In the News: Abscission cells in red (UW/Madison plant image teaching collection) 1 15 ft. + snowbanks at Alpental http://www.npr.org/templates/story/story.php?storyid=114288700 ski area, Snoqualmie Pass, WA. Feb. 2006
In the News: http://www.coaps.fsu.edu/~maue/tropical/ 2 15 ft. + snowbanks at Alpental ski area, Snoqualmie Pass, WA. Feb. 2006
Precipitation Processes (ERTH 303, 2 November 2009) a. Growth of cloud droplets b. Distribution and forms of precip. c. Measuring precipitation d. Cloud seeding 3 Precipitation falling as snow.: how does it happen?
c. Measuring precipitation Raingages: Sparse network Point measurements Sensitive to winds, splash, location Textbook figure 7-18 4
c. Measuring precipitation Doppler radar: Real-time info. Semicontinuous coverage Precipitation estimate from backscatter of microwave Textbook figure 7-20 radiation National Radar Mosaic: http://radar.weather.gov/conus/index.php 5
c. Measuring precipitation Snow Course: Snow-water water equivalent: 10:1, but variable (4:1 to 50:1) Point measurements Extensive network Montana Snow Course Data: http://www.wcc.nrcs.usda.gov/cgibin/snow_rpt.pl?state=montana New World Snow Course maker near Mt. Ellis, Gallatin National Forest, MT. 6
c. Measuring precipitation 7
c. Measuring precipitation SNOTEL: Automated Point measurements Extensive network Montana SNOTEL Sites: http://www.wcc.nrcs.usda.gov/snotel/montana/montana.html http://www.wcc.nrcs.usda.gov/cgibin/precup-wcgraph.pl?state=mt 8
c. Measuring precipitation 2007 2008 2009 9
d. Cloud Seeding Cloud Seeding: Objective = convert supercooled droplets into ice to initiate the Bergeron Process Dry ice (-78 C, -108 F), injected via plane Siler iodide, initiates Bergeron processes by acting as an ice nucleus at temps. as high at -5 C( (23 F), because it s a six-sided molecule http://news.bbc.co.uk/2/hi/asia-pacific/8337337.stm 10
Chapter 8: Atmospheric Circulation http://www.cdc.noaa.gov/people/klaus.wolter/mei/ 11 Sea surface temperature index during mild 2006 El Nino. http://earthobservatory.nasa.gov/newsroom/newimages/images/elnino_jas_20060905_lrg.jpg
Chapter 8: Atmospheric Circulation a) Global atmospheric circulation b) Semipermanent Pressure Cells c) Upper Troposphere Patterns d) Oceans e) Major Wind Systems f) Air-Sea Interactions 12 Sea surface temperature index during mild 2006 El Nino. http://earthobservatory.nasa.gov/newsroom/newimages/images/elnino_jas_20060905_lrg.jpg
Spatial and Temporal Scales Term Macroscale Temporal Scale Spatial Scale Example Planetary Weeks or longer 1000-40 40,000000 km Westerlies and trade winds Synoptic Days to weeks 100-5000 km Mid-latitude cyclones, anticyclones, and hurricanes Mesoscale Minutes to hours 1-100 100 km Thunderstorms, tornadoes, and land-sea breeze Microscale Microscale Seconds to < 1 km Turbulence, dust minutes devils, wind gusts 13
a) Global atmospheric circulation Well-defined pressure patterns exist across the globe: Induces winds Largest wind systems define global atmospheric circulation 14
a) Global atmospheric circulation Single-cell model: winds All planet = ocean Single convection cell per hemisphere mer ridional flow / Textbook figure 8-2 zonal flow / winds 15
a) Global atmospheric circulation Three-cell model: 3. Polar 2. Ferrel 1. Hadley 2. Ferrel Textbook figure 8-2 3. Polar 16
a) Global atmospheric circulation Three-cell model: 1. Hadley cell: heat-driven Rising air near tropics, sinking air at subtropics InterTropical Convergence Zone (ITCZ) [or equatorial low], near 0 latitude Subtropical High, near 20-30 latitude ITCZ NASA: http://earthobservatory.nasa.gov/newsroom/newimages/images/itcz_goes11_lrg.jpg
a) Global atmospheric circulation Three-cell model: 1. Hadley cell: heat-driven Northeast and Southeast trade winds Doldrums, Horse Latitudes Strongest in winter 18
a) Global atmospheric circulation Three-cell model: 2. Ferrel cell: indirect cell Circulates air between subtropical high and subpolar lows Dominated by westerlies (both hemisphere) 19
a) Global atmospheric circulation Three-cell model: 3. Polar cell: heat-driven cell Circulates air from polar high to subpolar low Dominated by polar easterlies 20
a) Global atmospheric circulation Three-cell model: how accurate is it? Hadley cells are close approximations of real world Ferrel and polar cells do not approximate the real world Model is unrepresentative ti of flow aloft Continents and topographic irregularities cause model oversimplification 21
Atmospheric Circulation a) Global atmospheric circulation b) Semipermanent Pressure Cells c) Upper Troposphere Patterns d) Oceans e) Major Wind Systems f) Air-Sea Interactions 22 Sea surface temperature index during mild 2006 El Nino. http://earthobservatory.nasa.gov/newsroom/newimages/images/elnino_jas_20060905_lrg.jpg
b) Semipermenant Pressure Cells Dynamically or thermally induced Undergo seasonal fluctuations Northern Hemisphere cells: January: Aleutian Low Icelandic Low Siberian High Bermuda-Azores High July: Bermuda-Azores High Tibetan Low Hawaiian High 23
b) Semipermenant Pressure Cells July January Textbook figure 8-4 24
b) Semipermenant Pressure Cells Seasonal fluctuations impact our climate: e.g. Migration of the ITCZ and rains in the Sahale Open Link: http://geography.uoregon.edu/envchan ge/clim_animations/flash/mslp.html 25 Textbook figure 8-5
b) ITCZ - meeting of S. and N. Hemi. Trade winds 26 Textbook figure 8-5