High-resolution simulation and analysis of the mature structure of a polar low over the sea of Japan on 21 January 1997

This paper presents a high-resolution simulation of a remarkable polar low observed over the Sea of Japan on 21 January 1997 by using a 5-km mesh non-hydrostatic model MRI-NHM (Meteorological Research Institute Non-Hydrostatic Model). A 24-hour simulation starting from 0000 UTC 21 January 1997 successfully reproduced the observed features of the polar low such as the wrapping of western part of an initial E W orientation vortex, the spiral-shaped bands, the cloud-free “eye“, and the warm core structure at its mature stage. The “eye“ of the simulated polar low was relatively dry, and was associated with a strong downdraft. A thermodynamic budget analysis indicates that the “warm core“ in the “eye“ region was mainly caused by the adiabatic warming associated with the downdraft. The relationship among the condensational diabatic heating, the vertical velocity, the convergence of the moisture flux, and the circulation averaged within a 50 km~50 km square area around the polar low center shows that they form a positive feedback loop, and this loop is not inconsistent with the CISK (Conditional Instability of the Second Kind) mechanism during the developing stage of the polar low.     

Analysis and high-resolution modeling of a dense sea fog event over the Yellow Sea

A ubiquitous feature of the Yellow Sea (YS) is the frequent occurrence of the sea fog in spring and summer season. An extremely dense sea fog event was observed around the Shandong Peninsula in the morning of 11 April 2004. This fog patch, with a spatial scale of several hundreds kilometers and lasted about 20 h, reduced the horizontal visibility to be less than 20 m in some locations, and caused a series of traffic collisions and 12 injuries on the coastal stretch of a major highway. In this paper, almost all available observational data, including Geostationary Operational Environmental Satellite (GOES)-9 visible satellite imagery, objectively reanalyzed data of final run analysis (FNL) issued by the National Center for Environmental Prediction (NCEP) and the sounding data of Qingdao and Dalian, as well as the latest 4.4 version of Regional Atmospheric Modeling System (RAMS) model, were employed to investigate this sea fog case. Its evolutionary process and the environmental conditions that led to the fog formation were examined by using GOES-9 visible satellite imagery and sounding observations. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling of 4 km × 4 km was designed. The modeling was initialized and validated by FNL data. A 30-h modeling that started from 18 UTC 10 April 2004 reproduced the main characteristics of this fog event. The simulated lower horizontal visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role for the fog formation.     

Application of integrated geophysical interpretation on accumulation body

Integrated geophysical interpretation is a method of combinating different geophysics prospecting methods based on different physical properties of accumulation. As different geophysical methods own different interpretations and varying detection accuracies, the key issue becomes how to integrate the results of several geophysical methods to corrently carry out a comprehensive explanation. Based on different geophysical results, the authors proposed an integrated geophysical explanation method and successfully applied it in practical engineering problems.     

基于“一街一站”的深圳市PM2.5时空特征及排名通报作用研究

深圳市于2018年6月建成了全国首个街道空气监测网络“一街一站”,并对全市74个街道进行月均PM_2.5浓度排名,向公众通报空气质量排名倒数十位的街道,以落实基层治理大气污染的责任。本研究基于深圳市街道空气监测网络的数据,分析了深圳市PM_2.5浓度的时空特征,使用双重差分模型检验空气质量排名通报是否能发挥环保部门所期待的效果,进一步促使PM_2.5浓度排名靠后的街道改善其空气质量。结果表明：① 基于街道空气监测的深圳市年均PM_2.5浓度为22.4 μg/m³,月均浓度最低值出现在7月,最高值出现在1月,与国家站监测结果之间无显著性差异。② 深圳市街道的PM_2.5浓度具有较高的空间集聚性,高值主要聚集在西北部,低值主要聚集在中南部,而国家监测站难以准确表征深圳市PM_2.5浓度空间分布特征。③ 考虑了个体和时间固定效应的双重差分模型分析结果表明,对深圳市月均PM_2.5浓度较高、空气质量排名靠后的街道进行通报,其随后1~2个月的PM_2.5浓度仍受该月污染的持续性影响,而通报行为无显著性影响;到随后第3个月,该月污染的持续性影响下降到较小的程度,此时通报行为对PM_2.5浓度呈显著降低作用,且影响程度大于污染的持续性影响。     

Seismic data denoising via shearlet transform and data‐driven tight frame

We propose a sort of double sparsity dictionary (DSD) to deal with random noise of seismic exploration, which consists of shearlet transform and data‐driven tight frame (DDTF). We train the DDTF dictionary in the domain of shearlet transform to improve the robustness of the dictionary. Furthermore, the function of hard‐thresholding is applied to find dictionary coefficients and cut small shearlet coefficients. Finally, we verified the reliability of the proposed approach by a synthetic data denoising example.     

Study of numerical simulation on dual-frequency IP method with FEM

Using the finite element method and Cole-Cole model for dual-frequency IP method to research numerical simulation, the authors introduced the fundamental principle of the dual-frequency IP method and the boundary value problem and variational equations, then replaced the complex resistivity of the model with the Cole-Cole model's parameters under ignoring the EM effect. Through solving the last linear equations, electric potentials of all the model's points were obtained. With changing model's parameters, the authors got different curves of the Fs and phases. According to the results of the simulation, the algorithm is proved to be correct and adaptable.     

