Douglas Spangenberg 1 , Patrick Minnis 2 , Michele L. Nordeen 1 , Sunny Sun-Mack 1

4th PAN-GCSS Meeting/Polar Clouds Working Group

NASA Langley Research Center / Atmospheric Sciences

Toulouse, France 2-6 June 2008

Cloud Property Retrievals over the Arctic from the NASA A-Train Satellites Aqua, CloudSat and CALIPSO

Douglas Spangenberg1, Patrick Minnis2,

Michele L. Nordeen1, Sunny Sun-Mack1

and Q. Z. Trepte1

1- Science Systems and Applications, Inc, Hampton, VA, USA

2- NASA Langley Research Center, Hampton, VA, USA




NASA A-Train Constellation

CloudSat (Radar) Aqua

(MODIS)

CALIPSO (Lidar)

0.5-2 min15 sec




North Pole A-Train Orbit Tracks: April 19, 2008




A-Train Satellites

Aqua:• Passive MODIS sensor•1km res pixels sub-sampled to 2 km for cloud property retrievals• Channels used for cloud detection, cloud property retrievals (NASA CERES algorithm): 0.65, 2.1, 1.38, 3.7, 6.7, 7.3, 8.5,11,12,13.3 m - Original Algo, Cloud Detection/Phase, Cloud-Top Altitude• Cloud Properties: Z,T, Phase, , LWP, IWP, Particle Size

CALIPSO: • Cloud-Aerosol lidar with 532, 1064 nm channels• 0.33-5.0 km horizontal res; 30, 60 m vertical res• Cloud properties: N layers, T, Z, Phase, , IWP• Lidar attenuates after =5; often can’t see to cloud base

CloudSat: • 94 GHz Cloud Profiling Radar• 2.5x1.4 km horizontal res; 240 m vertical res• Cloud properties: , LWC/LWP, IWC/IWP, Particle Size




A-Train Cloud Analysis, 22:25 UTC Apr 19, 2008R: 0.65 mG: 3.7-11 mB: 11 m

Aqua Cloud Phase Aqua Optical Depth

Aqua RGB Aqua 11m BT

A-Train




A-Train Cloud Analysis: 22:25 UTC Apr 19, 2008

CALIPSO VFM

CALIPSO Phase

A-Train

Aqua Cloud Phase





CloudSat Reflectivity

CloudSat Ice Re

CloudSat IWC

Aqua 11m BT

A-Train





CloudSat LWC

CloudSat Liq ReAqua Liquid Re

A-Train




Aqua-MODIS Validation

• Compare CERES Aqua-MODIS cloud property retrievals to CloudSat/CALIPSO retrievals (passive vs active sensor retrievals)

• Results from April 2008 afternoon/daytime overpasses, 22-23:30 GMT

• ARM/ISDAC field experiment flight days

• Region: 60-80N; 130-180W

• Nearest 4 Aqua-MODIS pixels along CloudSat/CALIPSO track used

• CALIPSO & CloudSat data points matched to within 4 km, 4 min





Scene Type % Match NCloud 68 2968Clear 84 299Ice 64 (28) 998Liq/Mixed 92 (93) 572

Cloud Amount & Phase Matching between CALIPSO & Aqua:

Scene Type Amount (%)

N

All Clouds 89 3452Ice Clouds 68 2632Liq/Mix Clouds 21 817

CALIPSO Scene Types Sampled:

• Results valid for CALIPSO upper-most cloud layer





Cloud Top Height, CALIPSO vs Aqua:

CALIPSO mean: 5.24 kmAqua mean: 4.39 kmAqua bias: -0.85 km





Ice Crystal Effective Diameter, CloudSat vs Aqua:




New Aqua-MODIS Multilayer Cloud Property Retrievals

Aqua Optical Depth

Low-Level ZtopSL/UL Ztop

April 19 2008, 22:20 GMT

• Uses 13.3 m channel/CO2 slicing to detect multilayer clouds •, Re, T, Z, for low (liquid) layer• Can improve ice cloud detection by adjusting highest cloud top upward




Summary & Future Work

• CALIPSO, CloudSat provide data for validating Aqua-MODIS cloud property retrievals on a continuous basis over remote Arctic/Antarctic. • A-Train data can be compared with cloud model data & retrievals from passive sensors on geo satellites (validation studies). • CALIPSO reported combinations of ice and liquid phase in low level Arctic clouds rather than reporting mixed phase.

• Problem in CloudSat data for clouds below ~1km, to hopefully be resolved.

• In-situ data obtained during field experiments will provide valuable data for validating CALIPSO/CloudSat retrievals (ISDAC/AK-Apr 2008).




Summary & Future Work

• Comparisons between Aqua passive sensor retrievals and active sensor retrievals of CALIPSO show good agreement for cloud amount, phase, height.

• Comparisons between Aqua and CloudSat , particle size, LWP/IWP showed larger discrepancy which needs to be resolved - Account for differences inherent in retrievals methods - Improve Aqua-MODIS retrieval techniques for polar clouds

• Multilayer Aqua-MODIS cloud algorithm should be able to provide improved retrievals for high ice clouds and low mixed/liq clouds.

• Web Pages for Information/Data Access:- CALIPSO: http://www-calipso.larc.nasa.gov/- CloudSat: http://cloudsat.atmos.colostate.edu/data/

Douglas Spangenberg 1 , Patrick Minnis 2 , Michele L. Nordeen 1 , Sunny Sun-Mack 1

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