The formation of small-scale atmospheric vortices via horizontal shearing instability

Motivated by recent high-resolution observations of small-scale atmospheric vortices along near-surface boundaries, this study presents a series of simulations that attempt to replicate the dynamics of the dryline and surrounding boundary layer with special emphasis on misocyclones. The first simulation was a real data case, initialized and forced through time-dependent lateral boundary conditions via analyses of temperature, moisture, and momentum from the 22 May 2002 IHOP dataset. The second series of simulations were barotropic runs, initialized with a north-south oriented constant vorticity shear zone and north-south periodic boundary conditions. The third series of simulations were baroclinic, where the shear zone also contained and east-west temperature gradient. The barotropic and baroclinic simulations had varying magnitudes of shear and shear zone widths (corresponding to differing initial vorticity values) across the runs. Additionally, several barotropic simulations were rerun with moisture included to assess preferred could formation regions. The real data simulation produced several misocyclones with characteristics consistent with those observed along near-surface boundaries in the atmosphere. Several of these misocyclones also had features resembling those observed in many laboratory studies and other numerical studies. Many of these features were also found in the barotropic simulations (i.e. instabilities developed into elliptical cores that precess, contain pressure perturbations in their centers, and evolve with cores connected by vorticity braids). To assess the instability mechanism, the results were compared to linear theory. Excellent agreement was found between predictions from linear theory in terms of wavenumber of maximum growth as a function of shear zone width and growth rate as a function of shear zone vorticity, suggesting to a very good first approximation, horizontal shearing instability (HSI) is responsible for the growth of initial small perturbations. It was also found that predictions of linear theory tend to extend well into the nonlinear regime. The baroclinic simulations were more complicated and allowed for tilting and stretching of vorticity not seen in the barotropic simulations. As the shear zones contract due to frontogenesis, vorticity increases, thus increasing the growth rates and the wavenumber of maximum growth. An attempt was made to model the contraction and apply a “modified linear theory” to the results, by allowing linear theory to have a time-varying shear zone width. This modified model provided excellent agreement with the simulated results in terms of growth rate and wavenumber of maximum growth. Finally, an attempt was made to assess preferred regions of cumulus formation by including moisture in the real data case and in several barotropic simulations. It was found that maximum updrafts and simulated cumuli tend to form along the periphery of cores and/or along the braided regions adjacent to the cores. Due to the important modulating effect of misocyclone development via HSI and subsequent moisture transport, cumulus spacing and size/depth was also dependent on the shear zone width and vorticity

A Multiscale Observational Case Study of the Development of an Isolated High Plains Tornadic Supercell

On 21 May 1995, a strong tornado developed with an isolated supercell in southwestern Nebraska. Largescale conditions were not supportive of a tornadic thunderstorm outbreak; however, evidence suggests significant mesoscale enhancements produced a local environment favorable for strong tornado formation. This case study illustrates the importance of ‘‘situation awareness’’ and illustrates how mesoscale enhancements must be anticipated by forecasters in order to properly assess rapidly changing atmospheric conditions

Connecting Land–Atmosphere Interactions to Surface Heterogeneity in CHEESEHEAD19

The Chequamegon Heterogeneous Ecosystem Energy-Balance Study Enabled by a High-Density Extensive Array of Detectors 2019 (CHEESEHEAD19) is an ongoing National Science Foundation project based on an intensive field campaign that occurred from June to October 2019. The purpose of the study is to examine how the atmospheric boundary layer (ABL) responds to spatial heterogeneity in surface energy fluxes. One of the main objectives is to test whether lack of energy balance closure measured by eddy covariance (EC) towers is related to mesoscale atmospheric processes. Finally, the project evaluates data-driven methods for scaling surface energy fluxes, with the aim to improve model–data comparison and integration. To address these questions, an extensive suite of ground, tower, profiling, and airborne instrumentation was deployed over a 10 km × 10 km domain of a heterogeneous forest ecosystem in the Chequamegon–Nicolet National Forest in northern Wisconsin, United States, centered on an existing 447-m tower that anchors an AmeriFlux/NOAA supersite (US-PFa/WLEF). The project deployed one of the world’s highest-density networks of above-canopy EC measurements of surface energy fluxes. This tower EC network was coupled with spatial measurements of EC fluxes from aircraft; maps of leaf and canopy properties derived from airborne spectroscopy, ground-based measurements of plant productivity, phenology, and physiology; and atmospheric profiles of wind, water vapor, and temperature using radar, sodar, lidar, microwave radiometers, infrared interferometers, and radiosondes. These observations are being used with large-eddy simulation and scaling experiments to better understand submesoscale processes and improve formulations of subgrid-scale processes in numerical weather and climate models

On the Use of Rotary-Wing Aircraft to Sample Near-Surface Thermodynamic Fields: Results from Recent Field Campaigns

