An aerosol trajectory model (ATM), which couples TOMS aerosol index (AI) measurements with multiple‐level parcel trajectories, is presented for determining the three‐dimensional (3‐D) distribution of a tropospheric aerosol cloud. The ATM is illustrated with an idealized 2‐D (height‐longitude) cloud in linear vertical shear. The half width of the vertical parcel distribution (an indicator of how well the cloud is resolved) is inversely proportional to time and to vertical shear. The degree to which a cloud can be resolved is limited by an “uncertainty principle,” whereby model precision improves with time, while accuracy degrades with time because of accumulating trajectory errors. ATM is applied to the ash cloud from the September 1992 eruption of Mount Spurr, Alaska. Disagreement in the predicted cloud structure occurs between 3‐day ATM runs using United Kingdom Meteorological Office (UKMO) and National Centers for Environmental Prediction (NCEP) winds. This is due to significant differences in the UKMO and NCEP zonal wind speed near the tropopause, which cause large trajectory separations over 3 days. The UKMO‐predicted cloud range (310–390 K) agrees well with radar and pilot observations of the ash cloud, while the NCEP‐predicted range shows strong disagreement with observations in the region of the jet maximum. This indicates the potential (when independent observations are available) for using ATM to partially validate wind fields.
Measurements of ClO (Brune et al., 1990) acquired during the Airborne Arctic Stratospheric Expedition are used to infer concentrations of reactive chlorine (ClO+2 × Cl 2 O 2 ). Observed fields of potential temperature and potential vorticity are used to extrapolate in situ data to larger regions of the vortex. Calculated values of the loss rate of O 3 , based on estimates of reactive chlorine and measurements of BrO (Toohey et al., 1990), suggest that the loss of O 3 was about 12% for levels of the atmosphere with potential temperatures between 440 and 470 K over the 39 day duration of the ER‐2 flights into the polar vortex. Calculated loss rates agree with observed rates of removal of O 3 , although significant uncertainties exist for each.
The wind and constituent measurements from the polar aircraft data are used to compute the flux spectra. Although there is variation from flight to flight, the flux spectra generally fit a −2 to −1.5 power law as expected theoretically. This result suggests that tracer fluxes from small scale features do not substantially contribute to the overall tracer budget relative to the fluxes from the larger scales.
The effects of various ozone density reductions of the zonally averaged circulation are evaluated with a numerical quasi-geostrophic model. If the ozone perturbations are confined to the polar regions and are minuscule on a global basis as was characteristic of the August 1972 solar proton event, then the calculations indicate a negligible effect on the mean circulation. For global ozone perturbations by predicted halocarbon pollution, about 10% reduction in the zonal jet strength and less than a 5% change in global mean stratospheric temperature are calculated. Large, uniform ozone reductions (above 50%) produce significant effects on the mean circulation: a substantial collapse of the stratosphere due to cooler temperatures, and a weak polar night jet. The reflection and transmission of quasi-stationary planetary waves in the middle atmosphere are computed to be insensitive to solar activity as extreme as the August 1972 solar proton event. It thus seems improbable that planetary waves are a viable mechanism for solar-weather interactions that involve perturbations of the zonally averaged circulation by ozone density reductions.
Abstract. We derive stratospheric aerosol microphysical parameters from Ozone Mapping Profiler Suite Limb Profiler (OMPS-LP) satellite measurements using aerosol extinction coefficient ratios at two wavelengths (the color ratio), which is sensitive to the particle radius, and concentration. We estimate various sources of uncertainty in this technique including extinction coefficient measurement error, sensitivity to the size distribution width assumption, and the OMPS-LP algorithm phase function error. We apply our algorithm to extinction coefficient measurements made by the Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) to verify our approach and find that our results are in good agreement. Our results also compare favorably to balloon borne particle size measurements and concentrations under ambient condition and 2019 Raikoke volcanic eruption assuming a log-normal particle size distribution width of 1.6. We also estimate the changes in aerosol median radius and concentration following the 2019 Raikoke and 2022 Hunga Tonga-Hunga Ha’apai volcanic eruptions and the result is consistent with other retrievals published in the literature.
The quasi-geostrophic integrated enstrophy budget for the 1978 to 1979 winter has been analyzed from 10-0.1 mb using LIMS data. During January and late February periods a significant imbalance in the budget appears at 10mb. This imbalance is attributed to Rossby wave breaking. It is produced by the irreversible transfer of enstrophy to smaller scales not resolved by LIMS. The imbalance episodes correspond well to the appearance of Ertel vorticity filaments shown by McIntyre and Palmer (1984). From a seasonal viewpoint, the integrated enstrophy shows an average (although irregular) transfer from a zonal mean reservoir to waves which are then dissipated. On a shorter time scale the integrated enstrophy sloshes back and forth between the waves and mean flow in early winter; then, beginning with the January sudden warming, the total enstrophy is reduced more rapidly. Between 10 mb and 1 mb this reduction is more or less continuous until the end of February. However, in the mesosphere the total enstrophy decrease is very short lived, being quickly restored after the January warming. Even though the zonal mean integrated enstrophy is large, only about 10% can be utilized by the waves. The available integrated potential enstrophy is introduced, which is a better measure of how close the flow is to saturation by Rossby waves. The largest amount of available potential enstrophy in early January is at 1 mb with decreasing amounts above and below. Saturation of the flow by Rossby waves occurs below 1 mb only coincident with sudden warmings; however, at mesospheric heights the flow appears to be nearly saturated throughout the winter.
Abstract. We derive stratospheric aerosol microphysical parameters from Ozone Mapping Profiler Suite Limb Profiler (OMPS-LP) satellite measurements using aerosol extinction coefficient ratios at two wavelengths (the color ratio), which is sensitive to the particle radius, and concentration. We estimate various sources of uncertainty in this technique including extinction coefficient measurement error, sensitivity to the size distribution width assumption, and the OMPS-LP algorithm phase function error. We apply our algorithm to extinction coefficient measurements made by the Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) to verify our approach and find that our results are in good agreement. Our results also compare favorably to balloon borne particle size measurements and concentrations under ambient condition and 2019 Raikoke volcanic eruption assuming a log-normal particle size distribution width of 1.6. We also estimate the changes in aerosol median radius and concentration following the 2019 Raikoke and 2022 Hunga Tonga-Hunga Ha’apai volcanic eruptions and the result is consistent with other retrievals published in the literature.
The Upper Atmosphere Research Satellite (UARS) was launched in September 1991 with a complement of 10 instruments focused on the middle and upper atmospheric processes, and on solar irradiance variability. After nearly three years of successful UARS operations, eight of the ten instruments continue to operate. Data is routinely processed and reprocessed on a central facility. This data is now being distributed electronically to the scientific community. Among the more important UARS accomplishments are the first global mapping of ozone depleting chlorine radicals and reservoirs, measurement of middle atmosphere winds, the tracking of the Mt. Pinatubo aerosols, and highly accurate measurements of solar ultraviolet variability.
