雅鲁藏布江流域1978-2009年气候时空变化及未来趋势研究

利用1 km 分辨率DEM数据及ArcHydro Tools 提取了雅鲁藏布江流域边界, 明确给出了该流域具体的地理边界及空间范围. 依据雅鲁藏布江流域范围内及周边39个气象站点1978-2009年近32 a逐年气象数据, 综合运用GIS空间插值技术及气象统计分析方法, 对雅鲁藏布江流域气候(着眼于降水和气温指标)时空变化特征及未来变化趋势进行了研究. 结果表明: 1978-2009年间流域范围内多年平均降水大致趋势为由西至东逐步增加, 年平均降水量以7.935 mm·(10a)^-1的速度缓慢增加. 流域多年平均气温大致由河源至下游逐渐升高, 河谷腹地至流域边界处逐渐降低, 并出现了以拉萨、乃东为中心的局部高温带; 近32 a流域年平均气温增加2.2 ℃, 增加幅度达到0.489 ℃·(10a)^-1, 高于全球及全国同期增温速率. 近10 a间, 流域平均降水以 -139 mm·(10a)^-1的速度显著减少, 气温则以1.14 ℃·(10a)^-1的速度增加, 整个流域气候呈现暖干趋势. 利用R/S分析法预测得知, 流域年降水量可能出现短时间的减少波动, 但未来较长一段时间内, 流域降水及气温仍将保持增加趋势, 流域气候呈现暖湿化趋势.     

新疆积雪覆盖时空变异分析

利用2000-2010年MODIS积雪覆盖产品数据MOD10A2,提取了新疆近10年来积雪覆盖变化信息,并结合地面站点数据,对遥感积雪覆盖估算的精度进行了验证;分析了新疆积雪覆盖的年际、年内变化及南北疆积雪覆盖变化的差异;结合数字高程模型,分析不同高程带下积雪覆盖的时空变化规律,揭示高程因素对新疆积雪时空变化的影响。结果表明:MOD10A2提取的积雪信息能够反映新疆的积雪变化情况,总体精度达92.3%;近10年来,全疆年积雪覆盖率最大值范围为34.0%~51.7%,最小值范围为1.7%~2.6%;积雪覆盖比率的变化在南北疆差异明显,南疆区域积雪覆盖整体不高,年内积雪覆盖比率变化幅度低于50%;而北疆区域由于受复杂地形和气候带的影响,积雪覆盖比率大,年内的变化幅度强,除2008年均达到80%以上;在季节变化上,春季和秋季的积雪覆盖均值波动较为明显,夏季和冬季的积雪覆盖均值则波动较小,这一规律在北疆地区表现更为显著;积雪覆盖的时空分布与变化受高程的影响,在海拔4 000 m以下区域,夏季积雪覆盖比率低,冬季积雪覆盖比率高,而6 000 m以上海拔区域则表现出完全相反的特点,即夏季积雪覆盖比率高,冬季积雪覆盖比率低。     

中间层与低热层二氧化碳体积混合比的年际变化特征研究

利用17年的SABER(Sounding of the Atmosphere using Broadband Emission Radiometry)Level2C数据研究了中间层与低热层大气(MLT, Mesosphere and Lower Thermosphere) CO₂ VMR(Volume Mixing Ratio)的年际变化特征.使用多元线性回归模型对双月平均时间序列拟合,定量地提取各变化特征.结果表明,SABER CO₂ VMR长期趋势在中间层保持在5.5%/decade左右,在中间层顶和低热层降低至4.5%/decade左右;结果与模式预测在统计意义上相符.长期趋势没有显著的纬度差异,但在各纬度上都具有明显的季节依赖,MLT CO₂ VMR长期趋势的季节性改变源自低层大气长期趋势季节性改变.SABER CO₂ VMR对QBO (Quasi-Biannual Oscillation)和ENSO (El Ni1o-Southern Oscillation)在绝大多数区域没有统计显著的响...     

