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Dynamical Meteorology (Atmospheric Dynamics)

Lecturer: Aarnout van Delden Assistant: Michiel Baatsen (weather discussions) Office: BBG, room 615 a.j.vandelden@uu.nl http://www.staff.science.uu.nl/~delde102/

2016-2017

Dynamical Meteorology (Atmospheric Dynamics)

Lecturer: Aarnout van Delden Assistant: Michiel Baatsen (weather discussions) Office: BBG, room 615 a.j.vandelden@uu.nl http://www.staff.science.uu.nl/~delde102/

Lecture 1 – 2016-2017

Introduction Grading Lecture notes and literature Forcing and response Basic equations Weather forecast

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Grade Dynamical Meteorology Grade determined by

Exams (2x) on 11/11/2016 (30%) and (1/2/2017) (30%) (minimum average grade for 2 exams together should be 4/10) Project 1 (Problem 1.6) (written report1) (12%) (deadline: Friday 28 Sep 2016) Project 2 (Problem 1.24) (oral2) (16%) (hand in hypothesis on/before 2 November 2015) Problem 3.2 (12%) (second period) Participation in weather forecasting competition 1<1000 words; problem 1.6 will be introduced on Friday 11/9 2 15 minutes in December 2015 or January 2016

Projects 1, and 2 can be performed in couples

Make a weather forecast for next Sunday (Tmax, Tmin Rain and sunshine)

ΚΝΜΙ:Thursday, 8/9

Studyweathermaps

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Weerplaza:Thursday, 8/9

Make a weather forecast for next Sunday (Tmax, Tmin Rain and sunshine)

Studyweathermaps

Categorical forecast

Statement that can either be true (1 point) or false (0 points)

A categorical temperature (maximum/minimum) forecast states that the temperature will either be “normal”, “above normal” or “below normal”.

The normal temperature is deduced from observations over the past 30 years for the particular day of the forecast.

See problem 0.2 on page 12 of the lecture notes

More about this on Wednesday 14 Sep.

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Lecture notes

Download from: http://www.staff.science.uu.nl/~delde102/AtmosphericDynamics.htm

Lecture notes For sale at A-Eskwadraat (2nd floor of BBG; as pdf on blackboard)

LectureNotes,chapter1

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LectureNotes,chapter1

Lecture notes include a list of contents, an abstract, a reference list, but not an index…

A good learning method is to make your own index

Schedule 2015 Lectures First period: Friday 1100-1245 in weeks 36-44, except Friday week 43. Second period Friday 1100-1245 in weeks 46-50, 2-4

Practical (exercise) sessions First period Wednesday 1315-1630 in weeks 37-44. Second period Wednesday 1315-1630 in weeks 46-50, 2-4

Exams First period week 45 (Friday, November 11, 2016) (retake: December 2016) Second period week 5 (Wednesday, February 1, 2017) (retake: March 2017)

No lectures or practical sessions on October 28

Excursion KNMI Not yet set

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Prior knowledge I assume that the student is familiar with the thermodynamic concepts of temperature and pressure of a fluid or gas, and with the conservation laws governing the fluid in a rotating frame of reference.

Give a physical interpretation of the pressure in a fluid

Prior knowledge

The first part of the course consists of sections 1.1-1.12 and 1.14-1.40. If you have passed the bachelors course Geophysical Fluid Dynamics, you will be familiar with much of the subject matter of sections 1.1-1.8, except maybe with the complications associated with the fact that the atmosphere is a compressible fluid.

I assume that the student is familiar with the thermodynamic concepts of temperature and pressure of a fluid or gas, and with the conservation laws governing the fluid in a rotating frame of reference.

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Book

Holton, J.R., 2004: An Introduction to Dynamic Meteorology, fourth edition. Academic Press, 535pp. The first (1972), second (1979) and third (1992) edition are also very useful.

Jim Holton died suddenly (while running) in 2004.

A fifth edition of Holton’s book has appeared in 2012 with Gregory Hakim as co-author.

Central Question

John Dutton has phrased it in the following way.

“The basic problems of atmospheric dynamics revolve around the question of why the observed responses are those that are chosen”

The atmosphere responds to the inhomogeneous distribution of insolation by adjusting to some kind of balance of forces.

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Insolation [W m-2] La

titud

e[°N

]

>500 W m-2

Radiative energy fluxes and water cycle (2000-2004)

Figure 2.25

Global, annual mean energy fluxes in W m-2

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Back to the central Question

John Dutton has phrased it in the following way.

“The basic problems of atmospheric dynamics revolve around the question of why the observed responses are those that are chosen”

The atmosphere responds to the inhomogeneous distribution of insolation by adjusting to some kind of balance of forces.

zonal mean heating

Heating due to absorption of Solar radiation, absorption and emission of long-wave radiation, latent heat release

heating cooling cooling

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zonal mean temperature

Cold: why?

zonal mean heating

Heating due to absorption of Solar radiation, absorption and emission of long-wave radiation, latent heat release

heating

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zonal mean heating

Heating due to absorption of Solar radiation, absorption and emission of long-wave radiation, latent heat release

heating

Total precipitation

Intertropical convergence zone (ITCZ) and “stormtracks”

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Total precipitation

Intertropical convergence zone (ITCZ) and “stormtracks”

zonal mean zonal wind, u

“The basic problems of atmospheric dynamics revolve around the question of why the observed responses are those that are chosen”

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zonal mean zonal wind, u

What features do you observe???

zonal mean zonal wind, u

Subtropical jet; polar night stratospheric jet; Trade winds; What else?

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zonal mean zonal wind, u

Why does the atmosphere respond to heating in this way?

Polar vortex at 250 hPa

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What do we want to know about the atmosphere?

Density, ρ (mass) Speed, Pressure, p Temperature, T

Four unknowns

€

! v

What do you know about fluid dynamics?

The equations expressing conservation of momentum, mass and energy

The equation of state

Closed system of four equations with four unknowns:

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The coordinate system

The equations*

€

d! v dt

= −α! ∇ p − g ˆ k − 2

! Ω ×! v + Fr

€

dρdt

= −ρ! ∇ ⋅! v

€

Jdt = cpdT −αdp

€

p = knT

momentum

mass

energy

state

*see geophysical fluid dynamics and sections 1.2, 1.3 and 1.4 of lecture notes

Pressure gradient (1.3) Gravity (1.3) Coriolis (1.7) Friction (1.8)

€

! v ,ρ,T , p

€

α ≡1ρ

eq. 1.6

eq. 1.22

Unknowns: eq. 10a

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Next lecture (14/9)

Reduce these 4 equations to system of 3 equations in terms of:

Potential temperature, θ Exner function, Π

Wind speed

(section 1.4)

Assignments Study sections 1.1-1.4

Next lecture is on Wednesday 14/9 (13:15- ) sections 1.4, 1.5, 1.6 and introduction to problem 1.6

A first introduction to programming in Python

Friday 16/9 (Tutorial): Problems 1.1, 1.2, 1.3

Reading datafiles and plotting in Python