EU/DG-XII
Contract:ENV4-CT-95-0036
The CARL project is a joint effort involving
research teams from Germany, France,
Greece and the Netherlands. It is a three years project, started in December
1997, in the European Commision's RTD programme " Enviroment and Climate". New
methodologies will be tested in order to derive microphysical parameters of
warm and cold clouds during several campaigns involving groud-based and
airborne radar and lidar systems. The most interesting cases of the
experimental campaigns will be simulated with an advanced limited area model. A
significant effort has been devoted in the intercomparison between the
collected data from the observational systems and the model outputs. The model
used for the simulations is the Regional Atmospheric Modeling System, RAMS.
PARTNERSHIP
GKSS Research Center Geesthacht, Institute of
Atmospheric Physics, Max Planck Strasse D-21502 Geestacht, Germany
M.Quante (Quante@gkss.de), tel:
494152871501, fax:494152872020
O.Danne (Danne@gkss.de), tel:
494152871520, fax:494152872020
F.Albers (Albers@gkss.de),
D.Milferstadt, fax:494152872020
Institut
Pierre Simon Laplace, 10-12 avenue de
l'Europe, 78140 Velizy, France
J.Testud ( Testud@cetp.ipsl.fr), tel:33139254476, fax:
33139254922
F.Baudin (Baudin@cept.ipsl.fr), tel:33139254850,
fax: 33139254872
P.H.Flamant (Flamant@lmd.polytechnique.fr),
Ecole Polytechnique, 91128, Palaiseau, France, tel: 33169334550,
fax:33169333005
J.Pelon(Jacques.Pelon@aero.jussieu.fr),
Universite Pierre et Marie Curie,T14,E5,B102,4,Place Jussieu,75252, Paris cedex
05, France; tel: 33144273779, fax: 33144273776
National
and Kapodistrian University of Athens (NKUA),
Department of Physics, Division of Applied Physics, Atmospheric Modeling and
Weather Forecasting Group, Panepistimioupolis, Bldg PHYS-V, 15784, Athens,
Greece.
G. Kallos (kallos@mg.uoa.gr),
tel: 30 1 7276923, fax: 30 1 72 95 281
E. Mavromatidis (imavr@mg.uoa.gr),
tel: 30 1 7276832, fax: 30 1 72 95 281
KNMI, Koninklijk Nederlands
Meteorologisch Institut, Postbus 201, 3730
AE De Bilt, Wilhelminalaan 10.
Hannelore Bloemink (bloemink@knmi.nl)
The main objectives of the project are:
·
To validate and
improve cloud parameterizations in atmospheric models, detailed information about
the cloud characteristics must be available on large scales. Crucial cloud
characteristics to the cloud radiation budget, e.g. the particle size
distribution (liquid or ice, as represented by the effective radius re
) and liquid or ice water content (
phase and W ), are presently poorly measured at such a scale. New
measurements from airborne and
spaceborne platforms will be utilized
in order to allow cloud sampling on large horizontal scales. The objective of
this work is to prepare such developments by testing new observational remote
sensing methods combining lidar and radar systems.
·
To test
different procedures involving several wavelengths, polarization, lidar fields
of view and multi-beam analysis and ground-based versus airborne observations
for the retrieval of the cloud parameters. As a first step, procedures will be
tested, by using ground-based measurements and in-situ cloud sampling for warm
clouds. In a second step airborne lidar and radar system will be involved.
·
Model
simulations will be performed in order to analyze the impact of the cloud
parameterization, on the radiation and dynamics at the mesoscale. The simulated fields and microphysical
processes will be used also to provide a feedback on the measuring systems and
especially the prototype ones (e.g. new radars at 96 GHZ, LIDAR).
·
During the
project, a cloud Radar (with polarization diversity to discriminate water and
ice phases and Doppler capabilities) and two backscattering Lidar ( with
polarization diversity) will be operated from the same site and airborne
platform. The target of the measurements is high, middle and low level clouds.
