Publications

Ozone production and hydrocarbon reactivity in Hong Kong, Southern China

Abstract. Data obtained in Hong Kong during the Hong Kong and the Pearl River Delta (PRD) Pilot Air Monitoring Study in autumn 2002 are analyzed to unravel the relationship between ground-level ozone (O3), pollution precursors, and cross-border transport. Ten ozone episodes, during which the hourly O3 concentration exceeded 100 ppbv in 9 cases and 90 ppbv in one case, are subject to detailed analysis, including one case with hourly O3 of 203 ppbv, which is the highest concentration on record to date in Hong Kong. Combined with high-resolution back trajectories, dCO/dNOy (the ratio of enhancement of CO concentration above background to that of NOy) is used to define whether O3 is locally or regionally produced. Five out of the ten Hong Kong O3-episodes studied show a "pollution signature" that is indicative of impact from Guangdong Province. Examination of speciated volatile organic compounds (VOCs) shows that the reactivity of VOCs is dominated by anthropogenic VOCs, of which the reactive aromatics dominate, in particular xylenes and toluene. Calculations using a photochemical box model indicate that between 50–100% of the O3 increase observed in Hong Kong during the O3 episodes can be explained by photochemical generation within the Hong Kong area, provided that nitrous acid (HONO) is present at the concentrations derived from this study. An Observation-Based Model (OBM) is used to calculate the sensitivity of the O3 production to changes in the concentrations of the precursor compounds. Generally the production of O3 throughout much of the Hong Kong area is limited by VOCs, while high nitric oxide (NO) concentrations suppress O3 concentration.

Photochemistry of an Urban Region using Observations and Numerical Modeling

Ocean Biogeochemistry Control on the Marine Emissions of Brominated Very Short‐Lived Ozone‐Depleting Substances: A Machine‐Learning Approach

Abstract Halogenated very short lived substances (VSLS) affect the ozone budget in the atmosphere. Brominated VSLS are naturally emitted from the ocean, and current oceanic emission inventories vary dramatically. We present a new global oceanic emission inventory of Br‐VSLS (bromoform and dibromomethane), considering the physical forcing in the ocean and the atmosphere, as well as the ocean biogeochemistry control. A data‐oriented machine‐learning emulator was developed to couple the air‐sea exchange with the ocean biogeochemistry. The predicted surface seawater concentrations and the surface atmospheric mixing ratios of Br‐VSLS are evaluated with long‐term, global‐scale observations; and the predicted vertical distributions of Br‐VSLS are compared to the global airborne observations in both boreal summer and winter. The global marine emissions of bromoform and dibromomethane are estimated to be 385 and 54 Gg Br per year, respectively. The new oceanic emission inventory of Br‐VSLS is more skillful than the widely used top‐down approaches for representing the seasonal/spatial variations and the annual means of atmospheric concentrations. The new approach improves the model predictability for the coupled Earth system model and can be used as a basis for investigating the past and future ocean emissions and feedbacks under climate change. This model framework can be used to calculate the bidirectional oceanic fluxes for other compounds of interest.

Parameterizations of US wildfire and prescribed fire emission ratios and emission factors based on FIREX-AQ aircraft measurements

Abstract. Extensive airborne measurements of non-methane organic gases (NMOGs), methane, nitrogen oxides, reduced nitrogen species, and aerosol emissions from US wild and prescribed fires were conducted during the 2019 NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality campaign (FIREX-AQ). Here, we report the atmospheric enhancement ratios (ERs) and inferred emission factors (EFs) for compounds measured on board the NASA DC-8 research aircraft for nine wildfires and one prescribed fire, which encompass a range of vegetation types. We use photochemical proxies to identify young smoke and reduce the effects of chemical degradation on our emissions calculations. ERs and EFs calculated from FIREX-AQ observations agree within a factor of 2, with values reported from previous laboratory and field studies for more than 80 % of the carbon- and nitrogen-containing species. Wildfire emissions are parameterized based on correlations of the sum of NMOGs with reactive nitrogen oxides (NOy) to modified combustion efficiency (MCE) as well as other chemical signatures indicative of flaming/smoldering combustion, including carbon monoxide (CO), nitrogen dioxide (NO2), and black carbon aerosol. The sum of primary NMOG EFs correlates to MCE with an R2 of 0.68 and a slope of −296 ± 51 g kg−1, consistent with previous studies. The sum of the NMOG mixing ratios correlates well with CO with an R2 of 0.98 and a slope of 137 ± 4 ppbv of NMOGs per parts per million by volume (ppmv) of CO, demonstrating that primary NMOG emissions can be estimated from CO. Individual nitrogen-containing species correlate better with NO2, NOy, and black carbon than with CO. More than half of the NOy in fresh plumes is NO2 with an R2 of 0.95 and a ratio of NO2 to NOy of 0.55 ± 0.05 ppbv ppbv−1, highlighting that fast photochemistry had already occurred in the sampled fire plumes. The ratio of NOy to the sum of NMOGs follows trends observed in laboratory experiments and increases exponentially with MCE, due to increased emission of key nitrogen species and reduced emission of NMOGs at higher MCE during flaming combustion. These parameterizations will provide more accurate boundary conditions for modeling and satellite studies of fire plume chemistry and evolution to predict the downwind formation of secondary pollutants, including ozone and secondary organic aerosol.

