Dissertation defense
Student: Jonathan Wendell Alves
Program: Meteorologia
Title: “Estimation of Evapotranspiration using the Morton-CRAE method in Cerrado and Atlantic Forest areas”
Advisor: Prof. Dr. Humberto Ribeiro da Rocha
Judging Committee:
- Prof. Dr. Humberto Ribeiro Rocha - orientador - IAG/USP
- Profa. Dr. Osvaldo Machado Rodrigues Cabral - EMBRAPA - por videoconferência
- Prof. Dr. Leonardo Moreno Domingues – pós-doutorando IAG
Abstract
Evapotranspiration (ET) is a fundamental component of the surface water balance, accounting on average for approximately 67% of the annual precipitation in the state of São Paulo, representing the greatest water loss for availability. ET estimation exhibits significant spatial variability, making its estimation marked by pronounced uncertainty for agricultural-sized areas or larger areas with different types of vegetation. This study uses the Complementary Relationship Areal Evapotranspiration (CRAE) method of Morton (Morton-CRAE) for a homogeneous area in equilibrium with the atmospheric state, a key advantage as it does not explicitly depend on surface conditions. Estimates were made for sites representative of the native vegetation of the Cerrado and Atlantic Forest biomes in southeastern Brazil and compared with field estimates at Gleba Pé de Gigante (Santa Rita do Passa Quatro) and Núcleo Santa Virgínia (São Luís do Paraitinga), respectively. Results showed high sensitivity of the method to net radiation, recommending the most accurate possible prescription of radiation in the method. Comparisons with field measurements in the Cerrado area indicated that the calculated values were very close to the overall average, with an overestimation of 0.6% (≃103 vs. 102.6 mm month⁻¹), and in monthly variation, the method exhibited an overestimation with a scaling factor of 15% and an offset of -15 W m-2. In the Atlantic Forest area, the calculations indicated an average overestimation of 19.4% (≃ 93 vs. 80 mm month⁻¹), and in monthly variation, they showed an overestimation with a scaling factor of 9% and an offset of +5 W m-2. Bouchet's hypothesis pattern was more evident in the Cerrado area, characterized by extensive variation in soil moisture, while in the Atlantic Forest, the hypothetical pattern was not well-defined due to the consistently high soil moisture throughout most of the year.
Keywords: Evapotranspiration, Morton-CRAE, Cerrado, Atlantic Forest