why is the difference in solar receipt between 60N and 30N greater in the winter than in the summer?
What latitude experiences the smallest variation in insolation during the year? What explains this pattern?
At noon on the summer solstice, the sun's zenith angle is 37 deg at 60 latitude and 7 deg at 30 latitude. The noon solar irradiance has a ratio
cos 7/cos37 = 1.24, and the sun is up much longer at the more northern latitude. The net result is very little dfference in total sunshine (assuming no clouds).
At noon on the winter solstice, the sun has zenith angle at 83 degrees at 60 N and 53 degrees at 30 latitude. The noon solar irradiance ratio is cos 53/cos83 = 4.93, AND the sun is up longer at the lower latitude.
The net result is a much larger solar 'receipt' difference (also called "insolation" difference) in the winter.
The difference in solar receipt between 60N and 30N is greater in the winter than in the summer due to a combination of factors:
1. Axial Tilt: The Earth's axis is tilted by about 23.5 degrees relative to its orbit around the sun. In the winter, the North Pole is tilted away from the sun, causing sunlight to hit the Northern Hemisphere at a lower angle. This results in the sunlight being spread out over a larger area, leading to less intense solar radiation.
2. Path Length: In the winter, the Northern Hemisphere is tilted away from the sun, causing the sun's rays to travel a longer path through the Earth's atmosphere before reaching the surface. This longer path results in more scattering and absorption of solar radiation by the atmosphere, leading to a decrease in the amount of solar energy reaching the surface.
3. Day Length: In the winter, the Northern Hemisphere experiences shorter daylight hours compared to the summer. This means that there is less time for solar radiation to reach the surface, leading to a decrease in the total amount of solar energy received.
Combining these factors, the greater distance, lower solar angle, longer path length, and shorter daylight hours in the winter contribute to a larger difference in solar receipt between 60N and 30N in the winter compared to the summer.
The difference in solar receipt between 60°N and 30°N is greater in the winter than in the summer due to two primary factors: axial tilt and the path of the sun.
To understand why this happens, let's first consider the concept of axial tilt. Earth's axis is tilted relative to its orbit around the sun. This tilt is responsible for the change in seasons. During summer in the northern hemisphere, the North Pole is tilted towards the sun, resulting in longer daylight hours and more direct sunlight. Conversely, during winter, the North Pole is tilted away from the sun, leading to shorter days and sunlight that hits the Earth's surface at a shallower angle.
Now, let's consider the path of the sun. The sun follows a higher arc in the sky during the summer, meaning it rises higher above the horizon and remains visible for a longer period. This results in more direct sunlight, which is concentrated over a smaller area, leading to higher solar receipt. In contrast, during the winter, the sun follows a lower arc, rising and setting at a lower angle, which means the sunlight is spread over a larger area.
When we compare the latitudes 60°N and 30°N, we observe that the 60°N latitude lies closer to the North Pole and is therefore subject to more extreme changes in daylight hours and sun angle. Consequently, the difference in solar receipt between summer and winter is more pronounced at 60°N compared to 30°N.
In summary, the greater difference in solar receipt between 60°N and 30°N in winter than in summer is primarily due to Earth's axial tilt, which leads to shorter days and sunlight hitting the Earth's surface at a shallower angle during the winter season. Additionally, the path of the sun, which follows a lower arc during winter, spreads the sunlight over a larger area, further reducing solar receipt at higher latitudes.