Robert J. Kurzeja

An Observational and Numerical Study of the Nocturnal Sea Breeze. Part I: Structure and Circulation

Abstract Characteristics of inland-penetrating nocturnal sea breezes at the Savannah River Site (SRS) in South Carolina are discussed. Detailed observations from an area tower network during the Stable Boundary Layer Experiment (STABLE) indicate passage of marine air through SRS on three different nights. Large-scale winds are directed onshore for the first two nights, resulting in similar boundary layer structure and stability on these nights, while synoptic winds on the third night are offshore, leading to stronger convergence and wedging of the marine air under the inland air mass. The Regional Atmospheric Modeling System (RAMS) is used to simulate conditions for the final two nights. General features of the sea breeze are captured by the model, including wind shifts, moisture increases, turbulence structure differences between the two nights, and the formation of Kelvin–Helmholtz billows along the interface of marine and return airflow.

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...

An Observational and Numerical Study of the Nocturnal Sea Breeze. Part II: Chemical Transport

Abstract Chemical transport at the Savannah River Site (SRS) in South Carolina during nocturnal sea-breeze passage is examined using simulations from a three-dimensional mesoscale dynamic model [(RAMS) Regional Atmospheric Modeling System] and a Lagrangian particle dispersion model (LPDM) and supplemental surface measurements of sulfur hexafluoride (SF6) obtained during a 1988 field campaign. Plume dispersion and regional transport were characterized by nights with onshore and offshore synoptic winds. For onshore winds, the sea breeze lifts, redirects, and broadens an initially narrow plume but maintains its general structure. Regional calculations reveal particle translations exceeding 100 km under these conditions. On the other hand, with offshore synoptic winds, frontal passage leads to stronger lifting, turbulence, and vertical shearing that fragments the plume. In addition, complicated recirculation of pollutants is possible and may increase chemical concentrations in areas near the source. Observed ...

Observations and model predictions of water skin temperatures at MTI core site lakes and reservoirs

The Savannah River Technology Center (SRTC) measured water skin temperatures at four of the Multi-spectral Thermal Imager (MTI) core sites. The depression of the skin temperature relative to the bulk water temperature ((Delta) T) a few centimeters below the surface is a complex function of the weather conditions, turbulent mixing in the water and the bulk water temperature. Observed skin temperature depressions range from near zero to more than 1.0 degree(s)C. Skin temperature depressions tend to be larger when the bulk water temperature is high, but large depressions were also observed in cool bodies of water in calm conditions at night. We compared (Delta) T predictions from three models (SRTC, Schlussel and Wick) against measured (Delta) Ts from 15 data sets taken at the MTI core sites. The SRTC and Wick models performed somewhat better than the Schlussel model, with RMSE and average absolute errors of about 0.2 degree(s)C, relative to 0.4 degree(s)C for the Schlussel model. The average observed (Delta) T for all 15 databases was -0.7 degree(s)C.

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

MTI thermal bands calibration at Ivanpah Playa with a Fourier transform infrared spectrometer

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DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY

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