Terroir 2020 banner
IVES 9 IVES Conference Series 9 Unprecedented rainfall in northern Portugal

Unprecedented rainfall in northern Portugal

Abstract

Aim: Climate is arguably one of the most important factors determining the quality of wine from any given grapevine variety. High rainfall during spring can promote growth of the vines but increases the risk of fungal disease, while vineyard operations can be disrupted, as machinery may be prevented from getting in the vineyard owing to muddy soils. Conversely, high rainfall during harvest time (August to October) also bears the potential for severe operational disruption and heavy economic losses. To date, the probability of unprecedented rainfall amounts in spring and the harvest season has not been assessed over northern Portugal, specifically the three wine-growing regions of Vinho Verde, Trás-os-Montes and Porto and Douro DOC. In a situation of higher climatic variability, establishing the probable limits of rainfall variation during critical moments of the vine growth cycle will allow for better readiness of farmers as well as higher resilience of the whole value chain.

Methods and Results: Observed rainfall totals for northern Portugal were extracted from version 21 of the E-OBS dataset. Monthly rainfall totals were archived from a series of 16 month-long hindcasts produced with the Met Office’s decadal prediction system DePreSys3. These hindcasts begin in November of each year, corresponding to the start of each viticultural campaign. The hindcasts are produced from 1980 to 2017, when satellite data are available for model initialisation. Forty ensemble members are available for each start time, providing 1520 (38 × 40) simulations of spring and late summer rainfall totals. The hindcast and observed rainfall totals are considered indistinguishable if the mean, standard deviation, skewness and kurtosis from the observations are within the respective 2.5th–97.5th percentile ranges from 10,000 model bootstraps. It was necessary to shift the modelled mean for spring rainfall owing to a wet bias in the simulations. The model results showed there was a probability of 0.02 ± 0.01 of an unprecedented rainfall event in spring and summer. However, the chance of another year with an exceptionally wet spring and late summer (as happened in 1993) is extremely small.

Conclusions: 

Rainfall totals in northern Portugal over the past 38 years have been very high in a few years, but higher values are possible in the current climate. The chance of another year similar to 1993, when both seasons were exceptionally wet, is very low. The uncertainty in extreme rainfall estimates is considerably reduced when the modelled data are used. A year with rainfall equal to the highest observed amounts in one of these two seasons could be expected to occur just once in the next 30-100 years.

Significance and Impact of the Study: This study is the first to assess the probability of unprecedented rainfall extremes over northern Portugal, allowing for a better estimate of the inherent risk. The results help inform the need for costly adaptation investments, such as better availability of spraying machinery and labour, high-gauge drainage, landslide controls or even abandonment of exposed vineyard areas.

DOI:

Publication date: March 17, 2021

Issue: Terroir 2020

Type: Video

Authors

Michael G. Sanderson1*, Marta Teixeira2, Natacha Fontes2, Sara Silva2, António Graça2

1Met Office, Fitzroy Road, Exeter, EX1 3PB, United Kingdom
2Sogrape Vinhos, S.A., Aldeia nova, 4430-809 Avintes, Portugal

Contact the author

Tags

IVES Conference Series | Terroir 2020

Citation

Related articles…

Late frost protection in Champagne

Probably one of the most counterintuitive impacts of climate change on vine is the increased frequency of late frost. Champagne, due to its septentrional position is historically and regularly affected by this meteorological hazard. Champagne has therefore developed a strong experience in frost protection with first experiments dating from the end of 19th century. Frost protection can be divided in two parts: passive and active. Passive protection includes all the methods that do not seek to modify the vine’s environment or resistance at the time of frost. The most iconic passive protection in Champagne is the establishment of the individual reserve. This reserve allows to stock a certain quantity of clear wine during a surplus year to compensate a meteorological hazard like frost during the following years. Other common passive methods are the control of planting area (walls, bushes, topography), the choice of grape variety, late pruning, or the impact of grass cover and tillage. Active frost protection is also divided in two parts. Most of the existing techniques tend to modify vine’s environment. Most of the time they provide warmth (candles, heaters, windmills, heating cables…), or stabilise bud’s temperature above a lethal threshold (water sprinkling). The other way to actively fight is to enhance the resistance of buds to frost (elicitors). The Comité Champagne evaluates frost protection methods following three main axes: the efficiency, the profitability, and the environmental impact through a lifecycle assessment. This study will present the results on both passive and active protection following these three axes.

