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February 2015
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[Met-jobs] PhD position in remote-sensing data assimilation at CNRM-GAME

From Olivier Caumont <olivier.caumont@meteo.fr>
To met-jobs@lists.reading.ac.uk
Date Fri, 6 Feb 2015 15:22:08 +0100 (CET)

Dear colleagues,

We are seeking applications for a 3-year PhD position to work on the assimilation of airborne cloud radar data in the framework of the HyMeX programme (see announcement below). Please feel free to forward this announcement to potential candidates.

Best regards,
Olivier Caumont



PhD title: Assimilation of airborne cloud radar data during the HyMeX special observing period

PhD supervisors: Dr. Olivier Caumont, Dr. Véronique Ducrocq, Dr. Benoît Vié

Place: CNRM-GAME (Météo-France & CNRS), 42 avenue G. Coriolis 31057 Toulouse Cedex 1, France

Deadline for application: 31 March 2015

PhD goals, proposed methodology:
The HyMeX programme (HYdrological cycle in the Mediterranean Experiment, http://www.hymex.org/) is an international experimental programme that aims at improving our understanding of the water cycle in the Mediterranean area. Its first special observing period (SOP) took place from 5 September to 5 November 2012. The main goal of this SOP was to document the heavy precipitation events and flash floods that regularly affect the north-western Mediterranean coastal areas. In the two-month campaign, around twenty rainfall events were documented in France, Italy, and Spain.
Exceptional instrumental means (research aircrafts, drifting balloons, lidars, radars, additional radiosoundings, etc.) were deployed during the SOP and allowed to harvest a unique observational dataset. Among these instrumental platforms, the Falcon 20 of the Safire unit (http://www.safire.fr/) made numerous flights in storm systems so as to document their thermodynamic, microphysical, and dynamical properties. In particular, the cloud radar Rasta (http://rali.projet.latmos.ipsl.fr/) was aboard this aircraft. This radar measures vertical profiles of reflectivity and Doppler velocity above and below the aircraft. This unique instrument thus allows to document the microphysical properties and the speed of wind and hydrometeors in clouds, quasi-continuously in time and at a vertical resolution of 60 m.
For this field campaign, Arome-WMed, a special version of the numerical weather prediction (NWP) Arome system, was developed. This version, which covers the whole north-western Mediterranean basin, ran in real time during the SOP in order to, notably, schedule the airborne operations, especially in storm systems. Arome-WMed delivers forecasts at a horizontal resolution of 2.5 km. Deep convection is resolved explicitly and microphysical processes are governed by a one-moment bulk microphysical scheme. By the start of the PhD, an additional two-moment microphysical scheme will become available. The three-dimensional variational (3DVar) data assimilation system of Arome-WMed ingests observations from a wide variety of instruments (radiosonde, ground automatic weather station, radar, satellite, GPS, etc.) every three hours.
The objective of the proposed PhD thesis is i) to compare the data observed by Rasta with the convective-scale Arome-WMed NWP system to evaluate the respective degrees of realism of its two microphysical schemes, ii) assimilate Rasta data, and iii) assess the potential of such data to improve the forecasting of heavy precipitation events. The PhD work will start with comparisons between Rasta data and Arome-WMed. This will allow to assess to which extent Arome-WMed is able to reproduce observed microphysical features and the benefits brought about by a two-moment microphysical scheme over a one-moment microphysical scheme in this respect. This will be accompanied with a reflection on which observation type to assimilate. A choice will have to be made between, e.g., raw data such as reflectivity and retrieved data such as ice contents. Comparisons between different radar observational types, their equivalents as simulated by the model, and independent observations will allow to address this question. Then, the assimilation system will be adapted to handle the cloud radar observations. As the Arome assimilation system is already able to assimilate similar data (wind vertical profiles, radial Doppler velocity, radar reflectivity), the changes will mainly consider geometrical aspects.
Assimilation experiments will be carried out for one flight to begin with. The respective roles of the reflectivity-related observations and the Doppler velocity-related observations will be investigated. These experiments will be compared with a reference experiment analogous to that which ran in real time during the campaign. This comparison will be facilitated by the wealth of observations harvested during the field campaign. The assimilation experiments will then be run for other worthwhile intensive observing periods of the campaign.

Required knowledge and experience:
Candidates (citizens from the European Union or Switzerland, under age 27) should hold or will obtain in 2015 a master's degree in Atmospheric, Environmental Sciences or equivalent. The applicant should be familiar with programming languages (Fortran, Unix,…), background in numerical modelling (especially microphysics) is welcome.
French or English spoken, English well-written.

For full consideration, the applicant should send a detailed CV by March, 31st to:
olivier.caumont@meteo.fr, veronique.ducrocq@meteo.fr, and benoit.vie@meteo.fr.
If selected, the candidate will have to submit an application through the armaments (DGA) portal in May.

--
Olivier Caumont
CNRM-GAME UMR3589 (Météo-France, CNRS)

CNRM/GMME/MICADO
Météo-France
42 av G. Coriolis
31057 TOULOUSE Cedex 01 (FRANCE)

Tel: +33 5 61 07 96 46 | Fax: +33 5 61 07 96 26 | Email: olivier.caumont@meteo.fr



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