Chapter 5 notes: Global Temperatures
Chapter 5 notes: Global Temperatures Geog 1112
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Date Created: 02/20/16
Chapter 5: Global Temperature Notes Apparent Temperature = outdoor temperature as it is perceived by people Humidity = water vapor content of air Wind-Chill Factor = measures the enhanced rate at which heat is lost to the air 1. Wind Speed increases = heat loss from skin increases; wind-chill factor goes up Wind-Chill Temperature Index = uses wind speed and air temperature to figure out apparent temperature (made by the National Weather Service) 1. Goal of chart = evaluate the danger freezing temperatures and winter winds pose to people Lower Wind Chill = freezing hazard; frostbite; hypothermia (people lose heat faster than their bodies can make it) Temperature Concepts and Measurement Heat = form of energy; moves among particles in a system or substance by means of kinetic energy A hotter substance = has molecules that move with a greater energy More heat = more energy Temperature = not a form of energy; related to the amount of energy in a substance Temperature = measure of the average kinetic energy of individual molecules in matter; measure of heat Heat transfer = a change in temperature Temperature Scales Absolute Zero (0 absolute temperature) = the temperature where molecular and atomic motion in matter totally stop Absolute Zero in Celsius = -273 degrees Absolute Zero in Fahrenheit = -59.4 degrees Absolute Zero in Kelvin = 0 degrees Daniel G. Fahrenheit (German physicist) = the Fahrenheit scale is named for him Melting Point of ice in Fahrenheit = 32 degrees Ice = contains only one melting point Boiling Point of water in Fahrenheit = 212 degrees Water = contains many freezing points Anders Celsius (Swedish Astronomer) = made the Celsius scale Celsius Scale = used by most countries; USA uses Fahrenheit Melting Point of ice in Celsius = zero Boiling Temperature of water at sea level = 100 degree Lord Kelvin (British physicist) = proposed Kelvin scale Kelvin scale = science use this because it begins at absolute zero Melting Point for ice in Kelvin = 273 K Boiling Point for water in Kelvin = 373 K The size of 1 Kelvin unit = the same size as 1 Celsius degree Measuring Temperature Thermometer = measures temperature Mercury and Alcohol Thermometers = used to measure outdoor temperatures Earth’s colder climates = alcohol temperatures preferred Official temperature measurements = made in the shade Thermistor = measures temperature by sensing the electrical resistance of a semiconducting material A goal of the Global Climate Observing System = make a reference network of one station per 250,000 km^2 across the globe Land- Surface Temperature (LST) = the heating of the land surface’ often much hotter than air temperature; record the heating of the ground from insolation and other heat flows LST = higher in dry environments with clear skies and surfaces with low albedo Three expressions of temperature: 1. Daily Mean Temperature 2. Monthly Mean Temperature 3. Annual Temperature Range Principle Temperature Controls Insolation = most important influence on temperature variations Effects of human activity = changing some natural controls on temperature (latitude, altitude and elevation, cloud cover, and land-water heating differences) Soot = cause of warming temperatures Latitude Subsolar Point = the latitude where the Sun is directly overhead at noon Insolation more intense = between tropics At higher latitudes = sun is never directly overhead during the year Intensity of the sun’s radiation= decreases away from equator and toward the poles Daylength = varies with latitude Seasonal effect of latitude on temperature are driven by two factors: 1. Sun angle 2. Daylength Altitude and Elevation Within troposphere = temperatures do down as altitude goes up; density also decreases Normal Lapse Rate = 6.4 degrees Celsius/1000m Atmosphere thins = has less sensible heat Mountainous Areas = experience lower temperatures than regions near the sea level Altitude = airborne objects or heights above Earth’s surface Elevation = the height of a point on Earth’s surface above some plane of reference High Elevations experience = cooler air temperatures, greater nighttime cooling, temperature range between night and day is greater Snow Line = lower limit of permanent snow and shows where winter snowfall surpasses the amount of snow lost through summer melting and evaporation Cloud Cover 50% of earth = covered by clouds Dawn = coldest time of the day Night = clouds are insulating (reradiating longwave energy back to Earth) Clouds = raise minimum nighttime temperatures Day = reflect sun’s radiation; lower daily maximum temperatures Clouds also decrease seasonal temperature differences Land-Water Heating Differences Water bodies = more