African Wave Disturbances in the GISS GCM and their Relationship to Climate Variability

GISS GCM 中的非洲波扰动及其与气候变化的关系

• 批准号: 9407018
• 负责人: Leonard Druyan
• 金额: $ 15.09万
• 依托单位: Columbia University
• 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: 1994-08-15 至 1997-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9407018&HistoricalAwards=false
• 关键词: African; Wave; Disturbances; GISS; GCM

ATM-9407018 Druyan, Leonard Columbia University Title: African Wave Disturbances in the GISS GCM and their Relationship to Climate Variability African wave disturbances are wave-like perturbations in the mid- tropospheric easterly circulation of boreal summer over northern Africa which organize distinctive spatial patterns of convergence and often precipitation. Although Sahel seasonal precipitation is associated with these waves, GCM studies of the interannual variability of sub-Saharan rainfall have not explicitly considered their influence. The research is based on preliminary work which found a reasonably realistic representation of African waves in the GISS GCM. The project will study wave behavior in the model at 4x5 degree and 2x2.5 degree horizontal resolution, and the relationship between this modeled behavior and the principal circulation features of the African summer monsoon, namely the tropical and African Easterly Jets. An archive of GCM simulations of some 10-20 summer seasons will be created from model runs forced with observed global SST for selected years during the 1950's through the 1980's (including years of anomalously sparse or abundant Sahel rainfall). In addition, wave characteristics will be analyzed from an ensemble of three equilibrium simulations with doubled CO2 concentration. For each run, model winds and precipitation will be saved as six- hour averages for grid boxes over northern Africa. These data will be used to construct wave composites of winds, divergence and precipitation rates for different locations, months and years. Power spectra of meridional wind and precipitation time series will show the spectral peaks that are related to African wave periodicities. Cross-spectra will document the mutual correlations of circulation and precipitation and spatial mapping of selected spectral amplitudes will highlight the geographical areas of preferred activity. Interannual variations in the composites, spectra, cross-spec tra and spatial and spatial distributions of spectral amplitudes will reflect variability of wave behavior for contrasting scenarios of drought and heavy precipitation and for the warmer, double-CO2 climate. Model results will be compared with analyses of observations in the literature and with analyses of time series of corresponding twice-daily observed ECMWF winds. This research is import because it seeks to increase our ability to simulate and predict climate variability.

ATM-9407018 Druya​​n，伦纳德哥伦比亚大学 标题：GISS GCM 中的非洲波扰动及其与气候变率的关系 非洲波扰动是北非夏季北半球对流层中层东风环流中的波状扰动，它组织了独特的辐合和经常降水的空间模式。 尽管萨赫勒季节性降水与这些波浪有关，但 GCM 对撒哈拉以南降雨年际变化的研究尚未明确考虑其影响。 该研究基于初步工作，在 GISS GCM 中发现了非洲海浪的相当真实的表示。 该项目将研究模型中水平分辨率为 4x5 度和 2x2.5 度的波浪行为，以及该模型行为与非洲夏季季风主要环流特征（即热带和非洲东风急流）之间的关系。 大约 10-20 个夏季的 GCM 模拟档案将根据 1950 年代至 1980 年代选定年份（包括萨赫勒降雨量异常稀疏或丰富的年份）强制观测的全球海表温度的模型运行而创建。 此外，还将通过三个二氧化碳浓度加倍的平衡模拟的集合来分析波浪特征。 对于每次运行，模型风和降水将保存为北非网格盒的六小时平均值。 这些数据将用于构建不同地点、月份和年份的风、散度和降水率的波浪组合。 经向风和降水时间序列的功率谱将显示与非洲波周期性相关的谱峰。 交叉光谱将记录环流和降水的相互关系，所选光谱幅度的空间映射将突出显示首选活动的地理区域。 复合材料、光谱、跨光谱以及光谱幅度的空间和空间分布的年际变化将反映干旱和强降水对比情景以及温暖的双二氧化碳气候下波浪行为的变化。 模型结果将与文献中的观测分析以及相应的每日两次观测到的 ECMWF 风的时间序列分析进行比较。 这项研究很重要，因为它旨在提高我们模拟和预测气候变化的能力。