Structure of atmosphere Meteorological/Environmental parameters Meteorological phenomena

Scopes of studies Climatology and Meteorology are branches of similar areas of study.

Climatology is focused on averages of weather and climatic conditions over a long period of time.

Meteorology focuses more on current weather conditions such as humidity, air pressure, and temperatures and forecasting the short-term weather conditions to come.

http://en.wikipedia.org/wiki/Earth's_atmosphere

Ozone maximum

Refer to:

1.Layers of the Atmosphere (National Weather Service JetStream – Online School for Weather, www.srh.noaa.gov/srh/jetstream/atmos/layers.htm#ion)

2.E. Aguado and J.E. Burt, Chapter 1 of Understanding Weather and Climate

Troposphere 對流層

• The troposphere ranges form the earth surface to 8-16 km (mean 11 km) height.

• We are living in this region, even travelling in a plane.

• Almost all weather occurs in this region.

• Air concentration drops with height.

• Temperature drops with height from 17°C (62°F) to -51°C (-60°F), because air is mainly warmed by radiation from the surface.

• Decreasing temperature with height causes convection of air.

• The upper transition boundary is called the tropopause.

Stratosphere 同溫層 ; 平流層

• The stratosphere ranges from 20 – 50 km height.

• It holds 19% of the atmosphere's gases but very little water vapor.The temperature increases from -57 to -2oC with increasing height.

• The upper regions receives more intense UV radiation. More UV is absorbed by oxygen causing a higher temperature. Less UV radiation reaches the lower boundary, where a lower temperature is resulted.

• A balance between cooling effect with height and UV heating is reached near the bottom of this layer, resulting in a constant temp range.

• Ozone reaches the max. concentration.

• The increase of temperature with height results in a calm layer with slow gas movement.

• The upper boundary is called the stratopause.

Mesosphere

•The mesosphere extends from the stratopause to 85 km above the surface.

•It is believed that the absorption of solar radiation at the bottom provides most of the heat of this layer. Heat is dispersed upward by vertical air motion.

•On average, temperature decreases from -15°C to -120°C from bottom to top of the layer.

•The top boundary is called the mesopause.

•The gases in this layer are thick enough to slow down meteorites ( 流星 ) hurtling into the atmosphere, where they burn up, leaving fiery trails in the night sky.

Thermosphere

•The Thermosphere extends from the mesopause to 690 km above the earth.

•Higher energy ultraviolet and x-ray radiation from the sun are absorbed by gas molecules which concentrations are very low.

•Temperature of the ionized species could be as high as 2000°C.

•However, despite the high temperature, this layer is still very cold to our skin because of the extremely thin air.

Spectra of solar radiation and terrestrial radiationhttp://www.stvincent.ac.uk/Resources/Weather/Meteosat/System/imaging.html

Earth-atmosphere energy balance

Why is the sky blue (Scattering of light)? http://www.phys.ufl.edu/~avery/course/3400/atmosphere?N=A

Why are sunsets red (scattering of light)? http://www.weatherquestions.com/Why_are_sunsets_red.htm

Earth-atmosphere energy balance

Earth-Atmosphere energy balance http://www.srh.noaa.gov/srh/jetstream/atmos/energy_balance.htm

Wind chill effect

A stable temperature is reached.

http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/solarradiationalevel.html

Causing internal movements of fluid systems (water in ocean and air) to keep a steady state of the globe.

Circulation of ocean streams

Atmospheric circulation

“Greenhouse effect”: A greenhouse is designed to admit both long and short wavelength radiation, and is opaque to the re-irradiated long wavelength radiation. It also precludes heat loss due to convection. The latter effect does not exactly occurs in the atmosphere (not a true greenhouse effect). Moreover, if there is no greenhouse effect, the mean temp of the earth would be -18oC, and oscillate widely from day to night.

Earth surface temperature distribution

North America

South America

Africa

EuropeAsia

Australia

Antarctica

Ice point: 0°C or 32°F (in this case °C = °F – 32)

Catching a fever: 40°C or 104°F (°C = (°F-32)x a factor smaller than 1, i.e. 5/9)

°C = (°F-32) x 5/9°F = °Cx9/5 + 32

Description Temperature (oC)

Very Cold 嚴 寒 <= 7 oC

Cold 寒 冷 8 - 12 oC

Cool 清 涼 13 - 17 oC

Mild 和 暖 18 - 22 oC

Warm 溫 暖 23 - 27 oC

Hot 炎 熱 28 - 32 oC

Very Hot 酷 熱 >= 33 oC

Temperature

Measurements of temperature

Recording the volume change of mercury of alcohol. Disadvantage is not ready for auto-recording.

