LandEM Module 源码解析（一）- 引用关系

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LandEM (Land Emission Module)模块是一种正向微波辐射传输模式，适用于积雪，沙地，植被冠层等下垫面情况，本节就LandEM模块的结构和引用关系进行解析。

NESDIS_LandEM_Module头信息如下：

Module containing the NESDIS microwave land emissivity model
CREATION HISTORY:Written by:
Banghua Yan, QSS Group Inc.,Banghua.Yan@noaa.gov 01-Jun-2005
Fuzhong Weng, NOAA/NESDIS/ORA,Fuzhong.Weng@noaa.gov

全局变量和Module依赖

fortran

MODULE NESDIS_LandEM_Module
  ! -----------------
  ! Enviroment set up
  ! -----------------
  ! Module use
  USE Type_Kinds, ONLY: fp    			!!只使用fp变量
  USE Fundamental_Constants, ONLY: C_2  !!只使用C_2变量
  USE NESDIS_SnowEM_Parameters  		!! 引用SnowEM模块的相关配置
  ! Disable implicit typing
  IMPLICIT NONE

  ! ------------
  ! Visibilities
  ! ------------
  PRIVATE
  ! Procedures
  PUBLIC  :: NESDIS_LandEM
  ! Parameters
  PUBLIC :: ZERO
  PUBLIC :: POINT1
  PUBLIC :: POINT5
  PUBLIC :: ONE
  PUBLIC :: TWO 
  PUBLIC :: THREE
  PUBLIC :: FOUR
  PUBLIC :: PI
  PUBLIC :: EMISSH_DEFAULT
  PUBLIC :: EMISSV_DEFAULT
  
  PUBLIC :: ONE_TENTH
  PUBLIC :: HALF
  
  ! -----------------
  ! Module parameters
  ! -----------------
  REAL(fp), PARAMETER :: ZERO   = 0.0_fp
  REAL(fp), PARAMETER :: POINT1 = 0.1_fp
  REAL(fp), PARAMETER :: POINT5 = 0.5_fp
  REAL(fp), PARAMETER :: ONE    = 1.0_fp
  REAL(fp), PARAMETER :: TWO    = 2.0_fp
  REAL(fp), PARAMETER :: THREE  = 3.0_fp
  REAL(fp), PARAMETER :: FOUR   = 4.0_fp
  REAL(fp), PARAMETER :: PI     = 3.141592653589793238462643_fp
  REAL(fp), PARAMETER :: TWOPI  = TWO*PI
  REAL(fp), PARAMETER :: EMISSH_DEFAULT = 0.25_fp
  REAL(fp), PARAMETER :: EMISSV_DEFAULT = 0.30_fp

  REAL(fp), PARAMETER :: ONE_TENTH = POINT1
  REAL(fp), PARAMETER :: HALF      = POINT5
   
CONTAINS !! 子程序中的变量无需重新声明直接使用，变量值无需通过哑实结合传递。

主程序结构

基本上是顺序结构+分支结构，对于每一个模块，先计算介电常数，再计算反射率和透射率，最后进行辐射传输计算。

结构图

  flowchart TB
	subgraph NESDIS_LandEM
     in0[Freq,SMC,VegFrc,SoilT,SkinT,LAI,SoilType,VegType,SownDepth]-.->out0[MLSE_V,MLSE_H,Diel_Soil]
	end
	NESDIS_LandEM-->switch0
	switch0{SnowDepth>0.1?}

	switch0--True-->switch1
	switch0--False-->Canopy_Soil_procedure
	
	switch1{SnowDepth>10?}
	switch1--False-->Snow_Soil_procedure
	switch1--True-->Empirical_Snow_Algorithm
	
	subgraph Snow_Soil_procedure
     in2[Freq,SoilT,SMC,SoilType,SnowDepth]-.->out2[MLSE_V,MLSE_H...]
	end	

	subgraph Empirical_Snow_Algorithm
     in4[Freq,SkinT,SnowDepth]-.->out4[MLSE_V,MLSE_H]

	end	

	
	subgraph Canopy_Soil_procedure
	      in3[SMC,VegFrac,LAI,VegType,SoilT,SkinT]-.->out3[MLSE_V,MLSE_H]
	end	

%% actions

无积雪表面的辐射计算

Canopy_Soil_procedure这个分支是用于计算无积雪覆盖的”土壤-植被冠层-空气”三层介质模型的辐射传输计算。
其结构如下：

  flowchart TB

	subgraph Soil_Diel
	      in1[Freq,SMC,SoilT,SoilType]-.->out1[Diel_Soil]
	end	
	
out1-->in2
	
	subgraph Reflectance
	      in2[Diel_Air,Diel_Soil,theta]-.->out2[R23_V,R23_H]
	end	
	
out2-->in3
	

	subgraph Roughness_Reflectance
	      in3[Freq,theta,sigma,R23_V,R23_H]-.->out3[R23_V,R23_H]
	end	




	
	subgraph Canopy_Diel
	      in4[VegType,VWC,Veg_density]-.->out4[Diel_Leaf]
	end	
	
	out4-->in5
	
	subgraph Canopy_Optic
	      in5[Freq,LAI,Diel_Leaf,theta,Leaf_Thickness]-.->out5[Omega_V,Omega_H,Tau_V,Tau_H,Asymmetry_factor]
	end	
	
	out3-->in6
	out5-->in6
	
	subgraph Two_Stream_Solution
	      in6[Omegas,Taus,Reflects,SoilT,SkinT,Freq,Asymmes,theta]-.->out6[MLSE_V,MLSE_H]
	end