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International audience; Upper stratospheric ozone anomalies from the satellite-borne Solar Backscatter Ultra-Violet (SBUV), Stratospheric Aerosol and Gas Experiment II (SAGE II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments agree within 5% or better with ground-based data from lidars and microwave radiometers at five stations of the Network for the Detection of Atmospheric Composition Change (NDACC), from 45°S to 48°N. From 1979 until the late 1990s, all available data show a clear decline of ozone near 40 km, by 10%–15%. This decline has not continued in the last 10 years. At some sites, ozone at 40 km appears to have increased since 2000, consistent with the beginning decline of stratospheric chlorine. The phaseout of chlorofluorocarbons after the International Montreal Protocol in 1987 has been successful, and is now showing positive effects on ozone in the upper stratosphere. Temperature anomalies near 40 km altitude from European Centre for Medium Range Weather Forecast reanalyses (ERA-40), from National Centers for Environmental Prediction (NCEP) operational analyses, and from HALOE and lidar measurements show good consistency at the five stations, within about 3 K. Since about 1985, upper stratospheric temperatures have been fluctuating around a constant level at all five NDACC stations. This non-decline of upper stratospheric temperatures is a significant change from the more or less linear cooling of the upper stratosphere up until the mid-1990s, reported in previous trend assessments. It is also at odds with the almost linear 1 K per decade cooling simulated over the entire 1979–2010 period by chemistry–climate models (CCMs). The same CCM simulations, however, track the historical ozone anomalies quite well, including the change of ozone tendency in the late 1990s.

The ultraviolet (UV) sensitivity of five species of freshwater zooplankton (three Cladocera, two Copepoda) were investigated. The animals were exposed to varying levels of UV‐radiation in a sunshine‐simulator and the UV doses for 10 and 50% mortality (LD10, LD50) were estimated using a dose‐response model. To place these doses in context they were compared with modelled clear‐sky surface UV irradiances in New Zealand. The cladocerans Daphnia carinata and Ceriodaphnia dubia were sensitive to levels of UVB irradiance of LD10 = 18–25 kJ m−2 and LD50 = 35–37 kJ m−2. These sensitivities are consistent with published values for other cladocera. In contrast a third cladoceran, Bosmina meridionalis, exhibited no higher mortality over the full range of the cumulative UVB‐doses used (3–40 kJ m−2) than controls receiving no UV exposure. The copepod Boeckella delicata showed the highest UV‐sensitivity of all organisms tested (LD10 = 7 kJ m−2, LD50 = 33 kJ m−2) whereas for Boeckella triarticulata, which was m...

Clouds are important modulators of UV radiation, but quantification of their effects has been limited. This preliminary study assesses satellite-derived fractional cloud cover as an estimator of cloud effects on UV radiation measured at Lauder, New Zealand. Although there is a good correlation between measures of cloud cover from satellite and from the ground, their correlation with surface irradiance in either the visible or UV parts of the spectrum is found to be weaker. Measurement of fractional cloud cover alone is inadequate to parameterize cloud effects on incoming radiation. In particular, knowledge of whether or not the Sun is obscured is required, while estimates of cloud optical depth also appear to be important. The strong correlation between UV and visible radiation suggests that the use of ground-based pyranometer data to infer cloud effects on UV radiation is more accurate than the use of presently available satellite data for process studies of the relationship between cloud cover and insta...

TOMS (Total Ozone Mapping Spectrometer) satellite data for 1988 have provided the opportunity for an investigation of spatial and temporal variations in total ozone over South Africa. Data for five South African stations and one southern ocean station. Gough Island, have been extracted from the TOMS data base. The seasonal peak in ozone occurs in October. Day-to-day variability is shown to increase with increasing latitude from Pretoria in the north to Gough Island in the south. as the influence of the transient eddies in the midlatitude westerlies becomes more dominant A model explaining the link between total ozone and a midlatitude wave is proposed. With the passage of a baroclinic westerly wave. north-westerly advection of ozone-poor air of tropical origin occurs in conjunction with a surface pressure minimum and upper air ridge. This is followed by the south-westerly advection of ozone-rich air of midlatitude origin in association with a surface high and stratospheric injection of ozone-rich...