Publications by Fred Taylor

Cloud structure and atmospheric composition of Jupiter retrieved from Galileo near-infrared mapping spectrometer real-time spectra

Journal of Geophysical Research E: Planets 103 (1998) 23001-23021

PGJ Irwin, AL Weir, SE Smith, FW Taylor, AL Lambert, SB Calcutt, PJ Cameron-Smith, RW Carlson, K Baines, GS Orton, P Drossart, T Encrenaz, M Roos-Serote

The first four complete spectra recorded by the near infrared mapping spectrometer (NIMS) instrument on the Galileo spacecraft in 1996 have been analyzed. These spectra remain the only ones which have been obtained at maximum resolution over the entire NIMS wavelength range of 0.7 - 5.2 μm. The spectra cover the edge of a "warm" spot at location 5°N, 85°W. We have analyzed the spectra first with reflecting layer models and then with full multiple scattering models using the method of correlated-k. We find that there is strong evidence for three different cloud layers composed of a haze consistent with 0.5-μm radius tholins at 0.2 bar, a cloud of 0.75-lim NH 3 particles at about 0.7 bar, and a two-component NH 4 SH cloud at about 1.4 bars with both 50.0- and 0.45-μm particles, the former being responsible for the main 5-μm cloud opacity. The NH 3 relative humidity above the cloud tops is found to decrease slightly as the 5-μm brightness increases, with a mean value of approximately 14%. We also find that the mean volume mixing ratio of ammonia above the middle (NtL 4 SH) cloud deck is (1.7± 0.1) × 10 -4 and shows a similar, though less discernible decrease with increasing 5-μm brightness. The deep volume mixing ratios of deuterated methane and phosphine are found to be constant and we estimate their mean values to be (4.9± 0.2) × 10 -7 and (7.7 ± 0.2) × 10 -7 , respectively. The fractional scale height of phosphine above the 1 bar level is found to be 27.1± 1.4% and shows a slight decrease with increasing 5-μm brightness. The relative humidity of water vapor is found to be approximately 7%, but while this and all the previous observations are consistent with the assumption that "hot spots" are regions of downwelling, desiccated air, we find that the water vapor relative humidity increases as the 5-μm brightness increases. Copyright 1998 by the American Geophysical Union.

Atmospheric, oceanic and planetary physics, Oxford University

ASTRONOMY & GEOPHYSICS 39 (1998) 26-26

FW Taylor

Comment on "Carbon monoxide in Jupiter after comet Shoemaker-Levy 9," by K.S. Noll, D. Gilmore, R.F. Knacke, M. Womak, C.A. Griffith, and G. Orton

ICARUS 133 (1998) 321-321

R Beer, FW Taylor

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 (1997) 1495-1512

A Lambert, RG Grainger, CD Rodgers, FW Taylor, JL Mergenthaler, JB Kumer, ST Massie

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.

Radiative transfer models for Galileo NIMS studies of the atmosphere of Jupiter

ADV SPACE RES 19 (1997) 1149-1158

PGJ Irwin, SB Calcutt, FW Taylor

Scientific results from NIMS observations of Venus have been extensively reported in the literature, while those of Jupiter have, at the time of writing, just barely commenced. The planning and interpretation of studies of these planets, with their massive atmospheres and exotic compositions (by terrestrial standards), requires a comprehensive treatment of radiative transfer in both. This paper describes work done at Oxford to develop the underlying theory and practical radiative transfer schemes, with particular reference to the NIMS wavelength range, spectral resolution, and scientific objectives for Jupiter. Equivalent work for Venus has already been reported in the literature (e.g. Kamp and Taylor, 1990) and will not be covered in detail here. (C) 1997 COSPAR. Published by Elsevier Science Ltd.

UARS first global N<inf>2</inf>O<inf>5</inf> data sets: Application to a stratospheric warming event in January 1992

Journal of Geophysical Research Atmospheres 102 (1997) 3575-3582

JB Kumer, SR Kawa, AE Roche, JL Mergenthaler, SE Smith, FW Taylor, PS Connell, AR Douglass

