| 1. |
- Lihavainen, Heikki, et al.
(författare)
-
Observational signature of the direct radiative effect by natural boreal forest aerosols and its relation to the corresponding first indirect effect
- 2009
-
Ingår i: Journal of Geophysical Research. - : American Geophysical Union. - 0148-0227 .- 2156-2202. ; 114
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- By using a screened set of long-term aerosol measurement data, the contribution of natural boreal forest aerosols to the direct radiative effect (DRE) was observed at a remote continental site in northern Finland. Averaged over the summer season, the magnitude of this effect at the top of the atmosphere was estimated to be in the range -(0.37-0.74) W m(-2) in our study region and possibly somewhat higher over the whole boreal forest region. Globally, the DRE owing to boreal forest aerosols is much smaller than that owing to natural sea salt or dust aerosols, as well as direct radiative forcing by anthropogenic aerosols. We also updated the earlier estimates of the first indirect radiative effect (IRE) by natural boreal forest aerosols. We found that this IRE is likely to be substantially higher, perhaps more than an order of magnitude, than the corresponding DRE
|
|
| 2. |
- Tunved, Peter, et al.
(författare)
-
Aerosol characteristics of air masses in Northern Europe – influences of location, transport, sinks and sources
- 2005
-
Ingår i: Journal of Geophysical Research. - : American Physical Union. - 0148-0227 .- 2156-2202. ; 110:D7, s. D07201-
-
Tidskriftsartikel (refereegranskat)abstract
- Synoptic-scale air masses at different stations were classified following a definition based on Berliner Wetterkarte. This air mass classification has been related to 1 year of aerosol number size distributions measurements performed at four different stations extending from Aspvreten in Sweden (58.8 degrees N) to Pallas in northern Finland (68 degrees N). The air mass classification describes both class of air mass, based on the origin of the air mass, and character of air in terms of marine, mixed, and continental air masses. The aerosol size distribution properties were evaluated in relation to the air masses. Emphasis was put on the differences between marine, mixed, and continental character air masses. It is shown that continental air masses exceed marine and mixed character air masses both in number and mass concentration. Different classes of air masses were further associated with different aerosol size distribution properties. It is also shown that although serving as a somewhat good qualifier for the aerosol at individual stations, the air mass classification cannot be used to estimate the aerosol burden over large geographical areas. Instead, a sharp gradient was shown to exist between different stations, although aerosol properties were observed in equal air masses according to the definition by Berliner Wetterkarte. This gradient manifests as a south-northerly decrease in aerosol total number and volume, indicating that the aerosol properties including the aerosol size distribution are less conservative than the thermodynamic properties (e.g., pseudo-potential temperature and humidity profiles) that characterize the different air masses. Further, using a pseudo-Lagrangian approach, the aerosol turnover time was estimated for different sized aerosols in air moving from south to north (i.e., depletion of aerosols in air arriving from the continent). Turnover time of Aitken particles was found to be in the range of 1-2 days, while accumulation mode turnover time was estimated to be in the order of 2-3 days
|
|
| 3. |
|
|
| 4. |
- Väänänen, Riikka, et al.
(författare)
-
Analysis of particle size distribution changes between three measurement sites in Northern Scandinavia
- 2013
-
Ingår i: Nucleation and Atmospheric Aerosols - 19th International Conference. - : AIP. - 1551-7616 .- 0094-243X. - 9780735411524 ; 1527, s. 531-534
-
Konferensbidrag (refereegranskat)abstract
- Measured aerosol size distributions from three measurement stations and modeled air mass trajectory data were combined to study aerosol dynamics in the boreal forest zone in Northern Scandinavia. Three approaches were used: investigation of new particle formation events, analysis of air masses arriving from ocean to continent, and study of changes in the aerosol size distributions when air masses travel from one measurement site to another. The statistical analysis of air masses travelling either from the Atlantic Ocean to measurement sites or from one site to another showed that on average the condensational growth was present during the summer season, and it was not restricted only to the days when evident new particle formation was observed. The rate of this average apparent growth of particle diameter was 3-7 times smaller than the growth rate of nucleation mode particles during the new particle formation events.
|
|
