Transcript Meteorological charts

Meteorological charts
Surface weather chart for 3 January 2007 (UK Met Office)
1110 km:
1° lat =
111 km
http://www.wetterzentrale.de/topkarten/tknfax.html
Salient features
• Surface pressure pattern dominated
by highs and lows, on a scale ~ 103
km. We call this the synoptic scale
Salient features
• Surface pressure pattern dominated
by highs and lows, on a scale ~ 103
km. We call this the synoptic scale
• Pressure excursions around ± 30 mb
– much smaller than the total
pressure of ~1000 mb.
Salient features
• Isobars give an indication of the wind
speed by the geostrophic relation:
wind tends to flow along isobars and
its strength is proportional to pressure
gradient
Wind is in knots – 1 knot = 0.5
ms-1. The arrow points along
the wind direction. This
symbol is called a wind fleck.
Time scale
00 h
3/1/07
Weather system takes ~ 1 day
to pass over the UK – so
synoptic timescale is around a
day (105 s)
00 h
4/1/07
Fronts
AVHRR IR image
2317 2/1/07
http://www.sat.dundee.ac.u
Warm airfronts
Cold and warm
Cold
Air
Motion of front
Warm
air
Cold front: narrow (~100 km), steep,
can get line convection particularly on
leading edge
www.rossway.net,
Cold Air
Warm front: broad (~300 km),
layer cloud due to gentle upglide.
Convection unusual.
Occluded front
Warm air
Cold,
unstable air
Cold, stable
air
Radiosondes
Vaisala
RS80
Vaisala
RS92
Launching a
radiosonde
European radiosonde stations (launch
00 and 12 UTC)
Data available from:
http://weather.uwyo.edu/upperair/sounding.html
700 mb,
300 mb,
~ 3 km
~ 9 km
Smoother patterns than at the surface; fronts not marked on these charts
700 and 300 mb charts show a similar pattern – synoptic scale features are generally
coherent throughout the troposphere. That is, vertical scale of synoptic-scale features ~
10 km
Winds closer to geostrophic – no surface friction
Very strong winds at 300 mb denote the jet stream. Jet stream is related to fronts, either
at the surface or in the upper troposphere.
Westerly winds increase with height: thermal wind equation