These days, there is a growing interest in Ireland's weather and climate and more and more people have purchased their home weather station and started to record the conditions in their own back gardens. Given the wide variety of weather stations on the market at the moment, making the right choice can be quite confusing, some are affordable while others may well be out of reach of your budget but at the end of the day it is your own site, whether urban or rural, and of course your pocket, that will determine the station you eventually purchase.
Here on the IWN we encourage all of our members to report their local conditions on the forum, regardless of their site and station type. Remember, what your station is reading is of interest to everyone and not just you!
For those of you who are interested in purchasing your first weather station, or upgrading to a better model, I hope that this guide will make the process less confusing and steer you through the different types of location you may have to deal with and the different makes of weather station that are most suitable for each particular site type.
This is not an easy topic to cover and forgive me if this is long and boring. It may however be of help to some.
Weather Stations or AWS (Automatic Weather Station)
Anyone, anywhere can have a weather station but you have to ask yourself what exactly to you want from it? Are you just curious to see what conditions are like outside right now with regards to temperature or wind, is it just because you've seen one going cheap and decide to grab one while the goings good or do you really want to get yourself involved in keeping accurate data and records for your area? In fact, buying a weather station can be surprisingly difficult and the answers that you give to these questions will determine the station that best suits your needs
The most common variables we measure from a weather station are air temperature, rain and wind although many more variables can be measured. The most important thing to look for in a station is accuracy; how accurately it will measure the data for your own immediate area i.e. right outside your door.
Air Temperature
When measuring air temperature you will definitely get what you pay for and with some of the budget-priced stations on the market, the radiation shielding can be exceptionally poor. The purpose of radiation shields is to reflect solar radiation away from the temperature/humidity sensors and also to keep a good airflow running over the sensors. With some stations, the radiation shields do not perform well and as a result, the air temp is over recorded. At the end of the day, we want to measure Air temperature and not apparent Solar temperature. There is a huge difference between the two.
For example this is an experiment I carried out while living in a housing estate: -
I had a Davis VP1, a second VP1 temp sensor that was unshielded and a La Crosse brand.
One summer’s morning, I placed all three side-by-side and very quickly the unshielded sensor was measuring 9°C higher than the Davis VP1 and the La Crosse 3°C higher than the VP1. When the unshielded Davis VP1 sensor had its radiation shield replaced, the temperature it recorded quickly came back into line with its shielded counterpart.
The La Crosse however had a different type of shield. Due to its construction, the sensor was virtually enclosed in the housing and had a more restricted air flow, basically creating its own little greenhouse and over-reading the temperature. I stripped the La Crosse sensor down and placed it in Davis VP1 housing and afterwards, the sensor reading dropped to just 0.7°C higher than the Davis readings. This was all due to the better airflow created by the design of the Davis radiation shield. This experiment was carried out 10 years ago and the La Crosse brand has improved its shield since then or so I believe.
(NB: Davis Vantage Pro2 is within ± 0.2 of Standard meteorological equipment which I measure officially along side my Vantage Pro2)
If you are experiencing problems with poor radiation shielding, a simple solution is to move the shielding or housing out of direct sunlight and this will immediately eliminate the problem. Alternatively, some of IWN members have constructed their own louvered Stevenson Screen's and placed the temperature sensor including the housing/shielding inside thus maintaining an airflow and eliminating direct solar radiation. This solution is not for everyone though, some of us will lack the carpentry skills to complete this task and the screen can be expensive to construct.
Rain
Measuring rainfall is usually done from the ground officially from a manual gauge read once a morning. There is more friction at ground level and thus more rainfall is collected. The higher you go, horizontal winds will sweep some rainfall over the gauge and the tendancy for rain to be under recorded due to this. On the AWS, the rain gauge is either attached to the main part of the station including where the thermometers are housed. Some AWS rainfall gauges can be separated and some are separated from the unit itself. To measure the rainfall as accurate as possible, the gauge is recommended to be at 1.2m high with the rest of the unit and at twice the distance from the tallest object. This is not always possible to achieve if you live in an housing estate. With other factors at play, the gauge along with the rest of the unit can be placed at the ambient temperature height above walls or fences to collect rainfall.
Wind speed
Wind speed and direction is measured from an anemometer. The standard aviation height is 10m or close to 33feet high to record wind speed. The higher you go than this, the higher the wind speed as there is less friction. Closer to the ground and below the standard height, more friction from buildings, trees and ground level slow the winds down, so the closer the standard height the better but some buildings and trees in close proximity can be at this height and block wind speed from that general direction.
Some of the AWS like the Davis Vantage Vue have all the instruments attached to one compact unit so your caught out on measuring one of the elements correctly as none of the instruments can be separated. The Davis Vantage Pro2 has 40 feet of line but you can add up to an additional 8 sensors with one being a wireless anemometer transmitter to place the anemometer even further away from the station itself. This is useful if you want to place the anemometer on a telegraph pole or on a chimney but is at extra expense.
The Site
There are two basic types of location - the Urban and the Rural site.
Urban
The most important factor to consider when locating a weather station in an Urban site is the UHI or Urban Heat Island effect and its influence on your measurements, particularly air temperature. An UHI occurs when heat from a town/city or housing estate modifies the air above it, making it warmer than the air in a rural setting. Buildings, housing estates, concrete/asphalt, motor vehicles and even people contribute to the UHI affect. This urban heat build is slow to cool at night and can even artificially raise the environmental temperature during daytime making it higher than in a non UHI area even to within just miles outside the UHI zone.
So, is there any point in owning a station in an UHI area? Yes, why not!! You’re still measuring the environmental temp outside your own door in your own local area and this can be just as fascinating and valid as measuring conditions in an exposed open field. What is important is that you aim to get the best from your station within the UHI.
