Presentation is loading. Please wait.

Presentation is loading. Please wait.

Cloud Development and Precipitation Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida.

Similar presentations


Presentation on theme: "Cloud Development and Precipitation Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida."— Presentation transcript:

1 Cloud Development and Precipitation Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida

2 Adiabatic Cooling and Warming Rising air expands & cools, while sinking air is compressed and warms Rising air expands & cools, while sinking air is compressed and warms Adiabatic process is one in which there is no heat exchange with the surrounding air Adiabatic process is one in which there is no heat exchange with the surrounding air

3 Stability: Key to Cloud Development The stability of a layer in the atmosphere is determined by comparing the temperature of a rising parcel of air (which cools at the adiabatic lapse rate) to that of its surroundings (which cool at the environmental lapse rate) The stability of a layer in the atmosphere is determined by comparing the temperature of a rising parcel of air (which cools at the adiabatic lapse rate) to that of its surroundings (which cool at the environmental lapse rate) –Dry adiabatic rate of cooling is 10°C per 1 km –Moist adiabatic rate is 6°C per 1,000 meters –Environmental rate averages 6.5°C per 1 km

4 Stability: Key to Cloud Development (question) If a parcel of unsaturated air with a temperature of 30° C rises from the surface to an altitude of 1000 m, the unsaturated parcel temperature at this altitude would be about If a parcel of unsaturated air with a temperature of 30° C rises from the surface to an altitude of 1000 m, the unsaturated parcel temperature at this altitude would be about a. 10° C warmer than at the surface. b. 10° C colder than at the surface. c. 6° C colder than at the surface. d. impossible to tell from the data given

5 Stability: Key to Cloud Development (question) If a parcel of unsaturated air with a temperature of 30° C rises from the surface to an altitude of 1000 m, the unsaturated parcel temperature at this altitude would be about If a parcel of unsaturated air with a temperature of 30° C rises from the surface to an altitude of 1000 m, the unsaturated parcel temperature at this altitude would be about a. 10° C warmer than at the surface. b. 10° C colder than at the surface. c. 6° C colder than at the surface. d. impossible to tell from the data given

6 Stable Air An absolutely stable atmosphere exists when a rising air parcel is colder and heavier (more dense) than the surrounding air An absolutely stable atmosphere exists when a rising air parcel is colder and heavier (more dense) than the surrounding air If released, the air parcel returns to its original position If released, the air parcel returns to its original position

7 Factors Affecting Stability A stable layer results when there is a relatively small difference in temperature between the surface air and the air aloft A stable layer results when there is a relatively small difference in temperature between the surface air and the air aloft If air aloft warms or surface air cools, the atmosphere stabilizes If air aloft warms or surface air cools, the atmosphere stabilizes Some examples of processes leading to surface cooling are Some examples of processes leading to surface cooling are –Nighttime radiational cooling –Influx of cold air –Air cooled by a colder surface

8 Stable Air (question) If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be a. stable. b. unstable. c. isothermal. d. neutral. e. adiabatic.

9 Stable Air (question) If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be a. stable. b. unstable. c. isothermal. d. neutral. e. adiabatic.

10 Unstable Air An absolutely unstable atmosphere exists when a rising parcel of air is warmer and lighter (less dense) than the air surrounding it An absolutely unstable atmosphere exists when a rising parcel of air is warmer and lighter (less dense) than the air surrounding it If released, the air parcel would continue to rise If released, the air parcel would continue to rise

11 Factors Affecting Instability An unstable layer results when the environmental lapse rate steepens or the temperature of the air drops quickly with height An unstable layer results when the environmental lapse rate steepens or the temperature of the air drops quickly with height If air aloft cools or surface air warms it becomes unstable If air aloft cools or surface air warms it becomes unstable Some examples of processes leading to surface warming are Some examples of processes leading to surface warming are –Daytime solar heating –Influx of warm air –Air warmed by a hotter surface

12 Unstable Air (question) Which of the following environmental lapse rates would represent the most unstable conditions in a layer of unsaturated air? Which of the following environmental lapse rates would represent the most unstable conditions in a layer of unsaturated air? a. 1° C per 1000 m b. 3° C per 1000 m c. 6° C per 1000 m d. 9° C per 1000 m e. 11° C per 1000 m

13 Unstable Air (question) Which of the following environmental lapse rates would represent the most unstable conditions in a layer of unsaturated air? Which of the following environmental lapse rates would represent the most unstable conditions in a layer of unsaturated air? a. 1° C per 1000 m b. 3° C per 1000 m c. 6° C per 1000 m d. 9° C per 1000 m e. 11° C per 1000 m

14 Ways Clouds Form

15 Way Clouds Form (question) An example of orographic clouds would be An example of orographic clouds would be a. clouds forming over a warm ocean current. b. clouds forming on the windward slope of a mountain. c. clouds forming behind a jet airplane. d. clouds formed by surface heating.

16 Way Clouds Form (question) An example of orographic clouds would be An example of orographic clouds would be a. clouds forming over a warm ocean current. b. clouds forming on the windward slope of a mountain. c. clouds forming behind a jet airplane. d. clouds formed by surface heating.

