Observations of the tropical atmosphere are fundamental to the understanding of global changes in air quality, atmospheric oxidation capacity and climate, yet the tropics are under-populated with long-term measurements. The first three years (October 2006 -September 2009) of meteorological, trace gas and particulate data from the global WMO/Global Atmospheric Watch (GAW) Cape Verde Atmospheric Observatory Humberto Duarte Fonseca (CVAO; 16° 51' N, 24° 52' W) are presented, along with a characterisation of the origin and pathways of air masses arriving at the station using the NAME dispersion model and simulations of dust deposition using the COSMO-MUSCAT dust model. The observations show a strong influence from Saharan dust in winter with a maximum in super-micron aerosol and particulate iron and aluminium. The dust model results match the magnitude and daily variations of dust events, but in the region of the CVAO underestimate the measured aerosol optical thickness (AOT) because of contributions from other aerosol. The NAME model also captured the dust events, giving confidence in its ability to correctly identify air mass origins and pathways in this region. Dissolution experiments on collected dust samples showed a strong correlation between soluble Fe and Al and measured solubilities were lower at high atmospheric dust concentrations.Fine mode aerosol at the CVAO contains a significant fraction of non-sea salt components including dicarboxylic acids, methanesulfonic acid and aliphatic amines, all believed to be of oceanic origin. A marine influence is also apparent in the year-round presence of iodine and bromine monoxide (IO and BrO), with IO suggested to be confined mainly to the surface few hundred metres but BrO well mixed in the boundary layer. Enhanced CO 2 and CH 4 and depleted oxygen concentrations are markers for air-sea exchange over the nearby northwest African coastal upwelling area. Long-range transport results in generally higher levels of O 3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in European air masses that contain relatively less well-aged air. In air heavily influenced by Saharan dust the O 3 /CO ratio was as low as 0.13, possibly indicating O 3 uptake to dust. Nitrogen oxides (NO x and NO y ) show generally higher concentrations in winter when air mass origins are predominantly from Africa. High photochemical activity at the site is shown by maximum spring/summer concentrations of OH and HO 2 of 9 × 10 6 molecule cm -3 and 6 × 10 8 molecule cm -3 , respectively. After the primary photolysis source, the chemistry of IO and BrO, the abundance of HCHO, and aerosol uptake are important for the HO x budget in this region.3

[1] We present first results from 19 months of semicontinuous concentration measurements of biogeochemical trace gases (CO 2 , CO, and CH 4 ) and O 2 , measured at the Zotino Tall Tower Observatory (ZOTTO) in the boreal forest of central Siberia. We estimated CO 2 and O 2 seasonal cycle amplitudes of 26.6 ppm and 134 per meg, respectively. An observed west-east gradient of about À7 ppm (in July 2006) between Shetland Islands, Scotland, and ZOTTO reflects summertime continental uptake of CO 2 and is consistent with regional modeling studies. We found the oceanic component of the

Methane hydrate is a clathrate, an ice‐like solid formed from methane and water, that is stable under conditions of pressure and temperature found in most of the world's oceans at depths greater than a few hundred meters. Hydrate occurs beneath the seabed where there is sufficient methane to exceed its solubility in water within the hydrate stability field. It has been speculated that methane released from hydrate by climate‐induced changes in pressure and temperature escapes into the ocean and into the atmosphere, where its acts as a greenhouse gas. Further, methane from beneath the seabed is the primary energy source for communities of chemosynthetic biota at the seabed.