DataSheet1_Decadal modulation of ENSO and IOD impacts on the Indian Ocean upwelling.docx

The decadal modulations are observed in impacts of El Niño and Southern Ocean (ENSO) and Indian Ocean Dipole (IOD) on the tropical Indian Ocean upwelling. Here, we explore important contributors to the decadal modulations by combining the observational data since 1958 and statistical model simulations. A Bayesian Dynamic Linear Model (BDLM), which represents the temporal modulations of the IOD and ENSO impacts, reproduces the timeseries of the eastern and western Indian Ocean (EIO and WIO) upwellings more realistically than a conventional Static Linear regression Model does. The time-varying regression coefficients in BDLM indicate that the observed shift of the IOD impact on the EIO upwelling around 1980 is mainly due to the changes of alongshore wind stress forcing and the sensitivity of the upper ocean temperature in the EIO through the surface warming tendency and the enhanced ocean stratification. In contrast, the impacts of ENSO and IOD on the WIO are modulated in relation to the decadal variability of the tropical Pacific Ocean. When the eastern tropical Pacific Ocean is observed warmer on decadal timescales, the accompanying changes of the dominant ENSO flavors contribute to modulating the strengths of the atmospheric convective activity over the Indian-Pacific warm pool and the easterly wind variations in the equatorial Indian Ocean.</p

Effect of the Hydrophilic Component in Aromatic Ionomers: Simple Structure Provides Improved Properties as Fuel Cell Membranes

To elucidate the effect of the hydrophilic component on the properties of aromatic ionomers, we have designed for the first time one of the simplest possible structures, the sulfo-1,4-phenylene unit, as the hydrophilic component. A modified Ni-mediated coupling polymerization produced the title aromatic ionomers composed of sulfonated <i>p</i>-phenylene groups and oligo­(arylene ether sulfone ketone)­s, as high-molecular-weight polymers (<i>M</i>_w = 202–240 kDa), resulting in the formation of tough, flexible membranes. The aromatic ionomer membranes showed well-developed hydrophilic/hydrophobic phase separation. Comparison with our previous aromatic ionomer membrane containing sulfonated benzophenone groups as a hydrophilic component revealed that the simple sulfophenylene structure (i.e., no polar groups such as ether, ketone, or sulfone groups in the hydrophilic component) was effective for the improvement of the membrane properties, i.e., reduced water uptake and excellent mechanical stability under humidified conditions. Furthermore, because of the high local ion exchange capacity (IEC), the simple structure led to high proton conductivity, especially at low humidity (reaching up to ca. 7.3 mS/cm at 80 °C and 20% RH), which is one of the highest values reported thus far. The improved properties of the membranes were also confirmed in an operating fuel cell

Simple, Effective Molecular Strategy for the Design of Fuel Cell Membranes: Combination of Perfluoroalkyl and Sulfonated Phenylene Groups

Proton-conducting membranes are key materials in polymer electrolyte fuel cells. In addition to high proton conductivity and durability, a membrane must also support good electrocatalytic performance of the catalyst layer at the membrane–electrode interface. We herein propose an effective molecular approach to the design of high-performance proton-conducting membranes designed for fuel cell applications. Our new copolymer (SPAF) is a simple combination of perfluoroalkylene and sulfonated phenylene groups. Because this ionomer membrane exhibits a well-controlled finely phase-separated morphology, based on the distinct hydrophilic–hydrophobic differences along with the polymer chain, it functions well in an operating fuel cell with good durability under practical conditions. The advantages of this ionomer, unlike typical perfluorosulfonic acid ionomers (e.g., Nafion), include easy synthesis and versatility in molecular structure, enabling the fine-tuning of membrane properties

Double-Layer Ionomer Membrane for Improving Fuel Cell Performance

A double-layer ionomer membrane, thin-layer Nafion (perfluorinated sulfonic acid polymer) on a sulfonated aromatic block copolymer (SPK-bl-1), was prepared for improving fuel cell performance. Each component of the double-layer membrane showed similar phase-separated morphologies to those of the original membranes. A fuel cell with the double-layer membrane exhibited lower ohmic resistance and higher cathode performance than those with the original SPK-bl-1 membrane despite their comparable water uptake and proton conductivity. Detailed electrochemical analyses of fuel cell data suggested that the thin Nafion interlayer contributed to improving the interfacial contact between the SPK-bl-1 membrane and the cathode catalyst layer and to mitigating excessive drying of the membrane. The results provide new insight on designing high-performance fuel cells with nonfluorinated ionomer membranes such as sulfonated aromatic polymers