Simultaneous ozone and polar stratospheric cloud observations ...
phenomena, for example, blowing snow and diamond dust, which have a strong influence on emission measurements taken from the ground. To achieve better signal-to-noise ratio, the scheduling program that usually takes data every 12 hours needs to be changed to more frequent measurements during clear-sky conditions. The data collection is fully automated needing a minimum of attention. The table shows values for water vapor in vertical column amounts and precipitable water contents for the South Pole for 1989-1990. The figure shows the water and nitric acid lines both measured and calculated for five dates from 6 December 1989 through 7 September 1990. The value of 2.0 * 10 16 molecules per centimeter for nitric acid is typical for the South Pole during the austral summer (Jones 1992). Both projects were supported by National Science Foundation grant DPP 89-17643 and by the National Aeronautics and Space
Administration. The first project was also supported by the DSIR and the New Zealand Antarctic Program.
Simultaneous ozone and polar stratospheric cloud observations at Amundsen-Scott South Pole Station during winter and spring 1991
ing aerosols at mid-latitudes. Briefly, the instrument measures the amount of locally backscattered light at two wavelengths from a flash-lamp beam. The final data product is essentially the same as that of lidar systems, but with comparatively high resolution (about 30 meters). All instruments are calibrated before flight against a standard which has a known response in aerosol-free air. The signal in the two color regions provides limited but useful particle-size information. Ozone measurements were made with a commercial sensor (ECC ozonesonde) modified to be part of the same instrument and telemetry package as the backscattersonde. Truly simultaneous measurements of both ozone and PSCs were obtained. In addition, simultaneous air temperature and pressure measurements were acquired with the backscattersonde. Balloon-borne frost-point measurements were made with an instrument described by Oltmans (1985). Previous measurements using this instrument in Antarctica have been reported by Rosen et al. (1991).
JAMES M. ROSEN AND NORMAN T. KJOME
Department of Physics and Astronomy University of Wyoming Laramie, Wyoming 82071 S.J. OLTAMANS
National Ocean and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory Boulder, Colorado 80303
The critical role that polar stratospheric clouds (PSCs) play in heterogeneous chemical ozone depletion schemes is well recognized. The South Pole is one of the most productive sites to study this interaction because temperatures low enough for extensive PSC formation occur every year. In addition, PSC activity continues through stratospheric sunrise over Antarctica; thus providing an unusual opportunity to directly observe possible correlation between ozone and PSCs during the initial stages of "ozone hole" formation. In this work, we conducted a series of simultaneous PSC and ozone observations from balloon-borne sensors launched at the South Pole starting before the beginning of PSC activity and continuing until the initial formation of the ozone hole. These observations were augmented with frost-point soundings and additional ozone soundings. PSC observations were made with a balloon-borne backscattersonde operating at wavelengths of 490 and 940 nanometers. This device, described by Rosen and Kjome (1991), is used for research in the north polar vortex as well as for monitor-
1992 REVIEW
References Jones, N. B. 1992. Application of improved HNO 3 band model parameters to South Pole atmospheric emission measurements. Ph.D. diss., University of Denver. Keys, J. G., P. V. Johnston, R. D. Blatherwick, and F.J. Murcray. 1992. New evidence of heterogeneous reactions involving nitrogen compounds in the antarctic stratosphere. Nature, in press. Murcray, F. J . and R. Heuberger. 1990. Infrared atmospheric absorption and emission measurements. Antarctic Journal of the U.S., 25(5):244-6. Murcray, F. J. and R. Heuberger. 1992. Year-round measurement of atmospheric infrared emission at the South Pole. Antarctic Journal of the U.S., 26(5)278-281.
TEMP./FROST PT. (°C) _q - -7c -()
30
IC R
25
2C
20 T
SC
15
R lOG E 20C (mb)
(km) 5
50C 000
U
o to 20 30 o iou euu BACKSCATTER RATIO OZONE PARTIAL (X : 94Onm) PRESSURE (nb)
An example of the vertical profiles obtained during this research project. See text for explanation and interpretation.
