Frozen soil annual average ground temperature simulation method based on air temperature

Abstract

The invention discloses a frozen soil annual average ground temperature simulation method based on air temperature. The method comprises the following steps: firstly, determining a research area and a year interval; then data acquisition and arrangement are carried out; the data comprises near-surface air temperature data, land coverage data and accumulated snow depth data, according to the determined research area and year interval, acquiring near-surface air temperature data with the spatial resolution of 1km and the time resolution of daily scale corresponding to the research area and year, land coverage data and accumulated snow depth data with the spatial resolution of 1 km in the corresponding research area and year are obtained, then key parameters of the model are calculated, and finally the annual average ground temperature of frozen soil is calculated. Simulation calculation is carried out on the annual average ground temperature of frozen soil in a research area.

Description

Technical Field

[0001] The invention belongs to the technical field of glacier frozen soil, and in particular relates to a method for simulating the annual average ground temperature of frozen soil based on air temperature. Background Art

[0002] Permafrost refers to a layer of soil or rock at a certain depth below the surface of the earth, which remains below 0°C for at least two years. The annual average ground temperature of frozen soil referred to in the present invention is the annual average soil temperature at the depth of zero amplitude of soil temperature (i.e., the soil temperature at this location does not change periodically within a year). The annual average ground temperature of frozen soil is an important indicator for measuring the degradation of frozen soil. In the context of climate change, the simulation and estimation of the annual average ground temperature of frozen soil is of great significance to the degradation of frozen soil and the ecosystem, hydrological process and engineering construction in frozen soil areas.

[0003] The annual average ground temperature of frozen soil can be obtained through field observation, model simulation and other methods. Field observation is to measure the temperature change of frozen soil by drilling holes in frozen soil. Although field observation has high accuracy, it can only obtain the annual average ground temperature of frozen soil at a point scale. Due to its high cost, it is difficult to meet the application needs at the regional scale. Model simulation includes the freezing index model, the permafrost top temperature (TTOP) model, the Geophysical Institute Permafrost Laboratory 2 (GIPL2) model and the Kudryavtsev method.

[0004] The TTOP model calculates the annual average ground temperature of frozen soil by using a balance equation. The model uses air temperature as the main driver and couples semi-empirical formulas to solve the thermal excursion from air to the ground and the influence of snow cover. Currently, the TTOP model has been widely used in Canada, Norway, Russia and the Qinghai-Tibet Plateau in my country.

[0005] In order to obtain large-scale, high-resolution, and long-term series of annual average ground temperature information of frozen soil, the present invention provides a method for simulating annual average ground temperature of frozen soil based on air temperature based on the TTOP model. This method has broad application prospects in simulating and predicting high-resolution annual average ground temperature of frozen soil at a regional scale. Summary of the invention

[0006] The purpose of the present invention is to provide a method for simulating the annual average ground temperature of frozen soil based on air temperature, and to simulate and calculate the annual average ground temperature of frozen soil in a study area.

[0007] The technical solution adopted by the present invention is a method for simulating the annual average ground temperature of frozen soil based on air temperature, which is specifically implemented according to the following steps:

[0008] Step 1: Determine the research area and year range;

[0009] Step 2: Data acquisition and organization;

[0010] Step 3: Calculation of key model parameters;

[0011] Step 4: Calculate the annual average ground temperature of frozen soil.

[0012] The present invention is also characterized in that:

[0013] Step 2 is implemented as follows:

[0014] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0015] The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n f Ratio of air temperature to ground temperature during the melting period t ; Ratio of thermal conductivity of frozen and thawed soils k .

[0016] In step 3, the air freezing day index FDD and the air melting day index TDD are calculated based on the near-surface temperature data on a daily scale obtained in step 2, that is, FDD is the cumulative daily average temperature of the days with a daily average temperature less than 0°C in a year, and TDD is the cumulative daily average temperature of the days with a daily average temperature greater than 0°C in a year;

[0017] Step 3 f is the ratio of freezing temperature to ground temperature. The freezing temperature is the daily average temperature less than 0℃. t It is the ratio of the temperature during the melting period to the ground temperature. The temperature during the melting period refers to the daily average temperature greater than 0℃.

