Agroclimatologia statica e dinamica del Veneto: analisi del periodo 1956-2004

Climatic and meteorological trends have always influenced, respectively in the long and short period, agricultural activity, acting for example on the territorial distribution of the crops and on seasonal yields. Climate is one of the main "production factors", influencing not only field agricultural practices, but also the multiyear planning. In the last decades the perception to live an anomalous meteo-climatic phase has increased on the base of global scale studies; the media and the rising consciousness of the public opinion, induced political authorities to assume, at national and international levels, strategies for the control and reduction of the hypothesized future impacts. Global analyses envisages the exigency of new detailed studies at local scale carried out on the base of available time series. More specifically the aim of this work was the description of the agro-climatic situation at local level for Veneto Region 1956-2004 time series of meteorological variables. This work has also tried to give a brief description of the possible future scenarios. Crucial has been the definition of a method to describe climatic change on the base of physical variables (temperature, precipitation, reference crop evapotranspiration, circulation indexes) and biological ones (phenological phases). In particular the approach of the most part of the scientific community (past climate behavior described by statistical linear interpolation methods with possible extrapolation of future trends) was integrated by the adoption of techniques of discontinuity analysis. These methods are useful to put in evidence that an important aspect of climate evolution is represented by abrupt changes with different phases separated by break-points. Moreover the initial hypothesis of this work is that these break-points separate climatic homogeneous phases, whose trends are useful to be analyzed instead of the description of trends belonging to not homogenous periods. This thesis approached both the aspects of static climatology (spatial-temporal behavior of surface meteorological variables) and the classical themes of the dynamic climatology (relations between macroscale circulation patterns and meteorological phenomena at surface). By the dynamic point of view the correlation between macroscale circulation indexes (NAO, ENSO, PDO, etc.) and surface meteorological variables gauged for Veneto region on the period 1956-2004 was studied. Results show the existence of a climatic breakpoint in the ’80 with a consequent change of climatic phase. This change point is particularly evident for temperatures and evapotranspiration: in particular after the change point, temperatures show a significant increase (respectively +1.5 and + 0.9 °C for yearly averages of maximum and minimum temperatures as regards to the previous phase) present in al seasons and particularly evident in spring, summer and winter for maximum temperatures and in summer for the minimum ones. Time series show a substantial stationary of seasonal precipitation with the only exception of winter ones, which show a significant decrease (in average -78 mm as regards to the previous phase,). The territorial analysis show that the situation is particularly critical for the central - southern plain (Polesine), which after the breakpoint shows an increase of aridity. This problem is enhanced by the fact that it involves the area that at regional level show the worst average values of water deficit. The evidence of a change of phase in the '80 is strengthened by (i) analysis of phenological data regarding some Veneto crops (grapevine, maize and soft wheat) per il Veneto (ii) analysis of climatic data of other Italian regions (Emilia Romagna and Piemonte) (iii) climatic and phenological analyses referred to other European regions. Climatic change is also highlighted by the expansion of the irrigation practices on grapevine in many different environments of Veneto Region. The results of this study show some operational rules referred to adaptation strategies, which should for example promote the adoption of crops with fall-winter cycle, and in particular barley and wheat, which minimize the risk of high temperature and aridity