How do changes in warm-phase microphysics affect deep convective clouds?
Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/9585/2017/acp-17-9585-2017.pdf |
| _version_ | 1818259171377676288 |
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| author | Q. Chen Q. Chen I. Koren O. Altaratz R. H. Heiblum G. Dagan L. Pinto |
| author_facet | Q. Chen Q. Chen I. Koren O. Altaratz R. H. Heiblum G. Dagan L. Pinto |
| author_sort | Q. Chen |
| collection | DOAJ |
| description | Understanding aerosol effects on deep convective
clouds and the derived effects on the radiation budget and rain patterns can
largely contribute to estimations of climate uncertainties. The challenge is
difficult in part because key microphysical processes in the mixed and cold
phases are still not well understood. For deep convective clouds with a warm
base, understanding aerosol effects on the warm processes is extremely
important as they set the initial and boundary conditions for the cold
processes. Therefore, the focus of this study is the warm phase, which can
be better resolved. The main question is: <q>How do aerosol-derived changes in
the warm phase affect the properties of deep convective cloud systems?</q> To
explore this question, we used a weather research and forecasting (WRF)
model with spectral bin microphysics to simulate a deep convective cloud
system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The
model results were validated against observations, showing similarities in
the vertical profile of radar reflectivity and the surface rain rate.
Simulations with larger aerosol loading resulted in a larger total cloud
mass, a larger cloud fraction in the upper levels, and a larger frequency of
strong updrafts and rain rates. Enlarged mass both below and above the zero
temperature level (ZTL) contributed to the increase in cloud total mass
(water and ice) in the polluted runs. Increased condensation efficiency of
cloud droplets governed the gain in mass below the ZTL, while both enhanced
condensational and depositional growth led to increased mass above it. The
enhanced mass loading above the ZTL acted to reduce the cloud buoyancy,
while the thermal buoyancy (driven by the enhanced latent heat release)
increased in the polluted runs. The overall effect showed an increased upward
transport (across the ZTL) of liquid water driven by both larger updrafts
and larger droplet mobility.
<br><br>
These aerosol effects were reflected in the larger ratio between the masses
located above and below the ZTL in the polluted runs. When comparing the net
mass flux crossing the ZTL in the clean and polluted runs, the difference
was small. However, when comparing the upward and downward fluxes
separately, the increase in aerosol concentration was seen to dramatically
increase the fluxes in both directions, indicating the aerosol amplification
effect of the convection and the affected cloud system properties, such as cloud
fraction and rain rate. |
| first_indexed | 2024-12-12T18:11:12Z |
| format | Article |
| id | doaj.art-669e6fffeecc4429ba7a6a29de05b8c2 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T18:11:12Z |
| publishDate | 2017-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-669e6fffeecc4429ba7a6a29de05b8c22022-12-22T00:16:22ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-08-01179585959810.5194/acp-17-9585-2017How do changes in warm-phase microphysics affect deep convective clouds?Q. Chen0Q. Chen1I. Koren2O. Altaratz3R. H. Heiblum4G. Dagan5L. Pinto6Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelKey Laboratory of Meteorological Disaster, Ministry of Education (KLME); Joint International Research Laboratory of Climate and Environment Change (ILCEC); Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters; Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration; Nanjing University of Information Science and Technology, Nanjing, ChinaDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelDepartment of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, IsraelUnderstanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: <q>How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems?</q> To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. <br><br> These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.https://www.atmos-chem-phys.net/17/9585/2017/acp-17-9585-2017.pdf |
| spellingShingle | Q. Chen Q. Chen I. Koren O. Altaratz R. H. Heiblum G. Dagan L. Pinto How do changes in warm-phase microphysics affect deep convective clouds? Atmospheric Chemistry and Physics |
| title | How do changes in warm-phase microphysics affect deep convective clouds? |
| title_full | How do changes in warm-phase microphysics affect deep convective clouds? |
| title_fullStr | How do changes in warm-phase microphysics affect deep convective clouds? |
| title_full_unstemmed | How do changes in warm-phase microphysics affect deep convective clouds? |
| title_short | How do changes in warm-phase microphysics affect deep convective clouds? |
| title_sort | how do changes in warm phase microphysics affect deep convective clouds |
| url | https://www.atmos-chem-phys.net/17/9585/2017/acp-17-9585-2017.pdf |
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