Chapter 3: Temperature and Humidity Extremes

Which locale is warmer on a cold, clear night-the lowest elevation in a valley or the slopes of nearby hills?

-By night, modestly high hills and mountains are more commonly warmer than the valleys below, most notably when the sky is clear and winds are relatively calm. -That's because dense air chilled over higher terrain naturally drains down into the valleys like maple syrup rolling down a stack of pancakes onto your breakfast dish. Thus, the sloping terrain acts as a natural defense to damaging spring and autumn frosts by prompting cold air to drain down into the valleys. -slopes of nearby hills

Where on Earth would you expect to find the smallest annual temperature ranges?

-Daily temperatures - Extreme Cold -The coldest region of the continental U.S. is the northern Great Plains and northern Maine. -The coldest areas in North America are found in the Yukon and Northwest Territories of Canada. -The coldest area in the world is the Antarctic. -The average temperature for July (winter) is -74°F. -The mean annual temperature is -57°F. -EQUATOR, over water ** -The largest cold wave in modern recorded history in the U.S. was in February 1899 -Temperatures in this cold wave fell below 0ºF in every state in the union at that time, including Florida -Lowest temperatures and coldest winters in the Northern Hemisphere -Yakutsk, Russia= -46ºC, January average temp -Eismitte, Greenland= -53ºF, February average temp

Why does water take much longer to heat up and cool off than land does?

-Land adjacent to water heats differently -Cool air moving inland can cause the daily maximum to occur earlier than other places -Properties of soil, vegetation, and land use affect the rate of conduction from earth to atmosphere -Humidity, clouds, haze can lower maxima -Because of water's fluid molecular composition, it takes longer to heat and cool than land, which has a molecular structure that is more static and dense. Convective movements and the thermal capacities of bodies of water cause them to have a longer heat and cool time than land. -water absorbs the heat and spreads it out

When is the highest daily temperature usually observed and why?

-Past the middle of the day b/c the air continues to be heated, often reaching a maximum temperature later in the afternoon. -Between 3-5PM mid afternoon

What is a radiation temperature inversion, and under what conditions would you find a strong one, and on what time of day?

-Radiation Inversion is an increase in temperature with height due to radiational cooling of the earth's surface. Also called the nocturnal inversion. -A strong radiation inversion occurs when the air near the ground is much colder than the air higher up. Ideal conditions for a strong inversion, and, hence, very low nighttime temperatures exist when the air is calm, the night is long, and the air is fairly dry and cloud-free, winter

Where on Earth would you expect to find the largest annual temperature ranges?

-The hottest region in the US: desert Southwest, max July temperatures above 100°F. -In a more humid climate: max temperature rarely above 105°F. -Highest temp in U.S.=134ºF, Death Valley -Highest temp on Earth=136ºF, Libya -northern hemisphere @ high latitudes, Siberia , more dirty than waters ** -The hottest place in the world is Dallol, Ethiopia. -Average daily maximum temperature exceeded 100°F during every month of the year, except December and January. -Daily maximum often exceeds 120°F. -Average annual temperature 94°F.

What is hypothermia, and when are people more susceptible to it?

-The rapid loss of body heat may lower the body temperature below its normal level, and produce hypothermia -The rapid, progressive mental and physical collapse that accompanies the lowering of human body temp. -With advancing age, the body's ability to endure long periods of exposure to cold is lowered. -Hypothermia is caused by getting too cold, as the body loses more heat than it can generate and body temperature drops below 35C (95F). -Hypothermia is most common in cold environments. You're more at risk if you don't wear enough layers to keep warm or you don't cover your head (a large amount of body heat is lost through your head). -It's also possible to get hypothermia in mild weather. For example, if you're soaked in the rain and don't dry off properly soon afterwards - particularly if there's a cool wind - the water evaporates from your skin and lowers your body temperature. Cold wet days , body shuts down

How much of the Earth, at any given time, is illuminated by the Sun?

50%, Let's model the Earth and Sun as perfect spheres and ignore atmospheric distortions and reflections. Because the radius of the Sun is larger, more than 50% of the Earth's surface is illuminated by the Sun's surface. There are some simple approximations which can get you close to the right value.

Where are official temperature readings taken-in the air right above the surface, or a few meters above and why?

A few meters above the ground because a thermometer too low will pick up excess heat from the ground and a thermometer too high will likely have too cool of a temperature due to natural cooling aloft -measuring kinetic energy of convection

When is the lowest daily temperature usually observed and why?

Around sunrise -It's actually about an hour or two before sunrise for a couple of reasons. First, over night, all of the heat from the previous day has been radiating out into space. Second, when the sun hits the upper atmosphere before actually coming up over the horizon, it heats the upper atmosphere a bit, causing it to expand and press down on the air below it. This is colder air than what's on the surface of the earth and it flows down to the surface a bit, causing a period of slight cooling just before the sunrise.

Under what conditions would you expect a great temperature difference between the air right near the surface, and the air several meters above the surface?

Cold nights -As sun lowers, the angle causes insolation to be spread across a larger area -Darkness=no insolation -Radiational cooling occurs as infrared energy (long wave) is emitted by Earth's surface -Radiation inversion: air near ground much cooler than a few meters above. ---Ideal conditions for strong radiation inversions -Calm winds inhibit mixing of layers -Longer nights increase outgoing long wave radiation -Clear nights with dry air allow maximum amount of long wave radiation to go skyward -Conditions above can be enhanced by the presence of unusually cold air masses -If persistent, they can cause a freeze, which can lead to widespread crop damage -calm day

Who do deserts often have large daily temperature ranges?

Largest diurnal range of temperature occurs on high deserts b/c -Dry air, cloud-free, little water vapor , dry soil Clouds / humidity can have a large affect on the daily range in temperature. Cities near large bodies of water typically have smaller diurnal temperature ranges