A065-0014
The Seasonal and Diurnal Variations of Planetary Boundary Layer and Convective Mixing Layer at the ARM/SGP sight Based on Raman and Doppler Lidar Measurements
Wednesday, 9 December 2020
Poster
Yufei Chu1, Zhien Wang2, Hyeyum Hailey Shin3, Lulin Xue4, Weiwei Li4 and Grant Firl3, (1)University of Colorado Boulder, Boulder, CO, United States, (2)University of Colorado at Boulder, Boulder, CO, United States, (3)National Center for Atmospheric Research, Boulder, CO, United States, (4)National Center for Atmospheric Research, Developmental Testbed Center, Boulder, CO, United States
Abstract:
The Planetary Boundary Layer (PBL) structure and processes are still poorly observed and understood, especially at the seasonal scale.
Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) supersite offers continuous Raman lidar and Doppler lidar observations, which provide unique dataset to study PBL structure and processes. Although the gradient of aerosol vertical distributions was widely used to derive PBL height, aerosol vertical structures over the land cannot provide an accurate boundary layer height all the time (Luo et al. 2014).
We take advantage of ARM Raman lidar water vapor measurements to improve PBL height determinations using a new dynamic threshold method.
Doppler lidar vertical velocity measurements are used to identify the mixing layer top height. To minimize
gravity wave impact on variance estimations, we developed a hybrid approach for reliable mixing layer height determinations.
The synergy of PBL height and daytime convective mixing layer heights allow us to characterize diurnal PBL evolution over the land, form initial daytime convective mixing layer developing in the morning to nighttime residual layer and near surface layer inversion developments. As solar radiation is one of the main forces of PBL development, PBL diurnal variations depend on seasons. We analyzed four years (2016-2019) warm seasons ARM observations at the SGP site to quantify seasonal and diurnal PBL variations. Although weekly means of diurnal PBL structures display expected seasonal variation, there are significant daily variations in PBL evolutions. We are exploring different dynamic and thermodynamic factors controlling observed daily variations. These results will provide essential guidance to improve model PBL parameterizations.
Reference
Luo T., R. Yuan and Z. Wang, 2014: Lidar Based Remote Sensing of Atmospheric Boundary Layer Height Over Land and Ocean. Atmospheric Measurement Techniques, 7, 173–182.
Stull R.B., 1988: An introduction to boundary layer meteorology. Kluwer Academic Publishers.
