Climatology lecture 1 what is climate
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Climatology Lecture 1: What is climate?. What should be learned in climatology?. 氣候學研究. Nature phenomena Observations: qualitative & quantitative descriptions Interpretation: (a) data diagnosis

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ClimatologyLecture 1: What is climate?

What should be learned in climatology?

  • Nature phenomena

  • Observations: qualitative & quantitative descriptions

  • Interpretation: (a) data diagnosis

    (b) theoretical/analytical study (c) experiment & numerical modeling

    Aspects: Formation, structure, evolution, interaction, and feedback

  • Application: forecast-error-modification

What the weather might be up to tomorrow?

Is the coming rainy season normal? Ancient civilizations appealed to the gods of the sky


Egyptians looked to Ra, the sun god,

Greeks sought out the all-powerful Zeus, and in

Ancient Nordic people, there was Thor, the god of thunder and lightning.

Aztecs use human sacrifice to satisfy the rain god, Tlaloc(He who makes things sprout).

Native American and Australian aborigines performed rain dances.

Those who were able to predict the weather/climate and seemed to influence its production were held in highest esteem. modern wizards


This is much better


Climatology is the study of atmosphere and its phenomena (Meteorology and Climate). It is a natural science due to the use of scientific instruments to make observations.

Aristotle340 BCMeteorologica


TheophrastusAristotles student, 287 BCBook of Signs (served as the definitive weather book for 2,000 years!)

Climate, a tract or region of the earth (clime in many poems)

in ancient Greece

klima in German & Norwegian

ora in Latin

localitin Italian


It advanced little after ancient Greece until the Renaissance













(Gustav Coriolis 19)



(The Bergen School)

1920:(polar front theory)(Bjerknes, Solberg, Bergeron)

Vilhelm F. K. Bjerknes(1862-1951) Jacob A.B. Bjerknes(1897-1975)


  • Pioneers in modern meteorology and climate research

  • Born on the 14th March, 1862 in Oslo (Christiania), Vilhelm Frimann Koren Bjerknes was destined for a career in science. He obtained a Masters degree in mathematics and physics in Kristiania 1888 and continued his studies in Paris and Bonn, where his work together with HeinrichHertz on electrical resonance resulted in a doctoral thesis in 1892.

  • While he was professor at the University of Stockholm (1895-1906), Vilhelm Bjerknes worked out a synthesis of hydrodynamics and thermodynamics, which was applicable to large-scale circulation in the atmosphere and the oceans. Based on his theorems, he published a programatic paper in 1904 on The problem of weather forecasting as a problem in mechanics and physics (Meteorologische Zeitschrift, Wien 21:1-7) where he postulated the procedure now know as numerical weather forecasting. Once at the Geophysical Institute in Bergen (1917-1926), he laid the foundations of the Bergen School of Meteorology. Bjerknes established a network of weather observations in Norway that collected data that would be of great importance in their later work. Together with his son Jacob, also an acknowledged meteorologist, he put forward the acclaimed polar front theory. In analogy with WWI battlefronts, the meteorological fronts form the boundaries between cold and warm air masses and their theories and models suggested that weather activity is concentrated in these relatively narrow zones, where mid-latitude cyclones were proposed to form, live, and decay. Today, practically all weather forecasting is based on Bjerknes principles described in his paper of 1904 and made possible thanks to the enormous computer capabilities of today. The work by Bjerknes marked a turning point in atmospheric science and remains remarkably unaltered to this day.

  • Further, Vilhelm and Jacob Bjerknes conducted several studies of the ocean circulation, air-sea exchange, and climate variability that laid the basis for modern research on climate change and the role of the ocean in the climate system. Jacob Bjerknes carried out pioneer studies on the North Atlantic Oscillation (NAO), by describing its major features and how it influences the currents and temperature conditions in the North Atlantic. Nowadays the vision provided by the Bjerknes family has been taken further by simulating climate variability in models that couple the atmosphere, land, and oceans, in an attempt to estimate the response of the climate system to driving forces.

  • The Centre is named is thus named as a tribute to their efforts.

