Vines (Vitis Vinifera) are Mediterranean plants. This means that the perfect weather for vine is Mediterranean weather while under Atlantic weather it’s a plant out of the optimum developement conditions.
Weather facts influence:
The optimum temperatura for photosynthesis is around 28ºC. Between 25ºC to 30ºC the plants are really efficient producing sugars from photosynthesis metabolism. This temperature range is typical from Mediterranean weather while Atlantic temperature are lower. Sugars during fermentation are transformed into alcohol so it’s typical higher alcohol in Mediterranean wines tan Atlantic ones. Another aspect related is the slower maturation under Atlantic weather conditions. This means later harvests, Autum harvest. Vitis Vinifera is a Summer maturation plant. Harvest should be at the end of Summer or early Autum. Today harvest in Mediterranean areas ussually is made around August while traditionally it was in September/October. This is well know by Mediterranean viticultors that are actually looking for higher lands to plant vineyards in fresher places.
Other effect related with temperature is the acids reduction, specialy Malic acid that is directly proportional consumed with higher temperatures. Atlantic wines keep more acidity and freshness tan Mediterranean ones.
With the balance of sugars and acids is defined the “industrial ripeness index”. The other two index that define maturation are “aromatic ripeness index” (showing aromatic compounds o aromatic precursor compounds ripeness) and “phenolic ripeness index” (indicating tannins and colour ripeness). This three maturation index define the optimum harvest momento for each grape variety and if al lof them appear at teh same moment this is the definition of perfect adpatation for a grape variety to a weather or in a more general way… to a terroir. Today, it’s easier to find this situation of coincidence in the three different maturation index in Atlantic weather while in Mediterranean weather is more anticipated the industrial maturity thanks to the temperature influence in the sugars production.
Sunlight is another of the imputs might limitate photosynthesis, in Atlantic weather conditions as the temperatures are lower it becomes in a really important aspect to care about. In Atlantic weather, in general, more sunlight… better!
Water status (rain or irrigation)
It isn’t a limitation in Atlantic weathers in terms of water status for the plant hydratation and the most important influence is that the rain and in general, humidity, helps the funghi diseases development. In Atlantic viticulture conditions is really important to pay atention to the funghi diseases control, the risk is much bigger tan in Mediterranean conditions.
It isn’t a discusión of better or worse wines, just different… but IMHO, today Atlantic areas, or higher altitude lands, represent an “unconfortable zone” for Vitis Vinifera that is really interesting to get more exciting wines, different ones, with higher identity… while in the “confort zone” wines tend to be more predictables and boring.