Evapotranspiration of the Brazilian Pampa Biome: Seasonality and Influential Factors

Abstract

Experimentally characterizing evapotranspiration (ET) in different biomes around the world is an issue of interest for different areas of science. ET in natural areas of the Brazilian Pampa biome has still not been assessed. In this study, the actual ET (ETact) obtained from eddy covariance measurements over two sites of the Pampa biome was analyzed. The objective was to evaluate the energy partition and seasonal variability of the actual ET of the Pampa biome. Results showed that the latent heat flux was the dominant component in available energy in both the autumn–winter (AW) and spring–summer (SS) periods. Evapotranspiration of the Pampa biome showed strong seasonality, with highest ET rates in the SS period. During the study period, approximately 65% of the net radiation was used for the evapotranspiration process in the Pampa biome. The annual mean ET rate was 2.45 mm d−1. ET did not show to vary significantly between sites, with daily values very similar in both sites. The water availability in the Pampa biome was not a limiting factor for ET, which resulted in a small difference between the reference ET and the actual ET. These results are helpful in achieving a better understanding of the temporal pattern of ET in relation to the landscape of the Pampa biome and its meteorological, soil, and vegetation characteristics.

Influence of submeso motions on scalar oscillations and surface energy balance

“…The global closure rate of the surface energy balance, derived from the slope of the linear fit of () versus (), is 79%. The observed imbalance is in agreement with typical values obtained at the same site (Rubert et al ., ) or in other experiments (Soltani et al ., ; Majozi et al ., ). It is noteworthy that, although the global rate does not change by applying different averaging periods, the use of a correct averaging time produces an improvement of the coefficients of determination () (from 0.76 to 0.90) and, in particular, an evident reduction in the spread of the data associated with the meandering cases.…”

“…The dataset used in the present study was obtained at the Federal University of Santa Maria (Rio Grande do Sul, Brazil) experimental site (Roberti et al ., ). The site is located in a pampa biome area of 24 ha of natural pasture, characterized by extensive and flat treeless grassland area with a shallow sandy‐loam soil (Rubert et al ., ). The data were collected from December 2015 to November 2016 on a 30 m high micrometeorological tower installed at S; W; 88 m amsl (above mean sea level).…”

“…The dataset used in the present study was obtained at the Federal University of Santa Maria (Rio Grande do Sul, Brazil) experimental site (Roberti et al, 2012). The site is located in a pampa biome area of 24 ha of natural pasture, characterized by extensive and flat treeless grassland area with a shallow sandy-loam soil (Rubert et al, 2018). Standard meteorological variables such as air temperature, T air , and relative humidity, RH, were collected by three slow-response thermo-hygrometers (HMP155-Vaisala) located above the ground at heights of 3, 9 and 30 m and sampled every 5 s from December 2015 to June 2016 and after this period each minute.…”

Evaluation of MOD16 Algorithm over Irrigated Rice Paddy Using Flux Tower Measurements in Southern Brazil

“…The EddyPro Advanced software (version 5.1, LI-COR) was used to process the flux data over half-hourly time scales. Further details of the configurations used are described in References [39,42].…”

“…Several studies show the imbalance between turbulent fluxes (H + LE) and available energy (R n − G; where R n is defined as net radiation and G is the soil heat flux) [35,37,42,49,50]. Many authors suggest the necessity of adjustment in the values of H and LE [51][52][53][54].…”