Henan will welcome another round of persistent snowfall, with light snow, heavy snow and blizzard taking turns

The streets of Zhengzhou after the first snow in 2022

□ Dahe Bao Yu video reporter Liu Rui ChaoWen Bai Zhoufeng photography

Starting this night, Henan will face another snowfall drama. Compared with the first snow of the year, this snow is more persistent, and Henan will be one of the centers of this round of snowfall in the central and eastern parts of the continent.

Yesterday morning, the Henan Meteorological Observatory issued a blue warning for blizzard. Some people question that the amount of snowfall is only 5 mm, and dare to call it heavy snow? In fact, this is a confusion between the amount of snowfall and the depth of snow, and it is also related to everyone's stereotype of snow.

Predicting a blizzard warning came a day earlier than the snowfall

Before the continuous snowfall arrives, the blizzard warning comes first. This has also aroused the attention of the industry and the public, who are concerned about the meteorological department's rare release of blizzard warnings more than a day in advance.

According to the blizzard blue warning, from 20:00 on the 20th to 8:00 on the 22nd, the amount of snow north of the Yellow River and Sanmenxia, Luoyang, Zhengzhou, Kaifeng, Pingdingshan, Xuchang, Luohe, Nanyang Badi City and shangqiu, Zhoukou and Zhumadian cities in the western part of the city will reach more than 5 mm.

The Central Meteorological Observatory made a prediction in the early stage, from January 20 to 24, Henan is one of the main areas of snowfall, and the western part of Henan will usher in heavy snowfall, with a snowfall of 20 to 22 mm, a new snow depth of 5 to 10 cm, and a local area of 15 to 20 cm.

The occurrence of snowfall requires the cooperation of temperature, cold and heating currents. This cold air process, accompanied by strong wind cooling, henan's daily maximum temperature will fall to 0 °C, fully meeting the snowfall conditions. On the other hand, this time the warm and humid air flow is relatively abundant, the water vapor conditions are good, and the snowfall is still in a state of chaos.

Don't think about the depth of the snow as the amount of snowfall

Why does the snowfall of only 5 mm trigger the blizzard warning?

The reason for this doubt is that two concepts are confused: snowfall and snow depth.

A relevant person from the Zhengzhou Meteorological Observatory said that in meteorological observation, the amount of snowfall refers to the depth of the melted water accumulated on the horizontal plane.

The size of the snowfall is a measure measured by meteorological observers in millimeters, also known as precipitation, measured by the collected snow water after melting in a standard precipitation observation container (commonly known as a rain gauge).

The amount of snowfall is the amount of snow that melts. The depth of snow, which refers to the vertical depth of snow from the surface of the snow to the ground, refers to the depth (thickness) of the snow measured by the meteorologist in or near the observation field in or near the flat, open place, when the snow has not yet melted, measured, in centimeters.

The blue warning for blizzards is that precipitation will reach more than 50 mm within 12 hours, or it has reached more than 50 mm and the precipitation may continue.

In other words, a 5 mm amount of snowfall can create up to 10 cm of snow on flat ground, not taking into account other factors such as terrain accumulation.

In general, the amount of snowfall is proportional to the depth of the snow. According to observations and measurements by meteorologists, nationwide, 1 mm of snowfall, the snow depth can be up to 9 cm thick.

Another snowfall begins early next week

This round of snowfall, the main time period starts tonight. Today, the temperature in Henan quickly drops to the freezing point with the blowing of high winds, creating an atmosphere for snowfall.

According to the forecast of the Henan Meteorological Observatory, today's daytime, the province is cloudy, and there is light snow or sleet in some parts of the west and northwest. From this night to the 21st, the province is cloudy, with light rain or sleet in the southeast, and moderate to heavy snow in other areas, of which there is blizzard in the central and southwest parts.

On the 22nd, the province was cloudy, with light to moderate rain or sleet in the southeast, and light to moderate snow in other areas, of which there was heavy snow in parts of the central and southwestern regions. On the 23rd, the province was cloudy, with light rain in the southeast and light to moderate snow or sleet in other areas. On the 24th, the province was cloudy, with light rain or sleet in the southeast, and light snow or sleet in other parts. On the 25th, the province was cloudy, and most of the areas south of the Yellow River had small to moderate snow or sleet, of which there was moderate to heavy snow in the central and southwestern parts.

Specific to Zhengzhou City, although the overall intensity of the upcoming round of snowfall is not large, it lasts longer and the duration of low temperatures is also longer.

Among them, on Thursdays, Zhengzhou cloudy days, the northeast wind 3-4 turns 2-3, the temperature is -2 °C ~ 1 °C; on Friday, the cloudy day has moderate snow, the temperature is -2 °C ~ 0 °C; Saturday daytime, cloudy days have snow showers, at night, cloudy days have small to moderate snow, the temperature is -2 °C ~ 0 °C; On Sunday, there is light snow on cloudy days, the northeast wind 2-3 turns to the north wind 3-4 levels, the temperature is -1 ~ 1 °C;

Next Monday, continue to snow, Zhengzhou cloudy days have light snow, the temperature is -2 °C ~ 2 °C; On Tuesday, the cloudy day turns snow, the temperature is -4 °C ~ 2 °C; Wednesday, there are snow showers on cloudy days, the northeast wind is about 3, and the temperature is 0 °C ~ 3 °C.