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| The
army testing a weather balloon. |
Radiosonde
A small radio transmitter, carried up through the atmosphere by
a hydrogen filled weather balloon, which transmits measurements
of pressure, temperature and humidity at various levels. Wind velocities
can also be calculated by radar tracking of a target carried by
the balloon. Typically balloons will reach heights of 24 - 30km
before bursting.
Rain
Liquid precipitation made up from water drops of diameter greater
than 0.5mm. Rain is classified as slight (falling at a rate of <0.5mm
per hour), moderate (0.5 - 4mm per hour) or heavy (>4mm per hour)
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| A
rainbow over Ireleth |
Rainbow
A rainbow is produced due to a combination of refraction and reflection
of sunlight through water drops. The coloration of the rainbow depends
on the size of the water drops. For example with drops larger than
1mm in diameter, intense, predominately red bows are formed, whereas
with drops around 0.05mm the rainbow is largely white with just
faint traces of colour near the edges. Rainbows can be observed
by moonlight but as the human eye cannot distinguish colour with
faint lights, these lunar rainbows appear to be white.
Remote
Sensing
Meteorological measurements made, not at the point at which the
measurements are required, but remotely. Remote sensing can be "active"
e.g. when a radar or laser beam is transmitted and the reflected
or scattered beam is collected and analysed by a receiver or "passive"
e.g. when a receiver collects and analyses naturally emitted radiation
from a distant source. Rainfall radar is an example of active remote
sensing while infra red satellite pictures are an example of passive
remote sensing.
Ridge
A ridge of high pressure is an extension of an anticyclone or area
of high pressure. It is the converse of a "trough" of
low pressure.
Rime
A deposit of white, rough ice crystals which forms when supercooled
water droplets of fog come into contact with a solid object at a
temperature below 0C. The deposit accumulates on the windward side
of the object. It occurs most frequently on high ground where supercooled
fog is most common.
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