[1] During the Large-Scale Biosphere-Atmosphere Experiment in Amazonia wet season experiment, the near-surface measurements of equivalent potential temperature and ozone at night, when background levels of ozone are low, clearly show that convective downdrafts rapidly transport air with higher ozone and lower equivalent potential temperature down to the surface from around 800 hPa. This largely unreported downward transport of ozone may play a significant role in the photochemistry of the atmosphere boundary layer and increase the surface deposition of ozone.

[1] Measurements of NO-NO 2 -O 3 trace gas exchange were performed for two transition season periods during the La Niña year 1999 (30 April to 17 May, ''wet-dry,'' and 24 September to 27 October, ''dry-wet'') over a cattle pasture in Rondônia. A dynamic chamber system (applied during the dry-wet season) was used to directly measure emission fluxes of nitric oxide (NO) and surface resistances for nitrogen dioxide (NO 2 ) and ozone (O 3 ) deposition. A companion study was simultaneously performed in an oldgrowth forest. In order to determine ecosystem-representative NO 2 and O 3 deposition fluxes for both measurement periods, an inferential method (multiresistance model) was applied to measure ambient NO 2 and O 3 concentrations using observed quantities of turbulent transport. Supplementary measurements included soil NO diffusivity and soil nutrient analysis. The observed NO soil emission fluxes were nine times lower than oldgrowth rain forest emissions under similar soil moisture and temperature conditions and were attributed to the combination of a reduced soil N cycle and lower effective soil NO diffusion at the pasture. Canopy resistances (R c ) of both gases controlled the deposition processes during the day for both measurement periods. Day and night NO 2 canopy resistances were significantly similar (a = 0.05) during the dry-wet period. Ozone canopy resistances revealed significantly higher daytime resistances of 106 s m À1 versus 65 s m À1at night because of plant, soil, and wet skin uptake processes, enhanced by stomatal activity at night and aqueous phase chemistry on vegetative and soil surfaces. The surface of the pasture was a net NO x sink during 1999, removing seven times more NO 2 from the atmosphere than was emitted as NO.

Abstract. As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia -Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO 2 ), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ER CN/CO ) fell in the range 14-32 cm −3 ppb −1 in most of the investigated smoke plumes. Particle number emission ratios have to our knowledge not been previously measured in tropical deforestation fires, but our results are in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependent on the fire conditions (combustion efficiency). Variability in ER CN/CO between fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO 2 emission ratios (ER CO/CO 2 ), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, reflecting the fact that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft, which increased the EF by a factor of 1.5-2.1. Vertical transport of smoke from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found Correspondence to: M. O. Andreae (andreae@mpch-mainz.mpg.de) to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger than in the unprocessed smoke, mostly due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets. This process may have significant atmospheric implications on a regional and larger scale.

Urban pollution can often impact surrounding, non-urban regions, through advection and dispersal of pollutants by the prevailing winds. Urban regions located upstream of high mountains, such as the Andes, can potentially impact the cryosphere by deposition of particles onto the surface of the snowpack and glaciers.Santiago, the capital of Chile, has more than 6 million inhabitants and regularly experiences episodes of severe pollution, particularly during the austral winter. Some studies have hypothesized that particle pollution from Santiago can reach the cryosphere downwind of the city, but the scarcity of measurements made high in the mountains prevents the validation of mesoscale models so the proof of actual impact remains elusive. A research project was designed to provide some insight into this question. The Pollution Impact on Snow in the Cordillera -Experiments and Simulations (PISCES) project was carried out in 2014 and includes both observational and modeling components. A five-week field campaign was conducted at the end of winter, at an elevated site in a mountain valley, 65 km to the southeast of the center of Santiago, to characterize some aspects of particulate pollution.During synoptic conditions that result in clear days at the site, the mesoscale mountain-valley circulation is effective in transporting pollutants upwards during the day, leading to diluted particle concentrations beyond the summits of the highest peaks. Cloudy days with reduced up-valley circulation do not show increased concentrations associated with transport. Back trajectories indicate that air masses reaching the site during the field campaign are seldom influenced by pollution from Santiago.

Abstract. In the winter-rain southern Atacama Desert of the Coquimbo Region of Chile, El Niño -Southern Oscillation (ENSO) events modulate primary productivity. In this region, there are important changes in water availability between La Niña (dry) and El Niño (rainy) years. Using interannual comparisons of LANDSAT images from 30 • to 31 • S latitude, we observed changes in primary productivity between dry and rainy years at the regional level. There were also significant, negative correlations between productivity and elevation, with changes occurring first at low elevation during rainy years. The limiting factors to dryland vegetation primary productivity is different in regard to elevation. Rain during an El Niño year is the main factor that explains the increase in primary productivity at low elevation, while lower temperatures reduce and delay the net primary productivity at mid elevation.