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Atmospheric Moisture. Moisture, Clouds, and Precipitation. Humidity Global Precipitation Lifting Mechanisms Precipitation Processes Big Question: What Causes Air to Precipitate?. Global Precipitation. After Saturation Occurs the Air Must Release Extra Water as Fluid.
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Moisture, Clouds, and Precipitation • Humidity • Global Precipitation • Lifting Mechanisms • Precipitation Processes Big Question: What Causes Air to Precipitate?
After Saturation Occurs the AirMust Release Extra Water as Fluid Water forms on the outside of a cold glass as the cold Air surrounding the glass chills the air to the Dew Point Temperature The resulting water is not from the glass, the water is from condensation of moisture in the air around the glass
Forms of Precipitation • Precipitation (pre-sip-uh-tay-shun) is any form of water that falls to the Earth's surface.
Types of Precipitation • The type of precipitation that falls to the ground depends upon the formation process and the temperatures of the environment between the cloud and the surface
Can you name the different types of precipitation? • Rain • Snow • Hail • Sleet • Freezing Rain
Rain • Rain develops when growing cloud droplets become too heavy to remain in the cloud and as a result, fall toward the surface as rain
Rain can also begin as ice crystals that collect each other to form large snowflakes As the falling snow passes through the freezing level into warmer air, the flakes melt
Snow • Snow is formed when ice crystals form from water vapor that is in the clouds directly above your heads! • This process is called sublimation
Snowflakes and Temperature Snow crystal images from an electron microscope
Hail • Hail is formed when updrafts carry raindrops upwards into extremely cold areas of the atmosphere
Hail • There the raindrops merge and freeze. When the frozen clumps get to heavy they fall to earth
Sleet • Sleet is frozen raindrops. Sleet begins as rain or snow and falls through a deep layer of cold air that contains temperatures below freezing that exist near the surface.
Sleet • Rain that falls through this extremely cold layer has time to freeze into small pieces of ice
Freezing Rain • Freezing rain is falling rain that cools below 0°C, but does not turn to ice in the air • The water is “supercooled”
Measuring Rain w/ Standard Gauge Standard rain gauge uses a funnel to collect rain and then stores it in a narrower tube, so that the gauge detection is amplified 10-fold. The 50 cm long tube, when filled, represents only 5 cm of total rainfall. Figure 8.27
Measuring Rain w/ Recording Gauge Figure 8.28 Tipping bucket and weighing rain gauges record precipitation rate at shorter time intervals, providing rain intensity data. Snow intensity can be measured with depth recorders, or accumulated totals with measuring sticks.
Snow depth • Snow can be measured as an actual depth by sticking a measuring stick into it • This is not reliable as the depth will change the next place you measure • Depth will depend on the type of snowflakes that fall (how fluffy they are)
Equivalent rain water depth • Usual conversion is 10 to 1 • 10cm of snow = 1cm of rain • (or 10” snow = 1” rain) • But very variable and depends on type of snow and how long it’s been settling
Ready? • Nuclei for the formation of rain drops can be small particles of: A) salt, B) smoke, C) dust, D) all the above • Which of these cloud types is not based on the clouds shape: A) stratus, B) nimbus, C) cumulus, D) cirrus
3. Mid elevation clouds between 2000 and 6000m: A) nimbus, B) alto, C) cirro, D) strato 4. This form of precipitation is supercooled: A) rain, B) snow, C) sleet, D) freezing rain
5.This form of precipitation stays frozen all the way to the ground: A) rain, B) snow, C) sleet, D) freezing rain Let’s see how you did!
The Answers! 1. D 2. B 3. B 4. D 5. B
Summary • Precipitation (Rain, Snow, Sleet) • When air is substantially cooled below the dew point, large droplets or ice crystals form and may fall if large enough.
