Search

As an important part of the Indo-Pacific warm pool, the Indian Ocean has great significance for research on the Asian monsoon system and global climate change. From the 1960s onward, several international and regional programs have led to important new insights into the Indian Ocean. The eastern Tropical Indian Ocean Observation Network (TIOON) was established in 2010. The TIOON consists of two parts: large-scope observations and moored measurements. Large-scope observations are performed by the eastern Tropical Indian Ocean Comprehensive Experiment Cruise (TIO-CEC). Moored measurements are executed by the TIOON mooring array and the hydrological meteorological buoy. By 2019, 10 successful TIO-CEC voyages had been accomplished, making this mission the most comprehensive scientific investigation in China. The TIO-CEC voyages have collected temperature/salinity profiles, GPS radiosonde profiles, and other observations in the Indian Ocean. To supplement the existing buoy array in the Indian Ocean, an enhanced TIOON mooring array consisting of eight subthermocline acoustic Doppler current profiler (ADCP) moorings, was established since 2013. The TIOON mooring equipped with both upward-looking and downward-looking WHLS75K ADCP provide valuable current monitoring information to depth of 1,000 m in the Indian Ocean. To improve air–sea interaction monitoring, two real-time hydrological–meteorological buoys were deployed in 2019 and 2020 in the equatorial Indian Ocean. A better understanding of the Indian Ocean requires continuous and long-term observations. The TIOON program and other aspiring field investigation programs will be promoted in the future.

Selenium (Se) has been recognized as a key trace element that is associated with growth of primary producers in oceans. During March and May 2018, surface water (67 samples) was collected and measured by HG-ICP-MS to investigate the distribution and behavior of selenite [Se(IV)], selenate [Se(VI)] and dissolved organic selenides (DOSe) concentrations in the Zhujiang River Estuary (ZRE), South China Sea (SCS) and Malacca Straits (MS). It showed that Se(IV) (0.14–3.44 nmol/L) was the dominant chemical species in the ZRE, related to intensive manufacture in the watershed; while the major species shifted to DOSe (0.05–0.79 nmol/L) in the MS, associated with the wide coverage of peatland and intensive agriculture activities in the Malaysian Peninsula. The SCS was identified as the northern and southern sections (NSCS and SSCS) based on the variations of surface circulation. The insignificant variation of Se(IV) in the NSCS and SSCS was obtained in March, potentially resulting from the high chemical activity and related preferential assimilation by phytoplankton communities. Contrastively, the lower DOSe concentrations in the SSCS likely resulted from higher primary production and utilization during March. During May, the concentration of Se(IV) remained low in the NSCS and SSCS, while DOSe concentrations increased notably in the SSCS, likely due to the impact of terrestrial inputs from surface current reversal and subsequent accumulation. On a global scale, DOSe is the dominant Se species in tropical oceans, while Se(IV) and Se(VI) are major fractions in high-latitude oceans, resulting from changes in predominated phytoplankton and related biological assimilation.

The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data are critical for achieving a better understanding of waves. In this study, the wave measurements based on a high-precision wave gauge were analyzed and observation data over approximately two years at a sampling frequency of 2 Hz were obtained. The wave system in the Pearl River Estuary was found to deviate from the assumption of a stationary stochastic process similar to that in the open ocean, due to the effects of abnormal waves caused by human activities. Therefore, traditional distribution functions such as Rayleigh and Weibull were not suitable for accurately fitting the main wave parameters (Hs, Tp, etc.), particularly in the tail. Consequently, abnormal wave signals were extracted from all wave sets, and through the comparison and analysis of the wave spectral features, it was determined that these abnormal waves are caused by the ship wakes. The spectral characterization of these waves was performed to determine the characteristics of different ship wake processes. Ship wakes in the Pearl River Estuary are an important part of the wave system, and their wave height is significantly larger than the normal wave. Based on the spectral characteristics of ship wakes, this study proposed some news characteristics of ship wakes in the main channel of the Pearl River Estuary.

