由于黄赤交角的存在使得太阳直射点在南北回归线及其之间做回归运动,导致各地昼夜长短和正午太阳高度发生周年变化。而昼夜长短和正午太阳高度的周年变化是学习的难点,本文想通过图解的办法加以解决。 Due to the existence of the Yellow River Cross, the direct solar point makes a return movement between the TGR lines and between them, resulting in the annual variation of day-night and mid-day solar heights. The diurnal variation of day-night and mid-day solar altitudes is a learning challenge. This paper attempts to solve the problem by means of illustration.