Intercomparisons of Radiosonde Humidity Data and Cirrus Cloud Observations during IHOP_2002

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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 Water Cycle Initiative Support
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The reference radiosonde system for IHOP_2002

• Swiss Radiosonde C34
• SW chilled-mirror DP hygrometer
• reference humidity sensor
• Carbon hygristor
• Copper-constantan thermocouple
• Hypsometer

Vaisala RS80 NWS VIZ B-2
Reference radiosonde
400MHz transmitter GPS receiver
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SnowWhite Chilled-mirror dewpoint hygrometer
Scattering light detector
Heated sensor housing
Reflecting light detector
Thermocouple Mirror
Peltier

• Fast response
• No influences of radiation, wind and others

• Accurate measurement of dew/frost point
• Detects clouds and estimates their liquid/solid
  water
• Needs no individual calibration and
  recalibration after recovered

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RS with NWS VIZ (7)
RS with Vaisala RS80H (7) and RS80A (2)
RS80H v.s. RS90
Reference sonde with Vaisala RS80-H (7) and
RS80-A (2).
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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.

Courtesy of Larry Miloshevich for correcting the
sounding
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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.

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Comparisons between SnowWhite and Carbon
Hygristors
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Summary

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• Typical accuracy
• Requirements for synoptic meteorology

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(No Transcript)
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Cirrus clouds detected by SnowWhite thick cirrus
Surface Report Cirrus anvil (moon visible
through cirrus)

Satellite image from UW-Madison CIMSS web page
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Cirrus clouds detected by SnowWhite thin cirrus
Not visible in GOES-8 VIS image and
cloud-top-pressure image
Satellite image from UW-Madison CIMSS web page
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Lidars at 20Z on May 30
Courtesy Geary Schwemmer, NASA/GSFC
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NAST-I on Proteus on May 30
Preliminary analysis
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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 1739 Homestead RS80-H, SRL, HARLIE
6/17 1801 Homestead RS80-H, SRL, HARLIE BLH
6/18 1752 Homestead RS80-H, SRL, HARLIE CI
6/20 0330 Homestead RS80-H, SRL, HARLIE, Satellite E LLJ
6/03 18Z Dodge City and large area LASE, NAST-I, Satellite M LLJ
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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)

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Important Notes about IHOP Reference Radiosonde
and Dropsonde Data

• Do not use reference sonde pressure and wind
  data
• The reference sonde (RS) uses a hypsometer to
  measure pressure. Unfortunately the hypsometer
  was not stable and has all kinds of problems.
• 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
• There are uncertainties in the flight level
  heights which are used as a reference by ASPEN to
  integrate geopotential altitudes.
• 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.