bluuebunny/crossref_metadata_2025 huggingface dataset:
Implementation and testing of a simple data assimilation algorithm in the regional air pollution forecast model, DEOM
Authors: Frydendall J. , Brandt J. , Christensen J. H.
Published: April 2010

Abstract. A simple data assimilation algorithm based on statistical interpolation has been developed and coupled to a long-range chemistry transport model, the Danish Eulerian Operational Model (DEOM), applied for air pollution forecasting at the National Environmental Research Institute (NERI), Denmark. In this paper, the algorithm and the results from experiments designed to find the optimal setup of the algorithm are described. The algorithm has been developed and optimized via eight different experiments where the results from different model setups have been tested against measurements from the EMEP (European Monitoring and Evaluation Programme) network covering a half-year period, April–September 1999. The best performing setup of the data assimilation algorithm for surface ozone concentrations has been found, including the combination of determining the covariances using the Hollingsworth method, varying the correlation length according to the number of adjacent observation stations and applying the assimilation routine at three successive hours during the morning. Improvements in the correlation coefficient in the range of 0.1 to 0.21 between the results from the reference and the optimal configuration of the data assimilation algorithm, were found. The data assimilation algorithm will in the future be used in the operational THOR integrated air pollution forecast system, which includes the DEOM.
Photoinduced oxidation of sea salt halides by aromatic ketones: a source of halogenated radicals
Authors: Jammoul A. , Dumas S. , D'Anna B. , George C.
Published: April 2010

Abstract. The interactions between benzophenone triplet state and halide anion species (Cl−, Br− and I−) have been studied by laser flash photolysis (at 355 nm) in aqueous solutions at room temperature. The decay of the triplet state of benzophenone was followed at 525 nm. Triplet lifetime measurements provided rate constants, kq (M−1 s−1), close to diffusion controlled limit for iodide (~8×109 M−1 s−1), somewhat less for bromide (~3×108 M−1 s−1) and much lower for chloride (>106 M−1 s−1). The halide (X−) quenches the triplet state, and a product, having a transient absorption at 355 nm and a lifetime much longer than that of the benzophenone triplet state, is formed. This transient absorption feature matches those of the corresponding radical anion (X2−). We therefore suggest that such reactive quenching can be a photosensitized source of halogen in the atmosphere and represents a driving force for the chemical oxidation of the oceanic surface.
Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations
Authors: Basart S. , Pérez C. , Cuevas E. , Baldasano J. M. , Gobbi G. P.
Published: April 2010

Abstract. We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994–2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors in order to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of the Ångstrøm exponent (α) and its spectral curvature. Plotting data in these coordinates allows to infer aerosol fine mode size (Rf) and fractional contribution (η) to total Aerosol Optical Depth (AOD) and separate AOD growth due to fine-mode aerosol humidification and/or coagulation from AOD growth due to the increase in coarse particles or cloud contamination. Our results confirm the robustness of this graphical method. Large mineral dust is the most important constituent in Northern Africa and Middle East; and under specific meteorological conditions, its transport to Europe is observed from spring to autumn. Small pollution particles are abundant in sites close to urban and industrial areas of Continental and Eastern Europe and Middle East; as well as, important contributions of biomass burning are observed in the sub-Sahel region in winter. Dust is usually found to mix with these fine, pollution aerosols.
Characterization of volatile organic compounds (VOCs) in Asian and North American pollution plumes during INTEX-B: identification of specific Chinese air mass tracers
Authors: Barletta B. , Meinardi S. , Simpson I. J. , Atlas E. L. , Beyersdorf A. J. , Baker A. K. , Blake N. J. , Yang M. , Midyett J. R. , Novak B. J. , McKeachie R. J. , Fuelberg H. E. , Sachse G. W. , Avery M. A. , Campos T. , Weinheimer A. J. , Sherwood Rowland F. , Blake D. R.
Published: April 2010

Abstract. We present results from the Intercontinental Chemical Transport Experiment – Phase B (INTEX-B) aircraft mission conducted in spring 2006. By analyzing the mixing ratios of volatile organic compounds (VOCs) measured during the second part of the field campaign, together with kinematic back trajectories, we were able to identify five plumes originating from China, four plumes from other Asian regions, and three plumes from the United States. To identify specific tracers for the different air masses, we focused on characterizing the VOC composition of these different pollution plumes. The Chinese and other Asian air masses were significantly enhanced in carbonyl sulfide (OCS) and methyl chloride (CH3Cl), while all CFC replacement compounds were elevated in US plumes, particularly HCFC-134a. Although elevated mixing ratios of Halon-1211 were measured in some of the Chinese plumes, several measurements at background levels were also observed. After analyzing the VOC distribution in the Chinese pollution plumes and the correlations among selected compounds, we suggest the use of a suite of species, rather than the use of a single gas, to be used as specific tracers of Chinese air masses (namely OCS, CH3Cl, 1,2-dichloroethane, and Halon-1211). In an era of constantly changing halocarbon usage patterns, this suite of gases best reflects new emission characteristics from China.
Significant variations of trace gas composition and aerosol properties at Mt. Cimone during air mass transport from North Africa – contributions from wildfire emissions and mineral dust
Authors: Cristofanelli P. , Marinoni A. , Arduini J. , Bonafè U. , Calzolari F. , Colombo T. , Decesari S. , Duchi R. , Facchini M. C. , Fierli F. , Finessi E. , Maione M. , Chiari M. , Calzolai G. , Messina P. , Orlandi E. , Roccato F. , Bonasoni P.
Published: April 2010

