The Role of Large-Scale Atmospheric Circulation in the Relationship between Tropical Convection and Sea Surface Temperature

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Abstract
In this paper, the authors study the influence of the large-scale atmospheric circulation on the relationship between sea surface temperature (SST) and tropical convection inferred from outgoing longwave radiation (OLR). They find that under subsidence and clear sky conditions there is an increase in OLR with respect to SST at a rate of 1.8–2.5 Wm−2 (°C)−1. In regions of large-scale ascending motions, which is correlated to, but not always collocated with, regions of warm water, there is a large reduction of OLR with respect to SST associated with increase in deep convection. The rate of OLR reduction is found to be a strong function of the large-scale motion field. The authors find an intrinsic OLR sensitivity to SST of approximately −4 to −5 Wm−2 (°C)−1 in the SST range of 27°–28°C, under conditions of weak large-scale circulation. Under the influence of strong ascending motion, the rate can be increased to −15 to −20 Wm−2 (°C)−1 for the same SST range. The above OLR–SST relationships are stron... Abstract In this paper, the authors study the influence of the large-scale atmospheric circulation on the relationship between sea surface temperature (SST) and tropical convection inferred from outgoing longwave radiation (OLR). They find that under subsidence and clear sky conditions there is an increase in OLR with respect to SST at a rate of 1.8–2.5 Wm−2 (°C)−1. In regions of large-scale ascending motions, which is correlated to, but not always collocated with, regions of warm water, there is a large reduction of OLR with respect to SST associated with increase in deep convection. The rate of OLR reduction is found to be a strong function of the large-scale motion field. The authors find an intrinsic OLR sensitivity to SST of approximately −4 to −5 Wm−2 (°C)−1 in the SST range of 27°–28°C, under conditions of weak large-scale circulation. Under the influence of strong ascending motion, the rate can be increased to −15 to −20 Wm−2 (°C)−1 for the same SST range. The above OLR–SST relationships are stron...

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