Correct δBGE truncation

src/Scattering/truncate_phase.jl

@@ -11,16 +11,15 @@ Returns the truncated aerosol optical properties as [`AerosolOptics`](@ref)
 - `mod` a [`δBGE`](@ref) struct that defines the truncation order (new length of greek parameters) and exclusion angle
 - `aero` a [`AerosolOptics`](@ref) set of aerosol optical properties that is to be truncated
 """
-function truncate_phase(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) where {FT}
+function truncate_phase_lowconf(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) where {FT}
     @unpack greek_coefs, ω̃, k = aero
     @unpack α, β, γ, δ, ϵ, ζ = greek_coefs
     @unpack l_max, Δ_angle =  mod
 
 
     # Obtain Gauss-Legendre quadrature points and weights for phase function:
     μ, w_μ = gausslegendre(length(β));
-    μ = convert.(FT,μ)
-    w_μ = convert.(FT,w_μ)
+
     # Reconstruct phase matrix elements:
     scattering_matrix, P, P² = reconstruct_phase(greek_coefs, μ; returnLeg=true)
 
@@ -50,7 +49,7 @@ function truncate_phase(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) wh
     # W₁₂ = Diagonal(w_μ[iμ]);
     # W₃₄ = Diagonal(w_μ[iμ]);
     # Julia backslash operator for least squares (just like Matlab);
-    cl = ((W₁₁ * A) \ (W₁₁ * y₁₁))   # B in δ-BGE (β)
+    cl = ((W₁₁ * A) \ (W₁₁ * y₁₁))   # B in δ-BGR (β)
     γᵗ = similar(cl); γᵗ[1:2] .=0
     ϵᵗ = similar(cl); ϵᵗ[1:2] .=0
     γᵗ[3:end] = ((W₁₂ * B) \ (W₁₂ * y₁₂))   # G in δ-BGE (γ)
@@ -70,14 +69,13 @@ function truncate_phase(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) wh
     c₀ = FT(cl[1]) # ( w_μ' * (P[:,1:l_max] * cl) ) / 2
 
     # Compute truncated greek coefficients:
-    βᵗ = cl / c₀                                    # Eq. 38a, B in δ-BGE (β)
+    βᵗ = cl / c₀                                    # Eq. 38a, B in δ-BGR (β)
     δᵗ = (δ[1:l_max] .- (β[1:l_max] .- cl)) / c₀    # Eq. 38b, derived from β
     αᵗ = (α[1:l_max] .- (β[1:l_max] .- cl)) / c₀    # Eq. 38c, derived from β
     ζᵗ = (ζ[1:l_max] .- (β[1:l_max] .- cl)) / c₀    # Eq. 38d, derived from β
 
     # Adjust scattering and extinction cross section!
     greek_coefs = GreekCoefs(αᵗ, βᵗ, γᵗ, δᵗ, ϵᵗ, ζᵗ  )
-    #@show typeof(greek_coefs)
 
     # C_sca  = (ω̃ * k);
     # C_scaᵗ = C_sca * c₀; 
@@ -87,3 +85,135 @@ function truncate_phase(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) wh
     return AerosolOptics(greek_coefs=greek_coefs, ω̃=ω̃, k=k, fᵗ=(FT(1) - c₀))
 end
 