In this paper, we first establish a narrow region principle for systems involving the fractional Laplacian in unbounded domains, which plays an important role in carrying on the direct method of moving planes. Then combining this direct method with the sliding method, we derive the monotonicity of bounded positive solutions to the following fractional Laplacian systems in unbounded Lipschitz domains \begin{document}$ \Omega $\end{document} \begin{document}$ \begin{equation*} \left\{\begin{array}{r@{\ \ }c@{\ \ }ll} \left(-\Delta\right)^{s}u& = f'>without any decay assumptions on the solution pair \begin{document}$ (u,\,v) $\end{document} at infinity.

In this paper,we consider the solutions of the non-homogeneous elliptic obstacle problems with Orlicz growth involving measure data. We first establish the pointwise estimates of the approximable solutions to these problems via fractional maximal operators. As a result, we obtain pointwise and oscillation estimates for the gradients of solutions by the non-linear Wolff potentials, and these yield results on $C^{1,\alpha}$-regularity of solutions., Comment: Elliptic obstacle problem; Dini-BMO coefficients; Wolff potential; Restricted fractional maximal function

There continues to be debate on the wet and dry conditions in central China due to different geological archives and proxy interpretations. This study reconstructed multi-proxy sequences spanning intervals between 65 and 40 ka using high-precision Th-230 dates, which was carried out on a stalagmite from Yongxing cave in the middle Yangtze Valley located in the Meiyu belt, China. Merely according to the petrography of the sample, Heinrich (H) 5-H6, Dansgaard–Oeschger (DO) 9-DO18 (or even secondary changes including DO15a and DO15b; DO17a, DO17b, and DO17c) were directly identified alongside the oxygen isotope record. The δ13C, trace elements, mineralogical, and bio-geochemical proxies exhibited similar millennial changes to that of the δ18O. This provided an indication of responses to millennial-scale climatic events in the karst hydrological cycle, local environment, and soil vegetation; however, the sensitivities to these events differed. Petrographic analyses of the same stalagmite including scanning electrical microscope (SEM), X-ray diffraction (XRD), fluorescence intensity, the deposition rate, and the diameter index depicted a dry-cold climate during the H events, and a wet-warm climate during the DO cycles in the middle Yangtze Valley. These results are consistent with the peat records of Dajiuhu Lake in the same area. We suggest that a combination of Atlantic Meridional Overturning Circulation (AMOC) and El Niño-Southern Oscillation (ENSO) may exert a strong influence on the Meiyu region and the related precipitation. This work was funded by the National Nature Science Foundation of China (awards 42072207, 42071105, 41931178), Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application.

In this paper, we consider the nonlocal double phase problems in unbounded domains. At first, we establish a maximum principle for these problems. Then we prove the monotonicity and uniqueness of positive solutions by developing a sliding method for nonlocal double phase equations.

In this paper, we consider the generalized stationary Stokes system with $p$-growth and Dini-$\operatorname{BMO}$ regular coefficients. The main purpose is to establish pointwise estimates for the shear rate and the associated pressure to such Stokes system in terms of an unconventional nonlinear Havin-Maz'ya-Wolff type potential of the nonhomogeneous term in the plane. As a consequence, a symmetric gradient $L^{\infty}$ estimate is obtained. Moreover, we derive potential estimates for the weak solution to the Stokes system without additional regularity assumptions on the coefficients in higher dimensional space.

This paper focuses on weak solutions to the following variational inequality ∫ Ω 〈 a ( x , D u ) , D ( φ − u ) 〉 d x ≥ ∫ Ω 〈 | F | p − 2 F , D ( φ − u ) 〉 d x for all φ ∈ A ψ ( Ω ) = { w ∈ W 1 , p ( Ω ) | w ≥ ψ a.e. in Ω } , where the vector field a satisfies some growth and ellipticity conditions. We derive that the higher differentiability property of the weak solution u is related to the regularity of the assigned obstacle ψ and the nonhomogeneous term F under a suitable integer or fractional differentiability assumption on a ( x , ξ ) with respect to x.

