Why does it rain all night in Lhasa?

Last week, I reviewed the Qinghai-Tibet region of China's regional geography, and found that Lhasa is very interesting, because it is called the Sunshine City, but it is not the season with the most sunshine in summer. People who have been to Tibet before will think that Lhasa is sunny in the daytime and cloudless in Wan Li, but it rains heavily at night. The next day, it was still sunny during the day and rainy at night. This should be the manifestation of the Buddha. In order to take care of the pilgrims and tourists who took pains to reach the plateau, they can see the true face of Lhasa and gain a happy mood. The Buddha generally exists in the hearts of people with faith, and I prefer to look for it from a geographical perspective. According to meteorological data, the annual precipitation in Lhasa is more than 4 mm, which is not a drought. It can even be called wet. At the same time, Lhasa is known as the sunshine city, but there are many sunny days. Looking up the data, it is found that the sunny nights and rainy nights in Lhasa are due to the unique terrain conditions in Tibet. Because Tibet is full of plateau hillsides and towns are built in river valleys near water sources, Lhasa is located in the Lhasa River Valley. On the Tibetan Plateau, the temperature change of 24 hours a day is obviously affected by the radiation heat of sunlight. At the same time, due to the large altitude difference between the hillside and the valley, the temperature difference at different altitudes at the same time is also very obvious. The higher the altitude, the lower the temperature. During the tourist season in Tibet, the plateau is strongly radiated by the local scorching sun every morning, and the earth absorbs the radiant heat of the sun, and the temperature is generally rising. After noon, the temperature of the earth rose to the peak. From the afternoon, the radiant heat absorbed by the earth from the sun gradually decreased, and the heat dissipation rate of the earth gradually accelerated. At this time, the hillside highlands with high altitude first began to cool down, and the atmospheric temperature at the same altitude as the hillside highlands also decreased. The air became cold, the density increased, the weight of the air became heavy and gradually decreased. The air at high altitude cools down and falls over the valley area at low altitude, while the warm and humid air in the valley area is low in density and light in weight, and begins to rise under the extrusion of the cold air falling from the high slope. When the warm and humid air rises to a certain height, the water in the air begins to condense into countless tiny water droplets suspended in the air, which is the cloud. The cold air on the high slope is falling continuously, and the warm and humid air in the valley is being lifted continuously; Warm and humid air keeps rising and condensing into small water droplets, so the clouds accumulate thicker and thicker; More and more small water droplets are condensed, and they converge with each other, and the water droplets are getting bigger and bigger. Finally, the rising airflow can't hold the bigger and bigger water droplets, and these water droplets can no longer be suspended in the air and fall down, so it began to rain. It takes a long time from the dry cold air on the high slope to the warm and humid air in the valley, to the condensation of the warm and humid air into clouds and the accumulation of clouds into rain. Generally, it starts in the afternoon and lasts until the night, when it rains, it is already night. A rainy night often drops all the water in the sky in the form of raindrops. Until the next morning, it is cloudless and sunny in Wan Li. This kind of sunny and rainy weather, which is determined by the topography of high slopes and valleys with an altitude difference of several thousand meters, mainly appears in the golden season of tourism in Tibet in summer. This kind of good tourist weather, which benefits from the plateau topography, is not only found in Lhasa, but also in other towns built in river valleys in Tibet. If you travel to Shigatse, Tibet, you will also encounter this kind of fine weather with sunny days and rainy nights.