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Meteorology
Chapter 1
Introduction to the Atmosphere
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Meteorology \ Dr. Mazin sherzad
 Meteorology
(Introduction to the Atmosphere)
The atmosphere (history)
Observing the atmosphere
Weather, Climate and more definitions,
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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
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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Meteorology \ Dr. Mazin sherzad
Water 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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Meteorology \ Dr. Mazin sherzad
Clouds in the Atmosphere
•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%
cause
Factor
reason
principle
This can happen if one or both of the following occurs:
1) The air is cooled, reducing the saturation vapor pressure
2) Water vapor is added to the air
Rising air expands, expanding air cools, so rising air can cause clouds
Most clouds occur in the troposphere
There are exceptions:
Noctilucent clouds (NLCs) occur in the
mesosphere
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Meteorology \ Dr. Mazin sherzad
Polar stratospheric clouds (PSCs)
occur in the stratosphere
Precipitation
precipitation (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.
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Meteorology \ Dr. Mazin sherzad
snow
rain
hail
sleet
Annual rainfall mm, cm and m
daily 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.
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Atmosphere of Earth
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Meteorology \ Dr. Mazin sherzad
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Meteorology \ Dr. Mazin sherzad
Chapter 1
SUMMARY
Atmosphere Protocols
– Pressure
Cloud
– Wind Speed and
Aerosols
Direction
Water Vapor
• Surface Temperature
Relative Humidity
Precipitation (type and
amount
• Digital Max/Min/Current
Air and Soil Temperature
•
•
•
•
•
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Meteorology \ Dr. Mazin sherzad