Method for determining density of new snow

Abstract

The invention discloses a new snow density determination method considering surface temperature and relative humidity. According to the method, on the basis that only the air temperature and the wind speed are considered in a traditional new snow density determination method, the influence of the surface temperature and the relative humidity on the new snow density is added, and the problem that the new snow density determination error is too large in some specific scenes in a traditional method is solved. The new snow density obtained by the method is more scientific and accurate than that obtained by a traditional method, and prediction and emergency management of the accumulated snow density and the accumulated snow depth by a management department are facilitated.

Description

Technical Field

[0001] The present invention relates to the intersection of geography, meteorology and physics, and in particular to a method for determining the density of new snow, and more particularly to a method for determining the density of new snow taking into account the surface temperature and relative humidity. Background Art

[0002] Under the condition of certain precipitation, the depth of snow accumulation is determined by the snow density, and the snow depth is one of the most important indicators to determine whether a snow disaster will occur. Therefore, it is necessary to simulate and determine the snow density in order to make more scientific and reliable early warning and prediction of snow depth and snow disasters.

[0003] Snow density is mainly determined by the shape and size of snow particles. The shapes of snow particles can be roughly divided into disk, needle, column, star and branch shapes, and the resulting snow density changes from large to small. The shape of snow particles is mainly determined by the temperature in the cloud layer. The temperature required to form disk, needle, column, star and branch shapes is roughly distributed from high to low. In the process of falling from the cloud layer to the ground, snow particles are affected by the temperature and humidity of the surrounding environment, and they will sublimate and melt, and the shape of snow particles will also adjust accordingly. After the snow particles fall to the ground, they are affected by the compaction of wind and the surface temperature, and the snow density will also change. Since it is difficult to obtain high-altitude meteorological data, the existing snow density parameterization method only considers the statistical relationship between temperature and wind speed and snow density, but ignores the effects of relative humidity on snow particle sublimation and warm season surface temperature on snow particle melting. These factors will cause large deviations in the snow density estimation in certain climate scenarios. Summary of the invention

[0004] The purpose of the present invention is to propose a method for determining the density of new snow taking into account the surface temperature and relative humidity. This method adds the influence of relative humidity and surface temperature on the density of new snow on the basis of the statistical relationship between air temperature, wind speed and density of new snow established by the existing method, thereby being able to more accurately estimate the density of new snow.

[0005] A method for determining the density of fresh snow taking into account the surface temperature and relative humidity of the present invention comprises the following steps:

[0006] Step 1: Determine the mean value of each meteorological element during snowfall.

[0007] Based on the hourly meteorological observation data, the observed values ​​of air temperature, wind speed, relative humidity and surface temperature during snowfall were obtained and standardized.

[0008] Step 2: Determine the effect of wind speed on the density of new snow.

[0009] Based on the wind speed observations in step 1, determine the change in snow density due to wind compaction.

[0010] Step 3: Determine the effect of temperature on the density of new snow.

[0011] Based on the temperature observations in step 1, determine the relationship between temperature and new snow density.

[0012] Step 4: Determine the effect of relative humidity on the density of fresh snow.

[0013] Based on the relative humidity observations in step 1, determine the change in snow density caused by sublimation.

[0014] Step 5: Determine the effect of surface temperature on the density of new snow.

[0015] Based on the surface temperature observations in step 1, if the surface temperature is above 0°C, determine the change in snow density due to melting.

[0016] Step 6: Determine the new snow density value.

[0017] The new snow density value is obtained by comprehensively analyzing the impact of various meteorological factors in steps two to four on the new snow density.

[0018] Preferably, in step 2, the change value of snow density caused by wind compaction is determined by the following method:

[0019]

[0020] ρ bs : Change in snow density caused by wind (kg / m 3 );

[0021] W r : wind speed (m / s);

[0022] Preferably, in step three, the relationship between the air temperature and the density of new snow is determined by the following method:

[0023]

[0024] ρ tm : Snow density determined by temperature (kg / m 3 );

[0025] T a : air temperature (k);

[0026] Preferably, in step 4, the influence of relative humidity on the density of new snow is determined by the following method:

[0027]

[0028] ρ rh : Change in new snow density due to relative humidity (kg / m 3 );

[0029] RH: relative humidity (%),

[0030] Preferably, in step 5, the influence of the ground surface temperature on the density of new snow is determined by the following method:

[0031]

[0032] ρ sm : Change in new snow density caused by surface temperature (kg / m 3 );

[0033] T a : surface temperature (K);

[0034] Preferably, in step six, the new snow density value is determined by the following method:

[0035] ρ ns =ρ bs +ρ tm +ρ rh +ρ sm

[0036] ρ ns :New snow density (kg / m 3 );

[0037] ρ bs : Same meaning as above;

[0038] ρ tm : Same meaning as above;

[0039] ρ rh : Same meaning as above;

[0040] ρ sm : Same meaning as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Flowchart for determining fresh snow density

[0042] Figure 2 Snow depth simulation based on SnowModel at Zoige Station from September 1 to November 5, 2004 (the observed values ​​are the daily snow depth observation data of the meteorological station, the simulated values ​​of the method of the present invention are the simulation results of the new snow density determined by the method of the present invention, and the simulation values ​​of the original method are the simulation results of the new snow density determined without considering the relative humidity and the surface temperature. Since the observed values ​​of the meteorological station are rounded data, the simulated values ​​are also rounded). DETAILED DESCRIPTION

[0043] In conjunction with a method for determining the density of new snow considering the surface temperature and relative humidity in the present invention, the following embodiments are given. Taking the Zoige station as an example, based on the hourly observation data of the Zoige station, including observation values ​​such as air temperature, wind speed, relative humidity, and surface temperature (specifically, for example, precipitation is observed every 6 hours, and the other observation data are observed every 3 hours), the density of new snow falling at the Zoige station during the period from September 1 to November 5, 2004 is determined. The method comprises the following 6 steps.

