全球变暖背景下青藏高原夏季气温在对流层上下反相变化及其与降水和环流的关系

本文利用NCEP/NCAR月平均再分析资料及中国596个测站月降水资料,采用线性倾向估计、经验正交函数分解(EOF)、相关分析、合成分析等方法,对青藏高原夏季对流层气温垂直变化及其与降水和环流的关系进行了分析。气温垂直变化特征分析表明:自1971年以来,青藏高原夏季对流层低层至对流层中上部气温呈现显著增暖趋势,对流层上部气温呈现显著变冷趋势,高原对流层低层至中上部气温及对流层上部气温在年际、年代际尺度上均呈较显著负相关,且均存在2~4 a及8~13 a的周期;夏季青藏高原地区沿27.5°N~40°N平均的气温距平垂直分布的EOF分解第一模态特征向量在对流层表现为"下降温上增温"的反相变化,其时间系数呈显著负趋势,且存在1978年及1994年的突变点。高原夏季气温在对流层的上下反相变化与我国夏季降水的关系在年际、年代际尺度上均显示:当高原对流层低层至对流层中上部升温而对流层上部降温时,我国夏季降水表现为南方型,其中以江南至华南地区降水显著偏多而我国东北地区降水显著偏少为主要分布特征;另外,长江流域的局部地区及我国西北的部分地区降水也明显偏少,而华北东部的局部地区、青藏高原中部及东部地区以及新疆西北部地区降水明显偏多;降水异常分布在年代际尺度上比年际尺度更显著。环流分析显示:当高原对流层低层至对流层中上部升温而对流层上部降温时东亚中高纬度地区为异常高压控制,中低纬度地区受异常低压影响。环流场与降水分布有较好的配置关系。     

二流—四流球谐函数谱展开累加辐射传输方案在全球气候模式中的应用

本文首先构建了二流—四流球谐函数谱展开累加辐射传输的新方案,然后将其应用于国家气候中心第二代大气环流模式BCC_AGCM2.0.1的新版本中,并与模式中原有的Eddington累加方案进行了比较。由于新方案本质上是单层Eddington近似方案在四流上的推广。因此新方案在计算精度上要优于原方案。通过在全球气候模式中的应用与比较,本文发现新方案对气候模拟会产生比较大的影响。在晴空条件下,新方案计算的在南纬30°到60°区间、北大西洋东北部以及非洲北部的撒哈拉沙漠区域的地表向下年平均短波辐射通量要小于原方案结果,最大差别可以达到3.5 W/m2;同时,新方案计算的在南纬30°到60°区间和北大西洋东北部的大气顶向上年平均短波辐射通量要大于原方案结果,最大差别达到3 W/m2。在有云大气情况下,新方案计算的地表向下年平均短波辐射通量要小于原方案结果,并随着纬度的增加,新旧两种方案的差别逐渐变大,在南北极时达到最大5.5 W/m2;同时,新方案计算的在赤道区域的大气顶的年平均短波向上辐射通量要小于原方案结果,最大差别为2.5 W/m2,而在南北纬30°到60°区间,新方案计算的在大气顶的年平均短波向上辐射通量则要大于原方案结果,最大差别为1.5 W/m2。新方案计算的年平均短波加热率普遍高于原方案结果,特别是在800 hPa到地表之间的低层大气以及50 hPa到100 hPa的高层大气,最大差别可达0.03 K/d。因此,新方案有助于改善全球气候模式中普遍存在的赤道平流层中下层的温度冷偏差现象。     

Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation

Iraq contains the Great Mesopotamian alluvial plain of the Euphrates and Tigris rivers. Its regional vegetation phenological patterns are worthy of investigation because relatively little is known about the phenology of semi-arid environments, and because their inter-annual variation is expected to be driven by uncertain rainfall and varied topography. The aim of this research was to assess and map the spatial variation in key land surface phenology (LSP) parameters over the last decade and their relation with elevation. It is the first study mapping land surface phenology during last decade over the whole of Iraq, and one of only a few studies on vegetation phenology in a semi-arid environment. Time-series of Moderate Resolution Imaging Spectroradiometer (MODIS) normalised difference vegetation index (NDVI) data at 250 m spatial resolution and 8 day temporal resolution, were employed to map the spatial variation in three LSP parameters for the major vegetation types in Iraq during 2001–2012. LSP parameters were defined by inflection points after smoothing the vegetation phenological signals using the Fourier technique. The estimated key LSP parameters indicated that the relatively shorter length of season (LOS) in the north of Iraq resulted from a delayed start of season (SOS). Greater spatial variation occurred in the SOS than end of season (EOS), which may be due to the spatial distribution of rainfall and temperature as a function of elevation. A positive correlation was observed for SOS and EOS with elevation for all major land cover types with EOS producing the largest positive correlation (R² = 0.685, R² = 0.638 and R² = 0.588, p < 0.05 in shrubland, cropland and grassland, respectively). The magnitude of delay in SOS and EOS increased in all land cover types along a rising elevation gradient where for each 500 m increase, SOS was delayed by around 25 or more days and EOS delayed by around 22 or more days, except for grassland. The SOS and EOS also varied temporally during the last decade, particularly the SOS in the lowland, north of the country where the standard deviation was around 80 to 120 days, due mainly to the practice of crop rotation and the traditional biennial cropping system. Thus, the results of this research emphasize the effect of elevation on key LSP parameters over Iraq, for all major vegetation types.     

