H13-92 Estimate of acid deposition through fog using numerical models in the Kinki Region of Japan Hikari Shimadera 1, 2 , Akira Kondo 1 , Akikazu Kaga 1 , Kundan Lal Shrestha 1, 2 , Yoshio Inoue 1 1 Graduate School of Engineering, Osaka University 2 JSPS Research Fellow
Introduction 1 Background Acid deposition has been widely recognized as a regional environmental problem, and has caused damage to sensitive ecosystems Fog deposition can lead to considerable amount of acid deposition in mountainous forest areas – Ionic concentrations in fog are much higher than those in rain – Fog water deposition through interception by vegetation can be an important part of the hydrologic budget of forests Few fog monitoring sites exist and fog is highly variable according to region
Introduction 2 Objective Establish a method to estimate spatial distribution of the amount of acid deposition including fog deposition Approach 2-dimensional model to predict fog water deposition (FDM) was developed and verified FDM was applied with meteorology and air quality model to estimate acid deposition in Kinki Region of Japan
2-dimensional Fog Deposition Model (FDM) 3 Description of FDM Features of FDM Comparison of FDM with field measurement
Description of FDM 4 Equation of mean motion u u K C a z u u M d S t t z K M : eddy diffusivity, C d : drag coefficient, a S : surface area density SAI ˆ a z a ( Z ) for Z z h , 0 Z 1 S fc h fc 1 Z 1 1 1 ˆ ˆ 2 2 a ( Z ) a exp Z Z , a ( Z ) dZ 1 m m 1 Z 2 2 0 m 2 1 1 4 for 1 Z 2 m 0 for 1 SAI : surface area index (= LAI + NLAI ), h fc : height of forest canopy λ : parameter by Kondo and Arakashi (1976, Boundary-Layer Meteorol. , 10 (3), 255)
Description of FDM 5 Equation of liquid water content of fog ( LWC ) LWC LWC LWC LWC u w K Dep M t x z z z Dep f a z u LWC L L IM f L : portion of the effective leaf area, a L : leaf area density, ε IM : impaction efficiency of fog droplet 2 d u St W p , St IM St 9 d A L α , β, γ : 5.0, 1.05 and 1 for needle leaf 0.5, 1.90 and 5 for broad leaf d L : characteristic leaf length (=0.001 m for needle leaf and 0.030 m for broad leaf) d p : mean diameter of fog droplet (= 17.03 LWC × 10 -3 +9.72 × 10 -6 m) by Katata et al. (2008, J Appl. Meteorol. Climatol. , 47 (8), 2129)
Description of FDM 6 z = Δz × nz u bc λ = 1 λ = 2 λ = 3 λ = 4 λ = 5 forest area LWC bc FR F z = h fc non-forest area 1- FR F z = 0 x = Δx × nx x = 0 SAI / h fc a S ( z ) u ( z ) – Forests are allocated to the computational area from its horizontal edges according to fraction of forest ( FR F ) – Vertical distributions of a S ( z ) vary with λ , and u(z) vary with a S ( z ) – FDM predicts steady state fog deposition velocity ( V Dep = fog water deposition flux/ LWC bc ) for each run – FDM configuration λ = 3, NLAI = 0.5, Δx = 40 m, nx = 50, Δz = 1.5 m, nz = 30
Features of FDM 7 Sensitivity to parameters 1.0E+00 – FDM configuration LWC bc = 0.0003 kg m -3 , LAI 1.0E-01 Mean V Dep (m s -1 ) 0.1 h fc = 18 m, 0.3 FR F = 0.96, 1.0E-02 1 needle-leaved forest 3 10 1.0E-03 1.0E-04 10 0 2 4 6 8 10 u bc (m s -1 ) – Since ε IM increases with u , V Dep increases with u bc – When forest areas are thin, V Dep considerably increases with LAI – When forest areas are dense, V Dep does not very increase or can decrease with an increase in LAI because of large drag force
Features of FDM 8 Horizontal distribution of V Dep – FDM configuration 1.2 FR F 1.0 u bc = 10 m s -1 , V Dep (m s -1 ) 0.8 0.24 LWC bc = 0.0003 kg m -3 , 0.6 0.48 h fc = 18 m, 0.4 0.96 FR F = 0.96, 0.2 LAI = 3, 0.0 2000 400 800 1200 1600 2000 needle-leaved forest x (m) u bc – V Dep at the windward edge of forest is the largest in every cases largest V Dep – Ratio of ( V dep at edge/ V Dep in inner forest) increases with increasing width of the gap between forest areas x = 0 x = 2000 m
Comparison with field measurement 9 Measurement site – Burkard et al. (2003, Atmos. Environ. , 37 (21), 2979) measured the turbulent fog water flux by the eddy covariance method at 45 m on a tower (15 m above the forest canopy) – The measurement site is situated at 690 m on the south slope of the Lägeren Mountain, ~15 km northwest of Zurich, Switzerland – The vegetation cover around the site is mixed forest dominated by beech and Norway spruce Eddy covariance measurement Lägeren forest (cited from http://www.gl.ethz.ch/infrastructure/research_sites/switzerland/laegeren) – FDM configuration h fc = 30 m, LAI derived from dataset of MODIS LAI product, FR F = 1, 50 % of needle-leaved and 50 % of broad-leaved trees
