Engineering topics

Kerr, J. B.

Publications and source records attributed to Kerr, J. B..

13 records

NASA NTRS1998

Trends in the Vertical Distribution of Ozone: A Comparison of Two Analyses of Ozonesonde Data

We present the results of two independent analyses of ozonesonde measurements of the vertical profile of ozone. For most of the ozonesonde stations we use data that were recently reprocessed and reevaluated to improve their quality and internal consistency. The two analyses give similar results for trends in ozone. We attribute differences in results primarily to differences in data selection criteria and in utilization of data correction factors, rather than in statistical trend models. We find significant decreases in stratospheric ozone at all stations in middle and high latitudes of the northern hemisphere from 1970 to 1996, with the largest decreases located between 12 and 21 km, and trends of -3 to -10 %/decade near 17 km. The decreases are largest at the Canadian and the most northerly Japanese station, and are smallest at the European stations, and at Wallops Island, U.S.A. The mean mid-latitude trend is largest, -7 %/decade, from 12 to 17.5 km for 1970-96. For 1980-96, the decrease is more negative by 1-2 %/decade, with a maximum trend of -9 %/decade in the lowermost stratosphere. The trends vary seasonally from about 12 to 17.5 km, with largest ozone decreases in winter and spring. Trends in tropospheric ozone are highly variable and depend on region. There are decreases or zero trends at the Canadian stations for 1970-96, and decreases of -2 to -8 %/decade for the mid-troposphere for 1980-96; the three European stations show increases for 1970-96, but trends are close to zero for two stations for 1980-96 and positive for one; there are increases in ozone for the three Japanese stations for 1970-96, but trends are either positive or zero for 1980-96; the U.S. stations show zero or slightly negative trends in tropospheric ozone after 1980. It is not possible to define reliably a mean tropospheric ozone trend for northern mid-latitudes, given the small number of stations and the large variability in trends. The integrated column trends derived from the sonde data are consistent with trends derived from both surface based and satellite measurements of the ozone column.

Loogan, J. A.↗

NASA NTRS1995

Stratospheric Ozone Intercomparison Campaign (STOIC) 1989: Overview

The NASA Upper Atmosphere Research Program organized a Stratospheric Ozone Intercomparison Campaign (STOIC) held in July-August 1989 at the Table Mountain Facility (TMF) of the Jet Propulsion Laboratory (JPL). The primary instruments participating in this campaign were several that had been developed by NASA for the Network for the Detection of Stratospheric Change: the JPL ozone lidar at TMF, the Goddard Space Flight Center trailer-mounted ozone lidar which was moved to TMF for this comparison, and the Millitech/LaRC microwave radiometer. To assess the performance of these new instruments, a validation/intercomparison campaign was undertaken using established techniques: balloon ozonesondes launched by personnel from the Wallops Flight Facility and from NOAA Geophysical Monitoring for Climate Change (GMCC) (now Climate Monitoring and Diagnostics Laboratory), a NOAA GMCC Dobson spectrophotometer, and a Brewer spectrometer from the Atmospheric Environment Service of Canada, both being used for column as well as Umkehr profile retrievals. All of these instruments were located at TMF and measurements were made as close together in time as possible to minimize atmospheric variability as a factor in the comparisons. Daytime rocket measurements of ozone were made by Wallops Flight Facility personnel using ROCOZ-A instruments launched from San Nicholas Island. The entire campaign was conducted as a blind intercomparison, with the investigators not seeing each others data until all data had been submitted to a referee and archived at the end of the 2-week period (July 20 to August 2, 1989). Satellite data were also obtained from the Stratospheric Aerosol and Gas Experiment (SAGE 2) aboard the Earth Radiation Budget Satellite and the Total Ozone Mapping Spectrometer (TOMS) aboard Nimbus 7. An examination of the data has found excellent agreement among the techniques, especially in the 20- to 40-km range. As expected, there was little atmospheric variability during the intercomparison, allowing for detailed statistical comparisons at a high level of precision. This overview paper summarizes the campaign and provides a 'road map' to subsequent papers in this issue by the individual instrument teams which will present more detailed analysis of the data and conclusions.