[0018] In step 3, during the freezing period, n f The value of is determined according to the type of land cover, among which forest, shrub and wetland have n f The values ​​are 0.35, 0.3 and 0.6 respectively. In bare land and grassland, n f Determined by temperature and snow depth: First, determine the value of nf based on the relationship diagram between nf, temperature and snow depth. First, obtain the average temperature of the area, determine the relationship curve between nf and snow depth under the temperature, and then read the corresponding nf value from the curve according to the snow depth in the area. During the melting period, nf t The value of is also determined by the type of land cover, with forests, shrubs and wetlands having n t The values ​​are 0.9, 1.0 and 0.85 respectively.t The value is 1.0;

[0019] The thermal conductivity ratio of frozen and thawed soil in step 3 is r k :r k is the ratio of the thermal conductivity of soil in the frozen and thawed states, r k The value depends on soil moisture and organic matter content, r k The value of is also determined according to the type of land cover. The values ​​of forest, shrub, wetland, farmland, grassland and bare land are 0.95, 0.7, 0.55, 0.75, 0.75 and 0.95 respectively.

[0020] Step 4 is implemented according to the following steps:

[0021] The permafrost top temperature model TTOP is used to calculate the annual average ground temperature of frozen soil. The annual average ground temperature of frozen soil is calculated as follows:

[0022]

[0023] Wherein, MAGT is the annual average ground temperature of frozen soil, n f is the ratio of freezing period air temperature to ground temperature; FDD is air freezing day index, r k is the ratio of thermal conductivity of frozen and thawed soil, n t is the ratio of air temperature to ground temperature during the melting period, TDD is the air melting day index, and τ is the number of days in a year.

[0024] The beneficial effect of the present invention is that the method for simulating the annual average ground temperature of frozen soil based on air temperature can simulate and calculate the temporal and spatial distribution of the annual average ground temperature of frozen soil based on air temperature, combined with data such as land cover and snow depth. It has the following advantages:

[0025] (1) High simulation accuracy: The method for simulating the annual average ground temperature of frozen soil based on air temperature proposed in the present invention has a spatial resolution of 1 km and a temporal resolution of 1 year, which can better simulate and analyze the spatiotemporal changes of the annual average ground temperature of frozen soil.

[0026] (2) High universality: The method for simulating the annual average ground temperature of frozen soil based on air temperature proposed in the present invention can flexibly select the research area according to the needs and can be widely used in frozen soil distribution areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the ratio of freezing period air temperature to ground temperature f Relationship with near-surface air temperature and snow depth. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0030] Step 1: Determine the research area and year range;

[0031] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0032] Step 2 is implemented as follows:

[0033] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0034] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0035] The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n f Ratio of air temperature to ground temperature during the melting period t ; Ratio of thermal conductivity of frozen and thawed soils k .

[0036] In step 3, the air freezing day index FDD and the air melting day index TDD are calculated based on the near-surface temperature data on a daily scale obtained in step 2, that is, FDD is the cumulative daily average temperature of the days with a daily average temperature less than 0°C in a year, and TDD is the cumulative daily average temperature of the days with a daily average temperature greater than 0°C in a year;

[0037] The ratio of air temperature to ground temperature in step 3 reflects the ratio of near-ground air temperature to ground temperature, which is mainly affected by ground cover, near-ground air temperature and snow accumulation. f is the ratio of freezing temperature to ground temperature. The freezing temperature is the daily average temperature less than 0℃. t It is the ratio of the temperature during the melting period to the ground temperature. The temperature during the melting period refers to the daily average temperature greater than 0℃.

