Describe the change in duration of insolation from the Equator to the North Pole
A) In the winter
b) In the summer
c) on the Equinox
To describe the change in duration of insolation (the time during which the Sun's rays reach the Earth's surface) from the Equator to the North Pole in different seasons, we need to understand the axial tilt of the Earth and its effect on the angle at which sunlight reaches different latitudes.
a) In the winter: During winter in the Northern Hemisphere, the North Pole is tilted away from the Sun. This means that the Sun appears lower in the sky and its rays strike the Earth's surface at a shallower angle. As a result, the duration of insolation decreases from the Equator to the North Pole. Near the Equator, the Sun is higher in the sky, and hence, the duration of insolation is longer. As one moves towards the North Pole, the Sun appears lower, and thus, the duration of insolation decreases.
b) In the summer: During summer in the Northern Hemisphere, the North Pole is tilted towards the Sun. Therefore, the Sun appears higher in the sky, and its rays strike the Earth's surface at a steeper angle. As a result, the duration of insolation increases from the Equator to the North Pole. Close to the Equator, the Sun is still relatively high in the sky, resulting in a longer duration of insolation. As we move towards the North Pole, the Sun's position in the sky becomes more overhead, leading to a further increase in the duration of insolation.
c) On the Equinox: During the equinoxes (in March and September), the Earth's axis is not tilted towards or away from the Sun. As a result, the Sun appears directly overhead at the Equator on these days. This means that the duration of insolation is roughly equal at all latitudes, including the North Pole. On the equinoxes, day and night are approximately equal in length across the globe.
It's important to note that these explanations are based on the assumption of a perfectly spherical Earth and do not take into account other geographical and atmospheric factors that can influence insolation.