17 Rain Shadow Air dries on the leeward side of mountains because of water vapor condensing and remaining as cloud droplets and precipitation on the windward side Air dries on the leeward side of mountains because of water vapor condensing and remaining as cloud droplets and precipitation on the windward side Rain shadow is the region on the lee side of the mountain with low precipitation and dry air Rain shadow is the region on the lee side of the mountain with low precipitation and dry air

18 Producing Rain: Collision and Coalescence Cloud droplets forming on condensation nuclei are extremely small with a diameter of 0.02 mm so they stay suspended by slight upwards air currents Cloud droplets forming on condensation nuclei are extremely small with a diameter of 0.02 mm so they stay suspended by slight upwards air currents Some larger droplets may form through random collision or by forming on larger condensation nuclei Some larger droplets may form through random collision or by forming on larger condensation nuclei

19 Producing Rain: Collision and Coalescence (continued) Larger drops fall faster than smaller drops, overtaking, colliding and coalescing with smaller droplets, eventually growing too heavy and falling to the ground due to gravity Larger drops fall faster than smaller drops, overtaking, colliding and coalescing with smaller droplets, eventually growing too heavy and falling to the ground due to gravity

20 Producing Rain: Collision and Coalescence (continued) Warm clouds with strong updrafts (like Cumulus Congestus) can sustain the weight of more larger drops, leading to bigger raindrops and heavier rain Warm clouds with strong updrafts (like Cumulus Congestus) can sustain the weight of more larger drops, leading to bigger raindrops and heavier rain

21 Producing Rain: Collision and Coalescence (question) The merging of liquid cloud droplets by collision is called The merging of liquid cloud droplets by collision is called a. coalescence. b. riming. c. accretion. d. deposition. e. condensation.

22 Producing Rain: Collision and Coalescence (question) The merging of liquid cloud droplets by collision is called The merging of liquid cloud droplets by collision is called a. coalescence. b. riming. c. accretion. d. deposition. e. condensation.

23 Ice-Crystal Process Most common type of rain formation at our latitudes (mid to high latitudes) Most common type of rain formation at our latitudes (mid to high latitudes) Small supercooled water droplets can exist at below freezing temperatures Small supercooled water droplets can exist at below freezing temperatures Ice-Crystals are also present, but in smaller quantities (because ice nuclei are scarce) Ice-Crystals are also present, but in smaller quantities (because ice nuclei are scarce) Bergeron process: Ice-Crystals grow at the expense of the surrounding water droplets through accretion, with the liquid water freezing on contact with the ice Bergeron process: Ice-Crystals grow at the expense of the surrounding water droplets through accretion, with the liquid water freezing on contact with the ice

24 Ice-Crystal Process (question) Most rain at middle latitudes is produced by the ice crystal process. This is because Most rain at middle latitudes is produced by the ice crystal process. This is because a. ice crystal nuclei are more plentiful than condensation nuclei. b. most clouds form in cold regions of the atmosphere. c. ice crystals evaporate more slowly than water droplets. d. most rain occurs during the winter.

25 Ice-Crystal Process (question) Most rain at middle latitudes is produced by the ice crystal process. This is because Most rain at middle latitudes is produced by the ice crystal process. This is because a. ice crystal nuclei are more plentiful than condensation nuclei. b. most clouds form in cold regions of the atmosphere. c. ice crystals evaporate more slowly than water droplets. d. most rain occurs during the winter.

26 Snow to Rain Ice-Crystals grow, fall, collide, and stick to one another forming a snowflake Ice-Crystals grow, fall, collide, and stick to one another forming a snowflake If snowflake melts before hitting the ground, it falls as a raindrop If snowflake melts before hitting the ground, it falls as a raindrop Most rain begins as snow Most rain begins as snow

27 Snow to Rain (question) Which of the following statements is not correct? Which of the following statements is not correct? a. Generally, the smaller the pure water droplet, the lower the temperature at which it will freeze b. Ice nuclei are more plentiful in the atmosphere than condensation nuclei c. Much of the rain falling in middle northern latitudes begins as snow d. Ice crystals may grow in a cold cloud even though supercooled droplets do not.

28 Snow to Rain (question) Which of the following statements is not correct? Which of the following statements is not correct? a. Generally, the smaller the pure water droplet, the lower the temperature at which it will freeze b. Ice nuclei are more plentiful in the atmosphere than condensation nuclei c. Much of the rain falling in middle northern latitudes begins as snow d. Ice crystals may grow in a cold cloud even though supercooled droplets do not.

29 Sleet and Freezing Rain Go to Visualization

30 Sleet & Freezing Rain (continued) A raindrop which freezes before reaching the ground is called A raindrop which freezes before reaching the ground is called a. snow. b. graupel. c. sleet. d. glaze.

31 Sleet & Freezing Rain (continued) A raindrop which freezes before reaching the ground is called A raindrop which freezes before reaching the ground is called a. snow. b. graupel. c. sleet. d. glaze.

32 Hail Produced by accretion Produced by accretion Up to 7” in diameter Up to 7” in diameter Causes hundreds of millions of dollars in damage annually Causes hundreds of millions of dollars in damage annually For a hailstone to grow to golf ball size it must remain in the cloud for 5 to 10 minutes For a hailstone to grow to golf ball size it must remain in the cloud for 5 to 10 minutes The hailstones may cycle within a Cumulonimbus, or be too heavy and drop The hailstones may cycle within a Cumulonimbus, or be too heavy and drop Go to Visualization

33 Measuring and Detecting Precipitation A rain gauge is used to collect and measure precipitation starting at 0.01” (less is called a “trace” of rain) A rain gauge is used to collect and measure precipitation starting at 0.01” (less is called a “trace” of rain) 10” of snow will melt to 1” of water (total precipitation) 10” of snow will melt to 1” of water (total precipitation) Radar (radio detection and ranging) shows where precipitation is and its intensity Radar (radio detection and ranging) shows where precipitation is and its intensity Doppler Radar allows us to observe rotating winds inside T-Storms to detect tornadoes Doppler Radar allows us to observe rotating winds inside T-Storms to detect tornadoes


Download ppt "Cloud Development and Precipitation Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida."

Similar presentations


Ads by Google