Because the sun is lower in the sky in northern latitudes than in middle latitudes the insolation, or amount of radiation reaching the ground is less at more northern latitudes than at lower latitudes even though more radiant energy reaches the top of the atmosphere at higher latitudes. This is so because the incoming radiation, at the more northern latitudes, must traverse a longer path in the air, because the summer skies at northern latitudes tend to be cloudier than at middle latitudes, and because, at extreme northern latitudes, much incoming radiation is reflected off ice and snow and that which does reach the ground often melts ice and snow or evaporates water rather than raising the temperature.
3-QR11. Explain why the warmest time of the day is usually in the afternoon, even though the sun's rays are most direct at noon.
Even though the rate at which radiant energy reaches the ground is maximum at mid-day, the temperature rises until the rate of energy loss from the ground rises to equal the rate at which energy is absorbed. That condition usually does not occur until several hours after noon.
3-QR18. Look at Fig. 3.21 (temperature map for January) and explain why the isotherms dip southward (equatorward) over the Northern Hemisphere continents.
Because land has a much smaller specific heat than water, and because circulation cannot bring heat to a cooling land surface as it can in water, both annual and daily temperature variations are considerable greater over land than over water. In particular winter temperatures are lower over land than over water at a comparable latitude, especially over large land bodies such as continents. This lower winter temperature over continents, versus oceans at the same latitude, is the physical explanation for the southward dipping of isotherms over northern continents during the northern winter.
3-QT2. Consider these two scenarios: (a) The tilt of the Earth decreased to 10°. (b) The tilt of the Earth increased to 40°. How would this change the summer and winter temperatures in your area? Explain using a diagram.
(a)/(b) Since the sun's north-south range of angular motion in the sky would be reduced/increased from 47° to 20°/80° there would be far less/more difference in both the angle of the sun and the length of the day between summer and winter. As a consequence seasonal effects would be much smaller/greater. Winters would be considerably warmer/colder and summers considerably cooler/hotter than at present. There would probably be little change in the mean annual temperature. The figure at the right illustrates both scenarios. Of the six lines extending skyward from Provo, the inner pair represents the range in the direction of the noon sun for a 10° tilt, the next pair outward represents the actual range in the direction of the noon sun and the outermost pair represents the noon sun range for a 40° tilt. These lines are parallel to six lines intersecting the earth, showing the range in those latitudes on the earth’s surface, above which the noon sun would stand, for each of the three tilts considered.
3-QT9. On a warm summer day, one city experienced a daily range of 22°C (40°F), while another had a daily range of 10°C (18°F). One of these cities is located in New Jersey and the other in New Mexico. Which location most likely had the higher daily range, and which one had the smaller? Explain.
Most likely the larger range was in New Mexico and the smaller in New Jersey. This is so because the conditions in New Mexico favor the larger temperature range. These conditions include higher altitude, lower humidity, and the probability of less cloud cover.
3-PE6.
What is the wind-chill factor when the air temperature is 5°F and the wind speed is 35 mi/hr? (Use Table 3.3, p.77.)F (-29°C).Referring to Table 3.3, Twind-chill equivalent= -21°