The vertical distribution of tropospheric aerosols at Barrow, Alaska

The vertical distribution of tropospheric aerosols near Barrow, Alaska (latitude 71°21’ N, longitude 156°30’ W) was determined by measuring the optical atmospheric transmission in the mid-visible at different altitudes with an airborne photometer. Measurements of the vertical aerosol distribution for periods in April and July 1972, are discussed. The aerosol concentration for both periods decreased exponentially with increasing height with a scale height equal to 1.4 ± 0.3 km. A seasonal variation in turbidity (and the corresponding columnar aerosol loading) was found. In general, the spring turbidity values were larger than the mid-summer values, thereby suggesting an aerosol mechanism which operates at low temperatures. It is hypothesized that the aerosols may be ice crystals seeded by open leads and mixed into the troposphere. A minimum value of aerosol optical depth (τ_D = 0.05 ± 0.01) occurred after the passage of a cold front. Possible effects of ice crystal aerosols on the heat budget of the arctic basin are discussed.