Why is there is only a small difference in temperature between day and night, while the land experiences a much greater variation?

The temperature in the day time is comparatively higher than the temperature at night time. It is because during the day time, there is the presence of the clouds and the atmosphere is comprised of water vapor, that gets heated up when sunlight falls on earth. So the temperature increases. Whereas, during the night time, there occurs no cloud and no sunlight that can warm up the atmosphere. So the heat energy that was trapped in the day time is easily released into the outer atmosphere (space), thereby decreasing the temperature.

Due to this reason, there occurs a certain amount of temperature difference between the day and night.