边坡非线性位移的Verhulst-ARMA组合预测模型研究

针对ARMA模型中时序变量自身变化的复杂性及其预测的不确定性,利用Verhulst提取非平稳时间序列中的趋势项,再对剩下部分采用平稳时间序列建模,建立Verhulst-ARMA组合预测模型。运用文中组合模型对三峡某边坡滑移的实测数据进行分析,验证Verhulst-ARMA组合模型在边坡非线性位移预测中的可靠性和适用性。     

基于专业特点的双语系列课程设计与教学实施研究

高等职业教育是高等教育的一种类型,其教育的国际化水平是衡量高等职业教育水平的重要指标。本文分析了国土资源管理与测绘类专业双语系列课程的特性,提出了递进式双语系列课程设计模式,阐述了三阶段教学实施方案,对双语教学存在的问题提出了对策。     

我国IGS基准站高程时间序列抗差功率谱估计

为更清晰地了解基准站高程序列的周期运动特性,本文采用抗差最小二乘迭代与功率谱估计相结合的方法,分析了我国6个IGS基准站近11年观测得到的高程时间序列数据。在功率谱分析获取准确的高程运动第一主周期项的基础上,继续抗差迭代,并分离出高程方向运动的其他主周期项和振幅,得到了主要周期项对高程方向运动能量的贡献大小,基准站高程方向具有接近一年的年周期运动和多于一年的第二主周期项运动,半周年项运动所占的比重很小。     

基于条件温度植被指数（VTCI）的中国北方地区土壤水分估算

 利用中国北方13省2000-2008年的Terra-MODIS归一化植被指数（[WTBX]NDVI）和地表温度（LST）[WTBZ]数据,以及相同时间段农业气象观测站点的0~10 cm表层土壤水分资料,建立基于条件温度植被指数的表层土壤水分遥感估算模型,计算出2000-2008年北方13省各月份表层土壤水分,主要结论有：（1）空间分布上,表层土壤水分最高的是分区一和分区四,平均值均达到了0.2以上,表层土壤水分最低的是新疆沙漠地区,低于0.05,土壤水分空间分布基本呈"南高北低,东高西低"的趋势;（2）受降雨量和农作物需水的影响,年内月份之间,7、8 两月表层土壤水分最高,4、5、9、10月表层土壤水分最低;（3）年际变化上,2000-2001、2001-2002、2005-2006年北方大部分区域表层土壤水分增加,增加区域面积分别占总面积的79.2%、59.3%和71.4%,而2002-2003、2004-2005年大部分区域表层土壤水分减少,减少区域面积分别占总面积的53.9%和64.1%;（4）降水是影响土壤水分时空分布的一个重要因素。误差分析结果表明,基于条件温度植被指数的土壤水分遥感反演达到了较好的效果,能够较准确地反映北方地区干旱的分布及变化状况。     

Heatwaves in Europe: areas of homogeneous variability and links with the regional to large-scale atmospheric and SSTs anomalies

This work presents a methodology to study the interannual variability associated with summertime months in which extremely hot temperatures are frequent. Daily time series of maximum and minimum temperature fields (T _max and T _min, respectively) are used to define indexes of extreme months based on the number of days crossing thresholds. An empirical orthogonal function (EOF) analysis is applied to the monthly indexes. EOF loadings give information about the geographical areas where the number of days per month with extreme temperatures has the largest variability. Correlations between the EOF principal components and the time series of other fields allow plotting maps highlighting the anomalies in the large scale circulation and in the SSTs that are associated with the occurrence of extreme events. The methodology is used to construct the “climatology” of the extremely hot summertime months over Europe. In terms of both interannual and intraseasonal variability, there are three regions in which the frequency of the extremely hot days per month homogeneously varies: north-west Europe, Euro-Mediterranean and Eurasia region. Although extremes over those regions occur during the whole summer (June to August), the anomalous climatic conditions associated with frequent heatwaves present some intraseasonal variability. Extreme climate events over the north-west Europe and Eurasia are typically related to the occurrence of blocking situations. The intraseasonal variability of those patterns is related to the amplitude of the blocking, the relative location of the action centre and the wavetrain of anomalies downstream or upstream of the blocking. During June and July, blocking situations which give extremely hot climate conditions over north-west Europe are also associated with cold conditions over the eastern Mediterranean sector. The Euro-Mediterranean region is a transition area in which extratropical and tropical systems compete, influencing the occurrence of climate events: blockings tend to be related to extremely hot months during June while baroclinic anomalies dominate the variability of the climate events in July and August. We highlight that our method could be easily applied to other regions of the world, to other fields as well as to model outputs to assess, e.g. the potential change of extreme climate events in a warmer climate.     

基于MODIS的广东省植被指数序列构建与应用

植被指数是衡量植被长势的重要指标,植被指数序列有助于准确地认知植被覆盖、土地利用和土壤水分的时空变化规律,以及进行干旱和植被生长监测.利用2004-2006年的MODIS数据,选择RVI、NDVI和EVI三种植被指数,采用最大值合成法进行广东省植被指数序列构建.按照不同植被覆盖对三种植被指数的年际变化规律进行分析,并通过NDVI进行植被覆盖度计算以及植被覆盖等级分类来分析植被的空间分布.结果表明,建立的植被指数序列能真实地反映植被生长规律,植被覆盖度和广东地区的植被实际分布状况一致.说明建立植被指数序列是动态监测广东省植被长势的及植被环境的变化的有效方法.