Forecast unsuitable spraying conditions #12
Description
This is a pesticides application weather service able to forecast unsuitable spraying conditions and to determine optimal spray times.
Prerequisites
a) Dry Bulb Temperature - Tdb
The Dry Bulb temperature, usually referred to as air temperature, is the air property that is most common used. When people refer to the temperature of the air, they are normally referring to its dry bulb temperature.
The Dry Bulb Temperature refers basically to the ambient air temperature. It is called "Dry Bulb" because the air temperature is indicated by a thermometer not affected by the moisture of the air.
Dry-bulb temperature - Tdb, can be measured using a normal thermometer freely exposed to the air but shielded from radiation and moisture. The temperature is usually given in degrees Celsius (oC) or degrees Fahrenheit (oF). The SI unit is Kelvin (K). Zero Kelvin equals to -273oC.
b) Wet Bulb Temperature - Twb
The Wet Bulb temperature is the temperature of adiabatic saturation. This is the temperature indicated by a moistened thermometer bulb exposed to the air flow.
Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin. The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a "wet bulb temperature" lower than the "dry bulb temperature" in the air.
The rate of evaporation from the wet bandage on the bulb, and the temperature difference between the dry bulb and wet bulb, depends on the humidity of the air. The evaporation is reduced when the air contains more water vapor.
The wet bulb temperature is always lower than the dry bulb temperature but will be identical with 100% relative humidity (the air is at the saturation line).
How to calculate Twb:
Tw=Tarctan(0.151977RH+8.313659)+0.00391838RH3arctan(0.023101RH)−arctan(RH−1.676331)+arctan(T+RH)−4.686035
reference: https://www.omnicalculator.com/physics/wet-bulb
Spray during favorable weather conditions.
a) Wind speed is critical. Air movement is needed to ensure that mixing occurs in the air. This helps to deposit airborne droplets. Wind speeds should be below 15 km/h as measured at the site of application, depending on the label instructions. If the wind speed is etween 15-25 km/h, spray with caution. Wind speed above 25 km/h means that the weather is unsuitable for spraying.
b) Rain — Ideally, you should schedule spraying for periods with no precipitation. If you experience precipitation under 0.1 mm, spray carefully. Do not spray when precipitation intensity is more than 0.1 mm.
c) Temperature should be under 18 °C in optimal conditions. When temperature is between 18 and 25 °C, spray with caution. The weather is unsuitable for spraying when the temperature is over 25 °C.
d) Humidity between 60-85% is optimal for spraying. Spray with caution when humidity is between 45-60% or 85-95%. Humidity below 45% or over 95% indicates that the weather is not suitable for spraying.
e) Delta T is an atmospheric moisture parameter, defined as the dry bulb temperature minus the wet bulb temperature, and provides a better indication of water evaporation rate than relative humidity alone. Avoid spraying when the Delta T is either too high or too low, it should be within a range of 2-8. If Delta T is between 0-2 or 8-10, spraying conditions are marginal, spray with caution. Do not spray if Delta T is under 0 or over 10.
Functionality
The service will get current and forecast weather conditions and will evaluate the values of Temperature, Wind, Precipitation and Delta against the set or rules defined above. Then on an one hour timeframe bases a categorisation will occur for spraying pesticides as : "optimal", "marginal", "unsuitable".