The converter uses guidelines set out by the Bureau of Meteorology (BOM) This calculation also doesn't utilise rain as a component, as such if your spray requires a period of dry weather before or after spraying please take the time to do extra checks. Please note that this is just and indicator, and further checks need to be made based on the type of spray you are using, as well as any other factors such as local Council rules. We assume our temperature sensors in a shroud to be close to Dry Bulb Temp, and utilise temperature, humidity, and pressure (optional) for calculating Wet Bulb. Spray when delta T (Dry Bulb Temp - Wet Bulb Temp) is between 2 and 8, and not greater than 10.Avoid Calm conditions (below the 3km/h).Harvest uses the following checks when determining if it is possibly safe to spray: The Can I Spray Indicator uses wind, humidity, temperature and pressure (optional) to indicate if it is possibly safe to spray or not. Required Sensors: Temperature Sensor, Leaf Wetness Sensor Can I Spray Indicator After four hours of 'dry' the risk index is reset. The I values were summed for the duration of each wet period. Where I is risk index and T is the mean air temperature during a wet hour. When this index reaches 1.0 there is a high probability of infection and crops should be sprayed or irrigation reduced or stopped.ĭata from the leaf wetness sensor is fed into a model developed in New Zealand by Dr Balasubramaniam (Bala). This will give the best data results.īy measuring the duration that leaves have been wet, and utilizing a temperature sensor we can apply these to the Botrytis disease risk model and provide an output in the form of an infection index value. It is also recommended that the sensor be mounted at a 10 degree angle so it is almost horizontal. For best results the sensor is recommended to be placed NEAR the crop but not in it to avoid it being sprayed.

To detect Botrytis risk we monitor leaf wetness using the Decagon leaf wetness sensor. Bacchus Botrytis Disease Modelīotrytis cinerea is a disease that affects soft fruits, mainly wine grapes, usually affecting vines that experience constant wet or humid conditions, or over irrigation. The North American formula was designed to be applied at low temperatures (as low as −46 ☌), when humidity levels are also low. The Australian formula includes the important factor of humidity and is somewhat more involved than the simpler North American model. The vapour pressure can be calculated from the temperature and relative humidity using the equation: v = wind speed (m/s) at an elevation of 10 m.It was extended in the early 1980's to include the effect of sun and wind. The apparent temperature, invented in the late 1970's, was designed to measure thermal sensation in indoor conditions. The Australian Bureau of Meteorology, using a model developed by the US Navy, researched and then developed their own formula, the Australian Apparent Temperature. Australian Apparent Temperature (Feels Like) If you don't already have the sensors, give us a call and we can let you know if it will work with your unit and what the addition will cost. If you do, it is as simple as calling and asking for the calculation to be added to your page. Check the list of sensors at the bottom of each description to see if you already have these sensors. At times, frost can form on objects even when the recorded air temperature is higher than freezing, because air temperatures are typically recorded approximately 4 feet above the ground.Below are a number of calculations that Harvest can calculate using various sensors attached to our monitoring systems. Frost typically forms on low-to-the ground objects (grass) and cold objects (car roofs and windows) because the temperature of those objects is actually colder than the ambient air.

Ideal weather conditions for frost to form are calm, clear, cold nights when the temperature drops to near or below freezing. When this happens, the dew point equals the frost point. Frost forms when the dew point reaches freezing point or lower and the air temperature equals or is less than the dew point temperature. Frost formation greatly depends on the level of relative humidity in the air. The frost point is the temperature at which air can no longer hold its water in vapor state, and the air temperature reads close to or below freezing (32 degrees Fahrenheit). Frost is a crystalline formation of small, thin ice crystals that form on objects when the air directly above the object reaches the frost point.

Contrary to common opinion, frost is not frozen dew.

Frost point to dew point calculator