Chapter 7 Water and Atmospheric Moisture

Water on the earth: Land and Water Hemispheres 2/3 earth’s surface areas are water body Most land is over northern Hemisphere Figure 7.2

Ocean and Freshwater Distribution Figure 7.3

Unique Properties of Water Heat properties  Phase change Latent heat: heat related to water phase change Heat properties of water in nature  

Three States of Water Figure 7.5

Phase Changes Figure 7.7

Uniqueness of Ice Forms Figure 7.6

Humidity Saturation: air is holding the maximum amount vapor at the given air temperature. Expressions of humidity   Vapor pressure Specific humidity Relative humidity Dew point Instruments

Water Vapor in the Atmosphere Figure 7.10

Water Vapor in the Atmosphere Figure 7.10

Vapor pressure: pressure created by water vapor alone Saturation Vapor Pressure: maximum vapor pressure at a given air temperature. It increases with air temperature, more rapidly at higher air temperatures Figure 7.12

Specific humidity: the amount of water (g) vapor in a kg of dry air Maximum Specific Humidity: the saturation specific humidity at a given air temperature Figure 7.13

Relative Humidity: (actual vapor)/(saturation vapor); how close the atmosphere to the saturation Figure 7.8

Humidity Patterns Air temperature increases, the relative humidity decreases if there is no change in vapor amount in the air Figure 7.11

Humidity Instruments: hair hygrometer; dry-and-wet bulb thermometer Figure 7.14

Dew point temperature The air temperature when air reaches saturation (when dew starts to form)

Clouds and Fog Cloud Formation Processes Cloud Types and Identification   Fog  

Cloud Formation Processes Moisture droplets Cloud-condensation nuclei

Moisture Droplets Figure 7.20

Raindrop and Snowflake Formation Ice crystal process: ice crystals grow and water droplets evaporate Collision and coalescence: large droplets merges with smaller ones Figure 7.21

Cloud Types and Identification High clouds: cirrus, cirrostratus, cirrocumulus Middle clouds: altostratus, altocumulus Low clouds: stratus, stratocumulus, nimbostratus Clouds with vertical development: Cumulus cumulonimbus Figure 7.22

Cirrus Figure 7.22

Cirrostratus Figure 7.22

Altocumulus Figure 7.22

Altostratus Figure 7.22

Nimbostratus Figure 7.22

Stratus Figure 7.22

Cumulus Figure 7.22

Cumulonimbus Figure 7.22

Cumulonimbus Development Thunderstorm cloud: with updraft and downdraft in different parts of the cloud Figure 7.23

Fog: clouds with based on the ground Advection fog Evaporation fog Upslope fog Valley fog Radiation fog

Advection Fog: warm and moist air moves over a cooler surface Figure 7.24

Evaporation Fog: warm water evaporates into colder air above Figure 7.25

Radiation Fog: radiation cooling of the land surface chills the near surface air. Condition: clear sky, calm (light wind). Most common in fall and winter Figure 7.27