Proposed reference models for ozone

Ozone reference models are proposed here similar to the Keating and Young 1985 models which were prepared for the new COSPAR International Reference Atmosphere. This paper updates tables provided in the Keating and Young ozone model, giving improved monthly zonal mean total column ozone in 10° latitude increments, improved monthly zonal mean ozone volume mixing ratios (ppmv) from 20 to 0.003 mb in 10° latitude increments, and conversion tables providing ozone vertical structure in other units. Also, a new table is provided giving ozone vertical structure as a function of altitude (from 25 to 80 km), latitude, and month. The models are based on measurements from six contemporary satellite instruments.     

Proposed reference models for nitrous oxide and methane in the middle atmosphere

Data from the Stratospheric and Mesospheric Sounder (SAMS) on the Nimbus 7 satellite, for the three years from January 1979–December 1981, are used to prepare a reference model for the long-lived trace gases methane (CH₄) and nitrous oxide (N₂O) 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 50S to 70N, and for each month of the year. The means by which the data quality and interannual variability, and some of the more interesting globally and seasonally variable features of the data are discussed briefly.     

Southern hemisphere reference middle atmosphere

The wind part of the rocket-based empirical model of the middle atmosphere of the Southern Hemisphere is revised on the basis of new rocket and radar data. Wind and temperature values from this empirical model are compared with corresponding values from the satellite-based reference atmosphere compiled by Barnett and Corney. General similarity of the two models is confirmed, though marked discrepancies are sometimes revealed.     

Proposed reference models for CO2 and halogenated hydrocarbons

The vertical distribution of carbon dioxide, halocarbons and their sink products, HCl and HF, have become available, mainly by means of balloon measurements. Most measurements were made at northern mid-latitudes, but some constituents were measured at tropical latitudes and in the southern hemisphere as well. This report attempts to combine the available data for presentation of reference models for CO₂, CCl₄, CCl₃F, CCl₂F₂, CClF₃, CF₄, CCl₂F-CClF₂, CClF₂-CClF₂, CClF₂-CF₃, CF₃-CF₃, CH₃Cl, CHClF₂, CH₃-CCl₃, CBrClF₂, CBrF₃, HCl and HF.     

Proposal for a reference model of the middle atmosphere of the southern hemisphere

Available rocketsonde information has been used to compile tables of monthly mean temperature, pressure, density and zonal wind for the middle atmosphere of the southern hemisphere with the purpose of revising similar tables presented to COSPAR earlier. The altitude range is 25 to 80 km in steps of 5 km. The latitude range is 0° to 70°S with a 10° step. The compatability of different sets of temperature measurements is discussed. Mean values of temperature, pressure and zonal wind obtained for the southern hemisphere are compared with northern hemisphere model values. Large differences between the hemispheres (up to 20°C in temperature, 20–30% in pressure, 30–50 m/s in wind) imply that reference atmospheres such as CIRA should be complemented by southern hemisphere climatology.     

A middle atmosphere temperature reference model from satellite measurements

Temperature fields in the stratosphere and mesosphere have been derived from radiance measurements made by the Nimbus 5 SCR, the Nimbus 6 PMR, and the Nimbus 7 SAMS and LIMS radiometers. These instruments cover different latitude and height ranges and different times during the 1973–1983 period. The problems of combining different data sets are discussed, and examples from a proposed model atmosphere for the stratosphere and mesosphere are presented. The model is given in terms of zonal means and amplitude and phase of zonal waves 1 and 2 for temperature and geopotential height, as functions of latitude and pressure for each calendar month. Comparisons are made with the CIRA 1972 and the Koshelkov Southern Hemisphere models and with the SAMS results and in-situ rocket/radio sondes.     

Ionic mobility of the middle atmosphere

Positive ion mobilities are calculated for 40–75 km by computing the theoretical positive ion composition and combining it with laboratory-determined mobilities. Theoretical determinations for mobility appear to be especially apt for the 40–65 km region since oxonium ions are observed to be the principal positive ions and they should be subject to thermodynamic equilibrium. We compute a mean reduced mobility of 2.1 ± 0.1 cm²/V-s for 40–65 km using the 1976 U.S. Standard Atmosphere and a water vapor mixing ratio of 5 ppmv. The results are compared with atmospheric data for mobility. Observations of a lower mobility from about 35 km down to ground level are qualitatively compatible with the onset of the so-called non-proton hydrate ions at about this altitude and extending to lower heights. We note that the laboratory determined mobilities for oxonium ions average about 12 % less than the theoretical Langevin values. The total positive ion conductivity is determined also and compared with in-situ results.     

