The Experts below are selected from a list of 48543 Experts worldwide ranked by ideXlab platform

Sasha Madronich - One of the best experts on this subject based on the ideXlab platform.

C G Wellemeyer - One of the best experts on this subject based on the ideXlab platform.

  • application of the langley plot method to the calibration of the solar backscattered ultraviolet instrument on the nimbus 7 satellite
    Journal of Geophysical Research, 1995
    Co-Authors: P K Bhartia, S L Taylor, C G Wellemeyer
    Abstract:

    The concept of the well-known Langley plot technique, used for the calibration of ground-based instruments, has been generalized for application to satellite instruments. In polar regions, near summer solstice, the solar backscattered ultraviolet (SBUV) instrument on the Nimbus 7 satellite samples the same Ozone field at widely different solar zenith angles. These measurements are compared to assess the long-term drift in the instrument calibration. Although the technique provides only a relative wavelength-to-wavelength calibration, it can be combined with existing techniques to determine the drift of the instrument at any wavelength. Using this technique, we have generated a 12-year data set of Ozone vertical profiles from SBUV with an estimated accuracy of ±5% at 1 mbar and ±2% at 10 mbar (95% confidence) over 12 years. Since the method is insensitive to true changes in the Atmospheric Ozone profile, it can also be used to compare the calibrations of similar SBUV instruments launched without temporal overlap.

Niklaus Kampfer - One of the best experts on this subject based on the ideXlab platform.

  • Short-term stratospheric Ozone fluctuations observed by GROMOS microwave radiometer at Bern
    'Springer Science and Business Media LLC', 2018
    Co-Authors: Lorena Moreira, Klemens Hocke, Niklaus Kampfer
    Abstract:

    Abstract The ground-based millimeter wave Ozone spectrometer (GROMOS) has been continually measuring middle Atmospheric Ozone volume mixing ratio profiles above Bern, Switzerland ( $$46.95^{\circ }\hbox {N}$$ 46 . 95 ∘ N , $$7.44^{\circ }\hbox {E}$$ 7 . 44 ∘ E , 577 m), since 1994 in the frame of NDACC. The high temporal resolution of GROMOS (30 min) allows the analysis of short-term fluctuations. The present study analyses the temporal perturbations, ranging from 1 to 8 h, observed in stratospheric Ozone from June 2011 to May 2012. The short-term fluctuations of stratospheric Ozone are within 5%, and GROMOS appears to have relative amplitudes stable over time smaller than 2% at 10 hPa (32 km). The strongest natural fluctuations of stratospheric Ozone (about 1% at 10 hPa) above Bern occur during winter due to displacements and deformations of the polar vortex towards mid-latitudes

  • the importance of signals in the doppler broadening range for middle Atmospheric microwave wind and Ozone radiometry
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2017
    Co-Authors: Rolf Rufenacht, Niklaus Kampfer
    Abstract:

    Abstract Doppler microwave radiometry is a novel technique for the measurement of horizontal wind profiles at altitudes between 10 and 0.03 hPa, where there is a substantial lack of observations. All wind radiometers currently in use rely on ground-based observations of microwave radiation emitted by Atmospheric Ozone. Besides the well-known primary Ozone layer in the stratosphere a secondary Ozone layer forms near 10 − 3  hPa during nighttime. We show that the emission signal of this secondary Ozone layer cannot be neglected for the retrieval of mesospheric winds and that it can even alter nighttime Ozone retrievals. However, the present study also demonstrates that with a reasonably adequate representation of the Atmospheric reality in the mesopause region bias-free wind retrievals throughout the entire sensitive altitude range of the instruments can be achieved during day and nighttime. By applying the improved Ozone a priori setup to real observation data the average zonal wind difference to models was substantially reduced and a realistic diurnal cycle was reproduced. Moreover the presence of the high nighttime mesopause Ozone signal could enable future retrievals of mean winds beyond the altitude range dominated by pressure broadening.

Luke Abraham - One of the best experts on this subject based on the ideXlab platform.

