Head In The Clouds: A Go Play, Go Learn Challenge
The next ‘Go Play, Go Learn challenge‘ on ‘Nerd In The Brain‘ was to turn our attention to the clouds (the last one was insects.) I decided to spend a bit of time learning about them and also took some photographs while keeping note of the weather. During the short space of a week I photographed a variety of clouds. The weather was mostly calm and warm, but there was the odd spot of rain and even a small thunderstorm at the end.
Clouds And The Weather
Clouds are really important as they bring rain and offer shade from the sun. Knowing how to identify them can also be an indicator as to what to expect from the weather (incredibly useful for anybody that enjoys outdoor activities.) It’s in a loop, where the right conditions affects the formation of clouds, but in turn the clouds affect the conditions. They have an impact on the climate by reflecting incoming light from the sun or radiating back heat rising from the surface.
How Are Clouds Formed
During the morning the sun heats up the earth. Throughout the day different areas heat up at different rates. Thermals (up-drafts of warm air) start to rise and water evaporates from rivers and lakes. As the air rises to where the pressure is lower it expands and cools, causing condensation to occur (when water changes from gas to liquid.) There are usually other particles such as dust for the droplets to hold onto and they are light enough to float in the air. Once the droplets are big enough they fall to earth as rain and the process starts again. There’s an interesting experiment you can try to see how they are created, using a bottle, warm water and matches.
There can be a variety of different types of clouds in the sky at any one time and they’re always changing. There are three different levels where clouds can appear, high (> 20,000 ft), medium (6,500ft – 20,000ft) and low (< 6,500ft.) The higher clouds often have a different shape and look as they are formed from ice crystals as opposed to droplets. There are 10 main groups (known as genera) overall.
|Stratus||Low||One of the lowest appearing clouds, sometimes found at ground level in the form of fog. It is a featureless uniform grey or white, consisting of layers or patches with fuzzy edges.||Often accompanied by drizzle or snow and during overcast conditions. It can form from Stratocumulus, indicating a prolonged continuation of cloudy weather and drizzle. If they appear thickly in the night and morning, they will usually disappear later on in the day.|
|Cumulonimbus (also known as thunderclouds.)||Low||Heavy and dense plumes that tower into the sky. They have flat dark bases.||Associated with extreme weather. Is a sign of atmospheric instability, capable of producing lightning and other severe weather.|
|Cumulus||Low||Fairly common, usually forming over land. They are big and fluffy, in a cauliflower shape with distinct edges. They are shaded, appearing white when lit by the sun.||They can indicate that the atmosphere is unstable at the altitude where they are found. They usually appear during fair weather, but can quickly change to rain (usually if seen at midday.) The showers they produce are light.|
|Stratocumulus||Low||Clumps of cloud varying from bright white to dark grey. Can be joined together or patchy with gaps in-between.||They can appear in all types of weather. In winter they may indicate high pressure and stable conditions. If there are expanding patches of blue sky it may mean the weather is improving. Rain rarely occurs, but they can turn into Nimbostratus clouds.|
|Altocumulus||Mid||Small clouds, forming in rounded layers or patches – known as cloudlets. Can be white or grey (unlike Cirrocumulus,) and shaded by the sun. They are made up of ice crystals as well as droplets.||Found in settled weather, usually followed by a humid climate or thunderstorms. Commonly seen in the Summer.|
|Altostratus||Mid||Large clouds that spread over wide areas. They are thin and featureless with a blue or grey colouring. Sometimes the sun can shine through, although it doesn’t cast any shadows (unlike Nimbostratus.) Made up of a mixture of ice crystals and water droplets.||May indicate the coming of a storm or continuous rain. They produce light precipitation, and may eventually thicken into rain bearing Nimbostratus.|
|Nimbostratus||Mid||Dark grey or bluish featureless layers covering most of the sky. May have ragged edges or small fragments beneath the main cloud. Thick enough to block out the sun.||Associated with dark gloomy days. Frequently accompanied by persistent rain or snow (not thunder or lightning like Cumulonimbus.)|
|Cirrus||High||Wispy and delicate. In the day they are a brilliant white, but during sunset or sunrise they may reflect different colours such a red, orange and yellow. They are also fast moving, but may not appear so when viewed. Made up of ice crystals.||Cirrus clouds usually indicate a change in weather over the next 24 hours. A few irregular patches may mean the coming of dry sunny weather, but a lot may be warning of a coming storm.|
|Cirrocumulus||High||Rare clouds consisting of small patches – cloudlets. Evenly spaced and can take on the appearance of ripples. Made up almost entirely of ice crystals.||May indicate the coming of rain and thunder. If seen in small patches it could also mean the continuation of good weather alongside the odd shower or storm.|
|Currostratus||High||Transparent clouds covering wide areas of the sky. Sometimes they produce coloured rings around the sun or moon that are known as the Halo Phenomena. They can be so thin that the halo may be the only indication that they are in the sky.||Like Cirrus and Cirrocumulus it does not produce rain, but with decreasing pressure may be a sign of bad weather to come.|
My Collected Data
Afternoon – 19°C. 7 mph wind. Humidity 59%. Precipitation 4%. Pressure (hPa) 1012 rising.
Evening – 18°C. 8.9 mph wind. Humidity 52%. Precipitation 2%. Pressure (hPa) 1014 rising.
