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RESEARCH PRODUCT

Meteorological considerations of grapevine damage due to temperature variations: the 2019 late spring frost and summer heat wave events in Burgundy.

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<p><strong><span>Meteorological considerations of grapevine damage due to temperature variations:</span> <span>t</span><span>he 2019 late spring frost and summer heat wave events </span>in Burgundy </strong></p><p>During 2019, <span>the occurrence of two contrasting weather events, a cold snap and a heat wave, caused extensive damage to the vineyards</span> of Northern Burgundy. <span>The late spring cold snap, that </span><span>occurred</span><span> from May 5</span><sup><span>th</span></sup><span> to 7</span><sup><span>th</span></sup><span>, generated frost like conditions across the northern and north-western areas of the Côte-d'Or department.</span> The weather stations of the Northern Auxois area, where the three observation and study sites are located, recorded minimum temperatures <span>ranging </span>between -1 and -2°C. <span>On the 24</span><sup><span>th</span></sup><span> and the 25</span><sup><span>th</span></sup><span> of July vineyards were exposed, yet again, to an extreme temperature variation.</span> <span>A brief but unusually intense heat wave increased daily maximum temperatures up to 42°C in the department’s far north. Landforms such as plateaus were less exposed to the increase in temperatures due the limiting effect of higher elevations. This led to temperatures not exceeding 40°C above 300 m, elevation at which the vineyard sites of this study are located.</span></p><p>Weather conditions that caused the early May frost event were related to a northern circulation <span>present </span>over Western Europe <span>that persisted </span>from <span>the 28</span><sup><span>th</span></sup><span> of April </span><span>to</span><span> the 6</span><sup><span>th</span></sup><span> of May</span>. <span>The strong anticyclonic ridge stretching from Greenland to the Iberian Peninsula directed an air mass of arctic origin towards France.</span> <span>On July 24</span><sup><span>th</span></sup><span> and 25</span><sup><span>th</span></sup><span>, the presence of a surface high pressure system above Scandinavia, associated with a low-pressure center located near the Atlantic Ocean, generated an influx of a very hot air mass from the northern part of the African continent through France and neighbouring countries.</span></p><p>The local impact of these two weather events was modulated by the topographical features specific to the study area: a limestone plateau strongly dissected by parallel valleys <span>of S.E. / N.W. orientations</span>. <span>The three observation sites have similar soil characteristics and are located on south facing slopes.</span> <span>However, damage to vegetation was uneven across sites as well as within each site.</span> These observations rise up the question of the influence of very fine-scale environmental conditions <span>and the impact they might have on the different vegetative growth stages.</span> <span>Lastly, the variation in physiological response among grapevines and its effect on their sensitivity to the occurrence of different weather hazards is also to be considered.</span></p>