黄河源区径流减少的原因探讨

分析了黄河源区1960~2000年气候变化特点,对蒸发进行了估算,并分析了植被和冻土的变化,对径流在20世纪90年代后明显减少的原因进行了探讨。结果表明,黄河源区气温在20世纪80年代中期后明显增加,降水在90年代偏少,气候向暖干方向发展,但蒸发变化不大,径流减少的直接原因是降水的减少;在90年代后降水强度的减弱也可能是径流减少的重要原因;归一化植被指数(NDVI)数据显示植被在90年代后期呈现退化的趋势,冻土在80年代以后表现出的明显的退化趋势,植被冻土的退化可以使得冻结层上水位下移,土壤水向土壤下层的渗漏增加,也会造成径流的减少。     

植被覆盖对暴雨型滑坡影响的初步分析

根据遥感资料、地形数据和历史观测资料等,以江西省为例,分析了森林植被覆盖率、森林生物量和暴雨型滑坡的空间分布,以及森林植被类型对大气降水的截留作用。分析结果初步揭示了植被覆盖对滑坡的影响,认为植被覆盖程度高、生物量多和植被覆盖差、生物量低的中低山区,都可能发生滑坡灾害。不同林冠对降水的截留作用,减缓了降水对斜坡的冲刷,但当降水强度达到或超过暴雨强度时,森林对降水的截留率减小。同等地质环境条件下,植被覆盖率低,滑坡较易发生,但当降水强度较大时,特别是达到诱发滑坡灾害发生的临界值时,植被对滑坡体的重力作用则更加重了滑坡的发生。植被覆盖对滑坡的影响主要取决于降水强度。高森林覆盖区发生滑坡的雨量临界值大于森林覆盖率差的区域。     

巴里坤植被覆盖动态变化及气象因素分析

利用2003-2010年5-10月巴里坤250 m分辨率的EOS-MODIS卫星影像数据,通过预处理、几何校正、NDVI计算以及最大值合成,并计算植被盖度,依照盖度值将地表植被总盖度划分为高、中、低覆盖三类,得到连续8 a巴里坤植被盖度的动态变化:植被总盖度在16%～44%范围内波动,2007年植被盖度相对较高,200...     

全球植被与大气之间碳通量的模式估计

用大气植被相互作用模式(AⅥM)模拟了全球陆地植被的净初级生产力(NPP)。AⅥM由相互耦合的两部分组成：物理过程，包括陆地表面水分和能量在土壤、植被与大气之间的传输；以及生理生态过程，如：光合、呼吸、干物质分配、凋落和物候等。全球的植被分为13类，土壤按质地分为6类。用EMDI提供的全球1637个包括不同植被类型的NPP观测点数据对模型进行了检验。NPP模拟的结果表明：全球陆地植被的平均NPP为405.13 g C m-2yr-1，不同植被类型的平均NPP变化范围在99.58 g C m-2yr-l(苔原)到996.2 g C m-2yr-l(热带雨林)之间。全球年总NPP为60.72 Gt C yr-l，其中最大的部分为热带雨林，15.84 Gt C yr-1，占全球的26.09％。最大的碳汇是在北半球的温带。模式模拟的NPP在全球的空间和季节分布是合理的。     

Improving the vegetation dynamic simulation in a land surface model by using a statistical-dynamic canopy interception scheme

Canopy interception of incident precipitation, as a critical component of a forest＇s water budget, can affect the amount of water available to the soil, and ultimately vegetation distribution and function. In this paper, a statistical-dynamic approach based on leaf area index and statistical canopy interception is used to parameterize the canopy interception process. The statistical-dynamic canopy interception scheme is implemented into the Community Land Model with dynamic global vegetation model （CLM-DGVM） to improve its dynamic vegetation simulation. The simulation for continental China by the land surface model with the new canopy interception scheme shows that the new one reasonably represents the precipitation intercepted by the canopy. Moreover, the new scheme enhances the water availability in the root zone for vegetation growth, especially in the densely vegetated and semi-arid areas, and improves the model＇s performance of potential vegetation simulation.     

Intermediately complex models for the hydrological interactions in the atmosphere-vegetation-soil system

This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis and numerical simulations show that these models, despite their simplicity, can very clearly reveal the essential features of the rather complex hydrological system of atmosphere-ecosystem-soil. For given atmospheric variables, these models clearly demonstrate multiple timescales, the “red shift” of response spectra, multi-equilibria and limit cycles, bifurcation, abrupt change, self-organization, recovery, “desertification”, and chaos. Most of these agree with observations. Especially, the weakening of “shading effect” of living canopy and the wilted biomass might be a major mechanism leading to the desertification in a relatively short period due to overgrazing, and the desertification in a relatively long period or in climate of change might be due to both Charney’s mechanism and the shading effect. These ideas could be validated with further numerical simulations. In the paper, some methods for improving the estimation of timescales in the soil water evolution responding to the forcing are also proposed.     

Effects of heterogeneous vegetation on the surface hydrological cycle

Using the three-layer variable infiltration capacity (VIC-3L) hydrological model and the successive interpolation approach (SIA) of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index (LAI) are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type (85%). Comparison of the modeled results with the observed discharge data suggests that: (1) Daily discharges over the period of 1992–2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. (2) The relative computing error (RCE) of the annual average discharge is ?24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and ?14.32% when an REDC (Resource and Environment Database of China) land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used.     

试用三维地形模式计算茂密林区火险等级

本文用考虑森林植被的三维地形模式，对1972年4月15日神逐架林区森林火灾发生期间的风场、温度场和相对湿度场等进行了模拟，并在此基础上计算森林火险等级。结果表明，采用数值模拟方法可以得到无测站地区的气象要素，为进行森林火险等级预报奠定了基础。     

NIM陆面过程模式的研究Ⅰ：模式建议与对比研究

为了能真实地模拟干旱、半干旱地区以及湿润地区的陆面与大气之间的能量物质交换,发展了一个具有普适性的南京气象学院（ＮＩＭ）陆面过程（ＬＳＰ）模式。该模式是由等温植被参数化方案和本文建立的土壤模式所组成。土壤模式又分为五层模式和两层模式两种。利用１９７９年５～８月“青藏高原气象科学实验”资料作验证,同时将五层模式与Ｄｅａｒｄｏｒｆｆ（１９７８）陆面模式、两层模式作了对比,结果表明五层土壤模式的模拟效果     

青藏高原局地因素对近地表层地温的影响

青藏高原近地表层地温既受区域性因素（高度、经度、纬度）控制，同时又受局地因素的影响。观测结果表明，高原稀疏植被地段比裸地地温高，短时期薄层雪盖起降低地温的作用，南坡比北坡地温高2－7℃，黑色沥青路面年平均温度比碎石土天然的年平均地表温度高4．5℃，亦高于其它材料的路面地温。