The city of Lhasa, according to meteorological data, annual precipitation is greater than 400 millimeters, can not be described as arid, and can even be called wet, while Lhasa is known as the city of sunshine, sunny days but a lot. Look up the information found, Lhasa's sunny day and night rain, it is thanks to Tibet's unique topographic conditions. Because Tibet is full of plateau hillside, towns and cities are built in the river valley near the water source, Lhasa is located in the Lhasa River valley, on the Tibetan plateau, 24 small changes in temperature a day by the sun's radiant heat of the obvious influence, at the same time, due to the mountain slopes and river valleys of the altitude difference is large, at the same time, the temperature difference between different altitudes is also very obvious, the higher the altitude, the lower the temperature.
In Tibet during the tourist season, every morning the plateau is subjected to the local peculiar strong radiation of the scorching sun, the earth absorbs the radiant heat of the sun, the temperature is generally rising. After noon, the earth temperature rises to the peak, from the afternoon, the earth from the sun absorbed radiant heat gradually reduced, the earth heat dissipation speed gradually accelerated. At this time, the high altitude of the mountain slopes and highlands first began to cool down, and with the mountain slopes and highlands at the same altitude of the atmospheric temperature is also reduced. The air becomes colder, denser and heavier, and the weight of the air gradually decreases. The air at high altitude becomes colder and descends over the valley area at low altitude, while the warm moist air that was in the valley area is less dense and lighter in weight, and starts to rise under the pressure of the cold air that descends from the high slopes.
When the warm humid air continues to rise to a certain height, the moisture in the air begins to condense into countless tiny droplets suspended in the air, which is the cloud. The cold air on the high slopes continues to fall, the warm humid air in the river valley is constantly being lifted; the warm humid air continues to rise and condense small droplets of water, so the cloud thicker and thicker; condensation of more and more small droplets of water, they and each other, the droplets of water, the more and more large, and finally the rising air current can not support the more and more large droplets of water, these droplets can no longer be suspended in the air and fall, which is the rain.
From the high slopes of dry and cold air down, warm and moist air in the valley up, to the warm and moist air condensation into clouds, cumulus clouds into rain, is a long time process, usually from the afternoon, has been continued to the evening, to be down to the rain has been the night. A night rain is often the moisture in the sky all in the form of raindrops down to the next morning, and is cloudless, the sun shines brightly on a good day.
This kind of sunny and rainy weather due to the terrain of high slopes and river valleys with thousands of meters of elevation difference is mainly found in the summer tourist season in Tibet. This kind of tourism thanks to the plateau topography of the good weather not only in Lhasa, in Tibet built in the valley of the other towns and cities have, such as traveling to Shigatse, Tibet will also encounter this kind of sunny day and night rainy good weather.