Abstract. High levels of trace gas (O3 and CO) and aerosol (BC, fine and coarse particles) concentrations, as well as high scattering coefficient (σs) values, were recorded at the regional GAW-WMO station of Mt. Cimone (MTC, 2165 m a.s.l., Italy) during the period 26–30 August 2007. Analysis of air-mass circulation, aerosol chemical characterization and trace gas and aerosol emission ratios (ERs), showed that high O3 and aerosol levels were likely linked to (i) the transport of anthropogenic pollution from Northern Italy, and (ii) the advection of air masses rich in mineral dust and biomass burning (BB) products from North Africa. In particular, during the advection of air masses from North Africa, the CO and aerosol levels (CO: 175 ppbv, BC: 1015 ng/m3, fine particle: 83.8 cm−3, σs: 84.5 Mm−1) were even higher than during the pollution event (CO: 138 ppbv, BC: 733 ng/m3, fine particles: 41.5 cm−3, σs: 44.9 Mm−1). Moreover, despite the presence of mineral dust able to significantly affect the O3 concentration, the analysis of ERs showed that the BB event represented an efficient source of fine aerosol particles (e.g. BC), but also of the O3 recorded at MTC. The results suggest that events of mineral dust mobilization and wildfire emissions over North Africa could significantly influence radiative properties (as deduced from σs observations at MTC) and air quality over the Mediterranean basin and Northern Italy. Since in the future it is expected that wildfire and Saharan dust transport frequency could increase in the Mediterranean basin due to more frequent and severe droughts, similar events will possibly play an important role in influencing the climate and the tropospheric composition over South Europe.
Quantitative long-term measurements of VOC concentrations by PTR-MS: annual cycle at a boreal forest site
Authors: Ruuskanen T. M. , Taipale R. , Rinne J. , Kajos M. K. , Hakola H. , Kulmala M.
Published: April 2010

Abstract. Atmospheric concentrations of volatile organic compounds (VOCs) vary diurnally, seasonally and annually. Therefore continuous long-term measurements are needed to properly describe the atmospheric levels of these chemically reactive compounds. We conducted on-line measurements of atmospheric volume mixing ratios of several VOCs in the European boreal region with a proton transfer reaction – mass spectrometer (PTR-MS) over a 15 month period. The measurements lasted from spring 2006 to fall 2007 and were conducted at SMEAR II station in south-western Finland. The measured compounds included for example methanol, acetone, sum of isoprene and 2-methyl-3-buten-2-ol (MBO), monoterpenes and benzene. The VOC mixing ratios were measured inside and above canopy, during every second or third hour. The PTR-MS was calibrated regularly and background signals of VOCs were measured every second or third hour from the zero air and subtracted from the measured volume mixing ratio. In the continuous measurements at moderate VOC mixing ratios we observed that the PTR-MS has to be calibrated and SEM operation voltage checked regularly, at least twice a month to ensure reliable measurements. Of the measured VOCs, methanol and acetone were the most abundant ones, their volume mixing ratio medians were in the order of 1 ppbv. Volume mixing ratios of methanol, acetone, isoprene-MBO and monoterpenes were high during summer and low in winter indicating mostly biogenic or photochemical local or regional origin. Benzene behaved in the opposite way, while seasonal variation of acetaldehyde and methacrolein-methylvinylketone (MACR-MVK) was less profound. Methanol, acetone, isoprene and monoterpene volume mixing ratios had clear diurnal patterns during summers, while the mixing ratios of other VOCs did not exhibit this behavior. During winter we did not observe systematic diurnal cycles in the VOC volume mixing ratios.
CALIPSO polar stratospheric cloud observations: second-generation detection algorithm and composition discrimination
Authors: Pitts M. C. , Poole L. R. , Thomason L. W.
Published: April 2010

Abstract. This paper focuses on polar stratospheric cloud (PSC) measurements by the CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) lidar system onboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) spacecraft, which has been operating since June 2006. We describe a second-generation PSC detection algorithm that utilizes both the CALIOP 532-nm scattering ratio (ratio of total-to-molecular backscatter coefficients) and 532-nm perpendicular backscatter coefficient measurements for cloud detection. The inclusion of the perpendicular backscatter measurements enhances the detection of tenuous PSC mixtures containing low number densities of solid particles and leads to about a 15% increase in PSC areal coverage compared with our original algorithm. In addition, the new algorithm allows discrimination of PSCs by composition in terms of their ensemble backscatter and depolarization in a manner analogous to that used in previous ground-based and airborne lidar PSC studies. Based on theoretical optical calculations, we define four CALIPSO-based composition classes which we call supercooled ternary solution (STS), ice, and Mix1 and Mix2, denoting mixtures of STS with nitric acid trihydrate (NAT) particles in lower or higher number densities/volumes, respectively. We examine the evolution of PSCs for three Antarctic and two Arctic seasons and illustrate the unique attributes of the CALIPSO PSC database. These analyses show substantial interannual variability in PSC areal coverage and also the well-known contrast between the Antarctic and Arctic. The CALIPSO data also reveal seasonal and altitudinal variations in Antarctic PSC composition, which are related to changes in HNO3 and H2O observed by the Microwave Limb Sounder on the Aura satellite.
First year of upper tropospheric integrated content of CO2 from IASI hyperspectral infrared observations
Authors: Crevoisier C. , Chédin A. , Matsueda H. , Machida T. , Armante R. , Scott N. A.
Published: April 2010

