Properly siting weather stations on farms
/by Michelle Cortens
The diverse areas of expertise needed on a farm never cease to amaze me. Now, as weather station technology becomes increasingly affordable, you might be able to upgrade your resume from weather enthusiast to weather forecaster.
As we envision a future with more weather stations on farms, we also need to understand what’s involved in their operation and spread the word about best practices. Using standard practices in siting and maintenance means that, all other things being equal, you can gloat that you got 10 millimetres more rain than I did. Otherwise, inconsistencies make the data unreliable for comparison between sites.
This spring, I helped site 10 weather stations across the Annapolis Valley and learned from a few installations that it’s more than a matter of plunking a station in the ground.
“Over there! That’s a nice open grassy area,” I said to the others on a farm during our quest for the perfect spot. It’s tempting to think that the station should go in the crop, but the goal of siting a weather station is to mimic conditions in the natural environment. To do that, the station must be far enough away from artificial heat sources such as large rock piles and obstructions to air flow and rain such as buildings, cars, brush piles, and trees. Open, grassy fields fit the bill.
That being said, one of the grassy areas we came across wasn’t a good site because it was next to a pond. A pond can influence the temperature and humidity in the surrounding area, so it’s not representative of a larger field or entire orchard. In the case of a large lake or basin, the water body affects the climate of the entire area, so a weather station in the vicinity still represents the area.
With the site chosen, the next step was to install a stable mount for the sensors. Weather station suppliers might have metal tripods available, but a sturdy wooden post is a surprisingly good option. A four- to six-inch wide post installed three feet in the ground isn’t going anywhere – likely not even in a hurricane. The bigger risk is heavy equipment running into the post, so the mount should be decorated with reflectors and orange spray paint.
One by one, the different sensors were mounted. There are a variety of sensors, but there are some standard ones for farm-relevant data. The wind sensor measures the wind direction from a wind vane and the wind speed from cups that turn in the wind. The combined temperature and humidity sensors are protected by a radiation shield, which cleverly blocks the sun from heating the sensors but allows air to flow for measuring the air temperature. The rain gauge can be a tipping bucket with little spoons that tip back to empty the water after a certain volume has accumulated. Other sensors can measure the intensity of the sun, leaf wetness, soil moisture, and more.
If a solar panel is powering the station, then installing it facing south will help get the most out of the sun to maintain a charge. Charging the battery might not be an issue in the summer but in the fall and winter months, the more sunlight, the merrier.
Sensor readings can be kept consistent between sites by levelling the sensors on the mount. It’s particularly important that the rain gauge and wind sensors are level. The equipment and mount can shift over time, so sensors should be checked occasionally and levelled again.
Everyone using the weather station is responsible for watching the data and determining if the information is realistic. Was water collected in a rainstorm? If not, the rain gauge could be clogged with debris, or sturdy spider webs could be preventing the tipping spoon from tipping. Is the temperature reasonable relative to other nearby weather stations? Maybe the solar panel even needs a wipe.
A weather station is like any other piece of equipment in the sense that you need to plan for ongoing maintenance and repairs. Preventative replacement of sensors and batteries before they fail is a good approach to ensure consistent and reliable data for the farm. Check with suppliers for a recommended replacement schedule. For example, the lifespan of a temperature/humidity sensor in our wet and humid environment is reportedly four years.
I would like to thank Jonathan Buffet, the founder of Cape Breton Weather Mesonet (a cooperative network of privately owned weather stations across Cape Breton Island), for sharing his wisdom in weather stations, and the Nova Scotia Fruit Growers’ Association for owning the 10 weather stations and working collaboratively to gather the data.
The new network has started to reveal differences in the Annapolis Valley microclimate – as much as six-degree differences in daytime maximum temperatures throughout the Valley – and significant differences in rainfall and wind speed. Of course, we know there are microclimates, but the key will be to wield weather data to help us make management decisions.
Plant growth, insects, and diseases are all weather-driven, and science explains many of the relationships. What an incredible opportunity to pair weather data with predictive models. It takes time to adopt new tools, but the ultimate goal is to save money and time by identifying optimum management opportunities.
(Michelle Cortens is a tree fruit specialist with Perennia Food and Agriculture Inc. based in Kentville, N.S.)
