Information content and optimisation of high spectral resolution remote measurements
ADV SPACE RES 21:3 (1998) 361-367
Abstract:
Remote measurements of the atmosphere with high spectral resolution from the ground or from space. are being or will be made from a new generation of instruments such as the Fourier transform or grating spectrometers AIRS, MIPAS, TES or IASI. Such measurements would appear to contain a large amount. of information about the atmosphere, but it is not immediately obvious how to quantify it or to use it efficiently or effectively. The somewhat neglected concepts of 'information content' and 'degrees of freedom for signal' provide single parameters which can be used in the automated optimisation of, for example, instrument design parameters, the selection of microwindows or subsets of channels for retrieval: the optimisation of retrieval strategy, and the understanding of the information content of a spectrum. Some such applications are illustrated by means of simulated spectra for the AIRS instrument. (C) 1998 COSPAR. Published by Elsevier Science Ltd.Retrieval of tropospheric carbon monoxide for the MOPITT experiment
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 103:D24 (1998) 32277-32290
Towards a reference stratospheric aerosol loading
ADV SPACE RES 21:10 (1998) 1421-1424
Abstract:
Stratospheric aerosol loading is reviewed in the context of the parameters necessary to describe stratospheric aerosol in chemical and radiative studies. The large spatial and temporal variability of sulphate aerosol loading makes a single reference atmosphere impractical and it is suggested that the liquid content of sulphate aerosols be used in the construction of future reference atmospheres as this parameter is invariant to temperature changes. The construction of an a posteriori climatology is recommended (C) 1998 COSPAR. Published by Elsevier Science Ltd.Global evolution of the Mt Pinatubo volcanic aerosols observed by the infrared limb-sounding instruments CLAES and ISAMS on the Upper Atmosphere Research Satellite
J GEOPHYS RES-ATMOS 102:D1 (1997) 1495-1512
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.A new parameterization of scale-dependent radiative rates in the stratosphere - Reply
JOURNAL OF THE ATMOSPHERIC SCIENCES 54:10 (1997) 1393-1394