Lecture 7 Climate and Climate Classification PDF

GEOG 111: INTRODUCTION TO PHYSICAL GEOGRAPHY Lecture 7: Climate and Climate Classification Instructor: Dr. Peter Bilson Obour 1  Learning Goals Understand climate classifications Describe the cl...

GEOG 111: INTRODUCTION TO PHYSICAL GEOGRAPHY Lecture 7: Climate and Climate Classification Instructor: Dr. Peter Bilson Obour 1  Learning Goals Understand climate classifications Describe the climate classes identified by the Köppen’s classification system.  Global Climatic Regions Climate could be defined as the average weather conditions of a large area studied over a long period of time Study of climate involves the study of trends in elements of weather. These elements include: Temperature Precipitation Pressure  Elements and Variations  Temperature of an area: – Its mean or average: a. Annually b. Monthly c. Average monthly daytime highs and nighttime lows – Its typical degree of variation: a. Range or standard deviation in annual averages b. Range or standard deviation in monthly averages c. Range or standard deviation in monthly highs and lows – When the highest and lowest monthly averages are experienced  Precipitation: – Types commonly experienced: rain, snow, sleet, hail – Averages a. Annual receipt b. Receipt by month – Typical variation a. Extreme ranges annually and monthly b. Standard deviations annually and monthly  When the highest and lowest monthly averages are experienced  Duration of drought  Classification of Climate  A number of climate classification systems are encountered in physical geography.  They might be based on annual and monthly averages of temperature and precipitation or perhaps on the balance between precipitation and potential evapotranspiration (itself based on temperature).  There are three fundamental types of classifications used in climatology  Classification of Climate  Empirical systems: Classification based on observable features. The Köppen system is an empirical system based on observations of temperature and precipitation  Genetic classification systems are those based on the cause of the climate. A genetic system relies on information about the climatic elements of solar radiation, air masses, pressure systems  Applied classification systems created for particular climate- associated problem. The Thornthwaite classification system is one based on potential evapotranspiration and thus groups climates based on water requirements. This classification system grew out of the issue of trying to predict the supply and demand for water in different climate regions.  Classification of Climate  The earliest known climatic classifications were those of Classical Greek times.  Aristotle believed that each of the Earth's hemispheres (Northern and Southern) could be divided into 3 zones  Because these climate zones are classified based on latitude— a geographic coordinate—they're also known as the geographic zones.  Classification of Climate  Warren Thornthwaite developed a water budget approach, based on potential evapotranspiration compared to water receipt  Wladimir Köppen devised a system based on monthly temperature averages and precipitation receipt, which he and his student, Rudolf Geiger put together into a wonderful map of the world's climates, called the Köppen- Geiger map Köppen-Geiger map  World Climatic Regions The Köppen Climate Classification System is the most widely used system for classifying the world's climates Its categories are based on the annual and monthly averages of temperature and precipitation. The Köppen system recognizes five major climatic types; each type is designated by a capital letter.  World Climate Classification A - Tropical Moist Climates: all months have average temperatures above 18° Celsius. B - Dry Climates: with deficient precipitation during most of the year. C - Moist Mid-latitude Climates with Mild Winters. D - Moist Mid-Latitude Climates with Cold Winters. E - Polar Climates: with extremely cold winters and summers.  Tropical Moist Climates (A)  Tropical moist climates extend about 15 to 25° northward and southward from the equator  In these climates all months have average temperatures greater than 18° Celsius.  Annual precipitation is greater than 1500 mm.  