Ideas and lesson plans to enhance the learning and teaching of weather studies in schools.
By Dr Geoff Jenkins
It goes without saying that projects based on the weather must teach the student something about the weather. Otherwise, they are not worth doing. Weather happens out of doors, so it is obvious that weather projects must involve some outdoor activity, and preferably quite a lot. Weather projects should not be done from textbooks only, unless there are good reasons (e.g. disability). Similarly, crunching through a pile of weather statistics that have been obtained elsewhere or not by the student personally may be a good way to learn about statistics but gives little real insight into the weather.
Projects based on Weather Station recordings
Making routine observations with a school weather station is not just an instructional activity in its own right. Once a set of measurements has accumulated over a period of two or three months (the longer the better), this database can be used for a range of different projects.
Instrumental measurements that can be made with a school weather station include (in order of cheapness): temperature (particularly daily maximum and minimum), rainfall, relative humidity, light level, pressure and wind speed. Simple visual observations include wind direction, visibility and cloud amount/type. See our document on simple_weather_instruments, which describes some useful instruments and techniques.
Projects that use collected data fall into several categories:
- Describing the climate of the location for as many weather elements as possible. This is best done with data for two or more years, so that year to year differences can be explored. In some years, days in December can have higher maximum temperatures than days in June!
- Comparison of the school's collected data with another set of data, taken from another school or a local 'official' weather station. This is particularly interesting during a time of unusual weather, e.g. a period of very low temperatures or intense rain.
- Comparing the records of two or more elements, to see if any relationships exist. This can be done in general qualitative terms or by using quantitative correlation techniques. Weather elements that might show interesting relationships (at least over certain periods) are:
- Pressure and rainfall
- Wind direction and rainfall (try using 'wet' and 'dry' day wind roses)
- Wind direction and temperature or humidity
- Wind direction and visibility
- Wind direction and wind speed
- Wind speed and minimum temperature
- Cloud cover (early morning) and minimum temperature (or daily range, i.e. difference between maximum and minimum)
The project should not only demonstrate a link but also try to explain possible reasons for it.
- Weather records can often be used in association with other measurements or observations, e.g. plant growth, or number of pupils with illnesses.
Find out how air pressure changes as you go up in the atmosphere, by taking a barometer up a hill or a tall building. Measure pressure before and after, to correct for any variation of pressure with time.
Measurements of temperature out of doors are cheap and easily made using standard liquid-in-glass thermometers, simple bimetallic thermometers or electronic thermometers. The latter use thermistors as sensors and usually have LCD readouts. They are clear and can be read with greater precision than the other types. However, precision must not be confused with accuracy. Indeed, electronic thermometers often have poorer accuracy than other types of thermometer. But in many projects absolute accuracy is not very important.
Measurements are best made away from the influence of buildings. A school playing field is ideal, or even a large playground. Some form of shield is mandatory, to protect the thermometer or thermistor probe from direct sunlight by day. After dusk, a 'radiation screen' is not so important but is still useful to reduce the effect of infra-red radiation from the ground.
- Record the way in which outside temperature varies over the course of a day (i.e. 09h to 16h). Is the variation the same on cloudy days as on clear days? Is the variation the same close to the ground as a few metres above the ground?
- Record the rapid changes of temperature that occur around sunrise or (probably more conveniently) sunset, by taking measurements every five minutes for an hour or so. Again, look at differences between cloudy and clear nights, and between calm and windy nights.
- Look at the temperature difference between two heights, one close to the ground (say 2 to 5 cm) and one at 2 to 3 metres. How does this temperature gradient change between day and night, cloudy or clear, calm or windy? What does this tell us?
- Measure the temperature below the ground. Contrast the diurnal variation (on the same day or night) with that in the air. Look at this variation at several depths - say 5 cm, 10 cm or 20 cm - and below different surfaces, e.g. grass or bare earth.
- How do buildings influence temperature by day and by night? Make measurements out in the open and gradually nearer to buildings, and make them in courtyards, passages, etc.
- As an extension of the above, investigate how whole towns and cities affect air temperature. This can really be done only with staff assistance, by driving through a town or city from one side to the other. An electronic thermometer with the probe mounted on the top of the radio aerial is ideal. A cold, calm, clear night gives the best 'urban heat island' effect - but try it on a cloudy, windy night for comparison.
