January 23, 2012

Since the 1980's the satellites have been monitoring the surfaces's energy behaviour

SINCE THE 1980's THE SATELLITES HAVE BEEN MONITORING THE SURFACES' ENERGY BEHAVIOUR Update: 01/23/2012
Logo 50 ans de résultats scientifiques
Logo 50 ans de résultats scientifiques
The water stress detection and the evapotranspiration estimates are available thanks to the surface temperature measurements in the thermal infrared range. A better knowledge of the water cycle and vegetation operation opens up a vast range of applications for agriculture (water management and production monitoring for example) and especially hydrology but also for the understanding of the global warming impacts and its interactions with the continental biosphere. Recent methodological progress was obtained in the surface flux modelling and remote sensing data application in the thermal infrared. In order to supply the increased demand in accurate monitoring, the current space systems' limitations led the science community and CNES to propose a MISTIGRI mission which would combine space high-resolution and high revisit capability in the thermal infrared range.

METEOSAT and NOAA-AVHRR were for a long time the standalone meteorological satellites to operate in the thermal infrared range with such high revisit capability so their data were widely used since the 80's to monitor the surface energy behaviour.

The development of water stress detection and continental biosphere evaporation estimates methods opened up a very wide application field in agriculture, climatology, hydrology and meteorology.

By supporting laboratories through structures like TOSCA (previously TAOB) for methodological works and by playing an active role in many international programmes with the CESBIO, CNES contributed to strengthen a very active science community around the thermal infrared in France.

At first, the works were focused on local and national scales such as the rain, evaporation and agricultural production mapping in Senegal within the frame of the European programme on Sahelian area desertification or the Hapex Sahel and Salsa Mex programmes of hydrological nature in which the CESBIO play a very active role. Then the works did reorient towards more accurate scales to supply the demand in agricultural parcel and little production area management.
griculture, climatology, hydrology, meteorology.

The Alpilles-ReSeDa experiment on a little agricultural region in South-East France in the early 1990's was a typical example of this evolution with the implementation of new approaches which combined soil-vegetation-atmosphere transfer models and thermal infrared remote sensing data achieved with thin space resolution and high revisit frequency at a level compatible with the real-time vegetation operation monitoring objective.

Several avenues are being explored:

  • either around the models based on the application of temperature variability among known reference evaporation parcels (so called contextual approach);
  • or around the soil-vegetation-atmosphere transfer deterministic model application associated with inversion or assimilation process making the specification correction and real-time model calibration possible using satellite data.

An evaluation work aimed to compare the performance of each approach on the Crau and Camargue region is being carried out at INRA of Avignon.

Daily evapotranspiration evolution (mm/day) based on MODIS images and EVASPA operational processing lines developed at INRA Avignon (UMR EMMAH) between 2001 and 2009 with different ecosystem samples (1x1 km) in the Crau and Camargue region.
(a) Comparison between wetlands (rice fields) and dry area (coussouls): the coussoul is a typical dry grassy area of the region and presents a low evapotranspiration level.
(b) Average daily evapotranspiration evolution (mm/day): the decreasing percentage of irrigated meadows/coussouls (cf. little images) explains the increasing evapotranspiration level between the meadows class 1 to 3.

Suitable space systems in terms of space resolution and revisit frequency are required in the panorama of the pending missions in order to achieve operational applications such as irrigation management, water close management, risk monitoring (water stress and forest fires for instance), biogeochemical cycle monitoring and soil pollution control with regard to the use of water for example.

The recent international initiative on world food security, GEO-GLAM (Global Agricultural Monitoring), agreed by the G20 within the frame of the action plan to curb food price volatility on agricultural markets shares the objectives of the GMES and clearly enhances this type of need. These motivations led the science community and CNES to design, in partnership with Spain, the project of the high-space resolution thermal infrared and high revisit frequency MISTIGRI space mission which just finished phase A.

Contacts

  • Scientific contacts: Jean-Pierre Lagouarde (INRA Bordeaux), Dominique Courault (INRA Avignon), Albert Olioso (INRA Avignon)
  • Continental surfaces program scientist at CNES: Selma Cherchali
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