David Werth

The Simulation of the Southern Great Plains Nocturnal Boundary Layer and the Low-Level Jet with a High-Resolution Mesoscale Atmospheric Model

AbstractA field project over the Atmospheric Radiation Measurement–Cloud and Radiation Test Bed (ARM–CART) site during a period of several nights in September 2007 was conducted to explore the evolution of the low-level jet (LLJ). Data were collected from in situ (a multilevel tower) and remote (sodar) sensors, and the observed LLJ activity during the project was found to agree well with data from earlier studies regarding jet speed, height, and direction. To study nocturnal boundary layer (NBL) behavior, the Regional Atmospheric Modeling System was used to simulate the ARM–CART NBL field experiment and was validated against the data collected from the site. This model was run at high resolution for calculating the interactions among the various motions within the boundary layer and their influence on the surface. The model faithfully simulated the formation and dissolution of the low-level nocturnal jet during a synoptic situation in which low pressure with warm southerly advection replaced high pressure...

Impact of Nocturnal Low-Level Jets on Near-Surface Turbulence Kinetic Energy

We report on the role of low-level jets (LLJs) on the modulation of near-surface turbulence in the stable boundary layer, focusing on the behaviour of the transport terms of the turbulence kinetic energy (TKE) budget. We also examine the applicability of Monin–Obukhov similarity theory (MOST) in light of these terms. Using coincident near-surface turbulence and LLJ data collected over a three-month period in South Carolina, USA, we found that turbulence during LLJ periods was typically stronger and more well-developed in comparison with periods without a LLJ. We found a local imbalance in the near-surface TKE budget, in which the imbalance (residual) term was typically positive (i.e., energy gain) and nearly in equilibrium with buoyant consumption. Based on a comparison with previous studies, we assume that this residual term represents mostly pressure transport. We found the behaviour of the residual term to be better delineated in the presence of LLJs. We found shear production to adhere to MOST remarkably well during LLJs, except under very stable conditions. Gain of non-local TKE via pressure transport, likely consisting of large-scale fluctuations, could be the cause of the observed deviation from the MOST

A case study of chlorine transport and fate following a large accidental release

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Detection of nuclear testing from surface concentration measurements: Analysis of radioxenon from the February 2013 underground test in North Korea

z-less prediction. The fact that this deviation was observed for periods with well-developed turbulence with an inertial subrange slope close to

Multi-scale decomposition of turbulent fluxes above a forest canopy

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THE SIMULATION OF FINE SCALE NOCTURNAL BOUNDARY LAYER MOTIONS WITH A MESO-SCALE ATMOSPHERIC MODEL

-5/3 indicates that such Kolmogorov turbulence is not a sufficient condition to guarantee the applicability of the MOST