A. Parrish

High concentrations of chlorine monoxide at low altitudes in the Antarctic spring stratosphere: diurnal variation

The Stony Brook ground-based remote sensing mm-wave spectrometer was used to measure chlorine monoxide in the stratosphere over McMurdo Station, Antarctica during the austral spring of 1986. From the data collected, we find strong evidence for abnormally high concentrations of CIO at low altitudes—as much as two orders of magnitude greater than standard theories predict at 20-km altitude at mid-latitudes. This low-altitude CIO changes cyclically on a diurnal basis, and also secularly during the September–October observing period. A study of the diurnal variation of the low-altitude ClO is presented here. We conclude that chlorine is crucially involved in the springtime destruction of Antarctic ozone.

Diurnal variation of stratospheric chlorine monoxide: a critical test of chlorine chemistry in the ozone layer.

This article reports measurements of the column density of stratospheric chlorine monoxide and presents a complete diurnal record of its variation (with 2-hour resolution) obtained from ground-based observations of a millimeter-wave spectral line at 278 gigahertz. Observations were carried out during October and December 1982 from Mauna Kea, Hawaii. The results reported here indicate that the mixing ratio and column density of chlorine monoxide above 30 kilometers during the daytime are ∼ 20 percent lower than model predictions based on 2.1 parts per billion of total stratospheric chlorine. The observed day-to-night variation of chlorine monoxide is, however, in good agreement with recent model predictions, confirms the existence of a nighttime reservoir for chlorine, and verifies the predicted general rate of its storage and retrieval. From this evidence, it appears that the chlorine chemistry above 30 kilometers is close to being understood in current stratospheric models. Models based on this chemistry and measured reaction rates predict a reduction in the total stratospheric ozone content in the range of 3 to 5 percent in the final steady state for an otherwise unperturbed atmosphere, although the percentage decrease in the upper stratosphere is much higher.

A quasi-continuous record of atmospheric opacity at λ = 1.1 mm over 34 days at Mauna Kea observatory

A quasi-continuous record of atmospheric attenuation is obtained. The data were gathered during a 24-day period in September and October 1982 and a 10-day period in December of that year. The opacity is arrived at by measuring the thermal emission of the atmosphere over a bandwidth of approximately 300 MHz. Using an experimental relationship established by Zammit and Ade (1981), opacity measurements at 1.1 mm are converted to the precipitable water vapor column overhead. With the precipitable water vapor, estimates of opacity due to water vapor can be made for other mm and FIR wavelengths. These estimates require model absorption curves for the atmosphere.

Quantitative Observations of Stratospheric Chlorine Monoxide as a Function of Latitude and Season During the Period 1980 – 1983

Results are presented for the Cl0 column density between ~30–35 km, and the mixing ratio at 38 km, from data taken during the period January 1980 to Dec. 1983. These data were taken from three different locations, at 42°, 32° and 20°N. We contrast the limited variation observed in this data set with the substantially large variations observed by the in-situ resonance fluorescence observations of Anderson, et al.

Additional atmospheric opacity measurements at lambda = 1.1 mm from Mauna Kea Observatory, Hawaii

Atmospheric opacity values in the zenith direction are given for a wavelength of 1.1 mm (278 GHz) at the summit of Mauna Kea in the Hawaiian Islands. A total of 75 days is covered during the period 1983–1986. Observations were made on a quasi-continuous basis, with opacity measured every 20 minutes around the clock for significant periods of time. A conversion from opacity at λ=1.1 mm to the equivalent preciptable water vapor column is given from the measurements of Zammit and Ade, from which opacities at other wavelengths may be derived. The data presented here supplement those in an earlier paper covering 34 days in the fall of 1982.

Measurement of atmospheric opacity at 278 GHz at McMurdo Station, Antarctica in austral spring seasons, 1986 and 1987

We present a quasi-continuous record of measured atmospheric opacity obtained at 278 GHz (1.1 mm wavelength) from McMurdo Station, Antarctica during austral spring seasons in 1986 and 1987. McMurdo Station, at 78°S, 166°W, is easier to access than the Amundsen-Scott (South Pole) Station, although representing a warmer, sea level site with substantially higher typical opacity: the present record may be of interest to those contemplating mm-wave astronomical or atmospheric observations within the Antarctic region. Observations were made over a 256 MHz bandpass in 1986, during the period August 30 to October 30. In 1987, a 512 MHz bandpass was used, and observations were made during the period September 4 to October 13. All data are reduced to represent opacity in the zenith direction, and measurements were taken approximately every 20 minutes, except during storms or other periods of high opacity. The periods covered represent transitions from the polar winter towards summer conditions, and thus represent neither the best nor the worst that this site has to offer.

Vertical Profiles and Column Density Measurements of Ozone from Ground-Based MM-Wave Spectroscopy at Mauna Kea, Hawaii a Demonstration of Capabilities

Using ground-based microwave techniques, we have observed the pressure broadened emission line of stratospheric ozone at 273.0509 GHz, due to the 181,17 →180,18 transition in the ground vibrational state of 1603. Observations were made at approximately 23h local time on 8, 9, 10 and 11 June 1983 from the Mauna Kea Observatory, on the island of Hawaii, at latitude 19°8 N, and an altitude of 4.2 km. The integration time for each observation was 20 minutes, which under good conditions at this high, dry site gives a signal/noise (ratio of peak intensity of line to rms of noise). of 500 or better, at our maximum frequency resolution of 1 MHz/channel, and even higher if the data is smoothed over a few channels.