A one‐dimensional modeling study of carbonaceous haze effects on the springtime Arctic environment

Abstract

A one‐dimensional three‐component numerical model of the Arctic environment is developed to study the effect of Arctic haze on the surface energy balance. The model represents an improvement over earlier studies in that it accounts for the transfer of infrared as well as solar radiation through the atmosphere, turbulent mixing within the boundary layer, and heat conduction through snow‐capped sea ice. In a control simulation, the model is used to calculate the steady state response of the springtime ocean‐ice‐atmosphere system to the presence of an airborne carbonaceous aerosol with an idealized (but realistic) vertical distribution representative of spring. Additional simulations are then carried out to examine the sensitivity of the response to humidity and surface albedo. In general, the results indicate that surface temperatures increase when haze is present, provided the relative humidity through the column does not change. Except in our control simulation, the increase is due to an increase in the absorbed radiation at the surface. This result is consistent with previous studies which indicated that the increased infrared emission to the surface would more than compensate for the haze‐induced reduction in solar radiation at the surface. As in previous studies, the increase in infrared emission is due to the increase in atmospheric temperatures because of the absorption of solar radiation by the haze, and the increase in atmospheric emissivity because of the greater amount of atmospheric water vapor. The latter follows from the assumption that the relative humidity does not change. However, in the present study the change in the net radiation at the surface is small such that the magnitude of surface warming is also small (several degrees Kelvin or less). Indeed, in the control simulation the absorbed radiation at the surface decreases and the warming is actually brought about by an increase in the sensible heat flux. Furthermore, if the specific humidity rather than relative humidity is assumed constant, then surface temperatures decrease rather than increase. These results suggest that haze‐induced surface temperature changes in the Arctic are difficult to determine, both in sign and magnitude, and that the Arctic environment is less sensitive than previously assumed.