1. METO 637 Lesson 2

2. Forces that Move the Air Gravitational force Is directed downward, normal to the ground Approximately equal to the mass of the air times the gravitational acceleration Pressure gradient force

3. Fig. 6.4

4. PRESSURE- GRADIENT FORCE.IS A FUNCTION OF THE PRESSURE DIFFERENCE AND AIR DENSITY..F PC = ΔP / D.σ WHERE F PC = PRESSURE GRADIENT FORCE PER UNIT MASS σ = DENSITY OF AIR ΔP = PRESSURE DIFFERENCE BETWEEN TWO POINTS D = DISTANCE BETWEEN THE TWO POINTS.NEWTON’S LAW STATES FORCE=MASS TIMES ACCELERATION.F PC IS A FORCE PER UNIT MASS, I.E. IS EQUIVALENT TO ACCELERATION

5. CORIOLIS EFFECT WEATHER MAP SHOWS THAT WINDS GO AROUND A LOW PRESSURE AREA, NOT ACROSS THE ISOBARS. THIS DEVIATION IS A RESULT OF THE EARTH'S ROTATION AND HAS BEEN NAMED THE CORIOLIS EFFECT (CORIOLIS FORCE) THIS FORCE ALWAYS ACTS AT RIGHT ANGLES TO THE DIRECTION OF MOTION.

6. Coriolis Effect

7. The Mechanism for Geostrophic Flow

8. GEOSTROPHIC FLOW.EVENTUALLY A BALANCE IS REACHED BETWEEN THE CORIOLIS FORCE AND THE PRESSURE GRADIENT FORCE.IF THERE IS NO FRICTION THEN THIS OCCURS WHEN THE PARCEL OF AIR IS PARALLEL TO THE ISOBARS..AT THIS POINT THERE IS NO NET FORCE ON THE AIR PARCEL - NO ACCELERATION - IT NOW MOVES WITH CONSTANT VELOCITY..UNDER THESE IDEALIZED CONDITIONS THE AIRFLOW IS SAID TO BE IN GEOSTROPHIC BALANCE..WIND GENERATED IS CALLED THE GEOSTROPHIC WIND.NORMALLY ONLY APPLIES TO WINDS ALOFT..SURFACE WINDS ARE SUBJECT TO FRICTION.

9. Fig. 6.15 Gradient Winds

10. Fig. 6.16 Gradient Winds – including Centrifugal Force

11. GRADIENT WINDS ·WINDS AROUND CENTERS OF HIGH OR LOW PRESSURE FOLLOW CURVED PATHS IN ORDER TO STAY PARALLEL WITH THE ISOBARS. ·THESE WINDS ARE CALLED GRADIENT WINDS. ·LOW PRESSURE CENTERS ARE CALLED CYCLONES - ROTATION IS COUNTER- CLOCKWISE - SAME AS THE EARTH ·CENTERS OF HIGH PRESSURE ARE CALLED ANTI-CYCLONES. ·IN SOUTHERN HEMISPHERE THE DIRECTIONS OF FLOW ARE REVERSED

12. Fig. 6.18 Effect of Friction at Surface on Geostrophic Balance

13. Fig. 6.24 Gradient winds at the surface

14. SURFACE WINDS.FRICTION AFFECTS WINDS ONLY CLOSE TO THE EARTH'S SURFACE. NOW WE MUST BALANCE THREE FORCES - CORIOLIS, PRESSURE GRADIENT AND FRICTION..NET EFFECT IS TO INDUCE A NET INFLOW AROUND A CYCLONE, AN EFFECT KNOWN AS CONVERGENCE. AROUND AN ANTICYCLONE WE GET A NET OUTFLOW, DIVERGENCE

15. Electromagnetic spectrum

16. SOLAR ENERGY Solar constant – energy from the sun that falls on unit surface normal to the line from the sun, per unit time, at the outside of the atmosphere at the mean solar distance S = 1.368 Kw per meter 2 S is integrated over all wavelengths S varies with the sunspot cycle

17. UV-VISIBLE SOLAR SPECTRUM

18. Absorption of Solar Radiation in the Earth’s Atmosphere