Margitan, J. J.↗

NASA NTRS1995

Satellite estimation of spectral UVB irradiance using TOMS derived total ozone and UV reflectivity

A method for satellite remote sensing of spectral UVB radiation incident at the earth's surface for snow and/or ice free areas has been developed. Measurements of total ozone and UV reflectively from the Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) instrument have been applied to this technique. Comparison of satellite estimates with ground based measurements of spectral UVB irradiance show differences which are comparable to differences between near simultaneous measurements made with two or more ground based co-located instruments.

Eck, T. F.↗

NASA NTRS1994

Ozone trends estimated from Umkehr observations made at Edmonton, Alberta, Canada

A Brewer Ozone Spectrophotometer has been in service at the Canadian ozone monitoring station at Stony Plain (53.55 deg N, 114.10 deg W), near Edmonton, Alberta, since 1984. During that time, the instrument has been operated in a fully automated mode that includes the collection of morning and evening Umkehr observations. Some 197 Umkehr observations have been analyzed to make an estimate of the temporal trend in ozone amount at high altitude over the station during the last 8 years. This work has shown that at 40 km the trend in the ozone concentration has been observed to be 0.14 plus or minus 0.10 percent per year.

Mcelroy, C. T.↗

NASA NTRS1994

Visible light nitrogen dioxide spectrophotometer intercomparison: Mount Kobau, British Columbia, July 28 to August 10, 1991

Under the auspices of the World Meteorological Organization, Environment Canada hosted an international comparison of visible light spectrophotometers at Mt. Kobau, British Columbia in August of 1991. Instruments from four countries were involved. The intercomparison results have indicated that some significant differences exist in the responses of the various instruments, and have provided a basis for the comparison of the historical data sets which currently exist as a result of the independent researches carried out in the past in the former Soviet Union, New Zealand, and Canada.

Mcelroy, C. T.↗

NASA NTRS1994

The Canadian Ozone Watch and UV-B advisory programs

The Ozone Watch, initiated in March, 1992, is a weekly bulletin describing the state of the ozone layer over Canada. The UV-B advisory program, which started in May, 1992, produces daily forecasts of clear-sky UV-B radiation. The forecast procedures use daily ozone measurements from the eight-station monitoring network, the output from the Canadian operational forecast model and a UV-B algorithm based on three years of spectral UV-B measurements with the Brewer spectrophotometer.

Kerr, J. B.↗

NASA NTRS1994

The latitudinal distribution of ozone to 35 km altitude from ECC ozonesonde observations, 1982-1990

Electrochemical concentration cell (ECC) ozone-sonde observations, made in recent years at ten stations whose locations range from the Arctic to Antarctica, have yielded a self-consistent ozone data base from which mean seasonal and annual latitudinal ozone vertical distributions to 35 km have been derived. Ozone measurement uncertainties are estimated, and results are presented in the Bass-Paur (1985) ozone absorption coefficient scale adopted for use with Dobson ozone spectrophotometers January 1, 1992. The data should be useful for comparison with model calculations of the global distribution of atmospheric ozone, for serving as apriori statistical information in deriving ozone vertical distributions from satellite and Umkehr observations, and for improving the satellite and Umkehr ozone inversion algorithms. Attention is drawn to similar results based on a less comprehensive data set published in Ozone in the Atmosphere, Proceedings of the 1988 Quadrennial Ozone Symposium where errors in data tabulations occurred for three of the stations due to inadvertent transposition of ozone partial pressure and air temperature values.

Komhyr, W. D.↗

NASA NTRS1994

SPEAM-II experiment for the measurement of stratospheric NO2, O3 and aerosols

Following the success of the Sunphotometer Earth Atmosphere Measurement (SPEAM-I) experiment, a more involved experiment was developed to fly as part of the second set of Canadian Experiments (CANEX-2) which will fly on the US Space Shuttle in the fall of 1992. The instrument complement includes an IBM-PC compatible control computer, a hand-held diode array spectrophotometer, and an interference-filter, limb imaging radiometer for the measurement of the atmospheric airglow. The hand-held spectrometer will measure nitrogen dioxide, ozone and aerosols. The limb imaging radiometer will observe emissions from the O2(1 DELTA) and O2(1 SIGMA) airglow bands. Only the spectrophotometer will be discussed here.

