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Highlights: [•] Evapotranspiration (ET), yield and water use efficiency of castor were evaluated. [•] Variations in ET and energy exchange were mainly associated with changes in stored soil water. [•] Castor seed yield and water use efficiency were very low under limited water supply. [Copyright &y& Elsevier]

Abstract: Nighttime transpiration (NT) has been documented in many plant species but we do not yet have a thorough understanding of the abiotic and biotic controls of this phenomenon. In this study we examined interspecific variation in NT behaviors in plants with distinct crown exposures (CE) and occurring at lowland (100m) and montane forests (1000m) in the Brazilian Atlantic rainforest to answer the following questions: are there different NT behaviors in plants subjected to distinct conditions associated with degree of CE and/or altitude? Are there higher rates of NT relative to daily maximum values at the montane forest due to higher vapor pressure deficit (VPD)? Taking into account that low VPD should generally produce low relative NT fluxes, should we expect that understory species in both altitudes will have quite uniform low relative rates of NT in comparison to overstory species owing to the buffered nature of within-canopy microclimate? NT did show differences between altitude and species. Of most significance was a prominent non-linear relationship between the NT and VPD, observed at the montane site. This non-linearity is in contrast to most previously published NT kinetics and suggests stomatal and/or leaf energy balance controls on NT. Our findings raise a new perspective concerning thermodynamic contributions to non-linear NT kinetics and some possible reasons for this interesting behavior are discussed. [Copyright &y& Elsevier]

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To achieve sustainable development and to ensure water availability in hydrological basins, water managers need tools to determine the actual evapotranspiration (ET) on a large scale. Field energy balances from irrigated and natural ecosystems together with a net of agro-meteorological stations were used to develop two models for ET quantification at basin scale, based on the Penman-Monteith equation. The first model (PM1) uses the resistances to the latent heat fluxes estimated from satellite measurements, while the second one (PM2) is based on the ratio of ET to the reference evapotranspiration (ET0) and its relation to remote sensing parameters. The models were applied in the Low-Middle São Francisco river basin in Brazil and, after comparison against field results, showed good agreements with PM1 and PM2 explaining, respectively, 79% and 89% of the variances and mean square errors (RMSE) of 0.44 and 0.34 mm d-1. Even though the PM1 model was not chosen for ET calculations, the equation for surface resistance (rs) was applied to infer the soil moisture conditions in a simplified vegetation classification. The maximum values of rs were for natural vegetation—caatinga (average of 1,937 s m-1). Wine grape and mango orchard presented similar values around 130 s m-1, while table grape presented the lowest ones, averaging 74 s m-1. Petrolina and Juazeiro, in Pernambuco (PE) and Bahia (BA) states, respectively, were highlighted with the biggest irrigated areas. The highest increments are for vineyards and mango orchards. For the first crop the maximum increment was verified between 2003 and 2004 in Petrolina-PE, when the cultivated area increased 151%. In the case of mango orchards the most significant period was from 2005 to 2006 in Juazeiro-BA (129%). As the best performance was for PM2, it was selected and used to analyse the regional ET at daily and annual scales, making use of Landsat images and a geographic information system for different soil moisture conditions. Considering the daily rates of the regional ET, pixels with values lower than 1.0 mm d-1 occurred outside the rainy season, representing the caatinga species. Values from 1.0 to 5.0 mm d-1 during the driest conditions of the year coincided with irrigated crops, being the highest values for table grapes. The highest accumulated ET values during 2006 were for mango orchards, being around 500-1,300 mm yr-1. Vineyards presented lower values, ranging from 450-800 mm yr-1, while in caatinga they were between 200 and 400 mm yr-1. It could be concluded that irrigated mango orchards and vineyards in that year consumed more water than caatinga by factors of 3 and 2, respectively. The mango orchards and vineyard areas, representing 19.4 and 8.2% of the total irrigated area, respectively, resulting in a total evaporative depletion of 0.22 km3 yr-1 in the growing regions comprised of the agro-meteorological stations. [ABSTRACT FROM AUTHOR]

