Comparison of the highly reflective cloud and outgoing longwave radiation datasets for use in estimating tropical deep convection
- Univ. of California, San Diego, La Jolla (United States)
- Univ. of California, Santa Barbara (United States)
There are two long-term satellite-derived datasets most frequently used as indices for tropical deep convection. These are the Outgoing Longwave Radiation (OLR) and Highly Reflective Cloud (HRC) datasets. Although both of these datasets have demonstrated their value, no direct comparison of these datasets has been conducted. The goal of this paper is to compare these two datasets to quantify their strengths and weaknesses. This information will provide guidance in choosing the most appropriate dataset(s) for subsequent studies, interpreting the results from those studies, and extending more modern convection datasets backward. Comparisons are done in terms of their climatological and frequency-dependent characteristics, consistency in identifying deep tropical convection, and relationships to local sea surface temperature (SST). Use is made of the more modern, shorter-term International Satellite Cloud Climatology Project stage C2 dataset as a means of further comparison and validation. The results of this study reveal some important differences between the HRC and OLR in terms of their temporal and spatial scales of variability, relationships to other geophysical fields, and the logistics of their use. For many applications the HRC more accurately represents the characteristics of cloud cluster-scale tropical convection. One important finding of this study is that both the OLR-SST and HRC-SST relationships show that SSTs in excess of about 29.5[degrees]C tend to occur only under conditions of diminished convection. The maximum convective activity does not occur over the warmest (>29.5[degrees]C) water; rather, the warmest water occurs under clear, less-convective skies. The results demonstrate that in a highly convective regime the maximum equilibrium SST that can be supported is about 29.5[degrees]C. These results are evidence that convective-cloud complexes provide a systematic and climatologically important cooling effect on the surface temperature.
- OSTI ID:
- 6577080
- Journal Information:
- Journal of Climate; (United States), Vol. 6:2; ISSN 0894-8755
- Country of Publication:
- United States
- Language:
- English
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CLIMATE MODELS
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TROPICAL REGIONS
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CLOUDS
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ATMOSPHERIC PRECIPITATIONS
ENERGY TRANSFER
EVALUATION
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