

基于1988年、1998年、2008年陆路交通网络数据,借助GIS软件,分析了1980年代以来珠三角地区交通网络通达性空间格局的变化,并采用GAM模型,定量分析了1980～2009年期间陆路交通网络与人口变化之间的关系。结果表明:研究时段内,公路交通通达性空间格局以穗-莞-深一线为最高,向外围逐渐递减;铁路交通通达性空间格局以广佛地区为中心向外围逐渐递减;陆路交通网络发展主要受公路网络的影响,铁路在整个交通网络中所起的作用较弱;各阶段通达性提高幅度差异较大,存在递减效应,第一阶段(1988～1998年)通达性提高较第二阶段(1998～2008年)更为显著;公路交通、铁路交通与人口变化关系具有差异性,公路交通对人口变化的作用显著,三个时段内其对人口变化的解释贡献率分别为11.56%、48.07%、44.92%,铁路与人口变化的关系较为薄弱,但在1990年以后,随着铁路网络扩展以及铁路运输服务水平的提高,其与人口变化的关系逐步增强。     

粗糙元几何参数的交互作用对床面空气动力学粗糙度的影响

 为了全面地揭示粗糙元的所有几何参数的交互作用对空气动力学粗糙度的影响,利用风洞实验研究了粗糙元高度、密度、高度与间距比、孔隙度和方向比率等几何参数交互作用对空气动力学粗糙度的影响。结果表明,密实和孔隙粗糙元的无量纲空气动力学粗糙度（空气动力学粗糙度度/粗糙元高度）均可表示为粗糙元密度/等效密度的正比例函数,而比例系数反映了粗糙元几何参数交互作用。据此,该研究发展了一个全面反映粗糙元高度h、密度/等效密度λ、高度与行间距比Sp和方向比率AR等几何参数交互作用的空气动力学粗糙度模式:Z0h=-0.0028+0.5403S0.32p·AR-0.07·λ。该模式改进了模拟的精度,扩大了适用范围。     

中国城市场强格局演化及空间自相关特征

将城市场强与空间自相关结合起来,研究中国661个城市辐射场强和城市间的互动关联强度。从场强看,北京、上海、广州等超大城市辐射作用增长迅速,已形成全国性的辐射圈层结构;围绕沿海特大城市及武汉、郑州、重庆、成都等中西部的区域中心城市,已具备孵化若干区域级城市群的城市化土壤;在地区尺度范围,全国大量地区性中心城市所形成的辐射场强,则培育了都市区发育的城市化土壤。从互动关联强度看,沿海地区城市间相互作用和互动关联性明显高于内陆地区,不仅促进了珠三角、长三角、环渤海等超级城市群的日趋成熟,而且推动辽中南、山东半岛等次级城市群发展壮大。然而,内陆地区大部分城市目前还处于相对孤立发展状态,城市间互动关联性较弱,城市群发育潜力尚未得到真正激发。     

Assessment of CMIP3 climate models and projected changes of precipitation and temperature in the Yangtze River Basin, China

The projected changes of precipitation and temperature in the Yangtze River Basin in the 20th Century from 20 models of the CMIP3 (phase 3 of the Coupled Model Inter-comparison Project) dataset are analyzed based on the observed precipitation and temperature data of 147 meteorological stations in the Yangtze River Basin. The results show that all models tend to underestimate the annual mean temperature over the Yangtze River Basin, and to overestimate the annual mean precipitation. The temporal changes of simulated annual mean precipitation and temperature are broadly comparable with the observations, but with large variability among the results of the models. Most of the models can reproduce maximum precipitation during the monsoon season, while all models tend to underestimate the mean temperature of each month over the Yangtze River Basin. The Taylor diagram shows that the differences between modeled and observed temperature are relatively smaller as compared to differences in precipitation. For a detailed investigation of regional characteristics of climate change in the Yangtze River Basin during 2011–2050, the multi-model ensembles produced by an upgraded REA method are carried out for more reliable projections. The projected precipitation and temperature show large spatial variability in the Yangtze River Basin. Mean precipitation will increase under the A1B and B1 scenarios and decrease under the A2 scenario, with linear trends ranging from ?21 to 28.5?mm/decade. Increasing mean temperature can be found in all scenarios with linear trends ranging from 0.15 to 0.48°C/decade. Grids in the head region of the Jingshajiang catchment show distinct increasing trends for all scenarios. Some physical processes associated with precipitation are not well represented in the models.     

