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Title: Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations

Abstract

Abstract Two isolated deep convective clouds (DCCs) that developed in clean-humid and polluted-dry air masses, observed during the TWP-ICE and ACTIVE campaigns, are simulated using a 3-dimensional cloud-resolving model with size-resolved aerosol and cloud microphysics. We examine the impacts of different homogeneous and immersion freezing parameterizations on the anvil characteristics and the water vapor content (WVC) in the Tropical Tropopause Layer (TTL) for the two DCCs that developed in contrasting environments. The modeled cloud properties such as liquid/ice water path and precipitation generally agree with the available radar and satellite retrievals and in situ aircraft measurements. We find that anvil size and anvil microphysical properties such as ice number concentration and ice effective radius (rei) are much more sensitive to the homogeneous freezing parameterization (HomFP) under the polluted-dry condition, while the strength of anvil convection is more sensitive to HomFP under the clean-humid condition. Specifically, the cloud anvil with the Koop et al. (2000) (KOOP) relative humidity dependent scheme has up to 2 and 4 times lower ice number than those with other schemes (temperature dependent) for the clean humid and polluted-dry cases, respectively. Consequently, the rei is increased in both cases, with a larger increase in the polluted-dry case.more » As a result, extinction coefficient of cloud anvils is reduced by over 25% for the polluted-dry case. Anvil size and evolution are also much affected by HomFPs in the polluted-dry case. Higher immersion-freezing rates leads to a stronger convective cloud, with higher precipitation and ice water path under both humid and dry conditions. As a result, homogeneous freezing rates are enhanced by over 20%. Also, the higher immersion-freezing rate results in stronger convection in cloud anvils, much larger anvil size (up to 3 times) and longer lifetime. The moistening effect of deep convection on the WVC in the TTL is very significant with a increase of more than 2 times. Homogeneous freezing parameterizations do not significantly change the WVC in the TTL, but higher immersion freezing rate leads to an increase in TTL WVC by enhancing convection.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
982550
Report Number(s):
PNNL-SA-67055
25701; TRN: US201014%%341
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research. D. (Atmospheres), 115:D12201
Additional Journal Information:
Journal Volume: 115
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AEROSOLS; CLOUDS; CONVECTION; FREEZING; HUMIDITY; RADAR; TROPOPAUSE; WATER VAPOR; TROPICAL REGIONS; MATHEMATICAL MODELS; Tropical Anvil Characteristics; Water Vapor; Tropical Tropopause Layer; TTL; Heterogeneous; Homogeneous; Environmental Molecular Sciences Laboratory

Citation Formats

Fan, Jiwen, Comstock, Jennifer M, Ovchinnikov, Mikhail, McFarlane, Sally A, McFarquhar, Greg, and Allen, Grant. Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations. United States: N. p., 2010. Web. doi:10.1029/2009JD012696.
Fan, Jiwen, Comstock, Jennifer M, Ovchinnikov, Mikhail, McFarlane, Sally A, McFarquhar, Greg, & Allen, Grant. Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations. United States. https://doi.org/10.1029/2009JD012696
Fan, Jiwen, Comstock, Jennifer M, Ovchinnikov, Mikhail, McFarlane, Sally A, McFarquhar, Greg, and Allen, Grant. 2010. "Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations". United States. https://doi.org/10.1029/2009JD012696.
@article{osti_982550,
title = {Tropical anvil characteristics and water vapor of the tropical tropopause layer: Impact of heterogeneous and homogeneous freezing parameterizations},
author = {Fan, Jiwen and Comstock, Jennifer M and Ovchinnikov, Mikhail and McFarlane, Sally A and McFarquhar, Greg and Allen, Grant},
abstractNote = {Abstract Two isolated deep convective clouds (DCCs) that developed in clean-humid and polluted-dry air masses, observed during the TWP-ICE and ACTIVE campaigns, are simulated using a 3-dimensional cloud-resolving model with size-resolved aerosol and cloud microphysics. We examine the impacts of different homogeneous and immersion freezing parameterizations on the anvil characteristics and the water vapor content (WVC) in the Tropical Tropopause Layer (TTL) for the two DCCs that developed in contrasting environments. The modeled cloud properties such as liquid/ice water path and precipitation generally agree with the available radar and satellite retrievals and in situ aircraft measurements. We find that anvil size and anvil microphysical properties such as ice number concentration and ice effective radius (rei) are much more sensitive to the homogeneous freezing parameterization (HomFP) under the polluted-dry condition, while the strength of anvil convection is more sensitive to HomFP under the clean-humid condition. Specifically, the cloud anvil with the Koop et al. (2000) (KOOP) relative humidity dependent scheme has up to 2 and 4 times lower ice number than those with other schemes (temperature dependent) for the clean humid and polluted-dry cases, respectively. Consequently, the rei is increased in both cases, with a larger increase in the polluted-dry case. As a result, extinction coefficient of cloud anvils is reduced by over 25% for the polluted-dry case. Anvil size and evolution are also much affected by HomFPs in the polluted-dry case. Higher immersion-freezing rates leads to a stronger convective cloud, with higher precipitation and ice water path under both humid and dry conditions. As a result, homogeneous freezing rates are enhanced by over 20%. Also, the higher immersion-freezing rate results in stronger convection in cloud anvils, much larger anvil size (up to 3 times) and longer lifetime. The moistening effect of deep convection on the WVC in the TTL is very significant with a increase of more than 2 times. Homogeneous freezing parameterizations do not significantly change the WVC in the TTL, but higher immersion freezing rate leads to an increase in TTL WVC by enhancing convection.},
doi = {10.1029/2009JD012696},
url = {https://www.osti.gov/biblio/982550}, journal = {Journal of Geophysical Research. D. (Atmospheres), 115:D12201},
number = ,
volume = 115,
place = {United States},
year = {Wed Jun 16 00:00:00 EDT 2010},
month = {Wed Jun 16 00:00:00 EDT 2010}
}