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.
title: Assimilation of airborne cloud radar data during the HyMeX
special observing period
supervisors: Dr. Olivier Caumont, Dr. Véronique Ducrocq, Dr.
CNRM-GAME (Météo-France & CNRS), 42 avenue G. Coriolis 31057
Toulouse Cedex 1, France
for application: 31 March 2015
goals, proposed methodology:
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.
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.
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.
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.
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.
knowledge and experience:
(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.
or English spoken, English well-written.
full consideration, the applicant should send a detailed CV by March,
selected, the candidate will have to submit an application through
the armaments (DGA) portal in May.
CNRM-GAME UMR3589 (Météo-France, CNRS)
42 av G. Coriolis
31057 TOULOUSE Cedex 01 (FRANCE)
Tel: +33 5 61 07 96 46 | Fax: +33 5 61 07 96 26 | Email: email@example.com