Snow White® Chilled mirror dew-point hygrometer for radiosonde

Water vapour measurement in troposphere and

lower stratosphere

Recommended as working reference sensor

Low cost chilled mirror dew point sensor

Designed for radiosonde application

Light weight

Accurate measurement of dew-point or frost-point

Detects clouds and measures their liquid and solid

water content

The upper troposphere and lower stratosphere present the

greatest challenge to radiosonde relative humidity

measurements, because of the low temperature

involved, (down to -80 °C) , and because of the problems

of contamination of water vapor picked up on passing

through upper cloud.

The new yellow “hydropor” material reduces

contamination effect, and therefore the instrument is

useful at higher altitude than previous Snow White®

design.

Chilled Mirror:

Whereas all the operational radiosondes measure relative

humidity and are calibrated with respect to relative humidity,

the Snow White chilled mirror measures dewpoint or frost

point directly (depending on whether the film on the mirror

is water or ice) Main advantages of the chilled mirror system

over conventional systems are enhanced accuracy, and

higher measuring speed. Another advantage is the absence

of saturation effect.

Technical Data ….

Nominal operating altitude 0…~24 000m (Daytime version 0… ~12 000m)

Nominal operating time max 4 hours

Measurement range 2…100%rF -40…20°C

Mirror temperature range -80°C…+40°C (Daytime version –60°C….+40°C)

Resolution 0.01°C, 0.1%rF

Accuracy 0.2°K / 2%rF DewPoint / relative humdity

Reproducability in sounding 0.2°K / 2%rF DewPoint / relative humidity, measured with double soundings

Max dew point depression @ 0°C 45K Daytime version 40K

Max dew point depression @ -60°C 25K Daytime version 20K

Response time <0.5 s 5m/s, 0°C…+40°C, 500…1000hPa

Response time <2s 5m/s, -60°C…0°C, 3…500hPa

Case material Styrofoam “Hydropor”

Power Supply 9V/0.6Ah 1.5V/18Ah Alkaline batteries (included)

Weight 530g (Daytime version 560g)

SnowWhite® chilled mirror hygrometer

Contact

Meteolabor AG

Hofstrasse 92

CH-8620 Wetzikon

Switzerland

Phone: +41 44 934 40 40

Fax: +41 44 934 40 99

E-Mail: info@meteolabor.com

Internet: www.meteolabor.com

© by Meteolabor AGAll rights reserved.

Content may change without further notice • 2008-09SnowWhite_e

Versions

Several variants of Snow White are manufactured:

The .daytime. Snow White system has the chilled mirror mounted in an internal duct to protect the sensor from daylight. The

circulation through the duct system is good once established, the speed of response of the Snow White is similar or better

than the operational radiosondes, but this good ventilation cannot be guaranteed until the test rig has accelerated up to

normal ascent rate for several minutes. At low temperatures, with relatively wet conditions in the lower atmosphere,

contamination can build up in the duct.

The .nighttime. Snow White eliminates the internal duct and the chilled mirror sensor is exposed directly in the atmosphere.

In some measurements ascents are preceded by continuous rain. In these circumstances, .daytime. Snow Whites with the

sensor in an internal duct is flown (also on the night) and some measures are recommended to prevent ingress of rain to the

chilled mirror sensor. In this case the rain protection kit is installed to reduce effect of liquid water flooding the sensor.

The conversion from dewpoint to relative humidity requires an accurate air temperature measurement. If the sensor is used

with SRS-C34 radiosonde, the same calibration is used for dewpoint and temperature measurement, which eliminates and

differential errors and leads to the best possible conversion.

A complete package including meteolabor SRS-C34 radiosonde and a complete low cost ground station, ARGUS37, is

available from meteolabor and presents the best in ease of use, handling and accuracy. Alternatively Snow White can

interface to different manufacturers radiosondes.

Warning

Do not use radiosonde in proximity to airport,

check your local regulations.

Ordering Information

Description Night version Daytime version

PTU-Radiosonde meteolabor SRS-C34 with Snow White MRS-SRS-C34/002 MRS-SRS-C34/001

PTU-GPS Radiosonde meteolabor SRS-C34 with Snow White MRS-SRS-C34/003 MRS-SRS-C34/022

PTU-GPS Reference-Radiosonde meteolabor SRS-C34 with

Snow White

MRS-SRS-C34/026 MRS-SRS-C34/040

Snow White sensor for VIZ MarkII Radiosonde MRS-ASW35/01 MRS-ASW35/00

Snow White sensor for Vaisala RS80 Radiosonde MRS-ASW35/12 MRS-ASW35/17

Snow White sensor for Modem Radiosonde MRS-ASW35/09 MRS-ASW35/08

Snow White sensor for other Radiosondes On request On request

Rain protection kit n.a. MRS-ASW-Rain-Kit

Recommended Balloon, type and size for 30km height MBA-TA1000 MBA-TA1000

Recommended Balloon, type and size for 20km height MBA-TA500 MBA-TA500

Dimensions, SnowWhite 280 x 150 x 125 210 x 260 x 90 mm

Weight including Batteries, SnowWhite Approx. 530g Approx. 560g

Dimensions, Radiosonde 345 x 210 x 100 mm 345 x 210 x 100 mm

Weight including Batteries, SnowWhite+Radiosonde Approx. 1150 g Approx. 1180 g