Abstract. Simultaneous observations from the Infrared Atmospheric Sounding Interferometer (IASI) and from the Advanced Microwave Sounding Unit (AMSU), launched together onboard the European MetOp platform in October 2006, are used to retrieve an upper tropospheric content of carbon dioxide (CO2) covering the range 11–15 km (100–300 hPa), in clear-sky conditions, in the tropics, over sea, for the first year of operation of MetOp (January 2008–December 2008). With its very high spectral resolution, IASI provides fourteen channels in the 15 μm band highly sensitive to CO2 with reduced sensitivities to other atmospheric variables. IASI observations, sensitive to both CO2 and temperature, are used in conjunction with AMSU observations, only sensitive to temperature, to decorrelate both signals through a non-linear inference scheme based on neural networks. A key point of this approach is that no use is made of prior information in terms of CO2 seasonality, trend, or geographical patterns. The accuracy of the retrieval is estimated to be about 2.0 ppmv (~0.5%) for a 5°×5° spatial resolution on a monthly time scale. Features of the retrieved CO2 space-time distribution include: (1) a strong seasonal cycle of 4 ppmv in the northern tropics with a maximum in June–July and a minimum in September–October. This cycle is characterized by a backward two-months lag as compared to the surface, by a backward one-month lag as compared to measurements performed at 11 km, and by a forward one-month lag as compared to observations performed at the tropopause (16 km). This is likely due to the time-lag of CO2 cycle while transported from the surface to the upper troposphere; (2) a more complex seasonal cycle in the southern tropics, in agreement with in-situ measurements; (3) a latitudinal variation of CO2 shifting from a South-to-North increase of 3.5 ppmv in boreal spring to a South-to-North decrease of 1.5 ppmv in the fall, in excellent agreement with tropospheric aircraft measurements; (4) signatures of CO2 emissions (such as biomass burning) transported to the troposphere. In addition to bringing an improved view of CO2 distribution, these results from IASI should provide an additional means to observe and understand atmospheric transport pathways of CO2 from the surface to the upper troposphere.
Mexico City aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 1: Fine particle composition and organic source apportionment
Authors: Aiken A. C. , Salcedo D. , Cubison M. J. , Huffman J. A. , DeCarlo P. F. , Ulbrich I. M. , Docherty K. S. , Sueper D. , Kimmel J. R. , Worsnop D. R. , Trimborn A. , Northway M. , Stone E. A. , Schauer J. J. , Volkamer R. , Fortner E. , de Foy B. , Wang J. , Laskin A. , Shutthanandan V. , Zheng J. , Zhang R. , Gaffney J. , Marley N. A. , Paredes-Miranda G. , Arnott W. P. , Molina L. T. , Sosa G. , Jimenez J. L.
Published: April 2010

Abstract. Submicron aerosol was analyzed during the MILAGRO field campaign in March 2006 at the T0 urban supersite in Mexico City with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and complementary instrumentation. Mass concentrations, diurnal cycles, and size distributions of inorganic and organic species are similar to results from the CENICA supersite in April 2003 with organic aerosol (OA) comprising about half of the fine PM mass. Positive Matrix Factorization (PMF) analysis of the high resolution OA spectra identified three major components: chemically-reduced urban primary emissions (hydrocarbon-like OA, HOA), oxygenated OA (OOA, mostly secondary OA or SOA), and biomass burning OA (BBOA) that correlates with levoglucosan and acetonitrile. BBOA includes several very large plumes from regional fires and likely also some refuse burning. A fourth OA component is a small local nitrogen-containing reduced OA component (LOA) which accounts for 9% of the OA mass but one third of the organic nitrogen, likely as amines. OOA accounts for almost half of the OA on average, consistent with previous observations. OA apportionment results from PMF-AMS are compared to the PM2.5 chemical mass balance of organic molecular markers (CMB-OMM, from GC/MS analysis of filters). Results from both methods are overall consistent. Both assign the major components of OA to primary urban, biomass burning/woodsmoke, and secondary sources at similar magnitudes. The 2006 Mexico City emissions inventory underestimates the urban primary PM2.5 emissions by a factor of ~4, and it is ~16 times lower than afternoon concentrations when secondary species are included. Additionally, the forest fire contribution is underestimated by at least an order-of-magnitude in the inventory.
A simple model for cloud radiative forcing
Authors: Corti T. , Peter T.
Published: April 2010

