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H.W.J Russchenberg1, C.L. Brandau1, U. Loehnert2 and K. Ebell2

(1) International Research Centre for Telecommunication and Radar (IRCTR), Delft Technical University, The Netherlands

(2) Institute for Meteorology and Geophysics, University of Cologne, Cologne, Germany

Liquid water clouds in the Murg-valley

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CloudRadar

Microwave Radiometer

bZ aLWC

Cloud radar based retrievals of liquid water content (LWC):

Directly:simultaneous

measurements of LWC and Z:Fox/Illingworth

JPM 1997

Z

LWC

In-situ observations

Evaluation:ct

cb

LWC

( )LWP MWR

( )LWP radar

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Stratocumulus, Murg Valley

Radar reflectivity Vertical velocity Spectral width

Liquid water path

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One hour standard deviation vertical speed

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Link with liquid water path

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Some cloud statistics, Murg Valley

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Radar data analysis: approach, 1

( )radar radar

H

LWP LWC h dh

( ) ( )theoryradar radarLWC h Z h

microwave radiometerLWP

?

Z

LWC

Comparison of independent techniques

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Radar data analysis: approach, 2

radar microwave radiometerLWP LWP

? Z

LWC radarLWC Z

Suppose:

Which Z-LWC fits the equation?

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Case study: 26 October 2007, COPSLWP(radar)-LWP(radiometer)

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Case study: 26 October 2007, COPSRequired Z-LWC relationships

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Evaluation of radar-based LWC retrieval inthe Murg-valley from April-December

single layer, cloud droplets only, LWP(max)=700gm-2, geometrical thickness(min)=2 radar bins (90m), broken clouds

included

Radar discrepancy

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Analysis of cloud structure

increase of H results in a greater deviation from LWP(MWR)

Effect on the derived LWP from radar-based Z-LWC relationships

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M

M

SOP2: 21/07/2007

M M

Combination of different scales

LWC in-situ (PVM)

Radar reflectivity of 5 height bins

due to changes in flight level

Z > -50Z < -17 no drizzle

Is it always the case?

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Z-LWC relationship from in-situ data:

SOP2: 21/07/2007

Z-LWC relationshipfrom Fox/Illingworthand Atlas reproduces(albeit not perfect)radar observation on the ground

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Concluding remarks

• The observed reflectivity of stratocumulus tends to be less than expected

• We are looking for aerosol data• Be careful with aircraft measurements