What does llj mean?

LLJ is the abbreviation of "low-level jet", and its scientific name is "low-level jet", which refers to a high-speed airflow phenomenon in the lower atmosphere.

Low-level jet usually occurs in the height range of about 5000 meters from the ground, and the speed can reach more than 50 kilometers per hour, sometimes even more than 100 kilometers per hour. This kind of high-speed airflow usually runs in the north-south direction or northwest-southeast direction, and exists at night or early morning, mostly in summer and winter.

The formation of low-level jet is related to many factors. The most important factor is the role of large-scale weather systems, such as fronts, high-pressure systems and low-pressure systems. These weather systems will produce horizontal gradient wind and form vertical shear in the atmosphere, which will lead to the rapid increase of wind speed. In addition, topography, boundary layer conditions, surface temperature and other factors will also have an impact on the formation and development of low-level jet.

Low-level jet is of great significance in meteorology. It has great influence on weather forecast, air quality and disaster weather. For example, the low-level jet on the front can strengthen the development and instability of the front and promote the formation of precipitation. In addition, the low-level jet will also affect the development and spread of fires or sandstorms.

In the aviation field, low-level jet is also one of the important considerations for flight safety. It will have an impact on the take-off and landing, cruising and landing stages of the aircraft, and may cause serious bumps, aircraft stall or abnormal flight attitude and other dangerous situations. Therefore, pilots and air traffic controllers need to pay close attention to the existence and change of low-level jet to ensure flight safety.

The difference between upper jet and lower jet.

High-altitude jet and low-altitude jet are two high-speed airflow phenomena in different altitude ranges. High-altitude jet generally refers to the strong airflow in the atmosphere or upper layer, which usually appears in the height range of more than 7000 meters. Low-level jet refers to the high-speed airflow in the lower atmosphere, which generally appears in the height range from the ground to 5000 meters.

The main difference between the two lies in the cause and scope of action. The upper jet is mainly influenced by large-scale weather systems and ocean currents, which has an important impact on aircraft navigation and weather changes. Low-level jet is mainly related to factors such as ground temperature distribution, topography and boundary layer conditions, and has an important impact on weather forecast, fire and aircraft take-off and landing.