Ozone production in the upper troposphere and the influence of aircraft during SONEX: approach of NO_x‐saturated conditions

During October/November 1997, simultaneous observations of NO, HO 2 and other species were obtained as part of the SONEX campaign in the upper troposphere. We use these observations, over the North Atlantic (40–60°N), to derive ozone production rates, P(O 3 ), and to examine the relationship between P(O 3 ) and the concentrations of NO x (= NO + NO 2 ) and HO x (= OH + peroxy) radicals. A positive correlation is found between P(O 3 ) and NO x over the entire data set, which reflects the association of elevated HO x with elevated NO x injected by deep convection and lightning. By filtering out this association we find that for NO x >70 pptv, P(O 3 ) is nearly independent of NO x , showing the approach of NO x ‐saturated conditions. Predicted doubling of aircraft emissions in the future will result in less than doubling of the aircraft contribution to ozone over the North Atlantic in the fall. Greater sensitivity to aircraft emissions would be expected in the summer.

Modeling and analysis of atmospheric chemistry over the South Pole during ANTCI

The Tropical Forest and Fire Emissions Experiment: overview and airborne fire emission factor measurements

The Tropical Forest and Fire Emissions Experiment (TROFFEE) used laboratory measurements followed by airborne and ground based field campaigns during the 2004 Amazon dry season to quantify the emissions from pristine tropical forest and several plantations as well as the emissions, fuel consumption, and fire ecology of tropical deforestation fires. The airborne campaign used an Embraer 110B aircraft outfitted with whole air sampling in canisters, mass-calibrated nephelometry, ozone by UV absorbance, Fourier transform infrared spectroscopy (FTIR), and proton-transfer mass spectrometry (PTR-MS) to measure PM10, O3, CO2, CO, NO, NO2, HONO, HCN, NH3, OCS, DMS, CH4, and up to 48 non-methane organic compounds (NMOC). The Brazilian smoke/haze layers extended to 2–3 km altitude, which is much lower than the 5–6 km observed at the same latitude, time of year, and local time in Africa in 2000. Emission factors (EF) were computed for the 19 tropical deforestation fires sampled and they largely compare well to previous work. However, the TROFFEE EF are mostly based on a much larger number of samples than previously available and they also include results for significant emissions not previously reported such as: nitrous acid, acrylonitrile, pyrrole, methylvinylketone, methacrolein, crotonaldehyde, methylethylketone, methylpropanal, “acetol plus methylacetate,” furaldehydes, dimethylsulfide, and C1- C4 alkyl nitrates. Thus, we recommend these EF for all tropical deforestation fires. The NMOC emissions were _80% reactive, oxygenated volatile organic compounds (OVOC). Our EF for PM10 (17.8±4 g/kg) is _25% higher than previously reported for tropical forest fires and may reflect a trend towards, and sampling of, larger fires than in earlier studies. A large fraction of the total burning for 2004 likely occurred during a two-week period of very low humidity. The combined output of these fires created a massive “mega-plume” >500 km across that we sampled on 8 September. The megaplume contained high PM10 and 10–50 ppbv of many reactive species such as O3, NH3, NO2, CH3OH, and organic acids. This is an intense and globally important chemical processing environment that is still poorly understood. The mega-plume or “white ocean” of smoke covered a large area in Brazil, Bolivia, and Paraguay for about one month. The smoke was transported >2000 km to the southeast while remaining concentrated enough to cause a 3–4-fold increase in aerosol loading in the Sao Paulo area for several days.

