Chapter 11: Atmosphere

Transcription

1 Chapter 11: Atmsphere Sectin 1: Atmspheric Basics Objectives 1. Describe the cmpsitin f the atmsphere. 2. Cmpare and cntrast the varius layers f the atmsphere. 3. Identify three methds f transferring energy thrughut the atmsphere. A. Atmspheric Cmpsitin N 2 + O 2 + ther, including Ar, H 2 O vapr, CO 2, and trace gases such as H, He, Ne, methane (CH 4 ), zne (O 3 ), Kr, and Xe The atmsphere als cntains tiny particles f dust, salt, and ice. Key Atmspheric Gases The amunt f H 2 O vapr varies ( 4%) with the seasns, with the altitude f a particular mass f air, and with the surface features beneath the air. is the nly substance in the atmsphere that exists in three states: slid, liquid, and gas. When H 2 O changes frm ne state t anther, heat is either absrbed r released, which greatly affects weather and climate. The amunt f CO 2 varies ( 1%) with the seasns and with fssil fuel cmbustin emissins. Bth CO 2 and H 2 O vapr help regulate the amunt f energy the atmsphere absrbs. Ozne (O 3 ) Fund primarily in the zne layer f the stratsphere - Is imprtant because it absrbs - Evidence indicates that the zne layer is thinning A. Structure f the Atmsphere Made up f several layers, which differ in cmpsitin and temperature 1. Trpsphere Is the layer clsest t Earth s surface Cntains mst f the atmsphere s mass (due t gravity), s pressure (P) and density (D) are highest nearest the surface Has an upper limit called the trppause, which varies in height 2. Stratsphere Is lcated abve the trppause T increases (P and D decrease) with altitude Has an upper limit called the stratpause 11-1

2 3. Messphere Is lcated abve the stratpause T decreases (P and D decrease) with altitude Has an upper limit called the mespause 4. Thermsphere Is lcated abve the mespause Cntains nly a minute prtin f the atmsphere s mass T increases (P and D decrease) with altitude 5. Exsphere Is the utermst layer f Earth s atmsphere Fades int space There is n abslute bundary between Earth s atmsphere and space. B. Slar Fundamentals The Sun is the surce f all energy in the atmsphere. Slar energy is transferred t Earth and thrughut the atmsphere thrugh radiatin, cnductin, and cnvectin. 1. Radiatin Is absrbed by Earth, which als cntinuusly sends energy back int space Absrptin rates depend n and Mst slar radiatin travels thrugh the atmsphere at wavelengths, which are nt easily absrbed Earth s surface re-radiates energy with wavelengths, which warms the atmsphere thrugh and 2. Cnductin Is the transfer f energy that ccurs when mlecules cllide Affects nly a very thin atmspheric layer near Earth s surface 3. Cnvectin Is the transfer f energy by the flw f a heated substance 11-2

3 Creates, which are partially respnsible fr and, in turn, (1) Pckets f air near Earth s surface are heated, becme less dense than the surrunding air, and rise. (2) As the warm air rises, it expands and starts t cl. (3) When it cls belw the temperature f the surrunding air, it increases in density and sinks. Sectin 2: State f the Atmsphere Objectives 1. Describe the varius prperties f the atmsphere and hw they interact. 2. Explain why atmspheric prperties change with changes in altitude. A. Temperature vs. Heat Temperature (T) Is a measurement f hw rapidly r slwly mlecules mve arund Can be measured in degrees Fahrenheit ( F), Celsius ( C), r in kelvins (K; SI unit) Freezing Pint* f H 2 O Biling Pint* f H 2 O Abslute Zer* F F -523 F C C -273 C K K 0 K *Measured at P = 1 atmsphere (atm) : the pint at which mlecular mtin theretically stps Heat Is the transfer f energy that ccurs because f a difference in T between substances «Heat is the transfer f energy that fuels atmspheric prcesses, while T is used t measure and interpret that energy. : the T t which air must be cled at cnstant pressure t reach saturatin : the pint at which the air hlds as much water vapr as it pssibly can and at which cndensatin can ccur : change in state frm a gas t a liquid B. Vertical Temperature Changes Dry adiabatic lapse rate 11-3