曹妃甸邻近海域浮游动物群落时空变化及其影响因素

根据2013年8月(夏季)和2014年5月(春季)在曹妃甸邻近海域的调查资料,研究了浮游动物群落的种类组成、丰度、生物量、优势种和多样性的时空变化特征,分析了其与环境因子的关系,并结合2004年调查资料对比分析了浮游动物丰度和优势种的变化特征及围填海的影响。结果表明,研究海域浮游动物共鉴定得到31种(类),以桡足类和浮游幼体为主,优势种主要包括双刺纺锤水蚤(Acartia bifilosa)、小拟哲水蚤(Paracalanus parvus)、拟长腹剑水蚤(Oithona similis)和桡足类幼体(Copepodid larva)等。春季的浮游动物丰度和生物量均高于夏季,多样性和均匀度指数均低于夏季。浮游动物丰度的空间分布主要受温度、叶绿素a(Chl-a)等环境因子影响,春季基本为近岸高、远岸低的空间分布规律,夏季则相反,基本为近岸低、远岸高的空间分布规律。与2004年相比,本次调查春季和夏季的浮游动物丰度明显下降,可能与浮游植物丰度及DIP浓度降低有关。春季,西侧、东侧海域的浮游动物丰度分别明显降低、升高,与围填海后营养盐重新分布促进了东侧海域浮游植物增殖有关。夏季则主要受河流输...     

Diel discharge variations in dormant and growing seasons in a headwater catchment suggest potential sources of an evapotranspiration signal

Diel fluctuations in discharge not associated with precipitation have been identified in streams around the world and attributed to evapotranspiration of both hillslope and near-stream vegetation. Several mechanisms have been hypothesized to explain the generation of these signals, but a consensus has not been reached. In order to investigate the origin of these daily discharge fluctuations, we measured discharge and groundwater levels in a 43-ha headwater catchment near Cullowhee, NC, USA. The catchment was logged at least twice in the past 120 years, allowing the evergreen invasive Chinese privet (Ligustrum sinense) to become established in near-stream areas. Stream discharge was measured at the outlet, and stream stage and near-stream groundwater level were measured at a second location higher in the catchment. Daily fluctuations in discharge were quantified and found to increase in magnitude with daily mean discharge. Interestingly, daily discharge fluctuations were observed in the dormant season, and our analysis suggests that their magnitude may increase more with discharge than during the growing season. Two previously hypothesized processes may explain our observations. A decrease in signal dampening due to faster transmission of an evapotranspiration signal at elevated flows may explain the increased diel fluctuation magnitude at higher flows. Additionally, because the primary active vegetation in our catchment in the dormant season is in near-stream areas, we suggest that this indicates most of the evapotranspiration signal in stream discharge is derived from near-stream vegetation, not hillslopes.     

The role of landscape morphology on soil moisture variability in semi-arid ecosystems

Previous studies on semi-arid ecosystems have shown high values of soil moisture variability (SMV) primarily induced by the combined effects of non-uniform precipitation, incoming solar radiation, and soil and vegetation properties. However, the relative impact of these various factors on SMV has been difficult to evaluate due to limited availability of field data. In addition, only a limited number of studies have analysed the role of landscape morphology on SMV. Here we use numerical simulations of a simple hydrological model, the Bucket Grassland Model, to systematically analyse the effect of each contributing factor on SMV on two different landscape morphologies. The two different landform morphologies represent landscapes dominated respectively by either diffusive erosion or fluvial erosion processes. We conducted various simulations driven by a stochastically generated 100-year climate time series, which is long enough to capture climatic fluctuations, in order to understand the effect of various soil moisture controlling factors on the spatiotemporal SMV. Our modelling results show that the fluvial dominated landscapes promote higher spatial SMV than the diffusive dominated ones. Further, the role of landform morphology on SMV is more pronounced in regions where the spatial variability of incoming solar radiation and precipitation is high.     

Analysis on mechanisms of anomalous variations of tropopause pressure over the Tibetan Plateau during summer in Northern Hemisphere

