Spanish Wine Region Climate Calculator
Evaluate climate suitability for major Spanish wine regions by calculating Growing Degree Days (GDD), Huglin Index, and Dryness Index to determine grape variety compatibility.
Formulas Used
1. Growing Degree Days (GDD) — Winkler (1974):
GDD = max(0, (Tmax + Tmin) / 2 − 10) × 214 days
Base temperature 10°C; growing season April–October (214 days).
2. Huglin Index (HI) — Huglin (1978):
HI = Σ[(Tmax + Tmean) / 2 − 10] × k
where k = latitude coefficient (1.04 for Spain, 36°–44°N), summed over Apr–Oct.
3. Dryness Index (DI) — Riou et al. (1994):
DI = W₀ + P − Tv
W₀ = 200 mm (initial soil water reserve); P = growing season precipitation (60% of annual);
Tv = potential evapotranspiration ≈ 6.75 × Tmean (simplified Hargreaves).
4. Altitude Temperature Correction:
ΔT = −0.65°C per 100 m altitude (standard atmospheric lapse rate).
5. Overall Suitability Score:
Score = (HI_score × 0.40) + (DI_score × 0.35) + (Sunshine_score × 0.15) + (DTR_score × 0.10)
Assumptions & References
- Growing season defined as April–October (214 days), standard for Spanish viticulture.
- Huglin latitude coefficient k = 1.04 representative of Spain (36°–44°N); precise value varies ±0.02 by latitude.
- Growing season precipitation estimated as 60% of annual rainfall — a reasonable approximation for most Spanish regions; actual values vary by region.
- Evapotranspiration uses a simplified Hargreaves coefficient (6.75 × Tmean); full Penman-Monteith requires additional radiation and humidity data.
- Initial soil water reserve W₀ = 200 mm (OIV standard assumption for DI calculation).
- Optimal sunshine for Spanish viticulture: 2,200–3,000 h/year (Ministerio de Agricultura, Pesca y Alimentación).
- Optimal diurnal temperature range for quality wine production: 12–18°C (Jackson & Lombard, 1993).
- Preset region data sourced from AEMET (Agencia Estatal de Meteorología) 30-year climate normals (1991–2020).
- References: Huglin P. (1978) Nouveau mode d'évaluation des possibilités héliothermiques d'un milieu viticole; Winkler A.J. et al. (1974) General Viticulture; Riou C. et al. (1994) Le déterminisme climatique de la maturation du raisin; OIV Resolution OIV-VITI 423-2012.