THE CONVECTIVE BOUNDARY LAYER IN THE AMAZON RAINFOREST
Open Access
- Author:
- Monteiro, Vanessa Caroline
- Graduate Program:
- Meteorology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 22, 2018
- Committee Members:
- Jose Dolores Fuentes, Thesis Advisor/Co-Advisor
Jerry Y Harrington, Committee Member
Gregory S Jenkins, Committee Member - Keywords:
- Convective boundary layer
Amazon rainforest
Mesoscale convective system - Abstract:
- Among all the interactions in nature - between water, soil, atmosphere, and living beings - this work will be focused on quantifying a very specific one: the thermodynamics of the convective boundary layer preceding and following the passage of mesoscale convective systems (MCSs) in the Amazon rainforest. Over the Amazon basin, the warm and moist conditions favor the formation of mesoscale convective systems, which are constantly modifying the atmospheric features, such as the thermodynamics (e.g., temperature and humidity) and dynamics (e.g., wind shear). Then, the objectives of this work are: quantify the thermodynamic features of the convective boundary layer (e.g., temperature, humidity, convective available potential energy, and energy fluxes) before and after the passage of mesoscale convective systems over the Amazon rainforest; determine the convective boundary layer growth rates before and after such events (MCSs); and, determine the mixed-layer depth using a numerical model. Using the data set provided by the most recent experiment - GoAmazon 2014/15 - this study will address its objectives through the evaluation of case studies and an ensemble of days when there was the passage of mesoscale convective systems. The variables evaluated, such as equivalent potential temperature, specific humidity, and energy fluxes are estimated based on the surface measurements, and the convective boundary layer depth is estimated using the virtual potential temperature profile, obtained from the soundings launched during the experiment. The results show that the convective boundary layer experiences reductions in the equivalent potential temperature within 2 to 8 K and in the specific humidity up to 2 g/kg after the passage of a MCS, due to the cold and dry air brought to the surface by storms downdrafts. These two variables in addition to others (e.g., energy fluxes) are responsible for the low growth rates of the convective boundary layer, that were reduced by 100 m h−1 in the following two hours after the rainfall ceases - when compared to undisturbed conditions. Also, the mixed-layer model applied to predict the convective boundary layer growth during disturbed conditions showed a poor performance, that can be linked to the absence of the dynamic features that impact the CBL growth, such as subsidence. Nonetheless, this work provides a better quantitative evaluation of the thermodynamic features of the convective boundary layer under the passage of mesoscale convective systems in the Amazon rainforest, and proposes a set of different perspectives for future studies.