How is ice formed?

The flowing ice is called ling. Sometimes ice and ice are universal, and there is no strict difference. When the temperature is lower than the water temperature in the river, the water body begins to dissipate heat. When the temperature continues to drop and the water temperature reaches and is slightly lower than zero degrees Celsius, rivers begin to freeze on the shore and in the water. River icing is freezing in flowing water, which is different from lake icing. The freezing of the lake is limited to the water surface, and the temperature of the deep water remains above zero degrees Celsius. Due to the chaotic mixing of water flow in the river, the heat loss of water body occurs almost simultaneously in the whole water body. Therefore, rivers not only form thin ice and shore ice on the water surface, but also form ice on the water and river bottom. The evolution process of river ice can be divided into two stages according to the increase or decrease of ice volume: ice formation and ice melting. From the beginning of icing to the maximum ice thickness, it is called the icing stage; In spring, from the beginning of ice melting to the end of river ice flow, it is called ice melting stage. According to the morphological changes of ice, it can be divided into three periods: freezing period, freezing period and thawing period. From the day when rivers begin to freeze to the day when ice flowers and ice cubes stop flowing, it is called the ice age; The period from the stop of ice flow to the beginning of melting of ice sheet is called freezing period. The period from the beginning of ice sheet melting to the end of ice flow is called thawing period. The main ice states and elements are as follows: (1) ice. Ice crystals floating on the water surface are fine needles or extremely thin sheets, which often gather into loose small pieces or balls in the flow. (2) slight icing. Transparent and fragile thin ice that often appears on the shore. (3) Shore ice. The frozen ice belt along the river bank. Due to different formation time and conditions, it can be divided into primary shore ice, fixed shore ice, alluvial shore ice, reclaimed shore ice and residual shore ice. (4) ice flowers. Ice, cotton ice and ice chips floating on the surface or in water. (5) Flowing ice flowers. The phenomenon that ice flowers flow with water. (6) Ice flow. Ice cubes or a small amount of ice cubes, ice flowers, etc. go with the water. (7) Frazier ice. Ice that exists anywhere below the water surface. (8) density. The ratio of the plane area of ice cubes and ice flowers to the open water area in the experimental reach. (9) The exposed water surface is wide. On the test section, the width of free water surface except shore ice is fixed. (10) ice sheet. A fixed layer of ice covering the water on both banks. (1 1) freezing and freezing date. When there is an ice sheet in the experimental reach and the exposed water surface area is less than 20% of the total reach, it is ice. The date when it begins to appear is the freezing date. (12) Snow depth on the ice. The thickness of undisturbed snow on the ice. (13) layer ice water. There is a layer of water in the center of the ice. (14) anchor ice. Ice frozen on buildings at the bottom of rivers or under water. (15) Ditching. An unfrozen long ditch in a river when it freezes. (16) The bottom is frozen. The whole section from the water surface to the bottom of the river is frozen into ice. (17) Ice jam. Due to the accumulation of a large number of ice flowers under the ice sheet, some water-crossing sections are blocked, resulting in the phenomenon of high upstream water level. (18) Ice dam. In the shallows, bayonets or bends of a river, ice bodies that cross the section and obviously return to the water level. (19) The ice melts on the shore. The frozen ice layer melts obviously from the shore, causing water accumulation on the ice surface or open water surface. (20) Ice slide. A phenomenon in which a complete or split frozen ice layer slides downstream for a certain distance and then stagnates. (2 1) thawing and thawing date. In the experimental reach, there is no ice sheet, or the exposed water surface area has exceeded 20% of the total area of the reach. Its start date is the thawing date. In a long river, there is an open water surface running from top to bottom, which is also commonly known as talking. (22) Residual ice accumulation. After thawing in spring, ice cubes piled up along the river bank. (23) Ice Age. The whole period of river icing. (24) Freezing period. The whole period of river freezing. Because of the different topography, the river type and water quantity change differently. Therefore, not all rivers will have the above ice evolution process. For example, in the lower reaches of the Yellow River, there are frequent cold air activities in some years, and the fluctuation range is also large at zero degrees Celsius. There can be many freezing and thawing processes in one winter. Another example is some sections of the upper reaches of the Yellow River and some rivers in Xinjiang, where the rivers are steep and fast-flowing, and only ice flows in winter without freezing. The factors affecting the change of river ice conditions can be summarized as heat, power and river characteristics. (1) Thermal factors: In the first case, the water body gains heat, such as direct radiation and scattered radiation from the sun, heat added by groundwater and heat generated by water flow. The second situation is the heat that makes the water lose, such as the effective inverse radiation of water surface or ice surface. The third situation is to make the water body gain heat under certain conditions and lose heat under another condition, such as losing heat during evaporation and gaining heat during condensation; Heat loss during snowfall and heat increase during rainfall; Heat exchange between atmosphere and water flow; Heat exchange between river bed and current, etc. For a reach, the total water and heat change per unit time can be calculated by the water and heat balance equation. Generally speaking, in the icing stage, water flow is a process of heat loss, and in the melting stage, water flow is a process of heat gain. (2) Dynamic factors: mainly including water level, discharge, velocity, wind direction, wind speed and waves. During the freezing period, under the same thermal conditions, if the flow rate is large, the flow speed is fast, the wind speed in the downstream direction is high, and the ice transport capacity of the water flow is strong, and it is difficult for the ice cubes to stand still, the freezing date can be postponed or even not frozen; On the contrary, it is easy to freeze. During the melting period, under the same thermal conditions, if the flow rate is large, the velocity is fast, the fluctuation difference is large, and the wind force in the downstream direction is strong, it is easy to form the "Wukai River"; On the other hand, it is easy to form "sloppy". (3) River characteristics: mainly including geographical location, river direction and river boundary conditions. Under the same thermal and dynamic conditions, some sections freeze first, some sections freeze later, some sections are easy to form ice plugs and ice dams, and some sections are not easy to form ice plugs and ice dams. Generally speaking, in places with sharp bends, many bends and many beaches, ice begins to freeze first, and it is easy to form ice dams when thawing.