The temperature at the bottom of the water is 4 degrees Celsius in either winter or summer, why

Because at 4 degrees Celsius, the density of water is at its highest.

The formation of the ice surface prevents the heat exchange between water and air below the ice surface, and the freezing point is a temperature that can be mixed with ice and water, so it is normal.

When the cold winter comes, as the temperature drops, the water temperature in the rivers and lakes also drops. Consider a certain lake, let all the lake water be at a certain temperature such as 10 degrees Celsius, and then set the temperature of the air on the lake surface to be -10 degrees Celsius, then the water on the surface of the lake will become colder, for example, the temperature will drop to 9 degrees Celsius, this part of the water will shrink due to colding, and its density is greater than that of the warmer water below, so it sinks into the less dense water below, below.

10 degrees Celsius water rises. The sinking of the cold water causes a mixing process that continues until all the water in the lake has cooled to 4 degrees Celsius. However, the surface water will continue to be cooled and cooled by the cold air, and the temperature of the surface water will be further reduced, such as to 3 degrees Celsius, and the volume of this part of the water will not only not shrink but expand, that is, the density of the surface water is smaller than that below, so it will float on the water surface and no longer sink.

Both convection and mixing stop at this point (although diffusion does not), and the water beneath the surface essentially loses its internal energy by heat conduction. Water is a poor conductor of heat, so heat dissipation is slower. The temperature of the surface water drops to 0 degrees Celsius before the water below and begins to freeze.

Ice is less dense than water, so it floats on the surface of the water without sinking. The water underneath the ice, with a temperature of 0 degrees Celsius to 4 degrees Celsius from top to bottom, gradually freezes from top to bottom. The speed of freezing is slow due to the upward heat dissipation through heat conduction, and the geothermal heat conducts upwards from the bottom.

If the water in the lake is very deep, the water will not be frozen, and the animals and plants living in the lake can survive the winter in the 4 degrees Celsius water near the bottom of the lake, and avoid freezing to death.

The temperature is 4.

Bathymetry is the basic method of underwater topographic surveying. It is the basic means of hydrographic survey and seabed topography surveying to determine the plane position of each point on the bottom of the water and its clearance depth below the water surface.

Sounding instruments typically use sounding rods, thallium, echo sounders, multi-beam echo sounding systems, and submarine geomorphological sounders. The measured blind and positive depth under the instantaneous water surface can be calculated to the depth calculated from the depth datum after the sounder correction and water level correction.

Measurement preparation. Before measuring, it is necessary to determine the scope of the survey area and the scale of the survey.

Design the sheets, prepare the boards and map the control points, lay out the bathymetric lines and tide stations, and determine the location of the flow check points and hydrological stations. During the survey, the survey ship continuously measures the bathymetry along the predetermined bathymetric line, and positions it at certain intervals, and at the same time conducts water level observation.

During the survey, it is necessary to determine the exact location of various navigation obstacles such as reefs and shipwrecks, and to find out the shallowest water depth and its extension range. At the same time, a sediment survey is carried out, the flow velocity and direction are determined, and information such as water temperature and salinity are collected. After obtaining the original data of water depth, it is necessary to make various corrections, check the quality of the results, and finally draw up the results board.

On the surface of the water in the lake, when the temperature drops in winter, if the water temperature is above 4, the water in the upper layer cools, decreases in volume, becomes denser, and then sinks to the bottom, and the warm water in the lower layer rises to the upper layer. In this way, the cold water in the upper layer and the warm water in the lower layer are constantly swapped, and the overall water temperature gradually decreases. This phenomenon of thermal convection can only be carried out until the temperature of all water reaches 4 hours.

When the water temperature drops below 4, the water in the upper layer expands and decreases in density, so the cold water layer stays on top and continues to cool until the temperature drops to 0 and the upper cold water layer freezes.

The main form of heat exchange in the above stages is convection. When the surface of the water is frozen, the cooling of the water is completely dependent on the heat transfer of the water. Due to the poor thermal conductivity of the water, the water temperature at the bottom of the lake remains around 4.

This abnormal swelling of water ensures that the flora and fauna in the water can survive during the cold season. It should also be noted here that ice, when cooled, is the same as the general substance, and also shrinks. When heated, it expands, and only in the range of 0 to 4 does water show abnormal expansion.

1) Water itself is a poor conductor of heat; 2) The air humidity is close to saturation due to the low rain and temperature, so it is difficult for the water on the lake surface to evaporate, and it is difficult to take the lake away.

Normally, the surface temperature of the water is higher than the bottom temperature, and the greater the temperature difference in the water layer, the more difficult it is to fish. However, under special circumstances, the temperature difference of the water layer is reversed, the surface temperature of the water is lower than the bottom temperature, the dissolved oxygen content of the water body is greatly increased, and the fish are very active, and even bite the hook close to madness. The original heat is lost.

As a result, the lake still maintains its original water temperature of more than 20 degrees Celsius.

Gases and liquids with high temperature conform to the principle of thermal expansion and contraction, and the volume with high temperature will increase relatively and the density will be small, and of course they will float to it.

In summer, the water near the surface of the water is warmer than the water below because the temperature is high and the density is small. In winter, the water surface is colder than the water below.

Let's look at it separately. In deep waters, such as seawater and lake water, the surface temperature is especially higher than the underwater temperature in summer. In winter, the underwater temperature is higher than the surface temperature.

Why is the surface temperature warmer than the air temperature in summer?

The sun heats the ground first, and then the ground heats the atmosphere, so the temperature always rises and falls slower than the ground, and the temperature of the ground rises and falls faster, so the temperature difference of the ground is also larger, and the temperature of the atmosphere rises and falls slowly.

The water in the layer cools, shrinks in size, becomes denser, and then sinks to the bottom, while the warm water from the lower layer rises to the upper layer.

Because of the high temperature in summer, the density of water is not the same.

The water in the upper layer expands and decreases in density, so the cold water layer stays on top and continues to cool until the temperature drops to 0 and the upper cold water layer freezes.

The heat dissipation in the ocean is not good, and the seawater has the effect of heat preservation.

Liquids and gases have a characteristic, that is, the high density of the sinking bottom, the low density of the floating.

Gases and liquids with high temperature conform to the principle of thermal expansion and cold contraction, and the volume of high temperature is relatively large, and the density is small, and of course they will float to it.

The heat retention of seawater is relatively good, and there is a lot of salt.

It's a density temperature of water.

How many degrees Celsius is the temperature of the water flowing below the surface of a freshwater lake that freezes in winter like lead?

Correct Answer: a

At 0 4, the phenomenon of hot silver shrinkage and cold expansion of water is called abnormal expansion. At 0 at standard atmospheric pressure, water and ice can coexist.

The water density is highest at 4 degrees Celsius.

Under the ice, the water warms up "layer by layer" (1 degree Celsius, 2 degrees Celsius, 3 degrees Celsius.