The specific climatological conditions that characterise vine-growing in the Ribera del Duero have a great influence throughout the vegetative cycle of the vines, playing a fundamental role in the development of the plant and ripening of the grape. To a great extent, the quality of the drinks obtained depends on those special conditions.
The climate of the Ribera del Duero area is characterised in broad terms by moderate to low rainfall (400-600 mm average annual rain) that, together with its dry summers and long, rigorous winters and sudden temperature changes throughout the year, is of a Mediterranean type whose primordial feature is continentality.
The temperature and the water availability are the most important climatic elements for the development of the vine.
A long period of mild temperatures is needed to obtain the maturity. The metabolic development of the vineyard starts with temperatures over the 10 ºC and the photosynthesis occurs with average temperatures of 15 ºC and 30 ºC. A significant difference between the temperature on summer and winter allows the vineyard to rest. With temperatures over 35 ºC, the plant stops the ripening process and the winter frosts below -15 ºC can kill it. The variation between a high temperature and a low temperature during the day (diurnal temperature variation) significantly affects the ripening of the grapes. If the variation is low, the grapes will lack acidity, however, if the difference is big, the grapes will be well-balanced and retain acidity.
Moreover, it is important to know that with each 100 metres above sea level, the average temperature reduces approximately 0.6 ºC. Likewise, growing vines in a hill with certain orientations reduces the sun exposure of the vineyard (the sunstroke is another key element because it is the motor of the photosynthesis).
The orientation of the vineyard and the vine rows, as well as their separation, the different pruning systems and the control of the leaf area to increase or reduce the exposure or aeration of the clusters are key points to optimise the sunlight effect. Decisions related to these elements will depend on the varieties, because each one has different patterns of vigour and growth.
For the vine, the main concern of the precipitations is not the volume (there are great vine-growing areas with very low or high precipitations), but the moment of the vegetative cycle in which they are produced. Winter rains help to create reserves, if they occur at the beginning of the cycle it can affect the size of the harvest but if they occur at the end, it can influence the quality, because rain dilute sugars and acids, in addition to break the aromatic balance of the grapes. The most feared consequence of the rain is the risk of fungal disease that can expand quickly through the vineyard, ruining the harvest.
In some areas, autumn rains are produced. The only uncertainty is when they will occur. So, each year viticulturists must take the risk of deciding between a higher ripening or the possibility of having the harvest ruin due to the rain. The grapes grown in vineyards with cooler climates and longer maturations, have more interesting and complex aromas, which will be present in the wines. Even though it is very difficult to obtain a complete ripening, the places where the most interesting wines come are located in areas with marginal climates for the varieties that have been grown in their vineyards.
Since the different varieties have different rhythms of maturation, it is very important for the viticulturist to decide which variety he will grow on the vineyard. In all climates there are varieties that ripen easier than others. Besides, some varieties are more resistant to extreme weather where they have been grown. The range of the average temperature in which some varieties ripen is wider than in other varieties. Several varieties only reach the optimal ripening in a small range of temperature.
AVERAGE TEMPERATURES AND PRECIPITATIONS
The ‘average daily high’ (continuous blue line) shows the average of the maximum temperature of one day per month. Likewise, the ‘average daily low’ (continuous blue line) shows the average of the minimum temperature. Hot days and cold nights (discontinuous red and blue lines) show the average of the hottest day and the coldest night of each month on the last 30 years.
The diagram of the maximum temperature at Trus show how many days per month certain temperatures are reached.
CLOUDY SKY, SUN AND DAYS OF PRECIPITATION
The graphic shows the number of sunny, partly cloudy, cloudy days or with precipitations per month. Days with less than 20% of cloud cover are considered sunny days, with 20%-80% of cloud cover are partly cloudy days and over 80% are cloudy days.
AMOUNT OF PRECIPITATION
The diagram of precipitation for Trus shows how many days per month certain amounts of precipitation are reached.
The diagram of Trus shows the days per month where the wind reaches a certain speed.
The wind rose for Trus shows the number of hours per year the wind blows at a particular location.