Weather and Climate Weather and Climate Clouds Weather and Climate Dew and

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Weather and Climate Weather and Climate Clouds Weather and Climate Dew and Powered By Docstoc
					Weather and Climate

       Clouds




                      Weather and Climate
           Dew and Frost
• Where does dew and frost form? Why?




                                        Weather and Climate
        Frozen Dew vs. Frost
   Are frozen dew and frost the same thing?
• Frozen dew forms when the air temperature
  gets below freezing after dew forms.
• Frost occurs when the dew point
  temperature is at or below freezing.
  – Water vapor goes directly from vapor to solid.



                                               Weather and Climate
 When the dew is on the grass,
  rain will never come to pass.
When grass is dry at morning light,
 look for rain before the night!




                               Weather and Climate
     Good Conditions for Dew
           Formation
• Clear, calm nights  good for dew
• Cloudy, windy night  dew not likely
• Calm clear nights are usually associated
  with a high pressure fair weather system.
• Cloudy and windy weather is usually
  associated with an approaching storm
  system.

                                          Weather and Climate
         What is black frost?
• Sometimes the air temperature may go
  below freezing but no frost forms.
  – The air is very dry
  – The dew point temperature is never reached.
• This is also called simply a “freeze”.
• This type of event is very damaging to
  crops.

                                              Weather and Climate
  Clouds: Condensation Nuclei
• Sources:
  –   Dust
  –   Volcanoes
  –   Factory smoke
  –   Forest fires
  –   Salt from ocean spray
  –   Sulfate particles emitted by phytoplankton


                                                   Weather and Climate
 Hygroscopic vs. Hydrophobic
• Some particulates attract water and are called
  “hygroscopic”.
   – Such as: ocean salt, sulfuric acid, nitric acid
   – Water can condense in less than 100% relative
     humidity.
• Some particulates repel water and are called
  “hydrophobic”.
   – Such as: oils, gasoline, paraffin waxes, Teflon
   – Water vapor will resist condensing even when relative
     humidity is greater than 100%.
• At any given time there are usually enough
  condensation nuclei for clouds to form near 100%
  relative humidity.
                                                       Weather and Climate
Haze




       Weather and Climate
                  Fog
• Fog is not the same as haze, but can often
  develop from haze.
• Fog has a visibility less than 1km
  (0.62miles).
• There are different mechanisms for fog
  formation.



                                        Weather and Climate
Radiation Fog




                Weather and Climate
               Valley Fog
• Valley fog is a type of radiation fog.
• Cold, heavy air drains down mountains and
  collects in the valleys.
• Rivers running through valleys, helps make
  them very susceptible to fog.




                                         Weather and Climate
Advection Fog




                Weather and Climate
Upslope Fog




              Weather and Climate
        Evaporation (Mixing)Fog
• This fog is formed by the same process that allows
  you to “see” your breath on a cold winter day.
• This fog is formed by two unsaturated parcels of
  air mixing.




                                            Weather and Climate
Steam Fog




            Weather and Climate
                Frontal Fog
• Type of evaporation (mixing) fog.
• Warm rain falling through a layer of cold
  moist air can produce fog.
  – This is commonly observed before a warm
    front, or behind a cold front, hence the name
• Also called precipitation fog.



                                               Weather and Climate
               Foggy Weather




•    The three regions of the US with the most
     number of heavy fog days are:
    1.   The Pacific Coast States
    2.   The Appalachian highland region
    3.   New England
                                             Weather and Climate
Is fog good or bad?



                      Weather and Climate
Cloud Types
 1.            2.




  3.
              4.
            Howard’s System
• Wispy clouds were named “cirrus”, which means
  “curl of hair” in Latin.
• Puffy clouds were named “cumulus”, which
  means “heap” in Latin.
• Sheet like clouds were named “stratus” which
  means “layer” in Latin.
• Rain clouds were named “nimbus”, which means
  “violent rain” in Latin.
 By combining these basic types different clouds
  could be described.
                                              Weather and Climate
         Combining Names
• Cumulonimbus     Rain and “puffy”look
• Nimbostratus     Rain and “layer” look
• Stratocumulus    “Layer” and “puffy”
                      look




                                        Weather and Climate
                Cloud Types
• In 1887, Abercromby and Hildebrandsson
  expanded Howard’s classification.
• Clouds were divided into four groups:
  –   High clouds
  –   Middle clouds
  –   Low clouds
  –   Clouds with vertical development


                                         Weather and Climate
         High Clouds (Cirrus)
• In the middle and low latitudes, high clouds
  generally form above 20, 000ft.
• These clouds are mostly ice crystals and are
  very thin. Why?…….
  – Higher up it is cold! Cold air has less of a
    capacity for water vapor.
• These clouds appear white in color.


                                                   Weather and Climate
High Clouds




              Weather and Climate
Cirrocumulus




               Weather and Climate
Cirrostratus




               Weather and Climate
Cirrostratus




               Weather and Climate
Cirrostratus




               Weather and Climate
       Middle Clouds (Alto)
• Cloud base begins 6,500ft-23,000ft, in
  middle latitudes.
• Composed of water droplets, except when
  cold enough for ice crystals.




                                       Weather and Climate
Altocumulus




              Weather and Climate
              Altostratus

• Often cover the entire sky, extending over
  hundreds of square kilometers.
• Sometimes the sun can be seen through
  these blue-gray clouds, appearing as a
  “watery sun”.




                                         Weather and Climate
Weather and Climate
               Low clouds
• Base of clouds is below 2000m (6,500 ft.)
• Almost always composed entirely of water
  droplets.
  – In extremely cold weather may contain ice
    particles and snow.




                                                Weather and Climate
Nimbostratus




               Weather and Climate
Stratocumulus




                Weather and Climate
Stratus




          Weather and Climate
            Clouds with Vertical
                Development
            Cumulus




Cumulus
Congestus
                          Weather and Climate
Cumulus Humilis




           Cumulus Congestus



                        Weather and Climate
                       Cumulonimbus
• These are thunderstorm clouds.
• These clouds may extend from 600m
  into the tropopause.
• Often characterized by an anvil top.
• Produce lightning, hail, and thunder.
                                  Weather and Climate
Weather and Climate
Lenticular Clouds




                    Weather and Climate
Pileus




         Weather and Climate
          Mammatus Clouds
• For formation: Sinking air must be colder
  than surrounding air and have a high liquid
  water or ice content.
  – The sinking air warms, but not very quickly
    because of the latent heat taken from the air to
    evaporate the liquid, or melt the ice.
  – If the sinking air remains saturated and cooler
    than the surrounding air, the sinking occurs
    beyond the base of the cloud.

                                                 Weather and Climate
Mammatus Clouds




                  Weather and Climate
Nacreous Clouds




                  Weather and Climate
Noctilucent Clouds




                     Weather and Climate

				
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posted:3/4/2012
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