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Lecture 12

Lecture 12 - Storms.docx


Department
Earth Sciences
Course Code
EARTHSC 2GG3
Professor
Sergei Basik
Lecture
12

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Lecture 12: Storms Thunder, Lightning, Hail, Tornadoes and Dust
Weather Climate
EXAM QUESTION! What is the difference between weather and climate?****
Weather refers to the day-to-day changes in atmospheric conditions: temperature, precipitation
Climate is the long-term statistical average of weather conditions; assessed using at least 30-years of
data
Also includes long-term precipitation pattern
You can get same weather in 2 different climates
Adiabatic Cooling
Adiabatic cooling occurs when rising air cools as it expands without change in heat content
For dry air the cooling rate is 100C for every 1000m
Amount of heat stays
Adiabatic Lapse Rates
The saturated adiabatic lapse rate is less than the dry adiabatic lapse rate due to the release of
latent heat during condensation
Different if you have moisture in air and when you don’t
Convection
Heating of the Earth’s surface leads to rapidly rising parcels of air (convection) with subsequent
condensation and cloud formation
Winds and Pressure Gradients
High pressure system prevents warm air from rising clear skies
Low pressure system warm air rises cloudy
icelanding low pressure; Siberian high pressure; Bermuda high pressure; Pacific High pressure
high pressure equator
July high pressure moves south
Jetstreams
Generalized pattern of global circulation
with the typical jet stream locations shown
at 60deg and 30deg
Polar Cell North Pole
Storms occur between two different
temperature currents cells
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