Humidity Flashcards
Condensation nuclei
Microscopic water particles combine to form larger water droplets. Vapour –> liquid.
Typical raindrop = 2mm diameter
Moisture droplet = 0.02mm
Cloud-condensation nuclei = 0.002mm
Sublimation
Changing straight from gas to solid.
Also, solid to gas.
Rapid absorption/release of heat.
Humidity
How much water vapour is in the atmosphere.
Saturation of air by water Vapor
When air contains maximum amount of water vapour.
Cold air can hold less water than warm air.
Temperature influences amount of energy available to keep vapour from combining to create liquid. Warmer air, more energy, more vapour.
Absolute humidity
Total amount of water vapour present in a given volume.
Saturation below 0 degrees
saturation value is less over Ice than liquid, so water vapour sublimates to Ice.
Relative humidity
Ratio of mass of water vapour to maximum mass of water.
RH=Mass of water vapour/maximum mass of water vapour.
Effect of temperature on relative humidity
RH increases when temperature decreases.
Diurnal variation if relative humidity
RH higher in morning when temperature is lower.
Dew point
Temperature which parcel of air saturates (100% RH).
When temp and dew point are close together, low cloud or fog form.
Provides indication of amount of water vapour in the atmosphere,
Relative humidity calculation
RH% = 100 - (5x(T-TD))
T=ambient temperature
TD=dew point
What does it mean when temperature and dew point are close?
Fog.