- If you have a suitable instrument, see how the wind speed varies from one averaging period (say, 10 seconds) to the next. How does this variability depend upon the averaging period?
- Investigate the way in which wind speed depends upon height above the ground. Measure at, say, 30 cm, 1 m and 3 m. Simple flap-type anemometers or ventimeters can be used for this. How does the wind speed profile differ over different surfaces, e.g. smooth grass, rough pasture, heather or bracken?
- Find out how the flow of wind is affected by buildings, by measuring wind speed well upwind, around the buildings and downwind of them.
Cup anemometers (bottom and centre) and ventimeters (top)
- Investigate the way in which rainfall accumulates during a long period of rain as a warm front moves across the area, by checking the rainfall every 30 minutes or so. Contrast this with rainfall rates in shorter-lived showers.
- How big are raindrops? Collect them on coloured blotting paper and quickly measure their sizes. Calibrate the blotting paper by dripping water droplets of known size/volume onto it. How different is the size distribution of raindrops in showers compared to that in drizzle?
- Look at the sheltering effect of trees and buildings by putting down a network of simple rain collectors (e.g. jam jars) and measuring the accumulated volume in each after a shower or longer period of rain. Relate the result to wind speed and direction.
- By leaving out a dish of water, look at how fast the water evaporates, between, say, 09h and 12h, or between 12h and 15h. Relate the amount of evaporation to weather elements.
Simple 2-part rain gauge with measuring cylinder
Projects using humidity measurements
- Contrast the relative humidity measured first thing in the morning with that at midday and in mid-afternoon. Why does relative humidity change on days when there is no change in the weather, e.g. on a clear, fine day?
- Why does seaweed change from brittle to flabby?
- Some types of weather instrument can be constructed by students aged 14-16. However, as with the caution above about statistics-based projects, make sure that constructional projects teach students about some aspect of the weather, not just about electronics or mechanical engineering.
Automatic Weather Stations
Automatic weather stations An automatic weather station usually consists of a number of outdoor weather sensors which communicate with an LCD display unit indoors, which can in turn often be linked into a PC to store and display data. Once the preserve of the professional, or at least the rich amateur, recent advances in technology and production mean that simple (sometimes called "family" or "hobby") weather stations are well within the reach of most amateurs and schools. The price will depend upon how many weather elements are measured; for example, just outdoor temperature (including maximum and minimum) might be around £15, just rainfall around £30, temperature and humidity around £40. Even a station which displays the six main weather elements (temperature, humidity, wind speed and direction, rainfall and pressure), can now be bought for about £100. In addition to giving the basic measurements, quite often the display unit will also calculate quantities such as wind chill, dew point, etc. Sometimes it will also give a weather forecast, though based as it is on only local conditions, this must be taken with a big pinch of salt!
The link between the instruments outdoors and the display inside may well be by wireless, removing the need to feed a wire into the house or school, athough the range will be 100m at best, and often well below this. At the sort of prices quoted above it is not surprising that the manufacturer does not give details of accuracy, so this might be quite modest, although perfectly adequate for many applications in teaching or for the interested amateur. (Note that precision is often quoted, which is very different; for example, outdoor temperature might be displayed with a precison of 0.1°C whereas its accuracy may be no better than a degree or more). A professional automatic station reading six elements may well cost £500 or more, but you will get the benefits of a known accuracy for all the measurements, and probably higher reliability and longer lifetime.
There are many advantages to an automatic weather station. Weather observations can be made more quickly and conveniently, which might mean they can be taken four times a day in schools instead of just once. The sensors can be placed well out of the way and reduce the chances of vandalism - and (in the case of wind measurements, for example) in a better exposed location than would be possible with hand instruments. If a PC link is available this this opens the door to using the data for all sorts of projects, from simple averaging ones to looking at correlations between different measurements such as wind direction and temperature - although of course manual readings could be entered into a PC and the same sort of projects undertaken. The main disadvantage of an automatic weather station is that it removes the observer from the real elements being measured, and thus the experience of what minus 5°C temperatures or 30 knot winds feel like, is lost. And actually seeing the liquid in a thermometer contracting in cold weather, or pouring rain from a collector to a smaller-diameter measuring cyclinder, for example, naturally leads to discussion of these topics and the maths and physics behind them.There is also some satisfaction in having braved bitter winds or lashing rain to get the results!
The RMetS does not actually recommend specific instruments or manufacturers, but you can find instrument providers amongst our Corporate Members.