Snow melting liquid water outflow calculation method and device and storage medium

Abstract

The invention discloses a snow melting liquid water outflow calculation method and device and a storage medium, and the method comprises the steps: obtaining DEM data, satellite rainfall and air temperature data of a drainage basin, taking each grid unit of the DEM as a calculation unit, and calculating the probability that the rainfall form is snowfall and the average density of a snow layer according to the air temperature of a current time period; iteratively calculating the snow depths of each grid unit at the beginning and the end of a time period and the amount of meltable snow in the time period according to the initial snow depth obtained by satellite remote sensing and in combination with the air temperature and rainfall data of the current time period; and determining the water storage capacity of the snow layer reservoir at the beginning of the time period of each grid unit based on iterative operation, and calculating the water storage capacity of the snow layer reservoir at the end of the time period. According to the method, the regulation and storage effect of the snow layer on the snow melting liquid water is reflected by constructing the snow layer reservoir, refined simulation of the outflow process of the snow melting liquid water on the aspects of time and space is achieved, and runoff forecasting of the alpine region is effectively achieved.

Description

Technical Field

[0001] The present invention belongs to the field of hydrological forecasting, and in particular relates to a method for calculating the outflow of snowmelt liquid water based on a surface "snow layer reservoir". Background Art

[0002] Snowmelt liquid water is an important source of runoff in alpine areas and a key component of the hydrological ecosystem. Against the backdrop of global climate change, the acceleration of the snowmelt process has led to a rapid increase in runoff, increasing the probability of flood disasters. Therefore, accurate calculation of snowmelt runoff formed by snowmelt liquid water is of great significance for water resource management and flood prevention and disaster reduction in alpine areas. With the development of satellite remote sensing technology, calculating snowmelt runoff on a raster scale can more finely and comprehensively consider the spatial heterogeneity of meteorological conditions in the basin. However, current snowmelt runoff simulation methods rarely consider the outflow speed of liquid water in wet snow, which greatly affects the runoff forecasting ability in alpine areas. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a snowmelt liquid water outflow calculation method for effectively simulating and predicting runoff.

[0004] In order to achieve the above object, the present invention specifically adopts the following technical solutions: The present invention first provides a method for calculating snowmelt liquid water outflow, comprising the following steps: Step 1: Obtain the DEM data, satellite precipitation and temperature data of the watershed, use each grid unit of the DEM as a calculation unit, and calculate the probability of snowfall and the average density of the snow layer according to the temperature of the current period; Step 2, based on the initial snow depth obtained by satellite remote sensing, combined with the temperature and precipitation data of the current period obtained in step 1, iteratively calculate the snow depth of each grid cell at the beginning and end of the period and the amount of meltable snow in the period; Step 3, determining the water storage capacity of the snow layer reservoir at the beginning and end of each grid unit time period based on iterative calculation; calculating the water storage capacity of the snow layer reservoir at the end of the time period according to the snow depth of each grid unit at the end of the time period obtained by iterative calculation in step 2; Step 4, based on the amount of meltable snow in the time period determined in step 2 and the water storage capacity of the snow layer reservoir at the beginning and end of each grid unit time period and the water storage capacity of the snow layer reservoir at the end of the time period calculated in step 3, obtain the snowmelt liquid water outflow in each grid unit time period and the water storage capacity of the snow layer reservoir at the end of the time period; the obtained water storage capacity of the snow layer reservoir at the end of the time period is used as the water storage capacity of the snow layer reservoir at the beginning of the time period in step 3 for iterative calculation at the next moment.

[0005] The present invention conceptualizes the snow layer containing liquid water as a "snow layer reservoir", whose water storage capacity is equal to the liquid water stored in the snow layer reservoir. The liquid water in the snow layer reservoir flows out at a certain rate, and at the same time, a part of the solid snow in the snow layer is converted into liquid water to supplement the water storage capacity of the snow layer reservoir, and the water storage capacity does not exceed the water storage capacity of the snow layer reservoir.