Hydrogen peroxide and methylhydroperoxide distributions related to ozone and odd hydrogen over the North Pacific in the fall of 1991

Hydrogen peroxide and methylhydroperoxide were measured in the troposphere over the western North Pacific as part of the airborne portion of NASA's Global Tropospheric Experiment/Pacific Exploratory Mission‐West A field mission. The flights circled the North Pacific, focusing on the western Pacific, and extended from 300 to 13,000 m altitude. The hydroperoxides were uniquely separated and quantified using a high‐pressure liquid chromatography system in conjunction with a continuous enzyme fluorometric instrument. Results show a latitudinal gradient in both peroxides at all altitudes; for example, between 3 and 5 km, H 2 O 2 median values decrease from 1700 to 500 parts per trillion by volume (pptv) in going from 0°–15°N to 45°–60°N, and the corresponding decrease in CH 3 OOH was 1100 to 200 pptv. Concentration maxima are observed in both species at altitudes of 2 to 3 km with H 2 O 2 concentrations below 1 km lower by 30%, 10% for CH 3 OOH, and even lower, by a factor of 10, for both above 9 km. The H 2 O 2 to CH 3 OOH ratio increased with altitude and latitude with ratios <1 in the tropical surface layer and >2 at midlatitude high altitude. Highest peroxide concentrations were encountered over the Celebes Sea in air which was impacted by aged biomass fire and urban pollutants. CH 3 OOH was below the level of detection in stratospheric air. H 2 O 2 exceeded SO 2 95% of the time, with the exceptions generally above 9 km. Above 3 km, O 3 increases with decreasing H 2 O 2 and CH 3 OOH. Below 3 km the O 3 ‐CH 3 OOH trend is the same but O 3 increases with increasing H 2 O 2 . The measurements are compared with predictions based upon a photochemical steady state zero‐dimensional model and a three‐dimensional mesoscale time‐dependent model. These models capture observed trends in H 2 O 2 and CH 3 OOH, with the possible exception of H 2 O 2 below 2 km where surface removal is important. A surface removal lifetime of 3.5 days brings the observed and zero‐dimensional model‐estimated H 2 O 2 into agreement. The steady state model suggests a strong correlation between the ratios of NO/CO or HO 2 /HO and the ratio of H 2 O 2 /CH 3 OOH. The observed hydroperoxide ratios bracket the modeled relationship with occasionally much lower H 2 O 2 than expected.

Characterization of the chemical signatures of air masses observed during the PEM experiments over the western Pacific

Extensive observations of tropospheric trace species during the second NASA Global Tropospheric Experiment Western Pacific Exploratory Mission (PEM‐West B) in February‐March 1994 showed significant seasonal variability in comparison with the first mission (PEM‐West A), conducted in September‐October 1991. In this study we adopt a previously established analytical method, i.e., the ratio C 2 H 2 /CO as a measure of the relative degree of atmospheric processing, to elucidate the key similarities and variations between the two missions. In addition, the C 2 H 2 /CO ratio scheme is combined with the back‐trajectory‐based and the LIDAR‐based air mass classification schemes, respectively, to make in‐depth analysis of the seasonal variation between PEM‐West A and PEM‐West B (hereinafter referred to as PEM‐WA and PEM‐WB). A large number of compounds, including long‐lived NMHCs, CH 4 , and CO 2 , are, as expected, well correlated with the ratio C 2 H 2 /CO. In comparison with PEM‐WA, a significantly larger range of observed C 2 H 2 /CO values at the high end for the PEM‐WB period indicates that the western Pacific was more impacted by “fresher” source emissions, i.e., faster or more efficient continental outflow. As in the case of PEM‐WA, the C 2 H 2 /CO scheme complements the back‐trajectory air mass classification scheme very well. By combining the two schemes, we found that the atmospheric processing in the region is dominated by atmospheric mixing for the trace species analyzed. This PEM‐WB wintertime result is similar to that found in PEM‐WA for the autumn. In both cases, photochemical reactions are found to play a significant role in determining the background mixing ratios of trace gases, and in this way the two processes are directly related and dependent upon each other. This analysis also indicates that many of the upper tropospheric air masses encountered over the western Pacific during PEM‐WB may have had little impact from eastern Asia's continental surface sources. NO x mixing ratios were significantly enhanced during PEM‐WB when compared with PEM‐WA, in the upper troposphere's more atmospherically processed air masses. These high levels of NO x resulted in a substantial amount of photochemical production of O 3 . A lack of corresponding enhancements in surface emission tracers strongly implies that in situ atmospheric sources such as lightning are responsible for the enhanced upper tropospheric NO x . The similarity in NO x values between the northern (higher air traffic) and southern continental air masses together with the indications of a large seasonal shift suggests that aircraft emissions are not the dominant source. However, photochemical recycling cannot be ruled out as this in situ source of NO x .

