Frontogenesis and Frontolysis of a Cold Filament Driven by the Cross-Filament Wind and Wave Fields Simulated by a Large Eddy Simulation

The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.

Spatial distribution and behavior of dissolved selenium speciation in the South China Sea and Malacca Straits during spring inter-monsoon period

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.

Partial regularity and nonlinear potential estimates for Stokes systems with super-quadratic growth

This paper builds a bridge between partial regularity theory and nonlinear potential theory for the following generalized stationary Stokes system with super-quadratic growth and continuous coefficients:-div A(x,Du)+■π=f,div u=0,where Du is the symmetric part of the gradient■u.We first establish anε-regularity criterion involving both the excess functional of the symmetric gradient Du and Wolff potentials of the nonhomogeneous term f to guarantee the local vanishing mean oscillation(VMO)-regularity of Du in an open subset Ω_(u) of Ω with full measure.Such anε-regularity criterion leads to a pointwise Wolff potential estimate of Du,which immediately infers that Du is partially C^(0)-regular under appropriate assumptions.Finally,we give a local continuous modulus estimate of Du.

Ice-volume and insolation influences on hydroclimate changes in central eastern China during the antepenultimate glacial period

The rainfall changes in East Asian summer monsoon(EASM)regions on the orbital timescale remain controversial due to the lack of reliable rainfall records.Here,we present new multiproxy records(δ^(18)O,δ^(13)C,Sr/Ca and Mg/Ca)of a230Thdated stalagmite from Hulu Cave in central eastern China.Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP(thousand years before present),approximately covering the antepenultimate glacial period.Theδ^(18)O record is dominated by the precessional cycles,suggesting that EASM responds to changes in Northern Hemisphere summer insolation(NHSI)on the orbital timescale.Significant correlations amongst theδ^(13)C,Sr/Ca and Mg/Ca suggest that a common factor,i.e.,the local hydrological cycle,controlled their variability,and their leading principal component can be used as a proxy linked to regional rainfall.This composite record bears a good similarity to those from the Chinese Loess Plateau,showing a gradually decreasing rainfall during the antepenultimate glacial period,consistent with changes in global ice volume.Superimposed on the long-term trend,three relative wetter intervals were responding to the higher NHSI periods,suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI.The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies,which shortened the duration of Meiyu and midsummer rainfall.The differences between the rainfall record and the stalagmiteδ^(18)O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation,but does not directly reflect the rainfall changes at the cave sites.

Boundedness of Commutators of θ-Type Calderón-Zygmund Operators on Non-homogeneous Metric Measure Spaces

Let(X, d, μ) be a metric measure space satisfying both the upper doubling and the geometrically doubling conditions in the sense of Hyt?nen. In this paper, the authors obtain the boundedness of the commutators of θ-type Calderón-Zygmund operators with RBMO functions from L∞(μ) into RBMO(μ) and from Hat1,∞(μ) 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.

Boundedness of θ-type Calderon-Zygmund operators on non-homogeneous metric measure space

Let （X,d,μ） be a metric measure space satisfying both the upper doubling and the geometrically doubling conditions in the sense of HytSnen. Under this assumption, we prove that θ-type Calderon-Zygmund operators which are bounded on L2（μ） are also bounded from L∞（μ） into RBMO（μ） and from H1,∞at（μ） into L1（μ）.