Search results for "Evapotranspiration"

Actual evapotranspiration estimation by means of airborne and satellite remote sensing data

2006

ABSTRACT During the last the two decades, the scientific community developed detailed mathematical models for simulating land surface energy fluxes and crop evapotrans piration rates by means of a energy ba lance approach. These models can be applied in large areas and with a spatial distributed approach using surface brightness temperature and some ancillary data retrieved from satellite/airborne remote sensed imagery. In this paper a district scale application in combination with multispectral (LandaSat 7 TM data) and hyperspectral airborne MIVIS data has been carried out to test the potentialities of two different energy balance models to estimate evapotranspiration fluxes from a set of …

Combining a Two-Source Patch Model with Satellite Data to Monitor Daily Evapotranspiration at a Regional Scale

2008

In this work, we present a micro-meteorological approach for estimating surface energy fluxes that can be operationally used together with satellite images to monitor surface energy fluxes at a regional scale. In particular we will focus on the retrieval of daily evapotranspiration. The feasibility of the model is explored at a local scale using data collected over a maize crop in Beltsville, Maryland, USA, and a boreal forest in Sodankyla, Finland. Comparison of the results with ground measurements shows errors between plusmn15 and plusmn50 W m-2 for the retrieval of net radiation, soil heat flux, and sensible and latent heat fluxes in both sites. A methodology to apply the model to Landsa…

Climate change effects on the hydrological regime of small non-perennial river basins.

2015

Recent years have been witnessing an increasing interest on global climate change and, although we are only at the first stage of the projected trends, some signals of climate alteration are already visible. Climate change encompasses modifications in the characteristics of several interrelated climate variables, and unavoidably produces relevant effects on almost all the natural processes related to the hydrological cycle. This study focuses on potential impacts of climate variations on the streamflow regime of small river basins in Mediterranean, seasonally dry, regions. The paper provides a quantitative evaluation of potential modifications in the flow duration curves (FDCs) and in the p…

Maximum and Actual Evapotranspiration for Barley (Hordeum vulgare L.) through NOAA Satellite Images in Castilla-La Mancha, Spain

1996

Abstract An easy-to-follow methodology is developed for the assessment of regional evapotranspiration in Castilla-La Mancha, a semi-arid region of Spain. The methodology is applied to barley crops to monitor the irrigation scheduling over the region, by using remote sensing techniques supplemented by ground measurements. The methodology can be based on either of two models. In the first one, established by Caselles and Delegido, 1 the reference evapotranspiration, ET o , derives from the expression ET o = AR g (T a ) m a x + BR g + C where A, B and C are empirical coefficients, depending on climatic parameters and determined for each region; R g is the daily global radiation; and ( T a ) m …

Evapotranspiration simulations in ISIMIP2a-Evaluation of spatio-temporal characteristics with a comprehensive ensemble of independent datasets

2018

Actual land evapotranspiration (ET) is a key component of the global hydrological cycle and anessential variable determining the evolution of hydrological extreme events under different climate change scenarios. However, recently available ET products show persistent uncertainties thatare impeding a precise attribution of human-induced climate change. Here, we aim at comparing arange of independent global monthly land ET estimates with historical model simulations from theglobal water, agriculture, and biomes sectors participating in the second phase of the Inter-SectoralImpact Model Intercomparison Project (ISIMIP2a). Among the independent estimates, we use theEartH2Observe Tier-1 dataset …

2021

Abstract Terrestrial Essential Climate Variables, known as terrestrial ECVs, are key sources of information for both application- and scientific- oriented research. A large number of global terrestrial ECV products have been derived from satellite observations, and more are forthcoming. To unlock the full potential of these products, end-users need to know their uncertainties and error magnitudes. Due to the lack of conformity among validation strategies, a wide range of validation approaches have been employed to assess the quality of these products, and have resulted in reduced comparability even for the same terrestrial ECV. Addressing this challenge in validation practices requires the …

A simple algorithm to estimate evapotranspiration from DAIS data: Application to the DAISEX campaigns

2005

DOI:10.1016/j.jhydrol.2005.03.027; The knowledge of evapotranspiration is of great interest in many applications such as assessing irrigation water use. In this paper, a methodology is presented to estimate evapotranspiration using the surface energy balance model S-SEBI (Simplified Surface Energy Balance Index) and the evaporative fraction. The method is applicable under the assumptions of constant atmospheric conditions and sufficient wet and dry pixels over the image. The model uses remotely sensed parameters such as albedo, MSAVI (Modified Soil Adjusted Vegetation Index) and surface temperature and emissivity images. The methodology has been applied over the Barrax test site, located in…

Thermal remote sensing in the framework of the SEN2FLEX project: field measurements, airborne data and applications

2008

A description of thermal radiometric field measurements carried out in the framework of the European project SENtinel-2 and Fluorescence Experiment (SEN2FLEX) is presented. The field campaign was developed in the region of Barrax (Spain) during June and July 2005. The purpose of the thermal measurements was to retrieve biogeophysical parameters such as land surface emissivity (LSE) and temperature (LST) to validate airborne-based methodologies and to characterize different surfaces. Thermal measurements were carried out using two multiband field radiometers and several broadband field radiometers, pointing at different targets. High-resolution images acquired with the Airborne Hyperspectral…

Assessing opportunities for water savings in large-scale pressurized irrigation systems using actual evapotranspiration retrieved by surface energy b…

Remote sensing allows the observation of large land stretches and the acquisition of worthwhile information that can be used efficaciously in agro-hydrologic systems. Satellite imagery associated to computational models provide a reliable resource in estimating evapotranspiration (ET) fluxes based on surface energy balance. On irrigated crops, quantifying the spatial distribution of actual ET enables a broad range of applications such as irrigation management, monitoring water distribution, assessing crop water status and irrigation system performance. The general objective of the research was to propose a methodology to estimate ET by using Landsat Thematic Mapper (TM) images and surface e…

Geospatial analysis of drought tendencies in the Carpathians as reflected in a 50-year time series

2019

Climate change is one of the most important issues of anthropogenic activities. The increasing drought conditions can cause water shortage and heat waves and can influence the agricultural production or the water supply of cities. The Carpathian region is also affected by this phenomenon; thus, we aimed at identifying the tendencies between 1960 and 2010 applying the CarpatClim (CC) database. We calculated the trends for each grid point of CC, plotted the results on maps, and applied statistical analysis on annual and seasonal level. We revealed that monthly average temperature, maximum temperature and evapotranspiration had similar patterns and had positive trends in all seasons except aut…