Three minor Köppen climate types exist in the A group,  Their designation is based on seasonal distribution of rainfall.  Af or tropical wet is a tropical climate where precipitation occurs all year long. – Monthly temperature variations in this climate are less than 3° Celsius. – Because of intense surface heating and high humidity, cumulus and cumulonimbus clouds form early in the afternoons almost every day. – Daily highs are about 32° Celsius, while night time temperatures average 22° Celsius. Af - Andagoya, Columbia 5° N , Elevation: 65 m Sept Jan. Feb. Mar. Apr. May June July Aug. Oct. Nov. Dec. Year. Temp. 27 27 28 28 27 27 27 27 27 27 27 27 27 °C Precip. 554 519 557 620 655 655 572 574 561 563 563 512 6905 mm  Tropical Moist Climates (A)-Cont. Am is a tropical monsoon climate – Annual rainfall is equal to or greater than Af, but most of the precipitation falls in the 7 to 9 hottest months. – During the dry season very little rainfall occurs.  Am - Mangalore, India 13° N , Elevation: 22 m Ja n Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year. Temp. ° 27 27 28 29 29 27 26 26 26 27 27 27 27 C Precip. m 5 2 9 40 233 982 1059 577 267 206 71 18 3467 m  Tropical Moist Climates (A)-Cont. The tropical wet and dry or savanna (Aw) – has an extended dry season during winter. – Precipitation during the wet season is usually less than 1000 mm, and only during the summer season.  Aw - Calcutta, India 22.5° N , Elevation: 6 m Dec Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Year. Temp. 20 23 28 30 31 30 29 29 30 28 24 21 27 °C Precip. 13 24 27 43 121 259 301 306 290 160 35 3 1582 mm  Aw - Cuiaba, Brazil 13.5° S , Elevation: 165 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. 27 27 27 27 26 24 24 26 28 28 28 27 27 °C Precip. 216 198 232 116 52 13 9 12 37 130 165 195 1375 mm  Dry Climates (B) The most obvious climatic feature of this climate is that potential evaporation and transpiration exceed precipitation. This climatic region extends from 20 - 35° North and South of the equator In large continental regions of the mid-latitudes often surrounded by mountains Characteristics: – low relative humidity and cloud cover – low frequency and amount of precipitation. – high mean annual temperature. – high monthly temperatures. – high diurnal temperature ranges. – high wind velocities.  Dry Climates (B)-cont. Minor types of this climate include: BW - dry arid (desert) is a true desert climate. o It covers 12% of the Earth's land surface and is dominated by xerophytic vegetation. o The additional letters h and k are used generally to distinguish whether the dry arid climate is found in the subtropics or in the mid-latitudes, respectively  BWh - Berbera, Somalia 10.5° N , Elevation: 8 m Sept Jan. Feb. Mar. Apr. May June July Aug. Oct. Nov. Dec. Year. Temp. 25 26 27 29 32 37 37 37 34 29 26 26 30 °C Precip. 8 2 5 12 8 1 1 2 1 2 5 5 52 mm  Dry Climates (B)-cont. BS - dry semiarid (steppe). o Is a grassland climate that covers 14% of the Earth's land surface. o It receives more precipitation than the BW either from the intertropical convergence zone or from mid-latitude cyclones o The additional letters h and k are used generally to distinguish whether the dry semiarid climate is found in the subtropics or in the mid-latitudes, respectively  BSk - Denver, Colorado, USA 40° N , Elevation: 1611 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. -1 1 4 9 14 19 23 22 17 11 4 -1 10 °C Precip. 14 16 34 45 63 43 47 38 28 26 23 15 391 mm  Moist Subtropical Mid-Latitude Climates (C)  This climate generally has warm and humid summers with mild winters.  Its extent is from 30 to 50° of latitude mainly on the eastern and western borders of most continents.  During winter, the main weather feature is the mid-latitude cyclone.  Convective thunderstorms dominate summer months.  Three minor types exist: Cfa - humid subtropical – The humid subtropical climate (Cfa) has hot muggy summers and frequent thunderstorms. – Winters are mild and precipitation during this season comes from mid- latitude cyclones. – A good example of a Cfa climate is the southeastern USA.  Cf - New Orleans, USA 30° N , Elevation: 1 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. 12 13 16 20 24 27 28 28 26 21 16 13 20 °C Precip. 