Measurements Of Atmospheric Water Vapor Research Articles

Atmospheric water vapour measurements at Zelenchukskaya (U.S.S.R.) and La Silla (Chile)

Direct measurements of atmospheric precipitable water vapour are presented for Zelenchukskaya at the site of the 6 m telescope. The data may be compared with previous data and with indirect determinations based on extinction measurements at 1 mm interpreted in terms of experimental water vapour transmittance measurements. It is shown that the cosecant law is justified in practice. Indirect measurements of water vapour at the European Southern Observatory, La Silla show that precipitable water vapour may be less than 2 mm for ∼ 50% of the southern hemisphere winter time. A low value of 0.6–0.7 mm is reported.

Measurements of atmospheric water vapor with microwave radiometry

A dual‐channel, ground‐based microwave radiometer, working at the frequencies 21.0 and 31.4 GHz, an infrared spectral hygrometer, and radiosondes have been used for comparative measurements of the integrated amount of precipitable water vapor in the atmosphere over a period with zenith water vapor contents varying between 6 and 26 mm. The microwave radiometer was found to give comparable or better formal accuracy than the radiosondes, the absolute accuracy of which is believed to be about 1 mm. The rms difference of the integrated amount of water vapor in the zenith direction measured with the microwave radiometer and with radiosondes was 1.2 mm for all data, and 0.8 mm for a selected group of good weather data. These are lower formal errors than previously reported. It is shown that the simplified relation between the radiometer antenna termperatures and the integrated amount of water vapor in this case contributes with a formal error of about 0.3 mm. It is suggested that mean ground weather data can be used to adapt this relation to other sites and seasons.

Rapid extraction of layer relative humidity, geopotential thickness, and atmospheric stability from satellite sounding radiometer data

Layer moisture and temperature are important variables for forecasting local weather phenomena. The purpose of ths paper is to present a method to rapidly compute layer average relative humidities and geopotential thicknesses from satellite measurements of atmospheric water vapor and oxygen radiation emission to space. Both polar-orbiting and geostationary satellite data are considered. Analyses show that the relative humidity and geopotential thickness patterns from satellite data are consistent with radiosonde data. The relative humidity calculation is insensitive to the assumed temperature profile condition. It is shown that time variations of the atmospheric moisture can be monitored from a GOES-4 VAS sequential image. Also an attempt is made to derive the atmospheric stability index, total-totals, by use of satellite derived relative humidities and geopotential thicknesses. The results show good correspondence between the derived stability patterns and subsequent convective weather.

Measurements of water vapor in Mars' Antarctic

A complete Mars year of measurements of atmospheric water vapor in the south arctic have been obtained from the Viking Orbiters. Analysis of the observations indicates that, except for the south remnant cap, the southern hemisphere of Mars is devoid of any substantial reservoirs of water in contact with the atmosphere, and that, in the summer time, the top layer of soil is desiccated. Small amounts of water ice are incorporated into the annual CO 2 cap; this water is released at the cap margin when it retreats in the spring. The first global dust storm resulted in heating of the south arctic atmosphere and a transport of water in from the equatorial region. The second global dust storm had a negligible effect on atmospheric water vapor; the dust contained little water.

The Seasat scanning multichannel microwave radiometer (SMMR): Instrument description and performance

The scanning multichannel microwave radiometer (SMMR) is an imaging 5-frequency radiometer flown on the Seasat and Nimbus-7 earth satellites launched in 1978. It measures dual-polarized microwave radiances from the earth's atmosphere and surface, primarily for the purpose of deriving global and nearly all-weather measurements of sea surface temperature, wind speed, and atmospheric liquid water and water vapor. This paper describes the SMMR instrument and its calibration, antenna pattern measurements, and data processing procedures. Analysis of early data from the Seasat SMMR shows that the expected engineering performance in flight was achieved, and the measurement of sea surface temperature and wind speed with accuracies of 1.5 K and 2 m/s, respectively, may be achievable once the geophysical data processing algorithms and analysis have been completed.

Measurements of atmospheric water vapour using the absorption band at 7250 cm -1

Measurements of the integrated absorption of the 7250 cm -1 (1.38 μm) band of water vapour have been made for a 0.5 km horizontal path through the atmosphere. Using published band intensities the absorption values were converted to precipitable water amounts which were found to be about 10% smaller than values determined by wet and dry hygrometry. This difference is probably caused by inaccuracies in the published line parameter values, particularly those involving high rotational energy.

Atmospheric Water Vapor Measurements at Mizuho Camp, East Antarctica in 1976-1977

1976年11月30日から1977年1月21日まで,みずほ観測拠点において水蒸気量の測定を行った.測定期間中,相対湿度は30～80%の値を示し,低気圧の影響を受けている期間は,斜面下降風に支配されている気象状況のときよりも高い相対湿度が観測された.水蒸気量が測定された気温範囲は,-6.5℃から-22.8℃であった.水蒸気量の測定結果から,この測定期間中の雪面からの昇華量が計算された.計算結果は雪尺測定による消耗量の2～3倍になった.

