A monitoring programme for halogenated climate-altering gases has been established in the frame of the SHARE EV-K2 -CNR project at the Nepal Climate Laboratory – Pyramid in the Himalayan range at the altitude of 5079 m a.s.l. The site is very well located to provide important insights on changes in atmospheric composition in a region that is of great significance for emissions of both anthropogenic and biogenic halogenated compounds. Measurements are performed since March 2006, with grab samples collected on a weekly basis. The first three years of data have been analysed. After the identification of the atmospheric background values for fourteen halocarbons, the frequency of occurrence of pollution events have been compared with the same kind of analysis for data collected at other global background stations. The analysis showed the fully halogenated species, whose production and consumption are regulated under the Montreal Protocol, show a significant occurrence of “above the baseline” values, as a consequence of their current use in the developing countries surrounding the region, meanwhile the hydrogenated gases, more recently introduced into the market, show less frequent spikes. Atmospheric concentration trends have been calculated as well, and they showed a fast increase, ranging from 5.7 to 12.6%, of all the hydrogenated species, and a clear decrease of methyl chloroform(-17.7%).The comparison with time series from other stations has also allowed to derive Meridional gradients, which are absent for long living well mixed species, while for the more reactive species, the gradient in creases inversely with respect to their atmospheric lifetime. The effect of long range transport and of local events on the atmospheric composition at the station has been analysed as well, allowing the identification of relevant source regions the Northern half of the Indian sub-continent. Also, at finer spatial scales, a smaller, local contribution of forest fires from the Khumbu valley has been detected.

In the framework of the SusKat (Sustainable Atmosphere for the Kathmandu Valley), ABC-UNEP and NextData Projects, CNR-ISAC and URT Ev-K2-CNR participated in the setting-up of the Kathmandu (Pakanajol) monitoring station. In particular, the station is equipped with: • meteorological sensors; • global pyranometer for downward solar short-wave radiation; • surface ozone analyzer; • optical particle counter for aerosol size distribution from 0.3 to 10 micron; • on-line PM1/PM10 analyser ; • multi-angle absorption photometer for equivalent black carbon mass measurement.

In the framework of the SusKat (Sustainable Atmosphere for the Kathmandu Valley), ABC-UNEP, SHARE and NextData Projects, CNR-ISAC and URT Ev-K2-CNR participated in the setting-up of the Kathmandu (Pakanajol) monitoring station. In particular, the station is equipped with: • meteorological sensors; • global pyranometer for downward solar short-wave radiation; • surface ozone analyzer; • optical particle counter for aerosol size distribution from 0.3 to 10 micron; • on-line PM1/PM10 analyser ; • multi-angle absorption photometer for equivalent black carbon mass measurement.

The Portable Aethalometer Model AE42 manufactered by Magee measures light absorption by suspended aerosol particles at two wavelengths: 880 nm (IR), quantitative for the mass of ‘Black’ Carbon; and 370 nm (UV), indicating aromatic organic compounds. The instrument’s analytical performance is identical to the Rack Mount Aethalometer Model AE22, but it is constructed in a small portable case with an internal battery providing several hours of mobile operation. The Portable Aethalometer can also be operated from an AC transformer or by cables from an external battery or automobile power outlet. This instrument is widely used for studying indoor air quality, and for the mobile mapping of the air quality impacts of localized sources. The Portable Aethalometer may also be supplied with 7 wavelength light sources upon request.

In the framework of the SusKat (Sustainable Atmosphere for the Kathmandu Valley), ABC-UNEP and NextData Projects, CNR-ISAC and URT Ev-K2-CNR participated in the setting-up of the Kathmandu (Pakanajol) monitoring station. In particular, the station is equipped with: • meteorological sensors; • global pyranometer for downward solar short-wave radiation; • surface ozone analyzer; • optical particle counter for aerosol size distribution from 0.3 to 10 micron; • on-line PM1/PM10 analyser ; • multi-angle absorption photometer for equivalent black carbon mass measurement.

In the framework of the SusKat (Sustainable Atmosphere for the Kathmandu Valley), ABC-UNEP and NextData Projects, CNR-ISAC and URT Ev-K2-CNR participated in the setting-up of the Kathmandu (Pakanajol) monitoring station. In particular, the station is equipped with: • meteorological sensors; • global pyranometer for downward solar short-wave radiation; • surface ozone analyzer; • optical particle counter for aerosol size distribution from 0.3 to 10 micron; • on-line PM1/PM10 analyser ; • multi-angle absorption photometer for equivalent black carbon mass measurement.

