青藏高原强降水日数的时空分布特征

 根据青海和西藏48个气象台站近48 a（1961-2008年）的逐日降水和气温资料,分别以日降水量超过5 mm和25 mm作为冬半年（11月～翌年3月）和夏半年（5～9月）强降水的临界值,分析了青藏高原冬、夏半年强降水日数的时空分布特征。结果表明：（1）高原强降水日数与总降水量的空间分布型非常相似,夏半年均表现为由东南向西北递减,而冬半年则为由高原腹地向四周递减。（2）夏（冬）半年强降水主要集中在7月上旬～8月中旬（11月上旬和3月中下旬）。（3）夏（冬）半年强降水存在准6 a（5～6 a）的年际振荡以及准10～11 a（15 a）的年代际振荡。（4）强降水日数变化趋势的空间差异较大,夏半年高原北（南）部强降水日数普遍以增加（减少）趋势为主,而冬半年除雅鲁藏布江流域呈减少趋势外,高原大多数地区均表现出显著增加趋势。     

黄土区人类活动影响下的 产汇流模拟研究

日益频繁的人类活动改变了流域下垫面条件,对流域产汇流产生很大的影响。本文以黄河中游典型支流岔巴沟为研究区域,提出利用基于DEM的分布式水文模拟技术,探讨流域人类活动过程中的产汇流模拟,避免了经验公式的概化和由此引起的局限。模拟的结果证实了该方法的可行性。采用网格滞蓄的方法可以在子网格上体现人类活动引起的下垫面的变化及其对产汇流的影响,反映各个时期的产汇流条件,对降雨做出合理响应。     

Urban re-generations: afterword to special issue on the politics of urban greening in Australian cities

ABSTRACT

‘Urban re-generations' is written as an afterword to the special issue of Australian Geographer on ‘The Politics of Urban Greening in Australian Cities'. The collection prompts a deep questioning of reparative and regenerative work associated with greening, green spaces and green infrastructures. The climate-driven 2019-2020 bushfire crisis and COVID-19 have amplified the visibility of the more-than-human connectivity of our cities and the deep underlying structures of social and environmental inequity underpinning a variety of urban green spaces and agendas. Inspired by the articles in this special issue, the afterword explores how we might call back the grammars and practices of regeneration from their service to the neo-liberal, settler-colonial city and instead nurture reparative de-colonial practices that aid in the collaborative work of re-composing, becoming into better relation with, and working in modes of situated historical and cultural difference, with green and just cities.     

大别山及其周边现今垂直形变研究

基于1980年、2005年和2015年3期区域精密水准网观测资料,利用线性动态平差模型计算获取大别山地区水准网长期垂直运动速度场图像。研究发现,淮河平原地表下沉较为严重,大别山呈现弱隆升趋势运动,长江谷地边缘地区较大别山区呈现明显的隆升运动。跨郯庐断裂带水准剖面结果显示,垂直运动与地形呈负相关和弱相关。     

COMBINATION OF ECMWF REANALYZED DAILY RAINFALL AND PENTAD CMAP IN CHINA

In this study, 16 combinations of the ECMWF (European Centre for Medium-Range Weather Forecast) reanalyzed daily rainfall and the pentad CMAP in China for the period 1980- 1993( 1May - 31 Dec. ) were calculated. Correlation analysis was used to roughly evaluate daily rainfall for the whole of China and a combination of RPC (rotated principal component) and wavelet analyses was applied to data on observed and combined daily rainfall to obtain a detailed evaluation of the quality of these combined datasets in 6 selected major rainfall regions of eastern China. The results showed that except for intraweekly fluctuation, the best combination was roughly similar to or accorded well with observation in the aspects of space variation patterns and long period rainfall fluctuations related to monsoon onset and serious meteorologic disasters, indicating that this combination yielded better values of long term daily mean and standard deviation through the pentad CMAP ( CPC Merged Analysis of Precipitation), and can also represent rainfall fluctuations through the reanalyzed daily rainfall.     

An analysis of the causes of decadal variations of rainfall in Shandong in summer

The precipitation in Shandong in July, August as well as the whole summer (JJA) and the corresponding 500hPa geopotential height fields are analyzed by means of the SVD (singular value decomposition) methodology. It is found that the general circulations in East Asia and the Western Pacific underwent decadal changes around 1979. The geopotential height, in particular over key areas like the South China Sea and the Philippines, increased after 1979. Corresponding to the changes in the geopotential height, the rainfall in Shandong started to decrease around 1979. The synthesized analysis shows that when the geopotential height at 500hPa level decreases in the key areas, the Western Pacific subtropical high shifts northward and an anticyclonic anomalous cell enforces the southerly flow over Shandong-Korea-Japan, Shandong could experience a wet period. A dry period is likely to occur when the geopotential height increases in these key areas, the subtropical high moves southward or expands westward to a great distance, and a cyclonic anomalous cell controls Shandong. Respective conceptual models for the causative mechanism are obtained for the cases of July, August and the whole summer (JJA).     

Second kind Chebyshev operational matrix algorithm for solving differential equations of Lane–Emden type

In this paper, we present a new second kind Chebyshev (S2KC) operational matrix of derivatives. With the aid of S2KC, an algorithm is described to obtain numerical solutions of a class of linear and nonlinear Lane–Emden type singular initial value problems (IVPs). The idea of obtaining such solutions is essentially based on reducing the differential equation with its initial conditions to a system of algebraic equations. Two illustrative examples concern relevant physical problems (the Lane–Emden equations of the first and second kind) are discussed to demonstrate the validity and applicability of the suggested algorithm. Numerical results obtained are comparing favorably with the analytical known solutions.     

极端降雨事件对不同类型生物土壤结皮覆盖土壤碳释放的影响

于2011年5-8月,选择腾格里沙漠东南缘人工固沙植被区藻类、藓类和混生结皮覆盖的土壤为对象,研究了极端降雨量(降雨量44.7 mm、强度0.04 mm,min-1)、极端降雨强度(降雨量8.3 mm、强度0.55 mm·min-1)及普通降雨(降雨量16.3 mm、强度0.02 mm·min-1)条件下的碳释放过程.碳释放量的测定采用Li-6400-09土壤呼吸室,降雨结束后立即开始观测,直到呼吸速率恢复到降雨前水平时停止观测.结果表明:极端降雨(降雨量和降雨强度)结束初期藻类和混生结皮覆盖土壤的呼吸速率受到明显抑制,藻类结皮覆盖土壤呼吸速率分别为0.12 μmol·m-2·s-1和0.41 μmol·m-2·s-1,混生结皮覆盖土壤呼吸速率分别为0.10 μmol·m-2·s-1和0.45μmol·m-2·s-1;而极端降雨对藓类结皮覆盖土壤的影响不明显,呼吸速率分别为0.83 μmol·m-2·s-1和1.69μmol·m-2·s-1.这说明处于演替高级阶段的藓类结皮能够很好地应对短期的极端降雨事件.     

基于径流还现的洮河流域径流变化特征研究

河川径流还现计算是准确反映区域水资源状况的基础,同时也是水资源规划和决策的重要依据.选取甘肃省洮河流域李家村、红旗2个代表水文站长系列径流资料作为基础数据,在还原计算的础上,对洮河流域径流进行还现计算,同时对径流变化特征进行研究.结果 表明:1956—2016年洮河流域李家村、红旗多年平均实测径流量分别为39.52×1...