Weather reconstruction and application for Switzerland: Long-term changes of spring weather impacts since 1763

<p class="western">Numerous historical sources report on hazardous past climate and weather events that had considerable impacts on society. Studying <span lang="en-US">changes in their occurrence or </span> mechanisms <span lang="en-US">behind</span> such events is however hampered by a lack of spatial weather information. For Switzerland, we <span lang="en-US">created</span> a daily high-resolution (1x1 km²) reconstruction of temperature and precipitation fields for the years 1763 to 1960 using <span lang="en-US">an</span> analog resampling method based on observational data. The resampled fields are further post-processed by assimilating temperature observations and quantile mapping the precipitation fields. Together with the present-day meteorological fields, this forms a more than 250-year long gridded data set.</p> <p class="western"><span lang="en-US">W</span><span lang="en-US">e use this data set to evaluate</span> changes in spring weather impacts over the last 250 years. The spring season receives <span lang="en-US">fewer</span> attention since it has no extreme events in absolute terms. However, it is relevant <span lang="en-US">since weather conditions in spring can delay vegetation onset and growth, and can create substantial vegetation damages due to for example late frost and snow events</span>. We evaluate therefore the long-term <span lang="en-US">changes</span> of spring fresh snow days, late frost days, frost days, and warm days, and compare it to changes of spring <span lang="en-US">onset</span> and <span lang="en-US">reconstructed </span>phenological stages.</p>