ATM 10 Severe and Unusual Weather

Transcription

1 ATM 10 Severe and Unusual Weather Prof. Richard Grotjahn L1

2 Questions: Why are there 2 arcs? Why does the order of colors reverse? West Plainfield, CA R. Grotjahn

3 Question: Does this cloud tell a story? Mt. Hood, OR R. Grotjahn

4 Question: Is this little dust cloud dangerous? Stapleton Airport, CO R. Grotjahn

5 Questions: Is this a harmless dust devil at sunset? What do you think now?

6 Questions: Where is it safe during lightning? Where is it safe during a tornado? National Geographic

7 Questions: Would you be prepared for an ice storm? R U ready for no power or other utilities?

8 Questions: Would you be prepared for a hurricane like Katrina? Or Ike? They were!

9 Lecture topics: Course overview Administration info Severe and unusual weather topics VOTD (video of the day) Atmospheric Properties Atmospheric composition Vertical structure of atmospheric pressure & temperature Demo: Making a cloud

10 Course Overview - Administration Course administration summarized here. Details in discussion and online. That information on ppt slides that can be found on the course web page Lectures, assignments, & other information to be posted on the smartsite.ucdavis course website: Canvas materials accumulate during the course.

11 ATM 10 Severe and Unusual Weather Fall 2018, MW 12:10-1:00, Giedt 1002 G.E. CREDIT: Science and Engineering; visual, scientific, writing literacies WEBSITE: INSTRUCTOR: Prof. Richard Grotjahn, 231 Hoagland Hall Phone: ; Atmospheric Science Program, Dept. of Land, Air and Water Resources TAs: Dani Caputi Minmeng Tang Office Hours: (W: 10:30-11:30a) (Tu: 11:00a-12:00p) Location for office hours: 151 Hoagland Hall DISCUSSION SECTIONS: 12:10-1:00p Thursday 124 Hoagland 1:10-2:00p Thursday 124 Hoagland 12:10-1:00 Friday 124 Hoagland TEXT: NONE. Some may want to look at Fry et al Some pages are referenced from it in the course outline. It is OPTIONAL.

12 Course Overview - Administration Goals: A GE science course should: Teach some scientific methods, and Teach some scientific principles This course does so in an interesting context. You will learn about: 8 different kinds of atmospheric optical phenomena 14 different kinds of severe weather Will there be equations? (Yes, 8 simple equations, this is a science course after all!) Will you have to memorize formulas? No, just how to recognize and use them. So. don t worry!) Will there be pictures, videos & demonstrations? (Yes, lots of them)

13 ATM 10 Website Course postings of lectures, problem sets, videos and animations are all folders in the Files link. Shown is 2018 test version; similar to actual Homework assignments here Admin has course syllabus and this presentation. Note expanded folder. Lecture notes here TA discussion notes here

14 Course Syllabus Logistics & Grading Monitor the syllabus in the Files, Course Administration folder at the course website: cdavis.edu/

15 Course Syllabus - Calendar Monitor the syllabus in the Files, Course Administration folder at the course website: cdavis.edu/

16 Course Rules & Suggestions Some rules: 1. Homework is due by end of lecture on date indicated in syllabus. Homework turned in after that time receives 0% credit. 2. Homework is submitted on paper to your TA. 1. Do not submit homework as unless arranged prior with your TA. 2. If there are multiple pages, please staple all pages together. 3. Print out your answers using a word processor: 1. For any written part of an assignment 2. Exceptions: 1. Mathematical formulas and calculations can be legibly hand-written 2. Diagrams & charts can be hand-drawn (if clear) 3. Do your own homework. 1. Duplicative homework answers may cause both to get 0% credit 4. No early or late offerings of midterm 5. Exams and quizzes are closed book meaning closed notes. Some suggestions: 1. For more information & updates: routinely check the course website 2. Plan your timing of activities using the syllabus 3. Review the posted lectures after if not before lecture 4. Questions? Ask your TA or the instructor. 5. Check your campus our way to alert you to stuff. Note: To reduce paper usage, homework assignments will not be handed out (but posted on the course smartsite in the Resources heading)

17 Course Overview class meetings What to expect in lecture: powerpoint lecture (to introduce concepts) video(s) demonstration(s) weekly mini feedback form weekly turn in of homework (location for midterm and final) What to expect in discussion: Work through example problem similar to current homework Return of graded assignments, midterm Revisit any topic that people missed as noted by the TA when doing grading Revisit topics from lecture identified by students on the mini feedback form.