• Rn partitioning is strongly influenced by rainfall events in pastures. • More of the available energy went into the sensible heat flux during the year with less precipitation. • Pasture was coupled to the atmosphere, mainly in the dry season. • Energy balance closure was 87% in 2016–2017 and 84% in 2017–2018. The production of beef, soy, and corn in Brazil is currently higher in the Cerrado biome than other biomes, such as Amazon forest. The expansion of agricultural production has caused significant changes in local albedo and surface energy fluxes. Analyzing energy fluxes is essential for understanding the microclimate dynamics in the region. However, these factors are incompletely understood because of the limited number of micrometeorological measurements in the region. This study evaluated the energy fluxes and decoupling factor in pasture lands in the Brazilian Cerrado. The study was carried out in two hydrological years (2016–2017 and 2017–2018) in Três Lagoas, Mato Grosso do Sul, Brazil. An eddy covariance system outfitted with net radiation and ground heat flux plates was used to determinate the energy balance components. There was a predominance of latent heat flux (LE) compared to the sensible heat flux in the wet season in both years. The ratio of LE to net radiation decreased significantly in the dry season, especially in 2017–2018 where high daily average Bowen ratio was found to be 3.7 (± 3.0). In addition, the observed surface decoupling factor (Ω), that indicates the stomata control due to atmospheric condition, was lower during the dry season, especially in 2017–2018 with an average Ω of 0.4 (± 0.1), and confirmed that pasture lands were highly coupled to the atmosphere during dry season. The lower annual average of Ω in 2017–2018 was mainly due to the control of stomatal conductance to maintain essential metabolic activities and plant senescence during the unexpected drought that occurred in that period. Thus, the present study shows important findings necessary to understanding how droughts modulate the energy balance components in pasture lands, mainly considering the intensification of droughts in connection with climate change. [ABSTRACT FROM AUTHOR]

Abstract: There is a growing interest in quantifying regional scale actual evapotranspiration (ET) for water accounting and for water productivity assessments at river basin scale. Methods that provide point values fail to describe the situations at larger scales. Remote sensing measurements can be used at different spatial scales. This paper applies the theory of the Surface Energy Balance Algorithm for Land (SEBAL). SEBAL was originally derived for Egypt, Spain and Niger [Bastiaanssen, W.G.M., 1995. Regionalization of surface flux densities and moisture indicators in composite terrain: a remote sensing approach under clear skies in Mediterranean climates. Ph.D. dissertation, CIP Data Koninklijke Bibliotheek, Den Haag, The Netherlands. 273 pp.] and was calibrated and validated using ground measurements from four flux sites and from seven agro-meteorological stations in the semi-arid region of the Low-Middle São Francisco River basin, Brazil. Measured parameters included surface albedo, surface temperature, atmospheric and surface emissivity, soil heat flux, surface roughness, net radiation, air temperature gradients, sensible heat flux, latent heat flux, evaporative fraction, and photosynthetically active radiation. The daily ET was estimated (RMSE of 0.38mmd−1) for mixed agricultural and natural ecosystems. The improved coefficients for the local conditions can now be used to study the impact of expanding irrigated agriculture on the regional water balance and to quantify the water productivity of irrigated horticulture that is the largest water consumer in the Brazilian semi-arid region. Both applications are described in an accompanying paper (Part B). [Copyright &y& Elsevier]

Aiming to subsidize the rational water resources management, an R package called "agriwater" was created in order to obtain the energy balance on the soil and actual evapotranspiration using satellite imagery and agrometeorological data. This package apply the Simple Algorithm for Evapotranspiration Retrieving - SAFER to calculate the evapotranspiration fraction E T r (or E T A E T 0 −1), actual evapotranspiration (E T A ) and latent heat flux (λE); the Slob equation calculate the net radiation ( R N ); ground heat flux (G) is modeled from R N ; and the sensible heat flux (H) is retrieved as the residue of the energy balance equation. Landsat-8 (with and without thermal bands), Sentinel-2 and MODIS digital images can be used. Results are presented in raster format and can be post-processed by GIS analysis or anothers R procedures. A study case using Sentinel-2 images and agrometeorological data of a semiarid area from Brazil was performed. The requirements and conditions for use of the package are explained. • This package can use Sentinel-2, Landsat-8 or MODIS images, providing daily analysis at 10, 30- and 250-meters resolution. • The Simple Algorithm for Evapotranspiration Retrieving was applied in tropical, semiarid, subtropical and wetland areas. • Actual evapotranspiration, surface temperature, albedo, latent, sensible, and ground heat fluxes are spatially retrieved. • No crop or soil classification, nor extreme thermohydrological conditions (to set hot and cold pixels) is needed. • Results are in the form of raster file, which can be post-processed by using R or GIS-based software. [ABSTRACT FROM AUTHOR]