The Daring Book for Girls - Andrea J. Buchanan [32]
Nimbus clouds, the rain clouds, can have any structure, or none at all. If you’ve seen the sky on a rainy day and it looks like one big giant grey cloud, you’ll know what we mean.
WEATHER VOCABULARY
Air pressure
Here’s a fun fact: air is actually a fluid. Like other fluids, it has internal pressure due to the force of Earth’s gravity. Measured at sea level, the air weighs 14.7 pounds per square inch. Air pressure gets lower with increasing altitude.
Alberta Clipper
A fast-moving snow storm originating from the Canadian Rockies and moving quickly across the northern United States, bringing with it gusting winds and chilly Arctic air.
Barometer
An instrument measuring atmospheric pressure, which can predict weather changes.
Chinook
A type of warm, downslope wind in the Rocky Mountains, usually occurring after an intense cold spell, and capable of making the temperature rise by as much as 40°F in a matter of minutes.
Humidity
The amount of moisture in the air. You’ve probably heard the expression, “It’s not the heat, it’s the humidity”—meant to convey that the oppressive moisture in the air is what makes hot weather so uncomfortable. But even in the driest, hottest desert, there is always some water vapor in the air. There are two ways to measure humidity: Absolute humidity and relative humidity. Absolute humidity is the percentage of moisture actually present in the air, while relative humidity is absolute humidity divided by the amount of water that could be present in the air. Relative humidity is what people are complaining about when they say, “It’s not the heat, it’s the humidity”—because relative humidity indicates the amount of sweat that can evaporate from the skin.
Mean Temperature
The average of temperature readings taken over a specified amount of time.
Wind
Wind is the air in natural motion, a current of air moving along or parallel to the ground. We can feel the wind, and see the effects of wind, but we can’t see the wind itself—except as it appears in meteorological pictures, as in the swirling spirals we see on weather maps when a hurricane is present. The way the wind blows depends on the atmosphere around it: in the presence of high and low pressure, the wind blows in a circular pattern, clockwise around a high pressure cell and counterclockwise around a low.
FAMOUS POEMS ABOUT WEATHER
Who has seen the wind?
by Christina Georgina Rossetti (1830-1894)
* * *
Who has seen the wind?
Neither I nor you:
But when the leaves hang trembling
The wind is passing thro’.
Who has seen the wind?
Neither you nor I:
But when the trees bow down their heads
The wind is passing by.
Fog
By Carl Sandburg (1878-1967)
* * *
The fog comes on little cat feet.
It sits looking over harbour and city on silent haunches and then moves on.
I Wandered Lonely As A Cloud
by William Wordsworth (1770-1850)
* * *
I wandered lonely as a cloud
That floats on high o’er vales and hills,
When all at once I saw a crowd,
A host, of golden daffodils;
Beside the lake, beneath the trees,
Fluttering and dancing in the breeze.
Continuous as the stars that shine
And twinkle on the milky way,
They stretched in never ending line
Along the margin of a bay:
Ten thousand saw I at a glance,
Tossing their heads in sprightly dance.
The waves beside them danced; but they
Out did the sparkling waves in glee:
A poet could not but be gay,
In such a jocund company:
I gazed and gazed but little thought
What wealth the show to me had brought:
For oft, when on my couch I lie
In vacant or in pensive mood,
They flash upon that inward eye
Which is the bliss of solitude;
And then my heart with pleasure fills,
And dances with the daffodils.
The Cloud
By Percy Bysshe Shelley (1792-1822)
* * *
I bring fresh showers for the thirsting flowers,
From the seas and the streams;
I bear light shade for the leaves when laid
In their