Where does the optically detectable aerosol in the European Arctic come from?

Figures & data

Fig. 1 Position of Ny-Ålesund, Sodankylä and NP-35 in March/April 2008.

Table 1. Number and wavelength range of the interference filters in the sun photometer types SP2H, SP1A and PFR

Type	SP2H	SP1A	PFR
Channels	14	17	4
Wavelengths	360–1050 nm	350–1090 nm	368–862 nm

Table

Spring (red)	-	March, April, May
Summer (green)	-	June, July
Autumn (blue)	-	August, September.

Fig. 2 Cluster allocation of ensemble trajectories at all heights (850, 700 and 500 hPa) for Ny-Ålesund 1995–2008.

Fig. 3 (a) Mean values and standard deviation of τ _500nm and α and (b) number of hourly mean AOD in different trajectory groups from Ny-Ålesund 1995–2008. Seasonal separation: spring – red; summer – green; autumn – blue.

Table

Spring (red)	-	March, April, May
Summer (green)	-	June, July, August
Autumn (blue)	-	September, October, November,February.

Fig. 4 Cluster allocation of ensemble trajectories at all heights (850, 700 and 500 hPa) for Sodankylä 2004–2007.

Fig. 5 (a) Mean values and standard deviation of τ _500nm and α and (b) number of hourly mean AOD in different trajectory groups from Sodankylä 2004–2007. Seasonal separation: spring – red; summer – green; autumn – blue.

Fig. 6 (a) Clustering of the ensemble trajectories at all heights (850, 700, 500 hPa) from NP-35 between 14 March and 7 April, 2008, and (b) hourly mean of τ _500nm and α in the different trajectory groups and the group mean of τ _500nm and α.

Fig. 7 Monthly means of τ _500nm and α in Ny-Ålesund.

Fig. 8 Monthly means of τ _500nm and α in Sodankylä.

Fig. 9 Correlation between NAO-Index and monthly mean AOD in March (blue) and April (red) for Ny-Ålesund 1995–2008. Drawn are the monthly mean standard deviation and the linear regression of a) τ _500nm and b) α. The parameters of the regression, including the correlation coefficient and their confidence range, are shown in the legend.

Fig. 10 First five EOF of mean sea-level pressure of three periods: left – December, January and February (1995–2008); middle – March (1995–2008); right – April (1995–2008) and their variance in %. The white star marks the position of Ny-Ålesund, respectively Spitsbergen.

Table 2. Correlation coefficients and confidence range for the correlation between the principle components (PC) of the first five EOF MSLP DJF and the monthly mean τ _500nm of March and April in Ny-Ålesund (1995–2008)

	R
Month	1. EOF	2. EOF	3. EOF	4. EOF	5. EOF
March	−0.08±0.56	−0.16±0.55	−0.12±0.56	−0.27±0.53	−0.14±0.55
April	−0.08±0.59	−0.19±0.57	−0.05±0.59	−0.04±0.59	0.15±0.58

Table 3. Correlation coefficients and confidence range for the correlation between the principle components (PC) of the first five EOF MSLP March and April and the daily mean τ _500nm of March and April in Ny-Ålesund (1995–2008)

	March					April
	R					R
	1.EOF	2.EOF	3.EOF	4.EOF	5.EOF	1.EOF	2.EOF	3.EOF	4.EOF	5.EOF
0	0.41±0.22	0.36±0.29	0.05±0.26	0.02±0.26	−0.11±0.26	−0.03±0.20	0.0±0.20	0.17±0.19	0.17±0.19	−0.02±0.20
1	0.37±0.22	0.32±0.23	0.03±0.26	0.08±0.26	−0.10±0.26	−0.03±0.20	0.02±0.20	0.19±0.19	0.15±0.19	0.02±0.20
2	0.27±0.24	0.30±0.23	−0.05±0.26	0.06±0.26	−0.10±0.25	−0.03±0.20	0.03±0.20	0.19±0.19	0.15±0.19	0.05±0.20
3	0.19±0.25	0.32±0.23	−0.16±0.25	−0.03±0.25	−0.05±0.25	−0.05±0.20	0.07±0.20	0.19±0.19	0.14±0.19	0.04±0.20
4	0.13±0.24	0.34±0.22	−0.24±0.23	−0.13±0.24	0.04±0.25	−0.10±0.19	0.14±0.19	0.16±0.19	0.09±0.20	0.01±0.20
5	0.11±0.24	0.32±0.22	−0.23±0.23	−0.20±0.24	0.13±0.24	−0.10±0.20	0.20±0.19	0.16±0.19	−0.04±0.20	−0.05±0.2
6	0.12±0.24	0.29±0.22	−0.16±0.23	−0.18±0.23	0.20±0.23	−0.04±0.20	0.25±0.18	0.11±0.19	−0.16±0.19	−0.08±0.2
7	0.11±0.23	0.25±0.22	−0.10±0.23	−0.08±0.23	0.25±0.22	−0.01±0.20	0.26±0.18	0.02±0.20	−0.23±0.19	−0.09±0.2
8	0.10±0.23	0.17±0.22	−0.06±0.23	0.02±0.23	0.22±0.22	0.07±0.20	0.19±0.19	−0.02±0.20	−0.23±0.19	−0.10±0.2
9	0.11±0.22	0.12±0.22	−0.04±0.22	0.07±0.22	0.11±0.22	0.15±0.19	0.15±0.19	−0.06±0.20	−0.19±0.19	−0.11±0.1
10	0.12±0.22	0.10±0.22	−0.02±0.22	0.09±0.22	0.05±0.22	0.17±0.19	0.18±0.19	−0.11±0.19	−0.15±0.19	−0.05±0.2