The purpose of this paper is to study an inhomogeneous Dirichlet problem of a superquadratic nonlinear elliptic system with VMO coefficients in Reifenberg flat domains. We derive pointwise potential estimates for weak solution to the Dirichlet problem. As a consequence, we derive global integrability estimates for solutions with respect to Lorentz and Morrey norms.

A 230Th/U-dated stalagmite from Hulu Cave was analyzed for δ18O, δ13C, and trace elements. A ~10-yr-resolution δ18O record, spanning 51.7–42.6 ka, revealed Dansgaard-Oeschger (DO) events 14 to 11. A similar rapid transition and synchronous timing of the onset of DO 12 is evident between the Greenland and Hulu Cave records, which suggests a common forcing mechanism of DO cycles in the North Atlantic and monsoonal region of Asia. Centennial-scale monsoonal oscillations in the cave δ18O record are indicative of hydroclimatic instability during interstadials. After removing the signals of remote moisture sources, the proportion of moisture from nearby sources is found to be higher during stadials than during interstadials. To explain this, we propose that the movement of the westerly jet is an important control on the balance of nearby and distant moisture sources in East Asia. In addition, the records of δ13C and trace element ratios, which are proxies of local environmental changes, resemble the δ18O record on the scale of DO cycles, as well as on even shorter timescales. This suggests that hydrological processes and biological activity at the cave site respond sensitively to the monsoonal changes.

The last interglacial contains information about how climate behaves during a warm period comparable to the current interval. However, there is no consensus on the key signatures and force of the last interglacial climate changes at present. Here we present a high-resolution stalagmite oxygen isotope record from central China, which spans from 123.3 to 116.8 ka. The stalagmite δ18O time-series bears a resemblance to changes in Northern Hemisphere summer insolation before the demise of the last interglacial, like the condition during the Holocene. Superimposed on the long-term δ18O record is a pronounced shift to more positive values at around 121.6 ka, indicating a switch of the Asian monsoon mean state into a weaker condition. This monsoon shift correlates with a decrease in the mean state of the South American Summer Monsoon, and a well-known abrupt mid-Eemian cooling event at high latitudes. These correlations indicate broad-scale features of the climate shift over the warm last interglacial. Another positive δ18O shift of up to 3.5‰ occurred at around 120 ka, representing the demise of the last interglacial Asian monsoon. By comparing the stalagmite δ18O records against changes in ice volume and summer insolation during the last interglacial and recent Holocene, respectively, we conclude that the decreasing Northern Hemisphere summer insolation dominated the rapid demise of the last interglacial in the Asian monsoon region.

Let (X, d, μ) be a metric measure space satisfying both the upper doubling and the geometrically doubling conditions in the sense of Hytonen. In this paper, the authors obtain the boundedness of the commutators of θ-type Calderon-Zygmund operators with RBMO functions from L∞ (μ) into RBMO(μ) and from $$H_{{\rm{at}}}^{1,\;\infty }\left( \mu \right)$$ into L1 (μ), respectively. As a consequence of these results, they establish the Lp (μ) boundedness of the commutators on the non-homogeneous metric spaces.

Pointwise estimates of weak solution pairs to a stationary Stokes system with small [Formula: see text] semi-norm coefficients are established in Reifenberg flat domains by using the restricted sharp maximal function. These pointwise estimates provide a unified treatment of the Calderón–Zygmund estimates for the solution pair to Stokes systems in [Formula: see text] and [Formula: see text] spaces.

This paper deals with the following Choquard equations with fractional p -Laplacian − Δ p s u = C n , t | x | 2 t − n ∗ u q u q − 1 in R n , u > 0 on R n , where 0 s , t 1 , 2 p ∞ , p − 1 q ∞ and n ≥ 2 . By constructing a decay at infinity theorem and a narrow region principle, we establish the radial symmetry of positive solutions based on the generalized direct method of moving planes.