The wind field around Mauna Loa derived from surface and balloon observations

Abstract

The mountain wind field in the vicinity of Mauna Loa Observatory is derived by comparing vertical profiles of wind, ozone, and water vapor in the free troposphere to measurements made at the observatory. The wind field near the surface is described by two components: a radiation wind caused by the diurnal heating and cooling of the mountain slope, and a barrier wind caused by the free tropospheric wind flowing around the mountain barrier. The radiation wind is the primary factor in transporting air from different source altitudes in the free-troposphere to the observatory at 3400 m. At midday, air typically arrives from near the top of the marine boundary layer at 2500 m. After midnight, the average source altitude is 3400 m. The barrier wind field consists of a windward stagnation point, strong cross-slope and downslope flow in the flanks, and moderate downslope flow in the leeward sectors. The barrier wind field is effective at disrupting the surface temperature inversion and the radiation wind at night. A simple model is presented which relates the average properties and statistical variation of these winds to the vertical transport of air from the free troposphere to the observatory by the mountain wind field.