Seasonal controls on isolated convective storm drafts, precipitation intensity, and life cycle as observed during GoAmazon2014/5
<p>Isolated deep convective cloud life cycle and seasonal changes in storm properties are observed for daytime events during the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Green Ocean Amazon Experiment (GoAmazon2014/5) campaign to understand controls on storm behavio...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2023-05-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://acp.copernicus.org/articles/23/5297/2023/acp-23-5297-2023.pdf |
Summary: | <p>Isolated deep convective cloud life cycle and seasonal
changes in storm properties are observed for daytime events during the
US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Green Ocean Amazon Experiment (GoAmazon2014/5) campaign to understand controls on storm behavior.
Storm life cycles are documented using surveillance radar from initiation
through maturity and dissipation. Vertical air velocity estimates are
obtained from radar wind profiler overpasses, with the storm environment
informed by radiosondes.</p>
<p>Dry-season storm conditions favored reduced morning shallow cloud coverage
and larger low-level convective available potential energy (CAPE) than wet-season counterparts. The typical dry-season storm reached its peak intensity
and size earlier in its life cycle compared with wet-season cells. These cells
exhibited updrafts in core precipitation regions (<span class="inline-formula"><i>Z</i>>35</span> dBZ) to
above the melting level as well as persistent downdrafts aloft within
precipitation adjacent to their cores. Moreover, dry-season cells recorded
more intense updrafts to earlier life cycle stages as well as a higher incidence
of strong updrafts (i.e., <span class="inline-formula">>5</span> m s<span class="inline-formula"><sup>−1</sup>)</span> at low levels. In
contrast, wet-season storms were longer-lived and featured a higher
incidence of moderate (i.e., 2–5 m s<span class="inline-formula"><sup>−1</sup>)</span> updrafts aloft. These storms
also favored a shift in their most intense properties to later life cycle
stages. Strong downdrafts were less frequent within wet-season cells aloft,
indicating a potential systematic difference in draft behaviors, as linked
to graupel loading and other factors between the seasons. Results from a
stochastic parcel model suggest that dry-season cells may expect stronger
updrafts at low levels because of larger low-level CAPE in the dry season.
Wet-season cells anticipate strong updrafts aloft because of larger
free-tropospheric relative humidity and reduced entrainment-driven dilution.
Enhanced dry-season downdrafts are partially attributed to increased
evaporation, dry-air entrainment mixing, and negative buoyancy in regions
adjacent to sampled dry-season cores.</p> |
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ISSN: | 1680-7316 1680-7324 |