Observations in the nocturnal boundary layer

Low-latitude observations of the stably-stratified planetary boundary layer (SBL) above rough terrain are compared to observations of the mid-latitude SBL mainly through the depth h and its dependence upon surface fluxes. This involves the quantity h/L and the similarity prediction h = (u _* L/f)^1/2.Mid-latitude observations are consistent with model calculations for nighttime-averaged quantities and their deviations, as functions of latitude and surface roughness, from the equilibrium values found at large t. The above applies to horizontally-homogeneous terrain.Low-latitude observations of % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGafq4SdCMbae% baaaa!37AB!\\bar \gamma \] and h/L are significantly smaller than mid-latitude values, apparently the result of katabatic flows at the site and not the differences in latitude. This is consistent with model calculations for non-zero slope terrain.The National Center for Atmospheric Research is sponsored by the National Science Foundation.