Because lower clouds are much thicker, much of the solar energy is reflected back into space so less solar energy reaches the Earth's surface. High, thin cirrus clouds in the Earth's atmosphere act in a way similar to clear air because they are highly transparent, allowing most of the solar radiation to pass through.
Places closest to the equator do not see much variation in the length of daylight hours during all four seasons. The number of daylight hours decreases in the northern hemisphere during the fall and winter due to the tilt of the Earth and distance from the equator. More solar radiation is present at midday, when the Sun is directly overhead, meaning the Sun’s rays have a shorter path to get to the surface of the Earth and the energy is not scattered.
Different types of air pollutions (smog, smoke and volcanic ash) can limit the amount of solar radiation that reaches the Earth’s surface by up to 40%. More of the Sun’s direct light is scattered and have a larger impact on radiation coming in a direct line from the sun. In case of large volcanic eruptions, larger regions of the globe can experience decreased solar radiation for several months or years.