Abstract. We present a simple model for the longwave and shortwave cloud radiative forcing based on the evaluation of extensive radiative transfer calculations. The simplicity of the model equations fosters the understanding on how clouds affect the Earth's energy balance. In comparison with results from a comprehensive radiative transfer model, the accuracy of our parameterization is typically better than 20%. We demonstrate the usefulness of our model using the example of tropical cirrus clouds. We conclude that possible applications for the model include the fast estimate of cloud radiative forcing, the evaluation of the sensitivity to changes in environmental conditions, and as a tool in education.
IASI measurements of reactive trace species in biomass burning plumes
Authors: Coheur P.-F. , Clarisse L. , Turquety S. , Hurtmans D. , Clerbaux C.
Published: April 2010

Abstract. This work presents observations of a series of short-lived species in biomass burning plumes from the Infrared Atmospheric Sounding Interferometer (IASI), launched onboard the MetOp-A platform in October 2006. The strong fires that have occurred in the Mediterranean Basin – and particularly Greece – in August 2007, and those in Southern Siberia and Eastern Mongolia in the early spring of 2008 are selected to support the analyses. We show that the IASI infrared spectra in these fire plumes contain distinctive signatures of ammonia (NH3), ethene (C2H4), methanol (CH3OH) and formic acid (HCOOH) in the atmospheric window between 800 and 1200 cm−1, with some noticeable differences between the plumes. Peroxyacetyl nitrate (CH3COO2NO2, abbreviated as PAN) was also observed in some plumes and a tentative assignment of a broadband absorption spectral feature to acetic acid (CH3COOH) is made. For several of these species these are the first reported measurements made from space in nadir geometry. The IASI measurements are analyzed for plume height and concentration distributions of NH3, C2H4 and CH3OH. The Greek fires are studied in greater detail for the days associated with the largest emissions. In addition to providing information on the spatial extent of the plume, the IASI retrievals allow an estimate of the total mass emissions for NH3, C2H4 and CH3OH. Enhancement ratios are calculated for the latter relative to carbon monoxide (CO), giving insight in the chemical processes occurring during the transport, the first day after the emission.
Black carbon over Mexico: the effect of atmospheric transport on mixing state, mass absorption cross-section, and BC/CO ratios
Authors: Subramanian R. , Kok G. L. , Baumgardner D. , Clarke A. , Shinozuka Y. , Campos T. L. , Heizer C. G. , Stephens B. B.
Published: April 2010

Abstract. A single particle soot photometer (SP2) was operated on the NCAR C-130 during the MIRAGE campaign (part of MILAGRO), sampling black carbon (BC) over Mexico. The highest BC concentrations were measured over Mexico City (sometimes as much as 2μg/m3) and over hill-fires to the south of the city. As expected, older, diluted air masses had lower BC concentrations. A comparison of carbon monoxide (CO) and BC suggests a CO background of around 65 ppbv, and a background-corrected BC/COnet ratio of 3.1 (ng/m3 STP)/ppbv (±25%). This ratio is similar for fresh emissions over Mexico City, as well as for aged airmasses. Comparison of light absorption measured with a particle soot absorption photometer (PSAP) and the SP2 BC suggests a BC mass-normalized absorption cross-section (MAC) of 10.3 m2g−1 (±30%) at 660 nm (or 12.4 m2g−1 @ 550 nm, assuming MAC is inversely dependent on wavelength). This appears independent of aging and similar to the expected absorption cross-section for aged BC, but values, particularly in fresh emissions, could be biased high due to instrument artifacts. SP2-derived BC coating indicators show a prominent thinly-coated BC mode over the Mexico City Metropolitan Area (MCMA), while older air masses show both thinly-coated and thickly-coated BC. BC mass per particle of the thinly-coated mode appears to increase as the air mass ages, possibly due to coagulation and/or increased coating of the particles containing smaller BC masses. Differences in the coating indicator patterns for similarly-aged air masses may be due to differences in atmospheric processing on each day, including mixing with non-MCMA air masses.
An assessment of the accuracy of the RTTOV fast radiative transfer model using IASI data
Authors: Matricardi M.
Published: April 2010

Abstract. IASI measurements of spectral radiances made between the 1 April 2008 and the 15 April 2008 are compared with simulations performed using the RTTOV fast radiative transfer model utilizing regression coefficients based on different line-by-line models. The comparisons are performed within the framework of the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System using fields of temperature, water vapour and ozone obtained from short-range forecasts. Simulations are performed to assess the accuracy of the RTTOV computations and investigate relative differences between the line-by-line models and the quality of the spectroscopic databases on which the RTTOV coefficients are based.
A comparison of water uptake by aerosols using two thermodynamic models
Authors: Xu L. , Penner J. E. , Metzger S. , Lelieveld J.
Published: April 2010

