High-order long wave radiation transmission calculation method suitable for mesoscale mode

Abstract

The invention discloses a high-order long-wave radiation transmission calculation method suitable for a mesoscale mode, which adopts a four-stream method (second order) to calculate long-wave radiation, retains forward scattering effects in four Gaussian point directions, and specifically comprises the following steps: defining four Gaussian points and Gaussian point weights corresponding to the four Gaussian points; and applying the Gaussian points and the weights thereof to a calculation equation of long-wave radiation transmission, converting the calculation equation into a radiation transmission model containing contribution of four Gaussian points through a four-stream method, and calculating to obtain upward and downward radiation fluxes according to the radiation transmission model, thereby improving the calculation precision of long-wave radiation transmission and improving the calculation accuracy of long-wave radiation transmission. And the calculation efficiency of the mesoscale mode is considered, so that the problem of low precision of the current calculation method is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of long-wave radiation transmission calculation of mesoscale modes, and in particular to a high-order long-wave radiation transmission calculation method suitable for mesoscale modes. Background Art

[0002] Mesoscale models play an important role in meteorological research, especially in simulating and predicting severe weather such as sandstorms and blizzards. Such models can capture the occurrence, development and structural evolution of atmospheric mesoscale systems, providing an important scientific basis for meteorological forecasts and services.

[0003] The radiation process is a key physical process in numerical models and is of great significance for simulating the energy balance of the atmospheric system and climate change. As part of the radiation process, longwave radiation has a significant impact on the energy exchange between the atmosphere and the surface. Therefore, accurately calculating longwave radiation transmission in mesoscale models is an important part of improving simulation accuracy and forecasting capabilities.

[0004] Among them, the azimuth-averaged longwave radiation transfer equation under the plane-parallel atmosphere is:

[0005]

[0006] Where I(τ,μ), τ, μ, ω are the radiation intensity, optical depth, zenith angle cosine and single scattering albedo respectively. P(μ,μ') is the azimuthally averaged scattering phase function. B(τ) is the emitted Planck function.

[0007] In previous mesoscale models, the long-wave scattering effect was ignored and the above equation was simplified to

[0008]

[0009] In the previous models, the second-order method (first order) was mostly used to calculate the long-wave radiation, and the equation was

[0010]

[0011] The two Gaussian points are μ1=-μ -1 =0.6024096,

[0012] The weight of the Gaussian point is a ±1 =1.0

[0013] The final calculated radiation flux is F ↓ (τ)=2πμ -1 I ↓ ,F ↑ (τ)=2πμ +1 I ↑

[0014] Based on the above, the calculation accuracy of this method is low. Summary of the invention

[0015] The purpose of the present invention is to provide a high-order long-wave radiation transmission calculation method suitable for mesoscale modes, so as to solve the problem of low accuracy of the current calculation method mentioned in the above background technology.

[0016] To achieve the above object, the present invention provides the following technical solution: a method for calculating high-order long-wave radiation transmission suitable for mesoscale mode, which adopts a four-stream method (second order) to calculate long-wave radiation while retaining the forward scattering effect in the direction of four Gaussian points, and specifically comprises the following steps:

[0017] a) Considering the forward scattering, the azimuth-averaged long-wave radiation transfer equation under the plane-parallel atmosphere can be simplified to:

[0018]

[0019] b) Define four Gaussian points and their corresponding Gaussian point weights, where the four Gaussian points are μ1=-μ -1 =0.2113248, μ2=-μ -2 =0.7886752, and the corresponding Gaussian point weight is a ±1 =a ±2 =0.5;

[0020] c) applying the Gaussian points and their weights to a calculation equation for long-wave radiation transmission, and converting the calculation equation into a radiation transmission model including contributions from four Gaussian points by a four-stream method;

[0021] d) According to the radiation transfer model, the upward and downward radiation fluxes are calculated, and the calculation formula is:

[0022]

[0023] The final calculated upward and downward radiation flux is:

[0024] F ↓ (τ)=2π(a1μ -1 I1 ↓ +a2μ -2 I2 ↓ )

[0025] F ↑ (τ)=2π(a1μ +1 I1 ↑ +a2μ +2 I2 ↑ )

[0026] Among them, the method improves the calculation accuracy of long-wave radiation transmission by retaining the forward scattering effect in the direction of four Gaussian points, while taking into account the calculation efficiency of the mesoscale model.

[0027] Furthermore, the method is applied to the mesoscale numerical model and includes the following components:

[0028] a) Gas optical thickness calculation part (GASABS), which is used to calculate the gas optical thickness of 16 long-wave bands and define a function from transparent to opaque (with a value range of 0-1) based on the diffusion factor and gas optical thickness of the four-stream scheme, and convert the function into an integer as an index number to find the tau conversion function and transmittance in the lookup table;

[0029] b) Radiative transfer calculation part (RTRN), which is used to calculate the upward flux, downward flux and heating rate, where the angle of the angle integration and the corresponding Gaussian weight value adopt the four-flow method, which specifically includes the following processes:

[0030] i) Calculate the cloud optical thickness and cloud absorptivity layer by layer, and find the gas optical thickness according to the lookup table;

[0031] ii) Calculate the Planck function;

[0032] iii) Simulate the downward transmission flux and calculate the downward radiation flux of clear sky and full sky layer by layer;

[0033] iv) Simulate the upward transmission flux and calculate the upward radiation flux of clear sky and full sky layer by layer;

[0034] v) Calculate the long-wave heating rate of each layer.

