ABC Nepal  South Asia is one of the most populated regions in the world with population densities of 100-500 persons km2, it is also experiencing the most rapid development and increasing demands for energy and mobility, industrial activities and vehicular traffic.
This leads to a growth of anthropogenic pollutant emissions, as pointed out in recent studies of the United Nations Environment Program (UNEP). These emissions increase the concentrations of aerosol, greenhouse gases and ozone precursors, promoting intense photochemical smog episodes and leading to the occurrence of the so-called Atmospheric Brown Clouds, particularly during the dry months . Studies concerning the Atmospheric Brown Clouds have shown that this polluted hazes blocks up to 15% of the sun's radiation causing a possible cooling of the ground and a heating of the atmosphere, which can affect monsoons and other rainfall patterns with negative consequences on the agriculture productivity. In particular, black carbon (BC) can impact on glacier’s life while ozone can damage cellular leaves in the forest ecosystem also favouring decreased carbon storage. Mountain areas are suitable sites for determining the “health conditions” of the atmosphere and where early detection of climate change is particularly effective. Thus, in these areas, continuous observations of atmospheric composition represent a fundamental aspect to well evaluate the impact of the human activities on the environment. In particular the Himalaya-Karakorum is an ideal site to study the vertical extension of the pollution over South Asia and its transport to Himalayan glaciers through the deep mountain valleys. Nevertheless, due to technical and logistic difficulties to carry out continuous measurements at high altitude, no systematic observations of atmospheric constituents were available in this area still now.
These reasons encourage Ev-K2-CNR to pursue the idea of creating a network of stations, in the framework of SHARE project, for studying climate and atmosphere. The first step of this action led to the installation, in collaboration with UNEP, of a remote monitoring station (the Nepal Climate Observatory - Pyramid) in the high South Himalayas.
Description The Nepal Climate Observatory - Pyramid (Nepal, 27.95N, 86.82E, 5079 m a.s.l.) has been installed in February 2006 in the high Khumbu Valley, above the timber line in a rocky and mossy environment not far from the base camp area of Mt. Everest. The Observatory is running in the framework of the Atmospheric Brown Clouds Project (ABC) of UNEP, and is part of AERONET network and WMO-GAW program. Since 2010 NCO-P is a global GAW station. The instrument set-up was defined in accordance with “ABC” Project standards (Ramanathan et al., 2006) and includes: (a) a surface ozone analyser, (b) a Multi-Angle Absorption Photometer which measures aerosol light absorption also allowing the determination of the BC concentration in atmosphere, (c) a Differential/Scanning Mobility Particle Sizer to determine the aerosol size distribution from 10 to 500 nm, (d) an optical particle counter to complete the aerosol size distribution till 32 µm also allowing to reconstruction of aerosol mass, (e) a three wavelength integrating nephelometer to determine aerosol total and back scattering coefficients, (f) a sun photometer for measuring the aerosol optical depth, (g) a high volume aerosol sampler for chemical analyses, (h) a “clean” sampling device to collect grab air samples for halocarbons analyses, (i) a pyranometer for measuring the global solar irradiance, (j) a pirgeometer for measuring the downwelling infra-red irradiance, (k) a meteorological unit measuring temperature, pressure, relative humidity, rain, wind intensity and direction. The power needed to carry out the experimental activity (~ 3 kW) is provided by 96 photovoltaic panels with 120 electric storage cells. A satellite connection makes remote control of the devices and instrumentation possible so that operating instruments can be directly accessed from ISAC-CNR (Bologna, Italy) Headquarter. Quality control for instrumentation and data are continuously performed according to GAW-WMO, AERONET, EUSAAR, AGAGE and CEOP procedures.
A second station of the SHARE network will be installed in Pakistan. Preliminary studies are currently ongoing in order to identify the most representative area in the Gilgiit-Baltistan Region.
State of the art Besides proving an accurate description of the atmospheric background conditions over South Himalayas, the observations carried out at NCO-P since 2006 revealed that Brown Cloud “hot spots” can influence the high Himalayas during the pre-monsoon, with very high levels of BC, ozone, fine and coarse particles, and scattering coefficient. 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. As deduced by NCO-P research activity, in average, about 20% of the year is characterized by synoptic transport events of mineral dust and that more than 50% coming from Tibetan Plateau and Lot and Tar Deserts. The presence of absorbing aerosol can locally induce an additional top of the atmosphere forcing of 10 to 20 Wm−2 for the first atmospheric layer inducing a substantial decrease of the amount of radiation reaching the surface. In spite of being located at the heart of a very remote area, the NCO-P is affected by advection of significant constituents of the Brown Cloud: BC, dust particles and ozone from the regions of southern Asia and the Indo-Gangetic plains, able to influence climate and the atmospheric radiative forcing. Similar studies are foreseen in the Karakorum - Pakistan Gilgit-Baltistan where two AWSs were installed on the Baltoro glacier in order to provide further information on the atmospheric characteristics of this region.
