Strong Downslope Winds at Boulder, Colorado

Abstract

- statistics of 22 downslope windstorms in {B}oulder - mean windspeeds: 20 m/s, mean maximum gusts: 36 m/s - winds only half as strongover the lee slopes and out in the plains (from a chain of surfacestations) - location of speed maximum is not stationary - generallyno ideal upstream sounding ({WNW}-{NW} upper level winds): used potentialtemperature at surface and 700 and 500 h{P}a maps to find best soundingfrom the three stations {G}rand {J}unction, {L}ander and {S}alt {L}ake{C}ity - mean upwind conditions show inversion (approx. 25 h{P}adeep, nearly isothermal) above mountain top (575 h{P}a); layer aboveinversion more stable than layer near surface - mean downwind sounding({D}enver) also shows this inversion, albeit {BELOW} mountain top(approx. 650 h{P}a); air below is potential warmer than at same heightupstream => blocking of low level air upstream