SIRTA Cloud and Radiation Observatory
SIRTA
Institut Pierre Simon Laplace
Algorithms
M. Haeffelin, A. Armstrong, L.
Barthès, O. Bock, C. Boitel, D.
Bouniol, M. Chiriaco, J.
Delanoe, P. Drobinski, J-L.
Dufresne, C. Flamant, M.
Grall, F. Hourdin, F. Lapouge,
Y. Lemaître, A. Mathieu, Y.
Morille, V. Noel, J. Pelon, C.
Pietras, A. Protat, B. Romand,
G. Scialom, R. Vautard, Y.
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
Wanherdrick
SIRTA
LIDAR
Data Products
Cloud and
aerosol vertical
structure
Multi-test algorithm applied on 532-nm channel to identify cloud layers,
aerosol layers, molecular layers, and boundary layer height (Morille et
al., 2004)
Optical depth
Multi-retrieval algorithm applied on 532-nm channel to retrieve optical
depth of cloud or aerosol layers (Cadet et al., 2004)
Depolarization
and
color ratio
Multi-wavelength algorithms using linear and cross-polarized 532-nm
and linear 1064-nm channels to discriminate particle shape (Noel et
al., 2002)
RADAR
Cloud structure
Ice/water
content
Particle size
distribution
Mean particle diameter from radar reflectivity and doppler velocity
Size distribution related to mean diameter
Extinction and ice water content function of reflectivity and size
distribution
Retrieval uncertainties estimated 50%
CEILOME
TER
Cloud-base
height
Vaisala proprietary algorithm
RADIATIVE FLUX
STATION
Fraction of
cloud cover
Shortwave and
longwave clearsky fluxes
Clear-sky models derived from measurements. Threshold to identify
cloud cover fraction.
(Long and Ackerman 2000)
MWR
Integrated
Brightness temperatures simulated from radiosonde profiles to calibrate
water vapor
MWR. Water vapor and liquid water contents inverted using the
and liquid
Kummerow and Weinman (1988) algorithm.
water content Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Lidar Data Products
Cloud and aerosol vertical structure
Wavelet transform method:
• Search for high correlation
between a wavelet and the lidar
signal
• Mexican hat for particle layers in
the free troposphere
• Step function for boundary layer
Cloud / aerosol separation based
on PR2 peak-to-base ratio
Distinction between true noise (no
more photons) and apparent noise
(no more scatterers)
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Lidar Data Products
L0:
• Lidar back-scattered power
L1:
• Quality flag
• Monitoring noise
L2:
• Atmospheric Mask (Clouds,
aerosols, Boundary layer,
Particle-free zone, Noise
• Cloud thermodynamic
phase
• Cloud and aerosol layer
optical depth
L3:
• Time and layer -average
data
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Radar-Lidar Cloud Products
Combine Reading classification with LNA classification
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Cloud Product Dataset Analysis
Processed LNA Lidar data: 10/2002 - 09/2004
• Cloud, aerosol mask
• Time averaged data
20040830
20040830
20040830
20040830
20040830
20040830
20040830
20040830
20040830
20040830
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
17.0
01515 01995 100
01620 01995 030
01815 02220 100
01650 02325 100
02055 02490 086
02085 02550 100
01875 02760 100
10005 11655 100
10170 11700 083
10710 11790 100
10545 11865 100
09435 12000 100
09150 12150 100
09990 12135 100
09675 12060 095
09390 11565 070
08550 11715 100
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Cloud Product Dataset Analysis
Frequency of occurrence of cloud fraction
and vertical distribution of cloud layers
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Cloud Product Dataset Analysis
Frequency of occurrence of single and
multiple cloud layers
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Cloud Product Dataset Analysis
Frequency of occurrence of cloud thickness
and vertical distribution
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Cloud Product Dataset Analysis
Relative occurrence of cloud altitude
(monthly variations)
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Cloud Product Dataset Analysis
Relative occurrence of cloud altitude
(seasonal variations)
Vertical
Extent of
Clouds
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Cloud Product Dataset Analysis
Relative occurrence of cloud-base altitude
(seasonal variations)
Occurrence
of Cloud
Base
Cloudnet meeting 18-19 Oct 2004Palaiseau
- Martial Haeffelin
10/2002-09/2004
LNA Lidar
SIRTA
Lidar Data Products
Cloud thermodynamic phase
• Based on lidar depolarization ratio + b threshold
• Requires normalization in particle-free zone (2.74%)
Normalization
problem
Ice water
Mixed phase
Liquid water
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Lidar Data Products
Cloud optical depth
Molecular Integration method: t = ∫ a(z)dz
Integrated extinction = power loss between theoretical molecular return
below the cloud and molecular return above the cloud
Particle Integration method:
t = LReff ∫ (R(z)-1)bm(z)dz
where R(z)=(bm(z)+bc(z))/bm(z)
LReff prescribed: 18 sr
LReffopt derived from MI method
Cadet et al. 2004
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Lidar Data Products
Cloud optical depth
Cadet et al. 2004
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Radiative Flux Station
Operations:
• 18 months of Global SW + LW
• SW Direct + Diffuse missing
12/03-02/04
SW
LW
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Radiative Flux Dataset Analysis
SW Direct
SW Diffuse
SW Global
LW Down
May 2004
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Radiative Flux Dataset Analysis
Shortwave radiative impact of cloud layers
Clear-sky reference from F = a cos(q)b
Single-layer
high-altitude
clouds
May 2004
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin
SIRTA
Perspectives
• Produce 2-year radar-lidar L3 products
• Pursue analysis of vertical structure
• Pursue developments of lidar-only retrievals and combination
• Develop clear-sky flux and radiative forcing products, and analyse in
relation to the cloud data base
Institutes and programs supporting SIRTA:
Cloudnet meeting 18-19 Oct 2004 - Martial Haeffelin