Climate Projections for Precipitation and Temperature Indicators in the Douro Wine Region: The Importance of Bias Correction

Abstract

The implications of weather and climate extremes on the viticulture and winemaking sector can be particularly detrimental and acquire more relevance under a climate change context. A four-member ensemble of the Regional Climate Model-Global Climate Model chain simulations is used to evaluate the potential impacts of climate change on indices of extreme temperature and precipitation, as well as on agroclimatic indices of viticultural suitability in the Douro Wine Region, Portugal, under current and future climate conditions, following the RCP8.5 anthropogenic radiative forcing scenario. Historical (1989–2005) and future (2051–2080) periods are considered for this purpose. Although model outputs are bias-corrected to improve the accuracy of the results, owing to the sensitivity of the climatic indicators to the specific bias correction method, the performance of the linear and quantile mapping methods are compared. The results hint at the importance of choosing the most accurate method (quantile mapping), not only in replicating extremes events but also in reproducing the accumulated agroclimatic indices. Significant differences between the bias correction methods are indeed found for the number of extremely warm days (maximum temperature > 35 °C), number of warm spells, number of warm spell days, number of consecutive dry days, the Dryness Index, and growing season precipitation. The Huglin Index reveals lower sensitivity, thus being more robust to the choice of the method. Hence, an unsuitable bias correction method may hinder the accuracy of climate change projections in studies heavily relying on derived extreme indices and agroclimatic indicators, such as in viticulture. Regarding the climate change signal, significant warming and drying trends are projected throughout the target region, which is supported by previous studies, but also accompanied by an increase of intensity, frequency, and duration of extreme events, namely heatwaves and dry spells. These findings thereby corroborate the need to adopt timely and effective adaptation strategies by the regional winemaking sector to warrant its future sustainability and enhance climate resilience.

Robust Bias-Correction of Precipitation Extremes Using A Novel Hybrid Empirical Quantile Mapping Method: Advantages of A Linear Correction For Extremes

“…EQM, which is used to correct low-valued quantiles in both bias-correction methods, results in the majority of excessive low-precipitation days being set to zero. The underestimation of wet day frequency after biascorrection via EQM is not unusual; similar results were found by [19] and [55]. Moreover, although wet-day frequency appears to be adequately represented in raw model data, it comes at the expense of substantial overestimation of total annual precipitation (TotalP) and precipitation intensity (SPI).…”

European Grapevine Moth and Vitis vinifera L. Phenology in the Douro Region: (A)synchrony and Climate Scenarios

“…In this way, three steps were undertaken to obtain high-resolution temperature datasets. First, the climate model simulated data, previously bias-corrected using E-OBS as a baseline [47], were subtracted from the E-OBS dataset on a daily timescale and at an ~11 km resolution (daily anomalies). Second, a bilinear interpolation (in the latitude × longitude grid) was applied to interpolate the anomalies from ~11 km to ~1 km grid resolution.…”

Grapevine Sugar Concentration Model (GSCM): A Decision Support Tool for the Douro Superior Winemaking Region

“…The DS winemaking region is located in a "climate change hotspot", meaning that the impacts of climate change in this region may be particularly severe [42]. Current studies indicate that this particular sub-region of the Douro PDO may be negatively affected in terms of viticultural productivity [43], particularly due to the increase in extreme weather events [42,44]. In effect, climate change impacts on viticulture are already being reported in different regions worldwide, such as the shift in phenology, higher sugar concentration, and late spring frost problems [45][46][47][48][49].…”