279
One of the goals of this work was to characterize the PSCs and their environment at the onset of formation. However, due to several launch mishaps, the initial period was missed. The last sounding before the occurrence of PSCs was on 17 May when the minimum stratospheric temperature was about -79 'C -1 'C warmer than the expected temperature of initial formation. The next successful sounding was made on 12 June after the minimum stratospheric temperatures dropped will below -80 'C and extensive PSC formation had already begun. The figure shows the results of a sounding made more than one month after the beginning of extensive PSC activity. The frost-point profile illustrated in this figure was obtained on 12 January 1991, and represents initial conditions in the vortex. According to the figure, by 16 July the stratospheric air temperature had cooled well below the initial frost-point and a large fraction of the water vapor would have already condensed. However, in the altitude range of 20 to 45 millibars the backscatter signal is relatively small and does not indicate the presence of significant condensed material. This suggests that the particles have already fallen out, resulting in dehydration of the stratosphere. The magnitude of the backscatter layer at 60 millibars can only be explained by condensed water vapor. The inverse correlation of this dense PSC layer with the structure in the ozone
suggests recent transport from outer regions of the vortex. It is too early in the season for the usual ozone hose to have started development. Because the dense PSC layer is recent, the particles would not have had time to fall out of the stratosphere, as did the particles that must have formed earlier in the 20 to 45 millibar range. Mike O'Neil and John Lowell were responsible for preparing instruments and launching the balloons. They were often required to work outside for extended periods at temperatures below -60'C, so their efforts are greatly appreciated. This work was supported by National Science Foundation grant DPP 88-16563. References
Oltmans, S. J. Measurements of water vapor in the stratosphere with a frost-point hygrometer. Proceedings of Moisture and Humidity, Washington, D.C. 15-18 April, 1985. 252-8. Rosen, J. M., N. T. Kjome, S. J. Oltmans. 1991. Balloon-borne observations of backscatter, frost point and ozone in polar stratospheric clouds at the South Pole. Geophysical Research Letters, 18:171-174. Rosen, J. M. and N. T. Kjome. 1991. Backscattersonde: a new instrument for atmospheric aerosol research. Applied Optics, 30:1,552-1,561.
Antarctic automatic weather stations: Austral summer 1991-1992 CHARLES R. STEARNS AND GEORGE
A. WEIDNER
Department of Atmospheric and Oceanic Sciences University of Wisconsin Madison, Wisconsin 53706
The United States Antarctic Program (USAP) of the National Science Foundation Office of Polar Programs (OPP) places automatic weather stations (AWS) units in remote areas of Antarctica in support of meteorological research and operations. The AWS data are collected by the ARGOS data collection system on board the National Oceanic and Atmospheric Administration (NOAA) series of polar orbiting satellites. In the AWS system the basic AWS units measure air temperature, wind speed, and wind direction at a nominal height of 3 meters above the surface and air pressure at the electronics enclosure. Some AWS units may measure relative humidity at 3 meters, air temperature difference between 3 meters and 0.5 meters above the surface. The AWS unit at Pegasus South (table 1) measures millivolt signals using a differential amplifier with a gain of 480 to amplify the thermocouple voltage to the 0 to 1 vdc range of the analog to digital converter and a differential multiplexer to select the channels. The system is used to measure the temperature profile in the ice to a depth of 1.60 meters. AWS units equipped with the vertical air temperature difference and relative humidity are used to estimate the sensible and latent heat fluxes. Some results of the estimates are presented by Steams (1992) and show that there is a net removal of water (ice) from the surface in Antarctica and the removal is largest during the sum-
280
Figure 1. Map of Antarctica showing the locations of the AWS units for 1992. The units in the rectangle about Manuela site are shown in figure 2. mer months, amounting to as much as 80 percent of the net annual accumulation at Lettau site on the Ross Ice Shelf. The table gives the unit's latitude, longitude, and the start date for USAPAWS units in 1992. The AWS units are grouped together based on the area and usually are related to a single meteorological experiment in the area. Stearns and Weidner (1991) describe the AWS activities during the previous austral summer. The AWS units are located in arrays for meteorological experiments and at other sites for operational purposes. Any one AWS
ANTARCTIC JOURNAL
Administration. The first project was also supported by the DSIR and the New Zealand Antarctic Program.
