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Chapter 5 Atmosphere and Climatic Differentiation Section 1 Composition and structure of the atmosphere Section 2 Atmospheric circulation Section 3 Material movement Section 4 Energy flow Section 5 Climatic differentiation Section 6 Atmosphere and humankind Chapter 5 Composition and structure of the atmosphere Composition of the atmosphere: The earth’s surface atmosphere is comprised of N2, O2, Ar etc. . Structure of the atmosphere : The atmosphere is divided into troposphere, stratosphere, mesosphere, thermosphere and exosphere on elevation direction. Troposphere: The lowest layer of the atmosphere between the earth's surface and the tropopause, characterized by decreasing temperature with increasing altitude,prominent convection movement, complex and varied weather . Stratosphere: The layer of atmosphere between tropopause and 50~55 km. Mesosphere: The layer of atmosphere between stratopause to 80~85 km. Thermosphere: The layer of atmosphere between the top of mesosphere to 800 km. Exosphere: The outermost layer of Earth's atmosphere, lying above the thermosphere. Chapter 5 Composition of the Atmosphere N2 Ar others Composition of the Atmosphere Chapter 5 Table Composition of the atmosphere Composition N2 Volume percent 0.78083 Composition Volume percent 1.1X10-6 O2 0.20947 Kr Xe Ar 0.00934 Rn 0.5X10-6 CO2 0.00035 CH4 1.7X10-6 Ne 1.82X10-6 0.3X10-6 He 5.2X10-6 N2O O3 0.1X10-6 (10~50)X10-8 The earth’s atmosphere is mainly comprised of nitrogen and oxygen. Currently , the minor and trace constituents such as CO2, O3, H2O and aerosols are mostly concerned. This is because these minor constituents have distinctly space-time variation, and can severely affect the thermal income-expenses of earth-atmosphere system, the vertical distribution of temperature, and humankind. Main gas composition ,content and molecular weight of the atmosphere Chapter 5 Table main gas composition and content of the atmosphere Main composition N2 O2 Ar CO2 O3 CH4 H2O Percent of volume 78.08 20.95 0.93 0.03(variable) 0.000001(variable) 0.000165 variable Average longevity/year 106 104 109 15 ? 7 10days Molecular weight 28.02 32.00 39.94 44.00 48.00 16.04 18 The atmosphere is a mixture of gases. 99% of the atmosphere consists of Nitrogen(78%) and oxygen(21%).The remaining 1% of the atmosphere is comprised of H2, CO2 , O3 , H2O and solid particles etc. The concentration change of ozone with altitude is incontinuous.Ozone is found in minute amounts near the surface and increases gradually from 10km. Most of ozone is found between 10km and 50km. There is very little ozone above 50km. Only 10% ozone is concentrated in troposphere and most is in stratosphere. The greatest concentrations of ozone are found between 20 and 30km, known as ozone layer. According to observation,the addition of N2O and CFCs to the atmosphere may decrease ozone amount in the stratosphere, whereas the addition of CH4 may increase ozone amount. Altitude(km) Chapter 5 Ozonic concentration variation with altitude Ozone layer Concentration(m-3) Chapter 5 Seasonal variation and latitude distribution of ozone Ozone distribution changes with seasons and latitudes. The greatest concentrations of ozone are found near 60o latitude and the least near equator. In addition, the maximum of ozone are found in spring and the minimum in autumn. month Average gross of ozone Chapter 5 Vertical Layering of atmospheric temperature, density and composition The air density decreases gradually with altitude because of the reducing of the earth’s gravitation, and almost equals to the density of the interstellar gas above the atmosphere. From surface to high altitude, except differentia of the density and composition, the temperature varies distinctly. Three warmer layers and two cooler layers are formed on vertical direction of the atmosphere. The atmosphere is divided into troposphere, stratosphere, mesosphere, thermosphere and exosphere according to vertical temperature distribution by WMO. Chapter 5 Atmospheric circulation Level pressure gradient force: It is a motivity of pushing air from stillness to motion. Its direction is the same as level pressure gradient, and points from high pressure to low pressure. Deflection force of earth rotation(Coriolis effect): The Coriolis effect is a result of the earth’s rotation. This effect notes that an object in motion on the earth surface always appears to be deflected away from its course. The apparent deflection is to the right in the northern hemisphere and to the left in the southern hemisphere. Atmospheric convergence: Airflow concentrating toward the center of a low- pressure. Atmospheric divergence: Airflow fanning out and moving away from the center of a high-pressure. Cyclone, Anticyclone: Cyclone are low-pressure regions of ascending, spiraling air currents. Anticyclone are high-pressure spirals of descending or subsiding air. In the