North-south weather

We are in La Nina state this year, that is, the SST in the equatorial eastern Pacific is below 0.5 degrees below zero, which has a very obvious impact on China's climate. Under the influence of La Nina phenomenon, the meridional circulation in East Asia is abnormal, which is very beneficial to the southward movement of cold air in northern China. It has given us a cold winter, so we can see that this cold winter has already appeared this year.

The two conditions that must be met when it snows or rains are 1. It comes from warm and humid air currents in the tropics. There is cold air from high mountain area. The snowfall area in winter (the same as the rainfall area in summer) is distributed near the front, that is, the intersection of cold and warm air masses. This position is not fixed, but is determined by the strength of the two air masses. The cold air mass is weak, the front and precipitation areas have high latitudes, the cold air mass is strong, and the front and precipitation areas have low latitudes. The land cold high that affects China in winter is the Asian high centered on Mongolia and Siberia (also known as the Mongolian Siberian high), which has a very large sphere of influence and has a great impact on the weather in China, especially in the northern region. The cold air affecting our country in the early winter of this year is relatively weak, and the frequency is not much. Even with warm and humid airflow, it is not easy to snow without cold air. However, since 2008, the high pressure in Asia has been very active, and cold air masses have formed southward, affecting China and causing large-scale gale and cooling weather. However, due to the active warm air mass in the south this year, a large number of warm and humid air currents from the Pacific Ocean and the Indian Ocean frequently patronize the southern region. When the powerful cold air mass from Mongolia and Siberia quickly moved south to meet the warm and humid air mass, the cold and warm air just merged into one. Affected by these two air currents, there have been more rainy and snowy weather recently, especially in the Yangtze River basin, and the low temperature weather has lasted for a long time. If there is only a strong cold air mass without a large amount of water vapor provided by warm and humid air mass, there will only be strong winds and cool weather in the south; If there is only a large amount of water vapor provided by warm and humid air masses, there will be no disastrous weather at all without the arrival of cold air masses. When both are ready, disaster comes.

Many friends told me that the weather in the north has four distinct seasons, which puzzled me, because I really didn't find out how to embody this feature.

First of all: during my six-year experience in the north, I only found two seasons: winter and summer.

That is, about half a year in winter, from the middle of 10 to the middle of April the following year, the better time is actually summer. I wonder if the brothers in the north will have some opinions when they see this view.

Because I lived in the south since I was a child, I deeply felt this difference.

In the south, except winter, other seasons are very, very obvious.

Spring has come and everything is revived. You can see the green grass sprouting and the peach trees blooming. When you walk into the field, you will find that everything smells of spring.

The arrival of summer is more reflected in the sudden rise of temperature. Some summer fruits have begun to appear in the market, such as grapes, watermelons and, of course, green water pools, where green lotus leaves stand tall, making you feel that summer has begun. Pay attention to temperature changes to avoid heatstroke.

Autumn in the south is more meaningful. Leaves-urging, red maple leaves, Chengcheng Huang, sweet sugarcane, big grapefruit and delicious red dates all represent a bumper harvest in autumn. When I think of my childhood, my father will always show a better attitude and a happier mood in this season, because this is the moment when all the efforts in this year have been rewarded. At this time, I always get up early and work in the fields. Of course, others are as happy as my father, because many delicious foods have appeared. Hey hey.

With the arrival of harvest, winter comes quietly. In fact, winter in the south is not as obvious as that in the north. The thick snow makes people awake. The omen of winter in the south is the white entropy in the morning. Other temperature changes are not obvious, because it is only a few degrees below zero at most, and it seldom snows. It snowed in 1998, and many trees died. The rest is not obvious to me. When it snowed when I was a child, my brother always took me to sweep a small piece of snow, then put some white rice, tied it with a lid and a rope, a bit like Lu Xun at that time, and then waited for the sparrow to arrive.

If it snows a little in winter in the south, I think it will make people realize that the south is the real four seasons.