Aims The main aims of SHARE-ABC Pilot Project can be summarized in 6 points:
- To characterize chemical, physical and optical properties of aerosol in Himalaya and Karakorum and study of related climatic impacts;
- To study the influence of ABC on atmospheric composition in the Himalaya and Karakorum.
- To study the influence of natural processes, such as mineral dust transport and stratospheric intrusions, on atmospheric composition in the Himalaya and Karakorum;
- To define the variability of climate-altering and reactive compounds in the Himalayan-Karakorum mountain regions (from the short to the long temporal scales)
- To study the interaction between Himalayan-Karakorum mountain ranges and atmospheric circulation (from the synoptic to the local scales)
- To study deposition processes of the absorbing fraction of aerosol particles and the related changes in snow-ice albedo
- Attaining these aims will allow to study the impacts on climate and atmosphere of the natural and anthropogenic phenomena at different time and space scales (global and regional), providing precious information in a very little known area. This information will be available for scientific community and for policy makers, in order to define strategies for mitigations and adaptations to climate change.
Program Future activities within SHARE-ABC pilot project are related to the prosecution of atmospheric composition and meteorological observations in Himalaya, in order to study the long term background conditions as well as vertical air mass exchange (e.g. stratospheric intrusions). Evaluation of changes in intensity / frequency of pollution and mineral dust transports will permit to estimate the trend of atmospheric radiative forcing. Furthermore, the interaction between local valley circulation and synoptic circulation will be investigated in order to better assess the influence of biomass burning and mineral dust on atmospheric composition and optical active aerosol at NCO-P. One of the future goals is to define an objective methodology to differentiate background and polluted air masses.
The implementation of experimental set up is linked to the feasibility of an extension of the renewable power supply. We planned implementation of solar radiation observation with the ultraviolet radiation and CO measurements, in order to provide information on combustion sources and air mass aging. Moreover samplings of snow for determination of BC concentrations have been started, with the aim to study the impact of BC deposition on snow albedo at the Changri Nup glacier in the Khumbu valley.
Themes Principal themes of the studies carried out in the ABC-Nepal Pilot projects are:
- Investigation of the transport to high altitudes through the Himalayan valley of Atmospheric Brown Cloud and its vertical extension.
- Study of background variability of climate-altering and reactive compounds in the South Himalayas.
- Investigation of the role of air-mass transport to the variability of ozone and other trace gases in the Himalayan free troposphere.
- Study of mineral dust transport to South Himalayas: identification of main source areas and climate impacts.
- Study of the radiative forcing of absorbing aerosols at high altitudes and their interaction with monsoon circulation.
- Study of the deposition of absorbing particles on snow and ice surfaces and evaluation of the related impact on melting enhancement.
Targets
- To determine the temporal trends of trace gases and climate altering gases (O3, HCFC, HFC, CFC, ...);
- To determine the temporal trends of several aerosol parameters (black carbon, PM10, PM2.5, PM1.0, size distribution, scattering and absorption coefficients);
- To identify contributions of stratospheric air-mass intrusions to the surface ozone concentration;
- To identify mineral dust transport from North Africa, Arabian Peninsula and Central Asia, evaluate the mass contribution to PM10, their chemical composition and physico-chemical properties;
- To identify the contribution of polluted air mass transport (local, regional, long range) to the concentration of gaseous and particle atmospheric compounds;
- To identify the measurement periods characterised by background conditions at NCO-P;
- To evaluate the radiative forcing variation linked to transport of air masses rich in natural or anthropogenic aerosol
- To evaluate the relationship between atmospheric and snow/ice concentrations of absorbing aerosol in the high Khumbu valley.
Partners
- CNR-ISAC (Paolo Bonasoni, Paolo Cristofanelli, Angela Marinoni, Rocco Duchi, Ubaldo Bonafé, Francescopiero Calzolari, Fabrizio Roccato, Sandro Fuzzi, Cristina Facchini, Stefano Decesari, Gian Paolo Gobbi, Federico Angelini)
- CNRS-LGGE (Paolo Laj, Paolo Villani, Olivier Laurent)
- Urbino University (Michela Maione, Jgor Arduini)
- CNRS-LaMP (Karine Sellegri, Hervé Venzac, Jean-Marc Pichon)
- ENEA (Giorgio Di Sarra, Claudia Di Biagio)
- NASA Goddard (Teppei Yasunari, William Lau)
- ETHZ (Michael Sprenger)
- ICIMOD (Bidya Banmali Pradhan, Pradeed Dangol )
- NAST
Publications For more information on the NCO-P station, please visit the following website:
http://evk2.isac.cnr.it/
|
|
