Special Issue:Sixth Scientific Conference of the International Global Atmospheric Chemistry Project (IGAC) Bologna, Italy; 13–17 September 1999

This work describes the preliminary results of a study aimed at: (1) assessing the ability of a general circulation model routinely run at the Epson Meteo Centre (CEM) in predicting daily rainfall; (2) evaluating the performance of satellite-derived precipitation estimates (namely, NOAA CPC CMORPH) over the same domain and during the same period. The CPC daily rain gauge analysis is used as reference for validation. The study focused on the Indian Monsoon during summer 2004, and comparison with a similar analysis at the mid-latitudes is also shown.

The Ev-K2-CNR Project has been promoting and developing research at high altitude (>2,500 m a.sl.) in the Himalaya and Karakoram since 1987. Recently, activities have been focused on development of a monitoring network (stations at High Altitude for Research on the Environment in Asia: SHARE-Asia) to increase the environmental and geophysical scientific knowledge in these mountain regions. Research and monitoring activity at high altitude require a particular experience and a well-organized network. Ev-K2-CNR has accumulated a significant experience in managing a high altitude network of automatic weather stations along the Khumbu Valley (Nepal) and in northern Pakistan (Baltistan region) in the framework of the Coordinated Enhanced Observing Period Project. With the installation of an Atmospheric Brown Clouds Project (ABC) monitoring station near the Pyramid Laboratory-Observatory in 2006, near the base of Mount Everest, SHARE-Asia can also contribute to the study of atmospheric circulation of pollutants. The “ABC-Pyramid” is the first of a network of stations that are planned to be installed at altitudes between 2,500 and 5,000 m a.s.l. along the Himalayan–Karakoram chain. These stations will be operated under active cooperation with the local scientific community, creating ample cooperation between western countries and developing countries in the region.

Multispectral measurements of direct solar irradiance were simultaneously taken employing various sun-photometers at five stations located at different altitudes along the western slope of the Leo valley, in the Apennines (Italy), on a number of clear-sky autumn days in 1981 and 1982. Using precise estimates of the calibration constants of the various sun-photometers, obtained through a rigorous intercomparison procedure, the measurements were examined following the most up-to-date criteria of the sun-photometry method to determine daily homogeneous sets of aerosol optical depths at three window-wavelengths, at all five stations. The values of aerosol optical depth obtained from the 1982 measurements were corrected for the extinction effects produced by the stratospheric cloud of El Chichón volcanic aerosols, following a procedure based on the multimodal aerosol extinction model proposed by Pueschel et al. (Pueschel, R.F., Kinne, S.A., Russell, P.B., Snetsinger, K.G., 1993. Effects of the 1991 Pinatubo volcanic eruption on the physical and radiative properties of stratospheric aerosols. Keevallik, S. Kärner, O. (Eds.), IRS '92: Current Problems in Atmospheric Radiation. Proceedings of the International Radiation Symposium, A. Deepak Publ., Hampton, Va., 183–186.) for 6-month-old volcanic particles (see Appendix). The results show that the tropospheric aerosol optical depth at 500-nm wavelength usually assumed low values in the early morning, most generally decreasing from 0.08 to 0.01 with the station altitude, and considerably increased during the morning, especially at the lower stations, as a result of the vertical transport of particulate matter due to the upslope breezes. The corresponding daily percentage increases varied between 60% and 370%, presenting a median value of 175% and quartiles of 140% and 230%. The time-variations of the volume aerosol extinction coefficient at the 500-nm wavelength were evaluated within the four atmospheric layers defined by the station altitudes, presenting early morning values mainly varying from 0.02 to 0.20 km(-1) in the first layer, from 0.02 to 0.11 km(-1) in both second and third layers and from 0.01 to 0.03 km(-1) in the fourth. Therefore, greater increases were found to occur within the three lower layers situated below 1500 m height, with hourly mean percentage variations ranging between 10% and 420%, with a median value of 230% and quartiles of 70% and 270%.

