Why is the humidity in Hong Kong so high in spring?

Because both China and Hongkong are in the subtropical zone.

In spring, China and Hongkong are alternately affected by cold northerly/northeastern airflow and warm and humid easterly/southeastern airflow. Under the influence of cold air, the temperature of the ground/sea surface becomes lower. Once it turns to the southeast wind, the temperature of the warmer air drops after passing through the colder surface, so the relative humidity of the air increases. Because the relative humidity of warm air itself is not low, if it is increased, it will easily reach saturation (relative humidity 100%), and the water vapor in the air will condense into water points and float in the air. So, we feel very good. The floating of the above water points will form fog, which is called advection fog. Another common situation is that when cold and warm air meet, warm air in contact with cold air will also become saturated due to temperature drop and relative humidity increase, forming water spots floating in the air. The fog formed by these floating water spots is called frontal fog.

Extremely hot index In hot and humid days, we are bound to feel uncomfortable all over. Uncomfortable, of course, because of the high temperature; But the reason why we feel uncomfortable is not only high temperature, but also high humidity. We know that one of the heat dissipation mechanisms of the human body is sweating-when the temperature is high and the humidity is low, the sweat discharged by the human body will be evaporated rapidly; On the contrary, in the case of high temperature and high humidity, the evaporation rate of human sweat will be much slower. Because evaporation consumes heat energy, the purpose of sweating is to promote evaporation, and then consume the heat energy of our body and make us feel cool. But in hot and humid weather, the heat dissipation mechanism of human body will be affected. Because the evaporation of sweat will slow down due to high humidity, the excessive heat energy of the human body cannot be effectively taken away from the perspiration process. Problems such as heatstroke, cramps and heat exhaustion may occur at any time. However, under general meteorological conditions, people's body temperature regulation will be hindered: the temperature is 40℃ and the relative humidity is 30%; The temperature is 38℃ and the relative humidity is 50%. The temperature is 30-3 1℃ and the relative humidity is 85%. Because we know that humidity will affect the temperature our bodies feel, the National Weather Service of the United States took the lead in introducing the extreme heat index-1984 human body temperature index considering both temperature and humidity in summer. The extreme heat index (centigrade) can be obtained by the following formula: (-42.379+2.04901523 * (t)+10.1433127 * (RH)-0.224754. -5.48 17 17 * 10-2 *(rh2)+ 1.22874 * 10-3 *(T2)(RH)+8.5282 * 10-。 9/5+32 RH= relative humidity (%) It should be noted that this index can only be used as a reference, because different people have different degrees of adaptation to heat. For example, some people will feel very tired in the environment of 3 1 degree Celsius and 70% humidity, while others will not. Moreover, wind speed, labor intensity, exposure time in high temperature environment, physical strength, water supply and health status will also affect people's reaction to high temperature. Therefore, when the weather is hot and humid, as long as you remember to drink more water, wear some loose or breathable clothes and avoid outdoor exposure, there will basically be no big problem. Weather/study/heat and cold

Reference: Weather/Study/Hot and Cold