1
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
2
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
3
Stratocumulus, Murg Valley
Radar reflectivity Vertical velocity Spectral width
Liquid water path
4
One hour standard deviation vertical speed
5
Link with liquid water path
6
Some cloud statistics, Murg Valley
7
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
8
Radar data analysis: approach, 2
radar microwave radiometerLWP LWP
? Z
LWC radarLWC Z
Suppose:
Which Z-LWC fits the equation?
9
Case study: 26 October 2007, COPSLWP(radar)-LWP(radiometer)
10
Case study: 26 October 2007, COPSRequired Z-LWC relationships
11
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
12
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
13
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?
14
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
15
Concluding remarks
• The observed reflectivity of stratocumulus tends to be less than expected
• We are looking for aerosol data• Be careful with aircraft measurements