19 Mar 2021

19 Mar 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

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

Alice Henkes1,4, Gilberto Fisch1,2, Luiz Augusto Toledo Machado1,3, and Jean-Pierre Chaboureau4 Alice Henkes et al.
  • 1National Institute for Space Research, Cachoeira Paulista, São Paulo, Brazil
  • 2Universidade de Taubaté (UNITAU), Taubaté – São Paulo, Brazil
  • 3Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 4Laboratoire d'Aérologie, Université de Toulouse, CNRS, UPS, Toulouse, France

Abstract. Observations of the boundary layer (BL) processes are analyzed in four shallow convective days (ShCu) and four shallow-to-deep convective days (ShDeep) using a suite of ground-based measurements from the second Intensive Operating Period as part of the Observation and Modeling of the Green Ocean Amazon (IOP2; 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. Atmosphere thermodynamics and dynamics, environmental profiles, and surface 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 duration of the morning transition on ShDeep days decreases under high humidity and intense vertical wind shear. 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 large sensible heat flux in the early morning. A large sensible heat flux promotes rapid growth of the well-mixed layer, thus favoring the deeper BL starting from around 08:00 LST. Under these conditions, turbulent mixing provides a lifting mechanism by which air parcels reach the lifting condensation level, leading to the formation of shallow cumulus clouds and their subsequent evolution into deep convective clouds.

Alice Henkes et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-87', Anonymous Referee #1, 17 Apr 2021
    • AC1: 'Reply on RC1', Alice Henkes, 26 Jun 2021
  • RC2: 'Comment on acp-2021-87', Anonymous Referee #2, 21 Apr 2021
    • AC2: 'Reply on RC2', Alice Henkes, 26 Jun 2021

Alice Henkes et al.

Alice Henkes et al.


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Latest update: 01 Aug 2021
Short summary
The Amazonian boundary layer is investigated during the dry season in order to better understand the processes that occur between night and day until the stage where shallow cumulus clouds become deep. Observations show that shallow-to-deep clouds are characterized by a shorter morning transition stage (e.g. the time needed to eliminate the stable boundary layer inversion) while higher humidity above the boundary layer favors the evolution from shallow to deep cumulus clouds.