Add wet deposition (#10)

* Dry deposition

* Finish Unit Tests

* Modify Project.toml

* Modifying Project.toml

* remove ModelingToolkit dependency

* Add package for test files

* Add wet deposition

* Change Unit Test

src/DepositionMTK.jl

@@ -5,5 +5,6 @@ using StaticArrays
 
 include("wesley1989.jl")
 include("dry_deposition.jl")
+include("wet_deposition.jl")
 
 end

src/wet_deposition.jl

@@ -0,0 +1,40 @@
+export WetDeposition
+
+"""
+Calculate wet deposition based on formulas at
+www.emep.int/UniDoc/node12.html.
+Inputs are fraction of grid cell covered by clouds (cloudFrac),
+rain mixing ratio (qrain), air density (ρ_air [kg/m3]),
+and fall distance (Δz [m]).
+Outputs are wet deposition rates for PM2.5, SO2, and other gases
+(wdParticle, wdSO2, and wdOtherGas [1/s]).
+"""
+function WetDeposition(cloudFrac, qrain, ρ_air, Δz)
+    A = 5.2u"m^3/kg/s"          # m3 kg-1 s-1; Empirical coefficient
+	E = 0.1           # size-dependent collection efficiency of aerosols by the raindrops
+	wSubSO2 = 0.15   # sub-cloud scavanging ratio
+	wSubOther = 0.5  # sub-cloud scavanging ratio
+	wInSO2 = 0.3     # in-cloud scavanging ratio
+	wInParticle = 1.0 # in-cloud scavanging ratio
+	wInOther = 1.4   # in-cloud scavanging ratio
+	ρwater = 1000.0u"kg*m^-3"   # kg/m3
+	Vdr = 5.0u"m/s"        # raindrop fall speed, m/s
+
+    # precalculated constant combinations
+	AE = A * E
+	wSubSO2VdrPerρwater = wSubSO2 * Vdr / ρwater
+	wSubOtherVdrPerρwater = wSubOther * Vdr / ρwater
+	wInSO2VdrPerρwater = wInSO2 * Vdr / ρwater
+	wInParticleVdrPerρwater = wInParticle * Vdr / ρwater
+	wInOtherVdrPerρwater = wInOther * Vdr / ρwater
+
+    # wdParticle (subcloud) = A * P / Vdr * E; P = QRAIN * Vdr * ρgas => wdParticle = A * QRAIN * ρgas * E
+	# wdGas (subcloud) = wSub * P / Δz / ρwater = wSub * QRAIN * Vdr * ρgas / Δz / ρwater
+	# wd (in-cloud) = wIn * P / Δz / ρwater = wIn * QRAIN * Vdr * ρgas / Δz / ρwater
+
+    wdParticle = qrain * ρ_air * (AE + cloudFrac*(wInParticleVdrPerρwater/Δz))
+	wdSO2 = (wSubSO2VdrPerρwater + cloudFrac*wSubSO2VdrPerρwater) * qrain * ρ_air / Δz
+	wdOtherGas = (wSubOtherVdrPerρwater + cloudFrac*wSubOtherVdrPerρwater) * qrain * ρ_air / Δz
+
+    return wdParticle, wdSO2, wdOtherGas
+end

test/runtests.jl

@@ -9,4 +9,8 @@ using Test, SafeTestsets
     @safetestset "wesely1989_test.jl" begin
         include("wesely1989_test.jl")
     end
-end
+
+    @safetestset "wetdep_test.jl" begin
+        include("wetdep_test.jl")
+    end
+end

test/wetdep_test.jl

@@ -0,0 +1,8 @@
+using DepositionMTK
+using Test,Unitful
+
+@testset "unit" begin
+    @test unit(WetDeposition(0.5,0.5,1.204u"kg*m^-3",1u"m")[1]) == u"s^-1"
+    @test unit(WetDeposition(0.5,0.5,1.204u"kg*m^-3",1u"m")[2]) == u"s^-1"
+    @test unit(WetDeposition(0.5,0.5,1.204u"kg*m^-3",1u"m")[3]) == u"s^-1"
+end