18 Most lectures will have a video of the day Various topics, sometimes directly related to the lecture. Video of the Day

19 Course Overview - Subjects Unusual & common optical events 1. Why is the sky blue? 2. Why are there rainbows? 3. What causes mirages? 4. What causes halos and related phenomena?

20 Course Overview - Subjects Clouds, lots of clouds 1. How they form 2. Common clouds 3. Unusual clouds 4. What they tell us about the weather

21 Severe weather organized by size ( scale ) Large Scale: -heat waves, -jet stream turbulence -mid-latitude frontal cyclones (cold air outbreaks, ice storms, blizzards) Course Overview - Subjects Medium Scale: -hurricanes -floods -windstorms Small Scale -thunderstorms (hail, downbursts, lightning, tornados, flash floods)

22 Severe weather events Large Scale: -jet stream turbulence -heat waves -cold air outbreaks -ice storms -blizzards Medium Scale: -hurricanes -floods -windstorms Small Scale -thunderstorms -hail -downbursts -lightning -tornados Course Overview Large Scale Subjects

23 Severe weather events Large Scale: -jet stream turbulence -heat waves -cold air outbreaks -blizzards -ice storms Medium Scale: -hurricanes -floods -windstorms Small Scale -thunderstorms -hail -downbursts -lightning -tornados Course Overview Medium Scale Subjects

24 Severe weather events Large Scale: -jet stream turbulence -heat waves -cold air outbreaks -blizzards -ice storms Medium Scale: -hurricanes -floods -windstorms Small Scale -thunderstorms -hail -downbursts -lightning -tornados Course Overview Small Scale Subjects

25 Severe weather Course Overview Severe Weather Subjects Question: Which is more dangerous?

26 Which is more dangerous? Answer: It depends on the measure. Heat waves are the most dangerous to people. Hurricanes and Floods cause the most economic loss

27 Basic Atmospheric Properties

28 Atmospheric Composition Gas Symbol Percent by volume Nitrogen N (in dry air) Oxygen O (in dry air) Argon Ar 0.93 (in dry air) Carbon Dioxide CO (in dry air) Water vapor H 2 O ~0 to 4 % measured

29 Can we see air? Only indirectly. Nitrogen, oxygen, argon, water vapor, carbon dioxide, and most other gases are invisible. Clouds are not gas, but condensed vapor = liquid droplets or ice crystals. Smog can be visible, especially when it contains reactants of nitrogen and ozone.

30 If I can t see it, how do I know there is air? You can feel the air blowing as wind, of course. Including when you breathe in and out! You can see other evidence, for example: Ears pop as you ascend/descend mountain Ears pop during airplane ascent/descent Beautiful sunsets

31 The Atmosphere s Vertical Structure

32 The Thin Atmosphere 99% of atmospheric gases, including water vapor, extend only 30 kilometers (km) above earth's surface. Figure 1.2 (Ahrens) Most of our weather occurs within the lowest 10 to 15 km. (the orange layer in figure above)

33 Vertical Structure: Atmospheric Layers ionosphere Note the orange Layer. Stratopause Mesopause 5 layers based on air properties 1 is electrically charged ionosphere 4 defined by how air temperature changes with pressure and latitude. Between layers are key levels. Weather & wind differ between layers. Most weather occurs in the troposphere.

34 Vertical Structure of Pressure & Density Gravity pulls gases toward earth's surface. Pressure is weight of air above. Weight = mass of air times acceleration of gravity. The orange Layer In space photo Figure 1.8 Whole column of air at sea level weighs: = 14.7 psi = mb = in.hg.

35 Why is the line curved? Red line is curved since: 1. Air below is compressed from the weight of air above. 2. Why? Compression makes: 1. density increase as elevation becomes lower. 2. So, amount of mass in a layer below is > mass in layer the same depth above. 3. So, pressure difference from top to bottom of a layer increases as go lower. That is description in words, now consider a picture...

