An experimental investigation of Arctic haze at Alert,N.W.T., March 1985

Abstract

Arctic haze has been attributed to industrial pollution released at mid‐latitudes. Our current understanding has been pieced together from routine meteorological data, ground‐based air chemistry observations and limited aircraft measurements. This study investigates the relationship between synoptic boundary‐layer meteorology and the composition of the near‐surface atmosphere during the polar sunrise at Alert, N.W.T. A secondary objective is to characterize the influence of local activity on the atmospheric composition at a site for a new baseline monitoring station and at a location where aerosol chemistry and grab‐flask samples for CO₂ have been made for many years. Detailed measurements of the vertical distribution of aerosols were obtained from an upward‐looking lidar to complement the ground‐based measurements. Meteorological profiles of the near‐surface boundary layer were obtained from both free‐flying and tethered balloons. Near‐surface measurements were made of aerosol physical and chemical properties, O₃, NO₂, NO/NO_x, Peroxyacetylnitrate (PAN) and hydrocarbons.

The study period was characterized by prolonged periods with strong surface inversions, which were broken up occasionally by intrusions of cold air into the warmer air aloft. Lidar observations showed that ice crystals often accompanied aerosols and were responsible for reducing visibility below 30–40 km. There was a strong correlation between aerosol mass in the diameter size range 0.15 to 1.5 μm and total SO₄ ⁼ . PAN found at concentrations of about 200 ppt(v) was the main carrier of atmospheric nitrogen. Aerosol trace elements were divisible into anthropogenic soil, mixed soil/anthropogenic sea salt and halogens. Vertical transport in the surface boundary layer, as regulated by the strength of the surface radiation inversion, may play an important role in influencing the chemical composition of the air at the ground. The location of the new baseline monitoring laboratory was found to be generally windier and warmer than the lower altitude weather station, and the influence of local activity was found to be minimal.     

Temperature trends through urbanization in Metropolitan Washington,D.C., 1945–1979

Summary Annual and seasonal changes of the urban heat island magnitude in Washington, D.C. and a close-in suburb were analyzed for the period of 1945 through 1979. Monthly and annual mean temperature data, corrected for elevation, from three stations (National Airport, D.C.—downtown, Silver Spring, MD—suburban, and Beltsville, MD—rural) were evaluated by testing the statistical significance of temperature differences between the different data sets.The analysis indicated that the absolute heat island magnitudes have increased at the rate of 0.020 and 0.019 C/yr at Washington National Airport and Silver Spring, respectively during the study period. The differences between these two rates were not statistically significant at the 0.95 confidence level. However, the increase of the heat island magnitude from 1945 to 1979 at the suburban station was 20% greater than that at the downtown station. Those results indicate that as urbanization progresses, the suburban site, Silver Spring, has become incorporated into the Washington, D.C. urban heat island. The data also indicate that the magnitude of the heat island near the city center has continued to increase despite a significant population decrease since 1950.With 5 Figures