Intercomparisons of Radiosonde Humidity Data and Cirrus Cloud Observations during IHOP_2002

NCAR Atmospheric Technology Division

Intercomparisons of Radiosonde Humidity Data and Cirrus Cloud Observations during IHOP_2002

Junhong (June) WangNCAR 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


The reference radiosonde system for IHOP_2002

400MHz transmitter

GPS receiver

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


SnowWhite Chilled-mirror dewpoint hygrometer SnowWhite Chilled-mirror dewpoint hygrometer

• 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

ThermocoupleMirror

Peltier

Scattering light detectorReflecting light detector

Heated sensor housing


RS with Vaisala RS80H (7) and RS80A (2)

RS with NWS VIZ (7)

RS80H v.s. RS90


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


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.


Comparisons between SnowWhite and Carbon Hygristors

No response

Slow response


Summary

±5%:•Typical accuracy

•Requirements for synoptic meteorology



Cirrus clouds detected by SnowWhite – thick cirrus

Surface Report: Cirrus anvil (moon visible through cirrus)

*

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

Homestead(SRL, HARLIE)

Norman/ARM-B6 (RS80H/RS90)

Amarillo (RS80H)

DC8 (LASE)

Proteus (NAST-I)

Satellite image from UW-Madison CIMSS web page


LASE on DC-8

Courtesy Ed Browell, NASA/LARC

Lidars at 20Z on May 30

NASA HARLIE

NASA SRL

Courtesy David Whiteman and

Belay Demoz, NASA/GSFC

Courtesy Geary Schwemmer, NASA/GSFC


NAST-I on Proteus on May 3018:42-21:29Z

21:29-23:48Z

300mb

200mb

200mb

300mb

~20Z around Homestead

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


BLH


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


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)


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.

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Intercomparisons of Radiosonde Humidity Data and Cirrus Cloud Observations during IHOP_2002

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