Raffaele Montuoro

Western boundary currents regulated by interaction between ocean eddies and the atmosphere

Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean’s western boundaries. Even with an enhanced grid resolution to resolve ocean mesoscale eddies—energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents—the bias problem can still persist; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air–sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20–40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models’ representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events, as well as in the projection of the effect on these events of climate change.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy–atmosphere interaction in forecast and climate models.

Photoionization cross sections calculation with mixed L2 basis set: STOs plus B-splines. Results for N2 and C2H2 by KM-RPA method

Abstract A new mixed L2 basis set, built from multicenter STOs and single-center radial B-Splines, is proposed to evaluate the differential photoionization cross section of molecules. As a first comparison we report the results for nitrogen and acetylene molecules, whose photoionization cross sections, since they have been the object of very numerous studies both experimentally and theoretically, represent a reliable test. The theoretical approach utilized to evaluate the continuum is based upon the K-Matrix (KM) determination in the interacting channels random phase approximation framework (IC-RPA) and the results obtained with the new basis set are in good agreement with the experiment and with the best calculations available. Thus the mixed basis employed appears very adequate to describe the electronic continuum and the present calculations are helpful in the assignment of some fine details in the low energy portion of the spectrum. In the high energy region, although the rough behaviour agrees with the experiment, the limitations of the KM-RPA method are such as to not account for a more detailed description of the spectrum.

Importance of Resolving Kuroshio Front and Eddy Influence in Simulating the North Pacific Storm Track

AbstractLocal and remote atmospheric responses to mesoscale SST anomalies associated with the oceanic front and eddies in the Kuroshio Extension region (KER) are studied using high- (27 km) and low-resolution (162 km) regional climate model simulations in the North Pacific. In the high-resolution simulations, removal of mesoscale SST anomalies in the KER leads to not only a local reduction in cyclogenesis but also a remote large-scale equivalent barotropic response with a southward shift of the downstream storm track and jet stream in the eastern North Pacific. In the low-resolution simulations, no such significant remote response is found when mesoscale SST anomalies are removed. The difference between the high- and low-resolution model simulated atmospheric responses is attributed to the effect of mesoscale SST variability on cyclogenesis through moist baroclinic instability. It is only when the model has sufficient resolution to resolve small-scale diabatic heating that the full effect of mesoscale SST...

Quasibound continuum states in SiF4 (D̃A12) photoionization: Photoelectron-vibrational coupling

The authors report a fully vibrationally resolved photoelectron spectroscopy investigation of a nonplanar molecule studied over a range of excitation energies. Experimental results for all four fundamental vibrational modes are presented. In each case significant non-Franck-Condon effects are seen. The vibrational branching ratio for the totally symmetric mode nu1+ is found to be strongly affected by resonant excitation in the SiF4+ (D2A1) photoionization channel. This is shown to be the result of two distinct shape resonances, which for the first time have been both confirmed by theoretical calculations. Vibrationally resolved Schwinger photoionization calculations are used to understand the vibronic coupling for the photoelectrons, both using ab initio and harmonic vibrational wave functions.

A Rapid Response Study of the Hercules Gas Well Blowout

On 20 April 2010, the Deepwater Horizon drilling rig lost well control while drilling at the Macondo prospect in the Gulf of Mexico. At the time of the Macondo blowout, the academic scientific community was ill prepared to initiate and rapidly conduct the necessary coordinated interdisciplinary studies of the environments around the discharge area.

Mixed L2 basis set: STOs plus B-Splines. Calculation of the differential photoionization cross-section of Li2

Abstract The convenience afforded by the use of L 2 functions in the calculation of the photoionization cross-section and of others properties depending upon the electronic continuum has prompted the examination of particular basis sets that, among those derived, could be able to mimic the continuum states in an extended region of space. Here results are reported for the differential photoionization cross-section of the Li 2 molecule, where a mixed L 2 basis set comprising multi-center STOs plus single-center radial B-Splines times spherical harmonics was employed.

The effect of vibrational motion on the dynamics of shape resonant photoionization of BF3 leading to the state of

We present the results of an experimental and theoretical investigation of vibrationally resolved valence shell photoionization of BF3 leading to the state of , where vibronic coupling and shape resonances are known to be important. The experimental vibrational branching ratios for multiple quantum excitations of the symmetric stretching mode of the ion as well as for the single vibrational excitation of the asymmetric stretching mode are compared with the predictions of single-channel Schwinger variational calculations performed within the Chase adiabatic approximation to obtain vibrational-state specific cross sections. The presence of a shape resonance in the continuum of symmetry is seen to lead to significant non-Franck–Condon intrachannel vibronic coupling effects. The breakdown in the Franck–Condon approximation is due to the sensitivity to the asymmetric stretching mode of the energy of the resonance and the magnitude of the transition moment for exciting the resonance. However, there are indications that interchannel vibronic coupling effects may also be significant in this system.