A field study was conducted to determine the effects of ambient conditions and burning practices of rice fields in Taiwan on the chemical and physical characteristics of the smoke aerosol. Rice straw was burned on an actual rice field under typical conditions and smoke particles were collected immediately downwind of the field over the full particle size spectrum. Here we present size distributions of levoglucosan, a common molecular tracer for biomass burning, as well as detailed concentration patterns of three anhydrosugars, including mannosan, and galactosan, in addition to smoke aerosol concentrations of inorganic ions and carbonaceous species. The generated smoke aerosol was characterized by a high OC/EC ratio (10) and a large fraction of potassium (K + ) and chloride (Cl -) ions at a Cl -/K + ratio of 2. Levoglucosan showed a distinct bimodal distribution in the smoke particles with a large fraction (up to 56%) of the total levoglucosan mass observed in very large particles (PM >10 ). The prevailing ambient conditions (such as relatively high humidity), atmospheric processes (e.g., particle coagulation, hygroscopic growth, and deposition), the specific burning practices of rice fields in Taiwan (slow burning of straw spread in thin layers on the ground), as well as the inherent properties of rice straw likely influenced the particle size characteristics of the smoke tracer. Moreover, the relative abundance of the three biomass burning tracers showed a unique pattern (in good agreement with previous chamber burn measurements): levoglucosanto-mannosan ratios were distinctly higher (with an average value of 27) than those observed for other types of biomass, such as softwood, hard wood, peat, or leaves, in previous studies. Such chemical fingerprint may be used in source apportionment studies for the assessment of contributions from the combustion of specific types of biomass.

[1] For CareBeijing-2006, two sites were established in urban and suburban regions of Beijing in summer 2006. Observations of O 3 and its precursors together with meteorological parameters at both sites are presented. Gross ozone production rate P(O 3 ) and sensitivity to nitric oxides (NO x ) and volatile organic compounds (VOCs) were investigated using an observation-based photochemical box model (OBM). P(O 3 ) varied from nearly zero to 120 and 50 ppb h −1 for urban and suburban sites, respectively. These rates were greater than the accumulation rates of the observed oxidant (O 3 + NO 2 ) concentrations. The O 3 episodes typically appeared under southerly wind conditions with high P(O 3 ), especially at the urban site. Sensitivity studies with and without measured nitrous acid (HONO) as a model constraint suggested that the estimated P(O 3 ) at both sites was strongly enhanced by radical production from HONO photolysis. Both NO x -and VOC-sensitive chemistries existed over time scales from hours to days at the two sites. The variation in O 3 -sensitive chemistry was relatively well explained by the ratio of the average daytime total VOC reactivity (k TVOC ) to NO, with the transition chemistry corresponding to a k TVOC /NO value of 2-4 s. Pronounced diurnal variations in the O 3 production regime were found. In the morning, conditions were always strongly VOC-limited, while in the afternoon, conditions were variable for different days and different sites. The model-calculated results were tested by measurements of H 2 O 2 , HNO 3 , total OH reactivity, and HO x radicals. The OBM was generally capable of correctly simulating the levels of P(O 3 ), although it might tend to overpredict the VOC-sensitive chemistry.

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[1] The vertical and spatial structure of the atmospheric El Niño-Southern Oscillation (ENSO) signal is investigated using radio occultation (RO) data from August 2006 to December 2010. Due to their high vertical resolution and global coverage, RO data are well suited to describe the full 3-dimensional ENSO structure in the troposphere and lower stratosphere. We find that interannual temperature anomalies in the equatorial region show a natural decomposition into zonal-mean and eddy (deviations from the zonal-mean) components that are both related to ENSO. Consistent with previous studies, we find that during the warm phase of ENSO, zonal-mean temperatures increase in the tropical troposphere and decrease in the tropical stratosphere. Maximum warming occurs above 8 km, and the transition between warming and cooling occurs near the tropopause. This zonal-mean response lags sea surface temperature anomalies in the eastern equatorial Pacific by 3 months. The atmospheric eddy component, in contrast, responds rapidly (within 1 month) to ENSO forcing. This signal features a low-latitude dipole between the Indian and Pacific Oceans, with off-equatorial maxima centered around 20 to 30 latitude in both hemispheres. The eddy response pattern attains maximum amplitude in the upper troposphere near 11 km and (with opposite polarity) in a shallow layer near the tropopause at approximately 17 km. The eddy ENSO signal tends to be out-of-phase between low and middle latitudes in both the troposphere and lower stratosphere. Citation: Scherllin-Pirscher, B., C. Deser, S.-P.Ho, C. Chou, W. Randel, and Y.-H. Kuo (2012), The vertical and spatial structure of ENSO in the upper troposphere and lower stratosphere from GPS radio occultation measurements, Geophys.