BBC Weather Watchers Guidance

Transcription

1 BBC Weather Watchers Guidance

2 1) Becoming a Weather Watcher Sharing our interest in the weather Fun, interesting and educational Accessible to anyone Engage with others Deepen our understanding about the weather Introduction to digital skills Share content and local information with BBC audience

3 2) Current weather choosing the right weather symbol Sunny Sunny Intervals Light Cloud Heavy Cloud Drizzle Sunshine & Showers Heavy Showers Light Rain Heavy Rain Thunderstorm Thundery Showers Sleet Showers Sleet Light Snow Heavy Snow Showers Showers

4 2) Current weather choosing the right weather symbol Light Snow Heavy Snow Hail Showers Hail Fog Hazy Mist Hail showers Heavy Snow Snow Showers at Night at Night at Night

5 2) Current weather choosing the right weather symbol Sleet Showers Thundery Showers Heavy Showers Light Showers Partly Cloudy at Night at Night at Night at Night at Night Clear Night

6 2) Current weather choosing the right weather symbol

7 3) Instrumentation and siting Temperature (including maximum and minimum) Humidity Rainfall Snow depth Wind speed and direction Pressure Automatic weather stations Visual observations

8 Air Temperature What instrument do we use? Simple thermometer can be read at any time of the day Max-min thermometer usually read at same time each day Digital thermometer - can be read at any time of the day. Alternative options? How do we use it? All observations should be in degrees Celsius (ºC) Measure away from large buildings, trees etc. Thermometers must be kept out of direct sunlight Hang on a north-facing wall or (preferably) in a ventilated white box so that sun is reflected away, yet air can pass freely over the thermometer. Simple Thermometer ( 1 3) Digital max-min Thermometer 10 Traditional max-min Thermometer 10 UK Hottest: 38.5 C Faversham, Kent UK Coldest: C Braemar, Eastern Grampians

9 Air Temperature The Weather Watchers sliding scale

10 Humidity The amount of water vapour present in the air is known as the humidity. Relative humidity (RH) - amount of water vapour in the air as a percentage of that required to saturate it completely. RH will be 100% in fog, but might be as low as 30% on a dry summer s day. Digital hygrometer 10 What instrument do we use? There are several different types of instrument, such as simple wet-dry bulb thermometers, but the simplest to read is the digital hygrometer. How do we use it? Hygrometers must be protected from direct sunlight using some form of screen which still allows air to pass over the instrument freely.

11 Rainfall amount The total depth of rain which has fallen over the past 24 hours. What instrument do we use? A rain gauge which has a funnel collector to prevent the rain already in the gauge evaporating. A straight cylinder with flat bottom, such as a tin can. Rainfall depth can then be measured with a ruler. How do we use it? Put the rain gauge in as open an area as possible, away from obstructions (houses, trees). To prevent it blowing over, dig a shallow hole in a lawn and push the rain gauge into it, or put into a large plant pot. Rainfall is manually measured at the same time each day and is reported in millimetres (mm) for the past 24 hours [mm/hr is reported for automatic weather stations] Rain gauge with collecting funnel 15 Open rain gauge 3-5 Make your own Snow depth Can be simply measured by sticking a ruler into the snow, away from drifts. Measure in centimetres (cm).

12 Wind speed and direction Wind speed is the speed of the air moving past us. Wind direction is the direction which the wind is coming FROM. What instrument do we use? Wind speed is measured with an anemometer. Wind direction can be measured with a wind vane or windsock Blowing bubbles and using a compass can also be helpful in assessing wind direction. Windsock 1-3 How do we use it? Measure wind in open space and as high up off the ground as possible. The anemometer should be held up in front of you at arms length, facing into the wind. We report the speed in mph. The windsock can be put on a pole (e.g. bamboo) Report the direction the wind coming from one of eight compass points, i.e. N, NW, W, SW, etc. Propeller anemometer 10

13 Pressure Pressure is due to the weight of the column of air above us pressing down. Pressure varies with the type of weather. What instrument do we use? Barometer Digital sensor (used in AWSs) How do we use it? Pressure can be measured indoors with the barometer hanging on a wall. Tap the barometer gently before reading as the needle sometimes sticks. We use units called hectopascals (hpa) or millibars (mb) Calibration Wait for a calm day (i.e. high pressure system) then look at the pressure at your location on the BBC weather website, then alter your barometer to read this value (turning a small screw at the back). Barometer 15 Feeling under the weather Headache and joints ache drop in air pressure Nausea build up in static in the atmosphere Heat stress

14 Automatic wireless weather station You can buy an automatic weather station which transmits data to a console indoors and displays it. You can read these observations directly from the indoor display console and then report them manually on the BBC Weather Watchers website. Wireless temperature and humidity station, showing indoor console and (right) outdoor sensors. 20 wind speed and direction rainfall temp and humidity Full automatic wireless weather station and indoor display console 60-90

15 Visual observations Visibility This is how far you can see in daylight. If you can see less than 1000m report as fog. If you can see more than this but less than 4km, report as mist. Snow/sleet/hail falling Type of precipitation Report this as heavy, medium or light snow, or sleet or hail. Cloud amount Estimate how much of the sky is covered in cloud. Use eighths as a unit, so if the sky is half cloudy report 4/8 (four eighths), overcast is 8/8. Any small cloud in a clear sky is 1/8. Cloud type You can identify the type of cloud from the chart supplied or using the online key to clouds.