[0038] In step 3, during the freezing period, n f The value of is determined according to the type of land cover, among which forest, shrub and wetland have n f The values ​​are 0.35, 0.3 and 0.6 respectively. In bare land and grassland, nf Determine based on temperature and snow depth: First, determine the value of nf based on the relationship between nf, temperature and snow depth. First, obtain the average temperature of the area, determine the relationship curve between nf and snow depth under the temperature, and then read the corresponding nf value from the curve based on the snow depth in the area, such as Figure 1 During the melting period, n t The value of is also determined by the type of land cover, with forests, shrubs and wetlands having n t The values ​​are 0.9, 1.0 and 0.85 respectively. t The value is 1.0;

[0039] The thermal conductivity ratio of frozen and thawed soil in step 3 is r k :r k is the ratio of the thermal conductivity of soil in the frozen and thawed states, r k The value depends on soil moisture and organic matter content, r k The value of is also determined according to the type of land cover. The values ​​of forest, shrub, wetland, farmland, grassland and bare land are 0.95, 0.7, 0.55, 0.75, 0.75 and 0.95 respectively.

[0040] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0041] Step 4 is implemented according to the following steps:

[0042] The permafrost top temperature model TTOP is used to calculate the annual average ground temperature of frozen soil. The annual average ground temperature of frozen soil is calculated as follows:

[0043]

[0044] Wherein, MAGT is the annual average ground temperature of frozen soil, n f is the ratio of freezing period air temperature to ground temperature; FDD is air freezing day index, r k is the ratio of thermal conductivity of frozen and thawed soil, n t is the ratio of air temperature to ground temperature during the melting period, TDD is the air melting day index, and τ is the number of days in a year.

[0045] Example 1

[0046] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0047] Step 1: Determine the research area and year range;

[0048] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0049] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0050] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0051] Example 2

[0052] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0053] Step 1: Determine the research area and year range;

[0054] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0055] Step 2 is implemented as follows:

[0056] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0057] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0058] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0059] Example 3

[0060] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0061] Step 1: Determine the research area and year range;

[0062] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0063] Step 2 is implemented as follows:

[0064] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0065] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0066] The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n f Ratio of air temperature to ground temperature during the melting period t ; Ratio of thermal conductivity of frozen and thawed soils k .

[0067] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0068] Example 4

[0069] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0070] Step 1: Determine the research area and year range;

[0071] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0072] Step 2 is implemented as follows:

[0073] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0074] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0075] The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n fRatio of air temperature to ground temperature during the melting period t ; Ratio of thermal conductivity of frozen and thawed soils k .

[0076] In step 3, the air freezing day index FDD and the air melting day index TDD are calculated based on the near-surface temperature data on a daily scale obtained in step 2, that is, FDD is the cumulative daily average temperature of the days with a daily average temperature less than 0°C in a year, and TDD is the cumulative daily average temperature of the days with a daily average temperature greater than 0°C in a year;

[0077] The ratio of air temperature to ground temperature in step 3 reflects the ratio of near-ground air temperature to ground temperature, which is mainly affected by ground cover, near-ground air temperature and snow accumulation. f is the ratio of freezing temperature to ground temperature. The freezing temperature is the daily average temperature less than 0℃. t It is the ratio of the temperature during the melting period to the ground temperature. The temperature during the melting period refers to the daily average temperature greater than 0℃.

[0078] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0079] Example 5

[0080] The method for simulating the annual average ground temperature of frozen soil based on air temperature of the present invention is specifically implemented according to the following steps:

[0081] Step 1: Determine the research area and year range;

[0082] Step 2: Data acquisition and organization: Based on the research area and year range determined in the first step, obtain the required data and information from existing materials and literature.

[0083] Step 2 is implemented as follows:

[0084] The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

[0085] Step 3: Calculate key parameters of the model: Calculate the key parameters required for the model based on the relevant data obtained in the second step.

[0086] The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n f Ratio of air temperature to ground temperature during the melting periodt ; Ratio of thermal conductivity of frozen and thawed soils k .

[0087] In step 3, the air freezing day index FDD and the air melting day index TDD are calculated based on the near-surface temperature data on a daily scale obtained in step 2, that is, FDD is the cumulative daily average temperature of the days with a daily average temperature less than 0°C in a year, and TDD is the cumulative daily average temperature of the days with a daily average temperature greater than 0°C in a year;

[0088] The ratio of air temperature to ground temperature in step 3 reflects the ratio of near-ground air temperature to ground temperature, which is mainly affected by ground cover, near-ground air temperature and snow accumulation. f is the ratio of freezing temperature to ground temperature. The freezing temperature is the daily average temperature less than 0℃. t It is the ratio of the temperature during the melting period to the ground temperature. The temperature during the melting period refers to the daily average temperature greater than 0℃.

