Search results for "Net radiation"

Application of a simple algorithm to estimate daily evapotranspiration from NOAA–AVHRR images for the Iberian Peninsula

2007

International audience; Evapotranspiration (ET) is a key process in land surface–atmosphere studies. It mainly depends on water availability and incoming solar radiation and then reflects the interactions between surface water processes and climate. In this paper, a methodology for retrieving ET from low spatial resolution remote sensing data is presented. It is based on the evaporative fraction concept, and it has been applied to Advanced Very High Resolution Radiometer (AHVRR) data acquired over the Iberian Peninsula. The methodology does not require other data than the data provided by the satellite and may be applied to areas with almost spatially constant atmospheric conditions and whi…

Development of a general model to estimate the instantaneous, daily, and daytime net radiation with satellite data on clear-sky days

2015

Net radiation is a key variable in computing evapotranspiration and is a driving force in many other physical and biological processes. Remote sensing techniques provide an unparalleled spatial and temporal coverage of land-surface attributes, and thus several studies have attempted to estimate net radiation by combining remote sensing observations with surface and atmospheric data. However, remote sensing provides instantaneous data, when many applications and models need information at other temporal scales. In this work, a new general methodology is proposed to estimate daily and daytime net radiation and to retrieve the diurnal cycle of net radiation. Four images were acquired on differ…

Ecophysiological Characterization of the Canopy of Peach (P. persica L. Batsch) in Two Planting Systems

2007

Net radiation of the Iberian Peninsula from NOAA-AVHRR data

1998

In this work, we present a methodology to obtain the daily net radiation flux from NOAA-AVHRR data. To get this objective we need firstly to obtain shortwave net radiation flux from the solar global radiation flux and the albedo map. Secondly, we need to obtain the upward longwave radiation flux from surface temperature and emissivity and the downward longwave radiation flux from air temperature. Like an example of application of this methodology a daily net radiation flux image of the Iberian Peninsula is presented, in which we show that daily net radiation flux can be obtained with a satisfactory precision lower than 1.0 mmday -1 .

A satellite stand-alone procedure for deriving net radiation by using SEVIRI and MODIS products

2018

Abstract In this study, a new stand-alone satellite approach for the estimation of net surface radiation (Rn) has been implemented and validated for the Italian territory. The method uses the MODIS and MSG-SEVIRI time series products and it is independent of the use of ancillary data (i.e. ground measurements). A database of daily measurements of Rn, provided by 9 stations of the FLUXNET network, was used to validate the method in different ecological scenarios in the period 2010-12. The Rn modelled by the proposed approach and the corresponding FLUXNET measurements were in good agreement, with RMSE and R2 of 19.8 Wm−2 and 0.87, respectively, at 8-days scale, and 23.3 Wm−2 and 0.92, respect…

Estudio de la radiación neta en zonas semiáridas utilizando modelos lineales y neuronales y la sinergia entre GERB y SEVIRI

2012

Las regiones áridas o semiáridas se caracterizan por una distribución irregular de los recursos hídricos, lo que muchas veces constituye una limitación para el desarrollo de una determinada región. La variabilidad hidrológica de estas regiones se debe a la mala distribución espacial y temporal de la lluvia, a la topografía heterogénea y a los cambios de origen antropogénicos que muchas veces conducen a procesos de degradación y de desertificación. Como en estas regiones la evapotranspiración explica una parte significativa de la pérdida de agua hacia la atmósfera, el estudio y modelización de la radiación neta en superficie (Rn), es de suma importancia, una vez que las estimaciones o medici…

Estimating Maize (Zea mays) cvapotranspiration from NOAA-AVHRR thermal data in the Albacete area, Spain

1994

Abstract We have estimated evapotranspiration from maize (Zca mays) using NOAA thermal images infrared and meteorological data, by means of the relation where Ed is the daily evapotranspiration, is the daily net radiation expressed in mm of water per day, (Ta−Ts)i is the temperature difference between air and corn surface obtained near midday, and Bi is a semi-empirical constant which has been calculated as 0·53±0·10mm day−1K−1. We have tested the method obtaining actual daily evapotranspiration of maize with an acceptable precision (±0·9 mm day−1 taken Penman's method as the standard). Finally, a practical example is included, in which the different steps followed for applying the develope…

Characterization and Modelization of Surface Net Radiation through Neural Networks

2010

Artificial neural networks have shown to be a powerful tool for system modeling in a wide range of applications. In this chapter, the focus is on neural network applications to obtain qualitative/quantitative relationships between meteorological and soil parameters and net radiation, the latter being a significant term of the surface energy balance equation. By using a Multilayer Perceptron model an artificial neural network based on the above mentioned parameters, net radiation was estimated over a vineyard crop. A comparison has been made between the estimates provided by the Multilayer Perceptron and a linear regression model that only uses solar incoming shortwave radiation as input par…

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…