The Weather Stations

The myWeather project uses Davis Instruments Vantage Pro weather stations to take atmospheric measurements. Records from these instruments are rated as being usable by the scientific community and are used by researchers at CSAG regularly. Initially the Davis Instruments Weather MonitorII was used but all new (er) installations use the Davis Instruments Vantage Pro weather station. All the school-based Weather MonitorII stations have had to be decomissioned but these will be replaced with Vantage Pro stations as funding (sponsorship) becomes available.

The Vantage Pro weather station provides information (through direct measurement or calculation) on temperature, wind speed and direction, rainfall, pressure and humidity. The Vantage Pro has the benefit of recording more data and being able to transmit data over a wireless link to a receiver console up to 300 meters away from the base station. This facilitates optimal placing of the weather station at a location.

Alongside is a picture of the (bird-proofed) Vantage Pro at UCT. Numbers indicate the instrumentation on the weather station:

1. Radiation Shield holding temperature-humidity sensor, junction box, battery and wireless transmitter
2. Tipping Bucket Rain Gauge
3. Anemometer
4. Solar Radiation Sensor
5. Solar Panel
6. Console

Vantage Pro Specifications

The sensors which sample the weather variables need to be sensitive and accurate enough so that the data recorded can be used for scientific studies at CSAG. In meeting these requirements, the Vantage Pro weather station has sensors which sample weather variables at specific time intervals with specific ranges and accuracies. Below is a list of variables which are sampled and the sample interval for each.

Variable	Sample interval
Wind Speed	2.5 sec
Wind direction	2.5 sec
Rain rate	10 sec
Accumulated rainfall	10 sec
Temperature	10 sec
Radiation	1 minute

Operational ranges of the sensors and their accuracies.

Variable	Range	Accuracy

Inside temperature	-20 to 60 oC	+/- 0.5 oC

Outside temperature	-45 to 60 oC	+/- 0.5 oC

Wind speed	4 to 280 km/h	3.00%

Wind direction	0o to 360o	7.00%

Wind chill	-92 to 37 oC	2 oC

Pressure	880 to 1080 hPa	+/- 1.7 hPa

Humidity	0 to 100%	5.00%

Rainfall (Daily)	0 to 819 mm / hr	4% for rates from 0.2 to 50mm/hr 5% for rates from 50 to 100mm/hr

The vantage Pro wireless version can receive up to eight weather stations per console. The specifications of the transmitter are as follows:

Transmitter frequency	868.35 MHz
Transmitter range	300 m
Back-up battery life	2 years