What is the reason for the resurgence?

"Moisture regain" is actually a natural phenomenon, which often occurs in the transition period from winter to spring. The main reason is the indoor and outdoor temperature difference. Due to the frequent cold air activity and relatively low temperature after winter, the indoor temperature is decreasing day by day due to the influence of cold air mass; After beginning of spring, the outdoor temperature rises faster than that indoors, but relatively speaking, indoors is the cold source. At this time, the warm and humid air mass in the south is more active, and the warm and humid air mass is rich in water vapor. When hot and humid air surges northward, which is often called "south wind day", it is blown indoors, and when it meets cold ground, walls, furniture and other utensils, its water vapor condenses into small drops, and even forms a flowing water layer, which is called "moisture regain" or "moisture regain". In particular, hard objects such as tiled floors, walls, painted furniture surfaces, mercury mirrors, aluminum alloy doors and windows are airtight, so water vapor is not easy to absorb or penetrate, and the phenomenon of "moisture regain" is more serious. At the turn of winter and spring in the south of the Yangtze River, there have been several "resurgence" weather processes.