[0006] In step 4, the specific algorithm for calculating the water storage capacity of the snow layer reservoir at the end of the period is: (1) In the formula, and are the snow reservoir water storage at the end and beginning of the period (mm); is the water storage capacity of the snow layer reservoir at the end of the period (mm); is the outflow coefficient of liquid water in the snow layer reservoir, which takes into account the regulation and storage effect of the snow layer and reflects the outflow speed of liquid water in the snow layer reservoir; is the amount of meltable snow in the time period, that is, the amount of solid snow melted into liquid water (mm); is the rate at which solid snow in the first snow layer reservoir of the time period is converted into liquid water. As for the snow layer as a whole, the deeper the snow, the more obvious the compaction of the snow layer, the lower the proportion of liquid water, and the lower the average rate at which solid snow is converted into liquid water. Therefore, The estimation of is shown in formula (2).

[0007] (2) In the formula, is the water storage capacity of the snow layer reservoir at the beginning of the period (mm).

[0008] Snow layer reservoir storage capacity: The snow layer containing liquid water is generalized as a snow layer reservoir, and its storage capacity is equal to the ability of the snow layer reservoir to store liquid water. When the water storage capacity is less than the water storage capacity, the snowmelt liquid water in the snow layer reservoir flows out at a certain rate; when the water storage capacity is greater than the water storage capacity, in addition to the snowmelt liquid water that flows out normally at a certain rate, the liquid water exceeding the water storage capacity flows out directly.

[0009] In step 3, the specific algorithm for calculating the water storage capacity of the snow layer reservoir at the end of the period is: (3) In the formula, is the conversion coefficient, which reflects the linear relationship between the snow layer depth and the water storage capacity of the snow layer reservoir. The thicker the snow layer, the greater the theoretical water storage capacity of the snow layer reservoir. The experience value is 0.5; is the snow depth at the end of the time period (mm).

[0010] Snowmelt liquid water outflow: Snowmelt liquid water outflow includes direct outflow from meltable snow, outflow from stored water in the snow layer reservoir and water overflow after full storage.

[0011] In step 4, the specific algorithm for calculating the snowmelt liquid water outflow during the period is: (4) (5) In step 2, the specific algorithm for calculating the amount of meltable snow in the time period and the snow depth at the end of the time period is: (6) (7) In the formula, is the air temperature (℃). When the air temperature is less than 0℃, the theoretical amount of snow that can be melted is 0. When the air temperature is higher than 0℃ and the snow depth at the beginning of the period is less than the snow-melting capacity of the snow layer, the snow layer is completely converted into snow-melting liquid water. On the contrary, the theoretical amount of snow that can be melted has nothing to do with the snow depth, but is related to the snow-melting capacity of the snow layer. is the average density of the snow layer (g / cm 3 ); is the snowmelt factor of the snow layer (mm / day·℃), which reflects the speed of the snowmelt process. Its value may change with the season, with the maximum value occurring in summer and the minimum value occurring in winter. The value range is 0 to 15; Represents the melting capacity of the snow layer on a daily scale (mm); is the snow depth at the beginning of the period (mm); Indicates the depth of new snow formed by snowfall in the current period (mm), calculated as: (8) In the formula, is the precipitation on the grid during the period (mm), Represents the probability of precipitation falling as snow.

[0012] In step 1, the specific algorithm for calculating the probability of precipitation in the form of snowfall and the average density of the snow layer is: (9) (10) In the formula, is the temperature (℉). It is more practical to judge whether snowfall will occur in a probabilistic way than a single temperature threshold method. When the temperature is lower than a certain temperature threshold, the probability of snowfall is 1. When the temperature gradually rises, the probability of snowfall decreases exponentially. The average density of the snow layer is related to the temperature. Generally speaking, within a certain temperature range, the colder and drier the air is, the smaller the density of the snow layer. When the temperature exceeds or falls below the temperature range, the density of the snow layer remains basically unchanged.

[0013] The present invention also provides a snowmelt liquid water outflow calculation device, comprising a processor and a memory; the memory stores a program or instruction, and the program or instruction is loaded and executed by the processor to implement the steps of the snowmelt liquid water outflow calculation method.

[0014] The present invention also provides a computer-readable storage medium, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the snowmelt liquid water outflow calculation method are implemented.