Simultaneous ozone and polar stratospheric cloud observations at Amundsen-Scott South Pole Station during winter and spring 1991
ing aerosols at mid-latitudes. Briefly, the instrument measures the amount of locally backscattered light at two wavelengths from a flash-lamp beam. The final data product is essentially the same as that of lidar systems, but with comparatively high resolution (about 30 meters). All instruments are calibrated before flight against a standard which has a known response in aerosol-free air. The signal in the two color regions provides limited but useful particle-size information. Ozone measurements were made with a commercial sensor (ECC ozonesonde) modified to be part of the same instrument and telemetry package as the backscattersonde. Truly simultaneous measurements of both ozone and PSCs were obtained. In addition, simultaneous air temperature and pressure measurements were acquired with the backscattersonde. Balloon-borne frost-point measurements were made with an instrument described by Oltmans (1985). Previous measurements using this instrument in Antarctica have been reported by Rosen et al. (1991).
JAMES M. ROSEN AND NORMAN T. KJOME
Department of Physics and Astronomy University of Wyoming Laramie, Wyoming 82071 S.J. OLTAMANS
National Ocean and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory Boulder, Colorado 80303
The critical role that polar stratospheric clouds (PSCs) play in heterogeneous chemical ozone depletion schemes is well recognized. The South Pole is one of the most productive sites to study this interaction because temperatures low enough for extensive PSC formation occur every year. In addition, PSC activity continues through stratospheric sunrise over Antarctica; thus providing an unusual opportunity to directly observe possible correlation between ozone and PSCs during the initial stages of "ozone hole" formation. In this work, we conducted a series of simultaneous PSC and ozone observations from balloon-borne sensors launched at the South Pole starting before the beginning of PSC activity and continuing until the initial formation of the ozone hole. These observations were augmented with frost-point soundings and additional ozone soundings. PSC observations were made with a balloon-borne backscattersonde operating at wavelengths of 490 and 940 nanometers. This device, described by Rosen and Kjome (1991), is used for research in the north polar vortex as well as for monitor-
1992 REVIEW
References Jones, N. B. 1992. Application of improved HNO 3 band model parameters to South Pole atmospheric emission measurements. Ph.D. diss., University of Denver. Keys, J. G., P. V. Johnston, R. D. Blatherwick, and F.J. Murcray. 1992. New evidence of heterogeneous reactions involving nitrogen compounds in the antarctic stratosphere. Nature, in press. Murcray, F. J . and R. Heuberger. 1990. Infrared atmospheric absorption and emission measurements. Antarctic Journal of the U.S., 25(5):244-6. Murcray, F. J. and R. Heuberger. 1992. Year-round measurement of atmospheric infrared emission at the South Pole. Antarctic Journal of the U.S., 26(5)278-281.
TEMP./FROST PT. (°C) _q - -7c -()
30
IC R
25
2C
20 T
SC
15
R lOG E 20C (mb)
(km) 5
50C 000
U
o to 20 30 o iou euu BACKSCATTER RATIO OZONE PARTIAL (X : 94Onm) PRESSURE (nb)
An example of the vertical profiles obtained during this research project. See text for explanation and interpretation.
