## 1 Introduction
It has been shown that water limitation affects plant hormonal equilibrium directing sugar accumulation in grape berries. Furthermore, in irrigated conditions, total soluble solidsconcentration can decrease due to the dilution caused by greater berry size [17], but enhanced sugar accumulation associated with higher photosynthetic activity also occurs under irrigation [22]. Although the mechanisms of phenolic biosynthesis at high temperatures are still poorly understood, the optimum temperature for phenolic accumulation is nearly 25 \({}^{\circ}\)C, while above or below this level accumulation tends to fall significantly [20]. The effect of temperature on grape berry anthocyanins content has been studied for different varieties and regions [13; 14; 23; 24]. For instance, mature berries from Cabernet Sauvignon, Shiraz and Chardonnay varieties cultivated in cooler sites accumulate higher levels of anthocyanins than those from warmer climates [14]. High temperatures can reduce anthocyanins accumulation through either the impairment of its synthesis or the acceleration of its degradation [25]. In the berry skin of Darkridge (_Vitis vinifera_ L. \(\times\)_Vitis labrusca_ L.), two enzymes of the anthocyanins biosynthetic pathway were favoured by cool night temperatures [21]. In water stress conditions, phenolic compounds, including anthocyanins, are concentrated due to berry size reduction. In addition, the biosynthesis of each phenolic compound is differently affected by the severity of the water deficit and the period when it occurs [26]. Water deficits during veraison and maturation increase anthocyanin [26; 27; 28], proanthocyanin and flavonoid biosynthesis [26], while early in the growing season high water availability is beneficial for anthocyanins content, as it promotes vegetative growth and, consequently, berry development and composition at later stages [29]. However, other reports show that high moisture availability late in the growing season may reduce anthocyanins content [30]. Previous studies already demonstrated the role of some climatic variables in grape berry quality parameters [7; 13; 14; 31; 32], some of them using long-term historical data for a few variables [7]. To our knowledge, this is the only study that uses a long-time series of biochemical data in field conditions, for many berry quality aspects (berry weight, titratable acidity, pH, potential alcohol, anthocyanins and TPI): maximum of 19 years for Douro region (1999-2017) and a minimum of six years for Alentejo region (2012-2017). Moreover, this study is unprecedented in Portugal, being the first to assess the climate-berry quality relationships using several grape berry quality parameters and over such a long time period. Portuguese wine production is characterized by a strong interannual variability, which is a feature of Mediterranean climates, with adverse consequences for wine business [33]. Therefore, it is of great interest for the wine industry to understand the role of atmospheric variability on grape berry composition to develop and implement optimized agronomic/oenological strategies, such as stress mitigation agronomic practices while reducing water, fertilizers and pesticides usage. The identification of cause-effect relationships will set the grounds for the development of predictive models of grapevine quality and decision support tools that can be used either to monitor grapevine development, in the short-term, or to assess the potential impacts of climate change, in the long-term [34]. Hence, the present study aims to determine the responses of some key berry attributes to atmospheric variability, namely berry weight, titratable acidity (TA), pH, potential alcohol (PA), anthocyanins and total phenols index (TPI). The study was carried out for three Portuguese wine regions (Douro, Dao and Alentejo) and two major grapevine varieties: cv. Touriga Nacional (TON, PRT52206) and cv. Aragonez (ARA, PRT52603, International synonym Tempranillo).