Assessment of the mutual impact between climate and vegetation cover using NOAA-AVHRR and Landsat data in Egypt
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ORIGINAL PAPER
Assessment of the mutual impact between climate and vegetation cover using NOAA-AVHRR and Landsat data in Egypt Mohammed A. El-Shirbeny & Mohamed A. Aboelghar & Sayed M. Arafat & Abdel-Ghany M. El-Gindy
Received: 15 January 2012 / Accepted: 29 November 2012 # Saudi Society for Geosciences 2013
Abstract The objective of the current study is to use satellite data to assess the mutual influence between vegetation and climate. The Ismailia Governorate was selected as a case study to investigate the impact of vegetation cover expansion on both land surface and air temperature from 1983 to 2010 and vice versa. This observation site was carefully selected as a clear example of the high rate of the reclamation and vegetation expansion process in Egypt. Land surface temperature (LST) was estimated through the Advanced Very High Resolution Radiometer (a space-borne sensor embarked on the National Oceanic and Atmospheric Administration) data while air temperature (Tair) was collected from ground meteorological stations in the study area. Irrigated agriculture is the largest consumer of freshwater resources. However, consistent information on irrigation water use is still lacking. Relative humidity, wind speed, solar radiation, and Tair data were inserted in the Penman–Monteith equation to calculate potential evapotranspiration (ETo), while both LST and Tair were used to observe the relative water status of the study area as a result of the water deficit index (WDI). Then, both WDI and ETo were used to calculate actual evepotranspiration (ETC.). The results showed that LST decreased by about 2.3 °C while Tair decreased by about 1.6 °C during the study period. The results showed also that the vegetation cover expanded from 25,529.85 ha in 1985 to 63,140.49 ha M. A. El-Shirbeny (*) : M. A. Aboelghar (*) : S. M. Arafat National Authority for Remote Sensing and Space Sciences, 23 Joseph Tito St., El-Nozha El-Gedida, Cairo, Egypt e-mail: [email protected] e-mail: [email protected] A.-G. M. El-Gindy Faculty of Agriculture, Ain Shams Univ, Cairo, Egypt
in 2009 with about 147 % increase. This decrease in LST and air temperature was according to the expansion of the cultivated land that was proved through the processing of three Landsat TM and Landsat ETM+ imageries acquired in June 19, 1985, June 7, 1998, and June 29, 2009. The vegetation water consumption was affected by the decreasing surface and air temperature. The results showed that the water deficit index decreased by about 0.35, and actual evapotranspiration increased by about 2.5 mm during the study period. Keywords Land surface temperature . Vegetation expansion . Water deficit index . Evapotranspiration
Introduction Since ground observation networks cover only a small portion of global land surface, it is important to use remote sensing data to overcome the spatial problems involved in conventional methods of evapotranspiration (ET) estimation. A series of advanced satellite sensors have been launched to provide data at regional to global
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