  • (BCCR: Bjerknes Center for Climate Research, Norway)


(The Chicago School-Dynamical meteorology era)

1940(Rossby waves:)WMO

1950von NeumannW. Nielsen J. Charney(NWP)

1960TIROS-1Advanced TIROS (NOAA series) GOES and GMS(especially )




Image of a cyclone from TIROS1


  • 20~30, ,(NAO),(NPO),(SO); Walker (1932)

  • 30, -, Rossby (1939)

  • 40~50, , Namias (1953)

  • 60, , Bjerknes (1969)

  • 70, (doubling CO2), Manabe (1975)

  • 80, , Miyakoda (1986)

  • 80~90, ENSO, Cane and Zebiak (1986)

  • 80~90, ENSO, Suarez (1988), Battisti (1989)

  • 90, , Brocker , Delworth (1993)

  • 90, , Madden-Julian Oscillation(Madden 1994), Ming Ji (1994)

Carl-Gustav Rossby: Long waves in the westerly

Early days of NWP

Jule Charneys influence on modern Meteorology/long waves vs polar front (1982, BAMS)

Journal of the Atmospheric Sciences: Vol. 35, No. 3, pp. 414432.The Life Cycles of Some Nonlinear Baroclinic WavesAdrian J. Simmons and Brian J. Hoskins

Chaos Theory

  • Predictability problem


  • 20~30, ,(NAO),(NPO),(SO); Walker (1932)

  • 30, -, Rossby (1939)

  • 40~50, , Namias (1953)

  • 60, , Bjerknes (1969)

  • 70, (doubling CO2), Manabe (1975)

  • 80, , Miyakoda (1986)

  • 80~90, ENSO, Cane and Zebiak (1986)

  • 80~90, ENSO, Suarez (1988), Battisti (1989)

  • 90, , Brocker , Delworth (1993)

  • 90, , Madden-Julian Oscillation(Madden 1994), Ming Ji (1994)


Walker circulation-an equatorial belt circulation

The term Walker circulation was first defined by Bjerknes (1969) to describe an exchange of air in the zonal plane for the equatorial belt from South America to the western Pacific. Bjerknes considered this circulation to be part of the global Southern Oscillation phenomenon defined earlier in the statistical sense by Sir Gilbert Walker (1923, 1924, 1928). Bjerknes also postulated that the gradient of ocean surface temperature along the equator was the cause of the Walker circulation. Newell et al. (1974) later expanded this concept by considering circulations in zonal planes circumscribing the entire globe at any tropical latitude.

Chervin and Druyan 1984 MWR

Sea surface temperature anomaly map

Walkers southern oscillation (Bjerknes 1969)

  • Journal of the Atmospheric Sciences: Vol. 32, No. 1, pp. 315.

  • The Effects of Doubling the CO2 Concentration on the climate of a General Circulation Model

  • Syukuro Manabe and Richard T. WetheraldGeophysical Fluid Dynamics Laboratory/NOAA, Princeton University, Princeton, N.J. 08540

  • (Manuscript received 6 June 1974, in final form 8 August 1974)


    An attempt is made to estimate the temperature changes resulting from doubling the present CO2 concentration by the use of a simplified three-dimensional general circulation model. This model contains the following simplications: a limited computational domain, an idealized topography, no heat transport by ocean currents, and fixed cloudiness. Despite these limitations, the results from this computation yield some indication of how the increase of CO2 concentration may affect the distribution of temperature in the atmosphere. It is shown that the CO2 increase raises the temperature of the model troposphere, whereas it lowers that of the model stratosphere. The tropospheric warming is somewhat larger than that expected from a radiative-convective equilibrium model. In particular, the increase of surface temperature in higher latitudes is magnified due to the recession of the snow boundary and the thermal stability of the lower troposphere which limits convective beating to the lowest layer.It is also shown that the doubling of carbon dioxide significantly increases the intensity of the hydrologic cycle of the model.

  • Monthly Weather Review: Vol. 114, No. 12, pp. 23632401.

