Adding Value to Weather Data






There are plenty of valuable statistical summaries which help you understand what is happening around you. They typically involved calculating the average, maximum, minimum or sum for the chosen parameter for a time period. You may want to know what the average temperature for May was, or what was the highest wind speed recorded for August, or what was the weekly rainfall last week. All of these summaries are available through the Sensori Platform.

 There are two ways to generate them: firstly using an Aggregate function. Here the input tag (e.g. solar radiation) is used to generate the require summary (e.g. maximum daily radiation) which is then saved as a new “tag” in the database. This tag can then be viewed alongside any of the other sensor values; the second approach is to use the statistical summaries available in both the Graph and Table views. Here you select the sensor to view, then add the type of summary you want to show and the time period (e.g. sum of rainfall for the current month). The summary is then shown on the graph or as a column in the table.

But the real power of the system comes from combining the values of several tags in a mathematical formula which then produces a new “index” or risk factor.


Fire Danger Index


Fire Danger Index (FDI) is an index used in many fields to quantify the risk of a fire becoming uncontrolled. In many states, the FDI is used as a trigger to let broadacre farmers know when it is no longer safe to operate machinery on paddocks. The Grassland Fire Danger Index used in this application requires sensors for air temperature, relative humidity and wind speed. Once the calculation is in place you can set thresholds on a graph or create alarms which will trigger if the FDI exceeds a threshold.




Delta-T is a measure of the difference between the Wet Bulb and Dry Bulb temperatures and provides a surrogate for the humidity. Many chemical labels indicate conditions for safe use according to a range of Delta-T values. Prior to the introduction of electronic humidity sensors, two thermometers were placed side by side in a Stevenson screen. One was coupled to a wick which was inserted into water. Water would be drawn up the wick and evaporate at the bulb. The dryer the air, the higher the rate of evaporation and hence the higher the cooling effect. The difference between the values of the two thermometers is the Delta-T. Delta-T can also be calculated using the air temperature and relative humidity. Once calculated you can display it on a virtual instrument or graph. These can then be enhanced by adding the Delta-T limits for your application.


Sheep Chill Index


Sheep, particularly lambs, are vulnerable to cold conditions. The Sheep Chill Index uses temperature, wind speed, humidity and rainfall to provide an estimate of the amount of thermal energy which an animal will lose. Once the index exceeds a set threshold, lambs will not be able to keep warm and may die. If an alarm is set  based on the chill index, you can move stock to shelter before conditions deteriorate to the level where morbidity rates start to climb.


Cattle Heat Load


Cattle are badly effected by heat stress, with high stress levels impacting on animal health and meat quality. The Cattle Heat Load index calculation uses temperature, humidity and solar radiation data to model the heat felt by the animals. When conditions get back stock can be moved to shaded locations or other efforts made to keep them cool.


Inversion Monitoring


Normally as night falls, the temperature of the air  close to the ground stays warmer than the  air above it. When an inversion falls, warm air at height traps cold air below it. They normally occur in calm conditions and, when coupled with low humidity will result in high  frost damage. Another issue is that if farm chemicals are applied when an inversion is present (or forming) any aerosols which form will not disperse and will remain in the air. The formation of inversions and their impact on the movement of plumes of odour, smoke and aerosols has been widely modeled for environmental compliance. But it is now finding its way in to agriculture to provide recommendations on when conditions are safe to spray or not.

Inversion monitoring requires a pair of high accuracy temperature sensors, one installed 10m above ground and the other at 1.2 or 2m. The difference between the two is used to indicate the presence of an inversion: if it is cooler at 10m, no inversion is present,  but if it is warmer at 10m, an inversion is present.


Dew Point Temperature


The Dew Point temperature provides a measure of the temperature at which water vapour held in the air will change state and become liquid. If the dew point is above 0 degrees, it will form dew. But if the dew point is below 0 degrees it will form frost. Calculation of dew point requires air temperature and relative humidity


Black Bulb Globe Temperature


There is considerable literature around on how we humans experience heat and cold. The Apparent Temperature is one such measure and indicates how hot or cold we feel given the current air temperature, humidity and wind. Sporting groups are becoming increasingly concerned for the welfare of their participants, particularly where they are young or elderly. Many are now looking at having a reliable measure of when conditions are safe for play. The Black Bulb Globe Temperature is one measure which is increasingly being used for this purpose. It can be calculated using air temperature, relative humidity, wind speed and solar radiation.