Comparison with field measurement 10 Fog water flux and V dep FDM Measurement FDM Measurement 1.0E+00 8 Accumlated turbulent fog water flux (mm) 1.0E-01 6 V Dep (m s -1 ) 1.0E-02 4 1.0E-03 2 0 1.0E-04 Sep. Oct. Nov. Dec. Jan. Feb. Mar. 0 2 4 6 8 10 2001 2002 u bc (m s -1 ) – Total fog water flux in FDM (7.3 mm) agreed with that in the measurement (7.4 mm) – As V Dep in FDM strongly depend on u , FDM underestimated fog water flux when measured V Dep was large despite low u bc , and overestimated when measured V Dep was small despite high u bc
Estimate of fog deposition in Kinki Region of Japan 11 Modeling system Modeling domain Air quality prediction in March 2005 Forest data Fog water deposition and corresponding NO Y deposition in March 2005 * NO Y = NO + NO 2 + NO 3 + N 2 O 5 + HNO 3 + HONO + aerosol nitrate
Modeling system NCEP.FNL (D1) Emission Data MM5 v3.7 GPV-MSM (D2) Japan: EAGrid2000-JAPAN (The 5 th-Generation NCAR/ Other Asian countries Penn State M esoscale M odel) Anthropogenic: 2006 INTEX-B Asia emission NH 3 : REAS 2005 prediction Biogenic VOCs: EAGrid2000 Meteorology Field Biomass Burning: Streets et al. (2003) Volcanic SO 2 : Observed value at Miyakejima Andres and Kasgnoc (1998) MCIP v3.4 CMAQ v4.7 (Meteorology-Chemistry Emission Processor (The U.S. EPA’s C ommunity Interface Processor) M ultiscale A ir Q uality model) CCTM CMAQ default Ionic concentration (CMAQ Chemical concentration profiles in fog water Forest data Transport Model) FDM Photolysis rate table Atmospheric concentration Fog deposition Dry/Wet deposition
MM5/CMAQ modeling domain 13 Elevation D4 [m] 100 200 300 D3 400 500 Mt. Rokko 600 700 D2 850 1000 1200 1500 2000 D1 Horizontal resolution – D1: 54km-grid cells (105 × 81) – D2: 18km-grid cells (72 × 72) – D3: 6km-grid cells (99 × 99) – D4: 2km-grid cells (126 × 126) for estimate of fog deposition Vertical resolution – 24 layers from surface to 100hPa (the middle height of the 1st and 2nd layers are ~15 and 50m)
Air quality prediction in March 2005 14 - concentrations Spatial distributions of monthly mean NO 3 - Aerosol NO 3 [μg m -3 ] 0.3 0.5 0.7 1.0 1.3 1.7 2.2 2.8 3.5 4.3 5.2 7.0 10.0 15.0 - in rain - in fog NO 3 NO 3 [μmol L -1 ] [μmol L -1 ] 5 5 7 7 10 10 13 13 17 17 22 22 28 28 35 35 43 43 52 52 70 70 100 100 150 150 250 250
Air quality prediction in March 2005 15 Comparisons of predictions with observations - in rain - Aerosol NO 3 NO 3 80 6 Prediction [μmol L -1 ] Prediction [μg m -3 ] 60 4 40 2 20 0 0 0 2 4 6 0 20 40 60 80 Observation [μg m -3 ] Observation [μmol L -1 ] - in fog at Mt. Rokko NO 3 Observation - in fog [μmol L -1 ] Prediction 1.E+4 1.E+3 1.E+2 1.E+1 NO 3 1.E+0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 Date of March 2005
Forest data 16 FR F Forest class LAI in March 2005 [m 2 m -2 ] 0.0 0.3 0.1 DN 0.6 0.2 EN 0.9 0.3 1.2 DB 0.4 1.5 0.5 1.8 EB 0.6 2.1 0.7 2.4 0.8 2.7 3.0 0.9 1.0 FR F , forest class and LAI were obtained from dataset of MLIT in Japan, MOE in Japan and MODIS LAI product Forest areas account for 65 % of the land areas and 95 % of the mountainous areas with elevation > 500 m Needle-leaved (DN + EN) forest account for 67 % of the forest area and broad-leaved (DB + EB) forest account 33 % Because March is before or at the beginning of the vegetation growing season, most of the forest areas tend to be thin North-eastern areas covered with deciduous broad-leaved (DB) forest show the lowest LAI
Fog water deposition in March 2005 17 Fog frequency Fog water deposition Rainfall [%] [mm] [mm] 10 1 1 40 4 2 80 8 3 120 4 12 5 160 16 6 220 22 8 280 28 10 360 36 12 450 45 15 Fog frequency, fog water deposition and rainfall generally increased with increasing elevation While fog frequency and rainfall were the highest in the north- eastern area dominantly covered with deciduous broad-leaved forest, fog water deposition was not due to the thin vegetation cover Ratios of (Fog water deposition/Rainfall) reached up to 23 % (mean = 3 %) in mountainous areas The ratio may change in the vegetation growing season
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