Earth Observation Data Group

Abstract:

The cryogenic limb array etalon spectrometer (CLAES) and the improved stratospheric and mesospheric sounder (ISAMS) instruments on board the Upper Atmosphere Research Satellite (UARS) have been used to produce global information on the Mt. Pinatubo volcanic aerosol for the period from October 1991 to April 1993, The Satellite infrared extinction measurements near 12 mu m are converted into the aerosol-related parameters necessary for modelling the effects of the volcanic aerosol on the aeronomy of the stratosphere and are presented as zonal mean distributions for 80 degrees S to 80 degrees N averaged over similar to 35-day periods. The aerosol composition is derived from the CLAES and ISAMS temperature measurements and the water vapour abundances are obtained from the microwave limb sounder (MLS). The aerosol volume density is obtained from the extinction measurements from which the Surface area density and the effective particle radius are estimated. The maximum aerosol surface area density has a value of about 50 mu m(2) cm(-3) at a height of 24 km at the equator in October 1991, before decaying exponentially with a time constant of 443 +/- 10 days. The surface area density remained well above preeruption values in April 1993. The effective particle radius in the tropics decays monotonically from 0.65 mu m in October 1991 to 0.4 mu m in April 1993. The global aerosol sulphate mass loading is 19.5 Mt in October 1991 and decays exponentially with a time constant of 342 +/- 8 days to a value of 4.3 Mt by April 1993. Four months after the eruption the calculated optical thickness at 1.02 mu m was similar to 0.25 in the tropics. Rate constants are derived for the heterogeneous reactions of N2O5 and ClONO2 on the sulphate aerosols. The application of the aerosol parameters to the investigation of tracer transport, heterogeneous chemistry, and radiative transfer is discussed.

Abstract:

Simultaneous observations of Polar Stratospheric Cloud (PSC) aerosol extinction and HNO3 mixing ratios over Scandinavia are examined for January 9-10, 1992. Data measured by the Microwave Limb Sounder (MLS), Cryogenic Limb Array Etalon Spectrometer (CLAES), and Improved Stratospheric and Mesospheric Sounder (ISAMS) experiments on the Upper Atmosphere Research Satellite (UARS) are examined at locations adjacent to parcel trajectory positions. Regression coefficients, obtained from Mie calculations, are used to transform aerosol extinctions into aerosol volume densities. Graphs of volume density versus temperature, and importantly, HNO3 mixing ratio versus temperature, show volume increases and simultaneous loss of HNO3 as temperatures decrease. The data is consistent with initial PSC growth processes which transform sulfate droplets into ternary droplets or nitric acid dihydrate (NAD) particles.

Abstract:

The cryogenic limb array etalon spectrometer (CLAES) and the improved stratospheric and mesospheric sounder (ISAMS) instruments on board the Upper Atmosphere Research Satellite (UARS) have been used to produce global information on the Mt. Pinatubo volcanic aerosol for the period from October 1991 to April 1993, The Satellite infrared extinction measurements near 12 mu m are converted into the aerosol-related parameters necessary for modelling the effects of the volcanic aerosol on the aeronomy of the stratosphere and are presented as zonal mean distributions for 80 degrees S to 80 degrees N averaged over similar to 35-day periods. The aerosol composition is derived from the CLAES and ISAMS temperature measurements and the water vapour abundances are obtained from the microwave limb sounder (MLS). The aerosol volume density is obtained from the extinction measurements from which the Surface area density and the effective particle radius are estimated. The maximum aerosol surface area density has a value of about 50 mu m(2) cm(-3) at a height of 24 km at the equator in October 1991, before decaying exponentially with a time constant of 443 +/- 10 days. The surface area density remained well above preeruption values in April 1993. The effective particle radius in the tropics decays monotonically from 0.65 mu m in October 1991 to 0.4 mu m in April 1993. The global aerosol sulphate mass loading is 19.5 Mt in October 1991 and decays exponentially with a time constant of 342 +/- 8 days to a value of 4.3 Mt by April 1993. Four months after the eruption the calculated optical thickness at 1.02 mu m was similar to 0.25 in the tropics. Rate constants are derived for the heterogeneous reactions of N2O5 and ClONO2 on the sulphate aerosols. The application of the aerosol parameters to the investigation of tracer transport, heterogeneous chemistry, and radiative transfer is discussed.

Abstract:

This paper introduces a series of papers describing the validation of data products from the improved stratospheric and mesospheric sounder (ISAMS) on the Upper Atmosphere Research Satellite. ISAMS is a limb-sounding infrared gas-correlation radiometer, measuring thermal emission from a range of constituents. The constituents measured are ozone, water vapor, methane, nitrous oxide, nitric oxide, nitrogen dioxide, nitrogen pentoxide, nitric acid, carbon monoxide, and aerosol. Atmospheric temperature and composition data were obtained for approximately 180 days between September 26, 1991, and July 29, 1992, with near-global coverage. The instrument and the retrieval process are briefly described, together with aspects of the validation process relevant to all data products, including the radiometric calibration and the analysis of the calibrated radiances to produce data on a standard time-altitude grid.

Abstract:

The improved stratospheric and mesospheric sounder (ISAMS) made ozone measurements in the stratosphere and mesosphere, with dense coverage over a broad range of latitudes, on about 180 days between September 1991 and July 1992. In this paper we are concerned with version 10 of the ISAMS data, which is recommended for use in the pressure range 10-0.1 mbar at night and 10-1 mbar during daytime. We describe the measurements and the retrieval algorithm, present an error analysis, and provide comparisons of the results to both climatological and coincident data. It is demonstrated that biases with respect to other well-validated data sets are less than 10%, which is well within the internal assessment of systemetic errors.