Cumulative indices
On this page, cumulative phytoclimatic data are reported to carry out analyses and observations among different periods of interest.
Last updated
On this page, cumulative phytoclimatic data are reported to carry out analyses and observations among different periods of interest.
Last updated
By clicking on the "Select Period" button (at the top right), the drop-down menu appears where you can select the accumulation period of interest for the automatic calculation of cumulative counters. The default accumulation period is 1 day (exactly the day before the one being consulted). After selecting the period of interest, all indices and their corresponding graphs are recalculated.
The histograms (in the top part of the page) display the cumulative value totaled over the selected time window. Under each histogram, the duration in days of the selected time interval and the unit of measure used for the calculation are reported.
In particular, the main cumulative indices are as follows:
total unitary radiation that hit the ground (often not an actual measured value but an estimated parameter based on the geographic location)
millimeters of rainfall
total hours during which leaves were wet (both due to rain and high humidity)
total millimeters of evapotranspiration (estimated potential value - not optimized for a single crop)
accumulation of degree days (heat sums) that exceeded the thresholds of 10, 18, and 20 °C.
Degree days are calculated using the following formula:
Each day, the average temperature is computed and subtracted from the different target temperatures (10°C, 18°C, and 20°C). If this difference is negative, the result is zero. The cumulative value is then calculated day by day.
The line charts (in the lower part of the page) show the daily cumulative values in the selected time interval. For example, the cumulative rainfall line chart is drawn by connecting the total daily rainfall values, that is, the total millimeters of rain that fell each day. The cumulative wetness line chart is drawn by connecting the total daily leaf wetness values, that is, the total number of hours, calculated each day, during which the leaves were wet.
Note: The line charts of the cumulative indices show the daily cumulative values in the selected time interval. Therefore, the respective alarms will be triggered only in case of exceeding the configured alarm threshold by the daily cumulative data.
WiForAgri's evapotranspiration parameter represents the reference potential evapotranspiration. It is indicated by ET0 and refers to an ideal situation standardized by FAO (a 12 cm high, dense and uniform Festuca Arundinacea lawn in the vegetative growth phase and in optimal water and plant health conditions). Since the only variables used in the ET0 calculation formula are microclimatic factors related to the air, it can be stated that ET0 expresses exclusively the evaporative power of the atmosphere determined by the climatic conditions of the area. The ET0 calculation model implemented by WiForAgri is that of Hargreaves (1994).
The value of ET0 is quite different from the actual evapotranspiration of a specific crop: in the next paragraphs, the estimation procedure is illustrated to move from the value of ET0 (reference potential evapotranspiration) to ETc (crop potential evapotranspiration) and then to ETr (estimated actual evapotranspiration).
It is possible to estimate ETc by multiplying ET0 by the Kc coefficient (crop coefficient) which is able to integrate the type of crop grown and the vegetative development stage (phenological phase) into the calculation of the evapotranspiration demand.
The value of the Kc coefficient varies throughout the growing season: its value increases from the beginning of the crop cycle to plant maturity and decreases during yellowing until leaf fall. For perennial crops, the Kc also varies over time with plant growth.
Finally, to calculate the Real Evapotranspiration (ETr), which takes into account the actual vegetative limiting conditions and defense mechanisms of the plants (e.g. stomata closure), ETc is multiplied by the stress coefficient Ks that varies according to the environmental and agronomic conditions (e.g. soil conditions and agronomic techniques).
