gerd-jan van zadelhoff & dave donovan comparing ice-cloud microphysical properties using...
TRANSCRIPT
Gerd-Jan van Zadelhoff
&
Dave Donovan
Comparing ice-cloud microphysical properties using
Cloudnet & ARM data.
2 sites: coastal Europe, 1 site: Southern great plains; USA
GOAL :Compare and evaluate microphysical cloud properties at 3 sites
1. Cabauw:
• ECMWF data (T & P)
• 35 GHz Radar
2. Chilbolton:
• ECMWF data (T & P)
• 94 GHz Radar (Galileo)
• 905 nm CT-75 Ceilometer
3. ARM:
• Sonde data (T & P)
• 35 GHz Radar
• 532 nm Micro Pulse Lidar (MPL)
• 905 nm CT-75 Ceilometer
Site Instrument Period
Oct 2001 – March 2002
Oct 2001 – June 2003
Due to problems with Galileo only Z> -20 dB is used
Nov/Dec 1996 June 1997
Jan & July 2000
Selection of cloud typed
1. Ice clouds2. Visible in both Lidar and Radar
• T < -2 oC• Radar and Lidar top of cloud are roughly the same.• Ice-clouds are optically thin.
Par
ticl
e si
zes
(R’e
ff)
Only Lidar
Both Radar and Lidar Only Radar
24-05-200211-03-2002
Selection of cloud typed
1. Ice clouds2. Visible in both Lidar and Radar
• T < -2 oC• Radar and Lidar top of cloud are roughly the same.• Ice-clouds are optically thin.
Par
ticl
e si
zes
(R’e
ff)
EXCLUDEDINCLUDED
(11 year mean of the month June, HIRS data NOAA)Wylie & Menzel (1998)
High Cloud Statistics:Frequency of cumulated IR transmissive clouds above 4 km.
Comparing vertical cloud statistics at the three sites.
Observed low clouds
ARM
Cabauw
Chilbolton
Shown is the normalized cloud height distribution FOR EACH cloud pixel detected
Example for an ice-cloud measured at Cabauw.
4 eeff αZR'
shape-
n orientatioRR'
dist. size -
- effeff
How to deal with the observed cloudsDefine the regions wherein 10, 30, 60, 90 and 99 % of all observed values reside
Calculate the mean in each x-bin (T) and the of the distribution
Plot for every cloud pixel the appropriate values (T vs R’eff)
ARM vs CABAUW
vs. Z
Doppler velocity vs. R’eff
R’eff vs. T
IWC’ vs Z
Depth from top of cloud vs. SizeIWC’
distribution
Height vs. Size
ARM vs CABAUW
Height vs.particle size
Reff vs T(complex poly-crystals)
Need to use data with Z > -20 dBz for comparison withThe GALILEO radar in the 2001-2002 period.
Dependence of the retrieved particle sizes on Z.
Height dist. of the probed clouds(with lower limit to used Z data)
Particle size versus Temperature(with lower limit to used Z data)
Z > -20 dB
-Cabauw
-ARM
-Chilbolton Depth from top of cloud vs. Size
IWC vs. Z(complex poly-crystals)
Height vs.particle size
R’eff vs. T
Seasonal influences on the low optical depth ice clouds
WINTERSPRINGSUMMERAUTUMN
HEIGHTR’eff
HEIGHT
Log10(IWC’)
R’eff
Bottom row: ARM
Top row: Cabauw
Log10(IWC’)
CONCLUSIONS
4. The cabauw site shows no seasonal dependence for the low optical depth ice-clouds studied here. The ARM site shows a small dependence.
1. Cabauw & Chilbolton show very similar results (for Z > -20 dBz)
2. Derived parameter relations depend strongly on the lowest value of Z for Z > -30 dBz
3. The ARM site has higher and thicker ice-clouds the latter results in a larger particle size distribution.
