6533b832fe1ef96bd129ac4c

RESEARCH PRODUCT

Shelter and remotely sensed night temperatures in orange groves

subject

description

In previous papers we have used a linear regression approach for determining nocturnal air temperature in orange groves from satellite thermal data. However, this procedure has a poor precision (≈ 2 °C) for applications such as frost forecasting. For this reason a theoretical method has been proposed, which is based on the following assumptions: (1) the air temperature (Ta) is the result of the convective heat exchange between ground and air, and between air and orange trees, and (2) the remotely-sensed temperature (T) can be expressed as a function of ground (Tg) and orange tree (Ts) temperatures. So the relationshipT = Ta + (ag − α) (Tg − Ts) has been derived, wherea = (1 +h2πR/h1L)−1 andαg = (eg/e) [Pg + (1 −e0)G′Ps];h1 is the convective heat transfer coefficient between ground and air,h2 is the convective heat transfer coefficient between air and orange tree,R is the orange tree radius,L is the distance between two orange tree trunks,eg ande0 are the emissivities of the ground and of the orange tree,e is the effective emissivity,Pg andPs are the proportions of ground and side of the orange tree observed by the sensor, andG′ is the shape factor ground-side.