January 2014
Message 83

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[Met-jobs] PhD position at CNRM (Toulouse, France)

From CALVET Jean-christophe <>
To "met-jobs " <>
Cc CALVET Jean-christophe <>
Date Mon, 27 Jan 2014 18:33:16 +0100 (CET)

Dear Colleagues,

The following subject is proposed by CNRM (Meteo-France/CNRS):

"Integration of satellite data in SURFEX to monitor vegetation at a global 

The SURFEX modelling platform includes a generic dynamic vegetation model 
(ISBA-A-gs) able to simulate plant growth and the energy, water and carbon 
fluxes in relation to soil moisture. The model permits a detailed description 
of the soil moisture profile, and represents the diurnal cycle of the surface 
fluxes together with the seasonal, interannual, and decadal variablity of 
vegetation. This version of SURFEX is being implemented at a global scale, and 
includes a Land Data Assimilation System (LDAS). Satellite-derived vegetation 
(e.g. LAI) and soil moisture products can be jointly assimilated by ISBA-A-gs. 
The maximum available water content of the soil (MaxAWC) is a key driver of 
plant transpiration and plant growth. It is a major source of uncertainty in 
the model. MaxAWC depends on various soil properties and on the capability of 
plants to develop a rooting system in the soil. In this PhD work, the shape and 
the depth of the root profile will be assessed through the minimization of a 
cost function describing the ability of the model to reproduce the interannual 
variability of the satellite-derived LAI. Long time series of LAI (from 1 km to 
5 km spatial resolution) are now available over the last 30 years at a global 
scale. They will be used to map MaxAWC over the most homogeneous rainfed crops 
and grasslands of the Earth. In 2015, the first products derived from Sentinel 
2 and Sentinel 3 (S2 and S3, respectively) will be available. The S2 data will 
be used to disaggregate the S3 products and the MaxAWC map over France at a 
spatial resolution of 100 m. An hydrology model coupled to SURFEX will be used 
to assess the impact of the new MawAWC maps on river discharge. The 
uncertainties related to a number of assumptions in the model, such as the 
fraction of bare soil evaporation and the fraction of the evaporation of water 
intercepted by the vegetation canopy, will be quantified. The model simulations 
will be validated using agricultural statistics over France and at a global 
scale, together with phenology in situ observations. Finally, 
micrometeorological observations performed over the Meteopole site in Toulouse 
since June 2012 will be used to evaluate the model and to test new developments 
in the representation of the soil water holding capacity, as this site is 
rather stoney and includes hard soil layers.

This PhD work is co-funded by CNES 

Application should be done by email by sending a resume, a motivation letter, 
and the names, telephone and email address of two referees to:
Deadline: 14 March 2014.

Best regards,
JC Calvet.

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