Analysis of ARM cirrus data and the incorporation of Doppler Fall-velocity measurements in lidar/radar retrieval Outline of lidar/radar procedure. Problem of habit and bi-modality. How Vd may help.
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Analysis of ARM cirrus data and the incorporation of Doppler Fall-velocity measurements in lidar/radar retrievals
Outline of lidar/radar procedure.
Problem of habit and bi-modality.
How Vd may help.
Active (lidar/radar) cloud remote sensing
lidarLidar
Radar
Returned Power
Tim
e or
R
ange
Lidar Radar
Difference in returns is a function of particle size !!
l= 350 1100nm
= l 3-100mm
Effective size for ice crystals
Ice particles are large compared to llid (Optical scattering regime)Ice particles are small compared to lrad (Rayleigh scattering regime)
Exact treatment of scattering difficult (impossible?)However:
Confirmed using DDA and RT calculations
R'eff-vs-Reff for ice crystals
Must know relationship between crystal Mass and maximum dimension (D) in order to predict Reff and IWC !
Lidar/Radar Inversion Procedure
Lidar+RadarSignals
a/Ze=F(R'
eff)
RetrieveR'
eff,a
Habit/sizedist form info.
Reff
IWCRadar ReflectivityRadar Reflectivity
Lidar SignalLidar Signal
Effective RadiusEffective RadiusIWCIWC
ExtinctionExtinction
April 18, 1996, CLARA
CLARE98 ARAT/C-130 flightINSU ARATINSU ARAT
UKMO C-130UKMO C-130
Leandre 532 nm lidarLeandre 532 nm lidar
Kestral 94 Ghz RadarKestral 94 Ghz Radar
--
Good comparision betweenin-situ 2-D probe and airborne lidar/radar results !(During CLARE'98)
Good comparision betweenin-situ 2-D probe and airborne lidar/radar results !(During CLARE'98)
Good agreement with IR radiometer observations(During CLARA)
Good agreement with IR radiometer observations(During CLARA)
Donovan and van Lammerenand Donovan et al. 2001.
C-130 2D vs Lidar/Radar results
D-binned A-binned
0.10.3
0.6
0.9
0.99
Application to ARM data35-GHz Radar, 532 nm Lidar
Jan 14, 2000
200 000 range/time points !!
5 months Data Lidar signalLidar signal
Radar Ze
Radar Ze
R'eff
R'eff
IWC'=IWC(R'eff
/Reff
)IWC'=IWC(R'eff
/Reff
)
Complex polycrystals
Hex-Plates
Comparision with Kristjansson (Mitchell)Function of Temperature only (based on Aircraft data from FIRE/CEPEX)
Assume a crystal habit and convert to R'eff usingtheir size-dist. model.
Complex polycrystals
Hex-Plates
Overall pattern similar but large degree of variability at a given temperature
Overall pattern similar but large degree of variability at a given temperature
How do things vary with IWC ? How do things vary with IWC ?
Bin by IWC' (not yet IWC)
IWC'=IWC (R'eff/Reff)
IWC'=IWC (R'eff/Reff)
Increasing IWC' g/m3
Fit to simple bi-modal size distribution model (Must assume a crystal model !)
½ Maximum dimension
Bi-Modal Size dist with fixed small mode
Increasing N2
Increasing reff,2
Increasing N2
Model
Increasing IWC'
Fit to Observations
N2=F(IWC')r
eff,2=F(T)
N2=F(IWC')r
eff,2=F(T)
Translate to Reff and IWC (use size-dist function and assume crystal habit)
T=-35C
IWC=0.01 g/cm3
IWC=0.1 g/cm3
Polycrystals Bullet Rosettes
R'eff-vs-Reff may be a problem.
Depends on habit and effective varience of size-dist.
Range of R'eff
/Reff
much small for a given habit if dist is
effectivly "uni-modal". So less of an issue in clouds with a lot of "large-particles"
Problem when only a few large particles exist.
R'eff-vs-Reff for "bi-modal" ice clouds
Sample distributions
R'eff
/Reff
as function of N2/N
1 and R'
eff
How may Vd help ?
Fall speed depends on Mass and Area of particles. Measurement of Ze weighted V
d has some size
information embedded.
Doppler vel -vs- R'eff
Function of Habit and degree of bi-modality !
Curves from bi-modal size-dist model
N2/N
1=5x10-3N
2/N
1=5x10-3N
2/N
1 = 5x10-8
N2/N
1 = 5x10-8
N2/N
1> 0.05N
2/N
1> 0.05
Summary
Results of analysis of 5 months ARM data published in GRL (no doppler)
CLARE'98 data anaylsed in similar fashion.
Will continue to investigate Vd-R'eff relationship.
ARAT Lidar/Radar Results Oct, 20 1998
Future Tasks/Plans/Ideas
Test radiative property parameterization in RTM.
Use inversion products in radiative transfer schemes and compare with surface obs.
Incorporate Doppler fall-speed info into retrieval procedure.
Extend lidar/radar procedure to space-based lidar/radar instruments (CloudSat/Calipso, EarthCARE).
Development of more advanced retrival schemes incorporating passive sensor information.
Types of Equivalentspheres
Same opt. extinction
Same Ze
Same Ze and alpha ?
Same Ze and alpha ?
Comparisions (size dists. of plates)
Comparisions (size dists. of Columns)
Backscatter still varies though !
Plates Columns
Experimental ActivitiesCentered at CABAW (center of Netherlands)
Other stations have celiometers and SW fluxmeasurements (some also with IR radiometers)
Cabaw + Network useful for CSAT/CALYPSO Validation ?
Active in:CloudNET/BBC/CliwaNet
Validation
Two JGR-Atmospherepapers (In Press)
Good agreement with IR radiometer observations(During CLARA)
Good agreement with IR radiometer observations(During CLARA)
Good comparision betweenin-situ 2-D probe and airborne lidar/radar results !(During CLARE'98)
Good comparision betweenin-situ 2-D probe and airborne lidar/radar results !(During CLARE'98)
UKMO C-130UKMO C-130INSU ARATINSU ARAT
Leandre 532 nm lidarLeandre 532 nm lidar
Kestral 94 Ghz RadarKestral 94 Ghz Radar
INSU ARATINSU ARAT
CABAW
200 meter met. tower+ expanding numberof ground-basedremote sensing equipment
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