Ground‐based measurements and dual‐Doppler analysis of 3‐D wind fields and atmospheric circulations induced by a meso‐<i>γ</i>‐scale inland lake

Abstract

This paper presents a high‐resolution dual‐Doppler analysis of lake breeze mesoscale circulation induced by an elongated reservoir with a mean width of ∼2 km and an area of 125 km 2 . Compared to previous meso‐ γ ‐scale lake breeze studies based on point measurements or aircraft observations, the present study provides both a unique quantification and a high‐resolution spatial and temporal 3‐D visualization (several hundred meters and 5 min, respectively) of the kinematic structure of the lake breeze initiation and evolution. Visible satellite images show a cloud‐free zone over the lake and adjacent land areas that was promoted by subsidence associated with the lake breeze circulation. The background synoptic‐scale wind flow was almost parallel to the major axis of the lake, and distinct lake breeze frontal zones formed along both shorelines spanning the length of the lake. Dual‐Doppler analyses showed updrafts in the frontal zones, perturbation horizontal velocities of 1.5 m s −1 on both sides of the lake, and maximum downdrafts of 2 m s −1 centered over the lake. Vertical vorticity in the boundary layer was produced by differential friction between the smooth lake and adjacent land. The circulations are robust and are maintained during the day against a minor change in background wind direction. The study shows that the circulations produced by a small lake can generate significant mesoscale circulations that influence local climatology and identifies the importance of including such small mesoscale processes in global forecast models.