Abstract. A comprehensive comparison between two aerosol thermodynamic equilibrium models used in chemistry-climate simulations, EQUISOLV II and EQSAM3, is conducted for various relative humidities and chemical compositions. Our results show that the concentration of total particulate matter as well as the associated aerosol liquid water content predicted by these two models is comparable for all conditions, which is important for radiative forcing estimates. The normalized absolute difference in the concentration of total particulate matter is 6% on average for all 200 conditions studied, leading to a regression coefficient of about 0.8 for the water associated with the aerosol between these two models. Relatively large discrepancies occur, however, at high ammonium, low nitrate/sodium concentrations at low and medium relative humidities (RH<60–70%), which is analyzed and discussed in detail. In addition, the prediction of the partitioning of ammonium and nitrate is investigated under realistic atmospheric conditions. The data collected during the Mediterranean Intensive Oxidant Study (MINOS) campaign are simulated using both models. The results show that both models can reproduce the concentration of total particulate matter for 90% of the time within a factor of 2, while the predicted concentration of aerosol water by these two models is significantly correlated. The largest difference exists near RH's of 70–80% which is the RH range for the transition of mixed ammonium salts from the solid to the liquid phase.
Satellite observations and modelling of transport in the upper troposphere through the lower mesosphere during the 2006 major stratospheric sudden arming
Authors: Manney G. L. , Harwood R. S. , MacKenzie I. A. , Minschwaner K. , Allen D. R. , Santee M. L. , Walker K. A. , Hegglin M. I. , Lambert A. , Pumphrey H. C. , Bernath P. F. , Boone C. D. , Schwartz M. J. , Livesey N. J. , Daffer W. H. , Fuller R. A.
Published: April 2010

Abstract. An unusually strong and prolonged stratospheric sudden warming (SSW) in January 2006 was the first major SSW for which globally distributed long-lived trace gas data are available covering the upper troposphere through the lower mesosphere. We use Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) data, the SLIMCAT Chemistry Transport Model (CTM), and assimilated meteorological analyses to provide a comprehensive picture of transport during this event. The upper tropospheric ridge that triggered the SSW was associated with an elevated tropopause and layering in trace gas profiles in conjunction with stratospheric and tropospheric intrusions. Anomalous poleward transport (with corresponding quasi-isentropic troposphere-to-stratosphere exchange at the lowest levels studied) in the region over the ridge extended well into the lower stratosphere. In the middle and upper stratosphere, the breakdown of the polar vortex transport barrier was seen in a signature of rapid, widespread mixing in trace gases, including CO, H2O, CH4 and N2O. The vortex broke down slightly later and more slowly in the lower than in the middle stratosphere. In the middle and lower stratosphere, small remnants with trace gas values characteristic of the pre-SSW vortex lingered through the weak and slow recovery of the vortex. The upper stratospheric vortex quickly reformed, and, as enhanced diabatic descent set in, CO descended into this strong vortex, echoing the fall vortex development. Trace gas evolution in the SLIMCAT CTM agrees well with that in the satellite trace gas data from the upper troposphere through the middle stratosphere. In the upper stratosphere and lower mesosphere, the SLIMCAT simulation does not capture the strong descent of mesospheric CO and H2O values into the reformed vortex; poor CTM performance in the upper stratosphere and lower mesosphere results primarily from biases in the diabatic descent in assimilated analyses.
Concurrent observations of air pollutants at two sites in the Pearl River Delta and the implication of regional transport
Authors: Guo H. , Jiang F. , Cheng H. R. , Simpson I. J. , Wang X. M. , Ding A. J. , Wang T. J. , Saunders S. M. , Wang T. , Lam S. H. M. , Blake D. R. , Zhang Y. L.
Published: April 2010

Abstract. An intensive field measurement study was conducted simultaneously at a site within the inland Pearl River Delta (PRD) region (WQS) and a site in Hong Kong (TC) between 22 October and 1 December 2007. Ambient air pollutants measured included O3, NOx, CO, SO2, NMHCs, and carbonyls. The purpose is to improve our understanding of the interplay among local and regional air pollutants in the Hong Kong area, and the influence of regional transport on local air pollutants. The results indicate that the mean levels of air pollutants at the WQS site were much higher than those at the TC site, except NOx. Elevated CO levels were measured when the northerly monsoons enhanced mixing ratios at both sites, whereas high O3 episodes were usually observed when weather systems were relatively stable. Thirteen O3 episode days (daily O3 peak in excess of 122 ppbv) were monitored at WQS during the study period, while only 2 days were recorded at TC. The diurnal variations of air pollutants at the two sites were found to be rather different, suggesting different local and regional contributions. Ratio analyses for VOCs revealed that the air masses arriving at WQS were more aged than those arriving at TC, confirmed by the back trajectories analysis. In addition, the influence of regional transport from eastern China on the primary pollutants of Hong Kong was noticeable, whereas the air masses from the inland PRD region (e.g. Dongguan) had significant influence on the air pollutants at WQS. These results confirm that regional transport of air pollution has a complex and significant impact on local air pollutants in this region.
Verification of precipitation forecasts by the DWD limited area model LME over Cyprus
Authors: Savvidou K. , Michaelides S. C. , Orphanou A. , Constantinides P. , Schulz J.-P. , Voigt U. , Savvides M.
Published: April 2010

