Class Note for NATS 101 at UA
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Date Created: 02/06/15
TOPIC 1 2 Introduction to Models UNDERSTANDING SYSTEMS amp FEEDBACKS Class notes pp 7175 When one tugs at a single thing in nature one nds it attached to the rest of the world John Muir SYMBOLIC NOTATION use of a picture or diagram instead of words abbreviation symbol or acronym instead of spelling out the whole word or concept NATS101GC amp x or IPCC SYMBOLIC NOTATION cont NUMBERS 1 2 8 38x10 4 Elements and molecules H He H20 CO2 Formulas amp Equations y a bx equation for a straight line p71 SYMBOLIC NOTATION cont MODELS WHAT IS A MODEL 0 a representation of something usually miniature or not to scale 0 an example for imitation or emulation a person or thing that serves as a pattern 0 an analogy or analogue of something p 71 WHAT IS A MODEL 0 quota description or analogy to help visualize something that cannot be directly observedquot 0 or quota system of postulates data and inference resented as a mathematical de ription of an entity or state of a 39 quot Note the word system Daisyworld An Introduction to Systems WHAT IS A SYSTEM SYSTEM a set of interacting components 0 SYSTEM MODEL a set of assumptions rules data and inferences that define the interactions among the components of a system and the significant interactions between the system and the universe outside the system p71 SYSTEM DIAGRAM A diagram of a system that uses graphic symbols or icons to represent components in a depiction of how the system works One example of a system diagram for a model used in global change studies v v v v 39 Pivslcalclinatewstem Atmospheric PhysicsIDynznics 3 39 Chwl 3ngw HW quotm Tweslrial ocmn 393 v EnayylMoisiwe I A V NM 7H g Stil Globd Moistre External Forcing Another more complicated system diagram EDNEEPTUAL HDDEL nl Earth System prunes nuemung nn timescales n1 names In cenumes ii mm H w mm any wcomsw N u mqv 39 an leescme a ham 10 days on Hmesmm m mnnms m seasnns a ux n cancenlmhnn COM PON ENT Component def An individual part of a system A component may be a reservoir of matter or energy a system attribute or a subsystem COUPLING Coupling de The links between any two components of a system Couplings can be positive or negative TEAM PARTICIPATION POINTS lowtech version 0 As the lecture continues there will be 7 questions and the opportunity for your groups to earn an ACTIVE PARTICIPATION POINT today 0 Each group will get a PINK index card PUT YOUR Group on it A question will be asked the team confers and then the team answers If correct your team gets a point We ll keep this up until every team has earned a point for its members ALL TEAM MEMBERS PRESENT TODAY SIGN THE CARD before you turn it in TO GET YOUR POINT amp TURN IT IN TO ONE OF THE TA S A coupling between an electric blanket temperature component and a body temperature component blanket temperature If the electric blanket s temperature INCREASES My The person s Mm body temperature will also INCREASE Q1 What type of COUPLING IS THIS 1 Positive 2 Negative p71 A coupling between a person s body temperature and an electric blanket s temperature If the person s body temperature INCREASES and he gets too hot The electric blanket s temperature control will be turned down and the blanket temperature will DECREASE Q2 What type of COUPLING IS THIS 1 Positive 2 Negative p71 THE RULE how to tell if it s a positive or negative coupling Positive couplings have a solid arrow with a normal arrowhead pointing in the direction of the coupling Negative couplings have an open circle arrowhead pointing in the direction of the coupling FEEDBACKS Feedback mechanism de a sequence of interactions in which the nal interaction in uences the original one Feedbacks occur in loops 9 Feedback Loop def A linkage of two or more system components that forms a ROUNDTRIP flow of information Feedback loops can be positive or negative A positive feedback is an interaction that amplifies the response of the system in which