cfh: Cryogenic Frostpoint Hygrometer

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.

Measurements

Locations

  • Fixed
  • AMF1
  • AMF2
  • AMF3

2020

Dover J, D Brewer, and M Lataille. 2020. National Weather Service Radiosonde Evaluation Field Campaign Report. Ed. by Robert Stafford, ARM user facility. DOE/SC-ARM-20-001.

2018

Stuefer M and T Gordon. 2018. Cryogenic Frostpoint Hygrometer (CFH) Instrument Handbook. Ed. by Robert Stafford, ARM Climate Research Facility. DOE/SC-ARM-TR-210.

2015

Dzambo AM, DD Turner, and EJ Mlawer. 2015. "Evaluation of two Vaisala RS92 radiosonde solar radiative dry bias correction algorithms." Atmospheric Measurement Techniques Discussions, 8(10), 10.5194/amtd-8-10755-2015.

2014

Lawson P and A Gettelman. 2014. "Impact of Antarctic mixed-phase clouds on climate." Proceedings of the National Academy of Sciences, 111(51), 10.1073/pnas.1418197111.

2008

Cady-Pereira KE, MW Shephard, DD Turner, EJ Mlawer, SA Clough, and TJ Wagner. 2008. "Improved Daytime Column-Integrated Precipitable Water Vapor from Vaisala Radiosonde Humidity Sensors." Journal of Atmospheric and Oceanic Technology, 25(6), 10.1175/2007jtecha1027.1.

2004

Ferrare RA, EV Browell, S Ismail, S Kooi, LH Brasseur, VG Brackett, MB Clayton, J Barrick, GS Diskin, J Goldsmith, BM Lesht, JR Podolske, GW Sachse, FJ Schmidlin, DD Turner, DN Whiteman, D Tobin, L Miloshevich, HE Rivercomb, BB Demoz, and PD Girolamo. 2004. "Characterization of upper-tropospheric water vapor measurements during AFWEX using LASE." Journal of Atmospheric and Oceanic Technology, 21, 10.1175/jtech-1652.1.


View All Related Publications