Long-Term Vertical Velocity Statistics Derived From SGP Doppler Lidar Data During Convective Conditions
Poster PDF
Authors
Larry Berg — Pacific Northwest National Laboratory
Rob K Newsom — Pacific Northwest National Laboratory
David D. Turner — NOAA- Global Systems Laboratory
Category
Boundary layer structure, including land-atmosphere interactions and turbulence
Description
One year of Coherent Doppler Lidar (CDL) data collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) SGP site in Oklahoma is analyzed to provide profiles of vertical velocity variance, skewness, and kurtosis for cloud-free convective boundary layers. The variance was normalized by the Deardorff convective velocity scale, which was successful when the boundary-layer depth was stationary, but failed in transition periods. In this study the data are sorted according to time of day, season, wind direction, surface shear stress, degree of instability, and wind shear across the boundary-layer top. The normalized variance was found to have its peak value near a normalized height of 0.25. The magnitude of the variance changes with season, shear stress, and degree of instability, but was not impacted by wind shear across the boundary-layer top. The skewness was largest in the top half of the boundary layer (with the exception of wintertime conditions). The skewness was found to be a function of the season, shear stress, and wind shear across the boundary-layer top, with larger amounts of shear leading to smaller values. Like skewness, the vertical profile of kurtosis followed a consistent pattern, with peak values near the boundary-layer top (also with the exception of wintertime data). The altitude of the peak values of kurtosis was found to be lower when there was a large amount of wind shear at the boundary-layer top.
