An empirical model for the statistics of sea surface diurnal warming
An empirical model for the statistics of sea surface diurnal warming
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DOI：
10.5194/os-8-197-2012
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发表时间：
2012-03
期刊：
影响因子：
3.2
通讯作者：
M. Filipiak;C. Merchant;H. Kettle;P. Borgne
中科院分区：
文献类型：
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作者：
M. Filipiak;C. Merchant;H. Kettle;P. Borgne
本文从数值天气预报模式出发，建立了一个海表温度日变化与海面净热通量和海面风速的统计模式。该模型是使用通量和风从欧洲中期天气预报中心（ECMWF）数值预报模式和SST从旋转增强可见光和红外成像仪（SE-VIRI）。在模式中，日增暖量与黎明以来（约10月）积分的地面净热通量呈线性关系，与同期地面风速最大值呈二次反比关系。对于给定的积分热通量，通过匹配最大风速和观测到的变暖的频率分布来找到模式系数。昼夜冷却，它发生的地方，模拟成比例的综合热通量除以热容量的季节性混合层。该模型再现了SEVIRI观测到的SST日变化的统计数据（平均值、标准差和95百分位数），并再现了高级微波扫描辐射计（AMSR-E）观测到的平均变暖的地理格局。我们使用统计模型中的函数依赖性来测试两个昼夜变暖物理模型的行为，显示对比系统误差。及其地球物理影响，以及现有的昼夜变暖模型的审查，强调他们如何不同的目的和性质，从本文开发的模式。第2节描述了统计模型，第3节给出了数据和拟合程序的详细信息。第4节描述了该模型的性能和一些验证。本文的倒数第二部分给出了使用统计模型来评估由两个基于物理的模型预测的日变暖分布的示例，这两个模型似乎都不准确地匹配在测试的整个功能范围内观察到的分布。最后，我们总结了一个最后的部分，把在更广泛的背景下，在文件中提出的结果。海表日变暖是海表温度（SST）的次日变化，主要与太阳加热的日周期相关（尽管其他影响因素也可能具有日周期）。白天，海洋上层几米的海水受到短波太阳辐射的加热。这种加热通常被净输出长波辐射和感热和潜热通量的冷却部分抵消。海洋顶部5 m吸收60%的入射太阳辐射（Fairall等人，1996年），因此，有一种倾向，近地表变暖超过透光区的水柱作为一个整体。在夜间，由于其他热通量，水柱通常会从表面冷却。这种日变热和日变冷的过程给出了海面温度的日循环。一般来说，SST的日变化不大。Kennedy等人（2007年）在赤道纬度20 °范围内观测到漂移浮标SST的峰峰值平均振幅为0.4 K。整个海洋的平均振幅（根据下文将讨论的卫星观测）
A statistical model is derived relating the diurnal variation of sea surface temperature (SST) to the net surface heat flux and surface wind speed from a numerical weather prediction (NWP) model. The model is derived using fluxes and winds from the European Centre for Medium-Range Weather Forecasting (ECMWF) NWP model and SSTs from the Spinning Enhanced Visible and Infrared Imager (SE- VIRI). In the model, diurnal warming has a linear depen- dence on the net surface heat flux integrated since (approx- imately) dawn and an inverse quadratic dependence on the maximum of the surface wind speed in the same period. The model coefficients are found by matching, for a given inte- grated heat flux, the frequency distributions of the maximum wind speed and the observed warming. Diurnal cooling, where it occurs, is modelled as proportional to the integrated heat flux divided by the heat capacity of the seasonal mixed layer. The model reproduces the statistics (mean, standard deviation, and 95-percentile) of the diurnal variation of SST seen by SEVIRI and reproduces the geographical pattern of mean warming seen by the Advanced Microwave Scanning Radiometer (AMSR-E). We use the functional dependencies in the statistical model to test the behaviour of two physical model of diurnal warming that display contrasting systematic errors. and its geophysical impacts, together with a review of exist- ing diurnal warming models, emphasizing how they differ in purpose and nature from the model developed in this paper. Section 2 describes the statistical model, with the details of data and fitting procedures given in Sect. 3. Section 4 de- scribes the performance and some validation of the model. The penultimate section of the paper gives an illustration of the use of the statistical model to assess the distributions of diurnal warming predicted by two physically based models, neither of which seem accurately to match the observed dis- tributions over the full functional range tested. We conclude the paper with a final section which puts the results presented in the paper in a wider context. Diurnal warming of the sea surface is the sub-daily varia- tion in sea surface temperature (SST) associated principally with the daily cycle in solar heating (although other influen- tial factors may also have a daily cycle). During the day, the upper few metres of the ocean are heated by short-wave solar radiation. This heating is usually partially offset by cooling via net outgoing long-wave radiation and sensible and latent heat fluxes. The top 5 m of the ocean absorbs 60 % of the in- coming solar radiation (Fairall et al., 1996), and thus there is a tendency for the near-surface to warm more than the photic zone of the water column as a whole. During the night, the water column will usually cool from the surface due to the other heat fluxes. This daily progression in heating and cool- ing gives a diurnal cycle in the sea-surface temperature. Generally, the diurnal cycle in SST is modest. Kennedy et al. (2007) observed a peak-to-peak mean amplitude in drift- ing buoy SSTs of 0.4 K for observations within 20 of lati- tude of the equator. The mean amplitude for the ocean as a whole (based on satellite observations to be discussed below)