Snow White ® Chilled mirror dew-point hygrometer for

Water vapour measurement in troposphere and lower stratosphere Recommended as working reference sensor Low cost chilled mirror sensor Designed for radiosonde application Light weight Accurate measurement of dew-point or frost-point Detects clouds and measures their liquid and solid content

The upper troposphere and lower stratosphere present the Chilled Mirror: greatest challenge to radiosonde relative Whereas all the operational measure relative measurements, because of the low humidity and are calibrated with respect to relative humidity, involved, (down to -80 °C) , and because of the problems the Snow White chilled mirror measures dewpoint or frost of contamination of picked up on passing point directly (depending on whether the film on the mirror through upper cloud. is water or ice) Main advantages of the chilled mirror system The new yellow “hydropor” material reduces over conventional systems are enhanced accuracy, and contamination effect, and therefore the instrument is higher measuring speed. Another advantage is the absence useful at higher altitude than previous Snow White® of saturation effect. design.

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 @ 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

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 , 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 MRS-SRS-C34/026 MRS-SRS-C34/040 Snow White 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

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