moderate temperature patterns Continental Interiors = more temperature extremes Land = heats and cools faster than water Evaporation Disperses a lot of the energy that comes at the ocean’s surface 84% evaporation = from the oceans Surface Water evaporates = absorbs energy from the environment (results in lowering of temperatures) Land temperatures = effected less by evaporative cooling Transparency Light that hits the surface is absorbed When light reaches a body of water = it penetrates the surface Below surfaces = temperatures remain the same Water’s transparency = water is clear, and light passes through it to an average depth of 60m in the ocean Specific Heat The heat capacity of a substance Water = can hold more heat Specific Heat of Water = about four times that of soil Day to Day temperatures near water = moderated rather than containing big extremes Movement Movement of currents = a mixing of cooler and warmer waters and it spreads the energy Surface water and deeper waters mix as well to distribute the energy again in a vertical direction Ocean and land surfaces = radiate longwave radiation at night Land = looses energy more quickly Ocean Currents and Sea-Surface Temperatures Cool ocean currents (coming toward the equator) = make air temperatures less extreme (on land); this happens along subtropical and midlatitude west coasts of continents Gulf Stream = warm current; travels northward off the east coast of North America Water vapor content of air increases = ability for air to absorb longwave radiation increases Warm ocean and air = more evaporation occurs (increase in the water vapor coming into the air) Sea-Surface Temperature = SST Western Pacific Warm Pool = temperatures are often above 30 degrees Celsius Examples of Marine Effects and Continental Effects Marine Effect (maritime effect) = the moderating influences of the ocean and normally happens in locations along coastlines or on islands Continental Effect (condition of continentality) = the biggest range between maximum and minimum temperatures on both a daily and a yearly basis that happens in locations that are inland (from the ocean) or distant from other big water bodies Earth’s Temperature Patterns Isotherm = an isoline that connects points of equal temperature to show the temperature pattern Isoline = a line along which there is a constant value January and July Global Temperature Maps January in Southern hemisphere = high sun altitude and longer days cause summer weather conditions January in Northern hemisphere = lower sun altitudes and short days cause winter weather conditions Thermal Equator = an isotherm connecting all points of highest mean temperature July in Northern Hemisphere = isotherms shift towards the poles over land Hottest places in Northern Hemisphere in July = deserts (examples – Sonoran Desert of North America, the Lut Desert in Iran) January and July Polar-Region Temperature Maps North Polar Region = an ocean surrounded by land South Polar Region = big Antarctic ice sheet surrounded by ocean Antarctica summer = December and January Antarctica = Earth’s highest and coldest region Arctic ocean summer = July July in Antarctica = nights are 24 hours long Annual Temperature Range Map Subpolar Locations within the continental interiors of Asia and North America= largest average annual temperature ranges Southern Hemisphere = smaller temperature ranges (show less seasonal temperature variation) Continental Effects = the Northern Hemisphere Marine Effects = the Southern Hemisphere Recent Temperature Trends and Human Response Global Temperatures = went up an average of .17 degrees Celsius (per decade) (1970 and up) Heat waves = on the rise Record Temperatures and Greenhouse Warming Temperature Anomaly = an irregularity or difference located by differentiating recorded average annual temperature against the long-term average yearly temperature for a time period chosen as the baseline Baseline = base period Trend on the maps from 1970s to 2000s = above average temperatures Human Activities = increase atmospheric greenhouse gases Human Action = forces climate change Global warming and global climate change = not the same Climate Change = surrounds all effects of atmospheric warming (effects – relate to humidity and vary with location Heat Stress and the Heat Index Heat Wave = a lengthy period of abnormally high temperatures (sometimes related with weather that is humid) Human Body Temperature = within 36.8 degrees Celsius Body temperature lower = in cold weather and in the morning Body temperature higher = during work or exercise and emotional situations Amount of Water Vapor high = relative humidity is high A Heat Index shows temperatures and relative humidity Heat Stress = the risk of heat-related illness Examples of Heat Stress in People = heat stroke, heat exhaustion, and heat cramps