For the first time, global measurements of N < inf > 2 < /inf > O < inf > 5 < /inf > are available for study. N < inf > 2 < /inf > O < inf > 5 < /inf > has long been a missing link in large-scale observations of stratospheric nitrogen species, the chemical family that comprises the major global loss cycle for ozone above about 25 km [McElroy et al., 1992]. N < inf > 2 < /inf > O < inf > 5 < /inf > is also an important intermediate in conversion of NO < inf > x < /inf > to HNO < inf > 3 < /inf > , thus limiting the effect of nitrogen-catalyzed ozone destruction below about 25 km [Fahey et al., 1993]. The new N < inf > 2 < /inf > O < inf > 5 < /inf > observations come from both the Cryogenic Limb Array Etalon Spectrometer (CLAES) and Improved Stratospheric and Mesospheric Sounder (ISAMS) instruments on the Upper Atmosphere Research Satellite (UARS), providing near-global coverage at high spatial and temporal resolution for almost 20 months. Here we focus on data obtained near 40 km during a stratospheric warming in January 1992. The N < inf > 2 < /inf > O < inf > 5 < /inf > fields show globally coherent structures with large variation in response to global transport coupled with highly temperature dependent chemistry. Comparison of the data with chemistry and transport models indicates that our understanding of processes controlling N < inf > 2 < /inf > O < inf > 5 < /inf > amounts and the interaction with other reactive nitrogen species is largely accurate under most conditions; however, an exceptional disagreement is found in the prolonged polar dark. This example demonstrates the utility of global data to understand the combined effects of chemistry and transport on N < inf > 2 < /inf > O < inf > 5 < /inf > under a wide range of conditions.

A GCM climate database for Mars: For mission planning and for scientific studies

ADV SPACE RES 19 (1997) 1213-1222

PL Read, M Collins, F Forget, R Fournier, F Hourdin, SR Lewis, O Talagrand, FW Taylor, NPJ Thomas

The construction of a new database of statistics on the climate and environment of the Martian atmosphere is currently under way, with the support of the European Space Agency. The primary objectives of this database are to provide information for mission design specialists on the mean state and variability of the Martian environment in unprecedented detail, through the execution of a set of carefully validated simulations of the Martian atmospheric circulation using comprehensive numerical general circulation models. The formulation of the models used are outlined herein, noting especially new improvements in various schemes to parametrize important physical processes, and the scope of the database to be constructed is described. A novel approach towards the representation of large-scale variability in the output of the database using empirical eigenfunctions derived from statistical analyses of the numerical simulations, is also discussed. It is hoped that the resulting database will be of value for both scientific and engineering studies of Mars' atmosphere and near-surface environment. (C) 1997 COSPAR. Published by Elsevier Science Ltd.

Pathfinder on Mars

ASTRONOMY & GEOPHYSICS 38 (1997) 15-16

FW Taylor

Reference Model for Methane and Nitrous Oxide

Advances in Space Research 18 (1996) 91-124

FW Taylor, A Dudhia, CD Rodgers

Data from the Stratospheric and Mesospheric Sounder (SAMS) on Nimbus 7 have been used as the basis for a model of the abundances of nitrous oxide and methane in the stratosphere. The model is presented in tabular form on seventeen pressure surfaces from 20 to 0.1-mb, in 10° latitude bins from 50°S to 70°N, and for each month of the year. Some details of the acquisition of the data which went into the model, its limitations, and the general behaviour of methane and nitrous oxide in the middle atmosphere are given. Formal errors in the data and other uncertainties, interannual variability, and systematic trends are discussed. As expected, no trends which exceed the estimated error in the data are found in either methane or nitrous oxide over the five-year period of SAMS observations.

Remote sensing of the Earth from space

CONTEMPORARY PHYSICS 37 (1996) 391-405

FW Taylor

Remote sounding of the Martian atmosphere in the context of the InterMarsNet mission: General circulation and meteorology

PLANET SPACE SCI 44 (1996) 1347-1360

FW Taylor, SB Calcutt, PGJ Irwin, DJ McCleese, JT Schofield, DO Muhleman, RT Clancy, CB Leovy

A concept has been developed for a remote sensing experiment to investigate the physics of the Martian atmosphere from a spin-stabilized orbiter, like that planned for the InterMarsNet mission. Using coincident infrared and microwave channels and limb-to-limb scanning, it can map the planet much more extensively than previously in temperature atmospheric dust loading, and humidity. When combined with one or more surface stations measuring the same variables, the sounder experiment can contribute to major progress in understanding the general circulation and dust and water cycles of the atmosphere of Mars, and the characterization of medium-scale meteorological systems. Copyright (C) 1996 Elsevier Science Ltd

Stratospheric methane distributions: Comparisons of a CIRA reference model and recent observational data


SL Ruth, JJ Remedios, FW Taylor, AE Roche, JB Kumer

Improved stratospheric and mesospheric sounder validation: General approach and in-flight radiometric calibration

Journal of Geophysical Research Atmospheres 101 (1996) 9775-9793

CD Rodgers, RJ Wells, RG Grainger, FW Taylor

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. Copyright 1996 by the American Geophysical Union.