Using the monthly mean data from NCEP–NCAR reanalysis, through building tropopause pressure index, we investigated the mechanisms of anomalous variations of tropopause pressure over the Tibetan Plateau during summer in Northern Hemisphere. For comparative analysis we selected representative years of 1992 and 1998 to study, and they were respectively the highest and the lowest year of tropopause pressure anomaly over the Tibetan Plateau. The results are summarized as follows: (1) Over the Tibetan Plateau, the variations of tropopause pressure are well correlated respectively with anomalous temperature and geopotential height in both troposphere and stratosphere. Besides, the anomalous tropopause pressure has also close relation with anomalous surface temperature in the Tibetan Plateau. In 1992, the surface temperature was anomalously low, correspondingly, the tropopause pressure over the Tibetan Plateau was anomalously high; but in 1998, the opposite was the case. (2) Over the Tibetan Plateau, the correlation of tropopause pressure and OLR (Outgoing Longwave Radiation) is found to be positive. Furthermore, by further diagnosing the circulation fields between 850 hPa and 200 hPa levels and the whole troposphere vapour field, we found out that the anomalously high tropopause pressure in 1992 corresponded to the anticyclonic divergence of low level wind fields and the cyclonic convergence of high level wind fields, and coupled with divergence of the whole troposphere vapour fields along with the South Asian High weakened at the same time. While in 1998, the case was opposite to that in 1992. These facts indicated that the anomalous convection resulted in the significant difference of tropopause pressure in 1992 and 1998 over the Tibetan Plateau. (3) The vertically integrated heat budget anomalies were responsible for explaining tropopause pressure anomalies in 1992 and 1998 over the Tibetan Plateau.     

50年来秦岭金钱河流域水文特征及其对降水变化的响应

运用集中度和集中期、Kendall秩相关系数、R/S分析法、降水—径流双累积曲线模型及其他数理统计方法,分析了金钱河流域径流的变化特征,探讨了年际、季节及月尺度上径流变化的趋势并预测了未来趋势,用集中期指标反映了径流对降水响应的滞后效应,并定量分析了降水变化和人类活动对径流变化的贡献率。结果表明:50 a来径流量呈现出显著的递减趋势(p<0.05),递减率为34.33 m3(/s 10a),Hurst指数H=0.669>0.5,表明未来的一段时间内变化趋势与现在相同;1~12月各月径流均表现为下降趋势。流域内径流对降水的响应存在滞后效应,50 a径流对降水平均每年滞后23.6 d,且滞后天数具有明显上升趋势。50 a来径流系数呈极显著减小趋势,降水量转化为径流的部分在逐年减少,被植物截留、填洼、入渗和蒸发的部分增加;径流发生突变后比突变前径流系数降低了35.2%。50 a来降水变化对径流变化的影响率为53.4%,高于人类活动影响率46.6%,是导致径流变化的主要原因,人类活动为次要原因。     

阿克苏地区雷暴时空变化特征

 利用阿克苏地区1960—2010年雷暴资料,采用气候倾向率、保证率等气候诊断方法,探讨了阿克苏地区雷暴的时空分布规律、气候变化趋势等。结果表明,阿克苏地区雷暴空间分布表现为西多东少、北多南少,位于该地区西部的乌什县为雷暴多发中心;全区年平均雷暴日数为18.7~52.0 d;阿克苏地区每10 a雷暴日数减少2.8 d;雷暴主要集中在3—11月,7月达到最大值,11月下旬至翌年2月基本无雷暴;80%的保证率下雷暴初日出现在5月中旬至下旬之间,雷暴终日出现在9月下旬至10月中旬之间;阿克苏地区一日当中雷暴主要发生在午后至前半夜,雷暴高峰值出现在16—19时,雷暴平均持续时间在35~47 min,雷暴出现最多的方位是W和N。     

塔里木盆地西北缘前陆冲断带构造分段特征及勘探方向

通过12条典型地质剖面的综合构造建模,系统建立了塔里木盆地西北缘不同构造部位的地质模型,经过平衡恢复求取了变形量,探讨了前陆冲断带的构造分段特征、转换方式及其控制因素,进而指出塔里木盆地西北缘的有利勘探方向和领域。研究发现塔里木盆地与南天山造山带边界断裂系呈东、西两段不连续展布,整体控制前陆冲断带的构造展布格局。根据构造特征的差异性,将塔里木盆地西北缘前陆冲断带划分为7段,不同构造部位变形量差异巨大,向前陆不均一推覆扩展,最小水平缩短量约8.7～64.5km。中部温宿-乌什地区是前陆冲断系统构造转换过渡的关键地区,在该区构造样式由邻区盖层滑脱突变为基底卷入,缩短量也由邻区30～60km突降至9.8～25km。研究表明塔里木盆地西北缘前陆冲断带构造分段和不均一推覆扩展特征受先期构造、地层结构和动力学条件等因素控制,构造样式和变形量侧向变化主要靠走滑断裂和基底断裂调节。