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Climatology of Air Pollution in Kathmandu Valley, Nepal

Climatology of Air Pollution in Kathmandu Valley, NepalClimatology of Air Pollution in Kathmandu Valley, Nepal
[.pdf, 1645.3Kb]

A Thesis Submitted in Partial Fulfillment of the Requirements for the Master of Science Degree, Environmental Science Program in the Graduate School, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA by Sumit Pokhrel, May 2002


Air pollution is a serious problem in Kathmandu, Nepal. Particulate matter concentrations often exceed threshold values at which human health is severely affected. Meteorological factors are known to influence the air pollution level in Kathmandu Valley. This study addresses the linkages between meteorological processes and air pollution in the lower atmosphere of the Kathmandu Valley.

Particulate matter with aerodynamic size less than 10 microns (PM10) was monitored for 76 days, and subsequent information of weather conditions (wind speed and direction, precipitation and temperature) was also collected in situ. The data were then classified according to the United States Environmental Protection Agency (USEPA) Air Quality Index (AQI). Seasonal, weekly and daily variations of PM10 concentrations were also analyzed. It was found that although air pollution is caused by different vehicular and non-vehicular sources, concentration levels in Kathmandu are also influenced by meteorological factors. These factors include atmospheric stability, wind speed and direction, and precipitation.

The physical setting of Kathmandu also influences air pollution concentrations. In this study it was found that the mountain-valley setting produces mountain valley circulations that influence air pollution transport especially in winter. During the winter, air pollution is carried out of Kathmandu Valley during the day, while a mountain breeze causes pollution to return to the valley at night. This causes an elevated level of pollution during the night (19:00/20:00 to 24:00 LST). Since the variation in PM10 concentration is influenced by different meteorological factors in addition to sources, a forecast model for PM10 based on meteorological factors is both recommended and possible for the Kathmandu Valley.

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Pokhrel, Sumit
Southern Illinois University Edwardsville, USA

Secretariat: The World Bank & Asian Development Bank