Effect of improving representation of horizontal and vertical cloud structure on the Earth's global radiation budget. Part I: Review and parametrization
Effect of improving representation of horizontal and vertical cloud structure on the Earth's global radiation budget. Part I: Review and parametrization
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DOI：
10.1002/qj.647
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发表时间：
2010-07
影响因子：
8.9
通讯作者：
J. Shonk;Robin J. Hogan;John M. Edwards;Gerald G. Mace
中科院分区：
文献类型：
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作者：
J. Shonk;Robin J. Hogan;John M. Edwards;Gerald G. Mace
在大气环流模式（GCM）中，云结构的不良表现被广泛认为是辐射收支中的一个潜在误差源。在这里，我们开发了一种新的方式来表示水平和垂直云结构的辐射计划。这将“三重云”参数化与“指数-随机”重叠相结合，其中通过在每层中使用两个多云区域而不是一个多云区域来引入不均匀性，每个多云区域具有不同的水含量值，其中相邻层中的云不是最大限度地重叠，而是根据垂直去相关尺度。本文，第一部分的两个，旨在参数化的两个效果，使他们可以在GCM中使用。为了实现这一目标，我们首先回顾了一些研究，为全球适用的值的分数标准偏差的水含量用于三重云。我们从各种不同类型的观测中获得了0.75 ± 0.18的值，与云类型或网格大小没有明显的依赖性。然后，通过第二个简短的回顾，我们创建了一个用于指数随机重叠的去相关尺度的参数化，该尺度随纬度线性变化，从赤道的2.9 km到两极的0.4 km。当应用于雷达数据，这两个组件被发现有辐射的影响，能够抵消云的错误陈述所造成的偏见。本文的第二部分将三重云和指数随机重叠应用到辐射代码中，并使用再分析数据检查它们对全球辐射收支的单独和组合影响。版权所有© 2010皇家气象学会和皇冠版权所有
A poor representation of cloud structure in a general circulation model (GCM) is widely recognised as a potential source of error in the radiation budget. Here, we develop a new way of representing both horizontal and vertical cloud structure in a radiation scheme. This combines the ‘Tripleclouds’ parametrization, which introduces inhomogeneity by using two cloudy regions in each layer as opposed to one, each with different water content values, with ‘exponential‐random’ overlap, in which clouds in adjacent layers are not overlapped maximally, but according to a vertical decorrelation scale. This paper, Part I of two, aims to parametrize the two effects such that they can be used in a GCM. To achieve this, we first review a number of studies for a globally applicable value of fractional standard deviation of water content for use in Tripleclouds. We obtain a value of 0.75 ± 0.18 from a variety of different types of observations, with no apparent dependence on cloud type or gridbox size. Then, through a second short review, we create a parametrization of decorrelation scale for use in exponential‐random overlap, which varies the scale linearly with latitude from 2.9 km at the Equator to 0.4 km at the poles. When applied to radar data, both components are found to have radiative impacts capable of offsetting biases caused by cloud misrepresentation. Part II of this paper implements Tripleclouds and exponential‐random overlap into a radiation code and examines both their individual and combined impacts on the global radiation budget using re‐analysis data. Copyright © 2010 Royal Meteorological Society and Crown Copyright