Water and Atmospheric Moisture. Lecture 5 Atmospheric Moisture & Precipitation. Water on Earth. Water Distribution. Land & Water Hemisphere

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1 Lecture 5 Atmospheric Moisture & Precipitation Water and Atmospheric Moisture Water and the Hydrosphere Stages of Water - Relative Clouds Fog Geog210 Physical Geography Professor Paluzzi Water on Earth Worldwide equilibrium 97.22% - oceans 2.78% - fresh water 77.14% of fresh water is in long term storage Glaciers.333% - lakes, rivers, streams Subsurface - groundwater 22% Water Distribution 50% of freshwater is contained in the 7 largest lakes Lake Baykal located in southeast Siberia - largest freshwater reserve in the world 400 miles long, a mile deep Earth s Water Land & Water Hemisphere Not equally distributed Northern Hemisphere Land Dominates HydrologicCycle.swf Southern Hemisphere Water dominates Water Hemisphere Western parts of northern and southern hemispheres 1

2 Saline Lakes (Seas) ¼ of 1% of surface water are in saline lakes Shrinking Aral Sea 60% of the sea s total volume has disappeared Excessive utilization for irrigation led to the progressive drying of the sea. Use of rivers feeding the sea for agricultural irrigation Salinity increased from 10g/l to 40g/l destroying animal and vegetation species Saline Lakes (Seas) Surface area has decreased by 45% and water volume by 60%. complete separation into small sea and large sea Economic and cultural damages Severe shortage of water for 50 million people Environmental problem - ships The Shrinking Aral Sea The Shrinking Aral Sea Mosaic of satellite images, The Aral Sea on May 29, 1973 from Landsat-1 The Aral Sea on August 19, 1987 from Landsat-4 The Aral Sea on July 29, 2000 from Landsat Saline Lakes (Seas) Caspian Sea the worlds largest lake Roughly the size of Montana Ural and Volga Rivers feed the lake, but not rivers flow out Upstream harvesting of water Less water reached the lake evap. leaving the salt Threatening fishing industry Continued to shrink until the late 1970 s Recently more rain Increased depth Saline Lakes (Seas) Lake Balkhash (Kazakstan) fifteenth largest lake in the world Roughly the size of Connecticut and Rhode Island combined Several rivers feed the lake, but not rivers flow out The Ili River sediment (west) 2

3 U.S. Saline Lakes Mono Lake, CA Basin of Sierra Nevada Formed about 3 million years ago Mono Lake is the terminal point in a watershed fed from melting runoff. U.S. Saline Lakes Great Salt Lake, UT About 75 miles long, and 28 miles wide, and covers 1,700 square miles Has a maximum depth of about 35 feet Typically 3 to 5 times saltier than the ocean Fish free, the largest aquatic critters are brine shrimp and brine flies Three Stages of Water Solid as water cools, it contracts in volume (until 39 F) then expansion occurs Solid Liquid (Freezing & Melting) Ice cube tray Frost heaves Road/pavement damage Solid Gas Sublimation Liquid Process of ice changing directly to a gas Gas -> directly to solid Water attaches to ice crystals (frost) Gas evaporation/condensation Hydrologic Cycle Water moves among the ocean, atmosphere and land Evaporation Precipitation Transpiration from plants Runoff Sinks into soil Recharge of groundwater Hydrologic Cycle Precipitation: Particles of liquid water or ice that fall from the atmosphere and may reach the ground. water vapor in the air The maximum quantity of moisture that can be held in the air depends on air temperature A function of temperature 3

4 Relative humidity - the ratio of water vapor in the air, compared to maximum water vapor possible Tells us how close we are to saturation (100%) Dew point temperature at which air becomes saturated Further cooling results in condensation (dew) Temperature changes Lower temperature relative humidity rises Raise temperature relative humidity decreases Relative Actual Water Vapor in Air Relative = Maximum water vapor possible X 100 in the air at that temperature Highest at dawn when temperature is lowest ie. Dew on car in the morning Lowest in late afternoon temperatures highest Moisture in the Atmosphere Relative humidity Highest at dawn when temperature is lowest Lowest in late afternoon temperatures highest Cooler air = lesser maximum water vapor possible Maximum water-vapor possible Instruments Hair Hygrometer Human hair changes length based on humidity Water Vapor 5 a.m. 100% Relative Water Vapor 11 a.m. 50% Relative Water Vapor 5 p.m. 20% Relative Warmer air = greater maximum water vapor possible Relative Sling Hygrometer 2 thermometers 1 dry, records air temperature 2 wet, records temperature that is lowered by the evaporation of the wet bulb High humidity little evaporation Low humidity more evaporation The Adiabatic Process Atmospheric pressure decreases with altitude, so: As a parcel of air rises pressure on the parcel decreases air expands and cools As a parcel of air descends pressure on the parcel increases air is compressed and warms 4

