Modeling Anthropogenic Desiccation of the Aral Sea: A Unique Test of the Predictive Capabilities of a Regional Earth System Model

ATM-9632304斯隆，Lisa C.加州大学圣克鲁斯分校标题：模拟咸海的人为干旱：区域地球系统模型预测能力的独特测试全球和区域地球系统模型(ESM)在调查过去气候变化原因和预测未来人类活动影响方面的效用，取决于对特定扰动驱动的变化的预测精度。这种精确度主要取决于反馈模拟的好坏。ESM预测的变化的准确性尚不清楚，因为以前的模型验证仅限于评估当前条件的再现情况，或将古气候模型结果与稀疏和可能含糊的代理数据进行比较。为了对ESM性能进行更彻底的评估，模型预测的变化和观测到的历史时间尺度上的已知扰动引起的变化将进行比较。在这项研究中，咸海的人为干燥将被用来测试区域ESM(与国家大气研究中心相关的RegCM2和湖泊模式)的预测准确性，该模式包括大气和湖泊相互作用的耦合。自1960年以来，咸海干涸的程度足以产生区域气候反应，这是由于周围盆地的密集灌溉引水造成的。这种规模的干燥也应该会产生一个模型反应。重要的是。可以获得横跨干燥间隔的气象和水文观测，因此可以量化实际变化。模型的预测能力将通过将模型模拟的变化与1960年至1995年期间观察到的变化进行比较来测试。这项工作由三个部分组成。首先，观测将被用来量化可能由咸海干燥引起的区域气候和湖泊水文变化。这些观察到的变化将被用来(I)检验模型预测，(Ii)直接测量咸海的存在如何改变区域气候，(Iii)直接测量湖泊水位变化如何影响咸海的水文，以及(Iv)量化区域尺度的人类影响。其次，通过比较模拟和观测的干旱化引起的区域气候和湖泊水文变化，评估交互耦合的REG CM2-Lake模式在预测变化方面的优势和劣势。为了更透彻地了解耦合模型成功和失败的原因，还将评估独立(非交互)版本的RegCM2和湖泊模型在气象或水文观测的驱动下的预测精度。第三，计算了咸水对不同面积、深度和盐度的海洋所产生的区域气候效应。这将使：(1)与湖泊水位变化有关的湖-大气相互作用和反馈的量化；(2)对进一步的人为咸海干化所驱动的未来气候变化的预测；(3)评估模型预测的干燥前和现在之间的变化中有多少是由于大尺度气象变化造成的。将根据已确定的模型的长处和短处来编制和评估对进一步干旱造成的未来气候变化的预测。这项研究很重要，因为它试图测试区域气候湖泊模型如何很好地预测人类活动对大型浅水湖的影响，以及这种影响如何对区域和全球气候产生反馈。

Abstract ATM-9632304 Sloan, Lisa C. University of California, Santa Cruz Title: Modeling Anthropogenic Desiccation of the Aral Sea: A Unique Test of the Predictive Capabilities of a Regional Earth System Model The utility of global and regional earth system models (ESMs) for investigating causes of past climate change, and predicting impacts of future human activities, depends on how accurately changes driven by specific perturbations are predicted. This accuracy is controlled primarily by how well feedbacks are simulated. The accuracy of ESM-predicted changes is unknown, because previous model validation has been limited to assessing how well present conditions are reproduced or comparing paleoclimate model results with sparse and potentially ambiguous proxy data. In order to conduct a more thorough evaluation of ESM performance, model- predicted and observed changes resulting from known perturbations over historical timescales will be compared. In this study, anthropogenic desiccation of the Aral Sea will be used as a test of the predictive accuracy of a regional ESM (the RegCM2 and lake model associated with the National Center for Atmospheric Research) that includes an interactively coupled atmosphere and lake. Desiccation of the Aral Sea since 1960, resulting from diversion of water for intensive irrigation in the surrounding basin, has been extensive enough to produce a regional climatic response. Desiccation of this magnitude should also produce a model response. Importantly. meteorological and hydrologic observations that span the interval of desiccation are available so the actual changes can be quantified. The predictive capabilities of the model will be tested by comparing model-simulated changes with observed changes that have occurred between 1960 and 1995. The work consists of three components. First, observations will be used to quantify regional climate and lake hydrologic changes that are likely due to Aral Sea desiccation. These obser ved changes will be used to (i) test model predictions, (ii) directly measure how the presence of the Aral Sea alters regional climate, (iii) directly measure how lake-level variations have impacted the Aral Sea's hydrology, and (iv) quantify regional-scale human impacts. Second, the interactively coupled Reg CM2-lake model's strengths and weaknesses in predicting changes will be assessed, by comparing simulated and observed desiccation-induced regional climate and lake hydrologic changes. In order to gain a more thorough understanding of the causes for the coupled model's successes and failures, the predictive accuracy of independent (non-interactive) versions of RegCM2 and the lake model, driven by meteorological or hydrologic observations, will also be evaluated. Third, the regional climate effects generated by the Aral for seas of different surface area, depth and salinity will be calculated. This will allow: (i) quantification of lake-atmosphere interactions and feedbacks associated with lake-level variations; (ii) prediction of future climate changes driven by further anthropogenic Arals Sea desiccation; and (iii) assessment of how much of the model predicted change between pre- desiccation and -present and present intervals was due to large-scale meteorological variability. Predictions of future climate changes resulting from additional desiccation will be prepared and evaluated in terms of the model's strengths and weaknesses as determined. This research is important because it seeks to test how well coupled regional climate lake models predict the impact of human activities on a large shallow terminal lake and how that feedbacks on the regional and global climate.