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It is essential to understand the data quality of 10+ year OMI ozone product and impacts of the “Row Anomaly (RA)”. We validate the OMI ozone-profile (PROFOZ) product from Oct. 2004 to Dec. 2014 against ozonesonde observations globally. Generally, OMI has good agreement with ozonesondes. The spatiotemporal variation of retrieval performance suggests the need to improve OMI’s radiometric calibration especially during the post-RA period to maintain the long-term stability.

Formaldehyde is a primary and secondary air pollutant. As an intermediate product of hydrocarbon photooxidn., it contributes to the formation of photochem. pollution in urban areas. In addn., chronic or acute exposure to HCHO (a possible carcinogen) constitutes an important health hazard. Differential optical absorption spectroscopy (DOAS) is one of the best-suited techniques for monitoring formaldehyde. Within the frame of a European Union project, a field measurement campaign (PIPAPO) was carried out from May to June, 1998, in the Milan, Italy, area. During PIPAPO, a large no. of air pollutants, including formaldehyde, were monitored at several sites from Milan to the Swiss Alps foothills. Located at Seregno (25 km north of downtown Milan), EPFL (the Ecole Polytechnique Federale de Lausanne) carried out formaldehyde measurements by DOAS and performed intercomparison DNPH (2,4-dinitrophenylhydrazine) samples, which were analyzed at JRC (the Joint Research Center). Despite having different spatial and time resoln., DOAS and DNPH measurements of formaldehyde compare fairly well. The formaldehyde concn. time series retrieved from DOAS were analyzed with respect to the meteorol. conditions, particularly regarding heterogeneous removal processes, and the concn. of other air pollutants assocd. with formaldehyde emission and prodn. Pollutant dynamics calcns., made with a 3-dimensional photochem. grid (Eulerian) model over a wide spatial domain, were compared to the measurements and provided a basis for the interpretation of the formaldehyde measurements performed during one of PIPAPO's intensive observation periods (IOP).

The Grenoble metropolitan area located in the French Alps with more than 400 thousand inhabitants suffers from periods of high ozone (O3) concns. in summertime. Grenoble is moreover located in the Y shaped convergence of three deep valleys with surrounding mountains up to 3,000 m above sea level (asl) leading to a very complex wind pattern. During summer 1999, a major field campaign GRENOble PHOTochem. (GRENOPHOT) involving std. ground based stations, LIDAR, aircraft, DOAS, microwave windprofilers was carried out in order to obtain the measurements needed for model validation. The air quality model METeorol. PHOtochem. MODel (METPHOMOD) developed at the University of Bern and at the Swiss Federal Institute of Technol. at Lausanne, was used to investigate the dynamic characteristics of air pollution in the Grenoble area during GRENOPHOT. The lumped chem. mechanism Regional Atm. Chem. Mechanism (RACM) was used for the calcn. A one-way nesting technique was used in which the large grid is a squared 198 km one with a grid resoln. of 6 * 6 km and the small one is a rectangular 78 * 68 km with a grid resoln. of 2 * 2 km. There are 24 vertical levels up to 8,000 m asl. The meteorol. and chem. simulations were validated with ground and vertical profiles measurements performed during the Intensive Observation Period (IOP) July, 25-27, when the O3 concns. reached up to 95 ppb. Both the spatial as well as the temporal variabilities of the simulated O3 concns. correspond reasonably well to the measured values. They caught the O3 plume south of Grenoble. The model results indicate a lower Planet Boundary Layer (PBL) height than the LIDAR obsd. The PBL calcd. by the model is about 2,100 m, whereas the LIDAR indicates about 2,400 m. The results show that the PBL in mountain terrain is higher than those found over flat terrain. A specific vertical stratification of the atm. at day and night time is obsd. during typical photochem. episodes. Highest O3 values appear in the south at 25 km downwind the city center, and the results show that about 32 ppb of fresh O3 are generated in the Grenoble plume.

A new lidar for the measurement of tropospheric ozone is proposed, based on the differential analysis of the Raman backscattered signals on nitrogen and oxygen, which is far less sensitive to the aerosols than the classical DIAL system. Using a third Raman channel, the system is able to measure the water vapor mixing ratio simultaneously. The transmitting section of the instrument is composed of a single wavelength at 266 nm, generated by a quadrupled Nd:YAG laser, while the receiving section is the combination of a 20 cm Newton telescope, a polychromator, custom made band pass filters and miniature photomultiplier, giving a compact and efficient optical layout. The cross-talk between the different channels, and the rejection of the 266 nm wavelength have been measured in detail and will be presented. Time series of ozone and water vapor vertical profile during some days have been performed in the early spring 99.

Recent research works show that wastewater treatment plants may contribute significantly to the total emission of volatile org. compds. (VOCs) in urban areas. In order to investigate this contribution, a measurement campaign was carried out during Sept., 1999, in the Lausanne, Switzerland, area. The concns. of monocyclic arom. hydrocarbons (MAHs) over a wastewater treatment plant at Lausanne were monitored by differential optical absorption spectroscopy (DOAS) and gas chromatog. with a flame ionization detector (GC-FID). An FID was used for monitoring the overall concn. of nonmethane hydrocarbons (NMHCs). The local meteorol. conditions were also measured. The concns. of benzene, toluene, ethylbenzene, xylenes, 1,2,4-trimethylbenzene, and phenol over the wastewater treatment plant as measured by DOAS and GC-FID are compared. In addn., based upon the results of a recent field expt., the impact of the oxygen interference on DOAS measurements of arom. compds. is addressed. The MAH concn. time series and its relation to that of NMHCs, as well as to the meteorol. conditions, are presented. The VOC release and prodn. phenomena involved in the wastewater and sludge treatment processes are analyzed using complementary measurements of arom. compds. in wastewater and gas processing streams.

Applied Physics B, 78 (2), ISSN:0946-2171, ISSN:1432-0649, ISSN:0721-7269, ISSN:0340-3793