Expert Interpretation of Typhoon "Kanu": Its Impact on Northeast China's Three Step Rainbelt | Typhoon | Kanu
Changchun, August 13th (Xinhua) - Typhoon Kanu on the 6th is the second typhoon to affect Northeast China this year. On the 13th, meteorological experts in Jilin Province provided a detailed interpretation of "Kanu" and pointed out that the impact of the typhoon on Northeast China can be divided into three steps.
Kanu is a long-lived typhoon with a lifespan of 15 days, a fluctuating path, and a span of over 4000 kilometers from north to south. On August 10th, it made landfall along the coast of Gyeongsangnam do, South Korea and continued to move in a northwesterly direction, gradually weakening in intensity. At 23:00 on August 11th, it weakened to a tropical depression and made landfall along the coast of Zhuanghe, Liaoning. It ceased numbering on August 12th.
Affected by it, from the early morning of August 10, Jilin Province experienced rainfall weather, with heavy to rainstorm and local heavy rainstorm in the east of Yanbian, and the maximum rainfall occurred at the easternmost end of Jilin Province - Hunchun Fangchuan 172.5 mm. Why is the typhoon located on the Korean Peninsula, but the precipitation is mainly in the northeast of Jilin Province?
Chen Changsheng, the director of Jilin Provincial Meteorological Observatory, said that this should start with the structure of typhoons. The typhoon is divided into typhoon eye area, cloud wall area, and spiral rain belt area from the center outward. The typhoon eye area is generally calm, the cloud wall area is stormy, and the spiral rain belt has several rainbands converging around the eye wall in a spiral shape. The rain band is tens to hundreds of kilometers long, and thousands of kilometers long. Rainy weather will occur where the rain belt passes.
"The overall 'image' of typhoons that usually move northward into the Northeast region is no longer so 'exquisite', and can be roughly divided into two parts: the main circulation of the typhoon and the peripheral circulation." Chen Changsheng said that when the typhoon is far away, the peripheral cloud system extends over and rainfall begins. For example, the rainfall in the eastern part of Yanbian was generated on the peripheral spiral rain belt of 'Kanu', which is the 'first step' of the typhoon's impact on the Northeast.
Chen Changsheng said that the "second step" of the typhoon's impact on Northeast China is the precipitation brought by the typhoon itself when the center of the typhoon approaches. In recent years, the most heavily affected typhoon body rainfall was in 2012 "Brawan" and 2020 "Mishak". The heavy rainfall of Typhoon "Kanu" mainly occurred on the Korean Peninsula, but was very weak in the Northeast region.
Chen Changsheng said that the "third step" of a typhoon's impact on Northeast China is the precipitation brought by its residual water vapor after the typhoon's landfall weakens or even disappears. At this time, there are usually "helpers" outside the typhoon. The heavy rainfall in the central and eastern parts of Northeast China on August 13 is caused by the interaction between the residual water vapor of "Kanu" and a "helper" called low vortex shear.
The precipitation of the typhoon "Kanu" is also implemented in three steps, but the precipitation brought by the typhoon itself is the weakest, which is very different from the storm storms brought to the southern region around the typhoon center. The reason should be explained from the cause of rainfall, especially rainstorm.
Hu Zhongming, chief forecaster of Jilin Meteorological Observatory, said that water vapor conditions and dynamic conditions are the two most important conditions for the formation of rainstorm. The main body of the typhoon entered the northeast, carrying enough moisture, but the circulation weakened rapidly in the constant "struggle" with the the Changbai Mountains. When it was near the northeast of China, it could not provide the dynamic conditions needed for rainstorm. There was no obvious rainfall, but it made people feel a little "muggy". The "helper" vortex shear on August 13 would bring the dynamic conditions to supplement the conditions needed for rainstorm.
Hu Zhongming said that if there is unstable energy during the rainfall process, "thunderstorms" will play the "main role", and even short-term strong winds, hail, or tornadoes may occur. Conversely, the rainfall process is relatively "quiet" and stable, which leads to the formation of "convective" rainfall, "stable" rainfall, and "mixed" rainfall. The unstable energy of Typhoon "Kanu" rainfall is insufficient, and it tends to be "stable".
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