Hans Plets

1
General Meteorology

• Hans Plets
• 28.09.2007

2
Todays programme

• Personal Introduction
• Aim of this course
• Scheme of the course
• References
• Subject(s) of todays lecture
• Historical note
• Generalities about the earths atmosphere

3
Personal Introduction Hans Plets

• M.Sc in Physics (1991)?
• PhD in Astronomy (1997)?
• Postdoc at the RMI (1997-2000)?
• Ozone layer
• UV
• Meteorological Training Officer at Belgocontrol
  (2000-2004)?
• Manager of the Meteorological Department of
  Belgocontrol (since 2004)?

4
Personal Introduction

• Belgocontrol
• Autonomous public company
• Core business Air Traffic Control in Belgium (
  Luxemburg)?
• To ensure Air Traffic Safety meteorological
  information provision (Meteorological
  Department)?
• Met services Steenokkerzeel, Antwerp, Charleroi,
  Liège, Ostend, Saint-Hubert and Spa
• Meteorology in Belgium
• Royal Meteorological Institute meteorological
  information for the public
• MeteoWing meteorological information for
  military aviation
• Belgocontrol meteorological information for
  civil aviation
• Private companies MeteoServices,

5
Aim of this course

• Familiarize you with the basic meteorological
  concepts and phenomena
• Provide a basic understanding of the processes
  that occur in the atmosphere
• Practical sessions
• Give you a flavour of how the job of a weather
  forecaster looks like (Teacher Raf Windmolders)?

6
(Idealized) Scheme of this course

• 28.09
• Lecture 1
• Introduction
• Ch 1. The Earth and its Atmosphere
• 05.10
• Lecture 2 1000 - 1230
• Ch 1. The Earth and its Atmosphere (sequel)?
• Lecture 3
• Ch 2. Energy Warming the Earth and the
  Atmosphere
• 12.10
• Lecture 4
• Ch 3. Seasonal and Daily Temperatures
• Lecture 5
• Ch 4. Atmospheric Moisture

7
(Idealized) Scheme of this course

• 19.10
• Lecture 6
• Ch 5. Condensation Dew, Fog, and Clouds
• Lecture 7
• Ch 6. Stability and Cloud Development.
• 26.10
• Lecture 8
• Ch 7. Precipitation
• Lecture 9
• Ch 8. The Atmosphere in Motion Air Pressure and
  Winds
• 09.11
• Lecture 10
• Ch 9. Wind Small-Scale and Local Systems
• 16.11
• Lecture 11
• Ch 10. Wind Global Systems

8
Scheme of this course

• 23.11
• Lecture 12
• Ch 11. Air Masses and Fronts
• Ch 12. Middle-Latitude Cyclones
• 30.11
• Practical session 1 Surface weather map analysis
• Practical session 2 Wind (direction speed)
  versus pressure patterns Coriolis
  acceleration, gradient wind
• 07.12
• Practical session 3 Introduction to upper air
  meteorology
• Practical session 4 Air masses fronts
  satellite images
• 14.12
• Practical session 5 Upper versus surface charts
• Practical session 6 Thermodynamic diagrams
• 21.12

9
References

• Most important reference
• Meteorology Today, Ahrens, 8th ed., 2006
• Other references
• Meteorology The Atmosphere and Science of
  Weather, Moran, Morgan and Pauley, 1996
• Atmospheric Science, Wallace and Hobbs, 2nd ed.,
  2006
• Atmospheric Thermodynamics, Bohren and Albrecht,
  1998
• Fundamentals of Atmospheric Science, Salby,
  Pielke and Dmowska, 1996
• Fondamentaux de Météorologie, Malardel, 2005
• Calculating the Weather, Nebeker, 1995

10
Today

• Subject(s) of todays lecture
• Introduction Historical note
• Generalities about the Earths atmosphere

11
Introduction Historical note

• Aristotles Meteorology no distinction between
  meteorites and precipitation (astronomy
  meteorology)?
• Meteorology is a combination of 3 different
  traditions
• Dynamic meteorology
• Climatology / Statistical approach
• Weather forecasting
• that remained rather autonomous within the field
  of Meteorology until the 1950s

