Irrigation scheduling using the Typical Meteorological Year methodology

Typical Meteorological Year (TMY) is widely used for designing climate control systems, and its use in agriculture is limited to greenhouses. The aim is to adapt the TMY methodology for irrigation schedule advisory, in this case in the Protected Geographical Indication "Ajo Morado de Las Pedroneras" (PGIAMP) (Spain). A TMY consists of 12 months selected from individual years and concatenated to form a complete year. The months selected were chosen from statistics determined by the following indices commonly used for irrigation scheduling: reference evapotranspiration (ETo), rainfall (P), and minimum (T-min) and maximum temperature (T-max). For adapting this methodology to irrigation schedule, the weighted sum (WS) for each index was determined comparing the TMYs obtained through four different weight combinations with the reference TMYs (calculated assigning to each factor the maximum weight). The 11 years of daily climatic data (2001-2011) for TMY development were from the 18 weather stations in PGIAMP. For decreasing the number of required TMYs annual data (average temperature (T-ave), accumulated ETo and P) were statistically analyzed with a Duncan test to group stations. The Duncan test grouped the weather stations in three groups. Rainfall is the parameter with the greatest variability. The WS values determined for ETo, P, T-min, and T-max were 30/100, 60/100, 5/100, and 5/100, respectively. The three TMYs data series generated were compared with the annual average of T-max and T-min, and with the annual accumulated P and ETo of each individual weather station for the series studied, falling within an acceptable range determined by the standard deviation of the annual data. The use of the TMY