Atm Ocn 100 Edition 1nd Lecture 13 Outline of Last Lecture I Weather of the Day II More on Dry Adiabatic Process III More on Moist Adiabatic Process IV Lapse Rate V Stability a Conditional Instability b Implications of Conditional Instability VI Stuve Diagram VII LFC and LCL a Implications of LFC VIII Mechanisms to lift a parcel to LFC Outline of Current Lecture II Weather of the day III How do clouds form IV Aerosols V Dry Haze VI Wet Haze VII More on how do clouds form a Curvature effect b Swollen aerosols c Super saturation VIII What exactly is a cloud IX What is rain a Why do large droplets fall faster than small droplets b What is rain continued Current Lecture Reminders Test coming up a week from Wednesday Review session next Monday Review sheet will be put up Today we are going to be going over Microphysics The test will include Microphysics and there will be some additional lectures on Thunderstorms We will not get to Tornados before the test So everything we have covered so far Test will be multiple choice and true false We only have to read through Thunderstorms for the test Homework problems on the PowerPoint for today we should do them Do those homework problems because that is not covered in the book so we should really listen to that Best way to study for Microphysics is try to answer the problems they aren t due till after the test but we should know how to do them for the test Weather of the day Same data you can get on AOS website as well 250 mb level map from the GFS model This model shows the wind speed in knots The black lines are the heights This is from 6z this morning If we jump ahead to October 14 th we can see there is a strong Jetstream going to Pacific Northwest Purple s are up to 180 knots which is quite strong wind at this level There is nice trough forming over the U S If we go more ahead in time from the 14 th to the 15th we can see the Jetstream goes more out into the U S the wind speed is still 150 knots We can see a trough and a ridge right at the top Areas from a trough to a ridge have upper level divergence They are very close together so a lot of divergence happening in that area If we go to a surface map at the same time and start at October 14 th the blue lines are the isobars and precipitation is shown If we go to the 15th we see at the same areas between where there was a ridge and a trough we see a low that is 972 mb that is really strong If this happens we can expect a really windy day on the 15th This is 9 days out so it is very subject to change Typical surface pressure is pressure at sea level if no elevated typography A typical one is 1 013 mb A very strong cyclone low would have pressure in the 980 s mb typically A hurricane probably is in the 970 s which is what we are looking at here This 972 mb is very strong equivalent to a hurricane We don t usually see that in the Midwest if we see this at sea level it is usually on the coast Can happen there because contrast over warm air over water and cold air This is happening over Ontario so this is very unusual This is unusual because it is inland not along the coast And it is unusual because it seems to be associated with the subtropical jet This could be from typhoon that happened from Japan The last one happened in 2010 It had a name called Chiclone because it was in Chicago It was very damaging It was centered in Northern Minnesota for a time This was a very important storm We didn t predict that low of a pressure in advance knew it was going to be strong but didn t realize how strong But as days approach did realize how strong So maybe by next Monday we will be excited and maybe see something historic coming in A little different than 2010 event in that typhoon was actually a super typhoon The Japan typhoon was strong but not a record So maybe not match the strength of this from 2010 but maybe something similar nonetheless Back to lecture Microphysics How does Precipitation form in Clouds Homework is due Friday October 17 2014 Microphysics Problems end of the Microphysics PowerPoint TYU Ch 18 2 4 5 10 15 18 27 29 TYU Ch 19 1 2 3 6 9 10 11 16 18 How do clouds form Clouds begin with aerosols Aerosols are small solid particles of size typically amount 1 micron across 1 micron 1 1000 of a millimeter Aerosols can reduce visibility by scattering light This reduction of visibility is called Haze We divide aerosols into Hygroscopic aerosols soluble in water Hydrophobic aerosols insoluble in water Extra notes Even though we have saturation that doesn t actually produce precipitation Saturation will lead to formation of cloud droplets but how do the cloud droplets lead to formation of rain droplets Rain droplets are much larger then cloud droplets If all cloud droplets could grow larger to the size of rain droplets this would take 10 times as much water than we have in atmosphere to allow this to happen Reason There simply is not enough water available even if all the water condensed to turn cloud droplets into rain droplets Hygroscopic Ability to attract and hold water molecules from the surrounding environment Hydrophobic a molecule that is seemingly repelled from a mass of water Aerosols Where do they come from Aerosols occur from many sources Sea spray leaves salt aerosols in the air including plankton algae etc Fires leave smoke consisting of elemental carbons sulfur and other chemicals Wind blown dust can be quite small major sources are Sahara Mongolia These are major sources of insoluble nuclei e g silicates important to ice formation Aerosols are emitted by plants and forests Aerosols include spores pollens or condensed VOCs like terpens Sulfur dioxide emitted from combustion or volcanic activity condenses to form sulfuric acid drops or sulfate particles Our sense of smell detects aerosols in the air You can smell the terpens in a rain forest the salty air along the coast the sulfurs and carbons emitted by refineries and so on These sources tend to form hydrophobic but can become hygroscopic by picking up other things in the air 2 types of haze that form dry haze and wet haze Dry Haze Dry Haze results from suspended dry aerosols that scatter light They can be hygroscopic aerosols at low humidity or hydrophobic aerosols at any humidity Often these aerosols enter the air as a gas but chemically evolve and condense into particles NO gas from Methane combustion becomes nitrate particles SO2 gas from coal combustion becomes sulfate particles These aerosols will reduce visibility