Recent field programs on glaciers have supplied information that makes simulation of glacier mass balance with meteorological models meaningful. An estimate of world-wide glacier sensitivity based on a modeling study of 12 selected glaciers situated in widely differing climatic regimes shows that for a uniform 1 K warming the area-weighted glacier mass balance will decrease by 0.40 meter per year. This corresponds to a sea-level rise of 0.58 millimeter per year, a value significantly less than earlier estimates.

The first view of stratospheric and tropospheric ozone variability in the Southern Hemisphere tropics is provided by a 3‐year record of ozone soundings from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network (http://croc.gsfc.nasa.gov/shadoz). Observations covering 1998–2000 were made over Ascension Island, Nairobi (Kenya), Irene (South Africa), Réunion Island, Watukosek (Java), Fiji, Tahiti, American Samoa, San Cristóbal (Galapagos), and Natal (Brazil). Total, stratospheric, and tropospheric column ozone amounts usually peak between August and November. Other features are a persistent zonal wave‐one pattern in total column ozone and signatures of the quasi‐biennial oscillation (QBO) in stratospheric ozone. The wave‐one is due to a greater concentration of free tropospheric ozone over the tropical Atlantic than the Pacific and appears to be associated with tropical general circulation and seasonal pollution from biomass burning. Tropospheric ozone over the Indian and Pacific Oceans displays influences of the waning 1997–1998 El Niño, seasonal convection, and pollution transport from Africa. The most distinctive feature of SHADOZ tropospheric ozone is variability in the data, e.g., a factor of 3 in column amount at 8 of 10 stations. Seasonal and monthly means may not be robust quantities because statistics are frequently not Gaussian even at sites that are always in tropical air. Models and satellite retrievals should be evaluated on their capability for reproducing tropospheric variability and fine structure. A 1999–2000 ozone record from Paramaribo, Surinam (6°N, 55°W) (also in SHADOZ) shows a marked contrast to southern tropical ozone because Surinam is often north of the Intertropical Convergence Zone (ITCZ). A more representative tropospheric ozone climatology for models and satellite retrievals requires additional Northern Hemisphere tropical data.

[1] The satellite instrument Global Ozone Monitoring Experiment (GOME), on board the ERS-2 mission of the European Space Agency, is measuring backscattered sunlight from the atmosphere in the range from 240 to 790 nm. This spectrum is used for deriving global, height-resolved information on the ozone distribution in the atmosphere. Contrary to total ozone column retrieval, the retrieval algorithm for ozone profiles requires absolutely calibrated reflectivity spectra. However, the in-flight calibration of the GOME reflectivity spectra needs to be corrected before the spectra can be used for profile retrieval. A general method for this calibration correction of satellite data and the profile retrieval method are described in this paper. The retrieved profiles from the recalibrated reflectivity spectra of GOME differ in the stratosphere by up to 50% from retrieved profiles without the correction. With the calibration correction, improved ozone profiles are retrieved for the complete range of 0-50 km. The GOME ozone profiles have been validated with ground and satellite measurements at a representative urban midlatitude and a rural tropical ground station.

This study entails the parameterization, by means of a linear multiple-regression analysis, of the annual surface temperature and mass balance of Antarctica. The analysis was performed for the entire ice cap as well as for three separate regions: ice shelves (elevation less than 200 m), the interior (elevation above 1500 m), and the escarpment region in between. It was found that temperature can be parameterized very well in terms of elevation and latitude. The latitudinal gradient on the ice shelves can be explained by the super-adiabatic lapse rate along the surface and latitudinal temperature gradient in the interior, assuming adiabatic descent of air in the inversion layer from the interior region towards the coast and an axisymmetric spreading over the ice shelves. The surface mass balance can be parameterized reliably only in the interior, where it has a strong positive correlation with the saturation vapour pressure of the free atmosphere, and a significant correlation with the shape of the dome. The convex shape of the dome contributes to the mass balance by inducing subsidence of the relatively moist air of the free atmosphere into the inversion layer. This results in precipitation, as radiative cooling in the inversion exceeds adiabatic warming. An estimate is made of the annual horizontal and vertical advective velocities in the free atmosphere above the interior, based on regression results and a physical analysis of the precipitation processes in this region .A temperature sensitivity analysis was performed for the current mass-balance distribution . For a I K rise in surface temperature, the regression estimate of the increase in accumulation on the grounded ice sheet is equivalent to a rate of sea-level lowering of 0.2 mm a-1 . This is about 30% less than estimates based on the current mass balance perturbated by the increase in saturation vapour pressure of the free atmosphere .

An attempt is made to construct a zonal and monthly mean ozone climatology for use in general circulation models, based on a combination of ozonesonde and satellite observations. One important advantage of such a climatology is a more realistic ozone distribution around the tropopause, where heating rates and climate forcing are most sensitive to changes in gas concentrations. Also, a linear trend study is performed, for the periods 1970-83 and 1980-93 separately, on concurrent ozone and temperature data obtained from a selection of ozonesonde stations. On average for northern poiar-to mid-latitudes, these trends are insignificant for stratospheric ozone and temperature in the first period, but for the second period show a stratosphetic ozone depletion and stratospheric cooling of around -0.5 %/yearand -0. 15 K/year respectively. As for the troposphere in the same region, ozone shows an increase ( 1.5 %/year) in the mid-troposphere but temperature trends are insignificant over the first period, versus no ozone trend but a clearly significant near-surface warming (-0.2 K/year) in the second period. This average situation is however not representative for the separate regions it is composed of, i.e., Canada (4 stations), Japan (3 stations) and the U.S. (1 station). Above Syowa station at the Antarctic coast, the acceleration in stratospheric ozone depletion as well as stratospheric cooling over the past two decades is clearly evident: from hardly significant ozone and temperature trends in the first period to values ofup to -4 %/year and -0.4 K/year respectively in the second period. In regions where nearsurface ozone increase is evident over the past two decades, it is often accompanied by a significant near-surface warming. L INTRODUCTIONMost general circulation models (GCM's) currently use a prescribed ozone distribution for the calculation of radiative heating rates. Ideally this distribution should be a function of latitude, longitude, height and time. However, none of the observed ozone data provide the required spatial and temporal coverage for this. One commonly used dataset, the CIRA ozone reference 910hI was compiled using data from five different satellite instruments (LIMS, SBUV, AE-2 SAGE, SME-UVS and SME-IR), retrieving ozone profiles between 20 to 0.003 hPa (24 levels) from November 1978 to December 1983. An improved version of the CIRA model, including data on 3 additional pressure levels: 30, 50 and 70 hPa (Keating, personal communication), and extended to high latitudes in the polar night (after Shine, personal communication), is currently being used in the Berlin tropo-strato-mesospheric GCM. Use ofthis climatology results in a fairly realistic vertical temperature structure in the stratosphere and mesosphere.2' Up to now, satellite instruments are not capable ofmeasuring ozone in the troposphere and near the tropopause, where the climate forcing and radiative heating rates are very sensitive to the assumed ozone distribution.6'20 In order to overcome this deficit, an attempt is made to construct...