Changes in Sahel Land-Surface Characteristics and Climate Variation

萨赫勒地表特征变化和气候变化

• 批准号: 9405431
• 负责人: Yongkang Xue
• 金额: $ 19万
• 依托单位: Institute of Global Environment and Society
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-01 至 1997-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9405431&HistoricalAwards=false
• 关键词: Changes; Sahel; Land; Surface; Characteristics

9405431 Xue The climate in the Sahel area of Africa has been dominated by drought since the late 1960's. A number of studies have shown that the land surface-atmosphere interaction in the sub-Sahara region is very strong and that the land surface feedback may have played a role in the Sahel drought. However, in most of these studies only simple surface models were used and the results were never verified against observational data. Two comprehensive surface field measurements (HAPEX-Sahel and SEBEX) were conducted in the Sahel during the past five years. These data sets will be used to validate a simplified version of the Simple Biosphere Model (SSiB) and to create vegetation data sets for GCM boundary conditions. In the calibration study, special attention will be given to the realistic simulation of co-existing vegetation covers, which is one of the manifestations of surface heterogeneity. The sensitivity of the land-surface scheme to vegetation and soil parameter values will be investigated. This calibration will help us to improve the simulation of the hydrological cycle and the surface energy budget. The coupled biosphere-atmosphere model will be used to study the roles of the surface processes and atmospheric dynamics in determining the variation in the climate and hydrology of the Sahel. To understand the mechanisms of land surface feedback, we will divide the vegetation and soil parameters into several groups. The effects of each group and their combination on the simulated climate anomaly in the Sahel will be examined. The effect of heterogeneity will also be investigated. Based on the results of the above proposed studies, two multi-year numerical integrations will be conducted. The long term integration will allow more stringent statistical significance testing of the results. The results from the control run will be used to analyze The simulation of the annual cycle of water and energy balances in the sub-Sahara area. the anomaly run, in which the land surface in the Sahel is assigned as a desertification area, will be used to assess the effects of the desertification on the regional and global climate and hydrology during all seasons. Since this July 25, 1994 sensitivity study is based upon comprehensive observational data, its successful completion will help us in realistically assessing the consequences of the desertification in the regional as well as the global climate, in particular the Sahel drought.

9405431 XUE自1960年代后期以来，非洲萨赫勒地区的气候一直由干旱主导。 许多研究表明，撒哈拉以南地区的土地表面 - 大气相互作用非常强，并且土地表面反馈可能在萨赫勒干旱中发挥了作用。 但是，在大多数研究中，仅使用了简单的表面模型，并且从未针对观察数据验证结果。 在过去的五年中，在Sahel进行了两次全面的地表测量值（HAPEX-SAHEL和SEBEX）。 这些数据集将用于验证简单生物圈模型（SSIB）的简化版本，并为GCM边界条件创建植被数据集。 在校准研究中，将特别注意共存植被覆盖物的现实模拟，这是表面异质性的表现之一。 将研究土地表面方案对植被和土壤参数值的敏感性。 这种校准将有助于我们改善水文周期和表面能预算的模拟。 耦合的生物圈 - 大气模型将用于研究表面过程和大气动力学在确定sahel气候和水文学变化方面的作用。 为了了解土地表面反馈的机制，我们将植被和土壤参数分为几组。 将检查每个组及其组合对SAHEL中模拟气候异常的影响。 异质性的影响也将被研究。 根据上述研究的结果，将进行两项多年数值整合。 长期集成将允许对结果进行更严格的统计显着性测试。 控制运行的结果将用于分析撒哈拉以南地区水和能量平衡的年度周期的模拟。 萨赫勒（Sahel）中的陆地表面被指定为荒漠化区域的异常奔跑，将用于评估荒漠化对所有季节中地区和全球气候和水文学的影响。 自1994年7月25日的敏感性研究基于全面的观察数据以来，其成功完成将有助于我们实际评估区域和全球气候，尤其是萨赫勒干旱的荒漠化的后果。