影响夏季北极航道航行的近地面气象要素时空变化特征分析

本文利用ERA5再分析数据和我国北极科学考察期间获取的走航气象观测数据,分析了夏季影响船舶通航北极航道的关键近地面气象要素的时空变化特征。结果表明,7–8月的天气条件最适宜船舶在北极航道航行,9月低温、大风和大浪天气显著增多,对船舶航行影响较大,10月的天气更加恶劣,对船舶航行的挑战更大。低温天气主要出现在各航道的中段,大风和大浪天气集中在航道两端的海域。除北极中心区和10月的挪威海和巴伦支海以外,其余时间的海域出现大风和大浪天气的概率以增加趋势为主,但具有较大的年际变化。根据现有北极航道气象观测数据分析发现,东北航道能见度最差,西北航道能见度最好,中央航道居中。

钻孔瞬变电磁法扫描探测磁芯线圈激励电磁场响应特征

瞬变电磁测井一般采用超小线圈作为发射装置,由于激励产生的瞬变电磁场强度较低,仅能进行钻孔孔壁岩层探测,无法实现钻孔外围径向远距离探测及地质异常体精确定位。基于全空间瞬变电磁场相关理论,提出钻孔瞬变电磁法(BTEM)扫描探测方法,利用磁芯线圈激励电磁场,增强发射磁矩,提高钻孔瞬变电磁法的径向探测距离。同时,通过灵活调整线圈方向,对钻孔孔壁进行360°扫描,实现钻孔径向方向全方位探测,提高钻孔瞬变电磁法对含水地质体的空间分辨率和定位精度。建立钻孔全空间三维地质-地球物理模型,提出优化的网格剖分策略,采用特殊网格结构对钻孔中磁芯线圈进行网格加密及规范化,提高数值模拟精度。采用有限单元法分别计算均匀介质条件下钻孔瞬变电磁法磁芯激励电磁场响应以及含有低阻地质异常体时钻孔瞬变电磁法不同装置探测的瞬变电磁场响应,分析了共面偶极装置及共轴偶极装置以及不同几何参数对应的瞬变电磁场响应特征,采用全空间全区视电阻率计算及时深转换算法进行全空间电阻率成像。研究表明,在钻孔瞬变电磁法超小线圈中加入磁芯可以显著增强电磁场强度,并且增强的幅度与磁芯的直径和长度成正比,相比较而言,增大磁芯长度对电磁场响应的增强作用更为显著;钻孔全空间磁芯线圈激励时探测结果可以较好地反映钻孔径向外围岩层中低阻地质体引起的瞬变电磁场异常,共面偶极装置和共轴偶极装置均可以获得较为理想的探测效果,全空间电阻率成像结果分辨率较高,相比较而言,共面偶极装置得到的异常幅度更大,并且对异常体中心的定位更为准确,而共轴偶极装置对异常体整体形态和边界的刻画更为准确。

Third-order nonlinear optical properties of graphene composites:A review

Graphene has excellent thirdorder nonlinear optical(NLO)properties due to its unique electronic band structure and wideband gap tunability.This paper focuses on the research progress of graphene and its composite materials in nonlinear optics in recent years.In this review,recent results on graphene(or graphene oxide)-metal nanoparticles(G-MNPs),graphene-metal-oxide nanoparticles(G-MONPs),graphene-metal sulfide nanoparticles(G-MSNPs),and graphene-organic molecular composites(G-OM)have been discussed.In addition,the enhancement mechanism of nonlinear absorption(NLA)and optical limiting(OL)have also been covered.

Evaluation of reanalysis and satellite-based sea surface winds using in situ measurements from Chinese Antarctic Expeditions

Sea surface winds from reanalysis （NCEP-2 and ERA-40 datasets） and satellite-based products （QuikSCAT and NCDC blended sea winds） are evaluated using in situ ship measurements from the Chinese National Antarctic Research Expeditions （CH1NAREs） from 1989 through 2006, with emphasis on the Southern Ocean （south of 45°S）. Compared with ship observations, the reanalysis winds have a positive mean bias （0.32 m·s-1 for NCEP-2 and 0.13 m·s-1 for ERA-40）, and this bias is more pronounced in the Southern Ocean （0.57 m·s-1 and 0.45 m·s-1, respectively）. However, mean biases are negative in the tropics and subtropics. The satellite-based winds also show positive mean biases, larger than those of the reanalysis data. All four wind products overestimate ship wind speed for weak winds （〈4 m·s-1） but underestimate for strong winds （〉10 m·s-1）. Differences between the reanalysis and satellite winds are examined to identify regions with large discrepancies.