These are probably Cumulus clouds. It was a very warm and dry day and they are known as fair weather clouds. They also have a fluffy cauliflower shape and are shaded by the sun. They didn’t appear to be very high up either. The sky was mostly clear, but they could be seen throughout the day.
Afternoon – 16°C. 2 mph wind. Humidity 53%. Precipitation 0%. Pressure (hPa) 1018 rising.
Evening – 18°C. 2 mph wind. Humidity 61%. Precipitation 5%. Pressure (hPa) 1018 rising.
The morning and afternoon were similar to the day before, but later on the sky changed to overcast. They look like Altostratus clouds as they are a dull grey in colour, but the light can also be seen shining through in places. There was also no extreme weather to accompany the clouds and it continued to be dry and humid.
Afternoon – 18°C. 11.2 mph wind. Humidity 53%. Precipitation 13%. Pressure (hPa) 1018 falling.
Evening – 20°C. 8.9 mph wind. Humidity 69%. Precipitation 3%. Pressure (hPa) 1017 falling.
The clouds were in small patches covering a large area, with a few gaps in-between. I’m not sure if they are Altocumulus or Stratocumulus as they appear to fit the description of both and can appear in settled weather (it’s apparantly very easy to get the two confused.) I’m leaning towards Startocumulus however, as Altocumulus tend to be made up of smaller patches. The next day the weather also turned rainy which can follow the appearance of Stratocumulus.
Afternoon – 15°C. 13.2 mph wind. Humidity 69%. Precipitation 53%. Pressure (hPa) 1012 falling.
Evening – 17°C. 13.4 mph wind. Humidity 63%. Precipitation 40%. Pressure (hPa) 1011 falling.
Overcast. The clouds seem similar to the Altostratus seen on day 2, but are thicker and darker. Light doesn’t seem to be shining through so strongly either and they were accompanied by light showers. They may therefore be Nimbostratus, which can follow Stratocumulus.
Afternoon – 21°C. 13.4 mph wind. Humidity 64%. Precipitation 2%. Pressure (hPa) 1015 falling.
Evening – 15.1°C. 8 mph wind. Humidity 88%. Precipitation 4%. Pressure (hPa) 1016 rising.
The weather improved from the previous day. There were these interesting wispy patterns in parts of the sky. While they have the appearance of Cirrus clouds, I suspect they could actually be contrails, artificial clouds that sometimes form behind aircrafts (known as Cirrus Aviaticus.) They are formed when the water in jet exhaust mixes with wet cold air and turn into ice crystals. If the air is wet and cold enough the trails can spread out and stay around for a long time. Therefore, they can be an indicator as to the conditions of the region of air where they are formed (they will not form in dry air.)
Afternoon – 18°C. 8.9 mph wind. Humidity 65%. Precipitation 48%. Pressure (hPa) 1018 rising.
Evening – 22°C. 8.9 mph wind. Humidity 67%. Precipitation 2%. Pressure (hPa) 1017 falling.
The sky was fairly clear again with small clumps of cloud. The clouds however, seem to have slightly less form and shading than a distinct Cumulus cloud and so they may be Stratocumulus. When I look closely at the photograph I took in the evening the clouds appear to be less distinct and slightly wispy in texture, but they’re also featureless with a grey bluish colour and so could be Altostratus.
Afternoon – 23°C. 15.7 mph wind. Humidity 72%. Precipitation 54%. Pressure (hPa) 1017 falling.
Evening – 24°C. 20.1 mph wind. Humidity 79%. Precipitation 17%. Pressure (hPa) 1016 falling.
Once again the clouds had very little form and could be Stratocumulus, but there were also a few well defined cauliflower shapes (cumulus clouds) later on. Once again the weather was fine and settled.
The weather was fairly stable throughout the week, with the odd spot of rain. There was also a storm the day after I stopped recording data. Interestingly, the temperature seems to drop suddenly over day 4 when the thick Nimbostratus clouds appeared, covering the sky and blocking out the sun. It then became warmer again the next day when the sky was clearer with sparse cloud coverage. The precipitation also increased during this time and was still higher when the Cirrus Aviaticus could be seen during the morning of the next day.
The temperature drops again between day 5 and 6 when the clouds briefly thickened up again. Overall the humidity and precipitation seems to increase over the week before the storm. I remember on the day of the storm it was very warm and the sky was filled with cumulus clouds that suddenly darkened and grew in thickness – the calm before the storm caused by warm moist air. The pressure also drops around the rainy days, but was higher during the calmer dry days.
Of course, I’m no expert on clouds so I may have made a few mistakes in my attempts to identify them. I usually completely overlook clouds, but have since come to realize what an important role they play. I think it’d be useful and fun to learn how to predict the weather just by viewing the clouds.
- Met Office – Cloud Spotting Guide
- NC State University – How Clouds Form
- ISCCP: International Satellite Cloud Climatology Project – http://isccp.giss.nasa.gov/role.html
- Wiki How – How To Distinguish The Different Types Of Clouds
- Wiki How – How To Forecast the Weather Using Clouds
- Section Hiker – How to Predict the Weather using Clouds
- Weather Online
- Contrail Science – Why do some planes leave long trails, but others don’t?
- Discovery News – How Do Clouds Affect Earth’s Climate?
- how stuff works – Is there really “a calm before the storm”?
- Komo news – How do High Pressure and Low Pressure Affect Our Weather?