cfh

The cryogenic frostpoint hygrometer (CFH) is a small, balloon-borne instrument that provides highly accurate measurements of water vapor in the atmosphere. The CFH has a significantly greater sensitivity to water vapor than standard radiosondes, as it can measure the frostpoint or dewpoint temperatures at an accuracy better than 0.2 K corresponding to water volume mixing ratio accuracies of only a few parts per million.

The main instrument component is a small mirror, which is cooled by a cryogen in order to be covered with a thin layer of water vapor condensate. A pair of photodiodes detects the condensation on the temperature-controlled mirror. The phase of the condensate is controlled by a force-freezing algorithm, allowing for clear interpretation of the dew point versus frostpoint.

The replacement of analog electronics with a microprocessor, a feedback controller, and thermistor calibration have improved accuracy and performance of the CFH over its predecessors. Further characteristics like reduced power consumption and low instrument weight made the CFH a successful instrument to perform in situ balloon-borne measurements of water vapor in the upper troposphere and lower stratosphere. CFH measurements are now used worldwide to validate radiosonde, satellite, and ground-based profiler measurements.

Wind speed calculated from GPS location measurements
Ambient temperature from the radiosonde
Saturation vapor pressure calculated from CFH frost point temperature
Pressure from the radiosonde pressure sensor

Southern Great Plains - Central Facility, Lamont, OK

• Latitude: 36.607322
• Longitude: -97.487643
• Publication Date: 2014-09-11
• Start Date: 2014-09-11
• End Date: 2019-12-18
• Last Updated: 2020-02-12

https://www.arm.gov/connect-with-arm/organization/instrument-mentors/list#cfh

Martin Stuefer

University of Alaska Fairbanks

Telayna Wong

University of Alaska Fairbanks

http://dx.doi.org/10.5439/1355409
Atmospheric Radiation Measurement (ARM) user facility. 2014. Cryogenic Frostpoint Hygrometer (CFH). 2014-09-11 to 2019-12-18, Southern Great Plains (SGP) Central Facility, Lamont, OK (C1). Compiled by M. Stuefer, B. Ermold and T. Wong. ARM Data Center. Data set accessed at http://dx.doi.org/10.5439/1355409.