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During the NOAA Southern Oxidant Study 1999 (SOS1999), Texas Air Quality Study 2000 (TexAQS2000), International Consortium for Atmospheric Research on Transport and Transformation (ICARTT2004), and Texas Air Quality Study 2006 (TexAQS2006) campaigns, airborne measurements of isoprene and monoterpenes were made in the eastern United States and in Texas, and the results are used to evaluate the biogenic emission inventories BEIS3.12, BEIS3.13, MEGAN2, and WM2001. Two methods are used for the evaluation. First, the emissions are directly estimated from the ambient isoprene and monoterpene measurements assuming a well-mixed boundary layer and are compared with the emissions from the inventories extracted along the flight tracks. Second, BEIS3.12 is incorporated into the detailed transport model FLEXPART, which allows the isoprene and monoterpene mixing ratios to be calculated and compared to the measurements. The overall agreement for all inventories is within a factor of 2 and the two methods give consistent results. MEGAN2 is in most cases higher, and BEIS3.12 and BEIS3.13 lower than the emissions determined from the measurements. Regions with clear discrepancies are identified. For example, an isoprene hot spot to the northwest of Houston, Texas, was expected from BEIS3 but not observed in the measurements. Interannual differences in emissions of about a factor of 2 were observed in Texas between 2000 and 2006. Copyright 2010 by the American Geophysical Union.

A diurnally averaged ozone decay rate of about 0.11 [day.sup.-1] was observed under partly cloudy sky in the boundary layer over the eastern Atlantic during the second Lagrangian experiment in the Atlantic Stratocumulus Transition Experiment. The observed decay rate can be accounted for by the combined effects of ozone loss through photolysis by UV radiation, reaction with HO, radical, and deposition on the sea surface, and effects of ozone production through photooxidation of carbon monoxide and methane in the presence of nitrogen oxides. The main contributor to the ozone decay is photolysis by UV radiation, but the other sources and sinks also make significant contributions.

The mean time rates of change of temperature, total water mixing ratio and ozone along airflow trajectories in the lower troposphere over the eastern Pacific are inferred by comparing aircraft soundings from the First ISCCP Regional Experiment (FIRE) and the Hawaiian Rainband Project (HaRP). Through the use of the estimated mean fluxes of temperature and total water mixing ratio, it is found that the tendency for stratus layers to grow or dissipate is very sensitive to the assumed turbulence structure below the capping inversion. A mixed-layer model that assumes a well-mixed boundary layer up to the capping inversion predicts a solid cloud layer extending all the way to Hawaii, whereas a model that allows decoupling predicts rapid dissipation of the stratus layer. It is concluded that stratus dissipation here is due to the slowdown of turbulent mixing throughout the layer below the capping inversion, not the drying out of a well-mixed layer; hence, the mixed-layer model cannot be expected to predict realistic cloud dissipation. The differences in ozone concentration observed in the boundary layer during HaRP and FIRE suggest a chemical loss of ozone of 3-8 ppb day to the -1, corresponding to a lifetime of 3-9 days. This implies that ozone cannot be treated as a conserved tracer when dealing with ozone budgets over periods of days. The ozone sink is probably of photochemical origin, and it requires further investigation.