There are several types of site you can encounter in a housing estate or city/town centre location.
• Back garden with grassy area - (if children/pets permit), site the station away from buildings in and open area at 1.2m over the grass
• Back garden with patio/concrete and some grassy area - Site the station over grass at 1.2m and not over patio/concrete
• Back garden with grass but overlooked with taller buildings - Expose the station as much as possible to an airflow but siting over grass and away from buildings is sufficient
• Back garden with no grass with tall buildings blocking out sun - Raise the station above fence line or wall to record ambient temperature
• Back garden exposed, with patio/concrete and no grass - Station needs to be raised above the standard meteorological height and placed above fence line or above wall to record the ambient temperature
If you are living in an UHI and you can afford it, the most suitable station for your location is a Davis VP2, Vantage Vue or WMR Oregon Scientific. All of these will as it will serve measuring the environmental temperature accurately once sited correctly using the guide above. Less expensive, budget stations such as the Maplin/Fine Offset/Watson varieties would need more care and attention especially in situations like a south-facing garden, surrounded by tall building and exposed to the sun for parts of the day. In situations such as this, these stations will dramatically over record temperature, well above the true environmental range.
Some types of station can have separate sensors. If you have a budget type station, place the sensor in a shaded part of the garden out of direct sun at a height of 1.2m. Even using a simple white sheet of wood with holes in it, blocking direct sun and allowing some airflow through can help temporarily. Also if you can avoid placing sensors on or near walls as all concrete conducts heat eg: placing a temp sensor in the shade on a south facing wall will conduct heat and give off higher readings.
As you can imagine, there are many more types of back garden, and the direction you are facing and the proximity of buildings will all have an effect on your readings but if you stick to the basic principles in the above guide when locating your urban station you won't go too far wrong.
Rural
In a rural setting, you can get maximum exposure to the elements and have the best chance of recording data more accurately providing on the type of station you purchase. With an expensive station, the accuracy is far superior than a budget type station. With a budget station, too much exposure to strong sunshine can also over record temperature and renders the data inaccurate. Following some of the guidelines set out, a simple screen of sorts can help reduce the affects of direct sunshine.
Also of note, hedgerows, trees, walls and fences can also conduct heat even in a rural setting so placing the station as best you can and as far away from these for best results.
What station should I buy
In an ideal world we would all aim to have an expensive, reliable station on an exposed site, but we can't have everything so using the guide above and before spending huge amounts of money on a station, We can categorize stations as
Budget, Less than 100 Euro Watson/Fine Offset etc
Mid range, 100 to 300 La Crosse, some WMR Oregon etc
Expensive, 300 to 1000+ Davis VP2, Vantage Vue and higher range of WMR Oregon etc
• Expensive Station, Exposed Site = Ideal, gives reliable data and your money's worth
• Expensive Station, Housing estate = Good for measuring environmental data. You may have overspent and may not get the full potential of an expensive station but compensated for by adequate radiation shielding for air temp that measures the environmental temp well
• Lesser Station, Exposed site = Good for getting maximum airflow and rain data but inadequate housing/shielding over recording temperatures in prolonged sunshine.
• Lesser Station, Housing estate = Value for less money but needs to be fine-tuned with extra shelter or raised up and out of sun trap to record the ambient temperature, otherwise data will read extra high even above the true environmental range
These are some of the stations around on the market today.
the Huger/Radio Shack/Oregon Scientific WM918/WX200,WMR-918/WMR-968/WMR-928N,WMR100,WMR200,WM-900H,63-1016
the Davis WMII, Wizard III, Grow, Vantage Pro/plus/6161/VP2/Vue etc (with datalogger), supports soil temperature/moisture/leaf wetness and UV/solar (extracted data from logger too)
the ELV/Conrad/Huger WS2000/WS2010/WS2210/WS7000/WS2300/WS2305/WS2310/WS2315/Hyundai WS-05/WS2500PC/WS2510/3600
the La Crosse 2010,2110,2210,2308,2310,2315,2300,WS23XX,WS2350,2500,2510,3600/3610
the Peet Bros Ultimeter 100,500,800,2000,2100 and II
the Maximum Instruments Weathermax (with datalogger)
the Metron UWS 3000-ws
the Rain Wise WS2000/MK III (with data logger)
the Dallas 1 wire weather station (and version 3)
the Texas Inst. WR-25 and variations
the Heathkit ID -5001
the Climatronics Ultrasonic
the Novalynx WS-16 Weather Station
the Capricorn 2000
a ASOS station and a RAWS station
the Weather Hawk /Weather Hawk IP
the Environdata weather master 2000
the Kestral 4000
the Instromet
the Inspeed Vortex anenometer
the Vaisala WXT510/520 ultrasonic station
the HoneyWell TE923/Irox Pro/Nexus USB
the ELV WS500/La Crosse WS550 USB
the OS WMR100,WMS200/200 USB
the IRDAM station via TCP
the WH1081PC/National Geographic/Zephur/Fine Offset/WX-2008,Watson USB station
the new Davis IP data logger (direct connection for Live data)
the Airmar Ultrasonic GPS
the new AAG TAI603B 1 wire station
the new Hobby Boards ADS speed/dir board
the new La Crosse 2810 (via the curdat.lst file updated by Heavy Weather software)
the Weatherwise Pro WS-1080, Solar powered transmitter and the WH3081 with Lux and UV sensors
Please note, some of the stations I have not used personally myself before but some on the forum may have so please ask any questions in this topic or on any of the guide. You can take pics of your site and post up here as pics can best describe your site. Detail it as best you can.
I hope this was of at least some help to potential weather station owners and may have answered some doubts you may have had.