4 Is the rate at which rising unsaturated air, t which n heat is added r remved, will cl If the air cntinues t rise, it will eventually cl t its cndensatin T at an altitude knwn as the, r LCL. Abve the LCL, air is saturated and cls mre slwly. Mist adiabatic lapse rate Is the rate at which saturated air cls (ranges frm abut 4 C/1000 m in very warm air t almst 9 C/1000 m in very cld air) C. Pressure-Temperature-Density Relatinships Hwever, in mst atmspheric interactins, neither D nr P remains unchanged. T varies with changes in bth P and D; T is prprtinal t the rati f P t D, which decreases with increasing altitude. D. Wind Temperature inversin - Is an increase in T with altitude in an atmspheric layer - Can ccur when the lwer layers f the atmsphere lse heat t Earth s surface and becme cler than the air abve them - Can act like a lid t trap pllutin under the inversin layer - Can have a prfund effect n weather cnditins Mves faster with increasing altitude (generally) E. Humidity vs. Relative Humidity : the amunt f water vapr in air Air in the lwer prtin f the atmsphere always cntains at least sme water vapr. Relative humidity (RH) Is the rati f water vapr in a vlume f air cmpared t hw much water vapr that vlume f air is capable f hlding - If the T f air increases and n additinal water vapr is added, its RH decreases. - If mre water vapr is added t the air, its RH increases. 11-4

5 Is expressed as a percentage: If a certain vlume f air is hlding as much water vapr as it pssibly can, then it s RH = 100%. If that same vlume f air is hlding half as much water vapr as it can, its RH = 50%, and s n. Sectin 3: Misture in the Atmsphere Objectives 1. Explain hw cluds are frmed. 2. Identify the basic characteristics f different clud grups. 3. Describe the water cycle. A. Clud Frmatin is the tendency fr air t rise r sink as a result f differences in D. Cluds frm (1) (2) Arund, which are small particles in the atmsphere, such as dust, sea salt, sulfur and nitrgen xide aersls. (3) Due t, which ccurs when wind encunters a muntain and is frced upward where it expands and cls. (4) When warmer air cllides with cler air, the majrity f the warmer air will be frced t rise ver the mre-dense, clder air. As the warm air cls, the water vapr in it cndenses, frming a clud. Stability, r the ability f an air mass t resist rising, is determined by hw rapidly any given mass f air cls. The rate f cling depends n the T f rising air relative t the T f the statinary surrunding air that it passes thrugh. If the temperature f the surrunding air falls mre quickly with increasing altitude, it cntinues t rise. «Latent heat is energy stred in water vapr that is released when cndensatin ccurs. The energy stred in the water vapr cmes frm the change in state frm liquid water int water vapr, a gas. As water vapr cndenses back int liquid water, heat is released. «The amunt f water vapr present in the atmsphere is a significant surce f energy because f the latent heat it cntains. 11-5

6 B. Types f Cluds When a rising air mass reaches its, r LCL, its water vapr cndenses int liquid water. If the D f these water drplets is great enugh, they becme visible in the frm f a clud. This prcess can take place at many different altitudes and frm different clud shapes. Clud classificatin was riginally develped in by English naturalist. The mdern classificatin system grups cluds by (1) (usually dented as a prefix): lw cluds that frm belw 2000 m middle cluds that frm between 2000 and 6000 m. Cirr high cluds that frm abve 6000 m and are cmpsed f ice crystals. develp vertically (2) (usually dented as a suffix): gray; precipitatin-prducers layered/featureless sheet puffy/lumpy wispy/stringy «Cluds may be classified as: Stratus, cumulus, and stratcumulus Altstratus, altcumulus, and altcirrus Cirrcumulus, cirrus, and cirrstratus Nimbstratus, nimbus, and cumulnimbus C. Precipitatin ccurs when clud drplets cllide and jin tgether t frm a larger drplet. When the drplet becmes t heavy t be held alft, gravity takes ver and it falls t Earth. includes all frms f water, bth liquid and slid, that fall frm cluds including rain, snw, sleet, and hail. D. The Water Cycle Is the cnstant mvement f water between the atmsphere and Earth s surface. Includes the fllwing prcesses: (1) : H 2 O (liquid) à H 2 O vapr (gas) (2) : H 2 O vapr (gas) à H 2 O (liquid) (3) 11-6