nats 101 lecture 15 surface and upper-air maps. supplemental references for today’s lecture...
TRANSCRIPT
![Page 1: NATS 101 Lecture 15 Surface and Upper-Air Maps. Supplemental References for Today’s Lecture Gedzelman, S. D., 1980: The Science and Wonders of the Atmosphere](https://reader035.vdocuments.site/reader035/viewer/2022062515/56649cee5503460f949bbe61/html5/thumbnails/1.jpg)
NATS 101
Lecture 15Surface and Upper-Air Maps
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Supplemental References for Today’s Lecture
Gedzelman, S. D., 1980: The Science and Wonders of the Atmosphere. 535 pp. John-Wiley & Sons. (ISBN 0-471-02972-6)
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Summary
• Because horizontal pressure differences are the force that drives the wind
Station pressures are adjusted to one standard level…Mean Sea Level…to mitigate the impact of different elevations on pressure
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Ahrens, Fig. 6.7
PGF
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Correction for PhoenixElevation of PHX Airport is ~340 m
Station pressure at PHX was ~977 mb
So, SLP for PHX would be
SLP = 977 mb + (1 mb / 10 m) 340 m
SLP = 977 mb + 34 mb = 1011 mb
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Surface Maps
• Pressure reduced to Mean Sea Level is plotted and analyzed for surface maps.Estimated from station pressures
• Actual surface observations for other weather elements (e.g. temperatures, dew points, winds, etc.) are plotted on surface maps.
NCEP/HPC Daily Weather Map
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Isobaric Maps
• Weather maps at upper levels are analyzed on isobaric (constant pressure) surfaces.(Isobaric surfaces are used for mathematical reasons
that are too complex to explain in this course!)
• Isobaric maps provide the same information as constant height maps, such as:
Low heights on isobaric surfaces correspond to low pressures on constant height surfaces!
Cold temps on isobaric surfaces correspond to cold temperatures on constant height surfaces!
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Isobaric Maps
Ahrens, Fig. 2, p141
504 mb504 mb
496 mb496 mb
PGF
Downhill(Constant height)
Some generalities:
1) High/Low heights on an isobar surface correspond to High/Low pressures on a constant height surface
2) Warm/Cold temps on an isobaric surface correspond to Warm/Cold temps on a constant height surface
3) The PGF on an isobaric surface corresponds to the downhill direction
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Contour MapsHow we display
atmospheric fields
Portray undulations of 3D surface on 2D map
A familiar example is a USGS Topographic Map
It’s a useful way to display atmospheric quantities such as temperatures, dew points, pressures, wind speeds, etc.
Gedlezman, p15
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Contour Maps “To successfully isopleth the 50-degree isotherm, imagine that you're a competitor in a roller-blading contest and that you're wearing number "50". You can win the contest only if you roller-blade through gates marked by a flag numbered slightly less than than 50 and a flag numbered slightly greater than 50.”
https://www.e-education.psu.edu/gened/meteo101/Examples/Section2p02.html
Click “interactive exercise”
https://www.e-education.psu.edu/gened/meteo101/Examples/Section2p03.html
https://www.e-education.psu.edu/gened/meteo101/Examples/Section2p04.html
Click “interactive isotherm map”
From
Online Picture
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570 dam contour570 dam contour
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576 dam contour576 dam contour
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570 and 576 dam contours570 and 576 dam contours
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All contours at All contours at 6 dam spacing6 dam spacing
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All contours at All contours at 6 dam spacing6 dam spacing
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-20 C and –15 C -20 C and –15 C Temp contoursTemp contours
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-20 C, –15 C, -10 C -20 C, –15 C, -10 C Temp contoursTemp contours
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All contours at All contours at 55oo C spacing C spacing
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Height contours Height contours Temps shadedTemps shaded
Region of Region of HighHigh Heights Heights RIDGERIDGE
and and WarmthWarmth
Region of Region of LowLow Heights Heights TROUGHTROUGH
and and ColdCold
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PGFWind
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Key Concepts for Today
• Station Pressure and Surface Analyses
Reduced to Mean Sea Level Pressure (SLP) PGF Corresponds to Pressure Differences
• Upper-Air Maps
On Isobaric (Constant Pressure) Surfaces PGF Corresponds to Height Sloping Downhill
• Contour Analysis
Surface Maps-Analyze Isobars of SLP Upper Air Maps-Analyze Height Contours
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Key Concepts for Today
• Wind Direction and PGF
Winds more than 1 to 2 km above the ground are perpendicular to PGF!
Analogous a marble rolling not downhill, but at a constant elevation with lower altitudes to the left of the marble’s direction
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Assignment
Topic – Newton’s Laws
Reading - Ahrens pg 150-157
Problems - 6.12, 6.13, 6.17, 6.19, 6.22