12
Historical note
Climatology statistics empirical activity
collect observational data to derive information
from almost neglected physics descriptive
science the average weather Dynamic
Meteorology physics theoretical activity
explain/derive atmospheric phenomena from
general principles almost neglected
observations
13
Historical note
Weather Forecast practical activity
synoptic charts (via telegraphy) of pressure,
temperature, humidity, precipitation, wind,
derive rules of thumb from patterns (Buys-Ballot
Law, prevailing flow, motion around H and L,
correlation precipitation L / dryness H,
)? almost neglected theory used only limited
amount of data labelled unscientific by the
two other traditions on a daily base since ca.
1870
14
Historical note
Unification in 1950s thanks to availability of
electronic computers the 3 traditions used
similar models Big transformations in
meteorology 1) 1600 1700 quantitative
instead of qualitative description of
temperature, pressure, humidity, precipitation,
wind (direction and force)? - first
anemometer Alberti 1450 / Robertson 1846 -
first thermometer Galileo, 1593 - first
barometer Torricelli, 1643 - first rain
gauge Wren, 1662 - first hygrometer Folly,
1664
15
Historical note
2) 1850 1900 construction weather maps thanks
to telegraphy ? establishment of national
weather services, international cooperation 3)
1950 first computers So, technologically
driven 1) Instrumentation 2)
Communication 3) Calculation
16
Historical note
Richardson imagined a weather prediction factory
with 64000 people effectuating calculations
simultaneously, guided by a kind of conducter (in
the middle). This would enable weather
predictions for all over the globe. The great
number of people is needed to finish the
predictions before their validation time has
passed. This dream was never put into
practice. Richardson performed a 6hr forecast of
surface pressure on his own. It took him 6 weeks.
His result was 146 hPa. The correct result was
less than 1 hPa
Lewis Fry Richardson (1881-1953)?
1922
17
Historical note
John von Neumann (1903-1957)?
Jule Charney (1917-1981)?

• First successful Numerical Weather Prediction
  April 1950, using the ENIAC computer

• First operational weather predictions May
  1955, using an IBM 701 computer (US Air Force,
  Navy and Weather Bureau)?

18
Electronic Numerical Integrator And Calculator
(ENIAC)?
19
Historical note

• Optimism meteorology seems fully deterministic
• Obtain particular initial 3d-atmospheric state
  (wind, temperature, humidity, ) and boundary
  forcings (e.g. solar radiation)
• Solve the equations
• Meteorology as a problem to be solved once for
  all
• But
• Model (i.e. set of equations) is incomplete
  description of governing physics
• physical processes on small scales are not
  captured
• ? see Course Physical Meteorology
• Chaos theory time evolution of nonlinear,
  deterministic dynamical system highly depends on
  initial conditions, which are not perfectly well
  known in the case of the atmosphere

20
Historical note Meteorology nowadays

• Meteorology a branch of science dealing with
  the earths atmosphere and the physical
  processes occurring in it
• Atmosphere a spheroidal gaseous envelope
  surrounding a heavenly body

21
Historical note Meteorology nowadays

• Physical Meteorology
• Atmospheric structure composition
• Transfer of electromagnetic radiation and
  acoustic waves through the atmosphere
• Physical processes involved in the formation of
  clouds and precipitation
• Atmospheric electricity
• Aeronomy
• Synoptic Meteorology
• Description, analysis and forecasting of
  large-scale atmospheric motions
• Dynamic Meteorology
• Analytical approaches to atmospheric motions,
  based on fluid dynamics

22
Historical note Meteorology nowadays

• Bad mathematicians become physicists, and bad
  physicists become meteorologists - Aleksandr
  Friedman (1888-1925)

23
The Earths Atmosphere

• Main ingredients of meteorology
• Presence of an atmosphere
• fluid interface between Earth and Sun,
  influencing the energy distribution
• protects against harmful UV radiation
• supplies water, necessary for life forms
• contains gases for respiration and photosynthesis
• is for us what oceans is for fish we are
  confined to an ocean of air
• Earths gravity
• holds atmosphere together
• limits vertical motions by squeezing atmosphere
• invokes density decrease with height in the
  atmosphere
• Solar radiation
• Earths diurnal rotation (invoking ao. Coriolis
  force)?
• Earths yearly orbit around the Sun

24
The Earths Atmosphere Evolution

• 4.6 billion yrs ago
• Astronomers tell us Solar system originated from
  cloud of dust and gases within Milky Way
• Further accretion of cosmic dust meteorite
  bombardment
• ? Gravitational field strong enough for primeval
  atmosphere
• Probably first atmosphere with H and He (75
  25 100 of Universe)?
• Earth has temperature ? kinetic energy (mv²)?
• H and He light elements
• ? H and He relatively high v
• ? mean thermal speed relatively high

25
The Earths Atmosphere Evolution

• Gravity determines escape velocity
• If mean thermal speed gt escape velocity, then
  escape
• Earth too warm and/or mass too small to keep
  first atmosphere
• First atmosphere of H and He escaped into space
• Earth became planet without atmosphere
• Note in fact, all elements would have had
  mean thermal speed gt escape velocity