The impact of local sources and long‐range transport on aerosol properties over the northeast U.S. region during INTEX‐NA

We use data collected aboard the NASA DC‐8 aircraft during the summer 2004, Intercontinental Transport and Chemical Evolution Experiment over North America (INTEX‐NA) field campaign to examine the origin, composition, physical and optical properties of aerosols within air masses sampled over and downwind of the northeastern U.S. We note that aerosol concentrations within the region exhibited steep vertical gradients and significant variability in both time and space. An examination of air mass chemical signatures and backward trajectories indicates that transport from four, significantly different source regions contributed to the variability: the subtropical Atlantic Ocean (AO); the U.S. west coast and eastern Pacific (WCP); the U.S. east coast and Midwestern states (EC); and northwest Canada and Alaska (CA). AO air masses were typically confined to below 2 km altitude, exhibited low pollutant contents, contained enhanced levels of sea salt, and were typically observed when the Bermuda High strengthened. The most common air mass present in the upper troposphere, WCP air often contained weak dust and aged pollution enhances from convective input occurring over the central part of the continent. CA air exhibited enhancements in anthropogenic pollution tracers below 2 km and contained some black‐carbon rich haze layers between 3 and 5 km that could be traced to forest fires burning in western Canada and Alaska. EC air was prevalent at lower elevations throughout the study area and exhibited enhanced scattering along with elevated levels of sulfate aerosols and combustion tracers. There is an overall balance between the observed cations and anions for all cases, except EC air mass below 4 km.

Lecture 1. Intermolecular Forces Liquids & Solids, Part I

UCI Chem 1B is the second quarter of General Chemistry and covers the following topics: properties of gases, liquids, solids; changes of state; properties of solutions; stoichiometry; thermochemistry; and thermodynamics. Index of Topics: 0:48:33 First to Measure Gases: Gay Lussac 0:50:24 Genealogy (Academic Heritage) 0:51:38 Stratospheric Chemistry 0:57:54 CFC 1:01:00 Cicerone and Stolarski (Catalytic Cycle) 1:05:26 What are the effects fo reduced stratospheric ozone? 1:06:45 DNA Mutation 1:07:49 Ozone Graph 1:09:40 Weather balloon Photos 1:10:14 Ozone Over McMurdo Station, Antartica 1:12:25 Polar Stratospheric Clouds 1:13:45 Concentration vs Time Graph 1:14:01 South Pole Photos

Supplementary material to "Using observed urban NO _x sinks to constrain VOC reactivity and the ozone and radical budget in the Seoul Metropolitan Area"

The production and persistence of ΣRONO ₂ in the Mexico City plume

Abstract. Alkyl and multifunctional nitrates (RONO2, ΣANs) have been observed to be a significant fraction of NOy in a number of different chemical regimes. Their formation is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. ΣANs also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Numerous studies have investigated the role of nitrate formation from biogenic compounds and in the remote atmosphere. Less attention has been paid to the role ΣANs may play in the complex mixtures of hydrocarbons typical of urban settings. Measurements of total alkyl and multifunctional nitrates, NO2, total peroxy nitrates (ΣPNs), HNO3 and a representative suite of hydrocarbons were obtained from the NASA DC-8 aircraft during spring of 2006 in and around Mexico City and the Gulf of Mexico. ΣANs were observed to be 10–20% of NOy in the Mexico City plume and to increase in importance with increased photochemical age. We describe three conclusions: (1) Correlations of ΣANs with odd-oxygen (Ox) indicate a stronger role for ΣANs in the photochemistry of Mexico City than is expected based on currently accepted photochemical mechanisms, (2) ΣAN formation suppresses peak ozone production rates by as much as 40% in the near-field of Mexico City and (3) ΣANs play a significant role in the export of NOy from Mexico City to the Gulf Region.

