高阶seislet变换及其在随机噪声消除中的应用

Seislet变换是一种小波类数学变换方法,主要根据不同小波级数上地震同相轴的局部倾角的不同来分析数据.一般意义上,测线方向上的离散小波变换（DWT）是一种特殊的零局部地震倾角的seislet变换.早期的工作基于低阶版本的离散小波变换来构建seislet变换,在本文中,通过使用Cohen-Daubechies-Feauveau (CDF) 9/7双正交小波变换（常用于JPEG2000压缩标准）作为框架,扩展高阶seislet变换方法.通过分析理论模型和实际数据的处理结果,并对比傅里叶变换、离散小波变换和低阶seislet变换,高阶seislet变换可以为地震数据提供更好的压缩比.因此更加适用于地震数据去噪处理.     

Estimation of Explosion Energy Yield at Chernobyl NPP Accident

The value of the ¹³³Xe/^133mXe isometric activity ratio for the stationary regime of reactor work is about 35, and that for an instant fission (explosion) is about 11, which allowed estimation of the nuclear component of the instant (explosion) energy release during the NPP accident. Atmospheric xenon samples were taken at the trajectory of accident product transfers (in the Cherepovetz area); these samples were measured by a gamma spectrometer, and the ¹³³Xe/^133mXe ratio was determined as an average value of 22.4. For estimations a mathematic model was elaborated considering both the value of instant released energy and the schedule of reactor power change before the accident, as well as different fractionation conditions on the isobaric chain. Comparison of estimated results with the experimental data showed the value of the instant specific energy release in the Chernobyl NPP accident to be 2·10⁵–2·10⁶ J/Wt or 6·10¹⁴–6·10¹⁵ J (100–1,000 kt). This result is matched up to a total reactor power of 3,200 MWt. However this estimate is not comparable with the actual explosion scale estimated as 10t TNT. This suggests a local character of the instant nuclear energy release and makes it possible to estimate the mass of fuel involved in this explosion process to be from 0.01 to 0.1% of total quantity.     

北极圈数据库及为何需要

Many factors, such the great changes of temperature, which will be expected at the high latitudes, increased pressure from humans to extract the natural resources in cold regions, seriously affect the cold environment. Many meetings have been held about the classification of cold soils, ideas and concepts of cold soils. These facilitate the need for developing a database of soils of the circumpolar region. The database can help offering information for potential problems in cold regions and for selecting the best areas for placement of new road and towns.     

July 2020 heavy rainfall in Japan: effect of real-time river discharge on ocean circulation based on a coupled river-ocean model

Ocean Dynamics - In July 2020, a stationary atmospheric front over Japan caused persistent, nearly continuous rain for most of the month that resulted in new historical highest rainfall records in...     

Data‐driven time–frequency analysis of seismic data using non‐stationary Prony method

Empirical mode decomposition aims to decompose the input signal into a small number of components named intrinsic mode functions with slowly varying amplitudes and frequencies. In spite of its simplicity and usefulness, however, empirical mode decomposition lacks solid mathematical foundation. In this paper, we describe a method to extract the intrinsic mode functions of the input signal using non‐stationary Prony method. The proposed method captures the philosophy of the empirical mode decomposition but uses a different method to compute the intrinsic mode functions. Having the intrinsic mode functions obtained, we then compute the spectrum of the input signal using Hilbert transform. Synthetic and field data validate that the proposed method can correctly compute the spectrum of the input signal and could be used in seismic data analysis to facilitate interpretation.     

Developing configuration of WRF model for long-term high-resolution wind wave hindcast over the North Atlantic with WAVEWATCH III

The spatial resolution of wind forcing fields is critical for modeling ocean surface waves. We analyze here the performance of the non-hydrostatic numerical weather prediction system WRF-ARW (Weather Research and Forecasting) run with a 14-km resolution for hindcasting wind waves in the North Atlantic. The regional atmospheric model was run in the domain from 20° N to 70° N in the North Atlantic and was forced with ERA-Interim reanalysis as initial and boundary conditions in a spectral nudging mode. Here, we present the analysis of the impact of spectral nudging formulation (cutoff wavelengths and depth through which full weighting from reanalysis data is applied) onto the performance of the modeled 10-m wind speed and wind wave fields for 1 year (2010). For modeling waves, we use the third-generation spectral wave model WAVEWATCH III. The sensitivity of the atmospheric and wave models to the spectral nudging formulation is investigated via the comparison with reanalysis and observational data. The results reveal strong and persistent agreement with reanalysis data during all seasons within the year with well-simulated annual cycle and regional patterns independently of the nudging parameters that were tested. Thus, the proposed formulation of the nudging provides a reliable framework for future long-term experiments aiming at hindcasting climate variability in the North Atlantic wave field. At the same time, dynamical downscaling allows for simulation of higher waves in coastal regions, specifically near the Greenland east coast likely due to a better representation of the mesoscale atmospheric dynamics in this area.     