Abstract. A comparison is made between the precipitation forecasts by the non-hydrostatic limited area model LME of the German Weather Service (DWD) and observations from a network of rain gauges in Cyprus. This is a first attempt to carry out a preliminary verification and evaluation of the LME precipitation forecasts over the area of Cyprus. For the verification, model forecasts and observations were used covering an eleven month period, from 1/2/2005 till 31/12/2005. The observations were made by three Automatic Weather Observing Systems (AWOS) located at Larnaka and Paphos airports and at Athalassa synoptic station, as well as at 6, 6 and 8 rain gauges within a radius of about 30 km around these stations, respectively. The observations were compared with the model outputs, separately for each of the three forecast days. The "probability of detection" (POD) of a precipitation event and the "false alarm rate" (FAR) were calculated. From the selected cases of the forecast precipitation events, the average forecast precipitation amounts in the area around the three stations were compared with the measured ones. An attempt was also made to evaluate the model's skill in predicting the spatial distribution of precipitation and, in this respect, the geographical position of the maximum forecast precipitation amount was contrasted to the position of the corresponding observed maximum. Maps with monthly precipitation totals observed by a local network of 150 rain gauges were compared with the corresponding forecast precipitation maps.
Instability and its relation to precipitation over the Eastern Iberian Peninsula
Authors: Iturrioz I. , Hernández E. , Ribera P. , Queralt S.
Published: April 2010

Abstract. Synoptic situations producing rainfall at four rawinsonde observatories at eastern Spain are classified as stratiform or convective depending on dynamic and thermodynamic instability indices. Two daily radiosonde and daily-accumulated precipitation data from four observatories in Eastern Spain are used: Madrid-Barajas (MB), Murcia (MU), Palma de Mallorca (PA) and Zaragoza (ZA). We calculated two thermodynamic instability indices from radiosonde data: CAPE and LI. Likewise, from ERA40 reanalysis data we have calculated the Q vector divergence over the Iberian Peninsula and Balearic Islands, as a parameter describing dynamical instability. Synoptic situations producing rainfall were classified as convective or stratiform, satisfying a criterion based on the values of dynamic and thermodynamic indices at each observatory. It is observed that the number of days with stratiform precipitation related to the total number of precipitation days follows a consistent annual pattern.
On extreme daily precipitation totals at Athens, Greece
Authors: Nastos P. T. , Zerefos C. S.
Published: April 2010

Abstract. The paper studies changes in daily precipitation records at the National Observatory, Athens, during the period 1891–2004. This is the longest available time series of precipitation for Greece. The results show that both the shape and scale parameter of a fitted two parameter gamma distribution for the last two decades do show a significant difference of these parameters, when compared to any previous period from the 1890s through the 1970s. Also important changes are observed in daily precipitation totals exceeding various thresholds such as 10, 20, 30 and 50 mm. More specifically, a negative trend in the number of wet days (remarkable after 1968) and a positive trend in extreme daily precipitation are evident. The changes of heavy and extreme precipitation events in this part of SE Europe have significant environmental consequences which cause considerable damage and loss of life.
A new module for the tracking of radar-derived precipitation with model-derived winds
Authors: Winterrath T. , Rosenow W.
Published: April 2010

Abstract. A new approach for the nowcasting of precipitation has been developed at the German Weather Service combining extrapolation techniques and Numerical Weather Prediction (NWP) for a lead time range of several hours. Radar-derived precipitation fields serve as input data for a tracking algorithm using model-derived wind data. The composite precipitation field is derived from the precipitation scans which are performed every five minutes at the 16 German radar stations. The data are corrected from clutter and shading effects. The tracking of this radar-derived precipitation field is performed using the temporally and spatially resolved horizontal wind fields at different pressure levels provided by the Local Model Europe (LME). The optimal wind field is derived from minimization of the least-squares difference between a linear combination of model wind data from different pressure levels and the linear displacement vectors calculated via pattern recognition from previous radar measurements. An area-preserving displacement of the precipitation fields is realized by eliminating the wind field divergence and by omitting the dynamical evolution of the precipitation fields. Advection is performed using the fourth-order Bott scheme. Forecasted data comprise precipitation rates for every five minutes lead time as well as hourly sums of precipitation. The verification of a case study's results against radar precipitation measurements lead to a mean Equitable Threat Score (ETS) of 70%, 46%, and 38% for the first, second, and third forecast hour, respectively.
Measurement of solid precipitation with an optical disdrometer
Authors: Lempio G. E. , Bumke K. , Macke A.
Published: April 2010

Abstract. A study about measurements of solid precipitation using an optical disdrometer is presented. The optical disdrometer is an improved version of the ODM 470 disdrometer. It allows to measure hydrometeors within a size range of 0.4 to 22 mm in diameter. The main advantage of this instrument is its ability to estimate accurately precipitation even under strong wind conditions (Großklaus, 1996). To measure solid precipitation a geometrical model was developed to determine the mean cross-sectional area of snow crystals for different predefined shapes and sizes. It serves to develop an algorithm, which relates the mean cross sectional area of snow crystals to their maximum dimension, liquid water content, and terminal velocity. The algorithm was applied to disdrometer measurements during winter 1999/2000 in Uppsala/Sweden. Resulting precipitation was compared to independent measurements of a Geonor gauge and to manual measurements. In terms of daily precipitation the disdrometer shows a reliable performance.
Spatio-temporal water body and vegetation changes in the Nile swamps of southern Sudan
Authors: Petersen G. , Abeya J. A. , Fohrer N.
Published: April 2010

