Hurricane Ike:
- Upper level winds expanded when it entered the Gulf of Mexico
- Hurricane Warning over a large area of Texas and Louisiana coasts because of forecasting uncertainty
Announcements:
- HW #1 grades posted
- HW #2 posted, DUE: Tuesday, Sept. 23rd
- Old Exams from 07' posted under "Old Exams" menu button. Only guidelines for the type of questions, not the exact questions.
- EXAM 1: Thursday, Sept. 25th
Dew Point:
- Dew Point temp. does indicate the actual amount of water in the air
- When T and Td are far apart, RH is low and vice versa
- RH = U/Us, NOT T/Td
- Morning is when RH is the highest and is the best time to water plants
- Near the earth's surface the RH is relatively low
Condensation Near the Earth's Surface:
- Fog (Clouds close to the ground)
Dew & Frost:
- Dew: If the object is colder than the dew point temperature you end up with net condensation appearing on the object (your car)
- Frost: If the object is colder than the dew point and the object is lower than the point of freezing. Deposition: frost occurs from deposition, which is water vapor straight to ice, it skips the liquid stage
Example:
- Suppose Td = 40F
- Two cans, 1 is cold, 35F, 1 is warm, 45F
- The 35F can is cooler than the dew point, causing water vapor in the air surrounding it to condense onto the can forming liquid droplets of water on the outside of the can
- The 45F can is warmer than the dew point so no condensation occurs
T and Td:
- When T and Td are far apart in the early morning, RH is low
- When T and Td are close together in the afternoon, RH is higher
Energy Transfer:
- Warming required addition of energy
- Cooling requires removal of energy
- Energy always flows from the warmer object to the cooler object
Radiation:
= Transmission of energy through space or through a material in the form of electromagnetic waves
- All objects in the universe emit radiation
- Example: Rock in space - Rock is loosing energy by emitting radiation, the rock is also gaining energy by absorbing radiation from nearby stars
- The ground heats by absorbing more radiation than it emits during the day, until the afternoon when emitted radiation exceeds absorbed radiation as the sun sets
Conduction:
- Poor conductors are also known as heat insulators
Rate of Conductive Heat Transfer:
- Depends on temp differences between the two objects
- Conductivity of the material
Double-Paned Window Example:
- Air sandwiched between to layers of glass to slow conduction of air outside from air inside
Convection:
Dry Convection:
- Natural - warm air rising, cold air sinking (Thermal (rising parcels of air that birds and gliders can gain altitude with))
- Forced - Winds stir up the air, mixing it around. This partially explains why a fan can cool you...The fan blows the thin layer of air next to your skin which insulates you causing heat loss to occur at a faster rate
Moist Convection:
- Involves a phase change of water (Liquid water evaporating into water vapor, transferring the energy from the evaporation location (usually near the surface of the earth) to the condensation location (usually high in the atmosphere where clouds form))
- Energy is removed at the surface and added in the atmosphere where the cloud forms
Effects of the Wind:
- The rate of net evaporation rises when the wind blows the air near the surface away
Temperature, Humidity, Winds, & Human Comfort:
- Thermoregulation: the bodies process of balancing internal heat generation and external heat exchange so that it's core temp varies by no more than 2C from it's average of 37C. "Core" refers to vital organs, if the temp gets too far from 37C essential life functions do not work properly.
Response to cold core temperatures:
- Increase internal heat production by shivering (involuntarily muscle contractions)
- Reduce heat loss by vasoconstrictions (constrict blood vessels in outer extremities). Can lead to frost bite of extremities (freezing of skin).
Response to high core temperatures:
- Sweating - body is cooled by evaporation. By far the best way to loose heat, and the only means by which humans can live for long periods of time when the air temp exceeds body temp
- Increase heat loss by vasodialation (widening of blood vessels)
Hypothermia & Hyperthermia:
- Know definitions and what you can do for others suffering from these conditions
Influence of weather conditions on human body heat loss:
- In hot conditions and high humidity the rate of evaporation is slowed down by the high humidity
Heat Index:
- Not the temperature! In a way it's stating the rate of heat loss for a general human body
Wind Chill:
- Just a number! In a way it's stating the rate of heat loss for a general human body from exposed skin (wear clothes! Best is several layers of loose fitting clothing as the air trapped in between acts as an insulator)
- Wet clothing or skin will make the wind chill effect even worse
Clouds:
= A visible assembling of water droplets or ice crystals in the air
- May contain 3,000 droplets per cubic inch!
- Clouds are not water vapor, which is an invisible gas
- There must be a surface available for water vapor to condense on (Cloud Condensation Nuclei or microscopic aerosols)
- There is never a shortage of CCN
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