What Is Advection Fog?

Advection fog (advection fog) is a fog formed when warm and humid air flows advancing to the colder surface and the lower part cools. It mostly occurs in the winter and spring seasons. Most of the northern coastal areas can twist buildings in the city, so that people on the ground feel like a fairyland.

First, there is a large temperature difference between warm and humid air and the ground;

1.Analysis advection

1. The day-to-day change is not significant, it can occur at any time of the day, and the conditions can be maintained all day long. Annual changes are more obvious (more in spring and summer, less in autumn and winter), seasonal changes in sea-land temperature differences and cold and warm ocean currents;

2. Advection fog at sea lasts for a long time, sometimes it can last for several days. Advection radiation fog is often used on land, that is, warm and wet advection followed by radiative cooling;

3. The vertical thickness of advection fog can be from tens of meters to two kilometers, and the horizontal range can reach hundreds of kilometers or more. The intensity of advection fog is also greater than that of radiation fog;

4. Advection fog is often accompanied by weather phenomena such as stratum clouds, broken rain clouds and drizzle. The weather is generally stable.

5. Advection fog occurs mostly at sea and on the coast; advection fog on the continent is rarely a simple advection fog, but is caused by both advection and radiation, so it is generally called

1. Weather method

Advection fog is formed by low-level warm and humid air moving to the cold sea under certain weather conditions. Sea surface thermal conditions change little within the time frame of short-term forecasting and can be considered steady. So for short-term forecast, whether the weather conditions are favorable is the main factor that can produce advection fog. Therefore, as long as the future weather situation is predicted, and then other indicators are referred to, a judgment can be made as to whether there is advection fog in the future.

2.Forecasting method combining dynamics and statistics

The station's timed observation data is used, and the numerical forecast output data and weather map data are used as historical data. After statistical analysis, a forecast equation is established, and then the numerical input atmospheric data according to the desired forecast period is substituted into the forecast equation to make a forecast. In recent years, the combination of numerical and statistical forecasting has become a statistical dynamic forecast, which has achieved relatively obvious results.

3. Comprehensive forecasting method

Due to the many factors to be considered in the prediction of advection fog on the sea and the different local influencing factors are different, as far as the current forecast is concerned, there is no effective and widely applicable forecasting model. However, with the rapid development of computer technology and satellite remote sensing technology, comprehensive and direct observation of the atmosphere of a certain region from space through meteorological satellites, satellite cloud image data plays an extremely important role. At present, meteorological satellite cloud maps have become an indispensable tool in weather forecasting operations.

Relevant research shows that when the average wind speed in the coastal area is 1--7 m / sl, there is a southwestern warm and humid airflow, the relative humidity obviously increases, and the high humidity state is maintained. The K index is between 20-30.c; When strong inversion is stratified, it is necessary to consider whether to issue an early warning of sea fog. Especially in the late winter and early spring season, coastal areas are affected by weak cold air. The northerly wind near the ground, and the two lower layers are southwestern airflow. The air in Yemin is at or near saturation, and there is an inverse humidity in the boundary layer of the offshore surface. As long as the sea temperature difference is moderate, fog is easy to form at sea.

1. Advection fog in the cold and high-pressure west of the sea

After the cold and high pressure enters the sea, whether advection fog can form in the west depends mainly on the system.

Typical multi-advection fog cities in China

The beauty of advection fog flowing through Long Island (23 photos)

Due to the unique urban terrain, Qingdao has a lot of foggy weather, especially advection fog and radiation fog. For example, on March 26, 2014, dense fog shrouded Qingdao, overlooking high-rise buildings, only the top of high-rise buildings exposed clouds, a dreamy color. However, while the mist creates beautiful scenery, it is also harmful. When it appears, a series of physical and chemical reactions may occur in the toxic, harmful substances and atmospheric pollutants in the air, resulting in new toxic and harmful substances. ^[4]

On the morning of November 29, 2018, the rare advection fog landscape appeared on both banks of the Red Water River in the county town of Dahua Yao Autonomous County, Hechi City, Guangxi. Overlooking Dahua County from the air, the entire county town appeared looming in the foggy sea against the background of the rising sun wonderland. ^[2]