CINRAD/SA雷达两种识别跟踪产品的评估分析

以中国气象局气象探测中心提供的2007--2008年灾害性天气个例档案为基础,对CINRAD／SA雷达风暴识别跟踪和中气旋产品做了定量评估,同时就评估结果与美国同类产品做了对比。结果表明,风暴识别与跟踪产品基本能满足临近预报的需要,但存在漏识别和错误跟踪现象,且30min以后单体位置预报误差较大。中气旋产品评估结果与美国产品差异不大,基本能自动识别风暴涡旋,但存在漏报,且虚警率较高。     

对流涡度矢量垂直分量在西南涡暴雨中的应用

将对流涡度矢量 (CVV) 应用于浅薄系统西南低涡引发的暴雨中,特别是将对流涡度矢量垂直分量 (C_z) 应用在2010年7月16—18日由西南涡引发的一次暴雨过程诊断中。研究了CVV垂直积分的各个分量与6 h累积降水量的关系,尤其是CVV垂直分量在西南涡暴雨过程中的指示意义。诊断结果表明:CVV垂直分量与西南涡引发的暴雨有一定对应关系,强降水发生时段与C_z垂直积分峰值出现的时间对应一致;在对流层低层850 hPa水平分布上,暴雨区位于CVV垂直分量的正值中心附近,偏向其梯度较大处;沿暴雨中心的CVV垂直分量,当对流层低层至高层呈现一致的正值时,暴雨强度会明显加强。     

INTERDECADAL TRANSITIONS AND TWO EXCEPTIONAL YEARS OF JUNE PRECIPITATION OVER SOUTH CHINA

An analysis of high-resolution precipitation data for 1978-2006 indicates that the precipitation over southern China in June experienced a low-value period in 1980-1989 and a high-value period in 1992-2001.It also reveals that exceptional heavy(light) precipitation occurred in June 2005(2004) since 1951.For these variations on both interdecadal and interannual timescales,fairly uniform anomalies of precipitation appeared over Vietnam,southern China,and southeastern China.Corresponding to positive(negative) precipitation anomalies,anomalous southeasterly(northwesterly) flow at 850 hPa reached Vietnam and anomalous southwesterly(northeasterly) flow expanded to the coastal regions of southern and southeastern China.Precedent to the positive(negative) precipitation anomalies during 1992-2001(1980-1989),positive(negative) anomalies of sea surface temperature appeared over the extratropical northwestern Pacific in the winter and spring seasons,associated with a strong(weak) extension of the warm Kuroshio Current that affects the coastal region of eastern China.The above-normal precipitation in June 2005 was associated with the pseudo-ENSO event in the previous winter,and the below-normal precipitation in June 2004 was associated with negative anomalies of sea surface temperature over the equatorial central Pacific and positive anomalies over the equatorial western and eastern Pacific.     

基于SPOT 5图像的岩溶地貌单元自动提取方法

通过对峰林、峰丛和岩溶洼地3者的地理特征和影像特征的研究,基于遥感图像本底值提出了能有效反映目标特征的遥感指数——植被指数、土壤亮度指数、图像主成分变换第1主成分值及地形数据等,并构建了遥感指数的集成计算法,建立了遥感自动提取模型.指数集成运算法能够有效地增大峰丛、峰林与其他地物之间的光谱差异,使这些岩溶地貌单元的灰度值高于其他地物,从而利于岩溶地貌单元提取阈值的自动选取.基于构建的遥感自动提取模型先提取了峰丛、峰林信息,并在此基础上提取了岩溶洼地信息.经实验研究表明,该方法具有较高的提取精度和效率.