ON THE INSTRUMENTS FOR AIR HUMIDITY MEASUREMENTS IN 2000 YAKUTSK EXPERIMENT
M. Yu. Mezrin (1), E. V. Starokoltsev (1), T. Hiyama (3)
(1) 1) Central Aerological Observatory, Russia
(3) 2) Hydrospheric Atmospheric Research Center, Nagoya University & Frontier Observational Research System for Global Change, Japan
The experiment carried out in Yakutsk in 2000 was devoted to the investigation of the atmospheric boundary layer in the Lena area. Among the turbulent parameters under study was the turbulent water vapor flux. To determine the flux, fast-response measurements of absolute humidity had to be fulfilled. To analyze the transport processes, it was also necessary to know the mean humidity vertical distribution.
In the experiment three instruments to measure humidity were employed: Aircraft Condensation Hygrometer (ACH) to measure the mean value, Ultra-Violet Hygrometer (UVH) to measure fluctuations, and Fast Responding Closed-Path Infrared Gas Analyzer (LI-6262) served as a reference instrument.
ACH designed at CAO measures atmospheric humidity in terms of dew- or frost-point. Dew-point (or frost-point) is determined by measuring the temperature of a mirror cooled to a level at which dew or frost appears on its surface. The appearance of condensate is registered by an optical detector which can distinguish between a liquid and a solid phase.
UVH designed at CAO performs fast-response measurements of absolute air humidity fluctuations. Its operation principle is based on water vapor absorption of vacuum ultra-violet radiation at wavelengths close to the line L-a(121.6 nm) along the path between the radiation source and the receiver.
ACH and UVH sensors were mounted on the outer surface of the aircraft body in a single fairing. The working volume is ventilated in a natural way.
The operation principle of LI-6262 instrument designed by LI-COR is based on water vapor absorption in the infrared. Air samples are taken from outside the aircraft through an inlet pipe. This is done with the aid of an air pump.
An objective comparison of the data from the three instruments used shows that
1) the ratio of the instruments’ sensitivities at low frequencies is close to unity;
2) the difference between the time lags of UVH and LI-6262 instruments in measurements of absolute humidity fluctuations is not more than 0.1 s; ACH time lag is about 6 s;
0.3 s) at the output.
Submittal Information
Name :
Date :
Mezrin M. Yu.
30-May-01-16:04:17
Organization :
Theme :
Central Aerological Observatory (CAO)
Theme 1
Address :
Presentation :
3, Pervomayskaya Str., Dolgoprudny, Moscow Reg., 141700 Russia