[0015] Beneficial effects of the present invention: The present invention is based on a method for calculating the outflow of melted snow liquid water from a surface "snow layer reservoir". First, the DEM data of the watershed, satellite precipitation and temperature data are obtained, and each grid unit of the DEM is used as a calculation unit. The probability of precipitation in the form of snowfall and the average density of the snow layer are calculated according to the temperature of the current time period; then, according to the initial snow depth obtained by satellite remote sensing, the snow depth of each grid unit at the beginning and end of the time period and the amount of meltable snow in the time period are iteratively calculated in combination with the temperature and precipitation data of the current time period; then, based on the iterative operation, the water storage capacity of the snow layer reservoir at the beginning of the time period of each grid unit is determined, and the water storage capacity of the snow layer reservoir at the end of the time period is calculated; finally, the melted snow liquid water calculation method based on the surface "snow layer reservoir" is used to obtain the melted snow liquid water outflow in each grid unit time period and the water storage capacity of the snow layer reservoir at the end of the time period, and an iterative operation is performed. The present invention proposes a method for calculating the outflow of liquid water from snowmelt in grid cells based on the surface "snow layer reservoir", which takes into account the regulating and storing effect of the snow layer on the liquid water in snowmelt. It solves the problem that current snowmelt runoff calculation methods rarely consider the outflow speed of liquid water in wet snow, and can effectively realize runoff forecasting in high-altitude and cold areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of a method for calculating the outflow of liquid water from snowmelt based on a surface "snow layer reservoir" provided by the present invention; Figure 2 is a spatial distribution map of snow depth in a watershed in a specific embodiment; Figure 3 is the water storage capacity of the snow layer reservoir of each grid in the watershed in the specific embodiment; Figure 4 is the snowmelt liquid water outflow of each grid in the watershed in the specific embodiment; Figure 5 It is the daily runoff simulation result obtained by using the snowmelt liquid water outflow method based on the surface "snow layer reservoir" in the specific embodiment. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] Example 1 like Figure 1 As shown, the present invention provides a grid-scale snowmelt liquid water outflow calculation method based on a surface "snow layer reservoir", comprising the following steps: Step 1: Obtain the DEM data, satellite precipitation and temperature data of the watershed, use each grid unit of the DEM as a calculation unit, and calculate the probability of snowfall and the average density of the snow layer according to the temperature of the current period. The specific steps include: Step 11, obtain the DEM data of the basin, satellite precipitation and temperature data, and use each grid unit of the DEM as a calculation unit; Step 12, calculate the probability of precipitation in the form of snow and the average density of the snow layer according to the temperature of the current period: (1) (2) In the formula, represents the probability that the precipitation will be in the form of snow, is the average density of the snow layer, (℉) and (℃) is the air temperature.

[0020] Download the DEM data of the Shigu River Basin in the upper reaches of the Jinsha River Basin, the daily satellite precipitation and temperature data from 2013 to 2020, take each grid cell of the DEM as the calculation unit, and use GIS spatial analysis tools to determine the daily precipitation and temperature of each grid cell.

[0021] Step 2: Based on the initial snow depth obtained by satellite remote sensing, combined with the temperature and precipitation data of the current period, iteratively calculate the snow depth of each grid cell at the beginning and end of the period and the amount of meltable snow in the period. The specific steps include: Step 21, taking the initial snow depth obtained by satellite remote sensing as the snow depth at the beginning of the period, and calculating the new snow depth formed by snowfall in the period: (3) In the formula, is the new snow depth (mm), is the grid precipitation in the current period (mm).

[0022] Step 22, according to the temperature of the current period, calculate the theoretical amount of snow that can be melted in the period: (4) In the formula, is the snow depth at the beginning of the period (mm), is the snowmelt factor of the snow layer (mm / day·℃), Represents the snowmelt capacity of the snow layer on a daily scale (mm).

[0023] Step 23, based on the snow depth at the beginning of the time period and the theoretical amount of meltable snow in the time period, calculate the snow depth at the end of the current time period, that is, the snow depth at the beginning of the next time period: (5) In the formula, is the snow depth at the end of the time period (mm).

[0024] Download the long-term snow depth data set of China and use GIS spatial analysis tools to obtain the grid snow depth data of Shigu Basin on December 31, 2012, such as Figure 2 Combining the daily precipitation and temperature of each grid cell, the daily snow depth and meltable snow volume of each grid cell in the Shigu Basin from 2013 to 2020 were obtained through iterative calculation.

[0025] Step 3, based on iterative calculation, determine the water storage capacity of the snow layer reservoir at the beginning of each grid unit period, and calculate the water storage capacity of the snow layer reservoir at the end of the period.

