Transição de regimes da camada limite estável utilizando um modelo conceitual

Abstract

The behavior of the Atmospheric Boundary Layer (ABL) becomes particularly complex during nighttime. At night, due to stable stratification, flow turbulence can be suppressed, leading to the decoupling of atmospheric layers. This regime transition within the Stable Boundary Layer (SBL) poses a modeling challenge due to the difficulties in understanding and accurately reproducing these transitions. To investigate the role of surface energy ba lance in SBL transitions, a simplified conceptual model was used, consisting of a differential equation to determine surface temperature. Turbulent fluxes were parameterized using K-theory, and two stability functions, the Long-Tail Stability Function and Short-Tail Stability Function, were used to represent the relationship between turbulent mixing and local stratification. Simulations were conducted using different configurations by varying external parameters such as cloud fraction (qc), heat capacity per unit area (Cg), substrate temperature (θsub), surface roughness (z0), and local wind speed. Results indicate that surface roughness and cloud cover directly influence SBL regime transitions: increases in these variables reduce the wind speed necessary for regime transition. The role of soil thermal capacity per unit area, however, depends on the substrate temperature. When substrate temperature is low relative to air temperature, increased heat capacity raises the transition speed (Vr); conversely, when substrate temperature is close to or higher than air temperature, higher heat capacity reduces the speed needed for the transition. The results also show that the model reproduces regime transitions independently of the stability function used; however, the relationship between wind speed and radiation balance is well represented when substrate temperature exceeds air temperature. Nevertheless, further detailed analysis is required to identify the conditions under which the SBL transition speed is proportional to the surfasse radiation balance.

Keywords: stable boundary layer, regime transition, atmospheric modeling.