Atmospheric reanalyses were validated against tethersonde sounding data on air temperature, air humidity and wind speed, collected during the drifting ice station Tara in the central Arctic in April–August 2007. The data were not assimilated into the reanalyses, providing a rare possibility for their independent validation, which was here made for the lowermost 890 m layer. The following reanalyses were included in the study: the European ERA‐Interim, the Japanese JCDAS, and the U.S. NCEP‐CFSR, NCEP‐DOE, and NASA‐MERRA. All reanalyses included large errors. ERA‐Interim was ranked first; it outperformed the other reanalyses in the bias and root‐mean‐square‐error (RMSE) for air temperature as well as in the bias, RMSE, and correlation coefficient for the wind speed. ERA‐Interim suffered, however, from a warm bias of up to 2°C in the lowermost 400 m layer and a moist bias of 0.3 to 0.5 g kg−1throughout the 890 m layer. The NCEP‐CFSR, NCEP‐DOE, and NASA‐MERRA reanalyses outperformed the other reanalyses with respect to 2‐m air temperature and specific humidity and 10‐m wind speed, which makes them, especially NCEP‐CSFR, better in providing turbulent flux forcing for sea ice models. Considering the whole vertical profile, however, the older NCEP‐DOE got the second highest overall ranking, being better than the new NCEP‐CFSR. Considering the whole group of reanalyses, the largest air temperature errors surprisingly occurred during higher‐than‐average wind speeds. The observed biases in temperature, humidity, and wind speed were in many cases comparable or even larger than the climatological trends during the latest decades.

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Changes in the frequency and air pressure of cyclones that enter or are formed within the Arctic basin are herein examined by applying the database of cyclones created using NCEP/NCAR re-analysis. The Arctic basin is defined as the area north of latitude 68 • N. Deep cyclones with a mean sea level pressure (SLP) of below 1,000 hPa, were analysed separately from shallow cyclones. Changes in the variables in the first, last, deepest and northernmost points of cyclones were studied. The cyclones were grouped into sectors by using the point on latitude 68 • N at which the cyclone entered the Arctic region. The analysis described herein shows that the frequency of incoming cyclones, i.e. those that entered the Arctic basin, increased significantly during the period 1948-2002, but that the frequency of Arctic cyclones formed within the Arctic basin did not. The frequency of deep cyclones that entered the Arctic basin, as well as the frequency of cyclones that formed within it, clearly increased, while the frequency of shallow Arctic cyclones decreased. The most significant changes in the seasonal parameters associated with the cyclones occurred in winter. The mean annual SLP of deep cyclones decreased significantly, particularly for deep Arctic cyclones. The frequency of incoming cyclones showed an increase in the Bering Strait, Alaskan, Baffin Sea, and East Siberian sectors.

Meteorological observations were made at the drifting ice station Tara in the central Arctic Ocean from 23 March to 19 September 2007, constituting a unique data set from the season preceding the record‐low sea ice extent. Comparisons of the Tara data with observations at the Russian drifting ice stations in 1937–1938 and 1950–1991 and at SHEBA in 1998 indicated that at Tara and SHEBA the atmospheric transmissivity for shortwave radiation was smaller than at the Russian stations, suggesting a higher cloud fraction or optical thickness. Compared to the mean conditions at the Russian stations, at Tara the melting season was twice as long and in April the 2‐m air temperature was 7.0°C higher, but in July the 2‐m temperature difference disappeared. The Tara tethersonde sounding data suggest that the air temperature at the altitudes of 200–1000 m was approximately 1°C higher than the mean of 1954–1985.

Air temperature and specific humidity inversions and low-level jets were studied over two Svalbard fjords, Isfjorden and Kongsfjorden, applying three tethersonde systems. Tethersonde operation practices notably affected observations on inversion and jet properties. The inversion strength and depth were strongly affected by weather conditions at the 850 hPa level. Strong inversions were deep with a highly elevated base, and the strongest ones occurred in warm air mass. Unexpectedly, downward longwave radiation measured at the sounding site did not correlate with the inversion properties. Temperature inversions had lower base and top heights than humidity inversions, the former due to surface cooling and the latter due to adiabatic cooling with height. Most low-level jets were related to katabatic winds. Over the ice-covered Kongsfjorden, jets were lifted above a cold-air pool on the fjord; the jet core was located highest when the snow surface was coldest. At the ice-free Isfjorden, jets were located lower.