The following is an example of what kind of information can be retrieved from a Campbell Scientific automated weather station.
This station is located at Darfield, mid-Canterbury, New Zealand and owned by the Selwyn Plantation Board. Its primary function is to collect meteorological data as part of New Zealands Rural Fire Weather Network. For this purpose it measures the following variables:
Data is collected over telephone by forestry companies, the National Rural Fire Authority and other interested parties. This data is then processed to calculate the fire risk for each area and forwarded to Bernie, the little guy who races around the country changing the fire danger signs every day. (Bernie says that this now gives him time to sink back and enjoy a couple of cold ones while the computers do all the number crunching.)
In addition to these parameters, additional sensors have been added to gather information of interest to other groups in the area, namely:
Adding a solar radiation sensor makes it possible to calculate potential evapotranspiration (PET) (using the Penman-Monteith Equation for you soil buffs). This is a useful value to use for irrigation scheduling. Adding the Aquaflex soil moisture sensor allows us to compliment this PET value by measuring the changing actual soil moisture.
Data is collected automatically using WeatherPro 3 software developed by Remsoft. This package automatically polls the station, retrieves the latest data, calculates the indices required and any other parameters such as soil moisture deficit. Then it automatically graphs the data and transfers the graphs to our web server.
So...what does this all look like?
Soil Moisture Against Calculated Potential Evapotranspiration
Soil Moisture Defecit
When the values are negative the storage is above field capacity and drainage will occur. Field Capacity denotes the soil moisture storage that the profile drains to quickly after saturation has occurred.
The CR10X, the brains of the station, takes readings every three seconds from the attached meteorological sensors. These are stored and used to calcluate minimums, maximum, averages & totals and applied calculations such as potential evapotranspiration and soil moisture defecit. Data is stored hourly and daily at 0900, 1200 and 0000 hours in different identifiable arrays. The datalogger also controls the switching on/off of sensors and the telemetry options.
Vaisala HMP35C Temperature & Humidity Sensor
Combination air temperature and humidity probe. The temperature is measured using a 107 thermistor, and humidity with the HUMICAP H-sensor, measuring 0-100% RH. Accuracy +/-3% RH 0-90%, +/-5% 90-100% range. Used within a RS-35C naturally aspirated radiation shield on an extended arm from the mast. Weatherproof connectors are used to make servicing and replacement simple, without entry to the datalogger enclosure. (The HMP35C has now been superceded by the HMP45A)
The worlds, longest soil moisture sensor, and Kiwi designed and manufactured. Aquaflex measures soil moisture in volumetric moisture content and averages readings over its 3m length, a 6 litre volume of soil, overcoming traditional problems of soil variability. The sensor is used to measure soil moisture in the top 350 mm of the soil profile (where most pasture roots are) by placing the sensor ribbon in a sloping trench from just below the surface to 350mm depth. This allows the average water content to be measured over the profile so a water balance can be calculated.
Precision wind sensors from the UK withstand wind speeds up to 75 m/s. The A101M is a pulse output anemometer with a starting threshold of 0.15m/s and 1% accuracy over the full range. The W200P is a potentiometer wind vane with a starting threshold of 0.6m/s and accuracy of +/- 2 degrees
Ota 0.2mm Tipping Bucket Rain Gauge
International standard tipping bucket rain gauge with 0.2mm tip.
This sensor measures solar radiation with a silicon photovoltaic detector (just like a miniature solar panel) within the 400 - 1100 nm range. Used extensively in solar, agricultural, meteorological and hydrological applications.
Telemetry & Data Retrieval
Data is retrieved via telephone telemetry using the Campbell Scientific DC112 modem connected to the datalogger and landline. Data can be retrieved from any PC running PC208W or PC208 or Remsofts WeatherPro3. We use WeatherPro3 to call the station, retrieve data, create graphs and tables and ftp them to our web site.
Power
The low power requirements of the CR10 mean that the station can easily be powered by solar panel. We use a Solarex 50W solar panel and regulator. This recharges the 12VDC battery used by the datalogger.
Structural
The 10m tilting mast is designed to be easily lowered by one person for servicing of the wind instruments. These, and the Temp/RH sensor are connected using environmental connectors so they can be removed without rewiring the datalogger. The datalogger, battery and telemetry components are all enclosed within the sealed stainless steel enclosure.