[0026] Step 31, based on iterative calculation, determine the water storage capacity of the snow layer reservoir at the beginning of the time period, that is, the amount of liquid water stored in the snow layer reservoir. When the water storage capacity is less than the water storage capacity, the snowmelt liquid water flows out at a certain rate; when the water storage capacity is greater than the water storage capacity, in addition to the snowmelt liquid water that flows out normally at a certain rate, the liquid water that exceeds the water storage capacity flows out directly; Step 32, calculate the water storage capacity of the snow layer reservoir at the end of the time period, that is, the ability of the snow layer reservoir to store liquid water. The thicker the snow layer, the greater the theoretical water storage capacity of the snow layer reservoir: (6) In the formula, is the water storage capacity of the snow reservoir at the end of the period, is the conversion coefficient, which reflects the linear relationship between the snow layer depth and the water storage capacity of the snow layer reservoir, giving The experience value is 0.5.

[0027] The daily snow depth of each grid unit in the Shigu Basin determines the daily snow layer reservoir storage capacity of each grid unit. Taking April 1, 2014 as an example, the snow layer reservoir storage capacity of each grid in the Shigu Basin on that day is as follows: Figure 3 shown.

[0028] Step 4: Use the snowmelt liquid water calculation method based on the surface "snow layer reservoir" to obtain the snowmelt liquid water outflow in each grid unit time period and the snow layer reservoir water storage capacity at the end of the time period, and perform iterative calculations.

[0029] Step 41, calculate the water storage capacity of the snow layer reservoir at the end of the time period. The liquid water in the snow layer reservoir flows out at a certain rate. At the same time, part of the solid snow in the snow layer is converted into liquid water to supplement the water storage capacity of the snow layer reservoir. The actual water storage capacity does not exceed the water storage capacity of the snow layer reservoir: (7) In the formula, and are the water storage of the snow layer reservoir at the end and beginning of the period, and the water storage of the snow layer reservoir at the beginning of the period Assign a value of 0, is the outflow coefficient of liquid water in the snow layer reservoir, which takes into account the regulation and storage effect of the snow layer and reflects the outflow speed of liquid water in the snow layer reservoir; is the rate at which solid snow in the first snow layer reservoir of the time period is converted into liquid water. As for the snow layer as a whole, the deeper the snow, the more obvious the compaction of the snow layer, the lower the proportion of liquid water, and the lower the average rate at which solid snow is converted into liquid water. Therefore, The estimation of is shown in formula (8): (8) Step 42, calculate the snowmelt liquid water outflow during the time period, the snowmelt liquid water outflow includes the direct outflow of the meltable snow, the outflow of the stored water in the snow layer reservoir and the water overflow after being filled: (9) (10) Step 43, perform iterative calculation, that is, the water storage capacity of the snow layer reservoir at the end of the current period is used as the water storage capacity of the snow layer reservoir at the beginning of the next period, and the calculation is performed in step 3.

[0030] The daily snowmelt liquid water outflow and snow reservoir storage capacity in the Shigu Basin from 2013 to 2020 were obtained through iterative calculation. Taking March 2014 as an example, the snowmelt liquid water outflow of each grid in the Shigu Basin in that month is as follows: Figure 4 As shown. According to step 1, the precipitation is divided into rainfall and snowfall, where the daily rainfall and snowmelt liquid water outflow of the grid unit are summed up as the grid unit's inflow, which is used as the input of the distributed runoff generation and confluence model - the grid Xin'anjiang model to simulate the daily runoff of the Shigu hydrological station. 2013 is taken as the warm-up year, 2014~2017 as the rate period, and 2018~2020 as the verification period. The determination coefficient ( R 2 ), Nash-Sutcliffe efficiency coefficient ( NSE ) and mean absolute percentage error (MAPE) are used as evaluation indicators of model simulation effect. The calculation formulas of the three are: In the formula, and Respectively Observed flow and simulated flow values ​​(m 3 / s); and are the average values ​​of observed flow and simulated flow (m 3 / s), The total number of days.

[0031] The coefficient of determination, Nash-Sutcliffe efficiency coefficient and mean absolute percentage error were calculated. The simulation results of the model are as follows Figure 5 As shown. At regular rates, They were 0.899, 0.846, and 17.337% respectively; during the validation period, They are 0.922, 0.807, and 17.700%, respectively, indicating that the grid Xin'anjiang model coupled with the snowmelt liquid water outflow calculation method based on the surface "snow layer reservoir" has a good effect on the runoff simulation of the Shigu Basin.