98 101 136 116 111 113 171 136 128 72 85 104 1371 mm  Moist Subtropical Mid-Latitude Climates (C)-cont. Cfb - marine. – marine climates are found on the western coasts of continents. – They have a humid climate with short dry summer. – Heavy precipitation occurs during the mild winters because of the continuous presence of mid-latitude cyclones. Cs - Mediterranean; – Mediterranean climates (Cs) receive rain primarily during winter season from the mid-latitude cyclone. – Extreme summer aridity is caused by the sinking air of the subtropical highs and may exist for up to 5 months. – Locations in North America are from Portland, Oregon to all of California.  Cf - London, England 51.5° N , Elevation: 5 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. 4 4 7 9 12 16 18 17 15 11 7 5 10 °C Precip. 54 40 37 38 46 46 56 59 50 57 64 48 595 mm  Moist Continental Mid-latitude Climates (D)  Moist Continental Mid-latitude Climates (D)  Moist continental mid-latitude climates have warm to cool summers and cold winters.  The location of these climates is pole ward of the C climates.  The average temperature of the warmest month is greater than 10° Celsius, while the coldest month is less than -3° Celsius.  Winters are severe with snowstorms, strong winds, and bitter cold from Continental Polar or Arctic air masses.  Like the C climates there are three minor types: – Dw - dry winters; – Ds - dry summers; – Df - wet all seasons.  Dw - Calgary, Canada 51° N , Elevation: 1140 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. -10 -9 -4 4 10 13 17 15 11 5 -2 -7 4 °C Precip. 17 20 26 35 52 88 58 59 35 23 16 15 444 mm  Polar Climates (E)  Polar climates have year-round cold temperatures with the warmest month less than 10° Celsius.  Polar climates are found on the northern coastal areas of North America, Europe, Asia, and on the landmasses of Greenland and Antarctica.  Two minor climate types exist. ET or polar tundra – climate where the soil is permanently frozen to depths of hundreds of meters, a condition known as permafrost. – Vegetation is dominated by mosses, lichens, dwarf trees and scattered woody shrubs. EF or polar ice caps has a surface that is permanently covered with snow and ice.  EF - Plateau Station, Antarctica 79° S , Elevation: 3625 m Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year Temp. -34 -44 -57 -66 -66 -69 -68 -71 -65 -60 -44 -32 -56 °C Precip. NA NA NA NA NA NA NA NA NA NA NA NA NA mm  Highland Climate (H)  Highland climate is designated by letter H  Major climate type often added to the Köppen classification, although it was not part of the original or revised systsms by Köppens.  Highland climates occupy mountains and high plateaus at any latitude.  It includes all highland areas not easily categorized by other climate types.  The major highland regions of the world (Sierra Nevada, and the Rockies of North America, the Andes of South America, the Himalayas and Tibet plateau in Asia, the eastern highlands of Africa.  Highland Climate (H)-cont.  They tend to be cool to cold because air temperatures in the atmosphere normally decrease with altitude  The reduced amount of air overhead results in high atmospheric transparency and enhanced receipt of solar radiation, especially ultraviolet wavelength at elevation.  Mountains can act as barriers to the movement of air masses, which causes differences in precipitation amounts between windward and leeward slopes.  Highland areas usually derive their annual temperature cycle and the times of their wet and dry seasons from the climate of the surrounding  Strengths of Köppens Classification  This classification scheme uses certain critical values of temperature of the warmest and the coldest months and precipitation of the wettest and the driest months.  The weather elements, temperature and precipitation, affect other aspects of our physical environment more directly than any other elements.  The system of classification devised by Köppens is directly related to those aspects of the environment which are clearly visible to us.  The Köppen climate system is easy and convenient to use, given monthly weather data.  Message At first the classification scheme may look a bit difficult, but its close examination reveals that it is based on certain critical values with which all geography students soon become familiar. End of Class 39