Chapter 3 : temperature

what is the difference between a windward and leeward coast, and how does each affect temperature?

Windward coasts receive winds blowing in from the ocean. They are moderate by the ocean’s high specific heat and experience cooler more stable temperatures. Leeward coasts receive winds from land they are more variable and extreme.

• Examples: Eureka, CA (windward) vs. NYC (leeward inland air)

Why do isotherms generally run in an east-west direction on global temperature maps?

because latitude is the primary control on temperature locations at the same latitude receive similar solar radiation and therefore have similar temperatures.

• sun angles and daylight hours are latitude dependent.

what is temperature a measure of?

the average kinetic energy of molecules in a substance it depends on both the mass and velocity of the molecules.

• higher temp = faster- moving molecules

what is normal human body temperature in both Celsius and Fahrenheit?

• 37*C and 98.6*F

• a useful anchor for comparing the two scales

what is the heat stress index? (heat index)

The apparent temperature felt by the human body when both heat and humidity are factored in. High humidity prevents sweat from evaporating, which is the body’s main cooling mechanism, making hot days feel even more hotter.

• humid air = sweat can’t evaporate = body cannot cool.

What is a temperature anomaly?

a deviation from the norm. The ‘normal’ reference is typically the average temperature over 30 years, but can be defined differently depending on the scientific question.

• norm = 30 year average

how do ocean currents affect temperature at mid and high latitudes vs. the tropics?

warm currents on the eastern side of the continents make mid to high latitude coastal areas warmer than expected. Cold currents on the western sides make tropical/subtropical regions cooler than expected.

• eastern coast = warm current

• western coast = cold current

what is a temperature gradient and what do closely spaced isotherms indicate?

Temperature gradient is the change in temperature over a change in distance. Closely spaced isotherms indicate a large (steep) temperature gradient temperature changes rapidly over a short distance.

• so think of it like slope steepness on a hill.

what is the main limitation of satellite temperature sensing?

clouds block certain infrared bands making temperature data unrepeatable in regions with dense cloud cover.

• clouds interfere with IR signals.

what energy balance condition produced the daily temperature maximum and minimum?

Max temperature occurs when incoming solar (SW) radiation equals Earth’s outgoing long wave (LW) radiation in the evening. Min temperature occurs when SW = LW in the morning (just before sunrise).

• when SW = LW, the energy balance is at a tipping point.

what are the 3 main patterns of annual global temperature variation?

1) More variation over land than over water

2) more variation in the Northern Hemisphere than the Southern

3) More variation father from the equator.

• land N. Hemisphere and high latitudes = most variable.

How does latitude control temperature variation?

farther from the equator, temperature variation increases. Tropical locations experiences 2 peaks of solar radiation and temperature per year, while polar regions experience extreme seasonal swings.

• Equation = stable

• Poles = extreme swings

How does a liquid in glass thermometer work?

it uses the principle that density changes with temperature. As temperature rises, liquid volume increases, causing the fluid to rise in the tube.

• Temp ↑ → Volume ↑ → Fluid rises.

what are the 3 temperature scales and what is each based on?

Fahrenheit (roughly based on average human body temperature)

Celsius (based on properties of water, used globally in science)

Kelvin ( absolute scale directly tied to molecular movement)

• Kevlin is the ONLY absolute scale.

What are the 7 major temperature controls?

Latitude, specific heat (differential heating of land vs. water), ocean currents, altitude, prevailing winds (geographic position), topography and albedo.

what is the difference between zonal and meridional temperature changes?

zonal refers to temperature changes in the east west direction ( along lines of longitude). MerIdional refers to north south changes (along lines of latitude).

• latitude differences drive meridional changes.

why does maximum air temperature typically occur between 2-4 PM rather than at solar noon?

Maximum sun angle (and thus peak solar input) occurs at noon, but the surface continues to absorb more incoming shortwave radiation than it emits longwave radiation until mid afternoon so temperature keeps rising after noon.

• energy balance: max temp when SW in = LW out.

what is the wind chill index?

the apparent temperature due to wind speed. Wind enhances evaporation and removes the thin layer of warm air near the skin, replacing it with colder air making the air feel colder than the actual temeprature.

