Atm Ocn 100 Exam 1 Study Guide Lectures 1 15 Chapter 1 and lecture Clouds A cloud is a mass of air containing suspended hydrometeors water of ice that act to reduce visibility and sometimes form precipitating water Fog is a cloud that is in contact with the surface If suspended particles are primary composed of a non water substance or air is not maintained at water or ice saturation the particles are referred to as Haze rather than a cloud What causes clouds to form Clouds form when an air parcel becomes saturated When the temperature is decreased saturation can occur through three processes radiation conduction or expansional cooling through rising motion Also a mix of parcels of 2 different temperatures can cause saturation which allows clouds to form There are 4 basic types of clouds Fogs Stratiform Cirrus and Cumulus Fogs Fogs are clouds in contact with the surface Different fogs as associated with different formation processes Radiation Fog Results from radiative cooling of a moist layer Advection Fog Results from moist air being advected over a cool surface Mixing Fogs Results from mixing of parcels at two different temperatures and humidities Upslope Fog Expansional Cooling of upslope flow Stratus Clouds Uniform layered cloud formed by stable lifting of air over large areas by large weather systems These types of clouds often cover the entire sky Cirrus Layered ice cloud often look wispy Cumulus Unstable clouds having vertical development These often result from warm moist rising as bubbles Cumulus Congestus Congestus have significant vertical development but no precipitation yet Cumulonimbus Visible precipitation darkened base anvil Stratocumulus Low level layered cloud with embedded vertical development Cirro Cumulus Typically appears as a large white and patchy or tuft without a gray shadow AltoCumulus Middle altitude It is usually white or grey and often occurs in sheets or patches with wavy rounded masses or rolls Altostratus thin high level stratus Mammatus Upside down convecting clouds usually on the underside of a cumulonimbus anvil Wall Cloud Appendage representing the updraft on the underside of a supercell thunderstorm Supercell Rotating Thunderstorm Lenticular Clouds Wave clouds Atmospheric Variables The atmosphere is primarily made up of by nitrogen and oxygen The Basic Variables are Temperature Pressure Density Humidity and Wind Temperature a measure of the average speed that molecules move in a substance In a solid molecules vibrate in place faster for higher temperatures and slower for lower temperatures In a liquid molecules remain in contact with one another but move freely about again faster for higher and slower for lower In the air individual molecules move around rapidly in random directions and bounce off each other The faster the average speed of the molecules the higher the temperature will be When substances with different temperatures come in contact energy associated with the vibration or movement of the molecules will be transferred from the substance with a higher temperature to the substance with a lower temperature So the average speed of the molecules will increase in the colder substance and decrease in the warmer substance If there is no energy transfer the substances are at the same temperature The ratio between heat stored to the temperature change and to the mass of a substance is heat capacity There are three temperature scales Fahrenheit Celsius and Kelvin Fahrenheit ranges between 0 to 100 degrees Celsius is based on the boiling point of water and the melting point of ice The boiling point of water at sea level pressure is 100 degrees Celsius The melting point of ice is 0 degrees Celsius Absolute zero or where zero is set at a minimum energy state is known as Kelvin Temperature conversations C F 32 1 8 K C 273 15 Temperature normally decreases rapidly upward away from the earth s surface The atmosphere can be divided into four layers Troposphere the layer of air in the lower atmosphere where temperature decreases with height This is where all weather that develops on earth occurs Stratosphere The layer of air above the troposphere where temperature increases with height The boundary between these two layers is called the tropopause The temperature increase with height occurs in the stratosphere because of the absorption of ultraviolet radiation by ozone in that layer This layer has a very important effect on the earth s weather The tropopause is higher in the tropics tropical storms grow to greater heights that storms that form in middle latitudes and Polar Regions Mesophere temperature again decreases with height The Mesosphere is above the Stratosphere Thermosphere temperature increases with height The Thermosphere is above the Mesophere There are two jetstreams that circle the globe The subtropical Jetstream and the polar Jetstream Tropopause folds are one way in which air in the stratosphere mixes with air in the troposphere Density the mass per unit volume of the air kg m3 Density is affected by Mass of each molecule The number of molecules Distance between molecules Density decreases with altitude Pressure the force per unit area exerted on a surface of random orientation by air molecules hitting that surface and reflecting off that surface Pressure is affected by The number of molecules hitting the surface and the average mass of the molecules is air density The speed of the molecules hitting the surface temperature Pressure is like the weight of a column of the atmosphere above a unit area of surface The higher the elevation of a particular location the lower atmospheric pressure that location will have Chicago for example is 600 ft above sea level which means that Chicago is a little closer to the top of the atmosphere than New York and so therefore it has fewer air molecules in its column Average atmospheric pressure at sea level is 1013 25 mb Pressure rapidly decreases as you move away from the earth s surface To observe the horizontal distribution of pressure meteorologists have to convert station pressure to a common altitude Normally this altitude is chosen as average sea level or mean sea level Then the conversion is made to see how pressure varies over a region Surface maps that depict pressure distributions use mean level pressure Humidity measure of the amount of water vapor in the air Absolute humidity is the amount of water in the air measured as Vapor density mass of vapor volume of air Vapor pressure amount