Meteo 3: Chapter 1Meteo 3: Chapter 1

Tools and basic terms we use to Tools and basic terms we use to describe the weatherdescribe the weather

Read Chapter 1Read Chapter 1

TerminologyTerminology Atmosphere:Atmosphere: The envelope of air surrounding the The envelope of air surrounding the

earthearth– Includes gases, clouds and particlesIncludes gases, clouds and particles– Relatively thinRelatively thin

Meteorology: Meteorology: The study of the physics, chemistry, The study of the physics, chemistry, and dynamics of the atmosphereand dynamics of the atmosphere

Weather:Weather: The state of the atmosphere The state of the atmosphere Climate: Climate: describes prevailing weather conditions describes prevailing weather conditions

in a location in terms of averages/extremes over in a location in terms of averages/extremes over long periodslong periods

Atmospheric GasesAtmospheric Gases

Permanent Gases-Permanent Gases- constant concentration constant concentration

1) Nitrogen- 78.08%1) Nitrogen- 78.08% 2) Oxygen- 20.95%2) Oxygen- 20.95% 3) Argon- 0.93%3) Argon- 0.93% 4) Neon- 0.0018% 4) Neon- 0.0018%

Variable Gases- Variable Gases- variable concentrationvariable concentration

1) Water Vapor- 0-4%1) Water Vapor- 0-4% 2) CO2) CO22- 0.038%- 0.038%

3) Methane- .00018%3) Methane- .00018% 4) N4) N22O- 0.00003%O- 0.00003%

Table 1.1 Grenci/NeseTable 1.1 Grenci/Nese

Toolbox Toolbox Need to know when, where, what and how much Need to know when, where, what and how much

we are referring to with respect to the weather! we are referring to with respect to the weather! Easier to communicate about the weather when Easier to communicate about the weather when

we have standards for thesewe have standards for these Where -> geography, topography, Where -> geography, topography,

latitude/longitude latitude/longitude What -> e.g. temperature, pressureWhat -> e.g. temperature, pressure When -> standardized time, timescalesWhen -> standardized time, timescales How much -> statistics, UNITSHow much -> statistics, UNITS

Political Map: Know Your States!Political Map: Know Your States!Show boundaries made and used by humans Show boundaries made and used by humans

PA TopographyPA Topography Physical Maps:Physical Maps: Show natural features Show natural features

– Important b/c earth’s surface influences flow of airImportant b/c earth’s surface influences flow of air

Latitude & LongitudeLatitude & Longitude Latitude lines run Latitude lines run

parallel with equatorparallel with equator Longitude lines run Longitude lines run

pole to polepole to pole

Earth divided by LatitudesEarth divided by Latitudes

TropicsTropics lie between 23.5ºN ( lie between 23.5ºN (Tropic of CancerTropic of Cancer) & ) & 23.5ºS (23.5ºS (Tropic of CapricornTropic of Capricorn))

From 23.5º-30º in each hemisphere = From 23.5º-30º in each hemisphere = subtropicssubtropics Polar regionsPolar regions lie poleward of 66.5º lie poleward of 66.5º Mid-latitudes Mid-latitudes located between polar regions and located between polar regions and

subtropicssubtropics

A Standardized Time ScaleA Standardized Time Scale

8:00 am here is not 8:00 am in Chicago, 8:00 am here is not 8:00 am in Chicago, Ulaanbaatar or OuagadougouUlaanbaatar or Ouagadougou

Zulu-Time (Z) or Coordinated Universal Time Zulu-Time (Z) or Coordinated Universal Time (UTC)(UTC) = time scale all weather observations are = time scale all weather observations are reported in…represents local time on Prime reported in…represents local time on Prime MeridianMeridian– Ranges from 0-24 hrsRanges from 0-24 hrs– Eastern Time Zone is 5 hrs behind UTC, 4 hours behind Eastern Time Zone is 5 hrs behind UTC, 4 hours behind

during Daylight Savings Timeduring Daylight Savings Time E.g. 12Z = 7:00am EST or 8:00 am EDTE.g. 12Z = 7:00am EST or 8:00 am EDT

The larger a weather phenomenon, the longer it The larger a weather phenomenon, the longer it lasts!lasts!