[0089] In step 3, during the freezing period, n f The value of is determined according to the type of land cover, among which forest, shrub and wetland have n f The values ​​are 0.35, 0.3 and 0.6 respectively. In bare land and grassland, n f Determine based on temperature and snow depth: First, determine the value of nf based on the relationship between nf, temperature and snow depth. First, obtain the average temperature of the area, determine the relationship curve between nf and snow depth under the temperature, and then read the corresponding nf value from the curve based on the snow depth in the area, such as Figure 1 During the melting period, n t The value of is also determined by the type of land cover, with forests, shrubs and wetlands having n t The values ​​are 0.9, 1.0 and 0.85 respectively. t The value is 1.0;

[0090] The thermal conductivity ratio of frozen and thawed soil in step 3 is r k :r k is the ratio of the thermal conductivity of soil in the frozen and thawed states, r k The value depends on soil moisture and organic matter content, r k The value of is also determined according to the type of land cover. The values ​​of forest, shrub, wetland, farmland, grassland and bare land are 0.95, 0.7, 0.55, 0.75, 0.75 and 0.95 respectively.

[0091] Step 4: Calculation of annual average ground temperature of frozen soil: Calculate the annual average ground temperature of frozen soil based on the key model parameters calculated in the third step.

[0092] Step 4 is implemented according to the following steps:

[0093] The permafrost top temperature model TTOP is used to calculate the annual average ground temperature of frozen soil. The annual average ground temperature of frozen soil is calculated as follows:

[0094]

[0095] Wherein, MAGT is the annual average ground temperature of frozen soil, n f is the ratio of freezing period air temperature to ground temperature; FDD is air freezing day index, r k is the ratio of thermal conductivity of frozen and thawed soil, n t is the ratio of air temperature to ground temperature during the melting period, TDD is the air melting day index, and τ is the number of days in a year.

[0096] Example 6

[0097] 1. Determine the research area and year range

[0098] The working area of ​​the embodiment is located in the Qinghai-Tibet Plateau region of my country, including the Tibet Autonomous Region, Qinghai Province, southern Xinjiang Uygur Autonomous Region, western Sichuan Province, and parts of Gansu Province and Yunnan Province. The Qinghai-Tibet Plateau extends to the Kunlun Mountains and Qilian Mountains in the north, the Himalayas in the south, the Pamirs and Karakoram Mountains in the west, and the Qinling Mountains and the Loess Plateau in the east, with an area of ​​about 2.5 million km 2 The study year range was determined to be 1981–2018.

[0099] 2. Data Acquisition and Arrangement

[0100] The spatial resolution of the Qinghai-Tibet Plateau from 1981 to 2018 is 1 km, and the temporal resolution is daily near-surface air temperature data. The land cover data and snow depth data of the Qinghai-Tibet Plateau from 1981 to 2018 are obtained with a spatial resolution of 1 km.

[0101] 3. Calculation of key model parameters

[0102] According to the near-surface air temperature data of the Qinghai-Tibet Plateau obtained in the second step, the daily average temperature of the days with the average daily temperature less than 0°C in the Qinghai-Tibet Plateau in a year is accumulated to obtain the air freezing day index FDD. The daily average temperature of the days with the average daily temperature greater than 0°C in the Qinghai-Tibet Plateau in a year is accumulated to obtain the air melting day index TDD.

[0103] Based on the land cover data and snow depth data of the Qinghai-Tibet Plateau obtained in the second step, the ratio of the freezing period air temperature to the ground temperature of the Qinghai-Tibet Plateau was obtained. f Ratio of air temperature to ground temperature during the melting period t .

[0104] According to the land cover data of the Qinghai-Tibet Plateau obtained in the second step, the thermal conductivity ratio of frozen and thawed soils in the Qinghai-Tibet Plateau is obtained. k .