Measurements of methane and nitrous oxide distributions by the improved stratospheric and mesospheric sounder: Retrieval and validation


JJ Remedios, SL Ruth, CD Rodgers, FW Taylor, AE Roche, JC Gille, MR Gunson, JM Russell, J Park, EC Zipf, PW Erdman

Dinitrogen pentoxide measurements from the improved stratospheric and mesospheric sounder: Validation of preliminary results


SE Smith, A Dudhia, PE Morris, JJ Remedios, CD Rodgers, FW Taylor, BJ Kerridge, MP Chipperfield, JB Kumer, AE Roche, MR Gunson

Stratospheric nitrous oxide distributions: Comparisons of a CIRA reference model and new observational data


JJ Remedios, SL Ruth, FW Taylor, AE Roche, JB Kumer

Validation of temperature measurements from the improved stratospheric and mesospheric sounder

Journal of Geophysical Research Atmospheres 101 (1996) 9795-9809

A Dudhia

Atmospheric temperature measurements from the improved stratospheric and mesospheric sounder (ISAMS) are evaluated. Flown on the Upper Atmosphere Research Satellite (UARS), ISAMS obtained 180 days of science data between September 26, 1991 and July 29, 1992. Typically, over 2600 temperature profiles/day were retrieved, spaced every 200 km along the limb-viewing track and nominally extending from 100 to 0.01 mbar (15-80 km). The latitude coverage ranged from 80°S to 80°N, depending on the particular ISAMS/UARS viewing geometry on any day. UARS is in a near-Sun-synchronous orbit, so that while the 15 orbits/d are spaced approximately every 24° longitude around the equator, the sampled local solar time actually changes by 20 min/d. The ISAMS temperature retrieval process is outlined and the various products are described. A detailed error budget for the retrieval is presented and comparisons are made with temperature measurements from other sources. Finally, a table is provided summarizing the best estimates of ISAMS temperature bias and precision. The results suggest a general cold bias of around 1 K in the stratospheric temperatures, with a superimposed 2-3 K warm bias associated with the densest part of the Pinatubo aerosol cloud. The precision of individual profiles is ±2 K throughout the stratosphere but falls off in the mesosphere to about ±10 K at 80 km. The error bars produced by the retrieval appear to be reasonable (although slightly pessimistic) estimates of the precision. Copyright 1996 by the American Geophysical Union.

Calculated k distribution coefficients for hydrogen- And self-broadened methane in the range 2000-9500 cm-1 from exponential sum fitting to band-modelled spectra

Journal of Geophysical Research E: Planets 101 (1996) 26137-26154

PGJ Irwin, SB Calcutt, FW Taylor, AL Weir

The spectral band data derived by Strong et al. [1993] for laboratory-measured transmission spectra of hydrogen-broadened methane at 10 cm -1 resolution have been fitted with k coefficients over a wide range of pressures and temperatures representing those likely to be encountered in the atmosphere of Jupiter. The mean fitting error is found to be only 2.0×10 -3 in transmission. These data are essential for the scattering calculations likely to be necessary for analysis of the data from the Near Infrared Mapping Spectrometer aboard the NASA Galileo spacecraft. The new data have significant advantages over those previously derived by Baines et al. [1993] in that they cover a wider spectral range, are applicable to longer paths, and also apply to the hydrogen-broadened case, which is the dominant broadening mechanism in this atmosphere. A similar table has also been calculated for the self-broadening case for comparison. Copyright 1996 by the American Geophysical Union.

Measurements of water vapor distributions by the improved stratospheric and mesospheric sounder: Retrieval and validation


M GossCustard, JJ Remedios, A Lambert, FW Taylor, CD Rodgers, M LopezPuertas, G Zaragoza, MR Gunson, MR Suttie, JE Harries, JM Russell

The H<inf>2</inf>so<inf>4</inf> component of stratospheric aerosols derived from satellite infrared extinction measurements: Application to stratospheric transport studies

Geophysical Research Letters 23 (1996) 2219-2222

A Lambert, RG Grainger, HL Rogers, WA Norton, CD Rodgers, FW Taylor

The ambient water vapour and temperature conditions of stratospheric sulphate aerosol particles govern their composition and thereby influence their infrared extinction properties. This causes problems in the use of the infrared aerosol extinction as a tracer because variations in the aerosol composition modify the changes in extinction that may arise from the transport of aerosols. An improved tracer which can be derived from measurements of the infrared aerosol extinction, temperature and water vapour abundance, is the H 2 SO 4 component of aerosols. The application of this tracer to studies of stratospheric transport is demonstrated using data from instruments on the Upper Atmosphere Research Satellite and the results are compared to a contour advection calculation. Copyright 1996 by the American Geophysical Union.