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Abstract While it has been established that pronounced sea-breeze fronts (SBFs) develop under conditions of weak or offshore flow, with the SBF serving as a focus for convection initiation (CI), less is known regarding CI processes during large-scale onshore flow, including the potential existence and influence of embedded SBFs. Challenges that have limited progress in addressing this question include the limited focus on cases under this flow regime and the coarse grid spacing used in prior model-based parameter studies, artificially decreasing the magnitude of convergence or thermodynamic gradients associated with the SBF and potentially leading to substantial errors in the representation of surface fluxes. In Part II of this two-part series, the authors address these prior challenges through execution of a suite of Cloud Model 1 (CM1) large-eddy simulations analyzing the impact of varying the magnitude of the onshore wind component (+2.5 and +5.0 m s−1), and radiative forcing and water surface temperature consistent for summertime in the Great Lakes region. In all simulations, a mesoscale enhancement of onshore flow and return flow was present, with a thermal gradient and convergence collocated with the leading edge of this enhanced flow providing evidence for the presence of a diffuse yet discernible SBF. The SBF progressed inland and separated areas where CI did and did not occur, highlighting the need for increased focus on SBFs and CI in this less-studied flow regime. In conditions of weak onshore flow, surface-based CAPE was larger, CI was more common, and it occurred closer to the coast.
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This content will become publicly available on March 1, 2026
An Idealized Parameter Study of Destabilization and Convection Initiation in Coastal Regions. Part I: Calm or Offshore Synoptic-Scale Flow
Abstract The influence of large bodies of water on convection initiation (CI) and the environment in which convection evolves is highly complex due to the wide range of parameters that control relevant processes. A substantial focus of sea-breeze front (SBF) CI research has focused on the role of mesoscale boundary or organized boundary layer circulation interactions with SBFs; however, less research has focused on heterogeneities in convective parameters and how those may affect CI coverage, timing, and location. In this two-part series, the authors present a parameter study of SBF CI through Cloud Model 1 (CM1) large-eddy simulations across a parameter space varying the cross-shore wind component and radiative forcing and water surface temperatures consistent with June, July, and August in the Great Lakes region. In Part I of this series, simulations under conditions of calm, weak, and moderate offshore flow (0, −2.5, and −5.0 m s−1) are presented. CI occurred in all calm simulations, with decreased coverage and frequency of CI in weak offshore flow. CI was least frequent during moderate offshore flow, despite stronger convergence, due to a shear profile that favored undercutting by the SBF under conditions of moderate offshore flow. Surface-based convective available potential energy (SBCAPE) maxima developed on the cool side of the SBF, with convection occurring on the cool side of the SBF in some cases. Analyses are presented with a focus on the nature of the SBF, distribution of convective parameters, and their implications on CI.
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- Award ID(s):
- 2113324
- PAR ID:
- 10620725
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of the Atmospheric Sciences
- Volume:
- 82
- Issue:
- 3
- ISSN:
- 0022-4928
- Page Range / eLocation ID:
- 519 to 539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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