A high‐latitude convective cloud feedback and equable climates
A high‐latitude convective cloud feedback and equable climates
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DOI：
10.1002/qj.211
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发表时间：
2008
影响因子：
8.9
通讯作者：
D. Abbot;Eli Tziperman
中科院分区：
文献类型：
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作者：
D. Abbot;Eli Tziperman
在一个纬向平均的两层大气模式中识别了对流云对对流层外表面温度的反馈。该模式包含对流、降水和云的简化参数化，以及一个明确取决于二氧化碳、水蒸气和云分数的长波辐射方案。对流云反馈发生在对流层外地表温度升高到足以引发强对流的时候。这导致从低云到高云的变化，以及从负云辐射强迫到中性或正云辐射强迫的变化，这进一步使地表变暖，并导致更多的对流。这种正反馈随着CO2浓度的增加而激活，并导致高边界层温度的气候解决方案，中纬度和高纬度的对流以及赤道到极点的温差减少8-10 °C。赤道到极点温差的减少是由于高纬度局部热平衡的变化，尽管纬向热输送减少，但仍会发生这种变化。对流云的反馈也导致多个平衡和滞后相对于CO2和其他模型变量，虽然这些结果可能是由于模型的简单性。被认为是在高CO2与气候均匀的模型的行为的可能的连接。版权所有© 2008皇家气象学会
A convective cloud feedback on extratropical surface temperatures is identified in a zonally averaged two‐level atmospheric model. The model contains simplified parametrizations for convection, precipitation, and clouds, and a long‐wave radiation scheme that explicitly depends on carbon dioxide, water vapour, and cloud fraction. The convective cloud feedback occurs if the extratropical surface temperature is increased enough to initiate strong atmospheric convection. This results in a change from low to high clouds and from negative to neutral or positive cloud radiative forcing, which further warms the surface and leads to more convection. This positive feedback activates as the CO2 concentration is increased and leads to a climate solution with high boundary‐layer temperatures, convection at mid and high latitudes, and an Equator to Pole temperature difference that is reduced by 8–10 °C. The reduction in Equator to Pole temperature difference is due to changes in high‐latitude local heat balance and occurs despite decreased meridional heat transport. The convective cloud feedback also leads to multiple equilibria and hysteresis with respect to CO2 and other model variables, although these results may be due to the simplicity of the model. The possible connection of the behaviour of the model at high CO2 with equable climates is considered. Copyright © 2008 Royal Meteorological Society