• wind = accelerated heat loss from skin.

What is absolute zero on the Kelvin Scale and what does it mean?

0 K.

• the theoretical point at which there is no molecular movement at all

• nothing can be colder than 0 k.

what is specific heat and how does it differ between land and water?

specific heat is energy required to change the temperature of 1 gram of a substance by 1*C. Water has a higher specific heat than land, so it heats and cools more slowly.

• water is thermal buffer

• land is NOT.

What is remote sensing of temperature?

Measuring temperature without physical contact with the object, typically using Earth observing satellites that detect infrared radiation emitted from the surface.

• satellites measure IR from space.

What is the urban heat island (UHI) effect?

Urban areas are generally warmer than surrounding rural areas due to factors like dark pavement, buildings, waste heat from vehicles and industry and reduced vegetation.

• so like Atlanta the city center notably warmer than surburbs.

How does a mercury thermometer work?

liquid mercury expands when temperature rises and contracts when temperature falls. The volume change in mercury column indicates the temperature.

• Mercury = Hg on the periodic table.

what is the albedo and how does it affect temperature?

Albedo is the fraction of radiation reflected by a surface. High albedo surfaces (snow, ice clouds) reflect more radiation and stay cooler. Low albedo surfaces (dark soil, asphalt, ocean) absorb more radiation and warm up more.

• high albedo = high reflectivity = cooler.

what is thermocouple and what principle does it use?

an industrial thermometer that used the Seebeck effect.

• when two dissimilar metal conductors are joined, temperature changes produce a proportional electrical current.

How do clouds affect temperature on a daily basis?

Clouds decrease direct solar radiation reaching the surface but increase diffuse radiation. Overall, cloudy days have more moderate temperature ranges than clear days and cloudy months can reduce the total solar radiation at the surface.

• diffuse radiation is lower energy than direct radiation.

How does an electronic (thermistor) thermometer work?

a thermistor changes its electrical resistance when temperature changes. A computer measure the resistance and converts it to a temperature reading.

• ‘thermistor’ = thermal resistor.

How does altitude affect temperature?

temperature decreases as altitude increases in the troposphere, at the environmental lapse rate of -6.5*C per 1 km of ascent.

How does an infrared thermometer measure temperature?

it detects the thermal infrared radiation emitted by an object without physical contact, converting that radiation into a temperature reading.

• no contact needed. Used for measuring people or surfaces.

What are isotherms?

lines on a map connecting points of equal temperature.

• ‘iso’ = equal

• ‘therm’ = temperature

How do scientists work around cloud interference in satellite temperature measurements?

They use specific wavelengths (eg, 3.7 and ~10 micrometers) that are less affected by cloudiness, allowing measurements even in partially cloudy conditions.

• Not all IR wavelengths are equally blocked.

Under what conditions is the urban heat island effect strongest vs. weakest?

strongest on clear winter nights. The temperature difference can be up 20*F. On overcast winter nights, the effect nearly disappears because clouds trap heat in rural areas too.

• clouds equalize temperature between urban and rural.

How does differential heating of land and water affect temperature at nearby locations?

Land heats up and cools off more rapidly and to more extreme temperatures than water. Coastal locations near water have more moderate, less variable temperatures than inland locations at the same latitude.

• Example: Vancouver (costal) vs. Winnipeg (inland).

How do mountains create temperature and climate differences on their two sides?

the windward side is cool and moist. The leeward side (rain shadow side) is warm, dry and has more temperature variation.

• leeward = drier and warmer after air descends.

What effects do warm vs cold ocean currents have on perception?

warm currents primarily bring more moisture to regions to regions than cold currents.

• warm water → more evaporation → more moisture.

Why does the northern hemisphere have greater temperature variation than the Southern Hemisphere?

the northern hemisphere has more landmass, which heats and cools faster than ocean water. The Southern Hemisphere is dominated by oceans, which moderates temperature.

• more land = more temperature swings.

When does minimum temperature typically occur?

just before sunrise this is when Earth has been losing heat all night with no solar input reaching its lowest point before the sun rises again.

• all night radiative cooling → coldest at dawn