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March 2013
Message 12

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[Met-jobs] PhD position at Observatoire de Paris

From Catherine Prigent <catherine.prigent@obspm.fr>
To met-jobs@lists.reading.ac.uk
Cc Catherine.Prigent@obspm.fr
Date Tue, 05 Mar 2013 18:07:27 +0100

Dear colleague,

Could you please post this announcement?
Thank you

Catherine Prigent


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A PhD position is available in Paris Observatory (LERMA), starting in September 2013.

Subject:

 

Characterization and quantification of ice clouds from millimeter and sub-millimeter observations: preparing the next generation of operational instruments on MetOp-SG


Requiered background:

 

Solid knowledge of physics, if possible in the field of atmospheric radiative transfer and remote sensing. Proficiency in at least one computer programming language.

 

 

Description of the topic:

 

Ice clouds play a significant role in the energy balance of the planet, with a positive or negative, depending on their optical properties. Current estimates of the amount of ice cloud vary with a ratio of 10 between climate models and estimates from space also vary with similar ratios.

The next generation of European operational meteorological satellites (MetOp-SG) will carry passive millimeter / sub-millimeter radiometers with frequencies up to 670 GHz, for a better characterization of ice clouds. So far the observations are limited to 190 GHz, with limited sensitivity to the ice phase in clouds. The Ice Cloud Imager (ICI) for MetOp-SG is a conical scanning imager with 3 channels around the H20 line at 183 GHz, as well as around the 325 and 448 GHz lines and two window channels at 224 and 664 GHz. It will estimate the amount of ice cloud, the effective size of the particles, and the altitude of the cloud.

LERMA at Observatoire de Paris has promoted the use of millimeter-wave and sub-millimeter to study Earth's atmosphere for more than 10 years, in close collaboration with various international groups. The purpose of this thesis is to continue these developments toward the operational use of the ICI observations by numerical weather prediction models. The work will consist in performing simulations of realistic radiative transfer, investigating the sensitivity of the millimeter / submillimetre observations to cloud properties, analyzing airborne data, and developing inversion methods to derive the cloud properties from the observations.

Firstly, the student will become familiar with the radiative transfer codes to simulate observations. The community model ARTS (http://www.sat.ltu.se/arts/) will be used for its effectice treatement of the scatterind. The code will be fed by a detailed and realistic description of the atmospheric column in the cloud from a mesoscale cloud model (Meso-NH http://mesonh.aero.obs-mip.fr/mesonh/). Simulations will be performed to analyze the sensitivity of the different frequencies to the cloud properties and microphysics.

A airborne demonstrator has been developed jointly by the UK Met Office and ESA. The instrument will fly by early 2013 and participate in a series of measurement campaigns in various environments. In a first step, the data will be analyzed to refine the calibration, check the consistency of the observations and study their sensitivity to the cloud parameters as compared to auxiliary cloud parameters measured in situ.

Then, inversion algorithms observations will be developed to retrieve the cloud parameters (amount of ice, cloud altitude, and effective particle size). These algorithms will be applied to airborne radiometric observations. The inversion method may be based on a Bayesian algorithm or neural networks. The retrieved geophysical parameters will be confronted with in situ measurements made during the campaigns.

At the global scale, an inversion algorithm will be developed, based on the same methodology to estimate the amount of ice cloud from existing satellite observations between 150 and 190 GHz (AMSU-B, MHS). The consistency of the results will be evaluated by comparison with other retrieved products, thus providing a preliminary assessment of the method.

 

For more information, contact:


Catherine Prigent, LERMA, Obs de Paris, 61, av de l’Observatoire, 75014 Paris,

Tel: 01 40 51 20 18, catherine.prigent@obspm.fr


An application will have to be sent to CNES  (http://www.cnes.fr/web/CNES-en/10685-st-doctoral-grants.php), after contacting Catherine Prigent.  



-- 
Dr. Catherine Prigent
CNRS, LERMA
Observatoire de Paris
61, avenue de l'Observatoire
75014 Paris, France
tel: 33 (0)1 40 51 20 18
fax: 33 (0)1 40 51 20 02
email: catherine.prigent@obspm.fr
see: http://aramis.obspm.fr/~prigent/publication.html


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