Why does the weather get warmer and the subtropical precipitation decrease?

Will not decrease. For example, in summer, there is a low pressure control. When the air pressure is low, the air will flow upward, and the moisture in the air will condense into water in the troposphere and fall in the form of rain. Another important factor is temperature. As the weather gets warmer, the greater the evaporation of the earth, the more heat will rise, which will drive the air to rise. Therefore, rain in the tropics and subtropics is not common in the morning and evening, and there is no long rainy season in the temperate zone (the rainy season in the temperate zone is that warm air moves northward and meets cold air masses, and plum blossoms represent the high temperature season in summer). However, thunderstorms are more frequent in the afternoon. That's because at noon 12, the intensity of the sun is the largest and the evaporation is the largest, but the earth heating also needs a process, so the temperature generally reaches the highest point at two o'clock, and the evaporation is the largest at this time. After a period of convection, rain forms, so it usually rains around four o'clock in the tropics and subtropics.

So the weather is getting warmer, and there is still more precipitation in the subtropical zone, but it is still less than the rainy season in the temperate zone. They are all short-lived rainstorms.