ATOC 4720: class 5ATOC 4720: class 5

1. The fair weather atmospheric 1. The fair weather atmospheric electric fieldelectric field

The atmospheric temperature The atmospheric temperature distributiondistribution

1. The fair weather electric 1. The fair weather electric fieldfield

10-50km

Most electrons: >60km

80km

Magnitude near the earth’s Magnitude near the earth’s surfacesurface

120V/m: global mean120V/m: global mean 130V/m over ocean130V/m over ocean 360V/m industrial 360V/m industrial

regionregion >100km, conductivity >100km, conductivity

of air increases with of air increases with height--the fair height--the fair weather electric field weather electric field decreases with height decreases with height

Electrosphere carries Electrosphere carries a net positive charge;a net positive charge;

The erath’s surface a The erath’s surface a net negative charge;net negative charge;

Average electric Average electric current: 2-4current: 2-4

Question:Question:

The electric field in the atmosphere is The electric field in the atmosphere is nearly constant with time although there is nearly constant with time although there is electric current that would be large enough electric current that would be large enough to discharge the capacitor. to discharge the capacitor. What does this What does this mean?mean?

Answer:Answer:

There must be an electric generator in the There must be an electric generator in the atmosphere/earth system.atmosphere/earth system.

Thunderstorms: widely accepted ideaThunderstorms: widely accepted idea

10-50km

Elecrical Budget for the earth:Elecrical Budget for the earth:

90 units gained from fair weather 90 units gained from fair weather conductivity (positive charges);conductivity (positive charges);

30 units from precipitation (positive 30 units from precipitation (positive charges);charges);

100 units lost by point charges;100 units lost by point charges; 20 units lost due to transfer of negative 20 units lost due to transfer of negative

charges by lightning. (C/km2/yr)charges by lightning. (C/km2/yr)

2. The temperatuer distribution 2. The temperatuer distribution

andits meansurementandits meansurement Early exploration: manned balloon flights--Early exploration: manned balloon flights--

provided first conclusive evidence that within provided first conclusive evidence that within 10km, temperature decreases with height at a 10km, temperature decreases with height at a rate of about 7C, which is called lapse rate rate of about 7C, which is called lapse rate (troposphere).(troposphere).

>10km, T constant or increases with Z: >10km, T constant or increases with Z: (stratosphere) (1902)(stratosphere) (1902)

1920’s: radiosonde: unmanned balloon; 1920’s: radiosonde: unmanned balloon; modern--up to 40km; (born aloft by rockets: 40-modern--up to 40km; (born aloft by rockets: 40-80km). 80km).

2. The temperature distribution and its 2. The temperature distribution and its measurementmeasurement

80% massAll water(homo or heter?)

Sharp dropIn water