northern hemisphere, cyclones rotate counterclockwise and anticyclones have a clockwise spiral. Chapter 5 Atmospheric circulation Atmosphere circulation:With the effect of the solar radiation, the earth’s rotation, the ground surface characteristic and friction with the ground surface, the air is formed three-dimensional motion of different scale. Monsoon : Prevailing winds vary distinctly between winter and summer. with seasons in a large range Local winds : sea and land breezes:They take place at coastal area and alternate in direction from day to night. During the day ,sea breezes flow from sea to land. Late at night , land breezes flow from land to sea. Plateau monsoon:It results from thermal differentia between the plateau and surrounding free air, and causes reversed prevailing wind systems between winter and summer. Mountain and valley breezes:They are local winds that alternate in direction from day to night. During the day ,the wind moves from valleys to mountain slopes. At night, the wind blow from mountain slopes to valleys. Foehn:As winds flow down the leeward slope after crossing the mountains, the air is compressed and heated at a greater rate, they enter the valley below as warm and extremely dry winds. Heat-island effect:The urban temperature is always higher than that of suburbs and countries. Chapter 5 The coriolis effect and deflection of objects motion The pressure gradient force tends to move air from high to low pressure. For large wind systems ,however ,the direction of air motion will be somewhat different.The difference is due to the earth’s rotation ,and called Deflection force of earth rotation or Coriolis effect.This effect notes an object in motion on the earth’s surface always appears to be deflected away from its course.The apparent deflection is to the right in the northern hemisphere and to the left in the southern hemisphere. The deflective maximum are at poles. At Equator,there is no deflection. The directions of the force are always perpendicular to the motion course.The faster the object is moving, the greater will be the apparent deflection. North pole Deflection to right Equator No deflection Deflection to left South pole Chapter 5 Cyclones and Anticyclones A parcel of air in motion near the surface is subjected to three influences: (1)the pressure gradient that propels the parcel toward low pressure;(2)the Coriolis effect that turns the parcel to the side; and(3) friction with the ground surface. For low-pressure centers(left side), the wind will be deflected into an inward-moving spiral pattern,or inspiral. In northern hemisphere ,the inspiral will be counterclockwise.In the southern hemisphere, the inspiral will be clockwise.Meteorologists use the term cyclone. For high-pressure(right side), the situation is reversed. Air moving outward forms outspiral, clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.This outspiral is referred to as an anticyclone. Northern hemisphere Cyclones Anticyclones Southern hemisphere Chapter 5 The relationship of convergence and divergence ,cyclone and anticyclone (after Strahler) The figure to the right shows an anticyclone and a cyclone linked together in a convection loop. In the anticyclone, air converges aloft and descends in the spiraling motion. Near the surface, the flow diverges, fanning out and moving away from the center of the anticyclone.In the cyclone,air converges near the surface and spirals and upward. Aloft,the air diverges and spirals outward. Convergence Divergence Anticyclone Divergence Convergence Cyclone Chapter 5 Single circulation cell There is formed temperature gradient on the earth from equator toward poles with the heating of the solar radiation. It causes air temperature of the equator region to rise, the air expands and ascends. At one time the air over poles shrinks and descends because of cooling. It will form pressure gradient toward poles on upper atmosphere, and air flows from equator to poles. At lower atmosphere, the pressure gradient will point toward equator, and air flows from poles to equator. Supposing the earth’s surface is featureless -one without a complicated pattern of land and water , and no the earth’s rotation, it will form a single closed circulation between equator and pole by direct Chapter 5 Surface atmospheric circulation on an ideal earth(three circulation cells) On an ideal earth-one without a complicated pattern of land and water, the atmosphere is only affect by the solar radiation and the earth’s rotation, global surface pressure systems are: equatorial trough,two subtropical high-pressure belts,two subpolar low-pressure belts,and two polar high-pressure belts.Wind systems are northeast trades and southeast trades, prevailing westerlies and polar easterlies on the northern and southern hemisphere.Along the longitudinal direction, there form three circulation cells: Hadley cell, Ferrel and Polar cells. Chapter 5 Average sea level