also cannot be neglected. Daytime mean CH 4 concentrations from the Siberian tower sites were generally higher than CH 4 values reported at NOAA coastal sites in the same latitudinal zone, and the difference in concentrations between two sets of sites was reproduced with a coupled Eulerian-Lagrangian transport model. Simulations of emissions from different CH 4 sources suggested that the major contributor to variation switched from wetlands during summer to fossil fuel during winter.

[1] In situ measurements of the vertical distribution of carbon dioxide (CO 2 ) carried out with a light aircraft over a tower site (Berezorechka; 56°08′45″N, 84°19′49″E) in the taiga region of West Siberia from October 2001 to March 2012 document the detailed seasonal and vertical variation of CO 2 concentrations during daytime. The variation appears to be controlled mainly by the CO 2 flux from taiga ecosystems and the height of the planetary boundary layer (PBL). We calculated average CO 2 concentrations in the PBL and the lower free troposphere (LFT), both of which show clear seasonal cycles and an increasing long-term trend. Seasonal amplitude in the PBL had a larger value (29 ppm) than that in the LFT (14 ppm), demonstrating strong CO 2 source-sink forcing by the taiga ecosystems. Mean CO 2 concentrations during 13:00-17:00 local standard time observed at the four levels of the tower (5, 20, 40, and 80 m) showed lower CO 2 concentrations than that observed in the PBL by aircraft during June-August (growing season). This negative bias decreased with increasing inlet height such that the minimum difference appeared at the 80-m inlet (À2.4 ± 0.8 ppm). No such bias was observed during other months (dormant season). The daytime CO 2 flux, based on multiple vertical profiles obtained on a single day, ranged from À36.4 to 3.8 μmol m À2 s À1 during July-September. There was a clear difference in the fluxes between the morning and afternoon, suggesting that these data should be considered examples of fluxes during several daytime hours from the West Siberian taiga.

No abstract

We have been conducting continuous measurements of CH₄ and CO₂ on a network of towers (JR-STATION: Japan–Russia Siberian Tall Tower Inland Observation Network) located in taiga, steppe, and wetland biomes of Siberia. Here we describe measurements from two forested bog sites, Karasevoe (KRS; 58°15′ N, 82°25′ E) and Demyanskoe (DEM; 59°47′ N, 70°52′ E), in West Siberia from 2005 to 2009. Although both CH₄ and CO₂ accumulation (ΔCH₄ and ΔCO₂) during nighttime (duration of 7 h beginning 21:30 LST) at KRS in July 2007 showed an anomalously high concentration, the higher ratios of ΔCH₄/ΔCO₂ compared with those in other years indicate that a considerably more CH₄ flux occurred relative to the CO₂ flux in response to large precipitation recorded in 2007 (~2.7 mm d⁻¹ higher than the climatological 1979–1998 base). Estimated seasonal CH₄ fluxes based on the ratio of ΔCH₄/ΔCO₂ and the CASA 3-hourly CO₂ flux for the 2005–2009 period exhibited a seasonal variation with a maximum in July at both sites. Annual values of the CH₄ emission from the forested bogs around KRS (approx. 7.8×10⁴ km²) calculated from a process-based ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT), showed inter-annual variation of 0.54, 0.31, 0.94, 0.44, and 0.41 Tg CH₄ yr⁻¹ from 2005 to 2009, respectively, with the highest values in 2007. It was assumed in the model that the area flooded with water is proportional to the cumulative anomaly in monthly precipitation rate