Impact of explicit sun altitude in solar radiation on an ocean model simulation
Impact of explicit sun altitude in solar radiation on an ocean model simulation
复制标题
太阳辐射中明确的太阳高度对海洋模型模拟的影响
DOI：
10.1016/j.ocemod.2009.12.002
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
H. and G. Yamanaka
中科院分区：
文献类型：
--
作者：
Ishizaki;H. and G. Yamanaka
本文对一个海洋模式的敏感性进行了研究，以考察太阳高度对海洋辐射加热的影响。假设太阳光为入射角随时间变化的直射光（SA例），在给定海面日平均辐照度的情况下，估算了太阳光在海面下的日平均穿透量和吸收量的垂直变化，并与强度恒定且垂直向下辐射的情况（CTL例）进行了比较。从理论上预测，太阳角的引入将使日平均穿透辐射的有效衰减深度小于向下瞬时辐射的有效衰减深度，并使辐射吸收轨迹上移，即，辐射吸收量将在上层中增加而在下层中减少，对于低太阳角具有大的对比度。模式结果表明，大部分区域的年平均SST都有增加，而混合层深度（MLD）则有所减小。然而，在某些区域，吸收垂直分布变化的间接影响通过海洋动力学显现出来。一个例子是大尺度平流作用在北太平洋北方产生的深层正温度异常，另一个例子是赤道太平洋赤道流系的变化。在后一区域，温度层结的增加使赤道温度梯度变陡，导致赤道潜流、南赤道流和赤道上升流增强，赤道东太平洋海温下降。生物过程影响太阳辐射的情况也是如此。在月平均场中，夏半球海温距平为正，冬半球为负。冬季强的大气冷却使MLD增大，导致SST受深层温度的影响，SA比CTL冷。这也是100米以上的年平均热含量在SA较低的原因。
A study of the sensitivity of an ocean model was made to examine the effect of introducing the sun altitude on ocean radiant heating. Given the diurnal-mean irradiance at the sea surface under the assumption that all sunlight is direct rays with a diurnally changing incident angle (case SA), the vertical change in the diurnal-mean penetration and absorption amount of the sun light under the sea surface was estimated and compared to the case with constant intensity and vertically downward radiation (case CTL). It was theoretically predicted that introducing the solar angle would make the effective attenuation depth for the diurnal-mean penetrative radiation shallower than that for the downward instantaneous radiation and cause the locus of radiation absorption to shift upward, i.e., the amount of radiation absorption would increase in the upper layer and decrease in the lower layer, with a large contrast for low solar angles. Model results showed that the annual-mean SST increased in most of the model domain as predicted, and the annual-mean mixed layer depth (MLD) decreased. In some regions, however, indirect effects of the change in the vertical distribution of absorption appeared through ocean dynamics. One example is a deep positive temperature anomaly in the northern North Pacific by large-scale advection, and another is a change in the equatorial current system in the equatorial Pacific. In the latter region, increased temperature stratification made the meridional temperature gradient sharper, resulting in the intensification of the Equatorial Undercurrent, of the South Equatorial Current, and of equatorial upwelling, with decreased SST in the eastern equatorial Pacific. The same dynamics works as the case in which biological processes affect the solar radiation. In the monthly mean fields, the SST anomaly is positive in the summer hemisphere but negative in the winter hemisphere. Strong atmospheric cooling in winter increases MLD and leads to SST affected by the temperature of the deep layer, which is cooler in SA than in CTL. This is also the reason why the annual-mean heat content above 100m is lower in SA.