Hydrologic Cycle

1. Hydrologic Cycle

2. Humidity • Refers to the amount of water vapor in the air • Specific • Ratio of water vapor to air (dry air + water vapor) for a given parcel • Does not change with expansion or compression • Relative • Ratio of amount of water vapor for a given parcel to amount of water vapor if air was saturated • Absolute • Density of water in a given parcel of air • Subjected to volume changes • Warm air has greater capacity to hold moisture than cool air

3. Relative Humidity • A ratio of the amount of water vapor in the air, relative to how much water vapor that air can hold…… • WHAT IS THE PROBLEM WITH USING RELATIVE HUMIDITY TO SEE IF THE AIR IS HUMID? Actual water vapor content of the air Relative humidity = X 100 Maximum water vapor capacity of the air at that temperature

5. Specific Humidity

6. Air Saturation and Dew Point • = 100% relative humidity; that is the air is holding as much moisture as it can at its temperature = saturation and dew point • Dew Point is temperature to which air would have to be cooled to achieve saturation assuming there is no change in pressure or moisture content • DEW POINT IS A GOOD INDICATOR OF HOW MUCH MOISTURE IS IN THE AIR.

7. General Dewpoint Thresholds

9. Fun with the Heat Index Calculator • http://www.easysurf.cc/cnver16.htm

10. Fog • Fog is a cloud at ground level • Indicates saturated conditions at ground level • Fog types • Advection fog- warm moist air moves over a cold surface • Evaporation or steam fog- cold air moves over warm water • Radiation fog- air layer in contact with the ground cools to dew point…..creates shallow fog on calm clear nights

12. WHAT KIND IS THIS?

14. WHAT KIND????

18. Heavy Fog Days