Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model
Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model
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DOI：
10.1007/s00382-016-3204-6
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发表时间：
2017-04
期刊：
影响因子：
4.6
通讯作者：
M. Hawcroft;H. Dacre;R. Forbes;K. Hodges;L. Shaffrey;T. Stein
中科院分区：
文献类型：
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作者：
M. Hawcroft;H. Dacre;R. Forbes;K. Hodges;L. Shaffrey;T. Stein
温带气旋是温带天气的一个关键特征，气候模式需要反映这些特征，以便提供可靠的未来气候预测。温带气旋产生大量降水，其潜热释放对其发展起重要作用。本研究评估了气候模式HiGEM代表温带气旋潜在加热的能力。利用遥感数据研究气候模式和ERA-Interim （ERAI）再分析在评估潜热本身之前表征温带气旋云特征的能力。使用离线辐射模拟器、COSP、ISCCP和CloudSat数据集来评估来自HiGEM和ERAI的可比油田。发现HiGEM在温带气旋的云结构中表现出偏差，与ISCCP相比，在温暖的传送带区域产生了过多的高空云。该地区发生了显著的潜热，主要来源于HiGEM的对流方案。ERAI在云结构上也存在偏差，在温暖的传送带地区，较低高度的云比ISCCP观测到的云更多。因此，该地区的潜热释放主要集中在低海拔地区。CloudSat表明，在HiGEM和ERAI，特别是ERAI中，在过低的高度可能产生大量降水，两者都没有捕捉到观测到的降水强度变化。并对HiGEM和ERAI复合温带气旋的位涡结构进行了比较。与ERAI相比，HiGEM在复合材料的前缘形成了一个更明显的对流层顶脊。未来需要解决的一个研究领域是，潜热表征中的这些偏差对HiGEM产生的气候预测有何影响。ERAI中发现的偏差表明，在使用再分析来研究温带气旋的云特征和降水过程或使用再分析来评估气候模式表征其结构的能力时，需要谨慎。
Extratropical cyclones are a key feature of the weather in the extra-tropics, which climate models need to represent in order to provide reliable projections of future climate. Extratropical cyclones produce significant precipitation and the associated latent heat release can play a major role in their development. This study evaluates the ability of a climate model, HiGEM, to represent latent heating in extratropical cyclones. Remote sensing data is used to investigate the ability of both the climate model and ERA-Interim (ERAI) reanalysis to represent extratropical cyclone cloud features before latent heating itself is assessed. An offline radiance simulator, COSP, and the ISCCP and CloudSat datasets are used to evaluate comparable fields from HiGEM and ERAI. HiGEM is found to exhibit biases in the cloud structure of extratropical cyclones, with too much high cloud produced in the warm conveyor belt region compared to ISCCP. Significant latent heating occurs in this region, derived primarily from HiGEM’s convection scheme. ERAI is also found to exhibit biases in cloud structure, with more clouds at lower altitudes than those observed in ISCCP in the warm conveyor belt region. As a result, latent heat release in ERAI is concentrated at lower altitudes. CloudSat indicates that much precipitation may be produced at too low an altitude in both HiGEM and ERAI, particularly ERAI, and neither capture observed variability in precipitation intensity. The potential vorticity structure in composite extratropical cyclones in HiGEM and ERAI is also compared. A more pronounced tropopause ridge evolves in HiGEM on the leading edge of the composite as compared to ERAI. One future area of research to be addressed is what impact these biases in the representation of latent heating have on climate projections produced by HiGEM. The biases found in ERAI indicate caution is required when using reanalyses to study cloud features and precipitation processes in extratropical cyclones or using reanalysis to evaluate climate models’ ability to represent their structure.