About My Weather Station

Hardware

Davis Vantage Pro 2

Davis Vantage Pro 2 (wireless) w/ Fan Aspirated Radiation Shield (photo courtesy of Davis Instruments)

As of May 31, 2102, the data you see from my station was collected by a Davis Vantage Pro 2 weather station with a fan aspirated radiation shield. No that’s not my home in the picture. Davis weather stations are highly regarded as professional quality, with NIST traceable accuracy.

As good as the hardware is, meteorological measurement accuracy is largely affected by the siting of sensors and the geography of the surrounding terrain. I have tried to mount my station in the optimal location given the constraints of my property, but any such mounting will always be a compromise. In its current configuration, the anemometer for my station is located on a mast at a height of 25 feet (which it shares with a tri-band VHF ham radio antenna), mounted to the gable of my garage roof. The thermometer, humidity sensor, and rain collector are mounted near the bottom of that mast at a height of 15 feet.

Compromises Due to Location

My yard is surrounded by very tall mature trees. Because of this, even at 25 feet, I suspect my anemometer provides wind values that are too low, compared to a sensor sited in the open. Nonetheless, I believe it provides an accurate measurement of the actual wind affecting us on the ground, even if it isn’t meteorologically perfect. Additionally, the main roof of my house is nearby and the anemometer is barely higher than that roof, so I suspect winds from the south or southwest will be measured inaccurately. Fortunately, the wind around here rarely blows from the southwest.

Because it’s mounted on the roof of my garage, the temperature sensor is subject to inaccurate readings due to the solar heating of the nearby roof materials. I believe I have minimized this effect as much as practical because:

  1. The sensor is mounted in a radiation shield. Radiation shields are designed to reduce the effects of re-radiated heat on temperature measurements.
  2. The shield is fan-aspirated. This means that air is drawn through the shield and over the sensor 24 hours a day by a fan. This should help to further reduce the affects of the heating of air from the nearby roof.
  3. I’ve sited the sensor on the East side of my home, so that it is near a structure that receives direct sun only in the morning hours and not when the sun is the most intense.

Only time will tell if my efforts work.

Accuracy of Measurements

Because weather measurements are so subject to local variation, true reference measurements are nearly impossible to obtain. However, because disbursed readings from private weather stations can add valuable information to official weather forecasts and weather records, the National Weather Service instituted the Citizen Weather Observer Program (CWOP). Their mission, from the CWOP website:

The Citizen Weather Observer Program (CWOP) is a public-private partnership with three main goals: 1) to collect weather data contributed by citizens; 2) to make these data available for weather services and homeland security; and 3) to provide feedback to the data contributors so that they have the tools to check and improve their data quality. In fact, the web address, wxqa.com, stands for weather quality assurance.

I have made my data available to the CWOP program since May of 2006 under the station identifier AS792. All of the data I collect is subjected to a series of quality control checks and statistical algorithms to determine whether the values are likely to be accurate or not. You can see a quality summary of the current day’s reports at this page.

In addition, a more complete summary of my station’s performance over time is available at http://weather.gladstonefamily.net/site/AS792. Finally, a comparison reference to other stations is available at http://weather.gladstonefamily.net/cgi-bin/wxqual.pl?site=AS792.

Transmission of Measurements

Vantage Pro 2 Console

Vantage Pro 2 Console

Measurements are collected wirelessly from the sensors by a Davis Vantage Pro 2 console. This console records the values and then forwards them to a dedicated weather server via a Davis WeatherLink USB data logger.

The server is an AmbientWeather Weather Hub 2 server which is directly connected to my wired home network. The Weather Hub 2 is essentially a version of the excellent MeteoHub software, written by Boris Pasternak, ported to a SheevaPlug platform. For many years (from 2006 – 2010) I ran a variety of dedicated PCs to upload data. But I’ve found the WeatherHub to be an optimal solution because:

The WeatherHub 2

WeatherHub 2

  • The SheevaPlug uses barely 5 watts of power and generates almost no heat. My dedicated PCs warmed the room they were in and used several hundred watts just to run.
  • MeteoHub is a full-featured software program designed specifically for this task.
  • On a SheevaPlug, MeteoHub runs on a version of Debian Linux, which is known for its stability and reliability.
  • A dedicated system means that no other programs interfere with the transmission of weather data. There is no chance that other use of the computer will interrupt the system.
  • The whole thing is a few inches long and it tucks neatly out of the way.

Transmission Reliability

I strive to ensure the best reliability that I can. It is not lost on me that I (and others) would most like to see my data when the weather is at its worst. And of course that is when it is most difficult to keep a system like this running. But, to ensure a minimal disruption in the event of severe weather, I have taken the following steps:

  1. My whole house is protected by a 12 KW backup generator. It responds to power outages within 60 seconds and can run for days on my existing fuel supply. Indefinitely if I can keep the propane flowing.
  2. My Internet connection is provided by Verizon FiOS. During our most recent natural disasters (Hurricane Irene and the Snowtober snow storm), I didn’t lose connectivity for a single second. I had no electricity for 4 days, but never lost cable or Internet. That’s impressive reliability.
  3. The WeatherHub and the entire network infrastructure in my house is protected by an uninterruptable power supply to bridge the time between a power failure and the time when my generator takes over.
  4. I have a cellular plan with unlimited data and the ability to turn my phone into a wireless hotspot. This I can switch the data transmission over to a PC connected to the cellular network via WiFi in a matter of minutes.
  5. I am a licensed amateur radio operator (callsign = W1REH) and I can always fall back to wireless transmission of the data via APRS.

So, one way or another, as long as I am not busy worrying about other things, I will keep the data flowing.

Reporting Outlets

Data from this weather station is shared by a variety of networks. The ones I am aware of are listed below.

Weather Network Description Identifier Link to Data
Weather Underground The Weather Underground is the largest outlet for personal weather station data and among the best sites for integrating personal data with other forecast sources. KMANORTH12 http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KMANORTH12
Citizen Weather Observer Program (CWOP) CWOP is a program of the National Weather Service for collecting and quality checking data from personal weather stations. AS792 http://weather.gladstonefamily.net/site/AS792
Automatic Position Reporting System (APRS) APRS is a protocol used by amateur and other radio operators for reporting geographic position and data (such as weather observations) via radio or the Internet. It is the system used by CWOP to collect data. W1REH http://www.findu.com/cgi-bin/wxpage.cgi?call=w1reh&last=240
PWS Weather PWS Weather is another network dedicated to personal weather stations. MANORGRAF http://www.pwsweather.com/obs/MANORGRAF.html
NOAA MesoNet MesoNet is one of the products resulting from the CWOP program. Maintained by the University of Utah AS792 http://mesowest.utah.edu/cgi-bin/droman/mesomap.cgi?state=MA&rawsflag=3
NOAA Meteorological Assimilation Data Intake System (MADIS) MADIS is yet another product of the CWOP program. It is the source of large, quality checked weather data for researchers. AS792 https://madis-data.noaa.gov/sfc_display/
NOAA MesoWest Another version of CWOP data maintained by the Western Regional NOAA Headquarters. AS792 http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=mtr&sid=AS792&num=48

Sources

I would like to provide a special thanks to AmbientWeather.com. They are the source of all of my weather station hardware from the sensors to the server that uploads the data. Their prices are the best around and their service is great. I have been buying from them since I deployed my first Oregon Scientific weather station in 2006 and they were the only source I considered for my latest upgrade. I recommend them highly.

  1. October 31st, 2015 at 05:13 | #1

    Davis manufactures very high quality weather stations, but the cost is little higher than other brands. Rest of the thing is really good.

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