TemperatureTemperature TemperatureTemperature = measure of the avg. kinetic energy of a = measure of the avg. kinetic energy of a

substance’s moleculessubstance’s molecules– kinetic energy (KE)kinetic energy (KE) = energy associated with motion = energy associated with motion– High KEs correspond to higher temperatures High KEs correspond to higher temperatures – 3 Scales to Describe Temperature3 Scales to Describe Temperature– 1) Kelvin- 0 K corresponds to temperature at which 1) Kelvin- 0 K corresponds to temperature at which

molecular motion ceases, known as absolute zeromolecular motion ceases, known as absolute zero– 2) Celsius Scale- used to give temperatures in all 2) Celsius Scale- used to give temperatures in all

countries but US.…0ºC corresponds to ice’s melting pointcountries but US.…0ºC corresponds to ice’s melting point ºC = K - 273.15ºC = K - 273.15

– 3) 3) Fahrenheit= temperature scale used in US…32ºF 3) 3) Fahrenheit= temperature scale used in US…32ºF corresponds to ice’s melting pointcorresponds to ice’s melting point ºF = (1.8)ºC +32ºF = (1.8)ºC +32

UnitsUnits Scientists commonly use SI units => meter (m), Scientists commonly use SI units => meter (m),

second (s), kilogram (kg), and Kelvin (K) and second (s), kilogram (kg), and Kelvin (K) and scientific notation to represent numbersscientific notation to represent numbers

(e.g. 4.02 * 10(e.g. 4.02 * 1044)) All kinds of tutorials on the web on how to convert All kinds of tutorials on the web on how to convert

units using ‘dimensional analysis’ or ‘factor label’units using ‘dimensional analysis’ or ‘factor label’ For example:For example: http://www.ncsu.edu/felder-public/kenny/papers/units.htmlhttp://www.ncsu.edu/felder-public/kenny/papers/units.html

And And if you don’t learn howif you don’t learn how……

StatisticsStatistics

Average (Mean)- Average (Mean)- sum of all observed sum of all observed values divided by number of observationsvalues divided by number of observations

In meteorology, normals (averages) In meteorology, normals (averages) computed by averaging 30 years of datacomputed by averaging 30 years of data– Weather rarely conforms to “normals”Weather rarely conforms to “normals”

Range-Range- maximum and minimum values maximum and minimum values Probability of Precipitation (POP)-Probability of Precipitation (POP)- 70% 70%

chance of rain means a 7 in 10 chance that any chance of rain means a 7 in 10 chance that any point in the forecast area receives measurable rainpoint in the forecast area receives measurable rain

Weather ObservationsWeather Observations

In the U.S., surface weather observations taken In the U.S., surface weather observations taken automatically at ~1500 locations, mainly near airports…automatically at ~1500 locations, mainly near airports…coordinated by government (FAA & NWS)coordinated by government (FAA & NWS)

Weather conditions above the surface are measured using Weather conditions above the surface are measured using radiosondesradiosondes- weather-sensing instruments carried aloft by - weather-sensing instruments carried aloft by weather balloonsweather balloons– Upper-air obs. are made at fewer spots (~100 in North Upper-air obs. are made at fewer spots (~100 in North

America) and less frequently (2 times/day) than surface America) and less frequently (2 times/day) than surface obs.obs.

– Sparse upper-air network limits predictive capabilitiesSparse upper-air network limits predictive capabilities

Displaying Weather Data: The Station Displaying Weather Data: The Station ModelModel

CD from CD from Grenci/Nese has Grenci/Nese has cool interactive tool cool interactive tool to make and modify to make and modify station models, let’s station models, let’s take a looktake a look

So, what’s the temperature trend here?So, what’s the temperature trend here?

Eliminate the extraneous data…Eliminate the extraneous data…

How about contours?How about contours?

IsoplethingIsoplething IsoplethsIsopleths connect points of equal value on connect points of equal value on

a weather mapa weather map– Isotherms = lines of equal temperatureIsotherms = lines of equal temperature– Isobars = lines of equal pressureIsobars = lines of equal pressure– Isotachs = lines of equal wind speedIsotachs = lines of equal wind speed

Helps forecasters see patterns in data and Helps forecasters see patterns in data and estimate values at places where estimate values at places where observations are not takenobservations are not taken

How to ContourHow to Contour

Java applet from University of Wisconsin Java applet from University of Wisconsin http://cimss.ssec.wisc.edu/wxwise/contour/http://cimss.ssec.wisc.edu/wxwise/contour/

Isopleths that close in on themselves represent a Isopleths that close in on themselves represent a maximum or minimum of a quantitymaximum or minimum of a quantity

Usually drawn at equal intervalsUsually drawn at equal intervals Lines are neat/smooth, don’t cross or forkLines are neat/smooth, don’t cross or fork More direction given in Grenci/Nese, p. 18-21 and More direction given in Grenci/Nese, p. 18-21 and

in labin lab

GradientsGradients

Gradient- Gradient- A change in some quantity over a A change in some quantity over a distancedistance– Ex. Ski slopesEx. Ski slopes– The larger the change over a given distance, the larger The larger the change over a given distance, the larger

the gradientthe gradient– Large gradients indicated by tightly packed isoplethsLarge gradients indicated by tightly packed isopleths– Meteorologists focus on large gradients of temperature, Meteorologists focus on large gradients of temperature,

pressure, etc. because they indicate areas of changing pressure, etc. because they indicate areas of changing weatherweather