Rotary-wing small unmanned aircraft systems (sUAS) are increasingly being used for sampling thermodynamic and chemical properties of the Earth’s atmospheric boundary layer (ABL) because of their ability to measure at high spatial and temporal resolutions. Therefore, they have the potential to be used for long-term quasi-continuous monitoring of the ABL, which is critical for improving ABL parameterizations and improving numerical weather prediction (NWP) models through data assimilation. Before rotary-wing aircraft can be used for these purposes, however, their performance and the sensors used therein must be adequately characterized. In the present study, we describe recent calibration and validation procedures for thermodynamic sensors used on two rotary-wing aircraft: A DJI S-1000 and MD4-1000. These evaluations indicated a high level of confidence in the on-board measurements. We then used these measurements to characterize the spatiotemporal variability of near-surface (up to 300-m AGL) temperature and moisture fields as a component of two recent field campaigns: The Verification of the Origins of Rotation in Tornadoes Experiment in the Southeast U.S. (VORTEX-SE) in Alabama, and the Land Atmosphere Feedback Experiment (LAFE) in northern Oklahoma

Correction: Lee, T. R., <i>et al.</i> On the Use of Rotary-Wing Aircraft to Sample Near-Surface Thermodynamic Fields: Results from Recent Field Campaigns. <i>Sensors</i> 2019, <i>19</i>(1), 10

The authors wish to make the following correction to this paper [...

Bridging across length scales: Multi-scale ordering of supported lipid bilayers via lipoprotein self-assembly and surface patterning

We show that a two-step process, involving spontaneous self-assembly of lipids and apolipoproteins and surface patterning, produces single, supported lipid bilayers over two discrete and independently adjustable length scales. Specifically, an aqueous phase incubation of DMPC vesicles with purified apolipoprotein A-I results in the reconstitution of high density lipoprotein (rHDL), wherein nanoscale clusters of single lipid bilayers are corralled by the protein. Adsorption of these discoidal particles to clean hydrophilic glass (or silicon) followed by direct exposure to a spatial pattern of short-wavelength UV radiation directly produces microscopic patterns of nanostructured bilayers. Alternatively, simple incubation of aqueous phase rHDL with a chemically patterned hydrophilic/hydrophobic surface produces a novel compositional pattern, caused by an increased affinity for adsorption onto hydrophilic regions relative to the surrounding hydrophobic regions. Further, by simple chemical denaturation of the boundary protein, nanoscale compartmentalization can be selectively erased, thus producing patterns of laterally fluid, lipid bilayers structured solely at the mesoscopic length scale. Since these aqueous phase microarrays of nanostructured lipid bilayers allow for membrane proteins to be embedded within single nanoscale bilayer compartments, they present a viable means of generating high-density membrane protein arrays. Such a system would permit in-depth elucidation of membrane protein structure-function relationships and the consequences of membrane compartmentalization on lipid dynamics

Bridging across length scales: multi-scale ordering of supported lipid bilayers via lipoprotein self-assembly and surface patterning

We show that a two-step process, involving spontaneous self-assembly of lipids and apolipoproteins and surface patterning, produces single, supported lipid bilayers over two discrete and independently adjustable length scales. Specifically, an aqueous phase incubation of DMPC vesicles with purified apolipoprotein A-I results in the reconstitution of high density lipoprotein (rHDL), wherein nanoscale clusters of single lipid bilayers are corralled by the protein. Adsorption of these discoidal particles to clean hydrophilic glass (or silicon) followed by direct exposure to a spatial pattern of short-wavelength UV radiation directly produces microscopic patterns of nanostructured bilayers. Alternatively, simple incubation of aqueous phase rHDL with a chemically patterned hydrophilic/hydrophobic surface produces a novel compositional pattern, caused by an increased affinity for adsorption onto hydrophilic regions relative to the surrounding hydrophobic regions. Further, by simple chemical denaturation of the boundary protein, nanoscale compartmentalization can be selectively erased, thus producing patterns of laterally fluid, lipid bilayers structured solely at the mesoscopic length scale. Since these aqueous phase microarrays of nanostructured lipid bilayers allow for membrane proteins to be embedded within single nanoscale bilayer compartments, they present a viable means of generating high-density membrane protein arrays. Such a system would permit in-depth elucidation of membrane protein structure-function relationships and the consequences of membrane compartmentalization on lipid dynamics

Cryo-scanning transmission electron tomography of vitrified cells

Cryo-electron tomography (CET) of fully hydrated, vitrified biological specimens has emerged as a vital tool for biological research. For cellular studies, the conventional imaging modality of transmission electron microscopy places stringent constraints on sample thickness because of its dependence on phase coherence for contrast generation. Here we demonstrate the feasibility of using scanning transmission electron microscopy for cryo-tomography of unstained vitrified specimens (CSTET). We compare CSTET and CET for the imaging of whole bacteria and human tissue culture cells, finding favorable contrast and detail in the CSTET reconstructions. Particularly at high sample tilts, the CSTET signals contain more informative data than energy-filtered CET phase contrast images, resulting in improved depth resolution. Careful control over dose delivery permits relatively high cumulative exposures before the onset of observable beam damage. The increase in acceptable specimen thickness broadens the applicability of electron cryo-tomography