How different sources of climate databases influence assessment of growth response in dendroclimatic analyses - case study from Lapland

The paper deals with the comparison of the time series from different climate databases. We compared the measured data with the modelled data of monthly and seasonal temperature means and precipitation totals. Reliable and as long as possible time series of such data represent the basic starting point of dendroclimatic analyses. We evaluated the differences in the growth response of spruce derived using different databases of the stated climatic characteristics. The stem cores used to derive the cross-correlation function were taken from Hårås locality situated in the boreal zone of the Swedish part of Lapland. We compared the measured records from the nearest meteorological stations situated 18 and 40 km away from the locality with the interpolated values from CRU TS 3.21 climate database and with the reconstructed 502-year-long database. The spatial resolution of the modelled databases was 0.5° × 0.5° of latitude and longitude. We found a systematic error of different magnitudes in the modelled values, and we also quantified a random error and the overall accuracy of the data. The temperature model underestimated the data in comparison with the measured values, while the precipitation model overestimated the data. We also found that the radial increments of spruce correlated more strongly with the temperature than with the precipitation. Hence, in the conditions of the boreal zone, temperature is a more important factor affecting tree-ring formation. We found significantly higher correlations between the radial increment and the modelled precipitation data than with the data measured at the precipitation station situated 18 km from the locality of interest.