Search

North China (NC), namely Huabei in Chinese, is one of the most severely polluted regions in China, and the air pollution issues in this region have received a worldwide attention. We performed ground-based Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) measurements at Gucheng, (39°08′N, 115°40′E), a rural site of North China about 110 km southwest of Beijing, from September 2008 to September 2010. The tropospheric vertical column densities (VCDs) of NO2 and SO2 were retrieved using the so-called geometric approximation. The results show that the tropospheric NO2 and SO2 VCDs over NC have nearly the same seasonal variation pattern, with the maximum in winter and minimum in summer, while their diurnal variations are different. We also compared the tropospheric NO2 and SO2 VCDs from our MAX-DOAS measurements with several products of corresponding OMI (Ozone Monitoring Instrument) satellite observations. While in summer good agreement is found, the satellite observations systematically underestimate the tropospheric NO2 in winter over the polluted rural area of NC, probably mostly due to the so called aerosol shielding effect. In contrast, for SO2 no such clear conclusion can be drawn, probably owing to the larger uncertainties from MAX-DOAS and in particular satellite retrievals. This indicates that improvements of the retrieval algorithm for MAX-DOAS and off-line corrections of satellite measurements for the tropospheric SO2 VCDs should be given more emphasis in the future.

A new Monte Carlo atmospheric radiative transfer model is presented which is designed to support the interpretation of UV/vis/near-IR spectroscopic measurements of scattered Sun light in the atmosphere. The integro differential equation describing the underlying transport process and its formal solution are discussed. A stochastic approach to solve the differential equation, the Monte Carlo method, is deduced and its application to the formal solution is demonstrated. It is shown how model photon trajectories of the resulting ray tracing algorithm are used to estimate functionals of the radiation field such as radiances, actinic fluxes and light path integrals. In addition, Jacobians of the former quantities with respect to optical parameters of the atmosphere are analyzed. Model output quantities are validated against measurements, by self-consistency tests and through inter comparisons with other radiative transfer models.

In this article, we present satellite observations of atmospheric sulfur dioxide (SO_2) from volcanic eruptions. Global ozone monitoring experiment (GOME) data for the years 1996–2002 is analyzed using a DOAS based algorithm with the aim of retrieving SO_2 slant column densities (SCD). The retrieval of SO_2 SCD in the UV spectral region is difficult due to strong and interfering ozone absorptions. It is also likely affected by instrumental effects. We investigated these effects in detail to obviate systematic biases in the SO_2 retrieval. A quantitative study of about 20 volcanoes from Italy, Iceland, Congo/Zaire, Ecuador, Japan, Vanuatu Island and Mexico is presented. The focus is on both eruption and out gassing scenarios. We prepared a 7-year mean map (1996–2002) of SO_2 SCD observed by GOME and tabulated the ratios of the maximum SO_2 SCD observed to the average SO_2 SCD as seen in the 7-year mean map. The further aim of this study is to provide information about unknown volcanic eruptions, e.g., Bandai Honshu Japan, Central Islands Vanuatu, Piton de la Fournaise Reunion Island France, Kamchatka region of Russia and from Indonesia especially. The results demonstrate a high sensitivity of the GOME instrument towards SO_2 emissions during both eruption and degassing episodes.

In this article, we present satellite observations of OClO from the years 1995–2002. The focus is on observations of OClO in the Arctic wintertime stratosphere, which are compared to results of the SLIMCAT model and to observations in the Antarctic. In particular, we investigated the beginning and ending of the chlorine activation in the Arctic stratosphere. The Slant Column Densities (SCDs) of OClO increase significantly, when the temperature falls below the threshold for formation of Polar Stratospheric Clouds. The time for decrease of the OClO-SCDs in the deactivation phase (early spring) varies strongly and is related to the degree of denitrification. In the Arctic, chlorine activation can be further increased when there is strong activity of stratospheric mountain waves.

Nitrogen oxides (NO + NO 2 =NO x ) are important trace gases in the troposphere with impact on human health, climate and atmospheric chemistry, e.g. through their role in ozone production. Therefore a better understanding of the strength of the various sources (fossil fuel combustion, biomass burning, soil emissions, lightning) is desirable. NO x produced by lightning contributes approx. 12%, i.e. 5 (2–20) T g [N]/year [Atmos. Environ. 31 (1997) 1735; EULINOX – The European Lightning Nitrogen Oxides Project. DLR – Forschungsbericht 2000-28, 2000], of the totally produced nitrogen oxides. An uncertainty of one order of magnitude remains. Here we present an estimation of lightning produced NO x using satellite data. Lightning activity is monitored by the Lightning Imaging Sensor since November 1997. The same time span is also covered by NO 2 measurements from the Global Ozone Monitoring Experiment. This allows a statistical approach. In this study we relate lightning frequency and the tropospheric vertical column densities of NO 2 over Central Australia, where other NO x sources have only minor contribution. By analyzing the correlation of lightning activity with the vertical column densities of NO 2 we estimate the globally produced lightning NO x to be ∼2.8 (0.8–14) T g [N]/year. Despite the many uncertainties involved in NO 2 retrieval (e.g. profile information, cloud influence), this value shows a good agreement with literature.

In this paper we present data on the variation of tropospheric BrO, that is connected with the spring time ozone depletion in polar regions. For this study we use data derived from the Global Ozone Monitoring Experiment (GOME) for the years 1996–2001. We especially focus on the possible detection of trends in the extent of coverage of polar regions by BrO and on the time series of BrO abundances. For this purpose we calculated monthly means during polar spring of the areas that are covered with BrO exceeding certain thresholds. It turns out that in the timeseries of total, i.e. tropospheric and stratospheric, BrO column densities there is, up to now, no clear trend identifiable. In contrast, the analysis of areas covered by high concentrations of tropospheric BrO (columns >5.5 × 1013 molecules/cm2) is considerably expanding (about 10% per year during 1996–2000) in the northern hemisphere in the comparison of monthly means during polar spring, which is possibly due to an anthropogenic effect on the climate system.