Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Japon → Developing an Index based on surface temperature for assessment of moisture availability over vegetated land

Tottori University (2011)

Developing an Index based on surface temperature for assessment of moisture availability over vegetated land

Abdelmoneim Abdelsalam Mohamed

Titre : Developing an Index based on surface temperature for assessment of moisture availability over vegetated land

Auteur : Abdelmoneim Abdelsalam Mohamed

Université de soutenance : Tottori University

Grade : Doctor of Philosophy (PhD) 2011

Présentation

In arid regions of the world, agricultural production is limited by the availability of water and severely affected during times of drought. Drought occurs when there is insufficient soil moisture available for plants. The available soil moisture in the root zone is the central issue in food security. This background highlighted the need of a reliable indicator for the surface wetness status. Thermal inertia represents a measure of the material’s resistance to temperature change, and it is a function of the material’s conductivity and heat capacity. Water has a large heat capacity and heat conductivity, so the thermal inertia of wet soil is larger than that of dry one. This fact makes thermal inertia a useful physical parameter that indicates the surface wetness ; however, it cannot be measured remotely, instead it is inferred from the diurnal surface temperature range, especially from the difference between daytime and nighttime surface temperature. It is commonly used in surface soil moisture estimation for bare land. When there is vegetation cover, since the surface wetness is a function of soil surface water content plus leaf water content, this complication limits the use of thermal inertia on vegetated cases. Therefore, the effects of physiological activities, that is the change of vegetative surface temperature due to the transpiration, have to be taken into account to develop an effective index based on diurnal surface range for assessing and monitoring the surface wetness. This research is the first attempt to apply the diurnal surface temperature difference to model vegetated surface wetness metric (referred to as moisture availability ( m a ) ; defined as the ratio of actual to reference evapotranspiration ET) through combining meteorological data and surface energy balance models. This research conducted on the Loess Plateau of China, which is a water scarce region under threat of drought.

A new index was proposed, Normalized Day-Night Surface Temperature Index (NTDI), which normalizes the maximum daytime surface temperature and the minimum nighttime surface temperature, by the difference between the simulated maximum and minimum surface temperature, estimated from meteorological data by applying energy balance equation. The simulated surface temperatures represent the hypothetical maximum diurnal range of surface temperature (when ET = 0), which is determined only by the meteorological condition

Annonce

Résumé (0,43 Mb)

Page publiée le 23 octobre 2016, mise à jour le 19 avril 2020