This dissertation describes the most comprehensive study to date of the diurnal cycle of air pollution in the Kathmandu Valley, Nepal -- a bowl-shaped mountain valley of two million people with a growing air pollution problem but little past research. Field measurements and computer simulations were used to study the interplay of emissions and ventilation. From September 2004 through June 2005, CO (carbon monoxide), ozone, PM10 (particles smaller than 10 micrometers), wind speed and direction, solar radiation, temperature, and humidity were continuously measured east of Kathmandu. Sensors towers and mountains measured the diurnal cycle of the vertical temperature structure and stability. A sodar measured the mixed layer height and upper-level winds. Bag sampling provided the diurnal cycle of CO on mountains, passes and around the valley. Winds were measured on a mountain pass and ozone on a mountaintop. Patterns of air pollution and meteorology in the valley showed remarkable day-to-day similarity, with daily twin peaks of CO and PM10, a noon ozone maximum, afternoon westerly winds, and a stagnant cold pool at night. On mountaintops at night, ozone remained high, while CO dropped to regional background levels.
