ATMO 336 1st Edition Lecture 5 Outline of Last Lecture II. numerical models of weatherIII. errors in numerical forecastsIV. dilemma for weather forecastersV. ensemble weather forecastingVI. The atmospherea. Defining meteorologyb. Essential functions of atmosphereOutline of Current Lecture VII. Gasa. Defining gas, liquid, and solidsVIII. Kenetic Modela. Temperature of a gasb. Number density of a gasc. PressureIX. Ideal gas lawa. Gas law equation : pressure= temp x number density x constantb. Hold number density constantc. Hold pressure constantX. Relationship between 500mb and air temperatureXI. Thickness: a better estimate for air temp near grounda. 2 reasons for misleading informationXII. Composition of the atmosphere (nitrogen and Oxygen mainly)XIII. Trace components of the atmospherea. Water vaporb. Carbon dioxidec. Methaned. Nitrous oxidee. Ozonef. AerosolsCurrent Lecture- Gaso Gas= individual molecules are not chemically bonded together. Composed of the same molecules that make up liquids and solids, but they are not chemically bonded togetherThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Liquid= molecules are bonded together but the bonds are breaking and reforming, so the substance formso Solid= molecules tightly bonded together in orderly fashion. Bonds are difficult to break and substance does not flow- Kenetic modelo Helps us understand and visualize how matter behaves at the level of individual molecules (mainly in the behavior of gases)o Molecules are too small to observe individually, we must know how they behave individuallyo Energy state of a gas is determined by its Temperature Pressure Densityo Temp measured using thermometers and barometerso Kenetic model= micro scale because molecules are small- Temperature of a gaso Temp determined by the average speed of the molecules making up a substance (higher the temp, the faster they move)o Particles move in random motions- Number density of a gaso Defined as the number of gas molecules per unit volumeo Important property of gases is they can be easily compressed (solids and liquids have fixed volumes, gases are the only ones that can expand)- Pressureo Gas pressure caused by the collisions of gas molecules on a surface.o Each tiny individual collision provides a tiny force on the surface it contacts. Sum total of these forces is the gas pressureo Units= force per area- Ideal gas lawo Gas law equations Pressure= temperature x number density x constant Equivalent to PV=nRTo Hold number density constant If the number density of a gas is held fixed, increasing the temperature o the gas, increases its pressure and decreasing the temperature of the gas, decreases its pressureo Hold pressure constant If the pressure of a gas does not change, increasing the temperature of the gas causes the gas to expand (decrease number density) and decreasing the temperature of the gas causes the gas to contract (increase number density)- Relationship between 500mb and air temperatureo Air pressure decreases more slowly with increasing altitude in a warm column of air compared with a colder column of air.o This explains why higher 500 mb heights are associated with warmer air and lower 500mb heights are associated with colder air- Thickness: a better estimate for air temperature near the groundo 500mb height is not completely determined by the air temp in the lower troposphere (500mb height can be misleading with regard to air temp above the ground). Reasons why: 500mb height does not depend on the sea level pressure (pressure at ground level) Thickness of 1000-500mb is not uniformly warm of cold (can be may sub layers that are either warm or cold). To find surface temp., meteorologists look at 1000-850mb thickness which is more closely related to the air temperature just above the groundo the vertical height between any two pressure levels in atmosphere is related to the temperature of the air between two pressure levels. The warmer the air, the lower the air number density and the greater the vertical distance between two pressure levels- Composition of the atmosphereo Mainly nitrogen and oxygeno Nitrogen removed from atm. Involving soil bacteria. Replenished to atm by decaying of plant and animal mattero Oxygen removed from at when organic matter decayed or for breathing, repleneished byphotosythesis- Trace components of atmosphereo Water vapor: 0.4 % of atmosphere Evaporation= liquid to gas Condensation= gas to liquid Is a strong greenhouse gas (most important of greenhouse gases)o Carbon dioxide= second most important greenhouse gas.concentration has been increasing (increased 35% since 1750)o Methane= increasing due to human activity (increased 150% since 1750)o Nitrous oxide= increased 20% since 1750 mainly due to human activity. Forms in soil by bacterial processes and is destroyed by UV light from suno Ozone= in stratosphere (20-30 km above ground) protects plants animals and humans from harmful UV radiation by absorbing it.very little is found near the ground. High concentration= toxic pollutant (photochemical smog in large cities)o Aerosols= tiny liquid of solid particles suspended in air.  Dust, pollen, smoke, and even cloud droplets Affect propogation of light and visibility if in large concentrations Affect passage of solar radiation through atm Incfluence cloud formation “particulate” air