Weather Station and Data Monitoring - Details

Components of a personal weather station include (1) a sensor array that is installed on the roof of a building or on a standalone pole and (2) a base station or console that receives the data from the sensor array. The environmental data sensors in the array measure collect and store information about temperature, humidity, wind speed and direction, precipitation, barometric pressure, solar radiation, and air quality. The sensor array is powered using embedded solar panels, along with rechargeable batteries that are charged by sun during the day and provide power to the sensor overnight. Data from all the sensors are transmitted to the station tablet or console and are stored as a small text file (using a microSD card) which holds months or years of data. In the past, weather stations would write the data to a local computer, and the data would then have to be uploaded to a system to be included in weather data networks.   Modern weather stations, are connected to the internet, using data networks such as Ambient Weather or Weather Underground. The EcoCasa weather station is connected to a weather data portal and to the “Weather Underground” network.

Outdoor Environmental Conditions. A thermometer is used to measure exterior temperature, and is typically based on either a thermocouple (which measures voltage generated by the difference between the measured temperature and a reference temperature) or a thermistor or probe (both of which measure resistance and how that resistance varies based on changes in temperature). Humidity is measured by a hygrometer and uses a capacitor to monitor water molecules in the air. Both temperature and humidity are used to calculate the dewpoint, the temperature to which air must be cooled to become saturated with water vapor. A barometer measures barometric or atmospheric pressure (the pressure within the atmosphere of Earth) and uses differences in pressure to generate voltage that corresponds to the barometric pressure. The cup anemometer measures wind speed, while the wind vane measures wind direction, and the voltage output of the spinning cups (and vane direction) are converted into wind speed and direction. The weather station rain gauge uses a small funnel that feeds into the tipping bucket, which records a unit of precipitation each time the bucket fills and empties – with a resolution of approximately 0.01 inches (or 0.254 mm). The sensor array also includes a small solar sensor to measure approximate solar radiation. There is also a separate air quality sensor that is powered by both solar (primary) and battery (backup) that connects to the base station, and records particulate matter data. All of these data are gathered at reported on the website and in the data portal at 5 minute intervals.

Indoor Environmental Conditions. The EcoCasa weather station also includes a separate sensor that is located inside the EcoCasa, at a location that is a good representative interior temperature.  This additional sensor is an important comparison tool for monitoring how interior and exterior temperature and humidity vary over the course of a single day, or across weeks, months, or even seasons. This helps demonstrate the insulating capacity of the EcoCasa and how daytime temperatures are warmer on the inside compared to the outside during cooler months, but that daytime temperatures on the inside are cooler than outside during warmer months.

Why gather data using a personal weather station?

Official weather stations (such as at an airport or other official monitoring location) include very precise measurements with expensive instruments, but temperature and especially precipitation can vary considerably over relatively short distances. A personal weather station captures data that is specific to the structure where the station is located. One example of a network that uses data collected from personal weather stations and other rain gauges, is RainLog – a network of citizen science precipitation monitoring, where people submit daily precipitation data, which allows for a more complete understanding of how precipitation varies across a city or region.

What can we do with data from personal weather station?

The data from a single weather station can be a more accurate representation of neighborhood weather conditions than official stations that might be miles away. Multiple neighborhood weather stations can fill in gaps where no data exist and help us better understand precipitation and temperature patterns and how they vary from neighborhood to neighborhood. We can also use these data to assess the role that weather conditions might have played in times of temperature extremes or heavy precipitation and flooding.

How do personal weather station data compare to official stations?

If conditions are consistent across a region, a personal weather station will record similar measurements to an official station, limited by the accuracy of the sensors. However, in cases where conditions are not consistent across a region, personal weather station measurements can fill in gaps in data and illustrate small scale weather patterns. Data from the personal weather station do not always match data from the official stations, and highlights what we can learn from comparing official data to other weather stations in the region.