+"""
+$(FUNCTIONNAME)(mod::δBGE, aero::AerosolOptics))
+
+Returns the truncated aerosol optical properties as [`AerosolOptics`](@ref) 
+- `mod` a [`δBGE`](@ref) struct that defines the truncation order (new length of greek parameters) and exclusion angle
+- `aero` a [`AerosolOptics`](@ref) set of aerosol optical properties that is to be truncated
+"""
+function truncate_phase(mod::δBGE, aero::AerosolOptics{FT}; reportFit=false) where {FT}
+    @unpack greek_coefs, ω̃, k = aero
+    @unpack α, β, γ, δ, ϵ, ζ = greek_coefs
+    @unpack l_max, Δ_angle =  mod
+
+    l_tr = l_max
+    # Obtain Gauss-Legendre quadrature points and weights for phase function:
+    μ, w_μ = gausslegendre(length(β));
+
+    # Reconstruct phase matrix elements:
+    scattering_matrix, P, P² = reconstruct_phase(greek_coefs, μ; returnLeg=true)
+
+    @unpack f₁₁, f₁₂, f₂₂, f₃₃, f₃₄, f₄₄ = scattering_matrix
+
+    # Find elements that exclude the peak (if wanted!)
+    iμ = findall(x -> x < cosd(Δ_angle), μ)
+
+    # Prefactor for P2:
+    fac = zeros(FT,l_tr);
+    for l = 2:l_tr - 1
+        fac[l + 1] = sqrt(FT(1) / ( ( l - FT(1)) * l * (l + FT(1)) * (l + FT(2)) ));
+    end
+
+    # Create subsets (for Ax=y weighted least-squares fits):
+    y₁₁ = view(f₁₁, iμ)
+    y₁₂ = view(f₁₂, iμ)
+    y₃₄ = view(f₃₄, iμ)
+
+    #= for β
+       Ax=b, where
+       Aᵢⱼ = ∑ₖ w_μₖ Pᵢ(μₖ)Pⱼ(μₖ)/f₁₁²(μₖ), xᵢ=cᵢ (as in Sanghavi & Stephens 2015), and
+       bᵢ  = ∑ₖ w_μₖ Pᵢ(μₖ)/f₁₁(μₖ)
+    =#   
+    A = zeros(l_tr, l_tr)
+    x = zeros(l_tr)
+    b = zeros(l_tr)
+
+    for i = 1:l_tr
+        b[i] = sum(w_μ.*P[:,i]./f₁₁)
+        A[i,i] = sum(w_μ.*(P[:,i]./f₁₁).^2)
+        for j = i+1:l_tr
+            A[i,j] = sum(w_μ.*P[:,i].*P[:,j]./(f₁₁.^2))
+            A[j,i] = A[i,j]
+        end
+    end
+    cl = A\b # Julia backslash operator for SVD (just like Matlab);
+    # B in δ-BGR (β)
+    if reportFit
+        println("Errors in δ-BGE fits:")
+        mod_y = convert.(FT, A * cl)
+        @show StatsBase.rmsd(mod_y, y₁₁; normalize=true)
+    end
+
+    #= for γ
+       Ax=b, where
+       Aᵢⱼ = ∑ₖ w_μₖ facᵢP²ᵢ(μₖ)facⱼP²ⱼ(μₖ)/f₁₂²(μₖ), xᵢ=gᵢ (as in Sanghavi & Stephens 2015), and
+       bᵢ  = ∑ₖ w_μₖ facᵢP²ᵢ(μₖ)/f₁₂(μₖ)
+    =#  
+    A = zeros(l_tr, l_tr)
+    x = zeros(l_tr)
+    b = zeros(l_tr)
+
+    for i = 3:l_tr
+        b[i] = fac[i]*sum(w_μ.*P²[:,i]./f₁₂)
+        A[i,i] = (fac[i])^2*sum(w_μ.*(P²[:,i]./f₁₂).^2)
+        for j = i+1:l_tr
+            A[i,j] = fac[i]*fac[j]*sum(w_μ.*P²[:,i].*P²[:,j]./(f₁₂.^2))
+            A[j,i] = A[i,j]
+        end
+    end
+    γᵗ = similar(cl); γᵗ[1:2] .=0
+    γᵗ[3:end] = A[3:end,3:end] \ b[3:end]   # G in δ-BGE (γ)
+
+    if reportFit
+        println("Errors in δ-BGE fits:")
+        mod_γ = convert.(FT, B * γᵗ[3:end])
+        @show StatsBase.rmsd(mod_γ, y₁₂; normalize=true)
+    end
+
+    #= for ϵ
+       Ax=b, where
+       Aᵢⱼ = ∑ₖ w_μₖ facᵢP²ᵢ(μₖ)facⱼP²ⱼ(μₖ)/f₁₂²(μₖ), xᵢ=eᵢ (as in Sanghavi & Stephens 2015), and
+       bᵢ  = ∑ₖ w_μₖ facᵢP²ᵢ(μₖ)/f₃₄(μₖ)
+    =#  
+    A = zeros(l_tr, l_tr)
+    x = zeros(l_tr)
+    b = zeros(l_tr)
+
+    for i = 3:l_tr
+        b[i] = fac[i]*sum(w_μ.*P²[:,i]./f₃₄)
+        A[i,i] = (fac[i])^2*sum(w_μ.*(P²[:,i]./f₃₄).^2)
+        for j = i+1:l_tr
+            A[i,j] = fac[i]*fac[j]*sum(w_μ.*P²[:,i].*P²[:,j]./(f₃₄.^2))
+            A[j,i] = A[i,j]
+        end
+    end
+
+    ϵᵗ = similar(cl); ϵᵗ[1:2] .=0
+    ϵᵗ[3:end] = A[3:end,3:end] \ b[3:end]   # E in δ-BGE (ϵ)
+
+    if reportFit
+        println("Errors in δ-BGE fits:")
+        mod_ϵ = convert.(FT, B * ϵᵗ[3:end])
+        @show StatsBase.rmsd(mod_ϵ, y₃₄; normalize=true)
+    end
+
+    # Integrate truncated function for later renormalization (here: fraction that IS still scattered):
+    c₀ = FT(cl[1]) # ( w_μ' * (P[:,1:l_max] * cl) ) / 2
+
+    # Compute truncated greek coefficients:
+    βᵗ = cl / c₀                                    # Eq. 38a, B in δ-BGR (β)
+    δᵗ = (δ[1:l_tr] .- (β[1:l_tr] .- cl)) / c₀    # Eq. 38b, derived from β
+    αᵗ = (α[1:l_tr] .- (β[1:l_tr] .- cl)) / c₀    # Eq. 38c, derived from β
+    ζᵗ = (ζ[1:l_tr] .- (β[1:l_tr] .- cl)) / c₀    # Eq. 38d, derived from β
+
+    # Adjust scattering and extinction cross section!
+    greek_coefs = GreekCoefs(αᵗ, βᵗ, γᵗ, δᵗ, ϵᵗ, ζᵗ  )
+
+    # C_sca  = (ω̃ * k);
+    # C_scaᵗ = C_sca * c₀; 
+    # C_ext  = k - (C_sca - C_scaᵗ);
+    #@show typeof(ω̃), typeof(k),typeof(c₀)
+    # return AerosolOptics(greek_coefs = greek_coefs, ω̃=C_scaᵗ / C_ext, k=C_ext, fᵗ = 1-c₀) 
+    return AerosolOptics(greek_coefs=greek_coefs, ω̃=ω̃, k=k, fᵗ=(FT(1) - c₀))
+end