Bayesian methods of vector autoregressions with tensor decompositions

Vector autoregressions (VARs) are popular in analyzing economic time series. However, VARs can be over-parameterized if the numbers of variables and lags are moderately large. Tensor VAR, a recent solution to overparameterization, treats the coefficient matrix as a third-order tensor and estimates the corresponding tensor decomposition to achieve parsimony. In this paper, the inference of Tensor VARs is inspired by the literature on factor models. Firstly, we determine the rank by imposing the Multiplicative Gamma Prior to margins, i.e. elements in the decomposition, and accelerate the computation with an adaptive inferential scheme. Secondly, to obtain interpretable margins, we propose an interweaving algorithm to improve the mixing of margins and introduce a post-processing procedure to solve column permutations and sign-switching issues. In the application of the US macroeconomic data, our models outperform standard VARs in point and density forecasting and yield interpretable results consistent with the US economic history

Response of the tropical Pacific Ocean to wind changes related to global warming from simulations with an ocean general circulation model

A suite of numerical experiments is implemented with an ocean general circulation model (OGCM) to ex-amine the roles of wind stress and wind speed for oceanic changes in the tropical Pacific under global warming. In particular, we turned off the changes of wind stress and/or wind speed in the model to identify the effects of wind-driven ocean circulation and air-sea latent heat flux (i.e., its portion through the wind speed influence on the efficiency of latent heat flux). Results show that 1) the wind stress change appears to be a key forcing mechanism for weakening the tropical surface currents as well as for the oceanic changes in the equatorial thermocline, while it only contributes secondarily to the sea surface temperature (SST) pattern formation in the tropics; 2) the wind speed change is the leading cause for the minimum warming over the southeast subtropics and for a stronger surface warming in the northern hemisphere than in the southern hemisphere; and 3) the enhanced surface warming along the equator is mainly due to the effect of warming in the absence of wind stress and wind speed changes, and this effect also plays a significant role for changing the equatorial thermocline

A multifunctional tripodal fluorescent probe for the recognition of Cr3+, Al3+, Zn2+ and F− with controllable ESIPT processes

Three 4-(benzo[d]thiazol-2-yl)-2,5-dihydroxybenzaldehyde fluorophores were introduced to construct a tripodal multifunctional ESPIT fluorescence probe L. The fluorescent analysis revealed that probe L exhibited excellent recognition capabilities towards Cr3+, Al3+, Zn2+ and F− ions with large Stokes shifts. Furthermore, under optimal conditions, the detection limit of probe L towards Cr3+, Al3+, Zn2+ and F− were low, of the order of 10−8 M, which indicated that probe L was sensitive to these four ions. Interestingly, the fluorescent and 1H NMR titration experiments revealed that the recognition mechanism of probe L towards the ions Cr3+, Al3+, Zn2+ and F− were different. The presence of Cr3+ and Al3+ recovered the ESIPT, but the presence of Zn2+ trigger a moderate deprotonation of the phenolic OH and induced an ESIPT red-shifted (60 nm) emission wavelength. Finally, the presence of F− completely deprotonated the free phenolic OH and a remarkable red-shifted (130 nm) ESIPT emission was observed. In other words, the ESIPT process of probe L is controllable. Furthermore, the utility of probe L as a biosensor in living cells (PC3 cells) towards Cr3+, Al3+ and Zn2+ ions has been demonstrated

Response of the Pacific Ocean circulation to climate change

The response of the Pacific Ocean circulation to climate change is investigated by comparing solutions from a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled models for a present-day climate (the 20C3M experiments) and a future, warmer climate (the SRESA1B experiments). Under the warmer climate scenario, the oceanic changes in the tropical Pacific include a relatively weak warming of the western equatorial thermocline, a weakening of the surface current system and a complicated change in the structure of the Equatorial Undercurrent (EUC) with an increased flow in its upper branch but a decreased flow in its lower branch. As the climate warms, the North Pacific Ocean features a basin-scale reduction in mixed layer depth, a weakening of the subtropical countercurrent (STCC), a northward shift of the Kuroshio Extension (KE) and an overall slowdown of the subtropical gyre. In the South Pacific, the warmer climate induces significant changes in the upper ocean of the eastern subtropics including a relatively weak warming, a deepening of mixed layer depth and an anticylonic circulation

Analysis of Ionospheric Disturbances Caused by the 2018 Bering Sea Meteor Explosion Based on GPS Observations

The Bering Sea meteor explosion that occurred on 18 December 2018 provides a good opportunity to study the ionospheric disturbances caused by meteor explosions. Total electron content (TEC) is the core parameter of ionospheric analysis. TEC and its changes can be accurately estimated based on the Global Positioning System (GPS). TID is detected in time and frequency domain based on power spectrum and Butterworth filtering method. By analyzing the waveform, period, wavelength, propagation speed and space-time distribution of TID, the location of the TID source is determined, and the process of TID formation and propagation is understood. The TID caused by meteor explosions has significant anisotropy characteristic. Two types of TID were found. For the first type, the average horizontal propagation velocity is 250.22 ± 5.98 m/s, the wavelength is ~135–240 km, the average period is about 12 min, and the propagation distance is less than 1400 km. About 8 min after the meteor explosion, the first type of TID source formed and propagated radially at the velocity of 250.22 ± 5.98 m/s. For the second type, the propagation velocity is ~434.02 m/s. According to the waveform, period, wavelength and propagation velocity of the TID, it is diagnosed to be the midscale traveling ionospheric disturbances (MSTID). Based on the characteristics of TID, we infer that the TID is excited by the gravity waves generated by the meteor explosion, which is in accordance with the propagation law of gravity waves in the ionosphere. And it is estimated that the average velocity of the up-going gravity waves is about 464.58 m/s. A simple model was established to explain the formation and the propagation of this TID, and to verify the characteristics of the TID propagation caused by nuclear explosion, earthquake, tsunami, and Chelyabinsk meteorite blast. It is estimated that the position of the TID source is consistent with the meteor explosion point, which further indicates that the TID is caused by the meteor explosion and propagates radially

