排序方式： 共有12条查询结果，搜索用时 15 毫秒
1.
By T. THUM T. AALTO T. LAURILA M. AURELA J. HATAKKA A. LINDROTH T. VESALA 《Tellus. Series B, Chemical and physical meteorology》2009,61(5):701-717
We studied the commencement and finishing of the growing season using different air temperature indices, the surface albedo, the chlorophyll fluorescence (Fv/Fm) and the carbon dioxide (CO2 ) tropospheric concentration, together with eddy covariance measurements of CO2 flux. We used CO2 flux data from four boreal coniferous forest sites covering a wide latitudinal range, and CO2 concentration measurements from Sammaltunturi in Pallas. The CO2 gas exchange was taken as the primary determinant for the growing season to which other methods were compared.
Indices based on the cumulative temperature sum and the variation in daily mean temperature were successfully used for approximating the start and cessation of the growing season. The beginning of snow melt was a successful predictor of the onset of the growing season. The chlorophyll fluorescence parameter Fv/Fm and the CO2 concentration were good indicators of both the commencement and cessation of the growing season. By a derivative estimation method for the CO2 concentration, we were also able to capture the larger-scale spring recovery. The trends of the CO2 concentration and temperature indices at Pallas/Sammaltunturi were studied over an 11-yr time period, and a significant tendency towards an earlier spring was observed. This tendency was not observed at the other sites. 相似文献
Indices based on the cumulative temperature sum and the variation in daily mean temperature were successfully used for approximating the start and cessation of the growing season. The beginning of snow melt was a successful predictor of the onset of the growing season. The chlorophyll fluorescence parameter Fv/Fm and the CO
2.
3.
ANDERS LINDROTH FREDRIK LAGERGREN MIKA AURELA BRYNHILDUR BJARNADOTTIR TORBEN CHRISTENSEN EBBA DELLWIK ACHIM GRELLE REAS IBROM TORBJÖRN JOHANSSON HARRY LANKREIJER SAMULI LAUNIAINEN TUOMAS LAURILA MEELIS MÖLDER EERO NIKINMAA KIM PILEGAARD BJARNI D. SIGURDSSON TIMO VESALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(2):129-142
4.
5.
6.
T. AALTO J. HATAKKA I. PAATERO J.-P. TUOVINEN M. AURELA T. LAURILA K. HOLMÉN N. TRIVETT Y. VIISANEN 《Tellus. Series B, Chemical and physical meteorology》2002,54(2):110-126
Diurnal and annual variations of CO2 , O3, SO2 , black carbon and condensation nuclei and their source areas were studied by utilizing air parcel trajectories and tropospheric concentration measurements at a boreal GAW site in Pallas, Finland. The average growth trend of CO2 was about 2.5 ppm yr−1 according to a 4-yr measurement period starting in October 1996. The annual cycle of CO2 showed concentration difference of about 19 ppm between the summer minimum and winter maximum. The diurnal cycle was most pronounced during July and August. The variation between daily minimum and maximum was about 5 ppm. There was a diurnal cycle in aerosol concentrations during spring and summer. Diurnal variation in ozone concentrations was weak. According to trajectory analysis the site was equally affected by continental and marine air masses. During summer the contribution of continental air increased, although the southernmost influences decreased. During daytime in summer the source areas of CO2 were mainly located in the northern parts of the Central Europe, while during winter the sources were more evenly distributed. Ozone showed similar source areas during summer, while during winter, unlike CO2 , high concentrations were observed in air arriving from the sea. Sulfur dioxide sources were more northern (Kola peninsula and further east) and CO2 sources west-weighted in comparison to sources of black carbon. Source areas of black carbon were similar to source areas of aerosols during winter. Aerosol source area distributions showed signs of marine sources during spring and summer. 相似文献
7.
8.
9.
MIIKKA DAL MASO LARISA SOGACHEVA PASI P. AALTO ILONA RIIPINEN MIKA KOMPPULA PETER TUNVED LAURA KORHONEN VILLE SUUR-USKI ANNE HIRSIKKO THEO KURTÉN VELI-MATTI KERMINEN HEIKKI LIHAVAINEN YRJÖ VIISANEN HANS-CHRISTEN HANSSON MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2007,59(3):350-361
10.
MIIKKA DAL MASO ANTTI HYVÄRINEN MIKA KOMPPULA PETER TUNVED VELI-MATTI KERMINEN HEIKKI LIHAVAINEN YRJÖ VIISANEN HANS-CHRISTEN HANSSON MARKKU KULMALA 《Tellus. Series B, Chemical and physical meteorology》2008,60(4):495-508
We investigated size-resolved submicrometre aerosol particle number and volume concentration time series as well as aerosol dynamic parameters derived from Differential Mobility Particle Sizer (DMPS) measurements at five background stations in the Nordic boreal forest area. The stations in question were Aspvreten, Hyytiälä and Utö in southern Finland and Sweden, and Värriö and Pallas in the Finnish Lapland. The objective of our investigation was to identify and quantify annual and interannual variation observable in the time series. We found that the total number and mass concentrations were much lower at the Lapland stations than at the southern stations and that the total particle number was strongly correlated to particle formation event frequency. The annual total number concentration followed the annual distribution of particle formation events at the southern stations but much less clearly at the Lapland stations. The volume concentration was highest during summer, in line with higher condensation growth rates; this is in line with the assumption that a large part of the particle volume is produced by oxidized plant emissions. The decrease of sulphate emissions in Europe was not visible in our data set. Aerosol dynamic parameters such as condensation sink, condensation sink diameter and the power law exponent linking coagulation losses and condensation sink are presented to characterize the submicron Nordic background aerosol. 相似文献