30 December 2011 [Audio Journal] Building an Automated Weather System

Journal

What is an Automated Weather Station?

Here at AGO 4, I will be building an Automated Weather Station (AWS). The AWS is a tower that has instruments on it which records information about the weather. It sends weather information to a satellite, which transmits it to people at the University of Wisconsin at Madison. They put it up on the internet for all to see!

An automated weather system (AWS) — Terry Palmer helps Jonathon Thom and Lee Wellhouse install an Automated Weather Station at Willie's Field in McMurdo Station.

The AWS project originally started at Stanford University in the 1970s. In the early 1980s, the project moved to the University of Wisconsin at Madison. The first data from the weather stations began surfacing in the early 1980s. The work is funded by the National Science Foundation and data is distributed openly online. You can find out more about AWS at: http://amrc.ssec.wisc.edu

Instruments in the AWS

The AWS contains quite a few instruments that record varying aspects of the weather. It records surface pressure, wind speed and direction, air temperature, relative humidity, and at some locations, snow accumulation.

Aneroid Barometer

My favorite instrument on the AWS is the aneroid barometer. From the outside, the instrument looks uninteresting, however the amount of clever science going on inside of it is impressive!

The aneroid barometer measures air pressure. As the pressure changes outside of the barometer, it causes an accordion-like bellow inside the barometer to expand or contract. For example, if the pressure decreases, the accordion-like structure will expand. The accordion is connected to a piece of quartz. As the accordion pushes or pulls on the quartz (due to the change in pressure), the quartz vibrates at a different frequency. This is similar to the ring that you hear when you hit a piece of metal. Depending on how you hit it, the tone of the ring changes. The same is true with the quartz; it makes different frequencies (or tones) under different pressures from the accordion.

This part of the barometer completely astounds me! Crystals such as quartz vibrate at particular frequencies and changing the pressure will affect how the crystals vibrate. The barometer uses this principle to its advantage and when the crystal changes its vibration due to a change in pressure, the change is transferred to an electrical signal that can be measured as a proxy for pressure.

###Wind speed and direction

The AWS also has a wind turbine on it, which measures the wind speed and wind direction. When installing it, I have to be careful to make sure the black box under the wind turbine is facing South so that the wind direction is accurate. AGO 4 also has a wind turbine. We can compare the measurements to make sure they are accurate.

Temperature Probe

The temperature probe has a resistor inside the top metal probe that changes resistance as the temperature changes.

Humidity Probe

The humidity and temperature probe measure the amount of moisture in the air. This instrument also measures temperature.

Humidy probe — A humidity probe measures the humidity and temperature for the AWS.

Radiation Shield

The radiation shield blocks direct energy from the sun. It is placed onto the temperature and humidity probes to protect them from radiation and to keep their data readings accurate.

Pyranometer

The pyranometer will measure the light spectrum from the Sun at AGO 4. It is placed away from the other sensors to avoid shadows. The word "Pyranometer" comes from Greek: "Pyr" means fire, "ano" means sky.