Table 4. Correlation coefficients and confidence range between the measured τ _500nm/α in Ny-Ålesund, which were assigned a trajectory cluster, and the measured concentration of different atmospheric chemical components at Zeppelin

Matter	R(τ 500nm)	R(α)	Number of daily means	Period
(s)	0.506±0.144	0.124±0.191	103	1995–2008
(s)	0.070±0.193	0.160±0.189	103
(s)	0.185±0.186	0.148±0.188	105
Na^+(s)	0.028±0.192	−0.055±0.192	105
Mg^2+(s)	−0.014±0.192	−0.238±0.181	105
Ca^2+(s)	−0.020±0.192	−0.075±0.191	105
K^+(s)	−0.051±0.192	−0.019±0.192	105
Cl^− (s)	0.123±0.191	−0.272±0.180	103
SO2 (g)	0.052±0.192	−0.024±0.192	105
NH3 (g)	−0.259±0.179	0.202±0.184	105

g=gas, s=solid.

Table 5. Correlation coefficients and confidence range between the measured τ _500nm in Ny-Ålesund, which were assigned to a unique trajectory cluster, and the measured concentration of different atmospheric chemical components at Zeppelin

	R(τ 500nm)
Matter	1	2	3	4	5	6	7	8
(s)	0.174±0.436	0.765±0.218	0.761±0.291	0.180±1.095	0.421±0.570	0.379±0.407	0.573±0.329	0.460±0.631
(s)	0.040±0.449	0.567±0.355	0.013±0.693	−0.154±1.105	−0.345±0.611	0.161±0.463	−0.005±0.490	0.049±0.798
(s)	0.049±0.449	0.743±0.235	0.311±0.626	0.382±0.837	0.237±0.654	−0.008±0.475	0.694±0.254	0.601±0.511
Na^+(s)	−0.076±0.447	0.035±0.523	0.104±0.686	0.016±0.980	−0.367±0.600	−0.373±0.409	0.264±0.456	−0.227±0.759
Mg^2+(s)	−0.187±0.434	−0.088±0.520	0.134±0.681	−0.165±0.953	−0.167±0.674	−0.213±0.454	0.422±0.403	0.050±0.798
Ca^2+(s)	−0.139±0.441	0.096±0.519	−0.047±0.691	−0.263±0.912	0.021±0.693	0.053±0.474	0.110±0.484	0.014±0.800
K^+(s)	0.045±0.449	−0.179±0.507	0.265±0.644	−0.033±0.979	−0.391±0.587	−0.220±0.452	0.073±0.487	−0.726±0.378
Cl^−(s)	−0.068±0.448	−0.035±0.523	0.020±0.693	0.171±1.099	−0.194±0.667	0.060±0.474	0.300±0.446	0.033±0.799
SO2 (g)	0.201±0.432	−0.149±0.512	0.002±0.693	0.116±0.967	0.066±0.690	−0.103±0.470	−0.166±0.477	0.139±0.785
NH3 (g)	−0.049±0.449	−0.224±0.498	−0.197±0.666	−0.054±0.977	−0.471±0.539	−0.462±0.374	−0.492±0.372	−0.285±0.735
Number of daily means	20	15	9	5	9	18	17	7

g=gas, s=solid.

Fig. 11 Scatter plot of all hourly mean τ _500nm and α measured in Ny-Ålesund 1995–2008 and assigned to a trajectory cluster.