Secondary Organic Aerosol Formation from in-Use Motor Vehicle Emissions Using a Potential Aerosol Mass Reactor

Secondary organic aerosol (SOA) formation from in-use vehicle emissions was investigated using a potential aerosol mass (PAM) flow reactor deployed in a highway tunnel in Pittsburgh, Pennsylvania. Experiments consisted of passing exhaust-dominated tunnel air through a PAM reactor over integrated hydroxyl radical (OH) exposures ranging from ∼ 0.3 to 9.3 days of equivalent atmospheric oxidation. Experiments were performed during heavy traffic periods when the fleet was at least 80% light-duty gasoline vehicles on a fuel-consumption basis. The peak SOA production occurred after 2-3 days of equivalent atmospheric oxidation. Additional OH exposure decreased the SOA production presumably due to a shift from functionalization to fragmentation dominated reaction mechanisms. Photo-oxidation also produced substantial ammonium nitrate, often exceeding the mass of SOA. Analysis with an SOA model highlight that unspeciated organics (i.e., unresolved complex mixture) are a very important class of precursors and that multigenerational processing of both gases and particles is important at longer time scales. The chemical evolution of the organic aerosol inside the PAM reactor appears to be similar to that observed in the atmosphere. The mass spectrum of the unoxidized primary organic aerosol closely resembles ambient hydrocarbon-like organic aerosol (HOA). After aging the exhaust equivalent to a few hours of atmospheric oxidation, the organic aerosol most closely resembles semivolatile oxygenated organic aerosol (SV-OOA) and then low-volatility organic aerosol (LV-OOA) at higher OH exposures. Scaling the data suggests that mobile sources contribute ∼ 2.9 ± 1.6 Tg SOA yr(-1) in the United States, which is a factor of 6 greater than all mobile source particulate matter emissions reported by the National Emissions Inventory. This highlights the important contribution of SOA formation from vehicle exhaust to ambient particulate matter concentrations in urban areas.

Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements – corrected

Abstract. The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O3 and CH4 (O3, CH4, CO, H2O, HCHO, H2O2, CH3OOH, C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3, HNO4, peroxyacetyl nitrate, and other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O3 and CH4 photochemical tendencies from this modeling data stream for ATom 1. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom 10 s data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find generally good agreement with the reactivity rates for O3 and CH4. Models distinctly underestimate O3 production below 2 km relative to the mid-troposphere, and this can be traced to lower NOx levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation. This paper presents a corrected version of the paper published under the same authors and title (sans “corrected”) as https://doi.org/10.5194/acp-21-13729-2021.

Aircraft Measurements of Dimethyl Sulfide (DMS) Using a Whole Air Sampling Technique

Limitations in representation of physical processes prevent successful simulation of PM _2.5 during KORUS-AQ

