Downloaded 13 times
More Related Content
Lecture11 oct16-bb
- 1.
- 2. Geostrophic Wind when theisobars are straight, parallel lines, and the only two forces acting on a parcel are the PGF and the CF, then the wind is called geostrophic wind L 475 mb • PGF and CF are equal in magnitude and opposite in direction • Geostrophic winds are always parallel to the isobars PGF CF Wind 500 mb H 500 mb Surface 2
- 3. Strength of GeostrophicWind geostrophic conditions are that PGF and CF are equal in magnitude and opposite in direction P G F C F 2 V g sin Vg PGF L 475 mb PGF CF 2 sin Wind 500 mb H strength of geostrophic wind is determined by PGF not by CF, why? 3
- 4. Vg PGF 2 sin The Coriolis force can only change a parcel's direction, it CAN NOT affect its speed. 4
- 5.
- 6. Gradient Wind counter linesare relatively straight Counter lines are curvature Geostrophic Wind 6
- 7. Gradient Wind Centripetal force ifyou attach a string to a ball and swing it in a circular manner, then the force required to keep the ball moving in a circular path is called centripetal force magnitude of the centripetal force is centripital force V 2 r V=speed of a parcel (object) r= distance from the center direction of the centripetal force is directed inward, towards the axis of 7 rotation V
- 8. recall geostrophic wind L 475mb PGF Wind CF 500 mb H 8
- 9. Gradient Wind Centripetalforce Gradient wind is produced by the balance between PGF, CF and centripetal force PGF PGF PGF PGF 9
- 10.
- 11. above 850 mblevel, the flow is either geostrophic wind or gradient wind(free troposphere) near the surface about 1-2 km (boundary layer), we must include the effect of friction and therefore, the flow is no longer geostrophic or gradient balance 11
- 12. Q: As aresult, which force becomes smaller, the PGF or the CF? the atmosphere above the boundary layer is called free troposphere friction has a significant impact on wind in boundary layer (1-2 km) 12
- 13. Four forces inthe atmosphere 1. Pressure gradient force 2. Coriolis force Phigh Plow distance 2 V sin( ) 3. Centripetal force V 2 r 4. Friction kV which force is not caused by wind? which two forces do not affect wind speed? Coriolis force and centripetal force 13 PGF
- 14. at the centerof a surface low, the air converges, and then must rise H L at the center of a surface high, the air diverges, and must come from aloft due to sinking motion 14
- 15. Why temperature isthe most important to understand weather?
- 16. What is temperature definition? Whyearth’s radiation is infrared while solar radiation is short-wave? Wien’s Law m ax 3000 T (K ) ( m)
- 17. The earth’s radiationenergy is determined by what? Stefan-Boltzmann Law E T 4
- 18. The capacity ofair for holding water vapor is determined by what?
- 19. Saturation vapor pressure(mb) Temperature determines the capacity of holding water vapor in the air 120 110 100 90 80 70 60 50 40 30 20 10 0 * H 2O P This curve indicates how much water vapor can be held in the air at a given temperature 17.27 T PH 2 O (T ) 0.6108 e T 273.3 * T=44 oC T=10 oC T=30 oC 0 10 20 30 40 Temperature (oC) 50
- 20. Thermal circulation is generatedby pressure gradient Pressure gradient is produced by different heating
- 21. Rule Cool surface air sinking high surface pressure Warm surface air rising low surface pressure Wind is blowing from high pressure to low pressure Where is clear sky? Cool High P Warm Low P
- 23. Scales of AtmosphericMotions Time and space scale of atmospheric motions Typical size Global scale 5000 km Synoptic scale 2000 km Mesoscale 20 km Microscale 2m Typical life span 23
- 24.
- 25. isobars 7 AM 820 mb 860mb 900 mb 65oF 65oF
- 26. Sea breeze isobars 820 mb 860mb Cold Warm 780 mb 900 mb 90oF 70oF
- 27. isobars 820 mb 860 mb 900mb 90oF 70oF Cold Warm 780 mb