it is incorporated selfenhancing amplifying A negative feedback is an interaction that reduces or dampens the response of the system in which it is incorporated selfregulating diminishes the effect of perturbations One way to remember the effect that a NEGATIVE feedback loop has is to think of the word quotnegligiblequot ie a perturbation or disturbance in a system characterized by a negative feedback loop will be able to adiust to the perturbation and ultimately the effect on the system will be negligible FEEDBACK LOOP Q3 What kind of FEEDBACK LOOP IS IT 1 Positive 2 Negative body 39 blanket temperature temperature THE RULE how to tell if it s a positive or negative feedback LOOP Count the of number of NEGATIVE COUPLINGS If there is an ODD of negative Couplings the loop is NEGATIVE O If there is an EVEN of negative couplings the loop is POSITIVE 39 O L om One more term EQUILIBRIUM STATE a state in which a system is in equilibrium that is the state in which the system will remain UNLESS something disturbs it An equilibrium state can be stable or unstable Take notes The presence of FEEDBACK LOOPS leads to the establishment of EQUILIBRIUM STATES Negative feedback loops establish STABLE equilibrium states NEGATIVE LOOP STABLE EQUILIBRIUM recall negative feedback self regulating STABLE EQUILIBRIUM STATES are resistant to a range of perturbations ie system responds to modest perturbations by returning to the stable equilibrium state Take notes A negative feedback loop can also be described as a STABLE EQUILIBRIUM STATE A modest response that disturbance tends to return the short term I system to its perturbation equilibrium state Stable equilibrium state Take notes A LARGE or more persistent disturbance a forcing can carry the system to a different equilibrium state so there area some limits to stability even in a stable state Stable equilibrium Stable equilibrium state state Everyday life example Proper alignment of dual control electric blanket person A s FW person A s body blanket temperature q temperature 39 persona s b parsona39s temperature temperature Improper alignment Q4 What kind of FEEDBACK LOOP IS IT 1 Positive 2 Negative A POSITIVE FEEDBACK LOOP that amglifies the effect p 73 A positive feedback loop can also be described as an UNSTABLE EQUILIBRIUM STATE the slightest disturbance from a comfortable state may lead to system adjustments that carry the system further and further from that state Stable equilibrium Stable equilibrium state state State of the system such as temperature RECAP The presence of FEEDBACK LOOPS leads to the establishment of EQUILIBRIUM STATES Negative feedback loops establish STABLE equilibrium states that are resistant to a range of perturbations the system responds to modest perturbations by returning to the stable equilibrium state 0 Positive feedback loops establish UNSTABLE equilibrium states A system that is poised in such a state will remain there indefinitely However the slightest disturbance carries the system to a new state Take notes LINKING TO GLOBAL CHANGE In Global Change science we are concerned about disturbances that both humans and natural factors can produce in the Earth system eg increasing carbon dioxide and whether or not the Earth can adjust to these and have a stable equilibrium state or be thrown into an unstable state due to positive feedback loops WATER VAPOR Feedback in the EarthAtmosphere 05 What kind of FEEDBACK LOOP IS THIS 1 Positive 2 Negative Atmospheric T5 H20 effect POSITIVE FEEDBACK LOOP that amplifies the effect Atmospheric H20 Greenhouse effect OUTGOING INFRARED ENERGY FLUX I TEMPERATURE Feedback 06 What kind of FEEDBACK LOOP IS THIS 1 Positive 2 Negative Surface Outgoing temperature IR flux p73 NEGATIVE FEEDBACK LOOP that is selfregulating Surface temperature Outgoing IR flux Ok so what s this Daisyworld Climate System all about and why should I care White daisycovered Gray soil regions SNOW AND ICE ALBEDO Feedback 07 What kind of FEEDBACK LOOP IS THIS 1 Positive 2 Negative