We would like to acknowledge the support and successful cooperation of NASA and CNES in the development and operation of CALIPSO and the advocacy of Gérard Mégie for the mission. We thank Bill Hunt and the team at Ball Aerospace for CALIOP and payload integration; the teams at SODERN and Thales Alenia Space for the IIR and platform integration, respectively; the operations teams at NASA and CNES; and the support of the ASDC and ICARE data centers, who all made essential contributions to the success of the CALIPSO mission. The work described in "The occurrence of marine stratus and stratocumulus" was carried out by T. Kubar in collaboration with D. E.

A climatology of aerosol surface area inferred from satellite measurements is used as input in a two-dimensional model to study the long-term evolution of polar ozone depletion, especially the Antarctic ozone hole. It is found that volcanic aerosol inputs very likely modulate the severity of the ozone hole. In particular, the rapid deepening of the ozone hole in the early 1980s, as s•n, for example, in the Halley Bay total ozone measurements, was probably caused by accelerated heterogeneous chemistry associated with an increase in aerosol surface area due to volcanic injection combined with the anthropogenic perturbation of stratospheric chlorine. This is further substantiated by the large Antarctic ozone decline observed and modeled after the eruption of Mount Pinatubo. A number of factors that influence the ozone hole are also investigated, including the effect of liquid versus frozen aerosol, the effects of denitrification and dehydration, the role of HOx in HC1 and C1ONO2 recovery, and the effect of chlorine partitioning at the start of winter. Denitrification tends to slightly increase modeled ozone loss, primarily between about 17 and 25 km late in the season, while dehydration tends to decrease the amount of ozone depletion. However, temperature and aerosol amount have the strongest control on the model ozone loss for a given chlorine loading. These findings suggest that future Arctic ozone depletion could be severe in unusually cold winters or years with large volcanic aerosol surface area. IntroductionGround-based and aircraft observations later confirmed that the vertical profile of ozone loss coincided with a region of highly Significant springtime ozone depletion in the Antarctic region enhanced active chlorine and that the active chlorine levels were was first pointed out by Farman et al. [1985] and has since been approximately sufficient to produce the observed rate of ozone confirmed by other ground-based and satellite observations loss [Anderson et al., 1989; de Zafra et al., 1987]. [Holmann et al., 1987; Stotarski et at., 1986]. It was hypothesized Chlorine-activating heterogeneous reactions are thus a critical that chlorine-catalyzed ozone destruction was largely responsible. element for producing the Antarctic ozone hole. During the late While chlorine-containing compounds in the lower stratosphere 1980s these heterogeneous reactions were all thought to occur on are usually found in the form of the chlorine reservoirs HC1 and the surface of PSCs. PSCs were thought to be either water ice C1ONO2 which do not destroy ozone, during the Antarctic winter (type 2) or frozen particles containing nitric acid (type 1). In and spring the partitioning is shifted toward ozone-destroying particular, NAT (nitric acid trihydrate) was thought to be the active forms. It was suggested that this transformation took place dominant aerosol formed [Crutzen and Arnold, 1986]. When by heterogeneous reactions (especially HCl+C1ONO2) on the temperatures were too warm for PSCs to form, heterogeneous surface of polar strat...

Raman backscatter of a frequency-doubled ruby laser beam by water vapor has been observed in the atmosphere, using an optical radar system. This return along with a Raman nitrogen return, has been used to calculate a relative water-vapor mixing ratio profile in the atmosphere to an altitude of approximately 2 km.

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We report observations of ozone column and clouds at typically stratospheric altitudes, obtained during the 1987 Airbone Antarctic Experiment from the TIROS Operational Vertical Sounder (TOVS)/High‐Resolution Infrared Sounder (HIRS 2) instrument on the National Oceanic and Atmospheric Administration NOAA 10 satellite. Cloud formation occurs mainly along the coast of Antarctica when strong tropospheric winds blow from the ocean to the continent. The period of September 2–9 provides a good example of the formation of localized high‐altitude clouds over the Palmer Peninsula and the Weddell Sea. The appearance of these clouds (a subset of the more prevalent polar stratospheric clouds (PSCs)) is consistent with the presence of a strong tropospheric jet over the elevated topography of the peninsula. Mountain waves and their associated high‐altitude adiabatic cooling are the driving mechanism for the cloud formation. On the basis of the cloud area coverage and wind analyses, we estimate that in the altitude range 14–18 km the air within the polar vortex has spent 5% of its time inside these clouds from early August to late September. The importance of this observation for springtime ozone depletion mechanisms is discussed. It is also concluded that the TOVS data set recorded during the past decade would be suitable to search for a possible trend in the cloud amount. Such a trend could be relevant to the rate of the Antarctic ozone depletion.