Abstract. An assessment to describe and quantify the extent of changes in the channel and lagoon system of the Sudd was carried out using Landsat satellite images of 1973, 1979, 1997 and 2002. Using supervised classification and visual interpretation after referencing the images, the water bodies for a representative area between Bor and Shambe (a stretch of 150 km) were delineated. The resulting files were compared to establish and quantify changes in-between the years and as well compared to Lake Victoria outflow data to assess a likely correlation which was found for the largely water level dependent lagoon system. Changes in the channel system were interpreted to happen in a certain pattern but the extent of changes could not be correlated to the outflow data as they are influenced by other, here not considered factors like wind drift and channel blockages by vegetation.
Sensitivity and uncertainty in flood inundation modelling – concept of an analysis framework
Authors: Weichel T. , Pappenberger F. , Schulz K.
Published: April 2010

Abstract. After the extreme flood event of the Elbe in 2002 the definition of flood risk areas by law and their simulation became more important in Germany. This paper describes a concept of an analysis framework to improve the localisation and duration of validity of flood inundation maps. The two-dimensional finite difference model TrimR2D is used and linked to a Monte-Carlo routine for parameter sampling as well as to selected performance measures. The purpose is the investigation of the impact of different spatial resolutions and the influence of changing land uses in the simulation of flood inundation areas. The technical assembling of the framework is realised and beside the model calibration, first tests with different parameter ranges were done. Preliminary results show good correlations with observed data, but the investigation of shifting land uses reflects only poor changes in the flood extension.
Identification and model based assessment of the potential water retention caused by land-use changes
Authors: Wahren A. , Schwärzel K. , Feger K. H. , Münch A. , Dittrich I.
Published: April 2010

Abstract. The extreme summer flood in the Elbe River watershed initiated a debate on the role of forest conversion and afforestation as measures for preventive flood protection. To quantify the effect of forest conversion and afforestation on flood runoff from catchments reliable model calculations are essential. The article overviews the present state of our work and provides an example for a model- based assessment of potential water retention caused by land-use changes in a catchment in the Central Ore Mountains (Saxony, Germany). The potential of flood control by land-use management measures is highly dependant on the site-specific soil and relief conditions and the rainfall event characteristics. The pre-event soil moisture is distinctly lower under forest land-use. Furthermore, infiltration, percolation in the subsoil is increased. These effects exist for small/medium-scale events whereas they become marginal for extreme events.
The rissaga of 15 June 2006 in Ciutadella (Menorca), a meteorological tsunami
Authors: Jansa A. , Monserrat S. , Gomis D.
Published: April 2010

Abstract. An extraordinary "rissaga" event (the local name for high-amplitude sea level oscillations) with 4–5 m of amplitude occurred on 15 June 2006 at Ciutadella (Menorca, Spain). In this paper we describe the rissaga event and propose that the meteorological mechanism responsible for it was an unusual pressure jump, associated with a convective squall line.
Studying the extremes: hydrometeorological investigation of a flood-causing rainstorm over Israel
Authors: Morin E. , Harats N. , Jacoby Y. , Arbel S. , Getker M. , Arazi A. , Grodek T. , Ziv B. , Dayan U.
Published: April 2010

Abstract. Analysis of extreme hydrometeorological events is important for characterizing and better understanding the meteorological conditions that can generate severe rainstorms and the consequent catastrophic flooding. According to several studies (e.g., Alpert et al., 2004; Wittenberg et al., 2007), the occurrence of such extreme events is increasing over the eastern Mediterranean although total rain amounts are generally decreasing. The current study presents an analysis of an extreme event utilizing different methodologies: (a) synoptic maps and high resolution satellite imagery for atmospheric condition analysis; (b) rainfall analysis by rain gauges data; (c) meteorological radar rainfall calibration and analysis; (d) field measurements for estimating maximum peak discharges; and, (e) high resolution aerial photographs together with field surveying for quantifying the geomorphic impacts. The unusual storm occurred over Israel between 30 March and 2 April, 2006. Heavy rainfall produced more than 100 mm in some locations in only few hours and more than 200 mm in the major core area. Extreme rain intensities with recurrence intervals of more than 100 years were found for durations of 1 h and more as well as for the daily rain depth values. In the most severely affected area, Wadi Ara, extreme flash floods caused damages and casualties. Specific peak discharges were as high as 10–30 m³/s/km² for catchments of the size of 1–10 km², values larger than any recorded floods in similar climatic regions in Israel.
High impact weather and cyclones simultaneity in Catalonia
Authors: Campins J. , Aran M. , Genovés A. , Jansà A.
Published: April 2010

