The Nepal Climate Observatory - Pyramid (NCO-P, 27.95 N, 86.82 E) is located at 5079m a.s.l. in Sagarmatha National Park, in the eastern Nepal Himalaya, near the base camp area of Mt. Everest. NCO-P is sited at the confluence of the secondary Lobuche valley (oriented NNW-SSE) and the main Khumbu valley (oriented NESW), a tributary of the Dudh Koshi valley, a major Ganges tributary. Forests exist only in areas of the valley below 4 km a.s.l., while the landscape around the measurement site is mostly rocky with patches of musk. The area is subject to short-lived snow cover periods, especially during the cold months and summer monsoon. NCO-P is located away from important anthropogenic sources of pollutants, and only small villages are present along the valley: Lobuche, Pheriche, Tyangboche, Namche Bazar (the biggest village with about 800 inhabitants), Phakding and Lukla. The closest major urban area is Kathmandu (1 081 845 inhabitants; 2001 census), situated in the valley of the same name (estimated population of the valley in 2009 was about 3 million). The city, located about 200 km South-West of the measurement site and more than 3.5km lower down, is characterised by high atmospheric pollution and poor air quality.

The Observatory stands at the top of a hill, 200m from the Pyramid International Laboratory, a multidisciplinary high altitude research centre founded by the Ev-K2-CNR Committee and the Nepal Academy of Science and Technology in 1990. NCO-P was set up during January and February 2006, and the observation program was launched at the end of February 2006 in the framework of ABC - UNEP and SAHRE - EvK2CNR projects. At the end of March 2006 a Cimel CE-318 sunphotometer was installed at NCO-P within the framework of the Aerosol Robotic Network, AERONET (http://aeronet.gsfc.nasa.gov, EvK2-CNR site). It provides a characterization of aerosol optical and microphysical properties of the air column above the station.

In 2007 the station was part of GAW-WMO program. In July 2010 the Nepal Climate Observatory - Pyramid was upgraded to GAW Global Station.

The shelter-laboratory is composed of two parts: the main is devoted to host the instrumentation for the scientific activities while the behind part (a third of the shelter) hosts the batteries for power supply. On the aluminium roof four holes for inlet sampling are presents: a PM1 Digitel head for an integrating nephelometer and DMPS/SMPS instruments; a Total Particle Size for the Optical Particle Counters that has a specific head with probe with T and RH sensors; a PM10 for the high volume discontinuous sampling of aerosol on quartz fibre filters; a second Total Particle Size head for ozone and black carbon measurements.

The monitoring activity in the shelter-laboratory is completely realized using renewable energy from 112 photovoltaic panels and this permit to minimize the possible influence of local emissions and guarantee air mass sampling in clean conditions. The energy produced by photovoltaic panels is stocked by 120 electric storage cells, lodged on the shelf in the behind part of the shelter. The inverters will guarantee the current stabilisation.

A dedicated satellite connection permits near-real-time data transfer, as well as the remote control of instrumentation. Computers in the laboratory are connected with the server located in the Pyramid International Laboratory, using a coupled optical fibre and a wireless connection. The server Himalaya server is linked to another server located at ISAC-CNR Institute in Bologna (Italy). Quality control for instrumentation and data reduction will be performed according to EUSAAR/GAW/AGAGE procedures for aerosols and gases.

All the instrumentation is completely autonomous and remotely controlled, however technicians employment is necessary for the off line measurements (aerosol sampling on filters; greenhouse gases sampling in flasks performed far from shelter in order to protected from every local pollution source) and for some maintenance of the instrumentation.

Further details on the measurement site can be found in: P. Bonasoni, P. Laj, A. Marinoni, M. Sprenger, F. Angelini, J. Arduini, U. Bonaf?, F. Calzolari, T. Colombo, S. Decesari, C. Di Biagio, A. G. di Sarra, F. Evangelisti, R. Duchi, MC. Facchini, S. Fuzzi, G. P. Gobbi, M. Maione, A. Panday, F. Roccato, K. Sellegri, H. Venzac, GP. Verza, P. Villani, E. Vuillermoz, and P. Cristofanelli Atmospheric Brown Clouds in the Himalayas: first two years of continuous observations at the Nepal Climate Observatory-Pyramid (5079 m). Atmos. Chem. Phys., 10, 7515-7531, 2010. and in the ACP Special Issue "Atmospheric brown cloud in the Himalayas",