The 1995–96 northern hemisphere (NH) winter stratosphere was colder than in any of the previous 17 winters, with lower stratospheric temperatures continuously below the type 1 (primarily HNO 3 ) polar stratospheric cloud (PSC) threshold for over 2 1/2 months. Upper tropospheric ridges in late Feb and early Mar 1996 led to the lowest observed NH lower stratospheric temperatures, and the latest observed NH temperatures below the type 2 (water ice) PSC threshold. Consistent with the unusual cold and chemical processing on PSCs, UARS MLS observed a greater decrease in lower stratospheric ozone (O 3 ) in 1995–96 than in any of the previous 4 NH winters. O 3 decreased throughout the vortex over an altitude range nearly as large as that typical of the southern hemisphere (SH). The decrease between late Dec 1995 and early Mar 1996 was ∼2/3 of that over the equivalent SH period. As in other NH winters, temperatures in 1996 rose above the PSC threshold before the spring equinox, ending chemical processing in the NH vortex much earlier than is usual in the SH. A downward trend in column O 3 above 100 hPa during Jan and Feb 1996 appears to be related to the lower stratospheric O 3 depletion.
view Abstract Citations (78) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of interstellar H2O emission at 183 gigahertz Waters, J. W. ; Kakar, R. K. ; Kuiper, T. B. H. ; Roscoe, H. K. ; Swanson, P. N. ; Rodriguez Kuiper, E. N. ; Kerr, A. R. ; Thaddeus, P. ; Gustincic, J. J. Abstract Observations of the 183-GHz rotational transition of water vapor in interstellar molecular clouds are reported. The observations were made with a portable double-sideband superheterodyne radiometer used with the 91-cm Cassegrain telescope on board the Kuiper Airborne Observatory. An emission feature was detected in the direction of the Kleinmann-Low nebula in Orion with a peak antenna temperature of 15 K, a local standard of rest velocity of 8 km/sec, and a width of 15 km/sec. A plateau component of the emission profile is attributed to the 1-arcmin region characteristic of plateau emission from other observed molecules, with emission enhanced over that expected for thermal excitation, while the spike component observed is consistent with an optically thick source of the size of the molecular ridge in Orion at a temperature of 50 K and a column density greater than or equal to 3 x 10 to the 17th/sq cm, implying that H2O is one of the more abundant species in the Orion Molecular Cloud. Emission at 183 GHz was not detected in Sgr A, Sgr B2, W3, W43, W49, W51, DR 21, NGC 1333, NGC 7027, GL 2591 or the Rho Oph cloud; it may have been detected in M 17. Publication: The Astrophysical Journal Pub Date: January 1980 DOI: 10.1086/157609 Bibcode: 1980ApJ...235...57W Keywords: Infrared Astronomy; Interstellar Space; Microwave Emission; Nebulae; Radio Sources (Astronomy); Water Masers; Airborne Equipment; Brightness Temperature; Line Spectra; Molecules; Spectroscopic Telescopes; Astrophysics full text sources ADS |
Stratospheric ClO and O 3 vertical profiles were measured at 32° N in May 1985 and October 1986. The ClO profiles and diurnal variation are in general agreement with theory, but have somewhat less midday ClO near 34 km. Measured 35‐45 km O 3 is larger than theory and no stratospheric O 3 diurnal variation was observed, as expected. HNO 3 was detected, and an H 2 O 2 upper limit obtained.
UARS MLS observations of stratospheric ozone and chlorine monoxide are described. Enhanced concentrations of ClO, the predominant form of reactive chlorine responsible for ozone depletion, are seen within both the northern and southern winter polar vortices. In the southern hemisphere, this leads directly to the development of the annual Antarctic ozone hole. While ozone depletion is also observed in the north, it is less severe and there is considerable interannual variability.< >
We present an analysis of the temporal evolution of stratospheric constituents above the station of Dumont d'Urville in Antarctica (67°S, 140°E) from August 14 to September 20, 1992. Data sets include temperature profiles and H 2 O, ClO, O 3 , NO 2 , ClONO 2 , HNO 3 , N 2 O, and CH 4 mixing ratios and aerosol extinction coefficients from 46 to 1 hPa measured by the Microwave Limb Sounder (MLS) and the Cryogenic Limb Array Etalon Spectrometer (CLAES) instruments aboard the Upper Atmosphere Research Satellite (UARS). At the station, aerosol extinction coefficients and O 3 profiles are obtained by a lidar together with O 3 profiles provided by sondes. Integrated O 3 and NO 2 column amounts are given by a Système d'Analyse par Observation Zénithale (SAOZ) spectrometer located at the station. Column O 3 is also provided by the Total Ozone Mapping Spectrometer (TOMS) instrument aboard the NIMBUS 7 satellite, complemented with potential vorticity derived from the U.K. Meteorological Office assimilated data set and temperature fields provided by the European Centre for Medium‐Range Weather Forecasts. Time evolution of these measurements is interpreted by comparison with results from the SLIMCAT three‐dimensional chemical transport model. We show that the site is near the vortex edge on average and is alternately inside the vortex or just outside in the region referred to as the “collar” region. There are no observations of polar stratospheric clouds (PSCs) over the station above 46 hPa (∼18 km). In fact, PSCs mainly appear over the Palmer Peninsula area at 46 hPa. The rates of change of chemical species are evaluated at 46 hPa when the station is conservatively inside the vortex collar region. The ozone loss rate is 0.04 ppmv d −1 (∼1.3% d −1 ), which is consistent with other analyses of southern vortex ozone loss rates; chlorine monoxide tends to decrease by 0.03 ppbv d −1 , while chlorine nitrate increases by 0.025 ppbv d −1 . These negative ClO and positive ClONO 2 trends are only observed in the collar region of the vortex where O 3 amounts are far from near zero, and little denitrification is observed. Loss and production rates as measured by UARS are more pronounced than the ones deduced from the SLIMCAT model, probably because of the moderate model horizontal resolution (3.75° × 3.75°), which is not high enough to resolve the vortex crossings above Dumont d'Urville and which leads to a larger extent of denitrified air than indicated by the UARS data. The analysis also shows activated ClO inside the vortex at 46 hPa, a dehydrated vortex at 46 hPa, and rehydrated above, with no trace of denitrification in the lower stratosphere. Good agreement between coincident measurements of O 3 profiles by UARS/MLS, lidar, and sondes is also observed. Finally, the agreement between UARS and SLIMCAT data sets is much better in the middle stratosphere (4.6 hPa) than in the lower stratosphere (46 hPa).
This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz.
