2.4 - Weather Flashcards
What is a Stevenson screen?
a small weather station that is used to measure local weather conditions
What are some features of a Stevenson screen?
-white (reflects sun rays)
-wood reduces heat conduction/absorption
-air slats (for ventilation)
-raised 1.25m above ground (avoid strong temperature gradients at ground level)
-locked (stops people tampering with equipment)
(WWARL)
Why are thermometers and wet/dry bulb thermometers left inside Stevenson screens?
-makes sure direct/absorbed sunlight doesn’t affect readings (white coating reflects it)
-free flow of air ventilation
-not affected by radiation from ground
-secure from tampering
Where should a Stevenson screen be placed?
-away from buildings/trees (prevents wind blockage)
-on grass, not concrete (it gets too hot otherwise)
-face north in NH (stops direct sunlight when opened)
What does a rain gauge measure? Where is it placed?
rainfall (always in an overflow cylinder in open area)
What does a max. min. thermometer measure? How do you read one?
temperature range (read bottom of markers)
What does a hygrometer/wet dry bulb thermometer measure?
relative (%) humidity (larger difference means lower humidity)
What does a sunshine recorder measure?
hours of sunshine (focused sun burns into a single-use time card)
What does a barometer measure?
air pressure
What does an anemometer measure?
wind speed
What does a wind vane measure?
wind direction
(points in the direction where the wind originates)
Give some advantages of digital measuring instruments:
-more accurate + precise
-easier to read, no human error
-faster to read, saves time
-linked to computer to log data (can be left for longer periods without human monitoring/transferring data)
Give some disadvantages of digital measuring instruments:
-could be damaged by weather
-needs power (limits the location of usage)
-more expensive (don’t say this unless desperate, they are actually cheaper nowadays)
How do you assess cloud cover?
-choose a set time of day and location to check sky
-check the same area of sky every day at that time over several weeks/months
-look up at sky, hold rectangle at arm’s length
-estimate cloud cover in oktas
-cloud types (identify using diagram/chart/book)
-record in table
Describe what a cirrus cloud looks like:
-high altitude
-long, thin and wispy
-made of ice crystals
Describe what a cumulus cloud looks like:
-mid altitude
-white + fluffy
-flat base
-broken up/discontinuous
(if you get cumulus clouds in the morning, there will usually be rain later in the day)
Describe what a stratus cloud looks like:
-low altitude
-grey + fuzzy
-covers most of sky
can also form fog
What are the names of tropical storms in different locations?
-hurricanes (N. America)
-cyclones (India/Australia)
-typhoons (Japan)
What are the formation requirements for a tropical storm?
-need >26°C water (evaporating water fuels storm, usually found near equator)
-need >74mph winds (to be classed as a hurricane on Saffir Simpson scale)
Describe the ideal location for a wind vane:
-high up on a building
-in an open space
-clear from obstructions like a tree or building
How is data collected and recorded at a digital weather station?
-connected to data loggers and a computer to automatically record things
-no human interference needed
Name 4 instruments that may be found in a Stevenson screen:
-thermometer
-max-min thermometer
-hygrometer
-barometer
