Abstract
The near-surface characteristics of approximately 300 convective cold pools over the equatorial Indian Ocean are studied using surface meteorological variables from two equatorial Indian Ocean sites, radar imagery, and constrained cloud-resolving simulations. The observed temperature drop at cold pool onset is typically accompanied by a drying and a decrease in moist static energy, signifying air transport from above the boundary layer through precipitation-induced downdrafts. The decrease in the surface water vapor mixing ratio is more pronounced for stronger temperature drops. Composites reveal a slight enhancement in moisture coincident with a slight enhancement in temperature prior to the cold pool frontal temperature drop. The slight enhancements occur prior to a gust of increased surface winds, suggesting that the immediate cause is wind convergence. A statistical analysis combined with a focus on selected case studies is consistent with a view that the strongest cold pools occur in intermediate column water vapor paths with drier midtropospheres. Such conditions are more likely to occur during convectively suppressed phases of the Madden-Julian Oscillation, when cold pool mesoscale organization facilitates the ability of cumulus congestus to reach the middle troposphere. Cold pools thus help explain why tropical cumulus congestus are common. Cloud-resolving simulations capture realistic rain rates and surface wind changes (and thereby surface fluxes). The evolution in the model near-surface moisture field is unrealistic, however, with an erroneous moisture enhancement inside the cold pool edge that is attributed to rain evaporation. This supports a further focus on the model representation of cold pool frontal dynamics and mixing.
| Original language | English (US) |
|---|---|
| Journal | Journal of Geophysical Research: Atmospheres |
| DOIs | |
| State | Accepted/In press - Jan 1 2018 |
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Keywords
- cold pools
- convection
- DYNAMO
- Indian Ocean
- MJO
ASJC Scopus subject areas
- Geophysics
- Forestry
- Oceanography
- Aquatic Science
- Ecology
- Water Science and Technology
- Soil Science
- Geochemistry and Petrology
- Earth-Surface Processes
- Atmospheric Science
- Space and Planetary Science
- Earth and Planetary Sciences (miscellaneous)
- Palaeontology
Cite this
Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud-Resolving Simulations. / Chandra, Arunchandra S.; Zuidema, Paquita; Krueger, Steven; Kochanski, Adam; de Szoeke, Simon P.; Zhang, Jianhao.
In: Journal of Geophysical Research: Atmospheres, 01.01.2018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud-Resolving Simulations
AU - Chandra, Arunchandra S.
AU - Zuidema, Paquita
AU - Krueger, Steven
AU - Kochanski, Adam
AU - de Szoeke, Simon P.
AU - Zhang, Jianhao
PY - 2018/1/1
Y1 - 2018/1/1
N2 - The near-surface characteristics of approximately 300 convective cold pools over the equatorial Indian Ocean are studied using surface meteorological variables from two equatorial Indian Ocean sites, radar imagery, and constrained cloud-resolving simulations. The observed temperature drop at cold pool onset is typically accompanied by a drying and a decrease in moist static energy, signifying air transport from above the boundary layer through precipitation-induced downdrafts. The decrease in the surface water vapor mixing ratio is more pronounced for stronger temperature drops. Composites reveal a slight enhancement in moisture coincident with a slight enhancement in temperature prior to the cold pool frontal temperature drop. The slight enhancements occur prior to a gust of increased surface winds, suggesting that the immediate cause is wind convergence. A statistical analysis combined with a focus on selected case studies is consistent with a view that the strongest cold pools occur in intermediate column water vapor paths with drier midtropospheres. Such conditions are more likely to occur during convectively suppressed phases of the Madden-Julian Oscillation, when cold pool mesoscale organization facilitates the ability of cumulus congestus to reach the middle troposphere. Cold pools thus help explain why tropical cumulus congestus are common. Cloud-resolving simulations capture realistic rain rates and surface wind changes (and thereby surface fluxes). The evolution in the model near-surface moisture field is unrealistic, however, with an erroneous moisture enhancement inside the cold pool edge that is attributed to rain evaporation. This supports a further focus on the model representation of cold pool frontal dynamics and mixing.
AB - The near-surface characteristics of approximately 300 convective cold pools over the equatorial Indian Ocean are studied using surface meteorological variables from two equatorial Indian Ocean sites, radar imagery, and constrained cloud-resolving simulations. The observed temperature drop at cold pool onset is typically accompanied by a drying and a decrease in moist static energy, signifying air transport from above the boundary layer through precipitation-induced downdrafts. The decrease in the surface water vapor mixing ratio is more pronounced for stronger temperature drops. Composites reveal a slight enhancement in moisture coincident with a slight enhancement in temperature prior to the cold pool frontal temperature drop. The slight enhancements occur prior to a gust of increased surface winds, suggesting that the immediate cause is wind convergence. A statistical analysis combined with a focus on selected case studies is consistent with a view that the strongest cold pools occur in intermediate column water vapor paths with drier midtropospheres. Such conditions are more likely to occur during convectively suppressed phases of the Madden-Julian Oscillation, when cold pool mesoscale organization facilitates the ability of cumulus congestus to reach the middle troposphere. Cold pools thus help explain why tropical cumulus congestus are common. Cloud-resolving simulations capture realistic rain rates and surface wind changes (and thereby surface fluxes). The evolution in the model near-surface moisture field is unrealistic, however, with an erroneous moisture enhancement inside the cold pool edge that is attributed to rain evaporation. This supports a further focus on the model representation of cold pool frontal dynamics and mixing.
KW - cold pools
KW - convection
KW - DYNAMO
KW - Indian Ocean
KW - MJO
UR - http://www.scopus.com/inward/record.url?scp=85055697931&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85055697931&partnerID=8YFLogxK
U2 - 10.1029/2018JD028634
DO - 10.1029/2018JD028634
M3 - Article
AN - SCOPUS:85055697931
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
SN - 2169-9275
ER -