Atmospheric Boundary Layer Activities in ESRL Wayne M. Angevine With help from: the Surface and PBL theme team Sara Tucker Bob Banta Ola Persson Jim Wilczak Chris Fairall Atmospheric Boundary Layer Diurnal Variation (a severe simplification) 2000 Inversion 1500 ) s r e t e m Convective ( Mixed Layer t 1000 Residual Layer Residual Layer h g i e H 500 SSttaabbllee ((nnooccttuurrnnaall)) LLaayyeerr 0 Sunrise Noon Sunset Sunrise Adapted from Introduction to Boundary Layer Meteorology -R.B. Stull, 1988 Coastal Boundary Layer - warm to cold (cid:190) One of many 2000 “other” types of boundaInvreyrs ion 1500 ) layers s r e t (cid:190)e Polar BLs are m Convective ( Mixed Layer t s10t0a0bleRe sfidoural Lloaynerg Intermediate h g Layer i periods e H (cid:190) Some oceanic 500 BLs are continuously StableS mtaabrlien (en booctuunrdnaarl)y Llaayyeerr 0 weakly convective Sunrise Why do we care about the boundary layer? (cid:190) Controls transport of pollutants and climate-forcing constituents (cid:190) Source of heat, water, and turbulence (cid:190) Vital for weather and climate prediction (cid:190) Location of aerosols, clouds, and pollutants (cid:190) Context for other measurements Almost any measurement or prediction involves the boundary layer Critical scientific gaps Grand challenges (cid:190) Cloud formation and transitions within the boundary layer (cid:190) Concentration and transport of pollutants in realistically variable boundary layer structures (cid:190) Factors affecting the vertical transport of heat and matter during the boundary layer daily cycle (cid:190) Partitioning of various causes of climate changes in the polar regions (cid:190) Interaction between the boundary layer and atmosphere above (free troposphere) Recent findings (cid:190) Cloud formation and transitions within the boundary layer • Cloud effects on pollutant concentration and transport • Aerosol effects on clouds (cid:190) Conce ntration and transport of pollutants in realistically variable bounda ry layer structures • Stable boundary layer characterization • Mixing depths over water (cid:190) Factor s affecting the vertical transport of heat and matter during the bounda ry layer daily cycle • Coastal pollutant transport • Parameterizations for mesoscale models – validation and development • Au tomated BL height detection (cid:190) Partitio ning of various causes of climate chang es in the polar regions • Arctic boundary layer characterization (cid:190) Interaction between the boundary layer and atmosphere above (free troposp here) • Transitional boundary layers • BL-top entrainment • Lin ks to larger scales Mixing depths over the Gulf of Mexico and Galveston Bay (cid:190) Measurements from High Resolution Doppler Lidar on the Ronald H. Brown (cid:190) Reliability enhanced by multiple parameters • aerosol backscatter • turbulence intensity • win d shear (cid:190) Key fin ding: BL over water is weakly convective • shallow but not very shallow • no diurnal cycle (cid:190) Backed up by sea surface flux and tem perature measurements (cid:190) Key to interpretation of in-situ chemistry and aerosol measurements Validation of diurnal cycle in forecast models (cid:190) Using BL heights derived by an automated algorithm for 5 radar wind profilers in Texas (cid:190) Average over 52 days Stable boundary layer structure (cid:190)Two types lead to different chemical and physical behavior Weak LLJ Stronger LLJ (cid:190)Closely tied to strength of low-level jet: Weak LLJ (< 3 m s-1) - O → 0 3 6-7 m s-1 or more - [O ] stays > 20 ppb 3 (cid:190)Similar effects on temperature and water vapor profiles Stable boundary layer structure (cid:190) Decoupling of flow aloft from surface friction (cid:198) acceleration after sunset (cid:190) Happens every night to some degree (cid:190) Doppler lidar provides highly resolved wind and turbulence information (cid:190) A challenge to model parameterizations, and a framework for improving them