v. Clouds

HUMIDITY ANDDEW POINT

1DEW POINTThe dewpoint is the temperature of air which is needed for condensation or dew (at that particular temperature).

If you take a glass of ice water and it develops condensation on the glass surface, the air on the glass has condensed to its dewpoint and created dew.

Dewpoint actually measures how much water vapor is in the air. 2RELATIVE HUMIDITYRelative humidity is a measure of how much water vapor the air actually could "hold" at a certain temperature.

The relative humidity represents how close the air is to saturation.

Saturated air will have an RH of 100 %. You need the RH of 100% to have rain form in clouds. 3To measure relative humidity use a sling psychrometer (hygrometer)

How do we measure Humidity??????4Dry bulb thermometer and a wet bulb thermometer mounted together

Dry bulb tells actual temperatureWet bulb shows how much water can be evaporated temperature lowers as water is evaporated

5The difference in temperature on the 2 thermometers is an indication of the amount of water vapor in the air.6

Wet bulb.Dry BulbHow relative humidity (RH) is measured?Wet- and Dry Bulb Psychrometer

8Wet- and Dry Bulb Psychrometer Psychrometric Chart.

If the difference between wet and dry bulb is 6 F and the temperature is 72 F (dry bulb), then the RH is 54%.9Dry air: the water will evaporate quickly and cause a large drop in the wet-bulb temperature.

This makes the difference in readings on the 2 thermometers greater.

10Moist air: little water will evaporate from the wet-bulb and the temperature decrease will be small.

The difference between the wet bulb and dry bulb will be small.11When the Wet bulb temperature = the dry bulb temperature

100% HUMIDITY!!!

12The "wetter or damper" you feel,, the higher is the relative humidity.

If you feel the air is dry around you, the relative humidity is low.

13Glass of water demo

AssignmentBlk text pg 505 6-9V. Clouds & Precipitation

CLOUDS AND PRECIPITATIONS16A. Cloud Formation (condensation)1. All clouds require 3 things:a. water vaporb. condensation nuclei- something for water to bond withc. cooling- air must be cooled below dew point . Expansion, or when air rises. When air in the atmosphere sinks it compresses causing heating.

17Cloud familiesHigh altitudeMiddle altitudeLow altitudeVertical development

C. Cloud Types1. Cirrus- wispy, feathery high altitude clouds. a. Made of ice crystals19

202. Stratus- flat, spread out layers. Low to middle altitude. a. form through horizontal air movement 21

223. Cumulus- fluffy, rounded, medium altitude clouds. a. form through vertical air movementb. cumulus- piled23

244. Cumulonimbus- large rain/storm clouda. nimbo rain b. cumulo- column like

27

CumulunimbusCirrusstratuscumulus

Classify this cloud.G. Forms of Condensation1. Frost- when the temp of the air is below 0C, then the water vapor condenses as a solid.

2. Fog- cloud formation near Earths surface.a. Ground/radiation fog- during nighttime with sky clears, the ground loses heat rapidly by radiation.1.) breeze mixes air at ground level2.) air is cooled below the dew point and fog forms.

b. advection fog- when warm, moist air blows over a cool surface.

Topic Questions 511 blk textComplete the following questions.10, 11, 12a, 14a,b, 15a.Read pg 512-514 topics 16-17. then draw diagram 27.12 in your notes and describe in your own words how rain drops forms and the types of precipitation.