Alcohol thermometer

Range: 30C - 60C

Mercury thermometer

Measurement range ： 10C - 100C

• For automatic recording 電腦網絡傳送 )• For the convenience of data transfer (through internet/wireless technology,

recording in computer and server) • Remote sensing • More accurate

Radiosonde telemetry

Electronic thermometer is needed

Platinum thermometer

Pressure = weight of air / areaPressure = weight of air / area

in Pa = N/min Pa = N/m²²or or hPa = 100 PahPa = 100 Paor atm (atmospheric pressure)or atm (atmospheric pressure)or bar or bar

1 standard atmospheric pressure1 standard atmospheric pressure= = 1.013 x 101.013 x 1055 Pa Pa = 1013 hPa (hectopascal)= 1013 hPa (hectopascal)= 1 bar = 1000 mbar= 1 bar = 1000 mbar

Atmospheric pressure and Wind

BarometerBarometer (( 氣壓計氣壓計 ))

In Barometer, there is a In Barometer, there is a pressure sensor:pressure sensor:

Pressure changes Pressure changes electrical electrical

capacitancecapacitance

Height dependence of pressure Height dependence of pressure

Sea level pressure ~ P(0) = Sea level pressure ~ P(0) = 1000 mb (1 atm)1000 mb (1 atm)

Pressure drops with Pressure drops with heightheight ( (hh): ): P(h) = P(0) eP(h) = P(0) e-h/H-h/H

where H is a constant where H is a constant

http://gb.weather.gov.hk/education/package/pack01_severe_wx/severewx.html

Beaufort No.

Description Wind Speed(km / hr)

Effects Land

0 Calm < 2 Still, calm air, smoke will rise vertically.

1 Light Air 2 - Rising smoke drifts, wind vane is inactive.

2 Light Breeze -12 Leaves rustle, can feel wind on your face, wind vanes begin to move.

3 Gentle Breeze 13 - Leaves and small twigs move, light weight flags extend.

4 Moderate Breeze - 30 Small branches move, raises dust, leaves and paper.

5 Fresh Breeze 31 - 40 Small trees sway.

6 Strong Breeze 41 - Large tree branches move,  telephone wires begin to "whistle", umbrellas are difficult to keep under control.

7 Moderate Gale 62 - Large trees sway, becoming difficult to walk.

8 Gale 63 - Twigs and small branches are broken from trees, walking is difficult.

9 Strong Gale - 87 Slight damage occurs to buildings, shingles are blown off of roofs.

10 Storm 88 - Trees are broken or uprooted, building damage is considerable.

11 Violent Storm - 117 Extensive widespread damage.

12 Hurricane 118+ Extreme destruction, devastation.

http://www.marinewaypoints.com/marine/wind.shtml

Weather Map Wind Symbols (1 knot = 1.85 km / hr)

Composition of the atmosphere

Constituent percentage

Nitrogen 78.08

Oxygen 20.95

Argon 0.93

Ne, He, Kr, Xe,H2 Remainder

Permanent gases

Variable gases: Though the contents are rare, but is important to meteorological phenomena, and have great influence to comfort.

Constituent percentage

Water vapor 0.25

CO2 0.038

Ozone 0.01

wind vanewind vane (( 風向風向計計 ))

anemometeranemometer (( 風速計風速計 ))

wind cupwind cup(( 風杯風杯 ))

Measurement of wind speed and direction

• A turbine rotates freely at a speed directly proportional to the wind speed.

• The resulting signal is processed and displayed.

Turbo Meter

Description Relative Humidity ( % )

Very Dry 0 - 40 %

Dry 40 - 70 %

Humid 85 - 95 %

Very Humid 95 - 100 %

Relative Humidity

Relative humidity

Relative humidity = content of water vapor in air relative to the saturated value

evaporate compensecompenseVaporVapor(cloud,(cloud,

fog)fog)

WaterWater(of sea)(of sea)

waterwater（（ Rain, Rain, dewdew ））

Relative humidity in % = amount of vapor/maximum quantity

of water at that temperature

Average relative humidity in HK ~ 70-80%In winter : ~30-40% When red signal of rainstorm is in force:

RH ~ 100%

黃色暴雨警告信號In broad area of Hong Kong, a rainfall of 30

mm/h is recorded

紅色暴雨警告信號In broad area of Hong Kong, a rainfall of 50

mm/h is recorded

黑色暴雨警告信號In broad area of Hong Kong, a rainfall of 70

mm/h is recorded

Rain fall

Rain gauge : as simple as a cylindrical container + a ruler

Make your own rain gaugehttp://www.fi.edu/weather/todo/r-gauge.html

With two flip-flop buckets, each with a conducting contact for counting the time of switching cycles.

Rainfall (in mm/hr) = volume / area of the entrance / time of measurement