Supersaturation, buoyancy, and deep convection dynamics
<p>Motivated by recent discussions concerning differences of convective dynamics in polluted and pristine environments, the so-called convective invigoration in particular, this paper provides an analysis of factors affecting convective updraft buoyancy, such as the in-cloud supersaturation, c...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/13997/2021/acp-21-13997-2021.pdf |
| _version_ | 1819133493458763776 |
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| author | W. W. Grabowski H. Morrison |
| author_facet | W. W. Grabowski H. Morrison |
| author_sort | W. W. Grabowski |
| collection | DOAJ |
| description | <p>Motivated by recent discussions concerning differences of convective dynamics in polluted and pristine environments, the so-called convective
invigoration in particular, this paper provides an analysis of factors affecting convective updraft buoyancy, such as the in-cloud supersaturation,
condensate and precipitation loading, and entrainment. We use the deep convective period from simulations of daytime convection development over
land discussed in our previous publications. An entraining parcel framework is used in the theoretical analysis. We show that for the specific case
considered here, finite (positive) supersaturation noticeably reduces pseudo-adiabatic parcel buoyancy and cumulative convective available potential energy (cCAPE) in the lower
troposphere. This comes from keeping a small fraction of the water vapor in a supersaturated state and thus reducing the latent heating. Such a
lower-tropospheric impact is comparable to the effects of condensate loading and entrainment in the idealized parcel framework. For the entire
tropospheric depth, loading and entrainment have a much more significant impact on the total CAPE. For the cloud model results, we compare ensemble
simulations applying either a bulk microphysics scheme with saturation adjustment or a more comprehensive double-moment scheme with supersaturation
prediction. We compare deep convective updraft velocities, buoyancies, and supersaturations from all ensembles. In agreement with the parcel
analysis, the saturation-adjustment scheme provides noticeably stronger updrafts in the lower troposphere. For the simulations predicting
supersaturation, there are small differences between pristine and polluted conditions below the freezing level that are difficult to explain by
standard analysis of the in-cloud buoyancy components. By applying the piggybacking technique, we show that the lower-tropospheric buoyancy
differences between pristine and polluted simulations come from a combination of temperature (i.e., latent heating) and condensate loading
differences that work together to make polluted buoyancies and updraft velocities slightly larger when compared to their pristine
analogues. Overall, the effects are rather small and contradict previous claims of a significant invigoration of deep convection in polluted
environments.</p> |
| first_indexed | 2024-12-22T09:48:10Z |
| format | Article |
| id | doaj.art-d3633cca951044f58ac442882cce9b3c |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-22T09:48:10Z |
| publishDate | 2021-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-d3633cca951044f58ac442882cce9b3c2022-12-21T18:30:29ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242021-09-0121139971401810.5194/acp-21-13997-2021Supersaturation, buoyancy, and deep convection dynamicsW. W. GrabowskiH. Morrison<p>Motivated by recent discussions concerning differences of convective dynamics in polluted and pristine environments, the so-called convective invigoration in particular, this paper provides an analysis of factors affecting convective updraft buoyancy, such as the in-cloud supersaturation, condensate and precipitation loading, and entrainment. We use the deep convective period from simulations of daytime convection development over land discussed in our previous publications. An entraining parcel framework is used in the theoretical analysis. We show that for the specific case considered here, finite (positive) supersaturation noticeably reduces pseudo-adiabatic parcel buoyancy and cumulative convective available potential energy (cCAPE) in the lower troposphere. This comes from keeping a small fraction of the water vapor in a supersaturated state and thus reducing the latent heating. Such a lower-tropospheric impact is comparable to the effects of condensate loading and entrainment in the idealized parcel framework. For the entire tropospheric depth, loading and entrainment have a much more significant impact on the total CAPE. For the cloud model results, we compare ensemble simulations applying either a bulk microphysics scheme with saturation adjustment or a more comprehensive double-moment scheme with supersaturation prediction. We compare deep convective updraft velocities, buoyancies, and supersaturations from all ensembles. In agreement with the parcel analysis, the saturation-adjustment scheme provides noticeably stronger updrafts in the lower troposphere. For the simulations predicting supersaturation, there are small differences between pristine and polluted conditions below the freezing level that are difficult to explain by standard analysis of the in-cloud buoyancy components. By applying the piggybacking technique, we show that the lower-tropospheric buoyancy differences between pristine and polluted simulations come from a combination of temperature (i.e., latent heating) and condensate loading differences that work together to make polluted buoyancies and updraft velocities slightly larger when compared to their pristine analogues. Overall, the effects are rather small and contradict previous claims of a significant invigoration of deep convection in polluted environments.</p>https://acp.copernicus.org/articles/21/13997/2021/acp-21-13997-2021.pdf |
| spellingShingle | W. W. Grabowski H. Morrison Supersaturation, buoyancy, and deep convection dynamics Atmospheric Chemistry and Physics |
| title | Supersaturation, buoyancy, and deep convection dynamics |
| title_full | Supersaturation, buoyancy, and deep convection dynamics |
| title_fullStr | Supersaturation, buoyancy, and deep convection dynamics |
| title_full_unstemmed | Supersaturation, buoyancy, and deep convection dynamics |
| title_short | Supersaturation, buoyancy, and deep convection dynamics |
| title_sort | supersaturation buoyancy and deep convection dynamics |
| url | https://acp.copernicus.org/articles/21/13997/2021/acp-21-13997-2021.pdf |
| work_keys_str_mv | AT wwgrabowski supersaturationbuoyancyanddeepconvectiondynamics AT hmorrison supersaturationbuoyancyanddeepconvectiondynamics |