  • One-Month Forecast Experimentswithout Anomaly Boundary Forcings

  • K. Miyakoda, J. Sirutis, and J. PloshayGeophysical Fluid Dynamics Laboratory/N0AA, Princeton University, Princeton, NJ 08542

  • (Manuscript received 17 August 1985, in final form 19 May 1986)


    A series of one-month forecasts were carried out for eight January cases, using a particular prediction model and prescribing climatological sea-surface temperature as the boundary condition. Each forecast is a stochastic prediction that consists of three individual integrations. These forecasts start with observed initial conditions derived from datasets of three meteorological centers. The forecast skill was assessed with respect to time means of variables based on the ensemble average of three forecasts. The time or space filter is essential to suppress unpredictable components of atmospheric variabilities and thereby to make an attempt at extending the limit of predictability. The circulation patterns of the three individual integrations tend to be similar to each other on the one-month time scale, implying that forecasts for the 10 day (or 20 day) means are not fully stochastic. The overall results indicate that the 10-day mean height prognoses resemble observations very well in the first ten days, and then start to lose similarity to real states, and yet there is some recognizable skill in the last ten days of the month. The main interests in this study are the feasibility of one-month forecasts, the adequacy of initial conditions produced by a particular data assimilation, and the growth of stochastic uncertainty. An outstanding problem turns out to be a considerable degree of systematic error included in the prediction model, which is now known to be climate drift. Forecast errors are largely due to the model's systematic bias. Thus, forecast skill scores are substantially raised if the final prognoses are adjusted for the model's known climatic drift.

Oscillation of the thermohaline circulation

  • Journal of Climate: Vol. 6, No. 11, pp. 19932011.

  • Interdecadal Variations of the Thermohaline Circulation in a Coupled Ocean-Atmosphere Model

  • T. Delworth, S. Manabe, and R.J. StoufferGeophysical Fluid Dynamics Laboratory/N0AA, Princeton University, Princeton, New Jersey

  • (Manuscript received 5 September 1992, in final form 26 February 1993)


    A fully coupled ocean-atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the North Atlantic Ocean with a time scale of approximately 50 years. The irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation (approximately 52N to 72N) combined with much smaller density anomalies of opposite sign in the broad, rising region.The spatial pattern of sea surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the North Atlantic. The anomalies of sea surface temperature induce model surface air temperature anomalies over the northern North Atlantic, Arctic, and northwestern Europe.

  • ,,

  • ,,


The contribution to each winter's total precipitation made from "heavy" precipitation days, indicated by red (below average) and blue (above average) bars. A black smoothing line to highlight decadal variations has been overlaid.

Source: IPCC TAR (2001) Summary for Policy Makers

Source: IPCC AR4 (2007) Summary for Policy Makers

What is climate (A.S. Monin)?

--(A statistical ensemble of states of the atmosphere-ocean-land system during a time period several decades long. )

: --


(red noise)Monin--

(multiple scale)WMO()30(1951-1980)IPCC1961-1990 (anomaly;)

Can climate change occur over short time period?

By definition, NO!

What is climatology?

Study the statistical properties of the atmospheric variables: means, variability, max, min., etc.

Weather or climate?

Did it rain yesterday at Taipei?

When does Bombay enter the rainy season?

Was last winter colder than normal?


  • Monin

  • =>Rising of Earth System Science

Subsystems in Earth Climate System

  • Atmosphere: Nitrogen (78.1% volume mixing ratio) and oxygen (20.9%), together with a number of trace gases (argon 0.93%, helium, ozone, and carbon dioxide 0.035%). It also contains clouds and aerosols.

  • Hydrosphere: Liquid surface and subterranean water (oceans, seas, rivers, fresh water lakes, underground water etc.)

  • Cryosphere: Snow,ice, and permafrost at and beneath the surface of the earth and ocean.

  • Lithosphere: The upper layer of the solid Earth, both continent and ocean, comprising all crustal rocks and the cold part of the uppermost mantle (volcanic activity is generally excluded).

  • Biosphere: ecosystems and living organisms in the atmosphere, on land or in the oceans, including derived dead organic matter, such as litter, soil organic matter and oceanic detritus.

Source: IPCC AR4 (2007) Scientific basis

()(Intrinsic unpredictability)

  • The laws of momentum conservation here lead to intrinsic nonlinearity (Navier-Stokes equations). Here u is the velocity of a parcel of air or fluid.


: Impossibility of knowing initial conditions with perfect precision

Hard wall adds nonlinear response

Slight differences

in initial x,v lead to

very different

trajectories still,

motion is bounded

But, trajectories are confined to ``attractors average behavior can be well defined !=> bounded system

Two dimensional Lorenz attractor for simple model of the weather

A butterfly !

External forcings

Internal forcings: reacts of interactions to a subsystem


End of Lecture 1

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