Validation of a simple diagnostic relationship for downslope flows. (2nd March 2020)

• Record Type: Journal Article
• Authors: Cuxart, Joan; Martínez‐Villagrasa, Daniel; Stiperski, Ivana
• Is Part Of: Atmospheric science letters. Volume 21:Number 5(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-02
• Subjects: diagnostic formula -- downslope flow -- katabatic depth -- MATERHORN campaign -- METCRAX II campaign; Atmospheric physics -- Periodicals; 551
• DOI: 10.1002/asl.965
• Languages: English
• ISSNs: 1530-261X

Abstract

Abstract: A simple conceptual view of downslope flows allows a derivation of a diagnostic relationship between the maximum depth of the flow, its speed, the slope angle and the cooling flux. This relationship is obtained considering that the turbulence cooling causing the air to flow downslope is essentially compensated by the warming by compression as the flow reaches higher pressure levels. The obtained relationship is consistent with the bulk heat budget for the along‐slope flows, and its agreement with existing prognostic layer‐averaged models is checked. Finally, the depth of the flow obtained from the diagnostic relationship is compared against the observational estimations of katabatic flows from two experimental campaigns. Abstract : A simple formula for downslope flows is presented and compared to recently obtained experimental data. It relates the wind speed, the slope angle, the surface cooling flux, the depth of the flow, and the background thermal stratification. It is consistent with previous findings based on the bulk heat budget equation for the along‐slope wind. The figure shows the variation of the depth of the downslope flow ( D max ) allowing only one variable to change. The values for the variables when fixed are v = 2 m·s −1, H = −0.01 K·m·s −1, ∂ z θ = 0.0033 K·m −1, and α = 15°.