Cloud water chemistry in Sequoia National Park

Abstract

Interception of cloudwater by forests in the Sierra Nevada Mountains may contribute significantly to acidic deposition in the region. Cloudwater sampled in Sequoia National Park had pH values ranging from 4.4 to 5.7. The advance of cold fronts into the Park appears to lead to higher aerosol and gas phase concentrations than are seen under normal mountain-valley circulations, producing higher cloud-water concentrations than might otherwise be expected. Estimates of annual deposition rates of NO₃⁻, SO₄²⁻, NH₄⁺ and H⁺ due to cloudwater impaction are comparable to those measured in precipitation.