Export citation and abstract BibTeX RIS
Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Due to a mistake in the calculation of the warm spell duration index (WSDI) and cold spell duration index (CSDI) for the ERAInterim data, the magnitudes of the trends presented in our study are too small. Both indices were calculated using daily mean temperatures instead of daily minimum (for CSDI) and daily maximum (for WSDI) temperatures in comparison with the percentiles TN10 (for CSDI) and TX90 (for WSDI), which leads to much smaller values for the indices and therefore smaller trends. We corrected the calculation and plotted figure 1 again. The most prominent changes occur for warm spell duration index in summer. However, the main results and conclusions of our study are not affected by the error.
Figure 1. Trends in cold spell days (CSDI; top row) and warm spell days (WSDI; bottom row) for winter (left column) and summer (right column) over the time period 1979–2013. Colored circles show results from GSOD station data, associated color-coding is explained in the top color bar. Shading shows results from ERA-Interim data, associated color-coding is explained in the bottom color bar. For both color bars the numbers on the top refer to CSDI, numbers on the bottom refer to WSDI. Stations with trends found significant at the 95% confidence level are marked with a black circle around the colored station circle, while significant trends from ERA-Interim are marked with black dots. Only stations with a data coverage of at least 5 years within 1979–1995 and at least 5 years within 1996–2013 are used for this figure (see section 2.3).
Download figure:
Standard image High-resolution image
3. Results
3.1. Spatial patterns of trends in spells
3.1.1. Warm spells (WSDI)
The paragraph on the spatial patterns of warm spell duration index (WSDI) should read: ERA-Interim data-derived trends (shading in figure 1(d)) suggest that warm spells have changed most noticeably over Greenland (up to 4 days/decade). The station-derived (colored circles in figure 1(d)) significant positive trends indicating an increase of warm spells over southern Siberia are reproduced by ERA-Interim, in contrast to the significant positive station based trends over Scandinavia. Both data sets indicate an increase in warm spells over western Russia and parts of the Canadian Archipelago.