The main objective is to retrieve the effective radius and the water content of
such clouds. To do so, it is aimed at deriving the second and third moment of
the cloud droplet distribution from lidar and radar signal analysis, and to
correct for diffraction and multiple scattering. Model calculations will be
performed to analyze the impact of the retrieval and related errors, and check
the quality of retrieved cloud parameters and their representativeness, with
reference to radiation budget parameters measured at the same time. The
atmospheric model will be used to perform multi-scale simulations with a state
of the art cloud microphysical parameterization module activated. Two-way
interactive nesting capabilities of the model will be used in order to cover a
regional scale area and simultaneously to obtain very high resolution over the
experimental location.
Two experimental campaigns have been organized so far and a
third is under way. The main task of the Atmospheric Modeling and Weather
Forecasting Group of the University of Athens (NKUA/AM&WFG) is to perform
the appropriate model development and simulations with RAMS and inter-compare
the results with the observations from the experimental radar and lidar
platforms.
1st
experimental campaign
Location: Geestacht
Date: 6 December 1995
Period of observations: 8 minutes,
from 16:06 UTC to 16:14 UTC.
Instruments: The GKSS 95 GHz cloud Radar.
2nd
experimental campaign
Location: Palaiseau ( near Paris)
Period of observations: 26 April to
15 May 1999
Instruments:
For ground-based measurements: 5.5 GHz Radar
(IPSL), 95 GHz Radar (GKSS), Lidar 0.53 and 10.6 mm (IPSL), Lidar
ceilometer 0.9 mm (KNMI), visible and infrared radiometers (
KNMI, IPSL)
For airborne measurements: FSSP, 2DC, 2DP
sondes(GKSS), Visible and infrared broadband radiometer, narrow band narrow
beam infrared radiometer( Meteo-France)
Flights : Five flights were performed
during the campaign with the Merlin aircraft
( Meteo-France, subcontractor of IPSL) to get the observed cloud
microphysics, for comparison and validation.
Additional
model simulations for the 2nd experimental period
In order to investigate the model sensitivity to various
settings, a number of additional simulations were performed. The new version of
RAMS (4.2.9) was used. A number of figures have been prepared, especially in
the form of time-versus-height form for better inter-comparison with the
experimental observations (Radar, Lidar, ceilometer) and conventional
measurements (soundings)
A quick
description of RAMS
RAMS is a highly
versatile numerical code developed by scientists at Colorado State University
and Aster Division of Mission Research Inc. (http://www.aster.com) for
simulating and forecasting meteorological phenomena (Walko and Tremback, 1996;
Pielke et al., 1992). It is considered as one of the most advanced modeling
systems available today. It is a merger of a non-hydrostatic cloud model
(Tripoli and Cotton, 1982) and a hydrostatic mesoscale model (Mahrer and
Pielke, 1977). It has been developed in order to simulate atmospheric phenomena
with resolution ranging from tens of kilometers to a few meters. There is no
lower limit to the domain size or to the mesh cell size of the model finite
difference grid. A general description of the model and its capabilities is given
in Pielke et al (1992). However some RAMS features are summarized in the
following:
1. Two-way interactive nesting with any number of either telescoping or
parallel fine nest grids (Clark and Farley, 1984).
2. Terrain following coordinate surfaces with Cartesian or polar
stereographic horizontal coordinates.
3. Non-hydrostatic or hydrostatic time-split time differencing.
4. Cloud microphysics parameterization at various levels of complexity.
5. Various turbulence parameterization schemes.
6. Radiative transfer parameterizations (short and longwave) through
clear and cloudy atmospheres.
7. Various options for upper and lateral boundary conditions and for
finite operators.
8. Various levels of complexity for surface-layer parameterization
(soil model, vegetation etc.).
9. Horizontally homogeneous or variable initialization (isentropic
analysis). ECMWF and National Center for Environmental Predictions (NCEP)
analysis files can also be used for initialization.
10. It is highly portable and runs on several types of computers.
11. A parallel version of RAMS is currently available for efficient use
in high performance computers.