279
One of the goals of this work was to characterize the PSCs and their environment at the onset of formation. However, due to several launch mishaps, the initial period was missed. The last sounding before the occurrence of PSCs was on 17 May when the minimum stratospheric temperature was about -79 'C -1 'C warmer than the expected temperature of initial formation. The next successful sounding was made on 12 June after the minimum stratospheric temperatures dropped will below -80 'C and extensive PSC formation had already begun. The figure shows the results of a sounding made more than one month after the beginning of extensive PSC activity. The frost-point profile illustrated in this figure was obtained on 12 January 1991, and represents initial conditions in the vortex. According to the figure, by 16 July the stratospheric air temperature had cooled well below the initial frost-point and a large fraction of the water vapor would have already condensed. However, in the altitude range of 20 to 45 millibars the backscatter signal is relatively small and does not indicate the presence of significant condensed material. This suggests that the particles have already fallen out, resulting in dehydration of the stratosphere. The magnitude of the backscatter layer at 60 millibars can only be explained by condensed water vapor. The inverse correlation of this dense PSC layer with the structure in the ozone
suggests recent transport from outer regions of the vortex. It is too early in the season for the usual ozone hose to have started development. Because the dense PSC layer is recent, the particles would not have had time to fall out of the stratosphere, as did the particles that must have formed earlier in the 20 to 45 millibar range. Mike O'Neil and John Lowell were responsible for preparing instruments and launching the balloons. They were often required to work outside for extended periods at temperatures below -60'C, so their efforts are greatly appreciated. This work was supported by National Science Foundation grant DPP 88-16563. References
Oltmans, S. J. Measurements of water vapor in the stratosphere with a frost-point hygrometer. Proceedings of Moisture and Humidity, Washington, D.C. 15-18 April, 1985. 252-8. Rosen, J. M., N. T. Kjome, S. J. Oltmans. 1991. Balloon-borne observations of backscatter, frost point and ozone in polar stratospheric clouds at the South Pole. Geophysical Research Letters, 18:171-174. Rosen, J. M. and N. T. Kjome. 1991. Backscattersonde: a new instrument for atmospheric aerosol research. Applied Optics, 30:1,552-1,561.
Antarctic automatic weather stations: Austral summer 1991-1992 CHARLES R. STEARNS AND GEORGE
A. WEIDNER
Department of Atmospheric and Oceanic Sciences University of Wisconsin Madison, Wisconsin 53706
The United States Antarctic Program (USAP) of the National Science Foundation Office of Polar Programs (OPP) places automatic weather stations (AWS) units in remote areas of Antarctica in support of meteorological research and operations. The AWS data are collected by the ARGOS data collection system on board the National Oceanic and Atmospheric Administration (NOAA) series of polar orbiting satellites. In the AWS system the basic AWS units measure air temperature, wind speed, and wind direction at a nominal height of 3 meters above the surface and air pressure at the electronics enclosure. Some AWS units may measure relative humidity at 3 meters, air temperature difference between 3 meters and 0.5 meters above the surface. The AWS unit at Pegasus South (table 1) measures millivolt signals using a differential amplifier with a gain of 480 to amplify the thermocouple voltage to the 0 to 1 vdc range of the analog to digital converter and a differential multiplexer to select the channels. The system is used to measure the temperature profile in the ice to a depth of 1.60 meters. AWS units equipped with the vertical air temperature difference and relative humidity are used to estimate the sensible and latent heat fluxes. Some results of the estimates are presented by Steams (1992) and show that there is a net removal of water (ice) from the surface in Antarctica and the removal is largest during the sum-
280
Figure 1. Map of Antarctica showing the locations of the AWS units for 1992. The units in the rectangle about Manuela site are shown in figure 2. mer months, amounting to as much as 80 percent of the net annual accumulation at Lettau site on the Ross Ice Shelf. The table gives the unit's latitude, longitude, and the start date for USAPAWS units in 1992. The AWS units are grouped together based on the area and usually are related to a single meteorological experiment in the area. Stearns and Weidner (1991) describe the AWS activities during the previous austral summer. The AWS units are located in arrays for meteorological experiments and at other sites for operational purposes. Any one AWS
ANTARCTIC JOURNAL
