Last Millennium Reanalysis with an expanded proxy database and seasonal proxy modeling
Last Millennium Reanalysis with an expanded proxy database and seasonal proxy modeling
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DOI：
10.5194/cp-15-1251-2019
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发表时间：
2018-09
影响因子：
4.3
通讯作者：
R. Tardif;G. Hakim;W. Perkins;K. Horlick;M. Erb;J. Emile‐Geay;D. Anderson;E. Steig;D. Noone
中科院分区：
文献类型：
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作者：
R. Tardif;G. Hakim;W. Perkins;K. Horlick;M. Erb;J. Emile‐Geay;D. Anderson;E. Steig;D. Noone
抽象。最后一千年再分析（LMR）利用集合方法来同化古气候数据，以生成每年解析的共同时代气候场重建。两个关键要素是这项工作的重点：一套同化的代用记录和将气候变量映射到代用测量值的前向模型。更新的代理数据库和基于季节回归的正演模型的基础上的结果进行比较的LMR原型，这是基于一个较小的代理记录和简单的代理模型制定为单变量线性回归对年温度。对各种仪器时代的网格分析的验证表明，地面气温和500 hPa位势高度的新重建显着改善（从10%到100%以上），而帕尔默干旱严重程度指数重建的改善更为温和。旨在隔离改善来源的其他实验揭示了更新的代用记录的重要性，包括珊瑚记录，以改善热带重建，树木年轮密度记录的温度重建，特别是在高北方纬度地区。代理的季节性响应，并依赖于温度和湿度的树木年轮宽度，也有助于改善重建的热力学和水文气候变量在中纬度地区的模型。在几十年到百年尺度的温度的变化也被证明是敏感的同化代理集，特别是列入主要是水分敏感的树轮宽度记录。
Abstract. The Last Millennium Reanalysis (LMR) utilizes an ensemble methodology to assimilate paleoclimate data for the production of annually resolved climate field reconstructions of the Common Era. Two key elements are the focus of this work: the set of assimilated proxy records and the forward models that map climate variables to proxy measurements. Results based on an updated proxy database and seasonal regression-based forward models are compared to the LMR prototype, which was based on a smaller set of proxy records and simpler proxy models formulated as univariate linear regressions against annual temperature. Validation against various instrumental-era gridded analyses shows that the new reconstructions of surface air temperature and 500 hPa geopotential height are significantly improved (from 10 % to more than 100 %), while improvements in reconstruction of the Palmer Drought Severity Index are more modest. Additional experiments designed to isolate the sources of improvement reveal the importance of the updated proxy records, including coral records for improving tropical reconstructions, and tree-ring density records for temperature reconstructions, particularly in high northern latitudes. Proxy forward models that account for seasonal responses, and dependence on both temperature and moisture for tree-ring width, also contribute to improvements in reconstructed thermodynamic and hydroclimate variables in midlatitudes. The variability of temperature at multidecadal to centennial scales is also shown to be sensitive to the set of assimilated proxies, especially to the inclusion of primarily moisture-sensitive tree-ring-width records.