04 Oct 2022
 | 04 Oct 2022

Seasonal Controls on Isolated Convective Storm Drafts, Precipitation Intensity, and Life Cycle As Observed During GoAmazon2014/5

Scott E. Giangrande, Thiago Biscaro, and John M. Peters

Abstract. Isolated deep convective cloud life cycle and seasonal changes in storm properties are observed for daytime events during the DOE-ARM 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.

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 to wet season cells. These cells exhibited updrafts in core precipitation regions (Z > 35 dBZ) to above the melting level, and persistent downdrafts aloft within precipitation adjacent to their cores. Moreover, dry season cells recorded more intense updrafts to earlier life cycle stages, and a higher incidence of strong updrafts (i.e., > 5 m/s) at low levels. In contrast, wet season storms were longer-lived and featured a higher incidence of moderate (i.e., 2–5 m/s) updrafts aloft. These storms also favored a shift in their most intense properties to later life cycle stages. Strong downdrafts were far less frequent within wet season cells aloft, indicating a potential systematic difference in downdraft behaviors 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. The enhanced dry season downdrafts are attributed to increased evaporation, dry air entrainment-mixing, and negative buoyancy in regions adjacent to sampled dry season cores.

Scott E. Giangrande et al.

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  • RC1: 'Comment on egusphere-2022-877', Anonymous Referee #1, 11 Nov 2022
  • RC2: 'Comment on egusphere-2022-877', Anonymous Referee #2, 18 Nov 2022

Scott E. Giangrande et al.

Scott E. Giangrande et al.


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Short summary
Our study tracks thunderstorms observed during the wet and dry seasons of the Amazon basin using weather radar. We couple this precipitation tracking with opportunistic overpasses of a wind profiler and other ground observations to add unique insights into the upward and downward air motions within these clouds at various stages in the storm life cycle. The results of a simple updraft model are provided to give physical explanations for observed seasonal differences.