pressure in the northern hemisphere in July In the northern hemisphere in July, main pressure system are: Pacific High, Azores High, Southern Asia Low and Southwestern North America Low. The Aleutian and Icelandic Lows nearly disappear from the oceans. L H L H H H L H Chapter 5 Average sea level pressure in the northern hemisphere in January In the northern hemisphere in January, main pressure systems are:Siberian High, Canadian High, Icelandic Low and Aleutian Low. At the same time, the subtropical highs of the northern hemisphere appear slightly south of their average annual position because of the migration of the sun toward the Tropic of Capricorn L L H H H H L H H Chapter 5 Sea and Land Breezes Sea and land breezes alternate in direction from day to night. On a clear day,the sun heats the land surface rapidly,and a shallow air layer near the ground is strongly warmed.The warm air expands and rises. Thus low pressure is formed over the coastal belt.Pressure remains higher over the water.This means that there is a pressure gradient from ocean to land,and a wind is set in motion. At night ,the land surface cools rapidly if skies are clear.A cooler, denser air layer of high pressure develops.Now the pressure gradient is from land to ocean ,setting up a land breeze. Sea and land breezes affect distinctly the coastal weather and climate. Water vapor is transferred by Sea breeze from sea to land and makes more fogs and low clouds,and more precipitation on the coastal belts. At the same time,the winds adjust the coastal temperature and make there not too hot in summer and not too cold in winter . Sea breeze warm Land breeze cool cool warm Chapter 5 Qinghai-Tibet plateau and average longitudinal circulation(Molnar,1993) On a tall and great plateau, because of thermal differentia between the air near the plateau surface and surrounding free air, it causes reversed prevailing wind systems between winter and summer,called plateau monsoon. Qinghai-Tibet plateau monsoon is the most typical. In winter, a cold highpressure is formed over the plateau surface, and air flows from plateau to surroundings. A warm low-pressure is formed in summer, and air flows from surroundings to plateau. Plateau monsoon greatly affect the air circulation and climate, especially to east Asia and south Asia monsoon 。The direction of plateau monsoon is the same as that of east Asia monsoon formed by thermal differentia between land and ocean.It makes east Asia monsoon (special winter wind) specially strong and more thickness. January July Chapter 5 Mountain winds and Valley winds Mountain winds and valley winds are local winds that alternate in direction from day to night. During the day,mountain hill slopes are heated intensely by the sun, causing air to rise. To take place of the rising air,a current moves up valleys from the plains belowupward over rising mountain slopes, toward the summits. At night,the hill slopes are chilled by radiation. The cooler, denser hill slope air then moves valleyward,down the hill slopes, to the plain below. (a)valley winds warm cool (b)mountain winds warm cool warm cool Chapter 5 Foehn winds Foehn winds result when air ascends a mountain range and undergoes condensation that dries it out and add latent heat that slows its rate of cooling.As the dry air descends the leeward side of the range, it is compressed and heated at a greater rate.Thus they enter the valley below as warm,dry winds.The rapid temperature rise brought about by such winds has been known to damage crops,increase forest fire hazard,and set off avalanches. Temperature(0C) Chapter 5 “Urban heat-island” City is a populous region,and has developed industries. Large man-made heat is released by citizens, industries and vehicles, and causes urban temperature higher than that of suburbs and countries. The city is like a warm island, known as “urban heat-island”. The formation of “heat-island” is because the air over city obtains sensible heat from warm buildings by turbulent diffusion, and absorbs long- wave radiation from urban surface and polluted layer. Because of “heat-island effect”, the mean annual temperature of cities are higher 0.5~1℃ than that of the suburbs。 Chapter 5 Material movement Water vapor movement: Vertical transmission; Horizontal transmission(transmission between high and low latitude; transmission between land and ocean) Dioxide dioxide movement: CO2 diffuses and transmits from source to surroundings and higher atmosphere. Aerosols movement: Aerosols diffuses and transmits from source to surroundings and higher atmosphere. Chapter 5 Energy flow Energy flow between high latitude and low latitude : It mainly depends on global atmospheric circulation(direct and latent heat energy and oceanic flows). Energy flow between sea and land:In winter,oceans are heat sources and lands are cold regions, heat energy is transferred from ocean to land. Nearer to the ocean, more heat transferred, higher