analysis of arm cirrus data and the incorporation of doppler fall-velocity measurements in...
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![Page 1: Analysis of ARM cirrus data and the incorporation of Doppler Fall-velocity measurements in lidar/radar retrievals Outline of lidar/radar procedure. Problem](https://reader030.vdocuments.mx/reader030/viewer/2022032702/56649cea5503460f949b5d17/html5/thumbnails/1.jpg)
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.
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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
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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
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R'eff-vs-Reff for ice crystals
Must know relationship between crystal Mass and maximum dimension (D) in order to predict Reff and IWC !
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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
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April 18, 1996, CLARA
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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.
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C-130 2D vs Lidar/Radar results
D-binned A-binned
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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
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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 ?
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Bin by IWC' (not yet IWC)
IWC'=IWC (R'eff/Reff)
IWC'=IWC (R'eff/Reff)
Increasing IWC' g/m3
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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)
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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
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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.
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R'eff-vs-Reff for "bi-modal" ice clouds
Sample distributions
R'eff
/Reff
as function of N2/N
1 and R'
eff
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How may Vd help ?
Fall speed depends on Mass and Area of particles. Measurement of Ze weighted V
d has some size
information embedded.
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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
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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.
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ARAT Lidar/Radar Results Oct, 20 1998
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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.
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Types of Equivalentspheres
Same opt. extinction
Same Ze
Same Ze and alpha ?
Same Ze and alpha ?
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Comparisions (size dists. of plates)
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Comparisions (size dists. of Columns)
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Backscatter still varies though !
Plates Columns
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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
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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
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CABAW
200 meter met. tower+ expanding numberof ground-basedremote sensing equipment