Ozone reference models for CIRA

The ozone reference model which is to be incorporated in the COSPAR International Reference Atmosphere (CIRA) is described and compared with other measurements of the Earth's ozone distribution. Ozone vertical structure models from approximately 25 to 90 km are provided combining data from five recent satellite experiments (Nimbus-7 LIMS, Nimbus-7 SBUV, AE-2 SAGE, Solar Mesosphere Explorer (SME) UVS, and SME IR). The results include the latest improvements in the SBUV algorithms using the most recent estimates of ozone cross sections. Also, the latest refinements in SME algorithms are incorporated. These algorithm improvements have improved agreement between the satellite data sets. Standard deviations are provided of monthly zonal means, and an estimate of the interannual variability is given. The models based on satallite data compare well with the Krueger and Minzner mid-latitude model incorporated into the U. S. Standard Atmosphere which is based on rocket and balloon measurements. Other comparisons are shown with Umkehr and more recent balloon data. Models are also provided of total columnar ozone reflecting recent improved estimates of ozone cross section. Information is provided on semiannual and annual variations. Other systematic variations including estimates of diurnal variations in the mesosphere will be included in the CIRA document.     

A simple model for the interhemispheric coupling of the middle atmosphere circulation

The interhemispheric coupling of the middle atmosphere general circulation is characterized by a global anomaly pattern of the zonal-mean temperature. This pattern reflects an anomalous stratospheric and mesospheric residual circulation, in which a weaker (stronger) stratospheric winter circulation is linked to an upward (downward) shift of its upper mesospheric branch reaching from the summer to the winter pole. This phenomenon is robust in observational data and several middle atmosphere general circulation models. In the present study, the recently proposed mechanism of the interhemispheric coupling is unequivocally proven within the framework of a zonally symmetric model that excludes any additional effects due to resolved waves and non-zonally propagating gravity waves. Two simulations are conducted that differ in the strength of the polar vortex. A weaker polar vortex results in a downward shift of the winter mesospheric gravity wave drag. This leads to changes also in the summer upper mesosphere via a feedback solely between gravity wave breaking and the zonal-mean state. The accompanying temperature anomaly reproduces the pattern of the interhemispheric coupling.     

Synoptic studies of the middle atmosphere using balloons

During the Middle Atmosphere Program, 1982–1985, balloons will play a central role in gathering stratospheric, chemical, and dynamical data. This paper discusses some of the unique aspects of balloons as tools for probing the middle atmosphere, and suggests some directions for future projects and enhanced capabilities that would improve their utility in future investigations.     

Dissipation of temperature perturbations in the middle atmosphere

It is often observed that the stratospheric and mesospheric temperature structure undergoes transient disturbances from its averaged steady-state behavior. The causes may be traceable to gravity waves, planetary waves, solar proton and relativistic electron precipitation, etc. We examine the theoretical time behavior of the atmospheric temperature following the cessation of such heating phenomena as it relaxes toward its quiescent steady-state value. We also study the time-dependent response during a model stratospheric-warming/mesospheric-cooling event. In particular, we investigate the roles of eddy heat conduction, non-LTE cooling in the 15μm CO₂ band, and an ambient vertical wind, and their relative importance as they depend upon altitude and time, in modifying temperature changes in this region.     

Temperature structure and dynamics of the middle atmosphere of Venus

The definitive data set for the mean thermal structure of the Venusian middle atmosphere is published for the first time. Some recent interim results on a modelling study to interpret the measured thermal field in terms of the global dynamics are also presented. These indicate that (a) the zonal winds on Venus fall to very low values above about 90 km, (b) there is a strong mid-latitude jet which circles the planet approximately every two days, (c) the observed solar tides are dominated by the semi-diurnal component, in agreement with theory.