Abstract. High levels of fine particulate matter (PM2.5) pollution in East Asia often exceed local air quality standards. Observations from the Korea–United States Air Quality (KORUS-AQ) field campaign in May and June 2016 showed that development of extreme pollution (haze) occurred through a combination of long-range transport and favorable meteorological conditions that enhanced local production of PM2.5. Atmospheric models often have difficulty simulating PM2.5 chemical composition during haze, which is of concern for the development of successful control measures. We use observations from KORUS-AQ to examine the ability of the GEOS-Chem chemical transport model to simulate PM2.5 composition throughout the campaign and identify the mechanisms driving the pollution event. At the surface, the model underestimates sulfate by −64 % but overestimates nitrate by +36 %. The largest underestimate in sulfate occurs during the pollution event, for which models typically struggle to generate elevated sulfate concentrations due to missing heterogeneous chemistry in aerosol liquid water in the polluted boundary layer. Hourly surface observations show that the model nitrate bias is driven by an overestimation of the nighttime peak. In the model, nitrate formation is limited by the supply of nitric acid, which is biased by +100 % against aircraft observations. We hypothesize that this is due to a large missing sink, which we implement here as a factor of 5 increase in dry deposition. We show that the resulting increased deposition velocity is consistent with observations of total nitrate as a function of photochemical age. The model does not account for factors such as the urban heat island effect or the heterogeneity of the built-up urban landscape, resulting in insufficient model turbulence and surface area over the study area that likely results in insufficient dry deposition. Other species such as NH3 could be similarly affected but were not measured during the campaign. Nighttime production of nitrate is driven by NO2 hydrolysis in the model, while observations show that unexpectedly elevated nighttime ozone (not present in the model) should result in N2O5 hydrolysis as the primary pathway. The model is unable to represent nighttime ozone due to an overly rapid collapse of the afternoon mixed layer and excessive titration by NO. We attribute this to missing nighttime heating driving deeper nocturnal mixing that would be expected to occur in a city like Seoul. This urban heating is not considered in air quality models run at large enough scales to treat both local chemistry and long-range transport. Key model failures in simulating nitrate, mainly overestimated daytime nitric acid, incorrect representation of nighttime chemistry, and an overly shallow and insufficiently turbulent nighttime mixed layer, exacerbate the model's inability to simulate the buildup of PM2.5 during haze pollution. To address the underestimate in sulfate most evident during the haze event, heterogeneous aerosol uptake of SO2 is added to the model, which previously only considered aqueous production of sulfate from SO2 in cloud water. Implementing a simple parameterization of this chemistry improves the model abundance of sulfate but degrades the SO2 simulation, implying that emissions are underestimated. We find that improving model simulations of sulfate has direct relevance to determining local vs. transboundary contributions to PM2.5. During the haze pollution event, the inclusion of heterogeneous aerosol uptake of SO2 decreases the fraction of PM2.5 attributable to long-range transport from 66 % to 54 %. Locally produced sulfate increased from 1 % to 25 % of locally produced PM2.5, implying that local emissions controls could have a larger effect than previously thought. However, this additional uptake of SO2 is coupled to the model nitrate prediction, which affects the aerosol liquid water abundance and chemistry driving sulfate–nitrate–ammonium partitioning. An additional simulation of the haze pollution with heterogeneous uptake of SO2 to aerosol and simple improvements to the model nitrate simulation results in 30 % less sulfate due to 40 % less nitrate and aerosol water, and this results in an underestimate of sulfate during the haze event. Future studies need to better consider the impact of model physical processes such as dry deposition and nighttime boundary layer mixing on the simulation of nitrate and the effect of improved nitrate simulations on the overall simulation of secondary inorganic aerosol (sulfate + nitrate + ammonium) in East Asia. Foreign emissions are rapidly changing, increasing the need to understand the impact of local emissions on PM2.5 in South Korea to ensure continued air quality improvements.

Emissions from miombo woodland and dambo grassland savanna fires

Airborne measurements of trace gases and particles over and downwind of two prescribed savanna fires in Zambia are described. The measurements include profiles through the smoke plumes of condensation nucleus concentrations and normalized excess mixing ratios of particles and gases, emission factors for 42 trace gases and seven particulate species, and vertical profiles of ambient conditions. The fires were ignited in plots of miombo woodland savanna, the most prevalent savanna type in southern Africa, and dambo grassland savanna, an important enclave of miombo woodland ecosystems. Emission factors for the two fires are combined with measurements of fuel loading, combustion factors, and burned area (derived from satellite burn scar retrievals) to estimate the emissions of trace gases and particles from woodland and grassland savanna fires in Zambia and southern Africa during the dry season (May–October) of 2000. It is estimated that the emissions of CO 2 , CO, total hydrocarbons, nitrogen oxides (NO x as NO), sulfur dioxide (SO 2 ), formaldehyde, methyl bromide, total particulate matter, and black carbon from woodland and grassland savanna fires during the dry season of 2000 in southern Africa contributed 12.3%, 12.6%, 5.9%, 10.3%, 7.5%, 24.2%, 2.8%, 17.5%, and 11.1%, respectively, of the average annual emissions from all types of savanna fires worldwide. In 2000 the average annual emissions of methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, and acetic acid from the use of biofuels in Zambia were comparable to or exceeded dry season emissions of these species from woodland and grassland savanna fires in Zambia.