Interactions Between Tropical Cyclones and the Midlatitude Waveguide: Downstream Impacts and the Role of Convective Processes

Significant amplification to the waveguide can occur when a recurving tropical cyclone (TC) interacts with the midlatitude flow, leading to significant downstream impacts. To this point in time, TC-midlatitude waveguide interactions have been conceptualized as primarily being driven by large-scale processes, with convective-scale contributions having been parameterized or neglected. This three-part study diagnoses the impact TC-midlatitude waveguide interactions have on the intensity evolution of downstream TCs and the role convective-scale processes play in TC-midlatitude waveguide interactions. Recurving TCs in both the North Atlantic and western North Pacific basins frequently interact favorably with upstream troughs, where a favorable interaction entails the tightening of a pre-existing potential vorticity (PV) gradient on the eastern flank of the trough, leading to subsequent downstream flow amplification in the vicinity of a downstream TC. In the Atlantic, weakening downstream TCs are closer to the midlatitude waveguide on the southeastern edge of the amplified midlatitude ridge, whereas strengthening downstream TCs are further from the waveguide and equatorward of the amplified midlatitude ridge. Conversely, western North Pacific strengthening and weakening secondary TCs are primarily stratified by latitude, with weakening secondary TCs located poleward of their strengthening secondary TC counterparts. Convective-scale processes are shown to potentially play a role in determining the strength and downstream evolution of TC-midlatitude waveguide interactions. This importance of convective-scale processes on the large-scales is accomplished by way of an inverse energy cascade supported by the filamentation of intensely negative PV generated by deep, moist convection. These negative PV anomalies are generated by intense horizonal gradients of diabatic warming and exist primarily in the middle- to upper-troposphere. While preliminary sensitivity simulations suggest that convective-scale processes in particular regions of a TC-midlatitude waveguide interaction may not play a key role in determining the strength, and subsequent evolution of the interaction, that is not to say that convective-scale processes do not play a role at all. Additionally, the relative importance of convective-scale processes may depend on the particular TC-midlatitude waveguide interaction being studied

A Climatology of Extreme South American Andean Cold Surges

Interactions between the tropics and midlatitudes have been an ongoing area of research since the inception of meteorology. Cold surges represent one of several phenomena by which midlatitude features can modulate the atmosphere, both dynamically and thermodynamically, deep into the tropics. This study performs a climatology of particularly strong South American cold surges that follow along the Andes mountains to quantify the maximum extent to which these surges can modulate the atmosphere from the midlatitudes to the tropics. Data was collected for Austral winter (JJAS) from 1980-2010 (31 years). To identify events, standardized anomalies for 925 hPa meridional wind and temperature are calculated. To ensure the cold surges are on the stronger end of the spectrum, steep conditions of anomalies exceeding three above (below) zero for meridional wind (temperature) were set as the criteria which must occur in conjunction on the meso-alpha scale or larger. Using these criteria, 57 events are identified, and composites and area-averages are created, focused on the same fields used to identify the events. The duration of these events was approximately four days on average, with the strongest event lasting eight days. It is shown that some extreme cold surge events can have lasting impacts on the lower parts of atmosphere over much of northern South America, with anomalies up to three above (below) zero for meridional wind (temperature) reaching the southern Caribbean

The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility

RR Lyr stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way. This is because they are easy to find in the light curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr beyond 50 kpc in the outer halo of the Milky Way, excluding the Sgr streams, for which we have obtained moderate resolution spectra with Deimos on the Keck 2 Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447 candidate RR Lyr which were datamined using machine learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr we determine the radial velocity dispersion in the outer halo of the Milky Way to be ~90 km/s at 50 kpc falling to about 65 km/s near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as the -4 power of r.Comment: Accepted for publication in the Ap

P33. Design and evaluation of an Escherichia coli biomarker for indication of pH

Measuring pH is one of the most commonly used techniques in both the laboratory as well as the field due to its importance in a multitude of biochemical processes. Traditional methods of measuring pH may be highly developed in accuracy and precision but often involve disruption of the environment. Biological markers offer an alternative that allows for long-term pH monitoring. This innovative approach allows for vast applications such as in the manufacturing, food processing and research industries. Under moderate acidic conditions, the asr (acid shock RNA) gene is highly inducible and has been demonstrated to be crucial for growth at high acidities. The alx locus in E. coli contains a putative transporter preceded by a pH-induced riboregulator that operates under moderately alkaline conditions. In this study, vivid blue/purple and green/blue chromoproteins, cJBlue and amilCP respectively, were used as visual indicators. DH5α competent E. coli cells were transformed with recombinant plasmids containing either amilCP downstream the asr promoter or cjBlue downstream the alx promoter and 5’UTR, giving rise to the alx-cjBlue and asr-amilCP cell lines. Through this methodology, we were able to create strains of E. coli that expressed either a blue or blue-green chromoprotein under low or high pHs respectively

A rapid aerodynamic prediction method for unconventional transonic aircraft configurations

This paper presents some results comparing the use of the Full Potential equations, coupled with the turbulent integral boundary layer equations for aircraft transonic cruise analysis. Use of such a method in the conceptual design stage is shown to be capable of yielding accurate enough data in a few minutes on a single processor, where Navier - Stokes simulations on 100+ processors take several days

Roadmap of ultrafast x-ray atomic and molecular physics

X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (1020 W cm−2) of x-rays at wavelengths down to ~1 Ångstrom, and HHG provides unprecedented time resolution (~50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ~280 eV (44 Ångstroms) and the bond length in methane of ~1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science

The development of a simple method for drag estimation for wedge-like fairings in hypersonic flow

The addition of wedge-like fairings onto the side of missiles and space launch vehicles, to shield devices such as cameras or reaction jet nozzles, creates additional drag, particularly when in supersonic/hypersonic flow. An experimental and computational study was performed to obtain data on wedge configurations and develop simple theories for the drag due to these types of fairings

UPS, XPS, NEXAFS and Computational Investigation of Acrylamide Monomer

Acrylamide is a small conjugated organic compound widely used in industrial processes and agriculture, generally in the form of a polymer. It can also be formed from food and tobacco as a result of Maillard reaction from reducing sugars and asparagine during heat treatment. Due to its toxicity and possible carcinogenicity, there is a risk in its release into the environment or human intake. In order to provide molecular and energetic information, we use synchrotron radiation to record the UV and X-ray photoelectron and photoabsorption spectra of acrylamide. The data are rationalized with the support of density functional theory and ab initio calculations, providing precise assignment of the observed features