temperature it is. Energy flow between high and low altitude:In troposphere, energy is transferred between high and low altitude because of air convection. Chapter 5 Heat energy transfer and global energy balance(after Strahler) The energy transfer between equator and polar regions mainly depends on global atmospheric circulation (sensible and latent heat and oceanic flows), and it varies with latitudes and seasons. Global heat energy transfers from surplus regions of energy ( 350S~350N) to deficit regions (higher latitude 350 north and south). The greatest amount of heat is transferred near latitude 400 at average. Radiation deficit Longitudinal energy transfer Radiation surplus Chapter 5 Climatic differentiation Temperature differentiation:Temperature distribution is affected by the factors of latitude, ocean and land,landform and altitude etc.. Thereinto the latitude determine zonality differentiation of temperature. and ocean and land, landform and altitude are factors that influence non- zonality differentiation of temperature。 Humidity and precipitation differentiation:water vapor is abundant over oceans and short over land. Humidity is gradually minished from coastal to inland. Climatic differentiation: Latitudinal zonality: Unequal surface heating of the solar radiation is the dominant factor of climate formation, and accompanying the distribution of global pressure and wind belts,and seasonal motion, these result in climate types subrogation along latitude. Humidity zonality the difference between ocean and land cause climatic elements, such as temperature,pressure, directions of wind and precipitation etc. to change with seasons, and bring differentiation of continental and maritime climate in same latitude belt. Vertical zonality:On different altitude of a tall and great mountain , varied temperature and precipitation combination form different water and heat characteristic, and cause mountain climate change along vertical direction. Chapter 5 Average sea level temperature in January (0C) Chapter 5 Average sea level temperature in July (0C) Chapter 5 Average precipitation distribution in the Earth (Moller,1951) Dec.~Feb. Average precipitation distribution Chapter 5 in the Earth (Moller,1951) Jun.~Aug. The comparison between Chapter 5 maritime and continental climate Maritime climate T 1. Both daily and annual range of temperature are little. Warm in winter and cool in summer. It is warmer than the same latitudinal continent in winter and cooler in summer. 2. Both the warmest and coldest month occur later. In temperate zone, the warmest month is August, the coldest month is February. 3. The temperature in Autumn is higher than that in Spring. Continental climate 1. Both daily and annual range of temperature are large. Cold in winter and hot in summer. 2. Both the warmest and coldest month occur earlier. In temperate zone, the warmest month is July, the coldest month is January. 3. The temperature in Spring is higher than that in Autumn. The comparison between Chapter 5 maritime and continental climate Maritime climate P O t h e r s Continental climate 1. The amount of rainfall is abundant. 1. The amount of rainfall is short. 2. Annual percipitation distribution 2. Percipition mainly concentrates in summer. is even. 3. Less annual percipitation variation . 3.More annual percipitation variation . 4.Convection rainfall often occurs in the afternoon in summer. 1. High air humidity, heavy cloud 1. Low air humidity, slight cloud cover. cover. 2. Less day with fog, more radiation 2. More day with fog, more fogs. advection fogs. 3. High percentage of sunshine. 3. Low percentage of sunshine . 4.Slow wind speed. Obvious wind speed 4. Rapid wind speed. Little wind daily variation. speed daily variation. Chapter 5 Vertical climatic zone and natural zone on the north slope of changbai Mountain A tall and great mountain has two influences to climate: on the one hand, it impedes airflow’s motion and becomes barrier of airflow’s motion, thereby it may result widely different climate on two sides of a mountain, and break the climatic latitudinal zonality on a certain extent; On the other hand, on different altitude of a tall and great mountain , varied temperature and precipitation combinations form different water and heat characteristics, and cause mountain climate to change along vertical direction, namely vertical zonality, and form a special climatic type-mountain climate. Alpine desert climatic zone Alpine shrub climatic zone Montane birch climatic zone Montane conifer forest climatic zone Montane broad-leaf forest climatic zone Chapter 5 Atmosphere and humankind Composition of the atmosphere and humankind Human activities and atmosphere Weather,climate and humankind Suitable temperature, humidity, wind and sunshine are beneficial to people’s health, whereas some conditions help in the growth of some viruses and bacteria ,and harmful to people’s health.