[0035] Further, the lookup table in the gas optical thickness calculation part (GASABS) is established based on the pre-calculated gas optical thickness, tau conversion function and transmittance data under different conditions to facilitate fast lookup and calculation.

[0036] Furthermore, the radiation transfer calculation part (RTRN) takes into account the scattering and absorption effects of clouds, atmospheric gases and the ground surface on long-wave radiation during the calculation process, thereby improving the accuracy and applicability of the calculation results.

[0037] Furthermore, this method is applicable to mesoscale numerical models and can provide high-precision longwave radiation data support for mesoscale weather forecasting, climate simulation and atmospheric environment research.

[0038] Beneficial effects:

[0039] The present invention uses the four-stream method (second order) to calculate long-wave radiation in the mesoscale model, while retaining the forward scattering effects in the directions of four Gaussian points, which not only improves the calculation accuracy of long-wave radiation transmission, but also takes into account the calculation efficiency of the mesoscale model. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0041] The drawings described below are only related to some embodiments of the present invention, but are not intended to limit the present invention.

[0042] In the attached picture:

[0043] Figure 1 It is a schematic diagram of the gas optical thickness calculation part and the radiation transmission calculation part of an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] The present invention provides the following technical solution: a method for calculating high-order long-wave radiation transmission applicable to a mesoscale mode, which adopts a four-stream method (second order) to calculate long-wave radiation while retaining the forward scattering effect in the directions of four Gaussian points, and specifically comprises the following steps:

[0046] a) Considering the forward scattering, the azimuth-averaged long-wave radiation transfer equation under the plane parallel atmosphere can be simplified to:

[0047]

[0048] b) Define four Gaussian points and their corresponding Gaussian point weights, where the four Gaussian points are μ1=-μ -1 =0.2113248, μ2=-μ -2 =0.7886752, and the corresponding Gaussian point weight is a ±1 =a ±2 =0.5;

[0049] c) applying the Gaussian points and their weights to a calculation equation for long-wave radiation transmission, and converting the calculation equation into a radiation transmission model including contributions from four Gaussian points by a four-stream method;

[0050] d) According to the radiation transfer model, the upward and downward radiation fluxes are calculated, and the calculation formula is:

[0051]

[0052] The final calculated upward and downward radiation flux is:

[0053] F ↓ (τ)=2π(a1μ -1 I1 ↓ +a2μ -2 I2 ↓ )

[0054] F ↑ (τ)=2π(a1μ +1 I1 ↑ +a2μ +2 I2 ↑ )

[0055] Among them, the method improves the calculation accuracy of long-wave radiation transmission by retaining the forward scattering effect in the direction of four Gaussian points, while taking into account the calculation efficiency of the mesoscale model.

[0056] Furthermore, the scheme is used in the mesoscale model. Here, the RRTM radiation scheme of the WRF3.9.1 model is taken as an example. The transmission process in the radiation scheme is changed from a two-stream scheme to a four-stream scheme, and the forward scattering effect of the gas is added. The modification process is as follows:

[0057] 1). The modified program is phys / module_ra_rrtm_yq.F, which mainly modifies the `GASABS` function and the `RTRN` function in the rrtm scheme;

[0058] 2). Modified the function calling process in phys / module_radiation_driver.F;

[0059] 3). Modified the calling process of the function in phys / module_physics_init.F;

[0060] 4). Modified the registry Registry / Registry.EM_COMMON and added the `rrtmscheme_yq` package option;

[0061] 5). Other files related to compilation and calling, including:

[0062] *Registry / Registry.CONVERT

[0063] *Registry / Registry.NMM

[0064] *main / depend.common

[0065] *phys / Makefile

[0066] *share / module_check_a_mundo.F

[0067] *phys / module_physics_init.F

[0068] Here’s how to use the new solution:

[0069] During the compilation process, modify the namelist.input file and select the corresponding radiation scheme option. The modified scheme is the long wave scheme, so only "ra_lw_physics" needs to be modified. This scheme can be coupled with any other short wave scheme. Currently, it is recommended to use it with the Dudhia short wave scheme.

