The Weather Station

Location: 48° 51' 33" N; 122° 35' 39" W

Weather Conditions at the Old Jeffcott Place




Weather Software
The software that runs this weather station consists of a number of tasks, which run at specified intervals. Some tasks are responsible for reading the weather instruments; other tasks are responsible for formatting the data and posting it to logs and weather web sites.

Wind Speed
The wind speed task samples wind speed every three seconds and places each sample into a buffer, averaging over a two-minute sliding window. It calculates the minimum and maximum wind speed every sample period.

Wind Direction
The wind direction task samples the wind direction every five seconds and places each sample into a buffer, averaging over a two-minute sliding window. The averaging algorithm uses vector averaging.

Temperature
The temperature task samples the temperature sensor once a minute and places the data in a buffer, averaging over a ten-minute sliding window, and calculating the minimum and maximum temperature every sample period.

Humidity and Dewpoint
The humidity task samples the humidity sensor every minute and places the data in a buffer, averaging over a ten-minute sliding window, and calculating the minimum and maximum humidity every sample period. Dewpoint is calculated from the humidity and temperature data.

Barometric Pressure
The barometer task samples the air pressure sensor every minute and places the data in a buffer, averaging over a ten-minute sliding window, and calculating the minimum and maximum air pressure every sample period.

Rainfall
The precipitation task samples the tipping-bucket rain gauge every minute and converts the number of bucket tips (0.01 inch each) into total accumulation since local midnight, and the number of bucket tips per minute as rainfall rate in inches per hour summed over a 60-minute sliding window.

Posting Data to Weather Underground
Every ten seconds (a.k.a. "RapidFire"), the weather underground task posts the average temperature, average humidity, rainfall rate, accumulated rainfall since midnight, the average wind speed, the maximum wind speed recorded for the previous ten seconds and the average wind direction to Weather Underground Data Exchange.

Posting Data to Citizen Weather Observer Program (CWOP)
Every ten minutes, the CWOP task posts the average temperature, average humidity, rainfall rate, accumulated rainfall since midnight, the average wind speed, the maximum wind speed recorded for the previous ten minutes and the average wind direction to CWOP.

Weather Instrument Specifications
Weather Instrument Cluster
Temperature
Anemometer
Wind Vane
TAI8515 1-Wire Weather Instrument Kit V3.0
Dallas/Maxim DS18S20
Dallas/Maxim DS2423
Dallas/Maxim DS2450
Aux Air Temperature TAI8540A 1-Wire Humidity Module
Hygrometer TAI8540A 1-Wire Humidity Module
Barometer TAI8570 1-Wire Pressure Sensor
Precipitation TAI8575B 1-Wire Rain Gauge
Technology Dallas 1-Wire MicroLAN
Platform 2.66GHz Intel Celeron D/1GB RAM/13GB HDD
Windows XP Home SP2
Software Dallas 1-Wire TMEX Drivers
Uppiano 1-Wire Weather Service for Java

Radiation Shield
To reduce solar warming effects on my thermometer/hygrometer, I built a radiation shield out of nested foil pie tins (see figure 1, above). At this time, the pie tins are not painted, they're just natural aluminum. They started out shiny, as pie tins do, but they have weathered down to dull aluminum, as pie tins also do.

The effectiveness of the radiation shield seems quite good. My temperature data quality typically rates "two thumbs up" from MADIS. I have some maintenance scheduled for this summer, and I might paint them with some flat white epoxy at that time, and see how that affects accuracy.

Disclaimer
The Weather Underground is a respectable organization, providing useful weather information, hobbyist support and other interesting services. They took their name as a tongue-in-cheek reference to the radical 1960s Weather Underground political group. Both Weather Undergrounds got their start at the University of Michigan. It may have been tongue-in-cheek, but during the 2008 election, I have become much more familiar with the radical Weather Underground and its co-founder, William Ayers. These despicable people were domestic terrorists responsible for more than a few deaths in this country, and on 9/11, Ayers expressed regret that he "hadn't done more".

I understand his frustration at social evolution when it doesn't go the way we think it should. I have felt that my whole life. My principles happen to be diametrically opposed to Ayer's, but I understand his frustration nevertheless. That is why I think, if he wants change, he should have to accomplish it in the free market of ideas like everyone else, and not by having tantrums, or bombing, or trying to force everyone else to do things his way, just because he can't understand, or doesn't like the status quo. Who anointed him dictator?

He avoided prison on a technicality, and is now a tenured professor at the University of Illinois, teaching the next generation of educators how to indoctrinate the next generation of students. Disgusting. With this knowledge, I think it is time that the new Weather Underground consider changing its name to something else. I get the joke, and it isn't funny anymore.