The OPC, manifactured by FAI, permit a - Characterization of the temporal trends of the particulate matter granulometric distribution as a support and integration to information about air quality - Real-time estimation of the PM1, PM2.5, PM10, TPS mass concentration of the airborne particulate matter. Main features - Measurement principle: laser scattering on elliptical mirror - Optical channels: 8 optical channels with thresholds having lower limits [µm]: 0.28, 0.4, 0.5, 0.7, 1.1, 2.0, 3.0, 5.0 - Sampling type: The instrument gives counts per minute, or counts per liter for each optical channel - Dimensional sensitivity: 0.28 µm (50 ± 10% count efficiency)

In the framework of the SusKat (Sustainable Atmosphere for the Kathmandu Valley), ABC-UNEP and NextData Projects, CNR-ISAC and URT Ev-K2-CNR participated in the setting-up of the Kathmandu (Pakanajol) monitoring station. In particular, the station is equipped with: • meteorological sensors; • global pyranometer for downward solar short-wave radiation; • surface ozone analyzer; • optical particle counter for aerosol size distribution from 0.3 to 10 micron; • on-line PM1/PM10 analyser ; • multi-angle absorption photometer for equivalent black carbon mass measurement.

The Model 205 Ozone Monitor makes use of two detection cells to improve precision, baseline stability and response time. In the Dual Beam instrument, UV light intensity measurements Io (ozone-scrubbed air) and I (unscrubbed air) are made simultaneously. Combined with other improvements, this made it possible to reduce the time between ozone measurements to 2 seconds, making our instrument the fastest UV-based ozone monitor on the market, while still retaining the small size, weight and power requirements of our popular Model 202 Ozone Monitor.

This paper provides a detailed description of the atmospheric conditions characterizing the high Himalayas, thanks to continuous observations begun in March 2006 at the Nepal Climate Observatory-Pyramid (NCO-P) located at 5079 m a.s.l. on the southern foothills of Mt. Everest, in the framework of ABC UNEP and SHARE-Ev-K2-CNR projects. The work presents a characterization of meteorological conditions and air-mass circulation at NCO-P during the first two years of activity.The mean values of atmospheric pressure, temperature and wind speed recorded at the site were: 551 hPa, -3.0°C, 4.7 m s -1 ,respectively. The highest seasonal values of temperature (1.7 ° C) and relative humidity (94%) were registered during the monsoon season, which was also characterized by thick clouds, present in about 80% of the afternoon hours, and by a frequency of cloud-free sky of less than 10%. The lowest temperature and relative humidity seasonal values were registered during winter, -6.3° C and 22%, respectively, the season being characterised by mainly cloud-free sky conditions and rarehick clouds. The summer monsoon influenced rain precipitation (seasonal mean: 237 mm), while wind was dominated by flows from the bottom of the valley (S-SW) and upper mountain (N-NE). The atmospheric composition at NCO-P has been studied thanks to measurements of black carbon (BC), aerosol scattering coefficient, PM1, coarse particles and ozone.The annual behaviour of the measured parameters shows the highest seasonal values during the premonsoon (BC: 316.9 ng m-3 , PM1: 3.9 µg m-3, scattering coefficient: 11.9 Mm-1 , coarse particles: 0.37 cm-3 and O3: 60.9 ppbv), while the lowest concentrations occurred during the monsoon (BC: 49.6 ng m-3 , PM1: 0.6 µg m-3 , scattering coefficient: 2.2 Mm-1 , and O3: 38.9 ppbv) and, for coarse particles, during the post-monsoon (0.07 cm-3 ). At NCO-P, the synoptic-scale circulation regimes present three principal contributions: Westerly, South-Westerly and Regional, as shown by the analysis of in-situ meteorological parameters and 5-day LAGRANTO back-trajectories. The influence of the brown cloud (AOD>0.4) extending over Indo–Gangetic Plains up to the Himalayan foothills has been evaluated by analysing the in-situ concentrations of the ABC constituents. This analysis revealed that brown cloud hot spots mainly influence the South Himalayas during the pre-monsoon, in the presence of very high levels of atmospheric compounds (BC: 1974.1 ng m-3 , PM1: 23.5 µg m-3, scattering coefficient: 57.7 Mm-1, coarse particles: 0.64 cm-3, O3: 69.2 ppbv, respectively). During this season 20% of the days were characterised by a strong brown cloud influence during the afternoon, leading to a 5-fold increased in the BC and PM1 values, in comparison with seasonal means. Our investigations provide clear evidence that, especially during the pre-monsoon, the southern side of the high Himalayan valleys represent a “direct channel” able to transport brown cloud pollutants up to 5000 m a.s.l., where the pristine atmospheric composition can be strongly influenced.