Professor Roy Grainger

Abstract:

[1] The six longest records of stratospheric aerosol ( in situ measurements at Laramie, Wyoming, lidar records at: Garmisch-Partenkirchen, Germany; Hampton, Virginia; Mauna Loa, Hawaii; Sao Jose dos Campos, Brazil, and SAGE II measurements) were investigated for trend by ( 1) comparing measurements in the 3 volcanically quiescent periods since 1970 using standard analysis of variance techniques, and ( 2) analyzing residuals from a time/volcano dependent empirical model applied to entire data sets. A standard squared-error residual minimization technique was used to estimate optimum parameters for each measurement set, allowing for first order autocorrelation, which increases standard errors of trends but does not change magnitude. Analysis of variance over the 3 volcanically quiescent periods is controlled by the end points (pre-El Chichon and post-Pinatubo), and indicates either no change (Garmisch, Hampton, Sao Jose dos Campos, Laramie-0.15 mu m) or a slight, statistically insignificant, decrease ( Mauna Loa, Laramie-0.25 mu m), - 1 +/- 0.5% yr(-1). The empirical model was applied to the same records plus 1020 nm SAGE II data separated into 33 latitude/altitude bins. No trend in stratospheric aerosol was apparent for 31 of 33 SAGE II data sets, 3 of 4 lidar records, and in situ measurements at 0.15 mu m. For Hampton and Laramie-0.25 mu m, the results suggest a weak negative trend, - 2 +/- 0.5% yr(-1), while 2 SAGE II data sets ( 30 - 35 km, 30 degrees and 40 degrees N) suggest a positive trend of similar magnitude. Overall we conclude that no long-term change in background stratospheric aerosol has occurred over the period 1970 - 2004.

Abstract:

The Michelson Interferometer for Passive Atmospheric Sounding is a polar orbiting high resolution mid-infrared emission limb sounder with a nominal vertical resolution of 3 km. Work to extend the list of routinely retrieved species led to the examination of ammonia, NH3. In this paper, we explore the feasibility of upper tropospheric retrievals around 6-km altitude, discussing appropriate methods. We demonstrate a weak north to south gradient outside the error bars, using co-addition to improve signal-to-noise and compare these first results with a model. (c) 2006 Published by Elsevier Ltd on behalf of COSPAR.

Abstract:

Information on cloud properties from ATSR-2 radiances originates from the interaction of solar and terrestrial radiation with the cloud. Due to the spectral dependence of cloud optical properties, observations in different channels of ATSR-2 can be combined to provide information on a cloud phase, top height, effective radius cloud fraction and optical depth. These parameters are retrieved using an optimal estimation approach which enables us to extract information from all channels simultaneously. The method allows us to characterize the error on each parameter assuming the observed cloud is consistent with the modelled cloud (i.e. reasonably plane-parallel in nature). It is also possible to identify when model assumptions are inappropriate by examining the fit between simulated and observed radiances. This technique has been used in the NERC GRAPE (Global Retrieval of Clouds and Evaluation) project. In this paper the optimal estimation algorithm will be outlined and products and validation from the 5 year data set will be presented.

Abstract:

Operationally only pressure, temperature and six significant trace gases are retrieved by ESA from MIPAS data. However, information on many other species is also present in the spectra. We apply a variety of techniques and our own retrieval model to retrieve the concentration of three other species: SO 2,OCS and SF6. Sulphur Dioxide (SO2) is an acidic gas with both natural and anthropogenic sources that is rapidly converted to sulphuric acid and hence sulphate aerosols in the atmosphere. Carbonyl Sulphide (OCS) is produced naturally at the ocean surface and by biomass burning and, through stratospheric oxidation, it is thought to be the main contributor to non-volcanic stratospheric sulphate aerosols. Sulphur Hexafluoride (SF 6) is almost entirely anthropogenic in its origins and shows steady year-on-year increases making it useful for age of air and tracer studies. We anticipate the good global coverage and continuity of data will make MIPAS useful for the determination of changes and trends in the quantity and distribution of these species both natural and anthropogenic. In this paper we summarise the current progress that has been made in the retrieval of these important sulphur-containing species. We show some preliminary zonal mean fields and briefly outline the methods applied.