Earlier studies of solar-induced variations in stratospheric parameters have been mainly concerned with observed ozone responses. In the present investigation, attention is given to temperature responses as well as ozone responses at low latitudes, taking into account 22 months of Nimbus 7 solar backscattered ultraviolet (SBUV) ozone and stratospheric and mesospheric sounder temperature data. A data description is provided, and cross-correlation and regression analyses are conducted. An extension is considered of an analytic model, which was derived by Frederick (1981) for the coupled behavior of ozone and temperature perturbations in the upper stratosphere and lower mesosphere. The extended model is applied to the results of the analyses. The obtained data provide statistical evidence for ozone and temperature responses to changes in solar ultraviolet flux on the time scale of the solar rotation period.

Coupled stratospheric ozone and temperature responses to short-term changes in solar ultraviolet flux: An analysis of Nimbus 7 SBUV and SAMS data

The effects of solar UV variability on ozone and temperature are studied using Nimbus 7 stratospheric and mesospheric ozone, temperature, and 205-nm solar UV data, and Solar Mesosphere Explorer 1.27-micron ozone and 121.6-nm solar UV data. Consideration is given to the temperature/UV relation, the O3/UV relation with and without temperature feedback, and the responses of HNO3 and NO2 to solar UV variability. It is observed that the response times of temperature to solar UV variability are 6 days at 2 mbar and 1 day at 0.01 mbar. The stratospheric ozone response (with no correction for temperature effects) increases, while in the mesosphere a decrease is detected. The responses of ozone and temperature to solar variability are examined and calculated using a one-dimensional chemical-radiative time-dependent model. The comparison of the model results with the satellite-observed responses reveals generally good correlation between the data; however, the model predicts a larger time lag of the temperature response and a larger stratospheric HNO3 mixing ratio than the satellite data. It is noted that the relation between short-term variations in the solar UV radiation and stratospheric ozone is affected by the coupling between ozone and temperature.

Response of middle atmosphere to short‐term solar ultraviolet variations: 1. Observations

Ozone and temperature responses to solar variability, based on satellite data, have been reported in a companion paper (Keating et al., this issue). The present paper is intended to present a theoretical interpretation of this analysis with the purpose of better understanding the chemical behavior of the stratosphere and the coupling between temperature and ozone concentration, when a periodic forcing is applied to the solar ultraviolet (UV) flux. The response of the temperature and of the trace species concentrations, including ozone, to short-term variations in the solar UV irradiance is calculated by a one-dimensional chemical-radiative time-dependent model. The applied solar variability is assumed to be sinusoidal with a period of 27 days (in accordance with the rotation period of the sun) or 13.5 days (when two active regions are on opposite sides of the sun). The amplitude varies with wavelength, which is consistent with observations made by the Nimbus 7 solar backscattered ultraviolet (SBUV) experiment. The maximum ozone sensitivity in the stratosphere appears to be located near 3 mbar. The calculated amplitude and phase of the ozone response are significantly modified when the feedback between ozone and temperature is taken into account. The ozone/temperature coupling tends to modify the ozone phase lag such that, in the upper stratosphere and in the mesosphere, the ozone peak occurs a few days before the UV peak. Comparison of the model results with the observed ozone and temperature responses, based on satellite data, shows that the theory is consistent in many respects with observations. The calculated time lag of the temperature response, however, is approximately a factor of 2–4 smaller than the time lags derived from the measurements, suggesting evidence for some additional process not included in the model calculation. Large negative ozone sensitivities and positive temperature responses are predicted in the mesosphere as a result of the absorption by O2 of the solar irradiance at the Lyman α wavelength. The model also shows that the expected variation in the stratospheric nitric acid mixing ratio is a factor 2 larger than the corresponding opposite variation in the ozone concentration.

Response of middle atmosphere to short-term solar ultraviolet variations: 2. Theory

The temporal and spatial features of stratospheric fluctuations are analyzed using 2.5 years of ozone and temperature data from the Nimbus 7 solar backscattered ultraviolet and the SAMS experiments. It is observed that the oscillations are dynamically induced perturbations in the winter hemisphere and the 27-day modulation of the solar UV radiation. The fluctuations in the ozone and temperature are compared with solar activity. The effects of solar and temperature perturbations on stratospheric ozone are examined; it is shown that the dynamically induced oscillations are global and independent of solar activity. The seasonal, latitudinal, and altitudinal variations of the regression factors and their influence on the ozone are studied. Multiple regression and cross-spectral analyses of ozone, temperature, and solar flux data reveal that the ozone mixing ratio is more sensitive to changes in temperature than changes in solar activity.

The solar and dynamically induced oscillations in the stratosphere

A general purpose stochastic sequential estimator is described, which allows the inverse problem of remote sounding to be solved in an optimum manner. The use of a sequential estimator allows continuity in the horizontal or in time to be included, making the a priori estimate close to the final solution, so that iteration is not required. The scan pattern in which measurements are made is not used and need not be known, so that the problem of spacecraft attitude stability is minimized. The method gives both a solution profile and its error covariance. It is applied to both temperature and composition sounding from a limb scanning instrument, the SAMS on NIMBUS 7.

Retrieval of temperature and composition from NIMBUS 7 SAMS measurements

The measuring task, the engineering constraints, and the resulting design of the stratospheric and mesospheric sounder are described in broad terms. The calibration system and its performance are discussed in more detail. One significant side effect in the design and its impact on the fields of view is also discussed. The major lessons for future pressure modulator radiometer designs are summarized.

G. D. Peskett

Papers

Some aspects of the design and behavior of the stratospheric and mesospheric sounder