TY - JOUR
T1 - A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment
AU - Zuidema, Paquita
AU - Torri, Giuseppe
AU - Muller, Caroline
AU - Chandra, Arunchandra
N1 - Funding Information:
Acknowledgements PZ and AC gratefully acknowledge support from NOAA Climate Variability Program Grant NA13OAR4310157 and PZ from National Science Foundation grant AGS-132189. GT acknowledges support from DOE Awarrd DE-SC0018120 and NSF Grant AGS-1649819. CM gratefully acknowledges CINES/GENCI and PRACE/TGCC in France for providing access and support to their computing platforms OCCIGEN and CURIE. The satellite imagery in Fig. 1 was acquired through the NASA Worldview website. We acknowledge use of DOE ARM Mobile Facility data within Fig. 5. We are thankful to Steve Krueger and Adam Kochanski for the SAM simulation data diagnosed in Fig. 10. We thank two anonymous reviewers for input that greatly improved the manuscript. This contribution is a result of the International Space Science Institute (ISSI) Workshop on ‘‘Shallow clouds, water vapor, circulation and climate sensitivity.’’ Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Publisher Copyright:
© 2017, The Author(s).
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2017/11/1
Y1 - 2017/11/1
N2 - Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed ∼ 2 mm h- 1, convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4–5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings.
AB - Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed ∼ 2 mm h- 1, convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4–5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings.
KW - Convective cold pools
KW - Shallow cumulus convection
KW - Tropical convection
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U2 - 10.1007/s10712-017-9447-x
DO - 10.1007/s10712-017-9447-x
M3 - Article
AN - SCOPUS:85033722298
VL - 38
SP - 1283
EP - 1305
JO - Surveys in Geophysics
JF - Surveys in Geophysics
SN - 0169-3298
IS - 6
ER -