Abstract. The Western Mediterranean in general and Catalonia in particular are usually affected by high impact weather (HIW) events, mainly heavy rain (HR) and strong wind (SW). The improvement in the understanding and the accurate forecast of such events are major concerns for the meteorologists of the region. In the present study, HR and SW events in Catalonia are cross-referenced with an objective cyclone database for a 9-year period (from June 1995 to May 2004). Results show that in most of the HR events a cyclone is located close to Catalonia, in such a way that the feeding of a moist flow to the affected region was favoured. These cyclones can be either shallow and weak or deep and intense. A simultaneous cyclone also appears to be connected with many SW events. However, other SW events seem to be related to meso-scale circulations and, as a result, not always well captured in the cyclone database. Finally, coincident HR and SW events are analysed. In almost all of such events a deep cyclone is located in the vicinity of Catalonia.
Heavy rain prediction using deterministic and probabilistic models – the flash flood cases of 11–13 October 2005 in Catalonia (NE Spain)
Authors: Barrera A. , Altava-Ortiz V. , Llasat M. C. , Barnolas M.
Published: April 2010

Abstract. Between the 11 and 13 October 2005 several flash floods were produced along the coast of Catalonia (NE Spain) due to a significant heavy rainfall event. Maximum rainfall achieved values up to 250 mm in 24 h. The total amount recorded during the event in some places was close to 350 mm. Barcelona city was also in the affected area where high rainfall intensities were registered, but just a few small floods occurred, thanks to the efficient urban drainage system of the city. Two forecasting methods have been applied in order to evaluate their capability of prediction regarding extreme events: the deterministic MM5 model and a probabilistic model based on the analogous method. The MM5 simulation allows analysing accurately the main meteorological features with a high spatial resolution (2 km), like the formation of some convergence lines over the region that partially explains the maximum precipitation location during the event. On the other hand, the analogous technique shows a good agreement among highest probability values and real affected areas, although a larger pluviometric rainfall database would be needed to improve the results. The comparison between the observed precipitation and from both QPF (quantitative precipitation forecast) methods shows that the analogous technique tends to underestimate the rainfall values and the MM5 simulation tends to overestimate them.
Regional cosmic ray induced ionization and geomagnetic field changes
Authors: Kovaltsov G. A. , Usoskin I. G.
Published: April 2010

Abstract. Cosmic ray induced ionization (CRII) is an important factor of outer space influences on atmospheric properties. Variations of CRII are caused by two different processes – solar activity variations, which modulate the cosmic ray flux in interplanetary space, and changes of the geomagnetic field, which affects the cosmic ray access to Earth. Migration of the geomagnetic dipole axis may greatly alter CRII in some regions on a time scale of centuries and longer. Here we present a study of CRII regional effects of the geomagnetic field changes during the last millennium for two regions: Europe and the Far East. We show that regional effects of the migration of the geomagnetic dipole axis may overcome global changes due to solar activity variations.
Near-source observations and modeling of the Kuril Islands tsunamis of 15 November 2006 and 13 January 2007
Authors: Rabinovich A. B. , Lobkovsky L. I. , Fine I. V. , Thomson R. E. , Ivelskaya T. N. , Kulikov E. A.
Published: April 2010

Abstract. Two major earthquakes near the Central Kuril Islands (Mw=8.3 on 15 November 2006 and Mw=8.1 on 13 January 2007) generated trans-oceanic tsunamis recorded over the entire Pacific Ocean. The strongest oscillations, exceeding several meters, occurred near the source region of the Kuril Islands. Tide gauge records for both tsunamis have been thoroughly examined and numerical models of the events have been constructed. The models of the 2006 and 2007 events include two important advancements in the simulation of seismically generated tsunamis: (a) the use of the finite failure source models by Ji (2006, 2007) which provide more detailed information than conventional models on spatial displacements in the source areas and which avoid uncertainties in source extent; and (b) the use of the three-dimensional Laplace equation to reconstruct the initial tsunami sea surface elevation (avoiding the usual shallow-water approximation). The close agreement of our simulated results with the observed tsunami waveforms at the open-ocean DART stations support the validity of this approach. Observational and model findings reveal that energy fluxes of the tsunami waves from the source areas were mainly directed southeastward toward the Hawaiian Islands, with relatively little energy propagation into the Sea of Okhotsk. A marked feature of both tsunamis was their high-frequency content, with typical wave periods ranging from 2–3 to 15–20 min. Despite certain similarities, the two tsunamis were essentially different and had opposite polarity: the leading wave of the November 2006 trans-oceanic tsunami was positive, while that for the January 2007 trans-oceanic tsunami was negative. Numerical modeling of both tsunamis indicates that, due to differences in their seismic source properties, the 2006 tsunami was more wide-spread but less focused than the 2007 tsunami.
South American perspective of the International Charter "Space and Major Disasters"
Authors: Mahmood A. , Cubero-Castan E. , Platzeck G. , Bequignon J.
Published: April 2010

Abstract. The International Charter "Space and Major Disasters" is about joint operations and tasking of imaging satellites and other space resources of the member space agencies and operators in the delivery of information products to assist in responding to disasters of natural and technological causes. Authorized Users, who are the civil protection, emergency response or similar organizations of a state that is member of the Charter, can request the data and products. A specialist, called the Project Manager (PM), manages the overall data acquisition and delivery process. Regional initiatives, as for the Latin American countries, are under way to involve PMs from non-member states to have access to satellite data and apply these to disaster coverage in their respective regions. Volcanic eruptions are typical examples of disasters that affect the Latin American countries. A few Charter activations on this disaster type are described to highlight the information products provided under the Charter.