Metr 100 Section 1 Wednesday (9/2/09) Wednesday (9/2/09) Announcements: Announcements: Reading assignment: Chapters 1 & 2, Ahrens: Essentials of Meteorology. Reading assignment: Chapters 1 & 2, Ahrens: Essentials of Meteorology. A look at the GOES East satellite today (hurricane discussion) A look at the GOES East satellite today (hurricane discussion) Temperature profiles of the atmosphere Temperature profiles of the atmosphere Why does the temperature decrease in troposphere and increase in stratosphere? Why does the temperature decrease in troposphere and increase in stratosphere? Pressure and density profile of the atmosphere Pressure and density profile of the atmosphere Atmospheric composition (partial pressures) Atmospheric composition (partial pressures) A look at a recent soundings (uwyo) A look at a recent soundings (uwyo)

Hurricane Jimena

National Hurricane Center Website:

Oklahoma Weather Lab GOES-W Full View Infrared

Definition of temperature Temperature of gases is a measure of the average kinetic energy (energy of motion) of the molecules of the gas. Kinetic energy is proportional to the mass of the molecules times the square of their velocity Expressed in units of degrees Celsius (°C), degrees Kelvin (°K = °C+273) or (in the US only) degrees Fahrenheit (°F)

Definition of air pressure The force per unit area exerted by air molecules (nitrogen, oxygen, argon, water vapor, etc.) on any surface (the ground, your face, your inner ear, etc.) Expressed in units of millibars (mb), or hectoPascals (hPa) old: inches-Hg What is the unit of pressure we use in the US to check our tire inflation? Pounds/square inch {over atmosphere} Pounds/square inch {over atmosphere}

Definition of Density The ratio of the mass of a substance to the volume occupied by it Expressed in units of kilograms per cubic meter

The vertical temperature distribution of the atmosphere

Graph of pressure vs. height

How air density changes with height

Dalton’s Law of Partial Pressures The total pressure exerted by a mixture of gases which do not interact chemically is equal to the sum of the partial pressures of the gases. The partial pressure of a gas is the pressure it would exert at the same temperature as the mixture if it alone occupied the volume that the mixture occupies.

Composition of the Atmosphere Nitrogen 78% of moleculesNitrogen 78% of molecules Oxygen, 21% of moleculesOxygen, 21% of molecules Argon, ~ 1% of moleculesArgon, ~ 1% of molecules Water vapor concentrations are variable, up to 4% of total Water vapor concentrations are variable, up to 4% of total Dry Air Total cannot be more than 100%; e.g. If water vapor is present, reduce proportion of dry air, as shown in calculations of molecular weight following

Composition of dry air Constituent Molecular Weight Fraction Product Nitrogen (N 2 ) Oxygen (O 2 ) Argon (A) Sum The average molecular weight of dry air ≈ 29

Composition of very moist air (4%) Constituent Molecular Weight Fraction Product Nitrogen (N 2 ) x Oxygen (O 2 ) x Water Vapor (H 2 O) Argon (A) x Sum The molecular weight of moist air is less than that for dry air for 4% water vapor vs

Radiosonde soundings from a variety of latitudes. P(mb) vs T(°C) Left trace is Dew Point Temperature (ignore) Right trace is Temperature Green lines are adiabats (neutral buoyancy) Pt. Barrow, AK 71.3°N Vandenberg AFB, CA 34.75°N Canal Zone 10.0°N

Pressure, Height,&Temperature of Tropopause Station Latitude P(mb) Ht(km) T(°C) T 250 Pt.Barrow Vandenberg Canal Zone

Local (OAK) 8/31 12Z sounding Balloon broke at 150 mb Display to 700 mb Note temperature inversion and rapid drop in moisture (top of fog layer) Conditions conducive to refraction of VHF/UHF radio waves Note lapse rate stable

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