By: Isabel F. Trigo
From: Instituto de Meteorologia, Instituto Dom Luiz da Univ. Lisboa
At: Complexo Interdisciplinar, Anfiteatro
Land Surface Temperature (LST) is an important variable for the assessment of the surface energy budget. LST controls the surface emitted long-wave radiation, being also important for the estimation of the sensible and latent heat fluxes between the surface and the atmosphere. Remotely sensed thermal data constitute the best source of information for LST estimation over large areas, and within these, data obtained from geostationary satellites are the only capable of fully characterising the daily cycle of LST.
The Satellite Application Facility on Land Surface Analysis (LSA SAF) maintains an operational service to produce, archive and freely distribute LST, among other variables related to land surfaces and land-atmosphere interactions (http://landsaf.meteo.pt/). In this presentation, I will briefly describe the work developed by the LSA SAF team â€“ a consortium lead by Instituto de Meteorologia and financed by EUMETSAT (http://www.eumetsat.int/).
Focusing on the activities related to LST, I will discuss the advantages and drawbacks of using data from polar-orbiters versus geostationary satellites. Within the LSA SAF, LST is estimated from measurements taken by EUMETSAT geostationary satellites, Meteosat Second Generation (MSG). Different methodologies, including that used operationally, will be described. The sources of errors will also be analysed and used to characterize the uncertainty of LST estimations. Such study will be complemented with an independent validation against in situ measurements and satellite retrievals of the same variable using data from other satellites. It will be shown that overall there is a good matching between remote sensing estimates and ground measurements. However, validation exercises put into evidence the directional character of satellite LST.