Fluxes of Fine Particles Over a Semi-Arid Pine Forest: Possible Effects of a Complex Terrain

Figures & data

FIG. 1 The diurnal cycle (30 min averaged bins) of the particle size distribution for a week during autumn days measured by the GRIMM OPC at the Yatir forest. The color scale depicts log (dN/dlogD_p) for particle concentrations in particles L ⁻¹. (Color figure available online.)

TABLE 1 Average values of critical parameters for day hours (7:00–15:00) at the Yatir station. The bracketed values are the standard deviation from the mean, or the interquartile range (IQR) of the median. A total of 901 half-hour measurements were collected during the campaign

Size (nm)	250–280	280–300	300–350	350–400	400–450	450–500	500–580	580–650
% of data points of Vd > 0	44	46	45	41	38	37	31	23
Mean and std of Vd > 0 (mm s^−1)	3.8 (4.5)	4.8 (5.8)	5.7 (7.1)	7.0 (8.5)	6.8 (8.2)	6.4 (7.3)	5.2 (5.6)	5.1 (5.1)
Mean and std of Vd < 0 (mm s^−1)	−2.1 (2.4)	−2.9 (3.1)	−3.1 (3.1)	−4.2 (4.8)	−6.2 (7.6)	−7.9 (9.4)	−8.3 (10.9)	−11.5 (16.0)
Median concentration (cm ^−3)	48	25	21	10	3	1	1	0.7
Median u * and IQR (m s^−1)	0.53 (0.30)
Median and IQR of wind speed (m s^−1)					−51 (94)
Median and IQR of L (m)					2.4 (1.5)
Mean sensible heat and std (Wm^−2)					281 (133)
T° (K)					301 (4)

FIG. 2 Diurnal cycle of the half hour mean values of (a) friction velocity and (b) Obukhov length averaged over the full autumn day's data set. (Color figure available online.)

FIG. 3 Dependence of daytime deposition velocity on wind direction (15° sections) at the Yatir station. Data points and bars are the mean deposition velocities and standard deviations per 15° section over the full autumn days data set. The horizontal black (green) line marks zero deposition velocity. (Color figure available online.)

FIG. 4 Diurnal cycle of the half hour averaged deposition velocity during autumn days. Data points are displayed for downward fluxes (V_d > 0) by a solid (blue) line, upward fluxes (V_d < 0) by a dotted (red) line, and their sum by a dashed line (green) and exclude the westerly wind directions (225°–360°). Note the change in Y-scale between the upper and lower panels. (Color figure available online.)

FIG. 5 (a) V_d as a function of the friction velocity for size bin 250–280 nm. The open (red) circles represent the mean and standard deviation values (binned in 0.2 increments). V_d/ u _* (b) and V_d (c) as a function of particle diameter between 250 nm and 650 nm during autumn days. Data points are averaged for day hours (07:00–15:00), V_d > 0 and exclude the westerly wind directions (225–360°). (Color figure available online.)

FIG. 6 Mean values of half hourly V_d/ u _* vs. L ⁻¹ for size bins 250–280 nm, 350–400 nm, and 580–650 nm (Binned in 0.01 increments). Data points are for day hours, V_d > 0 and exclude the westerly wind directions (225–360°). The solid (red) lines show the modified parameterization equation (Equation (5)) for these three size bins following Gallagher et al. (1997). The equation coefficient (k₁) for each size bin is 0.005 as determined by the match of the parameterization (Equation (5)) to the Yatir data for the smallest size bin 250–280 nm. (Color figure available online.)

TABLE 2 Selected averaged deposition velocity values of particles in the accumulation mode over coniferous forests. Upward fluxes were (a) included, (b) not included, or (c) unknown (or not applicable) in the averaging of deposition velocities

Canopy (height in m)	dp (μm)	u * (m·s^−1)	Vd (mm·s^−1)	Reference	LAI
Pine (10.5)	0.25–0.28	0.65	3.8 ± 4.5 (b)	This Study	1–1.5
Pine (9)	0.5–1	(–)	4.3 (c)	(Lorenz and Murphy 1989)	6–12
Pine (15)	0.05–0.5	0.60	7.0 (c)	(Lamaud et al. 1994)	3
Pine (8)	0.44–0.54	(–)	6.1 (a)	(Vong et al. 2010)	5.1
Spruce (0.45)	0.82	0.45	5.0 (c)	(Ould-Dada et al. 2002)	3.2
Spruce (30)	0.5–1	(–)	15 ± 40 (c)	(Gravenhorst 1989)	(–)
Spruce (17)	0.3–0.5	0.15–0.75	0.3–16.6 (a)	(Gallagher et al. 1997)	10.3
Hardwood and coniferous (–)	0.23–0.40	0.2–0.80	0. 5–1 (a)	(Gordon et al. 2011)	(–)

Gallagher , M. W. , Beswick , K. M. , Duyzer , J. , Westrate , H. , Choularton , T. W. and Hummelshoj , P. 1997 . Measurements of Aerosol Fluxes to Speulder Forest Using a Micrometeorological Technique . Atmos. Environ. , 31 : 359 – 373 .

 Web of Science ®Google Scholar

Lorenz , R. and Murphy , C. E. 1989 . Dry Deposition of Particles to a Pine Plantation . Bound-Lay Meteorol. , 46 : 355 – 366 .

 Web of Science ®Google Scholar

Lamaud , E. , Brunet , Y. , Labatut , A. , Lopez , A. , Fontan , J. and Druilhet , A. 1994 . The Landes Experiment–Biosphere–Atmosphere Exchanges of Ozone and Aerosol-Particles above a Pine Forest . J. Geophys. Res.-Atmos. , 99 : 16511 – 16521 .

 Web of Science ®Google Scholar

Vong , R. J. , Vong , I. J. , Vickers , D. and Covert , D. S. 2010 . Size-Dependent Aerosol Deposition Velocities During BEARPEX’ 07 . Atmos. Chem. Phys. , 10 : 5749 – 5758 .

 Web of Science ®Google Scholar

Ould-Dada , Z. , Copplestone , D. , Toal , M. and Shaw , G. 2002 . Effect of Forest Edges on Deposition of Radioactive Aerosols . Atmos. Environ. , 36 : 5595 – 5606 .

 Web of Science ®Google Scholar

Gravenhorst , A. W. A. G. 1989 . “ Dry Deposition of Atmospheric Particles to an Old Spruce Stand ” . In Mechanisms and Effects of Air Pollutant Transfer into Forests , 77 – 86 . Kluwer Academic Publishers . Dordrecht, The Netherlands

 Google Scholar

Gordon , M. , Staebler , R. M. , Liggio , J. , Vlasenko , A. , Li , S. M. and Hayden , K. 2011 . Aerosol Flux Measurements Above a Mixed Forest at Borden, Ontario . Atmos. Chem. Phys. , 11 : 6773 – 6786 .

 Web of Science ®Google Scholar