5 Adiabatic Processes Dry adiabatic rate - rate at which rising air is cooled by expansion when no condensation is occurring: 5.5 F / 1000 ft Moist adiabatic rate Between 2.2 & 4.9 F / 1000 ft Clouds and Fog Clouds a great mass of moisture droplets As air rising, it cools. When it reaches it s dew point (saturation) further cooling results in moisture droplets forming through condensation Cloud condensation nuclei microscopic particles present in the atmosphere around which clouds form Cloud Types and Identification Altitude and shape are key to cloud id ing Low Clouds up to 6500 Stratus, stratocumulus, nimbostratus Middle Clouds 6500 to 20,000 Altostratus, altocumulus High Clouds 20,000 to 43,000 Cirrus, cirrostratus, cirrocumulus Vertically Developed Clouds near surface to 43,000 Cumulus, cumulonimbus Figure 7.20 Cloud Types & Identification: Low Stratus uniform, featureless, grey Up to 6500 composed of water only Cloud Types & Identification: Low Stratocumulus soft, gray, rounded masses, irregular shaped: Up to water Cloud Types & Identification: Low Nimbostratus up to 6500 : water : Stratus clouds that yield rain Gray, dark, low with drizzling rain 5

6 Cloud Types & Identification: Middle Altostratus thin to thick, uniform gray sheet or layer similar to stratus, except higher altitudes Sun s outline visible ,000 Composition ice and water Dangerous to aircraft cause ice to buildup Cloud Types & Identification: Middle Altocumulus patches of cotton balls, arranged in lines or groups Often in front of a cold front, precede thunderstorms on hot, humid summer days ,000, ice & water Cloud Types & Identification: High Cirrus wispy, feathery, hair-like 20,000 43,000 icy composition Indicate an incoming storm Cloud Types & Identification: High Cirrostratus thin veil of sheets of ice crystals, milky, results in halos around the sun and moon. Indicates precipitation will occur within hours Ice Cloud Types & Identification: High Cirrocumulus dappled, puffy appearance Mackerel sky High altitude 20,000 40,000 feet Almost exclusively Icy composition Indicate incoming storms Cirrocumulus differs from Cirrus and Cirrostratus in that it is rippled or subdivided into very small cloudlets Cloud Types & Identification: Vertical Cumulus often called Fair Weather Clouds Mostly detached clouds, generally dense and with sharp outlines The sunlit parts of these clouds are mostly brilliant white. Their base is relatively dark and nearly horizontal may be composed solely of water droplets, super-cooled water droplets, ice crystals, snowflakes, ice pellets or a combination of all Near surface to 43,000 6

7 Cloud Types & Identification: Vertical Cumulonimbus mushroomed shaped Dense, heavy, lots of vertical development Associated with dark thunderstorms and heavy showers Thunderheads from surface to 43,000 Upper air flow (wind) flattens the top Cloud Types & Identification Cumulonimbus Development anvil shaped Updraft/downdraft lift and drop of water droplets and ice crystals creates static electricity charges, resulting in thunder/lightning Generally occur in afternoon, as heat builds during day, but cold fronts meeting the warm fronts push air vertical Fog Fog a cloud layer that is on the ground; visibility restricted to 1km or less Tells us the air temperature and dew-point temperature are nearly identical and the air is saturated Advection fog Advection fog forms when warm moist air moves over a cold surface Evaporation fog Evaporation Fog when cold air lies over warm water (lake, ocean surface, swimming pool) Sea smoke Upslope fog Upslope fog warm, moist air flows to higher elevations along a hill or mountain Adiabatic cooling 7

8 Valley fog Valley fog cold air is denser than warm air, it occurs when cold air settles in the valleys when temperature meets the saturation point Radiation fog Radiation fog : formed when temperature of the air at ground level falls below dew point 8