Weather data vs. solar PV data

The data from the weather station help demonstrate the impact that weather variability can have on solar production. On a normal sunny day, considerable and consistent solar energy is produced, but on days with afternoon thunderstorms (such as during the monsoon), the initial solar production may be steady and increasing but become inconsistent in the afternoon.  On very cloudy days, the solar production is reduced considerably, although on days with intermittent clouds the amount of solar energy produced is still high. Data such as these can help people determine when and how a solar PV system would function at their home or business.

How do weather data help us understand different seasons?

Seasonal and Annual graphics of temperature and precipitation demonstrate the way seasons in the US-Mexico borderlands vary over the year.  Winter is characterized by cooler temperatures and lighter but more sustained rainfall, when it does rain at all. Given its semi-arid climate, the region is characterized by relatively dry conditions. With spring comes a gradual decrease in precipitation and an increase in temperature, and there tends to be more wind during this time of year. Summer starts out very hot and dry, with variability in the onset of the monsoon, which brings intense precipitation, increased humidity, and slightly lower temperatures. With fall comes a gradual decrease in temperature and precipitation, although the end of the monsoon overlaps with tropical storm activity from the Eastern North Pacific, which can extend the wetter periods until late fall when the region typically dries out. A look at the annual temperature and precipitation for various locations around the region demonstrate the variability in the US-Mexico borderlands region, but this region is well known for relatively low annual rainfall totals, and relatively high average temperatures.

What other kinds of data does this weather station collect?

The weather station at the EcoCasa also collects data on wind speed and direction, barometric pressure, solar radiation, and air quality (particulate matter 2.5 microns in diameter or greater; PM 2.5). Wind speed and direction vary over the course of the day and also change by season.  Data from the weather station at the EcoCasa highlight the current conditions and how they change over time.  Graphics from the U.S. National Weather Service (called a wind rose) demonstrate the long-term average wind conditions based on years of data.

The EcoCasa weather station includes a simple solar radiation sensor, which provides a rough estimate of the amount of the radiant energy emitted by the sun that is reaching the sensor.  The solar panels on the EcoCasa roof generate more detailed solar data, but the measurement of solar radiation allows for direct comparison to the amount of solar energy produced. This measurement can also be understood as a proxy for the amount of cloud cover in the sky during daylight hours, with higher solar radiation measurements on sunny days, lower measurements on cloudy days, and measurements of zero overnight.

The EcoCasa weather station also has an add-on air quality monitor that measures particulate matter (PM 2.5) in the air. While not as accurate as the sensors used by state and federal government agencies, it does provide a rough estimate of one measure of air quality near the EcoCasa and allows for comparisons to the official air quality measurements. The EcoCasa air quality sensor could highlight neighborhood air quality issues that may not show up on other sensors located further away.  We can also compare other data, especially wind, to help understand sharp increases in PM 2.5, which are frequently seen during strong winds. In northern Sonora and southern Arizona, rapidly developing monsoon storms create walls of wind (called outflows). These are large enough that they are visible in radar graphics and the air quality data, given the increased levels of dust and debris in the air. Data from the PM 2.5 sensor can also track longer term trends such as increased particulate matter during the winter when household fuels and automobile exhaust are trapped by inversion layers.

How much does a weather station cost?

A simple rain gauge might cost less than ten dollars, while some internet connected weather stations can cost over 300 dollars. The benefit of the more expensive systems is they are connected to larger data networks of other weather stations, and the data are automatically transmitted to these networks over the internet. But a simple rain gauge and thermometer are all you need to record the weather data at your house!

Benefits 

  • A local weather station is able to see live weather data from a localized weather station and compare local data to other official stations
  • The weather station can submit weather measurements to other data networks to see the weather in other neighborhoods or regions
  • Long term data monitoring allows for comparisons to long term averages (climatology) to identify if there are any changes

Limitations 

  • The station is solar and battery powered so if the battery runs out and the sun is not out then the apparatus will not function
  • If station is not connected to internet, data will not be sent. However, there is a SD card backup so data will be accessible after a manual backup. 
  • Only records data that it is designed to monitor 
  • The sensors included in personal weather stations are not as accurate as professional/official weather stations used by governmental weather services

Educational Activities

  • Download weather station data (here) and solar energy production data (here) and identify the role that different weather events play on solar energy production

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