Human-induced intensified seasonal cycle of sea surface temperature

Abstract Changes in the seasonal cycle of sea surface temperature (SST) have far-reaching ecological and societal implications. Previous studies have found an intensified SST seasonal cycle under global warming, but whether such changes have emerged in historical records remains largely unknown. Here, we reveal that the SST seasonal cycle globally has intensified by 3.9 ± 1.6% in recent four decades (1983–2022), with hotspot regions such as the northern subpolar gyres experiencing an intensification of up to 10%. Increased greenhouse gases are the primary driver of this intensification, and decreased anthropogenic aerosols also contribute. These changes in anthropogenic emissions lead to shallower mixed layer depths, reducing the thermal inertia of upper ocean and enhancing the seasonality of SST. In addition, the direct impacts of increased ocean heat uptake and suppressed seasonal amplitude of surface heat flux also contribute in the North Pacific and North Atlantic. The temperature seasonal cycle is intensified not only at the ocean surface, but throughout the mixed layer. The ramifications of this intensified SST seasonal cycle extend to the seasonal variation in upper-ocean oxygenation, a critical factor for most ocean ecosystems

Simulated response of North Pacific Mode Waters to global warming

This study investigates the response of the Mode Waters in the North Pacific to global warming based on a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models. Solutions between a present-day climate and a future, warmer climate are compared. Under the warmer climate scenario, the Mode Waters are produced on lighter isopycnal surfaces and are significantly weakened in terms of their formation and evolution. These changes are due to a more stratified upper ocean and thus a shoaling of the winter mixing depth resulting mainly from a reduction of the ocean-to-atmosphere heat loss over the subtropical region. The basin-wide wind stress may adjust the Mode Waters indirectly through its impact on the surface heat flux and subduction process. Copyright 2009 by the American Geophysical Union

Dynamics of the block Island Sound estuarine plume

Buoyant discharge of freshwater from Long Island Sound (LIS) forms a seasonal buoyant plume outside Block Island Sound (BIS) between the coast of Long Island and the denser shelf waters. The plume\u27s seasonal variability and its response to tides, winds, and surface heating are investigated through a series of process-oriented experiments using the Regional Ocean Modeling System (ROMS). Results show the importance of river discharge, wind directions, and surface heating in the seasonal variation of the BIS buoyant plume. In winter and spring, the plume is intermediate with a large surface offshore extension detached from the bottom. From winter to spring, the river discharge increases; meanwhile, upwelling-favorable winds keep dominating. They compete with the increase of surface heating and generate a broader buoyant plume in spring than in winter. In summer, the plume is bottom advected with most of its width in contact with the bottom and is featured with the steepest isopycnals and narrowest plume, which is driven by a combination of strong insolation, weak buoyant discharge from LIS, and feeble winds. In fall, although the river discharge is comparable to that in winter, the upwelling-favorable wind is relatively weaker, corresponding to a narrower intermediate plume

Increase of South Pacific eastern subtropical mode water under global warming

The response of South Pacific Eastern Subtropical Mode Water (SPESTMW) to global warming is investigated by comparing solutions from a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled models between a present-day climate and a future, warmer climate. Under the warmer climate scenario, the SPESTMW extends southwestward and is significantly increased in volume. This is because all the local surface forcing mechanisms (i.e., wind stress, heat and freshwater fluxes) in the eastern subtropical South Pacific tends to de-stratify the upper ocean and thus deepen the mixed layer. Further, a suite of process-oriented experiments with an ocean general circulation model suggest that it is the intensified southeast trade winds under the warmer climate that promotes more heat flux from the ocean into the atmosphere that then results in a deepening of the mixed layer in the eastern subtropics of the South Pacific. Copyright © 2011 by the American Geophysical Union

Response of pacific subtropical-tropical thermocine water pathways and transports to global warming

Global wanning may change the thermocline water pathways and transports from the subtropics to the tropics in the Pacific Ocean, which are known to have profound implications for the El Nino-Southern Oscillation (ENSO) and thereby global climate. This study investigates the changes by comparing solutions between a present-day climate and a future, warmer climate from a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models. As the climate warms, although the total transport from the subtropics to the tropics exhibits no significant change, transport via western boundary pathways increases and via interior pathways decreases. This shift is due to high potential vorticity (PV) zones that extend further westward, thus dynamically guiding thermocline water away from interior pathways to prefer western boundary pathways from the subtropics to the tropics. Additionally, a warmer climate induces a large temperature increase near the sea surface in the eastern tropics and a significantly enhanced Equatorial Undercurrent (EUC) in the western and central Pacific; the former is related to the decreased transport through interior pathways and the latter is linked to the increased transport through western boundary pathways. Implications of the results of this study are also discussed. © 2009 by the American Geophysical Union