Intercomparisons of Radiosonde
Humidity Data and Cirrus Cloud
Observations during IHOP_2002
Junhong (June) Wang
NCAR Atmospheric Technology Division
Collaborators: Dave Carlson, Dave Parsons, Terry Hock, Dean Lauritsen, Hal Cole, Kate
Beierle, and Ned Chamberlain (NCAR/ATD), Dan Zhou (NASA)
NCAR Atmospheric Technology Division
NCAR Water Cycle Initiative Support
The reference radiosonde system for IHOP_2002
Swiss Radiosonde C34
•SW chilled-mirror DP hygrometer
– reference humidity sensor
•Carbon hygristor
•Copper-constantan thermocouple
•Hypsometer
Reference
radiosonde
400MHz transmitter
GPS receiver
NCAR Atmospheric Technology Division
Vaisala RS80
NWS VIZ B-2
SnowWhite Chilled-mirror dewpoint hygrometer
Scattering light detector
Heated sensor housing
Reflecting light detector
Thermocouple
Mirror
Peltier
• Accurate measurement of dew/frost point
• Fast response
• Detects clouds and estimates their liquid/solid water
• No influences of
radiation, wind
and others
• Needs no individual calibration and recalibration after recovered
NCAR Atmospheric Technology Division
RS with NWS VIZ (7)
RS with Vaisala RS80H
(7) and RS80A (2)
RS80H v.s. RS90
NCAR Atmospheric Technology Division
Comparisons between SnowWhite and Vaisala RS80-H
•Vaisala RS80-H with the sensor boom cover
agrees with the SW very well in the middle and
lower troposphere, but has dry biases in the UT.
•The TD and time-lag corrections reduce the
differences but not enough.
NCAR Atmospheric Technology Division
Courtesy of Larry Miloshevich for correcting the sounding
Comparisons between Vaisala RS80H (Norman) and RS90 (ARM-B6)
WHY?
•Not sampling the
same air mass? No
•Solar heating of
RS90? No (no
day/night difference)
• Faster response of
RS90? No
•Warmer RS90 T?
Not through
calibration, maybe
warmer humidity
sensor boom.
NCAR Atmospheric Technology Division
Comparisons between SnowWhite and Carbon Hygristors
No response
Slow response
NCAR Atmospheric Technology Division
Summary
±5%:
•Typical
accuracy
•Requirements
for synoptic
meteorology
NCAR Atmospheric Technology Division
NCAR Atmospheric Technology Division
Cirrus clouds detected by
SnowWhite – thick cirrus
Surface Report: Cirrus anvil
(moon visible through cirrus)
*
NCAR Atmospheric Technology Division
Satellite image from UW-Madison CIMSS web page
Cirrus clouds detected by
SnowWhite – thin cirrus
Not visible in GOES-8 VIS image
and cloud-top-pressure image
GOES8 VIS 2000 UTC 5/30
Dodge City
Proteus (NAST-I)
DC8 (LASE)
Homestead
(SRL, HARLIE)
Amarillo (RS80H)
NCAR Atmospheric Technology Division
Norman/ARM-B6
(RS80H/RS90)
Satellite image from UW-Madison CIMSS web page
NASA SRL
LASE on DC-8
Courtesy David Whiteman and
Belay Demoz, NASA/GSFC
Courtesy Ed Browell, NASA/LARC
NASA HARLIE
Lidars at 20Z
on May 30
Courtesy Geary Schwemmer, NASA/GSFC
NCAR Atmospheric Technology Division
NAST-I on Proteus on May 30
~20Z around Homestead
18:42-21:29Z
200mb
300mb
21:29-23:48Z
200mb
300mb
NCAR Atmospheric Technology Division
Preliminary analysis
Cases for IHOP cirrus cloud intercomparisons
Date
UTC
Center Location
Intercomparison
Data
Missions
5/30
~20 (18-23)
Homestead and
large area
SRL, HARLIE,
LASE, NAST-I
BLH
5/28
17:39
Homestead
RS80-H, SRL,
HARLIE
6/17
18:01
Homestead
RS80-H, SRL,
HARLIE
BLH
6/18
17:52
Homestead
RS80-H, SRL,
HARLIE
CI
6/20
03:30
Homestead
RS80-H, SRL,
HARLIE, Satellite
E LLJ
6/03
~18Z
~Dodge City and
large area
LASE, NAST-I,
Satellite
M LLJ
NCAR Atmospheric Technology Division
Summary and Future Work
• Vaisala RS80-H with the new sensor boom cover agrees with the
SW very well in the middle and lower troposphere, but has dry biases
in the upper troposphere (UT).
• Systematic and significant differences between RS80-H and RS90
humidity data are found, and will be investigated in detail.
• VIZ carbon hygristor has time-lag errors throughout the troposphere
and fails to respond to humidity changes in the UT, sometimes even
in the middle troposphere.
• The SW can detect cirrus clouds near the tropopause and possibly
estimate their ice water content (IWC).
• SW-estimated cirrus cloud properties will be compared
quantitatively with remote sensing data. (“IHOP cirrus cloud
comparisons” meeting at 12-1 pm on Tuesday at Room 1003)
NCAR Atmospheric Technology Division
Important Notes about IHOP Reference
Radiosonde and Dropsonde Data
• Do not use reference sonde pressure and wind data:
1. The reference sonde (RS) uses a hypsometer to measure pressure.
Unfortunately the hypsometer was not stable and has all kinds of
problems.
2. We didn't correct balloon swing at all for winds and had quite big
balloon swing because of bigger balloons used.
• Do not use dropsonde geo-potential altitude data:
1. There are uncertainties in the flight level heights which are used as a
reference by ASPEN to integrate geopotential altitudes.
2. There are no flight level PTU data for any of the Lear jet soundings
because there were no PTU sensors on board, and for some of the
Falcon soundings there is no flight level PTU data because while
there were PTU sensors, the data was manually entered and
therefore its accuracy is unknown.
NCAR Atmospheric Technology Division