analysis of arm cirrus data and the incorporation of doppler fall-velocity measurements in...

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