General climatology of the rice area of the Novara Province
The Po valley is a large basin surrounded by high mountains (Alps and Apennines) and opened only toward East.
If the Easterly opening expose the area to winter cold outbreaks of polar continental air coming from Siberia,
the mountain ranges protect the area from the influence of the circulation that characterise the climate of
Central Europe and of Mediterranean. According to this, the climate of the Po Valley is a climate of transition
between the Mediterranean climate (Koeppen Csa) dominated by anticyclonic patterns and the Central European
climate (Koeppen's Cfb), dominated by the oceanic influence of westerlies.
This transitional character of the Po valley climate is shown by the precipitation regime that, with two minima
(in summer and winter) and two maxima (in spring and fall) is partially opposite in phase with respect to the
evapotranpirational request of the atmosphere, which show a maximum in summer. The consequence is a moderate
drought during summer which is intermediate between:
the strong summer drought of the Mediterranean climate, which show a strong precipitation minimum in summer,
clearly opposite in phase with respect to the evapotranpirational request of the atmosphere;
the absence of summer drought of the Central European climate, which presents the precipitation maximum in
summer, clearly in phase with respect to the evapotranpirational request of the atmosphere.
The area is characterised by yearly mean values of 800 – 1000 mm year-1 for precipitation and
950-1100 mm year-1for reference crop evapotranspiration (ET0); the main driving variables of ET0 show the
following behaviour:
air temperature: for the study-area the mean annual value is about 12.5-13.5 °C, with absolute minimum and
maximum registered in January–February and July-August respectively;
wind: the main contribution to mean wind field is given by breezes which dominate during anticyclonic weather
patterns (about 200 days year-1); these winds show a dominant direction from north east during night and from
south west during day with mean speed of 0.3-0.7 m s-1; strong and gusty winds from north (maximum velocity
of 15-25 m s-1) are gauged about 15-25 days year-1, during alpine foehn episodes; low or moderate
winds dominates during cyclonic weather patterns (about 100 days year-1); during these situations the prevailing
winds are from east or south east.
Global solar radiation: peak values of 28-31 MJ m-2 day-1 are reached in summer sunny days.
Relative humidity: the area show mean yearly values of 65-70%, with strong minima (10-15%) reached during alpine foehn episodes.
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