Pattern-guided dip estimation with plane-wave destruction filters

We propose to use pattern-guided dip estimation to mitigate aliasing problem that possibly exists in structure-oriented data processing. A straightforward and effective approach of generating pattern-guided dip is presented, which generally involves three rounds of standard dip estimation with plane-wave destruction filters. The first use of plane-wave destruction filter is for generating a mask operator distinguishing aliased and non-aliased data, based on measuring the uncertainty of the first dip estimation. The second plane-wave destruction filter uses the aliasing-free portions of the input data, and the dip in the aliasing-affected area is automatically padded with the ‘pattern’ dip by smoothing regularization. The result of the second plane-wave destruction filter is used as the initial dip for the inversion of the last-pass plane-wave destruction filter, which produces a pattern-guided dip. For some specific applications, the mask operator can be easily generated through other methods, and we can skip the first dip estimation. Two numerical examples, related to picking information using predictive painting and structure-oriented interpolation, respectively, demonstrate that our pattern-guided dip can effectively mitigate the aliasing problem in structure-oriented data processing.     

Understanding how physical-biological coupling influences harmful algal blooms,low oxygen and fish kills in the Sea of Oman and the Western Arabian Sea

In the last decade, green Noctiluca scintillans with its symbiont and other dinoflagellates such as Cochlodinium polykrikoides, Prorocentrum micans and Scrippsiella trochoidea have become the dominant HABs, partially replacing the previously dominant diatoms and red Noctiluca scintillans, especially during the northeast monsoon. Fish kills in the Sea of Oman are linked to a slow seasonal decline in oxygen concentration from January to November, probably due to the decomposition of a series of algal blooms and the deep, low oxygen waters periodically impinging the Omani shelf. In the western Arabian Sea, cyclonic eddies upwell low oxygen, nutrient-rich water and the subsequent algal bloom decays and lowers the oxygen further and leads to fish kills. Warming of the surface waters by 1.2 °C over the last 5 decades has increased stratification and resulted in a shoaling of the oxycline. This has increased the probability and frequency of upwelling low oxygen water and subsequent fish kills.     

Representation of light pressure resultant force and moment as a tensor series

In this article, we address the problem of the determination of light pressure upon space structures with a complex geometric shape. For each surface element, we enforce a condition that it can interact with light only from its front side, a condition represented in the form of series of Chebyshev polynomials of the first kind. This Chebyshev expansion enables the use of a series of tensors of increasing rank for determination of the force and moment acting on the sail. We obtain expressions for the determination of light pressure on space structures of complex geometry, taking into account self-shadowing and reflections within the structure. We also give the expressions for tensor parametrization using the specularity coefficient in case of specular -diffuse reflection. For these expressions, we calculated the principal moment and force upon two-sided flat solar sail, spherical and cylindrical bodies, and approximated light pressure upon the proposed space-based observatory Millimetron. The proposed expressions can be used in the ballistic analysis of solar sails and other space objects significantly affected by radiation pressure. Also, these results can be used to analyze the dynamics of large-scale space structures around their center of gravity under light pressure.     

Estimate of the Upper Limit on Hot Plasma Differential Emission Measure (DEM) in Non-Flaring Active Regions and Nanoflare Frequency Based on the Mg <Emphasis Type="SmallCaps">xii</Emphasis> Spectroheliograph Data from CORONAS-F/SPIRIT

Nanoflare-heating theory predicts steady hot-plasma emission in non-flaring active regions. It is hard to find this emission with conventional non-monochromatic imagers (such as the Atmospheric Imaging Assembly or the X-Ray Telescope), because their images contain a cool-temperature background. In this work, we search for hot plasma in non-flaring active regions using the Mg?xii spectroheliograph onboard the Complex Orbital Observations Near-Earth of Activity on the Sun (CORONAS)-F/SPectroheliographIc X-ray Imaging Telescope (SPIRIT). This instrument acquired monochromatic images of the solar corona in the Mg?xii 8.42 Å line, which emits only at temperatures higher than 4 MK. The Mg?xii images only contain the signal from hot plasma, without any low-temperature background. We studied the hot plasma in active regions using SPIRIT data from 18?–?28 February 2002. During this period, the Mg?xii spectroheliograph worked with a 105-second cadence almost without data gaps. Hot plasma was observed only in the flaring active regions. We did not observe any hot plasma in non-flaring active regions. The hot-plasma column emission measure in the non-flaring active region is not expected to exceed \(3 \times10^{24}\) cm^?5. The hot differential emission measure is lower than 0.01% of the DEM of the main temperature component. The absence of Mg?xii emission in the non-flaring active regions can be explained by weak and frequent nanoflares (with a delay of less than 500 seconds) or by very short and intense nanoflares that lead to non-equilibrium ionization.