[0044] Step 1: Standardization of meteorological observation data. This includes the following sub-steps:

[0045] (1.1) The three-hour observation data of air temperature, wind speed, relative humidity, surface temperature, etc. during the snowfall period are averaged into six-hour data, that is, six-hour meteorological observation data records are formed for four periods of time: 0-6:00, 6-12:00, 12-18:00, and 18-24:00 every day.

[0046] (1.2) Save the observed data such as air temperature, wind speed, relative humidity, and surface temperature in Excel format or other storage methods, for example, in a preset database. And standardize the units of each data, with the air temperature unit standardized to k, the wind speed unit standardized to m / s, the relative humidity unit standardized to %, and the surface temperature unit standardized to k.

[0047] Step 2: Determine the effect of wind speed on the density of new snow:

[0048] In Excel or other applications, write a formula to determine the effect of wind speed on the density of new snow according to the following formula:

[0049]

[0050] ρ bs : Change in snow density caused by wind (kg / m 3 );

[0051] W r : Wind speed (m / s).

[0052] Step 3: Determine the effect of temperature on the density of new snow:

[0053] In Excel or other applications, write a formula to determine the effect of temperature on new snow density according to the following formula:

[0054]

[0055] ρ tm : Snow density determined by temperature (kg / m 3 );

[0056] Ta : Air temperature (k).

[0057] Step 4: Determine the effect of relative humidity on the density of fresh snow:

[0058] In Excel or other applications, write a formula to determine the effect of relative humidity on the density of fresh snow according to the following formula:

[0059]

[0060] ρ rh : Change in new snow density due to relative humidity (kg / m 3 );

[0061] RH: relative humidity (%).

[0062] Step 5: Determine the effect of surface temperature on the density of new snow:

[0063] In Excel or other applications, write a formula to determine the effect of surface temperature on the density of new snow according to the following formula:

[0064]

[0065] ρ sm : Change in new snow density caused by surface temperature (kg / m 3 );

[0066] T a : Surface temperature (k).

[0067] The order of steps 1 to 5 can be set or arranged as needed.

[0068] Step 6: Determine the density of new snow

[0069] In Excel or other software or dedicated application, determine the fresh snow density value according to the following formula:

[0070] ρ ns =ρ bs +ρ tm +ρ rh +ρ sm

[0071] ρ ns :New snow density (kg / m 3 );

[0072] ρ bs : Same meaning as above;

[0073] ρ tm : Same meaning as above;

[0074] ρ rh: Same meaning as above;

[0075] ρ sm : Same meaning as above.

[0076] The density of new snow is determined according to the above method, and the depth of snow accumulation is further determined based on the precipitation and the determined density of new snow. When the determined snow accumulation depth reaches or exceeds a set threshold, it is determined that a snow disaster has occurred and an early warning is issued.

[0077] The methods of the above embodiments of the present invention can be stored in a computer, server or cloud in the form of computer software or application programs.

[0078] The protection scope of the present invention includes a storage device storing computer software implementing the method in the above embodiment; or a computer, server or cloud running the computer software or application.

Claims

1. A method for determining the density of fresh snow, characterized in that The method comprises the following steps: Step 1: Determine the mean value of each meteorological element during snowfall. Based on the meteorological observation data, the observed values ​​of air temperature, wind speed, relative humidity and surface temperature during snowfall were obtained and standardized. Step 2: Determine the effect of temperature on the density of new snow. Based on the temperature determined in step 1, determine the snow density value ρ determined by the temperature tm ; Step 3: Determine the effect of wind speed on the density of new snow. Based on the wind speed determined in step 1, determine the change in snow density due to wind compaction ρ bs , Step 4: Determine the effect of relative humidity on the density of fresh snow. Based on the relative humidity observations in step 1, determine the change in snow density caused by sublimation ρ rh , Step 5: Determine the effect of surface temperature on the density of new snow. Based on the surface temperature observations in step 1, if the surface temperature is above 0°C, determine the change in snow density due to melting: sm , Step 6: Determine the new snow density ρ based on the following formula ns , r ns =ρ bs +r tm +r rh +r sm (1)。 2. A method for determining the density of new snow taking into account surface temperature and relative humidity as claimed in claim 1, characterized in that: In step 3, the effect of wind speed on the density of fresh snow is determined as follows: ρ bs : Change in snow density caused by wind (kg / m 3 ); W r : Wind speed (m / s).

3. A method for determining the density of new snow taking into account surface temperature and relative humidity as claimed in claim 1, characterized in that: In step 2, the relationship between air temperature and new snow density is determined as follows: ρ tm : Snow density determined by temperature (kg / m 3 ); T a : Air temperature (k).

4. A method for determining the density of new snow taking into account surface temperature and relative humidity as claimed in claim 1, characterized in that: In step 4, the effect of relative humidity on the density of fresh snow is determined as follows: ρ rh : Change in new snow density due to relative humidity (kg / m 3 ); RH: relative humidity (%).

5. A method for determining the density of new snow taking into account surface temperature and relative humidity as claimed in claim 1, characterized in that: In step 5, the effect of surface temperature on the density of new snow is determined as follows: ρ sm : Change in new snow density caused by surface temperature (kg / m 3 );T a : Surface temperature (K).

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