Predicting Future Weather and Climate. Warittha Panasawatwong Ali Ramadhan Meghana Ranganathan

Transcription

1 Predicting Future Weather and Climate Warittha Panasawatwong Ali Ramadhan Meghana Ranganathan

2 Overview Introduction to Prediction; Why is Weather Unpredictable? Delving into Chaos Theory Weather Versus Climate: What Makes Them Different Future Projections of Climate 2

3 What is prediction? Image: 3

4 What is prediction? Prediction: extrapolation of knowledge of a sample to an entire population Image: 4

5 What is prediction? Prediction: extrapolation of knowledge of a sample to an entire population Forecasting: extrapolation of knowledge of the current or the past to the future; prediction in time Image: 5

6 What is prediction? Prediction: extrapolation of knowledge of a sample to an entire population Forecasting: extrapolation of knowledge of the current or the past to the future; prediction in time We predict disease, stock markets, solar cycles, population dynamics...and weather and climate. Image: 6

7 How do we know if we re good at forecasting? Image: 7

8 How do we know if we re good at forecasting? Forecast Skill: Quality of a forecast compared to observations Image: 8

9 How do we know if we re good at forecasting? Forecast Skill: Quality of a forecast compared to observations Methods of calculating forecast skill: -Mean Squared Error Skill Score -Ranked Probability Skill Score -Logarithmic Skill Score Image: 9

10 How do we know if we re good at forecasting? Methods of calculating forecast skill: -Mean Squared Error Skill Score Image:

11 How do we know if we re good at forecasting? Image:

12 Why is weather so difficult to predict? Image: 12

13 A Bit of Math: Chaos Theory Images:

14 Properties of a Chaotic System Chaos describes a dynamical system that has certain properties. These properties make these systems uniquely hard to predict... 14

15 Properties of a Chaotic System Chaos describes a dynamical system that has certain properties. These properties make these systems uniquely hard to predict In the words of Edward Lorenz When the present determines the future, but the approximate present does not approximately determine the future Source: 15

16 Properties of a Chaotic System 1. Sensitivity to Initial Conditions Image: 16

17 Properties of a Chaotic System 1. Sensitivity to Initial Conditions 2. Topologically Mixing Image: 17

18 Properties of a Chaotic System 1. Sensitivity to Initial Conditions 2. Topologically Mixing 3. Dense Periodic Orbits Image: 18

19 Properties of a Chaotic System 1. Sensitivity to Initial Conditions 2. Topologically Mixing 3. Dense Periodic Orbits 4. Aperiodic Image: 19

20 Properties of a Chaotic System - Summarized As described by the Stanford Encyclopedia of Philosophy: A dynamical system f is chaotic if, on a set M, 1. f has sensitivity dependence (weak) on set M 2. f is topologically transitive on M 3. Periodic orbits form a dense set on M 4. (Aperiodic) When the present determines the future, but the approximate present does not approximately determine the future Source: 20

21 What Does This Have to Do With Weather? Chaos puts a limit on predictability... Images: 21

22 If you want to know more... February 2nd, 8:30AM-5:30PM, MIT Wong Auditorium, E

23 Climate Model Vs. Weather Model - Grid system - Physics and process - A point is related to the next points 23

24 Weather Model - Reliable observations -> checking if the model is correct - Less variable to be concerned - Shorter time scale: hourly - daily 24

25 Climate Model - ~ 50 years of reliable global data, thanks to satellite - More processes to think about: ocean circulation, sea ice, vegetation, anthropogenic greenhouse gas - longer timescale: monthly 25

26 Climate Model Evaluation 26

27 Climate Model Evaluation: Comparing between Models Model spread 27

28 Climate Model Evaluation: Comparing between Models - Set initial and boundary condition - Set scenarios for experiments 28

29 Climate Model Evaluation: Model Spin Up 29

30 Climate Model Evaluation: Model Spin Up Meteostat satellite observations of clouds (left) are compared to climate model output from ECMWF (right) 30

31 Climate Model Evaluation: Emergent Constraint Hall and Qu (2016) 31

32 Climate Model Evaluation: Emergent Constraint Bender, et al (2010) 32

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34 What s up with all this RCP stuff? IPCC AR5 34

35 IPCC AR5 35

36 IPCC AR5 36

37 IPCC AR5 37

38 IPCC AR5 38

39 IPCC AR5 39

40 IPCC AR5 40

41 IPCC AR5 41

42 IPCC AR5 42

43 IPCC AR5 43

44 IPCC AR5 44

45 EXTRA SLIDES WE RE NOT USING 45

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49 IPCC AR5 49

50 IPCC AR5 50

51 So...how good are weather and climate predictions? Image: 51

52 What About Climate? Images: pg 52