[0070] &physics

[0071] ra_lw_physics=66

[0072] ra_sw_physics=1

[0073] The new solution mainly includes the following two parts in practical application:

[0074] a) Gas optical thickness calculation part (GASABS), which is used to calculate the gas optical thickness of 16 long-wave bands and define a function from transparent to opaque (with a value range of 0-1) based on the diffusion factor and gas optical thickness of the four-stream scheme, and convert the function into an integer as an index number to find the tau conversion function and transmittance in the lookup table;

[0075] b) Radiative transfer calculation part (RTRN), which is used to calculate the upward flux, downward flux and heating rate, where the angle of the angle integration and the corresponding Gaussian weight value adopt the four-flow method, which specifically includes the following processes:

[0076] i) Calculate the cloud optical thickness and cloud absorptivity layer by layer, and find the gas optical thickness according to the lookup table;

[0077] ii) Calculate the Planck function;

[0078] iii) Simulate the downward transmission flux and calculate the downward radiation flux of clear sky and full sky layer by layer;

[0079] iv) Simulate the upward transmission flux and calculate the upward radiation flux of clear sky and full sky layer by layer;

[0080] v) Calculate the long-wave heating rate of each layer;

[0081] And provide the program implementation of these two parts, namely GASABS function (calculate gaseous optical depths) and RTRN function (do the radiative transfer calculation, for both clear and cloudy columns), GASABS function is as follows:

[0082]

[0083]

[0084]

[0085] The RTRN function is as follows:

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096] The lookup table in the gas optical thickness calculation part (GASABS) is established based on the pre-calculated gas optical thickness, tau conversion function and transmittance data under different conditions for fast lookup and calculation.

[0097] Among them, the radiation transfer calculation part (RTRN) takes into account the scattering and absorption effects of clouds, atmospheric gases and the ground surface on long-wave radiation during the calculation process, thereby improving the accuracy and applicability of the calculation results.

[0098] Among them, this method is suitable for mesoscale numerical models and can provide high-precision longwave radiation data support for mesoscale weather forecasting, climate simulation and atmospheric environment research.

[0099] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating high-order long-wave radiation transfer suitable for mesoscale modes, characterized in that: The method uses the four-stream method (second order) to calculate the long-wave radiation while retaining the forward scattering effect in the direction of four Gaussian points. Specifically, it includes the following steps: a) Considering the forward scattering, the azimuth-averaged long-wave radiation transfer equation under the plane-parallel atmosphere can be simplified to: b) Define four Gaussian points and their corresponding Gaussian point weights, where the four Gaussian points are μ1=-μ -1 =0.2113248, μ2=-μ -2 =0.7886752, and the corresponding Gaussian point weight is a ±1 =a ±2 =0.5; c) applying the Gaussian points and their weights to a calculation equation for long-wave radiation transmission, and converting the calculation equation into a radiation transmission model including contributions from four Gaussian points by a four-stream method; d) According to the radiation transfer model, the upward and downward radiation fluxes are calculated, and the calculation formula is: The final calculated upward and downward radiation flux is: F ↓ (τ)=2π(a1μ -1 I1 ↓ +a2m -2 I2 ↓ ) F ↑ (τ)=2π(a1μ +1 I1 ↑ +a2m +2 I2 ↑ ) Among them, the method improves the calculation accuracy of long-wave radiation transmission by retaining the forward scattering effect in the direction of four Gaussian points, while taking into account the calculation efficiency of the mesoscale model.

2. The method for calculating high-order long-wave radiation transmission applicable to mesoscale models according to claim 1, characterized in that: The method applied to mesoscale numerical models includes the following components: a) Gas optical thickness calculation part (GASABS), which is used to calculate the gas optical thickness of 16 long-wave bands and define a function from transparent to opaque (with a value range of 0-1) based on the diffusion factor and gas optical thickness of the four-stream scheme, and convert the function into an integer as an index number to find the tau conversion function and transmittance in the lookup table; b) Radiative transfer calculation part (RTRN), which is used to calculate the upward flux, downward flux and heating rate, where the angle of the angle integration and the corresponding Gaussian weight value adopt the four-flow method, which specifically includes the following processes: i) Calculate the cloud optical thickness and cloud absorptivity layer by layer, and find the gas optical thickness according to the lookup table; ii) Calculate the Planck function; iii) Simulate the downward transmission flux and calculate the downward radiation flux of clear sky and full sky layer by layer; iv) Simulate the upward transmission flux and calculate the upward radiation flux of clear sky and full sky layer by layer; v) Calculate the long-wave heating rate of each layer.

3. The high-order long-wave radiation transmission calculation method applicable to mesoscale mode according to claim 2 is characterized in that: The lookup table in the gas optical thickness calculation part (GASABS) is established based on the pre-calculated gas optical thickness, tau transfer function and transmittance data under different conditions to facilitate fast lookup and calculation.

4. The method for calculating high-order long-wave radiation transmission applicable to mesoscale models according to claim 2, characterized in that: The radiation transfer calculation part (RTRN) takes into account the scattering and absorption effects of clouds, atmospheric gases and the ground surface on long-wave radiation during the calculation process, thereby improving the accuracy and applicability of the calculation results.

5. A high-order long-wave radiation transmission calculation method applicable to mesoscale modes according to any one of claims 1 to 4, characterized in that: This method is applicable to mesoscale numerical models and can provide high-precision longwave radiation data support for mesoscale weather forecasting, climate simulation and atmospheric environment research.

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