The Himalayan-Karakoram range - for its elevation and geographic location, represents one of the ideal places for studying long-range pollutant transport systems on a regional scale and for monitoring changes index by mechanisms that act on global scale through monsoon circulation. This book offers a comprehension of the environmental phenomena

A Cimel sunphotometer operating in the framework of the AERONET project has been installed at the Himalayan Ev-K2-CNR Pyramid (5079 m a.s.l.) in the year 2006, as site Ev-K2-CNR. The observational activity will provide a characterization of the optical and microphysical properties of atmospheric aerosols, in particular of the atmospheric brown cloud (ABC) in the Himalayan region. This paper will describe the Cimel sunphotometer measurement technique, will introduce to the AERONET programme and will evaluate the contribution of the proposed Ev-K2-CNR AERONET site to the study of the ABC.

ROXMAS (ROx Chemical Conversion/CIMS), a novel method for atmospheric speciated measurements of HO2 and the sum of organic peroxy radicals (SRO2) developed by MPI-K, has been successfully deployed in a field campaign on Monte Cimone, Italy, June-July 2000. The method relies on amplifying chemical conversion of peroxy radicals to gaseous sulfuric acid via the chain reaction with NO and SO2 and detection of the sulfuric acid by CIMS. Speciated measurements have been realized by diluting atmospheric air in either N2 or O2 buffer, thus exploiting the dependence of the conversion efficiency of RO2 to HO2 on [O2], [NO], and [SO2]. Speciated measurements of HO2 and RO2 are required to provide further insight into radical partitioning and thus to elucidate further the mechanisms of the oxidation of volatile organic compounds in the troposphere. This methodology yields useful speciated results for atmospheric conditions where CH3O2 makes a major contribution to total RO2. Under other conditions it gives an upper limit for [HO2] and a lower limit for [SRO2].

The ozone situation in the Eastern Alps was investigated during the south foehn period from 4 - 6 May 1997. The event was studied in detail using surface measurements, soundings and aircraft measurements of meteorological and chemical parameters. A numerical simulation with a prognostic meteorological model (MM5) and a chemistry-transport model with 6 km resolution provided additional insight. The case study was supplemented by a climatological evaluation of a three-year data set. The foehn period was preceeded by an ozone episode in the Po Basin south of the Alps. Advection of residual-layer air masses from that area caused a maximum of the ozone concentration in the beginning. Later on, the ozone concentration in the foehn area was determined by a mixture of regional-scale advection from the lower free troposphere and boundary-layer air form the south. The contribution o boundary-layer air was especially strong in the lee of the deep gap formed by the Brenner Pass and visiblein many parameters. The climatological evaluation showed that during south foehn, ozone concentrations are elevated in the foehn area, especially in the valleys and during nighttime where the usual nocturnal minimum is suppressed.

The International Global Atmospheric Chemistry (IGAC) project was created in the late 1980s to address growing international concerns over rapid changes observed in Earth's atmosphere. Much of IGAC's research effort during its first decade was directed towards assessing the effects of anthropogenic emissions on the background atmosphere. While questions remain concerning the point at which observed global/regional mean trends in component concentrations (signal) unambiguously rise above background natural variability (noise), it is now well recognized that human activities have perturbed the chemical composition of the atmosphere at local, regional, and global scales. Two overarching questions have emerged that constitute the basis for the IGAC action plan over the next decade: (1) What is the role of atmospheric chemistry in amplifying or damping climate change? (2) Within the Earth System, what effects do changing regional emissions and depositions, long-range transport, and chemical transformations have on air quality and the chemical composition of the planetary boundary layer? Within the context of the larger ABC-Asia project, a proposal was put forward for the activation of an ABC-IGAC Task focusing on the monitoring of aerosol and trace gases over the Asia–Pacific region and on estimating their impact on atmospheric chemistry and the radiation budget. The activities currently in progress, to include the Ev-K2-CNR Pyramid observatory in the Atmospheric Brown Cloud (ABC) monitoring network under the Stations at High Altitude for Research on the Environment in Asia (SHARE-Asia) project, aim at providing an important contribution to ABC-Asia and, at the same time, will undoubtedly be an opportunity for the Italian community of global-change researchers.

Chlorofluorocarbons and their replacement compounds are anthropogenic compounds of great environmental concern. For this reason monitoring their atmospheric mixing ratios on a worldwide scale is recommended. An analytical methodology for the simultaneous determination of selected chlorofluorocarbons and their replacement compounds has recently been developed. This methodology was applied in the analysis of actual air samples collected in remote and semi-remote areas located in the Northern and Southern Hemispheres. The concentration levels measured in the air samples collected in the two hemispheres are reported.