Revelations of a stratospheric circulation: The dynamical transport of hydrocarbons in the stratosphere of Uranus

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7297740

McMillan, W W

Observations by the Ultraviolet Spectrometer (UVS) onboard the Voyager 2 spacecraft revealed that above the 1 mb level, the mixing ratios of CH[sub 4], C[sub 2]H[sub 2], and C[sub 2]H[sub 6] are at least 10-100 times larger at the equator than at the south pole. In addition, the Voyager 2 Infrared Interferometric Spectrometer (IRIS) measured small meridional temperature gradients at the tropopause (60-200 mb) and in the upper troposphere (200-1000 mb) of Uranus. These temperature gradients result from a weak meridional circulation in the Uranian troposphere which penetrates into the stratosphere with upwelling at low southern latitudes and polar subsidence (vertical velocities [approximately]10[sup [minus]6] m/s, meridional velocities [approximately]10[sup [minus]3] m/s). The role of the zonally-averaged, meridional stratospheric circulation in determining the distribution of hydrocarbons in the stratosphere (0.1-100 mb) of Uranus is investigated with a 2-dimensional photochemical transport model. The stratospheric circulation is calculated with a linear, zonally-symmetric model with Newtonian cooling and Rayleigh friction similar to that used by Flaser et al. (1987). Operator-splitting is utilized to numerically solve the continuity equations for trace species in the stratosphere of Uranus. It is determined that advective transport by the stratospheric circulation can account for the essential observed meridional variation of stratospheric hydrocarbon abundances. However, vertical transport by eddy and molecular diffusion is required to fit the inferred vertical distribution of hydrocarbons. The uniform eddy diffusion coefficient is constrained to 10 cm[sup 2]/s < K < 100 cm[sup 2]/s (i.e. constant in both altitude and latitude). The best fit model has a meridional circulation three times stronger than the circulation of Flaser et al. and a weak uniform eddy diffusion coefficient, K = 100 cm[sup 2]/s.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States)
• OSTI ID: 7297740
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
540120 -- Environment
Atmospheric-- Chemicals Monitoring &amp; Transport-- (1990-)
ATMOSPHERIC CHEMISTRY
ATMOSPHERIC CIRCULATION
CHEMICAL REACTIONS
CHEMISTRY
EARTH ATMOSPHERE
HYDROCARBONS
INFRARED SPECTRA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PLANETS
SPECTRA
STRATOSPHERE
ULTRAVIOLET SPECTRA
URANUS PLANET