Snow and O Pianetary albedo ALSO a POSITIVE FEEDBACK LOOP that amplifies the effect Ptanetary albedo ALBEDO REVIEW Snow and ice cover If a surface s albedo is HIGH absorption by the surface is LOW COOLER surface If a surface s albedo is LOW absorption by the surface is HIGH gt HOTTER surface Type of Surface Albedo Sand 020 030 Grass 020 025 Forest 005 010 Water overhead Sun 003 005 Water Sun near horizon 050 080 Fresh snow 080 085 Thick cloud 070 080 PLANET EARTH 030 Planetary albedo Snow and ice cover P anetary albedo p73 Snow and ice cover P anetary albedo p73 Type of Surface Albedo Sand 020 030 Grass 020 025 Forest 005 010 Water overhead Sun 003 005 Water Sun near horizon 050 080 Fresh snow 080 085 Thick cloud 070 080 PLANET EARTH 030 CLOUDS 044 high thin 090 low thick temperature HOW DAISY COVERAGE AFFECTS 1 TEMPERATURE 32305 6 Daisy coverage Daisy coverage gt a coiaeirsgge w 2323 temperature An increase in daisy coverage 9 a decrease in surface temperature WHY because more sunlight is reflected back albedo increases 9 less sunlight is absorbed 9 Daisy coverage Daisyworld albedo cooler temps Average surface temperature Average surface temperature Daisy coverage p74 A 3 A sngsgs 203er 5333 4C cogzlifa e temperature 1 temperature Coupling is positive Coupling is negative t Optimum A t TEMPERATURE S emp S emp I creases Increases AFFECTS DAISY daisy coverage daisy coverage COVERAGE i creases decreases Daisy coverage Daisy coverage Minimum temper ture Maximum Average surface temperature gt te m pe ratu re Average surface temperamre PUTTING THE TWO GRAPHS TOGETHER Daisy coverage Daisy coverage Dam COAeLsae flipped axes temperature VASLSaS EDHSCS ELUDSLEHHLG gt Daisy coverage Daisy coverage gt Optirnum Maximum Average surface temperature gt Minimum temperature p74 P1 and P2 are EQUILIBRIUM STATES a state in which a system is in equilibrium that is the state in which the system will remain UNLESS something disturbs it An equilibrium state can be stable or unstable equilibrium statequot Stable equilibrium Stable equilibrium state state Daisy coverage Average Dais surface A I 0 rye Stable temperature 0 V9 39 su ace nsta Ie temperature 3 Coverage Averaoe surface temperature Unstable equianum stale Smhle equmbmrm state P1 amp P2 are each EQUILIBRIUM states but one is in a more precarious state unstable than the other p74 RECAP SUMMARY The presence of FEEDBACK LOOPS leads to the establishment of EQUILIBRIUM STATES Negative feedback loops establish STABLE equilibrium states that are resistant to a range of perturbations the system responds to modest perturbations by returning to the stable equilibrium state 0 Positive feedback loops establish UNSTABLE equilibrium states A system that is poised in such a state will remain there indefinitely However the slightest disturbance carries the system to a new state The last part of Chapter 2 illustrates that FEEDBACK FACTORS that are negative provide a buffer from FORCINGS they allow the daisies to survive LONGER after a climate change eg an increase in solar luminosity than they could have survived if NO feedback processes were in operation We will learn that this is EXACTLY what is happening on EARTH under many circumstances What we are worried about are the circumstances when feedback factors that are POSITIVE under a climatic FORCING ms mm mummm wscxinuus surrmras swarms smcwas 39pmmcs s Ecnnnmy Science 5 Hasmh Arcs s Culhur a Sumac s CDrnmun PBS NOW Earth Day April 22 2005 Time to Finish 39 the TREE RING PROJECT OR Develop your own FEEDBACK LOOP for a GROUP BONUS PT For 1 GROUP BONUS POINT we didn t have time for this in class But may try it again later Take a piece of paper amp write your name on it and number it 1 thru 4 Then do the following 1 sketch a feedback loop diagram positive or negative as complicated as you like 2 state what kind of loop it is or and HOW your know 3 NOW come up with a or feedback in your everyday life and make a diagram for it
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