Abstracts

A. F. Tuck (1), J. M. Russell III (2) and J. E. Harries (3)

(1) NOAA Aeronomy Laboratory, Boulder, CO 80304

(2) NASA Langley Research Center, Hampton, VA 23681

(3) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London

ABSTRACT

HALOE observations of water vapor and methane during the period 21 September - 15 October 1992 are used to examine the role of Antarctic drying in the lower stratosphere. Zonal mean cross-sections of [2 CH4 + H2O] show the probability of transport of Antarctic type dryness to latitudes as distant as 20-degrees-N, with major water vapor deficits evident between 10 and 100 mb to 10-degrees-S. Examination of monthly mean tropical 100 mb temperatures and of Antarctic temperatures suggests that the observations are consistent with stratospheric dryness being achieved by the combined effects of tropopause freeze- drying over the Micronesia region during northern winter and drying through the influence of the very low temperatures over Antarctica during southern winter. This paper presents these intriguing new results, and offers a possible explanation. Geophys. Res. Lett. (1993), Vol. 20, 1227-1230

J. E. Harries (1), J. M. Russell III (2), J. Park (2), A. F. Tuck (3), and S. R. Drayson (4)

(1) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London

(2) NASA Langley Research Center, Hampton, VA 23681

(3) NOAA Aeronomy Laboratory, Boulder, CO 80304

(4) University of Michigan, Ann Arbor, MI 48109

ABSTRACT

Measurements of the transmission of solar infrared radiation through the earth's atmosphere, by the HALOE experiment on the UARS spacecraft, were made at high southern latitudes during October 1991. These observations are direct measurements of atmospheric transmission, and do not need to be passed through a composition or temperature retrieval process; they are, therefore, amenable to direct interpretation. During October 1991 the profiles of transmittance versus height in the atmosphere show clear evidence for the arrival (from more northerly latitudes) of layers of some material which absorbs infrared radiation, at heights of up to 28 km. The spatial structure of the absorbing material shows considerable variability with longitude at a given latitude. The spectral properties of the detected absorption, measured at the various HALOE wavelengths, are consistent with absorption by sulphate aerosol, and clearly implicate the volcanic eruptions from Mts Pinatubo and Hudson during 1991. These results provide direct and detailed evidence for the arrival of layers of what appears to be sulphate aerosol during the 1991 southern spring, at latitudes as high as 80 degrees south. Quart. J. Roy. Meteor. Soc. (1995) Vol. 121, 655-667

J. E. Harries (1), J. M. Russell III (2), A. F. Tuck (3), L. L. Gordley (4), P. Purcell (2), K. Stone (4), R. M. Bevilacqua (5), M. Gunson (6), G. Nedoluha (5), and W. A. Traub (7)

(1) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London
Phone:  71-594-7670
Fax:  71-594-7681
E-Mail:  harries@haloe.larc.nasa.gov

(2) NASA Langley Research Center, Hampton, VA 23681

(3) NOAA Aeronomy Laboratory, Boulder, CO 80304

(4) G & A Technical Software, Hampton, VA 23666

(5) Naval Research Laboratory, Washington, DC 20375

(6) Jet Propulsion Laboratory, Pasadena, CA 91109

(7) Harvard Smithsonian Astrophysical Laboratory, Cambridge, MA 02138

ABSTRACT

The HALOE experiment is a solar occultation limb-sounder which operates between 2.45 and 10.0 µm to measure the composition of the mesosphere, stratosphere, and upper troposphere. It flies on board the Upper Atmosphere Research Satellite (UARS), which was launched in September 1991. Measurements are made of the transmittance of the atmosphere in a number of spectral channels as the sun rises or sets behind the limb of the atmosphere. One of the channels, at 6.60 µm, is a broad-band filter channel tuned to detect absorption in the Ã2 band of water vapour. This paper describes efforts to validate the absolute and relative uncertainties (accuracy and precision) of the measurements from this channel. The HALOE data have been compared with independent measurements, using a variety of observational techniques, from balloons, from the ground, and from other space missions, and with the results of a 2-D model. The results show that HALOE is providing global measurements throughout the stratosphere and mesosphere with an accuracy within ± 10% over most of this height range, and to within ± 30% at the boundaries, and to a precision in the lower stratosphere of a few percent. The H2O data are combined with HALOE measurements of CH4 in order to test the data in terms of conservation of total hydrogen, with most encouraging results. The observed systematic behavior and internal consistency of the HALOE data, coupled with these estimates of their accuracy, indicate that the data may be used for quantitative tests of our understanding of the physical and chemical processes which control the concentration of H2O in the middle atmosphere. J. Geophys. Res. (1996), Vol. 101, 10205-10216

J. E. Harries (1), S. Ruth (2), J. M. Russell III (3)

(1) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London

(2) Rutherford Appleton Laboratory, Didcot, Oxon, UK

(3) NASA Langley Research Center, Hampton, VA 23681

ABSTRACT

The Halogen Occultation Experiment (HALOE) is in orbit on NASA's Upper Atmosphere Research Satellite (UARS), and has been used to make measurements of a number of stratospheric and mesospheric constituents since October 1991. These include, amongst others, water vapour, H2O, and methane, CH4, two principal components of the total hydrogen budget of the middle atmosphere. The third main component is molecular hydrogen, H2, which is not measurable by HALOE or any other UARS sensor. By making the assumption that the total hydrogen content of the middle atmosphere is a conserved quantity, and that these three constituents dominate the budget, it is possible to infer the H2 fields in the mesosphere from the HALOE H2O and CH4 measurements. Geophys. Res. Lett. (1996) Vol 23, 297-300

 Evans S.J. (1), Toumi R. (1), Harries J.E. (1), Chipperfield M.P. (2), Russell J.M. (3)

(1) Blackett Laboratory, Imperial College of Science, Technology,
and Medicine, University of London

(2) Department of Chemistry, University of Cambridge, Cambridge, CB1 1EW

(3) Department of Physics, Hampton University, Hampton, VA,23668

ABSTRACT

Measurements of stratospheric water vapor and methane from the Halogen Occultation Experiment (HALOE) mounted on the Upper Atmosphere Research Satellite (UARS) are used to investigate changes in stratospheric water vapor over the period 1992-1996 inclusive. An increase in water vapor mixing ratio is found at levels between 30 km and 65 km across the globe which fit, to first order, a linear trend varying with altitude from 40 parts per billion by volume per year (ppbv yr(-1)) to a maximum of 90ppbv yr(-1) at 45 km. These trends appear to be greater than that expected due to the growth in tropospheric methane over the past several decades, and possible mechanisms accounting for this are discussed. The trend of the combined budget of 2 x CH4 + H2O is approximately constant with altitude with a global mean value of 61 +/- 4 ppbv yr(-1). On the basis of these estimates, sensitivity studies have been performed using a two-dimensional (2-D) radiative-chemical-dynamical model to assess the impact on concentrations of stratospheric ozone of this degree of change in stratospheric water vapor over timescales consistent with doubling CO2 scenarios. We find that the impact of increased stratospheric water vapor is to enhance the ozone increase in the midstratosphere by similar to 1 - 2% compared to the response due to a doubling of CO2 itself of similar to 5-10%. In the upper stratosphere the destruction of ozone is enhanced and the changeover from production to loss is lowered to similar to 50 km (from similar to 70 km). A chemical mechanism for these processes involving enhanced OH and NO2 is identified.

Jour. Geo. Res-Atm. (1998) Vol. 103, No. D8, pages 8175-8125