Observations Flashcards
(33 cards)
When are observations taken worldwide?
0000, 0600, 1200, 1800 UTC
How many weather stations are there in the UK?
200+
how far apart are the stations
40km
What does AWS stand for
Automated Weather Stations
What are the main measurements by a weather station?
temperature, humidity, wind, rainfall, pressure, cloud and ‘present weather
What are the conditions for a weather station
a flat site well away from buildings trees or steep ground, this provides data that is representative of a wider area
What is a stevenson screen
where themometers and humidity sensors are kept
why are stevenson screens white
to reflect the sun
why are the sides of the stevenson screen louvred
to allow for ventilation
what side is the door on a stevenson screen
north side
At what hight is temp and humidity measured at
1.25 m above the ground
What is used to measure rainfall
a tipping bucket device is continually used to monitor the amount of precipitation
at what hight are wind measurements take
10m above the ground in an area with no large obstacles within 300m to affect wind
what is commonly used to take wind measurements
cup or sonic anemometers most commonly used
what method is used to measure the wind
the mean wind is take 10 mins before reporting time and the gust is the maximum of 3 second average
what is pressure measured by
electronic sensor
what method is pressure measured by
3 separate measurements with automated checks for discrepancies than the reported pressure is converted to sea-level
why is it important to make cloud observations
for aviation purposes
what things are measured about clouds
cloud amount, type and cloud base
how are cloud distributions best measured
from satellite images
what are the drawbacks of using satellite images to measure clouds
cloud base cant be measured
cloud layers below top are not visible
satellite instruments struggle to distinguish shallow and low cloud from fog from the land
how many sub categories of clouds is there
10
what does a cloud base recorder measure?
cloud base and amound
waht does a LIDAR system do
sends pulses of laser light upwards and records backscatter from clouds.