36 Consider two examples. Left example: Contents NOT compressed by layers above; so density ρ same in each layer. Change of P from top to bottom of each layer is same for each layer. Pressure at bottom of each layer is P and P is plotted as pink line. Right example: Air layers above COMPRESS air below; so weight of air above makes ρ increase for layers below. More density means more mass so P change across layer increases too. P at bottom of each layer plotted as blue line. Why is the red line curved? Same layer depths (no comp.) ρ= 1, P=1 ρ= 1, P=2 ρ= 1, P=3 ρ= 1, P=4 ρ= 1, P=5 ρ= 1, P=6 NO compression so density same in each layer. P change is a straight line. Compressed air ρ= 1, P= 1 ρ= 1.2, P= 2.2 ρ= 1.44, P= 3.64 ρ= 1.73, P= 5.37 ρ= 2.07, P= 7.44 ρ= 2.49, P= 9.93 Let compression increase density by 20% from layer above. P change is a curved line.

37 Consider two examples. Left example: Contents NOT compressed by layers above; so density ρ same in each layer. Change of P from top to bottom of each layer is same for each layer. Pressure at bottom of each layer is P and P is plotted as pink line. Right example: Air layers above COMPRESS air below; so weight of air above makes ρ increase for layers below. More density means more mass so P change across layer increases too. P at bottom of each layer plotted as blue line. Why is the red line curved? Same layer depths (no comp.) ρ= 1, P=1 ρ= 1, P=2 ρ= 1, P=3 ρ= 1, P=4 ρ= 1, P=5 ρ= 1, P=6 NO compression so density same in each layer. P change is a straight line. Compressed air ρ= 1, P= 1 ρ= 1.2, P= 2.2 ρ= 1.44, P= 3.64 ρ= 1.73, P= 5.37 ρ= 2.07, P= 7.44 ρ= 2.49, P= 9.93 Let compression increase density by 20% from layer above. P change is a curved line.

38 Consider two examples. Left example: Contents NOT compressed by layers above; so density ρ same in each layer. Change of P from top to bottom of each layer is same for each layer. Pressure at bottom of each layer is P and P is plotted as pink line. Right example: Air layers above COMPRESS air below; so weight of air above makes ρ increase for layers below. More density means more mass so P change across layer increases too. P at bottom of each layer plotted as blue line. Why is the red line curved? Same layer depths (no comp.) ρ= 1, P=1 ρ= 1, P=2 ρ= 1, P=3 ρ= 1, P=4 ρ= 1, P=5 ρ= 1, P=6 NO compression so density same in each layer. P change is a straight line. Compressed air ρ= 1, P= 1 ρ= 1.2, P= 2.2 ρ= 1.44, P= 3.64 ρ= 1.73, P= 5.37 ρ= 2.07, P= 7.44 ρ= 2.49, P= 9.93 Let compression increase density by 20% from layer above. P change is a curved line.

39 Clouds Condensed water vapor: either ice crystals or liquid droplets Droplets much smaller than raindrops. Droplets form on a bit of dust, sea salt, etc That bit called a condensation nuclei. Most clouds form as air rises. Rising air encounters lower P and T This leads to our demonstration

40 Demo: Clouds in bottles Various ways to make cloud in a bottle: Plastic soda bottle with water and condensation nuclei inside, compress (P rises) then let go (P drops) Pump air from (big) bottle until cloud forms. Recall: need condensation nuclei. Try a bit of smoke from match. Real clouds have similar transparency.

41 Lecture Summary: Weather occurs on many scales large: jet stream turbulence, heat wave medium: hurricanes, floods, windstorms, blizzard, ice storm small: thunderstorms (hail, lightning, tornados, etc.) Composition permanent dry air gases: N 2 ~ 78%, O 2 ~ 21% Ar ~ 1% water is primary variable gas: ~0 to 4% Atmosphere vertical structure; as elevation increases: Air is compressible: so density decreases as elevation increases P is weight of air above; P decreases as go up. Sea level P ~1000 mb T decreases, then increases, then decreases, then increases as you measure T while ascending in the atmosphere (on average) T variations define distinct atmospheric layers: troposphere, stratosphere, mesosphere, thermosphere. Tropopause, stratopause, mesopause between adjacent layers. Troposphere: where most weather occurs; on average ~10 km deep One more layer: ionosphere electrically charged, plays a role in formation of lightning. Clouds form: Droplets or ice crystals condense on condensation nuclei In rising air -> T and P decrease until cloud forms Recall Demo.

42 End of lecture 1 Next time: units, ideal gas law, and scattering (several optical phenomena)