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CAMEX-4 NOAA Lyman-alpha Total Water Hygrometer Table of Contents
The Principal Investigator on the NOAA Lyman-alpha Total Water Hygrometer is Kenneth Kelly of the NOAA Aeronomy Lab located in Boulder, Colorado. The instrument was flown during the fourth field campaign in the CAMEX series (CAMEX-4). CAMEX-4 ran from 16 August to 24 September 2001 and was based out of Jacksonville Naval Air Station, Florida, and included missions in the Gulf of Mexico, Caribbean and Western Atlantic. The experiment focused on the study of tropical cyclone (hurricane) development, tracking, intensification, and landfalling impacts using both NASA-funded aircraft and surface remote sensing instrumentation. Instrument InformationHygrometers measure water. Some measure water vapor content, some measure liquid water. The NOAA Lyman-alpha Total Water Hygrometer measures the amount of all water that enters the sensor, be it in any form-- solid, liquid or gas. The instrument ionizes the water molecules themselves as they pass through. Using a high intensity direct current discharge lamp, light at 121.6nm (called Lyman-alpha light) photodissociates water molecules producing excited OH radicals. Fluorescence is produced as the OH radical emits photons at 309nm. Making use of a phototube sensitive to this wavelength and a counter, the amount of OH can be calculated. The ambient air in the sample diminishes this signal by an amount proportional to the mixing ratio, so knowing the ambient pressure and temperature yields the mixing ratio from which the total water is determined. The instrument is periodically calibrated in flight by injecting a known amount of water vapor directly into the sample. A one-page information sheet about the NOAA Lyman-alpha Total Water Hygrometer may be found here, and a more lengthy history of the NOAA Lyman-alpha Hygrometer experiments may be found here. Data Naming Conventions and FormatFiles are daily with the following file naming convention: c4enlh_2001.ddd_01-fff.asc where ddd is the day of the year, and fff is the unique ER-2 flight number. The data is in ASCII, and begins on line #22: in this example, data from the middle of the dataset has been inserted following the ellipses to show data from altitude and is self-explanatory.
Kelly, K. K., et al., “Dehydration in the lower Antarctic stratosphere during late winter and early spring, 1987”, J. Geophys. Res., 94, 11317, 1989. Kelly, K. K., et al., “A comparison of ER-2 measurements of stratospheric water vapor between the 1987 Antarctic and 1989 Arctic airborne missions”, Geophys. Res. Lett., 17, 465, 1990. Kelly, K. K., et al., “Water vapor and cloud water measurements over Darwin during STEP 1987 tropical cloud mission”, J. Geophys. Res., 98, 8713, 1993. Knollenberg, R. G., et al., “Measurements of high number densities of ice crystals in the tops of tropical cumulonimbus”, J. Geophys. Res., 98, 8639, 1993. Contact InformationTo order these data or for further information, please contact:
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