O. M. Evtushevsky

Decadal variability of winter temperatures in the Antarctic Peninsula region

Abstract Rapid climate warming has been observed in the region of the Antarctic Peninsula since the middle of the last century with the largest warming rate in the winter. Decadal variability of winter temperature on the regional scale was analysed using eight station datasets of the Antarctic Peninsula region. The Scientific Committee on Antarctic Research Reference Antarctic Data for Environmental Research from the period 1950–2009 were used. Fourier and wavelet transforms of the averaged temperature anomaly time series reveal a clear separation between the oscillations with three to eight year periods and a decadal oscillation with a period of around 16 years. On the Antarctic Peninsula region scale, 16 year periodicity in the winter temperature variability has not been described before. Both spectral components show similar spectral power and statistical significance (5–10%). This is evidence of their comparable importance for winter temperature changes in the Antarctic Peninsula region. The three to eight year periods are most probably related to the El Niño–Southern Oscillation and Antarctic Circumpolar Wave signals, but the 16 year oscillation has not been identified within the scope of this analysis. The possible effect of the decadal oscillation in the winter temperature trend estimate is discussed.

On the regional distinctions in annual cycle of total ozone in the northern midlatitudes

To better attribute the total ozone column (TOC) anomalies observed from the ozone measurements in Ukraine, the climatologies of annual ozone cycle along the latitudinal band 40–60° N with the 30° step in longitude have been analysed. Gridded satellite ozone data based on the merged ozone dataset over the period 1979–2011 are used. The results show that, similar to the known longitudinal dependences of both the total ozone itself and its decadal trends, the annual TOC cycle in the northern midlatitudes is also longitudinally dependent. The higher (lower) regional TOC level is associated with the leading (lagging) development of the annual cycle relative to the zonal mean climatology. Particularly, a 2- to 3-month lead of annual cycle in eastern Asia (120–150° E) in comparison with that in eastern Atlantic (0–30° W) exists. Revealed coupling between regionality and seasonality of the TOC in the northern midlatitudes may be involved in the regional climate variability and deserves further studies with higher temporal and spatial resolution.

Comparison of ground-based Dobson and satellite EP-TOMS total ozone measurements over Vernadsky station, Antarctica, 1996-2005

Total ozone content derived from version 8 of the Earth Probe Total Ozone Mapping Spectrometer (EP‐TOMS) satellite data was compared with that from ground‐based data obtained with the Dobson spectrophotometer no. 031 at the Ukrainian Antarctic Vernadsky station. The period of comparison is 1996–2005. The statistics for cloudy and clear sky observations are presented separately, in order to assess the influence of cloudiness on the difference between the satellite and ground‐based measurements. The main findings obtained from the TOMS–Dobson difference analysis were: (i) a significant disagreement between clear and cloudy sky differences of about 9%, which is almost the same value as in version 7; and (ii) the difference for all data equals −2.0% (2625 days), whereas in cloudless and cloudy conditions the difference is 4.1% (137 days) and −4.5% (1048 days), respectively. We conclude that the TOMS (Dobson) measurements are mostly responsible for the data disagreement in clear (cloudy) sky conditions.

Troposphere and stratosphere influence on tropopause in the polar regions during winter and spring

Arctic and Antarctic tropopause is formed under unique climate conditions, both in the troposphere and stratosphere. Individual patterns of polar tropopause anomalies are formed under dominance or competition of the tropospheric and stratospheric sources. We analyse the thermal tropopause climatology in the polar regions using National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP–NCAR) Reanalysis-1 data between 1979 and 2008. The role of the troposphere and stratosphere in tropopause anomaly distribution is examined using corresponding temperature and geopotential height fields. By location, the tropopause anomalies in the Arctic and Antarctic are closer to patterns of cold anomalies in the troposphere and stratosphere respectively. Results indicate that the 30-year climatological tropopause anomalies in polar winter and spring could have different relationships to troposphere and stratosphere influences, even in neighbouring parts of the polar atmosphere.

Decadal changes in the central tropical Pacific teleconnection to the Southern Hemisphere extratropics

Decadal changes in the teleconnection between the central tropical Pacific and the Southern Hemisphere extratropics are studied using the NCEP–NCAR reanalysis data. Concurrent and lagged relationships show that teleconnection strength in austral spring was weak (strong) before (after) 1996/1997. This decadal change coincides in time with the climate regime shift in the Pacific in the 1990s known from many studies. We show that, after the regime shift, the concurrent and delayed teleconnection with the Southern Hemisphere extratropics is insignificant in September and abruptly increases in October. Penetration of the stratospheric anomaly into the troposphere in October can indicate interacting tropospheric and stratospheric pathways of the teleconnection to strongly enhance the central tropical Pacific impact since the late 1990s. The results give evidence that the Southern Annular Mode seems to be connecting element between the two pathways in the recent decades. The common tendencies in the eastward shift of the tropical anomalies and zonal wave 1 phase in the Antarctic stratosphere in austral spring have been demonstrated. The difference between the central Pacific and eastern Pacific teleconnections is consistent with that known from previous studies and new tendencies in their decadal changes and delayed effects have been revealed. It has been found that the central Pacific contributions to the Pacific decadal oscillation and to the Northern Hemisphere stratosphere have also increased significantly after the 1990s. This characterizes the central tropical Pacific as one of the key regions impacting climate and teleconnection not only in the Southern Hemisphere, but also in the Northern Hemisphere. Our findings are consistent with and further develop the recent studies of the stratosphere–troposphere coupling in austral spring, and emphasize significant contribution of the delayed tropical signals to the climate variability in austral spring in both hemispheres.