Analysis of some environmental factors and cultural practices that affect the production and quality of the Manto Negro, Callet and Prensal Blanc varieties

45 non irrigated vineyards distributed in the DO (Denomination) Pla i Llevant de Mallorca and the DO Binissalem Mallorca were used to investigate the characteristics of production and quality and their relationships certain environmental factors and cultural practices. The grape varieties investigated are autochthonous to the island of Mallorca, Manto Negro and Callet as red and Prensal Blanc as white. All plants were measured for four consecutive years in the main production and quality parameters. Among the environmental factors, the type of soil has been studied, more specifically its water retention capacity, the planting density, the age of the vineyard and the level of viral infection. The presence or absence of virus seems to have no effect on any component studied in the varieties studied. For the white variety Prensal Blanc age is negatively correlated with production and the number of bunches, nevertheless it does not cause any effect on the required quality parameters. However, for the red varieties Callet and Manto Negro, the age of the plantation is the variable that best correlates with the quality parameters, therefore the old vines should be the object of preservation by the viticulturists and winemakers in order to guarantee its contribution to the quality of the wines made with these varieties.

Climate, Viticulture, and Wine … my how things have changed!

The planet is warmer than at any time in our recorded past and increasing greenhouse emissions and persistence in the climate system means that continued warming is highly likely. Climate change has already altered the basic framework of growing grapes for wine production worldwide and will likely continue to do so for years to come. The wine sector can continue to play an important role in leading the agricultural sector in addressing climate change. From developing on…

How does aromatic composition of red wines, resulting from varieties adapted to climate change, modulate fruity aroma?

One of the major issues for the wine sector is the impact of climate change linked to the increasing temperatures which affects physicochemical parameters of the grape varieties planted in Bordeaux vineyard and consequently, the quality of wine. In some varietals, the attenuation of their fresh fruity character is accompanied by the accentuation of dried-fruit notes [1]. As a new adaptive strategy on climate change, some winegrowers have initiated changes in the Bordeaux blend of vine varieties [2]. This study intends to explore the fruitiness in wines produced from grape varieties adapted to the future climate of Bordeaux. 10 commercial single–varietal wines from 2018 vintage made from the main grape varieties in the Bordeaux region (Cabernet franc, Cabernet-Sauvignon and Merlot) as well as from indigenous grape varieties from the Mediterranean basin, such as Cyprus (Yiannoudin), France (Syrah), Greece (Agiorgitiko and Xinomavro), Portugal (Touriga Nacional) and Spain (Garnacha and Tempranillo), were selected among 19 samples using sensory descriptive analyses. Both sensory and instrumental analyses were coupled, to investigate their fruity aroma expression. For sensory analysis, samples were prepared from wine, using a semi preparative HPLC method which preserves wine aroma and isolates fruity characteristics in 25 specific fractions [3,4]. Fractions of interest with intense fruity aromas were sensorially selected for each wine by a trained panel and mixed with ethanol and microfiltered water to obtain fruity aromatic reconstitutions (FAR) [5]. A free sorting task was applied to categorize FAR according to their similarities or dissimilarities, and different clusters were highlighted. Instrumental analysis of the different FAR and wines demonstrated variations in their molecular composition. Results obtained from sensory and gas chromatography analysis enrich the knowledge of the fruity expression of red wines from “new” grape varieties opening up new perspectives in wine technology, including blending, thus providing new tools for producers.

The plantation frame as a measure of adaptation to climate change

The mechanization of vineyard work originally led to a reduction in planting densities due to the lack of machinery adapted to the vineyard. The current availability of specific machinery makes it possible to establish higher planting densities. In this work, three planting densities (1.40×0.80 m, 1.80×1 m and 2.20×1.20 m, corresponding to 8928, 5555 and 3787 plants/ha respectively) were studied with four varieties autochthonous of Galicia (northwestern Spain): Albariño and Treixadura (white), Sousón and Mencía (red). The vines were trained in a vertical shoot positioning system using a single Royat cordon, and pruned to spurs with two buds each. Agronomic data (yield, pruning wood weight, Ravaz index) and oenological data in must were collected. The higher planting density (1.40×0.80 m) had no significant effect on grape yield per vine in white varieties, although production per hectare was much higher due to the greater number of plants. In red varieties, this planting density resulted in a significantly lower production per vine, compensated by the greater number of plants. In addition, it significantly reduced the Brix degree in the must of the Albariño, Treixadura and Sousón varieties, and increased the total acidity in the latter two and Mencía. It also caused an increase in extractable and total anthocyanins and IPT in red grapes. The effects of high planting density on grapes are of great interest for the adaptation of varieties in the context of climate change. In the future, it could be advisable to modify the limits imposed by the appellations of origin on the planting density of these varieties in order to obtain more balanced wines.