Www.soran.edu.iq 1. Meteorology Chapter 1 Introduction to the Atmosphere Meteorology \ Dr. Mazin sherzad

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Meteorology

Chapter 1Introduction to the Atmosphere

Meteorology \ Dr. Mazin sherzad

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Meteorology(Introduction to the Atmosphere)The atmosphere (history) Observing the atmosphere Weather, Climate and more definitions,


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Definitions

• Meteorology – (is the scientific study of the atmosphere)

The study of variable weather, the processes that cause weather and the interaction of the atmosphere with the Earth’s surface, ocean, and life

• Climatology – The study of climate, including past climate conditions and possible climate changes in the future


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Weather

• Weather is the condition of the atmosphere at a particular location and moment

• The condition of the atmosphere is expressed according to the following:– Temperature– Humidity (relative humidity, dew point)– Pressure– Wind Speed and Direction– Cloud Cover– Precipitation (type and amount)


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Climate

• Climate is the condition of the atmosphere over many years

• The same atmospheric variables are used for climate as weather

• Climate data use the following:– Averages (“normal high” = 30 year average high

temperatures for a given date and location)– Extremes (“record high” = highest temperature

ever recorded for a given date and location)


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The Earth’s Major Surface Features

• Our atmosphere receives energy from the Sun.• The surface of the Earth exchanges energy and water with the

atmosphere.• The distribution of land and water plays a major role in determining

climatic conditions and weather patterns.• 70% of the Earth’s surface is water (Arctic, Atlantic, Pacific, and Indian

Ocean).• More than 2/3 of Earth’s land is located in the Northern Hemisphere

(Seven continents are: Africa, Asia, Australia, Europe, North America, and South America).


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Atmospheric Variables

• We use a variety of variables to describe the atmosphere,

– For example:

• Temperature

• Pressure

• Mixing ratio

• Discussing the atmosphere requires an understanding of some important atmospheric variables


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Temperature

• Temperature is a measure of the average speed of the molecules, faster motion = higher temperature.

• Temperature is a fundamental quantity for understanding the weather, radiation, and chemistry of the atmosphere.

• Temperature scales:

• Fahrenheit (F): water freezes at 32°F and boils at 212°F

• Celsius (C): water freezes at 0°C and boils at 100°C, T(F) = (9/5) T(C) + 32

• Kelvin (K): water freezes at 273.15 K and boils at 373.15 K, T(K) = T(C) + 273.15


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Pressure• Atmospheric pressure can be thought of as the weight per unit area of the

column of atmosphere above a given height.

Pressure scales:

Millibars (mb): Sea level pressure is 1013.25 mb

Inches of Mercury (“Hg): Sea level pressure is 29.92 “Hg


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Water in the AtmosphereWater in the Atmosphere•Water exists in 3 states: solid (ice) – liquid – gas (water vapor)

•The saturation water vapor pressure (es) represents the maximum vapor pressure of water in air.

Vapor pressure is determined for equilibrium over liquid water or over ice

•es is a function of temperature alone, and decreases at colder temperatures.

•Relative humidity is the ratio of the water vapor content to the water vapor capacity:

RH = 100 x e / es (%)

•Dew point is the temperature to which the air would have to be cooled to achieve 100% relative humidity.


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Clouds in the Atmosphere

Most clouds occur in the troposphere

There are exceptions:

Noctilucent clouds (NLCs) occur in the mesosphere

Polar stratospheric clouds (PSCs) occur in the stratosphere

•Clouds are a collection of water drops and/or ice crystals•Clouds form when water vapor in the atmosphere condenses•Condensation only occurs on CN•Water vapor condenses when the relative humidity exceeds 100%

This can happen if one or both of the following occurs:1) The air is cooled, reducing the saturation vapor pressure2) Water vapor is added to the air

Rising air expands, expanding air cools, so rising air can cause clouds


cause Factor reason principle


Precipitationprecipitationprecipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena) is any product of the condensation of atmospheric water vapor that falls under gravity The main forms of precipitation include rain, snow, sleet and hail.

rainsnow

sleethail


Annual rainfall mm, cm and mdaily rainfall kg / m


The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year (these differences are extremely small). The seasons are the result of the tilt of the Earth's axis.The Earth's axis is tilted from perpendicular to the plane of the ecliptic by 23.45°. This tilting is what gives us the four seasons of the year - spring, summer, autumn (fall) and winter. Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year.Summer is warmer than winter (in each hemisphere) because the Sun's rays hit the Earth at a more direct angle during summer than during winter and also because the days are much longer than the nights during the summer. During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.


Atmosphere of Earth


www.soran.edu.iqMeteorology \ Dr. Mazin sherzad

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SUMMARY Atmosphere Protocols

• Cloud• Aerosols• Water Vapor• Relative Humidity• Precipitation (type and

amount• Digital Max/Min/Current

Air and Soil Temperature

– Pressure– Wind Speed and

Direction

• Surface Temperature


Chapter 1

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Www.soran.edu.iq 1. Meteorology Chapter 1 Introduction to the Atmosphere Meteorology \ Dr. Mazin sherzad