Skip to Main content Skip to Navigation
New interface
Journal articles

Morning boundary layer conditions for shallow to deep convective cloud evolution during the dry season in the central Amazon

Abstract : Observations of the boundary layer (BL) processes are analyzed statistically for dry seasons of 2 years and in detail, as case studies, for 4 shallow convective days (ShCu) and 4 shallow-to-deep convective days (ShDeep) using a suite of ground-based measurements from the Observation and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment. The BL stages in ShDeep days, from the nighttime to the cloudy mixing layer stage, are then described in comparison with ShCu days. Atmospheric thermodynamics and dynamics, environmental profiles, and surface turbulent fluxes were employed to compare these two distinct situations for each stage of the BL evolution. Particular attention is given to the morning transition stage, in which the BL changes from stable to unstable conditions in the early morning hours. Results show that the decrease in time duration of the morning transition on ShDeep days is associated with high humidity and well-established vertical wind shear patterns. Higher humidity since nighttime not only contributes to lowering the cloud base during the rapid growth of the BL but also contributes to the balance between radiative cooling and turbulent mixing during nighttime, resulting in higher sensible heat flux in the early morning. The sensible heat flux promotes rapid growth of the well-mixed layer, thus favoring the deeper BL starting from around 08:00 LST (UTC−4 h). Under these conditions, the time duration of morning transition is used to promote convection, having an important effect on the convective BL strength and leading to the formation of shallow cumulus clouds and their subsequent evolution into deep convective clouds. Statistical analysis was used to validate the conceptual model obtained from the case studies. Despite the case-to-case variability, the statistical analyses of the processes in the BL show that the described processes are very representative of cloud evolution during the dry season.
Document type :
Journal articles
Complete list of metadata

https://hal-insu.archives-ouvertes.fr/insu-03671632
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Thursday, May 19, 2022 - 8:27:13 AM
Last modification on : Wednesday, November 16, 2022 - 11:46:08 AM

File

acp-21-13207-2021.pdf
Publisher files allowed on an open archive

Licence


Distributed under a Creative Commons Attribution 4.0 International License

Identifiers

Collections

Citation

Alice Henkes, Gilberto Fisch, Luiz A. T. Machado, Jean-Pierre Chaboureau. Morning boundary layer conditions for shallow to deep convective cloud evolution during the dry season in the central Amazon. Atmospheric Chemistry and Physics, 2021, 21, pp.13207-13225. ⟨10.5194/acp-21-13207-2021⟩. ⟨insu-03671632⟩

Share

Metrics

Record views

16

Files downloads

4