强干扰区含噪电磁场的时空分布特征

噪声是限制电磁勘探应用效果的瓶颈之一,明确含噪电磁场数据的特征是强干扰区开展电磁法研究的首要问题。本文依据庐枞矿集区的干扰源调查及大量实测数据,通过对比不同条件、多种类型的电磁场数据,归纳了强干扰区电磁噪声源的主要类型,并总结了含噪电磁场数据的时间域、频率域及空间分布特征。结果表明：强干扰区噪声源可按多种形式进行分类;含噪电磁场数据在时间域常具有显著的形态、振幅、结构及相关性特征;时频谱常表现出不同的时间分段及频率分带特征;频域响应常呈分频带畸变特征,以"近源"型畸变最为典型;噪声影响的空间分布与场源类型、观测方位及地下结构等因素相关。     

Three-Dimensional Structure and Low-Level Features of the North Pacific Storm Track from 1999 to 2005

A storm track is a region in which synoptic eddy activities are statistically most prevalent and intense. At daily weather charts, it roughly corresponds to the mean trajectories of cyclones and anticyclones. In this paper, the recent QuikSCAT （Quick Scatterometer） satellite sea winds data with a 0.5°×0.5° horizontal resolution, and the NCEP （National Centers for Environmental Prediction） 10-m height Gaussian grid wind data and pressure-level reanalysis data, are employed to document the spatial structure of the North Pacific storm track in winter （January） and summer （July） from 1999 to 2005. The results show that in winter the North Pacific storm track is stronger, and is located in lower latitudes with a distinct zonal distribution. In summer, it is weaker, and is located in higher latitudes. Based on the horizontal distributions of geopotential height variance at various levels, three-dimensional schematic diagrams of the North Pacific storm track in winter and summer are extracted and presented. Analyses of the QuikSCAT wind data indicate that this dataset can depict the low-level storm track features in detail. The double storm tracks over the Southern Oceans found by Nakamura and Shimpo are confirmed. More significantly, two new pairs of low-level storm tracks over the North Pacific and the North Atlantic are identified by using this high-resolution dataset. The pair over the North Pacific is focused in this paper, and is named as the ＂subtropical storm track＂ and the ＂subpolar storm track＂, respectively. Moreover, statistical analyses of cyclone and anticyclone trajectories in the winters of 1999 to 2005 reveal as well the existence of the low-level double storm tracks over the North Pacific.     

北太平洋风暴轴的三维空间结构

文中利用最新的0.5°×0.5°分辨率QuikSCAT(QuikBird Satellite Microwave Scatterometer Sea Winds Data)海面风场资料、NCEP(National Center for Environmental Prediction)的10 m高度风场资料和全球客观再分析资料,对1999-2005年冬季(1月)和夏季(7月)北太平洋风暴轴的三维空间结构进行了分析,发现冬季北太平洋风暴轴的强度较强,呈明显的纬向拉伸带状分布特征,位置偏南.夏季北太平洋风暴轴的强度较弱,位置偏北.根据不同高度上位势高度方差的水平分布特征,绘制了北太平洋风暴轴的三维结构示意图.利用高分辨率QuikSCAT资料对风暴轴特征的刻画更为细致,不但验证了Nakamu-ra在南大洋发现的双风暴轴现象,而且还发现在北太平洋和北大西洋下层分别存在"副热带风暴轴"和"副极地风暴轴"两个风暴轴.对1999-2005年冬季北太平洋气旋和反气旋的移动路径进行的统计分析,为北太平洋"双风暴轴"的存在提供了强有力的证据.     

资源三号卫星DEM数据与全球开放DEM数据的误差对比

全球开放DEM数据为数字地形分析提供了重要数据源。与已有的全球开放DEM数据相比,资源三号卫星具有更高的空间分辨率、更大的覆盖范围和更好的现势性。将资源三号卫星生成的DEM数据与全球开放DEM数据进行误差对比则为基于资源三号卫星的全球DEM数据研制提供科学依据。本文以山西省中部太原市为研究区,基于高精度激光点云数据生成DEM为参考数据,对资源三号卫星影像生成的DEM数据与全球典型的开放DEM数据(AW3D30、SRTM1和ASTER GDEM)的误差进行了对比分析,并获得了其在不同坡度等级下绝对误差与相对误差的平均值、平均绝对值、均方根值和标准偏差值。研究结果表明:①4种DEM数据的误差分布均具有较好的对称性。同时,平均误差接近于0 m,SRTM1和ASTER GDEM数据更是如此。因此均方根误差值与标准偏差值近似一致;②资源三号DEM具有最高的精度,误差最小(均方根误差4.6 m)。其次为AW3D30数据(均方根误差5.6 m)和SRTM1数据(均方根误差8.8 m)。ASTER GDEM数据误差最大(均方根误差12.6 m),精度最差;③资源三号DEM、SRTM1和ASTER GDEM数据的误差均随坡度的变大而增大,而AW3D30数据误差随着坡度增加呈现先减小后增大的趋势。总体上,与其他3种DEM数据相比,资源三号DEM在所有坡度范围均具有最小的误差值。