Sichuan is located inland, why is the precipitation much higher than other western provinces and cities?
Why are there waves of heavy rain?
The high latitude circulation in the subtropical high is blocked.
Since the end of June, the rainstorm has come to our province once a week, and it has been down to the west of the basin, and the earthquake-stricken areas have been soaked almost every time. Some netizens asked: how to pick a place to rain? In fact, this is also a "coincidence" caused by the configuration of the weather system. Yesterday, Ma Li, deputy director of the Provincial Meteorological Bureau, and Lu, chief forecaster of the Provincial Meteorological Observatory, answered this question.
The biggest reason is that this year's subtropical high is abnormally north-west and stable and inactive. Ma Li said: "This year is very unusual. In June, the subtropical high reached the western part of the basin, and the high temperature in eastern Sichuan continued, so the weather in July last year began in western Sichuan. In July, our current subtropical high position was stable and did not move much, which caused the rain belt to stay and stay still, so the precipitation in the western part of the basin along the mountain and the western part of the basin was particularly strong. "
In addition, the circulation anomaly in the middle and high latitudes of Asia. The zonal circulation, which was originally prevalent, has a small meridional scale, which leads to the gentle westerly airflow on the Qinghai-Tibet Plateau and the eastward movement of the plateau short-wave low-value rainfall system. When it moved eastward to the west of the basin in our province, the subtropical high blocked its way like a wall, and it could only rain in the west of the basin.
In addition, the transport of water vapor is also very important for rainfall. This year, the warm air in the south is strong, and the water vapor and heat in the Bay of Bengal and the South China Sea are continuously transported to the west of the basin, which makes the heavy rainfall always supplemented by water vapor, and it turns from a rainstorm to a persistent rainstorm. The cold air in the north is weak and moves slowly after entering our province, which prolongs the duration of heavy precipitation.
The rainy night in the west of the basin is due to the influence of topography, and the rainstorm process also needs the participation of topography. Lu said that the western part of the basin is located on the eastern slope of the Qinghai-Tibet Plateau, and the Longmenshan fault zone is quasi-north-south. The strong warm and humid air flow from south to north turned west in the middle of the basin, orthogonal to the Longmenshan fault zone in the north-south direction, and was forced to rise after being blocked, thus increasing the magnitude of heavy rain. July 10 Dujiangyan torrential rain is a typical example.