Backyard Meteorological Instrumentation

Site Information

The site in  question is part of a 1000 m2 house block in the northern suburbs of Adelaide, South Australia. Adelaide has a Mediterranean climate (K√∂ppen climate classification Csa), with mild wet winters and hot dry summers. Adelaide experiences solar irradiation levels reaching approximately 4.83 kilowatt-hours per square metre per day on average over a year. However, if a solar system is to be considered, the winter readings must also be considered  as there may not be enough solar energy to run the system during this season.

A cursory investigation of the illumination by the Sun in December indicates that the area in the top left of the picture is shaded in the morning by the trees in the cemetery on the other side of the rear fence and shaded by the metal fence and the tool shed in the afternoon. The advantage of this site is that the tool shed has power that can be easily supplied to that area if the solar power is not enough. There is also a straight run from the rain water tanks next to the house that could be used for an automated watering system, if desired.

The rightmost area of the image and backing onto the swimming pool enclosure gets some shade in the morning from tall trees out of view in the cemetery. Being next to the swimming pool, it is a convenient location if pool water monitoring is implemented. It is also located between garden beds which would make the monitoring of ground temperature and soil moisture easy. The closest mains power is near the bottom right corner of the pool. This would mean that any power cable from that outlet would need to cross the entrance to the pool enclosure or the path around the pool.

Site Selection

Being a suburban house block, the placement of the primary meteorological sensor is unable to conform to the requirements Para 2.2.2 of the BOM's Guidelines for the Siting and Exposure of Meteorological Instruments and Observing Facilities "The station should not be sited on or close to steep slopes, ridges, cliffs or hollows. It is also important to avoid sites near large buildings or other obstructions." It is clear that neither of the available positions meet the BOM criteria, although the rightmost plot is less restricted that the leftmost plot which is adjacent to high metal fences, garden sheds and trees.

The right hand site provides exposure that is closer to the BOM standard compared to the left hand site, but does not have easy access to power. It does, however, provide a better location for the installation of solar panels to power the sensors. Unlike the left hand site which as access to the household gigabit LAN, there is no easy access to data communication except via Wi-Fi.

Since the Wi-Fi router is located in the front of the house, it is not known whether there would be adequate reception for a device such as a Raspberry Pi, or similar. If connection to the house router is nor practical, it should be possible to use something like another Raspberry Pi (or similar) to provide a Wi-Fi connection to the right hand plot, if required. A more physically complex solution would be to run an Ethernet cable between the two locations and use PoE (Power over Ethernet) to power the right hand sensors. The distance around the fence line between the two locations is about 20 metres and within the limits imposed by even cheap PoE devices. A PoE link would have a relative low bandwidth (between 10~100 Mbits/second).

The other alternative is not to select a single sensor site, but to use both sites. The left site where the better sun exposure is as important and/or the sensor requires a significant amount to power to provide high rate measurements, while the right hand site is best for sensors whose measurements are more influenced by the Sun, such as ground temperatures, etc. or benefiting from open space such as the anemometer.

Using both sites allows the project to commence with the powered site and to start development with access to both the home LAN and mains power.

For ease of development, the left site will be developed first and then a decision will be made whether to power the right hand site using a Power over Ethernet (PoE) cable from the left unit, or to independently powered using a solar array.

The image to the right shows the unused area selected for this project. At the start, it had just been a bit of a dumping ground that could benefit from a clean up.

The area is partially shaded by the fruit trees in the yard and the native trees in the cemetery on the other side of the back fence. Not visible to the left of the image is a garden shed. That shed and the other fence tend to shade the plot in the late afternoon. The fences also tend to reflect heat back onto the area when it is sunny.

All of these factors make the area challenging when it comes to measurements that are directly affected by the intensity of the Sun, but other measurements such as the air quality monitors should be less affected by the challenging location. These sensors use the most power, especially when the measurement rate is high, so being close to the mains power in the shed is an advantage of the site.

The first stage in this project was to clean up these area and create a border for an area to hold the sensors. Once it is cleaned up and the equipment shelter installed, the area would be grassed.

Besides the grass lowering the surface temperature during the heat of summer, it is less likely that dirt will be tramped into the house if the area is grassed, thus reducing the potential for domestic conflict.

Not being a gardener, a few problems arose with the grass. Not the least of which was that disturbing the soil, then fertilising and watering it resulted in a weed load that was greatly in excess of the grass that was planted. The most practical solution was to use a weed spray to sterilise the area before planting more grass seeds.

Licenced under Creative Commons Attribution Share Alike 4.0 International or better by Mark Little (2022 - 2023)