[0105] 4. Calculation of annual average ground temperature of frozen soil

[0106] According to the key parameters of the model calculated in the third step, the annual average ground temperature of the frozen soil on the Qinghai-Tibet Plateau is calculated. It is calculated that the annual average ground temperature of the frozen soil on the Qinghai-Tibet Plateau rose from 0.77℃ to 1.49℃ during 1981-2018. The annual average ground temperature of the frozen soil on the Qinghai-Tibet Plateau simulated by this method is compared with the annual average ground temperature of the frozen soil measured in 155 boreholes. It is found that the average deviation between the simulated values ​​and the measured values ​​of the 155 boreholes is 0.17℃, which proves the high accuracy of the annual average ground temperature of the frozen soil calculated by this method.

Claims

1. A method for simulating the annual average ground temperature of frozen soil based on air temperature, characterized in that: Follow the steps below to implement it: Step 1: Determine the research area and year range; Step 2: Data acquisition and organization; Step 3: Calculation of key model parameters; Step 4: Calculate the annual average ground temperature of frozen soil.

2. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 1, characterized in that: The step 2 is specifically implemented according to the following steps: The data include near-surface air temperature data, land cover data and snow depth data. According to the study area and year range determined in step 1, obtain the near-surface air temperature data with a spatial resolution of 1 km and a temporal resolution of daily scale for the corresponding study area and year, and obtain the land cover data and snow depth data with a spatial resolution of 1 km for the corresponding study area and year.

3. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 2, characterized in that: The model used in step 3 is the permafrost top temperature model TTOP. The key parameters of the model include: air freezing day index FDD and air melting day index TDD; the ratio of freezing period air temperature to ground temperature n f Ratio of air temperature to ground temperature during the melting period t ; Ratio of thermal conductivity of frozen and thawed soils k .

4. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 3, characterized in that: The air freezing daily index FDD and the air melting daily index TDD in step 3 are calculated based on the near-surface temperature data on a daily scale obtained in step 2, that is, FDD is the cumulative average daily temperature of the days with an average daily temperature less than 0°C in a year, and TDD is the cumulative average daily temperature of the days with an average daily temperature greater than 0°C in a year.

5. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 3, characterized in that: In step 3, n f is the ratio of freezing temperature to ground temperature. The freezing temperature is the daily average temperature less than 0℃. t It is the ratio of the temperature during the melting period to the ground temperature. The temperature during the melting period refers to the daily average temperature greater than 0℃.

6. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 5, characterized in that: In step 3, during the freezing period, n f The value of is determined according to the type of land cover, among which forest, shrub and wetland have n f The values ​​are 0.35, 0.3 and 0.6 respectively. In bare land and grassland, n f Determined by temperature and snow depth: First, determine the value of nf based on the relationship diagram between nf, temperature and snow depth. First, obtain the average temperature of the area, determine the relationship curve between nf and snow depth under the temperature, and then read the corresponding nf value from the curve according to the snow depth in the area. During the melting period, nf t The value of is also determined by the type of land cover, with forests, shrubs and wetlands having n t The values ​​are 0.9, 1.0 and 0.85 respectively. t The value is 1.

0.

7. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 6, characterized in that: The thermal conductivity ratio of the frozen and thawed soil in step 3 is r k :r k is the ratio of the thermal conductivity of soil in the frozen and thawed states, r k The value depends on soil moisture and organic matter content, r k The value of is also determined according to the type of land cover. The values ​​of forest, shrub, wetland, farmland, grassland and bare land are 0.95, 0.7, 0.55, 0.75, 0.75 and 0.95 respectively.

8. The method for simulating annual average ground temperature of frozen soil based on air temperature according to claim 4, characterized in that: The step 4 is specifically implemented according to the following steps: The permafrost top temperature model TTOP is used to calculate the annual average ground temperature of frozen soil. The annual average ground temperature of frozen soil is calculated as follows: Wherein, MAGT is the annual average ground temperature of frozen soil, n f is the ratio of freezing period air temperature to ground temperature; FDD is air freezing day index, r k is the ratio of thermal conductivity of frozen and thawed soil, n t is the ratio of air temperature to ground temperature during the melting period, TDD is the air melting day index, and τ is the number of days in a year.

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