About HIPPO
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HIPPO II Hard-Down Day #1 :: Kona, HI
HIPPO Field Catalog
Glossary of Acronyms
Dew Point, Humidity & Water Vapor
Dew Point, Humidity & Water Vapor Instruments
- Dew Point
- PMS Liquid Water Sensor (King) (PLWC)
- RICE | Raw Icing-Rate Indicator
- VCSEL | Vertical Cavity Surface Emitting Laser
Dew Point
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PMS Liquid Water Sensor (King) (PLWC)
PMS Liquid Water Sensor (King probe) is used primarily for the study of cloud microphysical processes and in icing studies. It uses a heated wire to measure liquid water content (LWC). This instrument is relatively simple and accurate (≈ 15%) for higher liquid water content (LWC)t; however, accuracy is diminished at lower LWC since the baseline (the clear-air signal upon which the in-cloud signal is superimposed) is dependent on airspeed, temperature, and pressure. Droplets between 5- and 40-μm diameter are efficiently sampled.
RICE | Raw Icing-Rate Indicator
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VCSEL | Vertical Cavity Surface Emitting Laser hygrometer
Monitored by: Mark Zondlo
The vertical cavity surface emitting laser (VCSEL) hygrometer measures water vapor concentration throughout the troposphere and lower stratosphere at high frequency (25 times per second), precision (<3%), and accuracy (5-10%). The wide dynamic range of the VCSEL is particularly well-suited for HIPPO Global where environments range from the warm and moist marine boundary layer in the tropics to the cold and dry stratosphere in polar regions. 
In addition, the VCSEL probes atmospheric moisture in an open-path configuration exterior to the aircraft (see picture at left). The lack of an inlet or tubing (which can create sampling artifacts for a “sticky” gas like water vapor) allows for the identification of highly resolved atmospheric layers in the horizontal and vertical. The heart of the instrument is a fiberized laser that passes near infrared light between two gold-coated mirrors that form the optical measurement cell.