[0032] Example 2 The present embodiment provides a snowmelt liquid water outflow calculation device, comprising a processor and a memory; the memory stores a program or instruction, and the program or instruction is loaded and executed by the processor to implement the steps of the snowmelt liquid water outflow calculation method of the above embodiment.

[0033] Example 3 This embodiment provides a computer-readable storage medium, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the snowmelt liquid water outflow calculation method of the above embodiment are implemented.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. A number of improvements and optimizations made by those skilled in the art without departing from the concept of the present invention should be considered as within the scope of protection of the present invention.

Claims

1. A method for calculating snowmelt liquid water outflow, characterized in that: The following steps are involved: Step 1: Obtain the DEM data, satellite precipitation and temperature data of the watershed, use each grid unit of the DEM as a calculation unit, and calculate the probability of snowfall and the average density of the snow layer according to the temperature of the current period; Step 2, based on the initial snow depth obtained by satellite remote sensing, combined with the temperature and precipitation data of the current period obtained in step 1, iteratively calculate the snow depth of each grid cell at the beginning and end of the period and the amount of meltable snow in the period; Step 3, determining the water storage capacity of the snow layer reservoir at the beginning and end of each grid unit time period based on iterative calculation; According to the snow depth of each grid cell at the end of the period obtained by iterative calculation in step 2, the water storage capacity of the snow layer reservoir at the end of the period is calculated; Step 4, based on the amount of meltable snow in the time period determined in step 2 and the water storage capacity of the snow layer reservoir at the beginning and end of each grid unit time period and the water storage capacity of the snow layer reservoir at the end of the time period calculated in step 3, obtain the snowmelt liquid water outflow in each grid unit time period and the water storage capacity of the snow layer reservoir at the end of the time period; The obtained snow layer reservoir water storage capacity at the end of the time period is used as the snow layer reservoir water storage capacity at the beginning of the time period in step 3 for the next iterative calculation.

2. The snowmelt liquid water outflow calculation method according to claim 1, characterized in that: In step 4, the calculation method for the snowmelt liquid water outflow during the period is: In the formula, is the snowmelt liquid water outflow during the period; is the amount of meltable snow in the time period; and are the water storage capacity of the snow layer reservoir at the end and beginning of the period, respectively.

3. The snowmelt liquid water outflow calculation method according to claim 2, characterized in that: Snow layer reservoir water storage at the end of the period for: In the formula, is the water storage capacity of the snow reservoir at the end of the period; is the outflow coefficient of liquid water in the snow layer reservoir; is the rate at which solid snow in the first snow layer reservoir of the period is converted into liquid water; The rate at which solid snow in the reservoir turns into liquid water during the first snow layer of the period for: In the formula, It is the water storage capacity of the snow layer reservoir at the beginning of the period.

4. The snowmelt liquid water outflow calculation method according to claim 3 is characterized in that: The calculation method of the water storage capacity of the snow layer reservoir at the end of the period is: In the formula, It is the conversion coefficient reflecting the linear relationship between snow layer depth and snow reservoir storage capacity; is the snow depth at the end of the period; Snow depth at the end of the period for: In the formula, The snow depth at the beginning of the period; The depth of new snow formed by snowfall in the current period; is the average density of the snow layer.

5. The snowmelt liquid water outflow calculation method according to claim 4, characterized in that: New snow depth for: In the formula, is the precipitation on the grid during the period; Represents the probability of precipitation falling as snow.

6. The snowmelt liquid water outflow calculation method according to claim 5, characterized in that: Probability of precipitation falling as snow for: In the formula, The temperature is in Fahrenheit.

7. The snowmelt liquid water outflow calculation method according to claim 5, characterized in that: Average density of snow layer for: In the formula, The temperature is in degrees Celsius.

8. The snowmelt liquid water outflow calculation method according to claim 4, characterized in that: Amount of snow that can be melted during the period for: In the formula, The snowmelt factor of the snow layer, Represents the snowmelt capacity of the snow layer on a daily scale.

9. A snowmelt liquid water outflow calculation device, characterized in that: It comprises a processor and a memory; the memory stores a program or instruction, and the program or instruction is loaded and executed by the processor to implement the steps of the snowmelt liquid water outflow calculation method as claimed in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The readable storage medium stores a program or instruction, and when the program or instruction is executed by the processor, the steps of the snowmelt liquid water outflow calculation method according to any one of claims 1 to 8 are implemented.

Images