Structures of the Sea‐Breeze Front in Dual‐Doppler Lidar Observation and Coupled Mesoscale‐to‐LES Modeling

Abstract

Sea‐breeze front (SBF) can cause dramatic changes in weather and air quality near the coast. However, the observation and forecast of its three‐dimensional (3‐D) fine‐scale structures have been challenging. Using mesoscale‐to‐large eddy simulations (LES) models and high‐resolution lidar measurement over Sendai Airport, here we perform a successful simulation of the observed 3‐D structures of an SBF for the first time. We show that frontal structures are characterized by a series of lobes (spaced ~500 m apart) aligned along the raised sea‐breeze head, where the shear between sea breeze and alongshore ambient flow aloft is evident. Local strong updrafts occur both in the frontal lobes of marine cold air and in the prefrontal warm air ascending the wedge of windward lobes. Downdrafts form behind the lifted marine cold air and trap air pollutants. These fine‐scale structures and vertical motions are repeatedly strengthened by the short‐term disturbances of gravity currents that move onshore and collide with the SBF. They are also affected by buildings and determine the detailed variations of surface winds. We conclude that advanced observation and modeling systems can potentially improve the prediction of coastal weather and environment.

The FastEddy® Resident‐GPU Accelerated Large‐Eddy Simulation Framework: Model Formulation, Dynamical‐Core Validation and Performance Benchmarks

“…In addition, the CP method is computationally efficient, a desired quality in the context of an accelerated GPU framework targeting predictive capabilities for microscale turbulence phenomena. The CP method has been proven to be an efficient technique to generate inflow turbulence and demonstrated on a variety of problems including full physics coupled mesoscale‐LES atmospheric simulations (Muñoz‐Esparza et al, 2017, 2018) and sea breeze fronts (Chen et al, 2019), other semiidealized scenarios dealing with ocean‐island interactions and cloud formation (Jähn et al, 2016), sea breeze over an urban‐like coast (Jiang et al, 2017), snow formation and precipitation (Chu et al, 2018), and flow and turbulence in urban scenarios (Lee et al, 2019). An example of the use of the CP method to develop forcing‐consistent turbulence in FastEddy is presented in section 4.4, for the validation of flow over heterogeneous terrain.…”

Data collected using small uncrewed aircraft system during the TRacking Aerosol Convection Interactions ExpeRiment (TRACER)

“…Within the SBF, regions of enhanced convergence form due to the collision with horizontal convective rolls and increase vertical motion (Atkins et al, 1995;Iwai et al, 2008). Heterogeneities in the SBF are compounded by the addition of the bay breeze and urban land use (Miller et al, 2003;Chen et al, 2019). This directly impacts public health since ABL kinematics and stability factor into aerosol and trace gas transportation, or lack thereof in times of stagnation (Caicedo et al, 2019).…”

Convection Initiation Associated with the Merger of an Immature Sea-Breeze Front and a Gust Front in Bohai Bay Region, North China: A Case Study

“…The basic typical structures or circulations of a mature sea-breeze circulation are considered as rear-to-front feeder flow in the mid-lower level of the sea-breeze current (SBC), SBF head at the leading edge of the SBC, significant convergent updraft at the leading edge of the SBF, Kelvin-Helmholtz Billows (KHBs) (KHBs defined as streamwise vortex structures arising in the strongly sheared braids between adjacent billows or within the billow cores at the interface between fluids of differing densities [22][23][24][25]), behind the head of the SBF, front-to-rear return flow above the KHBs, and vertical rotor circulations (i.e., closed vertical circulation) following closely to the leading edge of the SBF [16,[26][27][28][29][30]. If some of these structures or circulations are not yet formed in a sea-breeze circulation, the SBF is considered as an immature SBF.…”