Atmospheric water vapor measurements with an infrared (10-μm) differential-absorption lidar system

We report the recent design, construction, and operation of the first infrared differential-absorption lidar system for remote range-resolved sensing of gaseous species. The target gas in the present case was water vapor, which was measured using several CO2 laser lines near 10.3 μm. Profiling of the concentration of many air pollutants to a horizontal range of at least 12 km appears feasible with commercially available components.

Very Long Baseline Interferometry for centimeter accuracy geodetic measurements

Very Long Baseline Interferometry (VLBI) is one of the most promising of the new techniques for very accurate measurements (a few centimeters) of the distance between widely separated points on the earth, and for precise measurements of variations in Universal Time (UT.l) and polar motion. VLBI experiments conducted in 1972 and 1973 with radio telescopes 3900 km apart yielded values for the baseline length with a weighted root-mean-square spread about the weighted mean of 12 cm. The UT.1 and polar motion ( x-component) variations determined from these measurements were comparable to BIH values. The major error source in these VLBI measurements in the calibration of the delay contributions of the neutral atmosphere and ionosphere. We plan to improve the accuracy to the 5-cm level by: 1. (1) the addition of simultaneous measurements of atmospheric water vapor with microwave radiometers boresighted with the VLBI antennas; 2. (2) simultaneous VLBI measurements at 2.3 and 8.4 GHz for calibration of the io nsphere; 3. (3) using a new wideband data acquisition system for improving the signal/noise ratio and calibration of residual instrumental biases; and 4. (4) using improved models for known geophysical effects including earth tides, diurnal polar motion, etc. The first application planned for the 5-cm VLBI is the measurement of the distance and motion of Hawaii relative to stations on the North American Plate in California, Alaska, and Massachusetts.

Atmospheric water vapour measurements in Norway from 1972 to 1974

During an astronomical i.r.-site testing program in Norway from 1971 to 1974, atmospheric water vapour measurements have been performed mainly in the northern part of the country. The lowest monthly mean of the precipitable water content was 2.7 mm. The variation of the water vapour content during daytime was pronounced.

Atmospheric water vapor measurement by Raman Lidar

Measurements of atmospheric water vapor using the Raman backscatter from a pulsed laser were directly compared with measurements from meteorological instruments located on a tower. The experimental conditions and precautions required in making these observations in the atmosphere are discussed. The results indicate that water vapor profile measurement to a range of approximately 4 km is feasible with the lidar used in this experiment.

Passive Microwave Spectrum Measurements of Atmospheric Water Vapor and Clouds

Cloud structure, atmospheric water vapor and liquid water contents from passive ground based microwave spectrum measurements

Atmospheric water vapor measurements at 6–7 microns from a satellite

Measurements from an artificial satellite of the long wavelength (terrestrial) radiation emitted and reflected from the earth and its atmosphere should offer some insight on the vertical distribution of temperatures and on the strati~cation of the radiating gases”). The intensity of the total spectrum from about 5 to more than 100~ will not be very useful for his purpose. It is necessary to separate narrow spectral bands by means of filters or even spectrometers. As a partial problem, we will investigate the kind of information yielded by a measurement within the water vapor spectrum-either in the ~6.3~ band or somewhere in the rotation band. We will not enter here into inst~men~l details but simply assume that we have at our disposal a device to measure the radiation between 6 and 7,~ Then the radiation shall be computed which within this wavelength band is emitted by the atmosphere to a suitable radiation receiver outside the atmosphere. The atmosphere is considered to be horizontally stratified in parallel and plane layers. The curvature of the earth’s surface as well as of the radiation beams is neglected. In this spectral region only the water vapor must be taken into consideration as a radiating gas. The water vapor mass may be defined by

Meteorological Sounding Systems

A survey is presented of past and present systems for obtaining direct measurements of atmospheric wind, pressure, temperature, and water vapor. Estimates are included of the types of horizontal- and vertical-sounding systems which will be in field use within the next decade.

AN IMPROVED ELECTRONIC DEW-POINT HYGROMETER

Abstract After a theoretical discussion of the basic physical principles involved in the dew-point method of hygrometry, which serves to establish the inherent advantages of the technique, the paper describes the operating principles and the design of an improved, automatic, electronic dew-point hygrometer for laboratory or field use. The instrument makes use of photoelectric detection of condensation on a cooled, polished metal mirror combined with a radio-frequency induction heating system and an all-electronic proportional heat-control servo system. The instrument makes possible the continuous and automatic measurement of atmospheric water-vapor under all conditions of temperature with nearly constant accuracy and small lag.