Meteorological observations and weather forecasting services of the CHINARE

By 2018, China had conducted 34 scientific explorations in Antarctica spearheaded by the Chinese National Antarctic Research Expedition(CHINARE). Since the first CHINARE over 30 years ago, considerable work has been undertaken to promote the development of techniques for the observation of surface and upper-air meteorological elements, and satellite image and data reception systems at Chinese Antarctic stations and onboard Chinese icebreakers have played critical roles in this endeavor. The upgrade of in situ and remote sensing measurement methods and the improvement of weather forecasting skill have enabled forecasters to achieve reliable on-site weather forecasting for the CHINARE. Nowadays, the routing of icebreakers, navigation of aircraft, and activities at Chinese Antarctic stations all benefit from the accurate weather forecasting service. In this paper, a review of the conventional meteorological measurement and operational weather forecasting services of the CHINARE is presented.

Chaos-induced resistivity of collisionless magnetic reconnection in the presence of a guide field

One of the most puzzling problems in astrophysics is to understand the anomalous resistivity in collisionless magnetic reconnection that is believed extensively to be responsible for the energy re- lease in various eruptive phenomena. The magnetic null point in the reconnecting current sheet, acting as a scattering center, can lead to chaotic motions of particles in the current sheet, which is one of the possible mechanisms for anomalous resistivity and is called chaos-induced resistivity. In many interest- ing cases, however, instead of the magnetic null point, there is a nonzero magnetic field perpendicular to the merging field lines, usually called the guide field, whose effect on chaos-induced resistivity has been an open problem. By use of the test particle simulation method and statistical analysis, we investigate chaos-induced resistivity in the presence of a constant guide field. The characteristics of particle motion in the reconnecting region, in particular, the chaotic behavior of particle orbits and evolving statistical features, are analyzed. The results show that as the guide field increases, the radius of the chaos region increases and the Lyapunov index decreases. However, the effective collision frequency, and hence the chaos-induced resistivity, reach their peak values when the guide field approaches half of the character- istic strength of the reconnection magnetic field. The presence of a guide field can significantly influence the chaos of the particle orbits and hence the chaos-induced resistivity in the reconnection sheet, which decides the collisionless reconnection rate. The present result is helpful for us to understand the micro- physics of anomalous resistivity in collisionless reconnection with a guide field.

Features of visibility variation at Great Wall Station,Antarctica

The variation of visibility at Great Wall Station （GWS） was analyzed using manual observational data for the period of 1986 to 2012. Results show that the frequencies of occurrence of high （≥ 10 km） and low visibility （0-1 km） are 61.0% and 8.0%, respectively. Visibility at GWS shows an evident seasonal variation： The highest visibility between November and March, and the lowest visibility from June to October. Sea fog and precipitation are the main factors for low visibility during summer, whereas frequent adverse weather, such as falling snow, blowing snow, or blizzards, are responsible for low visibility in winter. The frequency of occurrence of low visibility has decreased significantly from 1986 to 2012. Conversely, the frequency of occurrence of high visibility has shown a significant increasing trend, especially during winter. The decreasing tendencies of fog, blowing snow, and snowfall have contributed to the increasing trend of high visibility during winter. Visibility at GWS exhibits significant synoptic-scale （2.1 to 8.3 d）, annual, and inter-annual periods （2 a, 4.1 a, and 6.9 a to 8.2 a）, among which the most significant period is 4.1 a. The visibility observed during 2012 indicates that instrumental observation can be applied in the continuous monitoring of visibility at GWS.

