The effect of Arabian Sea optical properties on SST biases and the South Asian summer monsoon in a coupled GCM
The effect of Arabian Sea optical properties on SST biases and the South Asian summer monsoon in a coupled GCM
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DOI：
10.1007/s00382-011-1254-3
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发表时间：
2012-04
期刊：
影响因子：
4.6
通讯作者：
Andrew G. Turner;Manoj Joshi;E. Robertson;S. Woolnough
中科院分区：
文献类型：
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作者：
Andrew G. Turner;Manoj Joshi;E. Robertson;S. Woolnough
这项研究研究了季节性变化的叶绿素对阿拉伯海和南亚季风气候的影响。这种季节性对上层海洋辐射特性的影响通常是耦合大气环流模型中缺失的过程，并且其在该地区的大幅度变化使其成为研究的相关选择，以确定对阿拉伯海平均和季节性系统偏差的影响。在这项研究中，我们研究了英国气象局结合大气-海洋 GCM HadCM3 由于浮游植物大量繁殖而将季节周期纳入叶绿素的影响。这是通过进行实验来实现的，其中阿拉伯海水的光学特性（该地区浮游植物繁殖半年周期的关键信号）是根据海景宽视场传感器 (SeaWiFS) 数据导出的叶绿素气候学计算得出的。 SeaWiFS 叶绿素是在年平均和季节性变化的实验中规定的。为了应对晚春的叶绿素绽放，混合层深度的偏差减少了高达 50%，并且地表变暖，导致季风爆发期间降雨量增加。然而，当北半球冬季和夏季季风完全形成并且存在强烈的表面风和较深的混合层时，混合层深度的偏差减小，但表面会经历冷却。研究发现海表温度对叶绿素响应的季节性取决于混合层与太阳通量异常穿透深度的相对深度。因此，纳入叶绿素对上层海洋辐射特性的影响可以减少混合层深度的偏差并增加海表温度的季节性。
This study examines the effect of seasonally varying chlorophyll on the climate of the Arabian Sea and South Asian monsoon. The effect of such seasonality on the radiative properties of the upper ocean is often a missing process in coupled general circulation models and its large amplitude in the region makes it a pertinent choice for study to determine any impact on systematic biases in the mean and seasonality of the Arabian Sea. In this study we examine the effects of incorporating a seasonal cycle in chlorophyll due to phytoplankton blooms in the UK Met Office coupled atmosphere-ocean GCM HadCM3. This is achieved by performing experiments in which the optical properties of water in the Arabian Sea—a key signal of the semi-annual cycle of phytoplankton blooms in the region—are calculated from a chlorophyll climatology derived from Sea-viewing Wide Field-of-View Sensor (SeaWiFS) data. The SeaWiFS chlorophyll is prescribed in annual mean and seasonally-varying experiments. In response to the chlorophyll bloom in late spring, biases in mixed layer depth are reduced by up to 50% and the surface is warmed, leading to increases in monsoon rainfall during the onset period. However when the monsoons are fully established in boreal winter and summer and there are strong surface winds and a deep mixed layer, biases in the mixed layer depth are reduced but the surface undergoes cooling. The seasonality of the response of SST to chlorophyll is found to depend on the relative depth of the mixed layer to that of the anomalous penetration depth of solar fluxes. Thus the inclusion of the effects of chlorophyll on radiative properties of the upper ocean acts to reduce biases in mixed layer depth and increase seasonality in SST.