  • Ozone chemistry on tidally locked M dwarf planets
    Monthly Notices of the Royal Astronomical Society, 2020
    Co-Authors: Jack S. Yates, Paul I. Palmer, James Manners, Ian A. Boutle, Krisztian Kohary, Nathan J. Mayne, Luke Abraham
    Abstract:

    We use the Met Office Unified Model to explore the potential of a tidally locked M dwarf planet, nominally Proxima Centauri b irradiated by a quiescent version of its host star, to sustain an Atmospheric Ozone layer. We assume a slab ocean surface layer, and an Earth-like atmosphere of nitrogen and oxygen with trace amounts of Ozone and water vapour. We describe Ozone chemistry using the Chapman mechanism and the hydrogen oxide (HO$_x$, describing the sum of OH and HO$_2$) catalytic cycle. We find that Proxima Centauri radiates with sufficient UV energy to initialize the Chapman mechanism. The result is a thin but stable Ozone layer that peaks at 0.75 parts per million at 25 km. The quasi-stationary distribution of Atmospheric Ozone is determined by photolysis driven by incoming stellar radiation and by Atmospheric transport. Ozone mole fractions are smallest in the lowest 15 km of the atmosphere at the sub-stellar point and largest in the nightside gyres. Above 15 km the Ozone distribution is dominated by an equatorial jet stream that circumnavigates the planet. The nightside Ozone distribution is dominated by two cyclonic Rossby gyres that result in localized Ozone hotspots. On the dayside the Atmospheric lifetime is determined by the HO$_x$ catalytic cycle and deposition to the surface, with nightside lifetimes due to chemistry much longer than timescales associated with Atmospheric transport. Surface UV values peak at the substellar point with values of 0.01 W/m$^2$, shielded by the overlying Atmospheric Ozone layer but more importantly by water vapour clouds.

J Staehelin - One of the best experts on this subject based on the ideXlab platform.

  • absorption cross sections of Ozone in the ultraviolet and visible spectral regions status report 2015
    Journal of Molecular Spectroscopy, 2016
    Co-Authors: J Orphal, A F Bais, J Staehelin, J Tamminen, G O Braathen, Marierenee De Backer, Dimitris Balis, A Barbe, P K Bhartia, Manfred Birk
    Abstract:

    The activity “Absorption Cross-Sections of Ozone” (ACSO) started in 2008 as a joint initiative of the International Ozone Commission (IO3C), the World Meteorological Organization (WMO) and the IGACO (“Integrated Global Atmospheric Chemistry Observations”) O3/UV subgroup to study, evaluate, and recommend the most suitable Ozone absorption cross-section laboratory data to be used in Atmospheric Ozone measurements. The evaluation was basically restricted to Ozone absorption cross-sections in the UV range with particular focus on the Huggins band. Up until now, the data of Bass and Paur published in 1985 (BP, 1985) are still officially recommended for such measurements. During the last decade it became obvious that BP (1985) cross-section data have deficits for use in advanced space-borne Ozone measurements. At the same time, it was recognized that the origin of systematic differences in ground-based measurements of Ozone required further investigation, in particular whether the BP (1985) cross-section data might contribute to these differences. In ACSO, different sets of laboratory Ozone absorption cross-section data (including their dependence on temperature) of the group of Reims (France) and , 1992, 1995, abbreviated as BDM, 1995) and those of [8], and [7], (abbreviated as SER, 2014) were examined for use in Atmospheric Ozone measurements in the Huggins band. In conclusion, ACSO recommends: - The spectroscopic data of BP (1985) should no longer be used for retrieval of Atmospheric Ozone measurements. - For retrieval of ground-based instruments of total Ozone and Ozone profile measurements by the Umkehr method performed by Brewer and Dobson instruments data of SER (2014) are recommended to be used. When SER (2014) is used, the difference between total Ozone measurements of Brewer and Dobson instruments are very small and the difference between Dobson measurements at AD and CD wavelength pairs are diminished. - For ground-based Light Detection and Ranging (LIDAR) measurements the use of BDM (1995) or SER (2014) is recommended. - For satellite retrieval the presently widely used data of BDM (1995) should be used because SER (2014) seems less suitable for retrievals that use wavelengths close to 300 nm due to a deficiency in the signal-to-noise ratio in the SER (2014) dataset.

  • total Atmospheric Ozone determined from spectral measurements of direct solar uv irradiance
    Geophysical Research Letters, 1995
    Co-Authors: Martin Huber, M Blumthaler, W Ambach, J Staehelin
    Abstract:

    With a double monochromator, high resolution spectral measurements of direct solar UV-irradiance were performed in Arosa during February and March, 1993. Total Atmospheric Ozone amount is determined by fitting model calculations to the measured spectra. The results are compared with the operationally performed measurements of a Dobson and a Brewer spectrometer. The total Ozone amount determined from spectral measurements differs from the results of the Dobson instrument by −1.1±0.9% and from those of the Brewer instrument by −0.4±0.7%.