Atmospheric Moisture. Relative humidity Clouds Rain/Snow. Relates to atmosphere, hydrosphere, biosphere, exosphere, geosphere

Transcription

1 Atmospheric Moisture Relative humidity Clouds Rain/Snow Relates to atmosphere, hydrosphere, biosphere, exosphere, geosphere

2 Atmospheric moisture Water in the atmosphere Requires - vapor pressure- the amount of pressure contributed by any volatile substance > e.g., water - air capable of "holding" vapor > dependent on temperature Evaporation- - more water is becoming vapor than is condensing (becoming liquid) Condensation - opposite effect

3 It is possible to get rainfall at the Earth s surface without the relative humidity being 100%? A.True B. False

4 Relative humidity (RH) Water in atmosphere is dependent on temp. Saturation Vapor Pressure= - the maximum amount of water vapor that air can "hold" - temperature dependent - warm air "holds" more than cold air RH = Partial Vapor Pressure Determined from equation Saturation Vapor Pressure* measured indirectly as a function of temperature by a measuring device Determined from current air Temp

5

6 Clouds As RH goes to 100% water vapor condenses - i.e., it changes from vapor to liquid or solid forms clouds, rain, snow/ice it can be raining and not 100% RH! Condensation Factors must get air mass to reach saturation (approx) - accomplished by lifting & cooling, or increasing amount of water being vaporized usually have to have something for the water to condense onto...such as: - aerosols -dust particles and large molecules

7 Cloud formation Occurs most often due to lifting of an air mass Cooling due to adiabatic process - ADIABATIC - no energy lost or gained by exchanging with air that has different characteristics - dry lapse rate (not at saturation) > 10 C per 1000 meters (-5.5 F / 1000 ft) - wet lapse rate (at saturation) > heat gained as water condenses > air won't cool as fast > 6 C per 1000 meters (-3.3 F / 1000 ft)

8 In Earth s atmosphere, clouds form as relative humidity reaches 100%? A. True B. False

9 Means of lifting Heating (aka convectional lifting) - warmed air rises (if it has water vapor, it will create clouds) Orographic Lifting (mountains) - air encounters a barrier and goes over the top of it Frontal Lifting (air masses with different densities - cool air is more dense than warm air > slides underneath warm air, lifting it

10 convection

11 Convectional lifting

12 orographic

13 Orographic lifting creating lenticular clouds

14

15 Orographic lifting creating lenticular clouds

16 Frontal lifting Warm Front Cold Front

17 Cloud terminology is descriptive 10 Genera are based on cloud shape and Cirrus = feathered or wispy Stratus= layered Cumulus=puffy or heaped Elevation- prefix or suffix only low, middle, high, and vertically developed - Cirro = high - Alto = middle and Precipitation - prefix or suffix only. nimbo (-us) = rain A dozen species of clouds based on unique characteristics Sometimes linked to temperature, shape, moisture warm vs. cold clouds- liquid water vs ice crystals weird shapes, like twisted, lens shaped, anvil shaped

18 The 10 genera (the plural form of genus) for clouds Cirrus- thin, fibrous, hair-like high altitude ice crystal clouds Cirrocumulus- patchwork, grainy or rippled high altitude puffy clouds Cirrostratus- white, semi-transparent veil of high ice crystal based clouds Altocumulus- middle altitude puffy or rippled ice crystal clouds Altostratus- middle altitude layered clouds Nimbostratus- rain producing layered clouds, low level Stratocumulus- layered clouds with vertical component, difficult to see from ground Stratus- layered clouds at low altitude Cumulus- puffy clouds at low altitude Cumulonimbus- puffy rain producing clouds with strong vertical component, extending through multiple altitudes

19

20 Cirrus Clouds - High Clouds "Feathers" or "Wisps" or small "Puffs" almost always High clouds Usually Ice crystals - a "mackerel" sky with small, puffed, cirrus clouds known as cirrocumulus - and almost layered cirrostratus clouds

21 Happy little cirrus clouds. Bob Ross

22 Perspective is everything from below, the low clouds look like stratus from above they look like cumulus in reality they are some combination of both! - three layers are visible here - cirrus > v. high - altocirrus > middle - stratocumulus > lower

23 Stratus clouds layered clouds occur at all elevations can be thick and rain/snow producing - Stratus clouds look like a gray sky - these are Nimbostratus clouds which produce rain

24

25 Cumulus puffy clouds with some vertical development - these cumulus cloud examples developed due to heating of land which caused the air to heat and rise into cooler air

26 Cumulonimbus Clouds continued vertical development will eventually lead to Cumulonimbus clouds - these produce heavy local rains, strong winds, and thunderstorms Characterized by a tall, often flat-topped, puffy cloud form

27 Unique cloud shapes Orographic lifting creating a lenticular cloud Air turbulence creating a lenticular cloud

28 Mammatus clouds

29 Wall Cloud with lightning- note rotational motion around a vertical axis

30 Shelf Cloud along a beach in Sydney, Australia Not the rotational motion or spilling over along a horizontal axis

31 Altocumulus (?) Castelanus- aka jellyfish clouds Altocumulus Castelanus- aka jellyfish clouds

32 Noctilucent cloud Contrails- jet engine produced cirrus clouds Halo cloud Iridescent cloud

33 Virga- rain that evaporates before reaching the ground Sun Dogs Rainbow- rain acts as a prism, splitting white sunlight into its spectral colors

34 Precipitation includes rain,drizzle, freezing rain, snow, hail, ice pellets etc. occurs when the weight of the water which has condensed in the air overcomes the influences of the winds keeping it aloft - falls under the influence of Earth's Gravity - velocity doesn't continue to increase > air resistance slows it down as it falls - Max Velocity called Terminal Velocity > varies with size of the water droplet most precip forms by a processes known as Bergeron process

35 Precipitation (2:2) Rain = drops > 0.5 mm Drizzle = droplets ~ 0.2 & 0.5 mm Freezing rain = liquid water (sometimes supercooled) which falls onto freezing (or near freezing) surfaces Snow = ice crystal in dendrites, plates, columns, or needles form Pellets = aka, sleet; water droplets freeze freeze Hail = big ice pellets that have been "recycled" through a cloud several times

36 Dew/Frost saturated air near the ground gets cooled to the saturation point, and water collects on any surface available - Frost is frozen condensation - Dew is liquid condensation Dewpoint is the temperature that the air must be cooled to (under constant pressure) to reach saturation and cause condensation Hoarfrost

37 Essentially low level clouds Fog Basically when like a low cloud, or but slightly different...how? created airaltitude is heated Created anytime there is a contrast in moisture and temperature between air and the ground. ooled in the contrast to land or water g Essentially low level clouds created when air is heated or cooled in contrast to land or water Steam fog Valley fog

38 Rime ice or Rime frost Wind is blowing this way rime frost or ice forms on the upwind side of obstructions as water droplets from fog freeze onto the surface