Banca de DEFESA: GUSTAVO SILVA XAVIER

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GUSTAVO SILVA XAVIER
DATE: 05/03/2026
TIME: 09:00
LOCAL: Laboratório de Informática/Remoto
TITLE:

Analysis Of Nocturnal Turbulence Regime Transitions At An Experimental Site In The Caatinga Biome

 

KEY WORDS:

Nocturnal boundary layer, Turbulence, Regime transition

PAGES: 78
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Meteorologia
SPECIALTY: Micrometeorologia
SUMMARY:

Understanding the processes that regulate scalar exchanges, such as CO2 and H2O, between the surface and the atmosphere under nocturnal stable conditions remains one of the main challenges in boundary-layer meteorology. Flux estimates obtained using the eddy covariance method often present significant uncertainties under these conditions, compromising the closure of mass and energy budgets in the nocturnal boundary layer. A central aspect of this problem is the occurrence of turbulence regime transitions, in which turbulence intensity changes abruptly, substantially modifying the dynamics of scalar exchanges between the surface, vegetation, and the atmosphere. This dissertation investigates transitions between weakly stable and very stable turbulent regimes at an experimental site located in the Caatinga biome, within the Açu National Forest (RN), Brazil. Based on the relationship between wind speed (V) and the potential temperature gradient (Δθ), the influence of different regimes on thermal stratification and surface fluxes measured above and below the canopy was analyzed. The relative contribution of turbulent and non-turbulent motions was evaluated using the multiresolution decomposition technique. Additionally, the relationship between V and net radiation (Rn), as well as the determination of a limiting wind speed (VL) based on the flux Richardson number (Rif = 2), were investigated as tools to identify regime transitions. The results indicate that the very stable regime is associated with increased thermal instability within the canopy, resulting from strong radiative cooling at the canopy top and adjacent levels. Non-turbulent scales were found to play a more significant role under very stable conditions, with evidence of enhanced vertical propagation of these motions within the canopy. Both the V × Rn relationship and the estimation of VL based on Rif = 2 proved to be consistent indicators of regime transitions at the Açu National Forest site.

COMMITTEE MEMBERS:
Presidente - 1753398 - PABLO ELI SOARES DE OLIVEIRA
Interno - 2086472 - BERGSON GUEDES BEZERRA
Interno - 1752417 - CLAUDIO MOISES SANTOS E SILVA
Externo à Instituição - FELIPE DENARDIN COSTA - Unipampa