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.

小行星9405431 自1960年代后期以来，非洲萨赫勒地区的气候一直以干旱为主。 一些研究表明，撒哈拉以南地区的地表-大气相互作用非常强烈，地表反馈可能在萨赫勒干旱中发挥了作用。 然而，在大多数这些研究中，只使用了简单的表面模型，其结果从未与观测数据进行过验证。 在过去五年中，在萨赫勒地区进行了两次全面的地面实地测量（HAPEX-Sahel和SEBEX）。 这些数据集将用于验证简化版的简单生物圈模型，并为全球气候模式边界条件创建植被数据集。 在校准研究中，将特别注意对共存植被覆盖的现实模拟，这是地表异质性的表现之一。 将调查陆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进水文循环和地表能量收支的模拟。 生物圈-大气耦合模型将用于研究地表过程和大气动力学在确定萨赫勒气候和水文变化方面的作用。 为了理解陆面反馈的机制，我们将把植被和土壤参数分成几组。 将研究每组及其组合对萨赫勒模拟气候异常的影响。 也将研究异质性的影响。 根据上述拟议研究的结果，将进行两次多年数值积分。 长期整合将允许对结果进行更严格的统计学显著性检验。 对照运行的结果将用于分析 撒哈拉以南地区水和能量平衡年循环的模拟。 在异常运行中，萨赫勒地区的地表被指定为荒漠化地区，将用于评估荒漠化在所有季节对区域和全球气候及水文的影响。 由于这项1994年7月25日的敏感性研究是以全面的观测数据为基础的，它的成功完成将有助于我们现实地评估荒漠化对区域和全球气候，特别是萨赫勒干旱的后果。