Mcelroy, C. T.↗

NASA NTRS1994

Stratospheric Ozone Intercomparison Campaign (STOIC) 1989: Overview

ozone↗

NASA NTRS1988

CANOZE measurements of the Arctic ozone hole

In CANOZE 1 (Canadian Ozone Experiment), a series of 20 ozone profile measurements were made in April, 1986 from Alert at 82.5 N. CANOZE is the Canadian program for study of the Arctic winter ozone layer. In CANOZE 2, ozone profile measurements were made at Saskatoon, Edmonton, Churchill and Resolute during February and March, 1987 with ECC ozonesondes. Ground based measurements of column ozone, nitrogen dioxide and hydrochloric acid were conducted at Saskatoon. Two STRATOPROBE balloon flights were conducted on February 26 and March 19, 1987. Two aerosol flights were conducted by the University of Wyoming. The overall results of this study will be reported and compared with the NOZE findings. The results from CANOZE 3 in 1988, are also discussed. In 1988, as part of CANOZE 3, STRATOPROBE balloon flights were conducted from Saskatchewan on January 27 and February 13. A new lightweight infrared instrument was developed and test flown. A science flight was successfully conducted from Alert (82.5 N) on March 9, 1988 when the vortex was close to Alert; a good measurement of the profile of nitric acid was obtained. Overall, the Arctic spring ozone layer exhibits many of the features of the Antarctic ozone phenomenon, although there is obviously not a hole present every year. The Arctic ozone field in March, 1986 demonstrated many similarities to the Antarctic ozone hole. The TOMS imagery showed a crater structure in the ozone field similar to the Antarctic crater in October. Depleted layers of ozone were found in the profiles around 15 km, very similar to those reported from McMurdo. Enhanced levels of nitric acid were measured in air which had earlier been in the vortex. The TOMS imagery for March 1987 did not show an ozone crater, but will be examined for an ozone crater in February and March, 1988, the target date for the CANOZE 3 project.

Evans, W. F. J.↗

NASA NTRS1988

Brewer spectrophotometer measurements in the Canadian Arctic

In the winters of 1987 and 1988 measurements were conducted with the Brewer Spectrophotometer at Alert (82.5 N) and Resolute (74.5 N). The measurements were conducted as part of our Canadian Program to search for an Arctic Ozone Hole (CANOZE). Ozone measurements were conducted in the months of December, January and February using the moon as a light source. The total ozone measurements will be compared with ozonesonde profiles, from ECC sondes, flown once per week from Alert and Resolute. A modified Brewer Spectrophotometer was used in a special study to search for chlorine dioxide at Alert in March 1987. Ground based observations at Saskatoon in February and at Alert in March 1987 failed to detect any measureable chlorine dioxide. Interference from another absorbing gas, which we speculate may be nitrous acid, prevented the measurements at the low levels of chlorine dioxide detected in the Southern Hemisphere by Solomon et al.

Kerr, J. B.↗

NASA NTRS1982

Measurements of SO2 in the Mount St. Helens debris

Routine measurements of ozone and SO2 are made with the Dobson and Brewer spectrophotometers at the Atmospheric Environment Service in Downsview Ontario. On May 20 and 21, 1980, large values of column SO2 were observed with both spectrophotometers at the time of passage of the Mount St. Helens debris. Enhanced SO2 values were first observed at 1800Z on May 20. The maximum column amount of SO2 measured was 0.06 cm at 2200 Z. On May 21, SO2 values slowly decreased from 0.03 cm at 1100 Z cm to 0.01 cm at 2000Z. Typical SO2 amounts due to pollution at the Downsview site are approximately 0.003 to 0.005 cm. At the same time of maximum SO2 enhancement, both Dobson and Brewer spectrophotometers measured a 0.040 cm decrease of total ozone. It is not clear whether the decrease of total ozone was caused by the volcanic cloud or natural ozone variability. Air mass trajectories indicate that the altitude of the debris cloud, which passed over Downsview at the time, was between 10 km and 12 km.

Kerr, J. B.↗

NASA NTRS1981

Preliminary results of an intercomparison of total ozone spectrophotometers

Preliminary results from an intercomparison of five total ozone spectrophotometers are presented. These are the Dobson spectrophotometer, the USSR M-83 ozonometer, the Canterbury filter photometer, the SenTran Company filter photometer, and the Brewer grating spectrophotometer. The pertinent characteristics of each are described, and conclusions are drawn about the agreement of each instrument's measurements with the Dobson's values over a time period of nearly one year. A discussion of the importance of calibration and long-term stability and reliability is included.

Parsons, C. L.↗