Climate impacts on vines in the upper Douro valley: Cold air pooling and unprecedented rainfall

Abstract

Climate is arguably one of the most important factors determining the quality of wine from any given grapevine variety. This study focuses on climate impacts on vines in the upper Douro Valley, which is one of the most important viticultural regions of northern Portugal. Two different phenomena are studied: cold air pooling and unprecedented rainfall totals. Cold-air pools can have several different impacts on viticulture, including timing of budbreak, final grape quality and yields. Cold pools were studied using high time resolution data from two weather stations located in the upper Douro valley. High rainfall during late spring (April to June) can promote growth of the vines but increases the risk of fungal disease. High rainfall during harvest time (August to October) also bears the potential for severe operational disruption and heavy economic losses. The probability of unprecedented rainfall totals in spring and the harvest season over wine-growing regions of northern Portugal has been assessed using an ensemble of decadal hindcasts and three different gridded precipitation datasets. The probability of a precipitation event with unprecedented totals was low (less than 0.04), although such an event would be highly damaging to the vines. A year similar to 1993, when both seasons were exceptionally wet, would be expected to occur, on average, just once in the next 70-80 years in the current climate.