Relationship between climatic factors and the flea index of two plague hosts in Xilingol League,Inner Mongolia Autonomous Region

Climatic factors are closely associated with the occurrence of vector‐borne diseases,and they also influence the distribution of vectors.The occurrence of plague is closely related to the population dynamics of fleas and their host animals,as well as climatic conditions.This study focused on Xilingol League,utilizing climatic and flea index data from 2012 to 2021.Spearman correlation and"Boruta"importance analysis were conducted to screen for climatic variables.A generalized additive model(GAM)was employed to investigate the influence of climatic factors and rodent density on the flea index.GAM analysis revealed distinct trends in flea index among different rodent hosts.For Meriones unguiculatus,the flea index declined with increased density and with higher humidity,yet rose with greater lagged sunshine duration.For Spermophilus dauricus,an initial increase in flea index with density was observed,followed by a decrease,and a rise in the index was noted when ground temperatures were low.This study reveals the nonlinear interactions and lag effects among climatic factors,density,and flea index.Climatic factors and density variably influence the flea index of two Yersinia pestis hosts.This research advances the prediction and early warning efforts for plague control,providing a theoretical basis for rodent and flea eradication strategies.

Relationships Between Meteorological Factors and Mongolian Gerbils and Its Flea Burdens—Xilingol League,Inner Mongolia Autonomous Region,China,2012–2021

Introduction:Plague is a significant global infectious disease,its spread is linked to host and flea populations.Meteorological conditions can impact flea populations and host densities,hence influencing plague outbreaks.Investigating the connection between meteorological factors,flea populations,and rodent densities in Inner Mongolia’s natural plague foci can aid in predicting and managing plague outbreaks.Methods:Monthly data on flea index,rodent density,meteorological factors,and normalized difference vegetation index(NDVI)were collected for the study area.Generalized additive modeling(GAM)was used to analyze the non-linear and lag effects of meteorological factors on flea index and rodent density.Structural equation modeling(SEM)was employed to investigate the relationships among meteorological factors,NDVI,flea index,and rodent density.Results:GAM analysis revealed that temperature,precipitation,relative humidity,and NDVI had significant linear,non-linear,and time-lagged impacts on the density of Mongolian gerbils and the flea index.SEM analysis indicated that meteorological factors could directly influence the density and flea index of Mongolian gerbils,or indirectly impact NDVI,subsequently influencing gerbil density and the flea index.Conclusions:Meteorological factors primarily influence gerbil density and flea index indirectly by affecting NDVI and the relationship between flea index and gerbil density.This study offers additional support for the significance of meteorological factors and NDVI in influencing the vector-rodent system,offering valuable insights for predicting and managing plague outbreaks.

Spatiotemporal Characteristics and Risk Zonation Analysis of Rodents and Surface-Parasitic Fleas—Inner Mongolia Autonomous Region,China,2013–2021

Background:Recent plague cases in Inner Mongolia prompted research on rodents and fleas.This study aimed to describe the spatiotemporal characteristics of parasitic fleas on predominant rodent species and identify plague risk areas.Methods:We assembled monitoring data from the National Plague Surveillance System for 12 regions in Inner Mongolia from 2013 to 2021.We performed descriptive statistics using relative indices,analyzed interannual flea index trends using the Mann-Kendall test,compared spatiotemporal characteristics using the Kruskal-Wallis H test and Dunn’s test,and delineated plague risk areas based on cluster analysis.Results:In total,134,181 rodents from 28 species were captured,with an average parasitism rate of 31.46%.A total of 143,958 fleas were collected,resulting in a total average flea index of 1.07.The primary rodent species were the Mongolian gerbil(Meriones unguiculatus)and Daurian ground squirrel(Spermophilus dauricus).The flea index showed a decreasing trend(Sen’s slope=−0.06,P<0.05).Meriones unguiculatus had two peaks(May and October),with a delay of one to two months after peak flea parasitism.Spermophilus dauricus had a peak in May but two flea parasitism peaks(March and November).Meriones unguiculatus and Spermophilus dauricus flea indices varied significantly across regions(H=25.75,P<0.001;H=29.88,P<0.001).Erdos City and Xilingol League had the highest flea indices for each species,respectively.Cluster analysis divided the 12 regions into three risk zones.Conclusions:The two predominant rodent species in Inner Mongolia have demonstrated an overall decline in flea index over time.The hotspots for flea index are primarily concentrated in Erdos and Xilingol League.Strengthening regional cooperation is crucial for tailored plague prevention and control measures.