中强地震前地磁极化异常特征及其与后续地震的关系

基于国家地磁台网中心的地磁秒采样数据,采用地磁垂直强度极化法,计算了2019年1月1日至2020年7月31日全国各地磁台站的极化值,对2019年中国大陆西部(110°E以西)极化异常进行了分析,研究了2020年于田M_S6.4等中强地震前地磁极化异常变化特征及其与后续地震的关系。研究发现:(1)地磁极化异常具有空间成组特征,即空间上多个地区可以同时出现地磁极化异常;地磁极化异常一般被认为是震前震源区发生断层蠕动或岩石破裂导致的电磁辐射,这意味着震前可能会有多个地区同时发生断层蠕动或岩石破裂,这一现象似乎表明有一个"力源"在主导多区域同时发生断层蠕动或岩石破裂。(2)地磁极化异常的后续地震具有成组特征,即一个地区出现极化异常后可能发生多次地震。该现象对日常会商分析具有重要参考意义,即此类异常发生预期地震后可能还会有类似地震的发生。(3)以往的一些研究认为地磁极化异常一般在震前2—3个月出现,但本研究发现极化异常出现后10个月在异常区域仍然会发生地震,这表明电磁辐射异常可能不仅仅是短临异常,还可能具有中期指示意义,即断层蠕动或岩石破裂发生时间可能在震前近1年左右便已开始...     

Transpiration of plantation pinus radiata estimated by the heat pulse method and the bowen ratio

The heat pulse method was used to estimate stand transpiration from a radiata pine (Pinus radiata) plantation in southeastern Australia over a period of four days. The diurnal pattern of sapflow was related to net radiation with a time lag of about 1.5 hours. Despite high soil moisture levels, sapflow did not keep up with evaporative demand in the afternoon. Sapflow estimates of transpiration exceeded estimates for evaporation based on Bowen ratio measurements for all four days of the study.     

Complex image method for calculating electric and magnetic fields produced by an auroral electrojet of finite length

The electromagnetic field due to ionospheric currents has to be known when evaluating space weather effects at the earths surface. Forecasting methods of these effects, which include geomagnetically induced currents in technological systems, are being developed. Such applications are time-critical, so the calculation techniques of the electromagnetic field have to be fast but still accurate. The contribution of secondary sources induced within the earth leads to complicated integral formulas for the field at the earths surface with a time-consuming computation. An approximate method of calculation based on replacing the earth contribution by an image source having mathematically a complex location results in closed-form expressions and in a much faster computation. In this paper we extend the complex image method (CIM) to the case of a more realistic electrojet system consisting of a horizontal line current filament with vertical currents at its ends above a layered earth. To be able to utilize previous CIM results, we prove that the current system can be replaced by a purely horizontal current distribution which is equivalent regarding the total (= primary + induced) magnetic field and the total horizontal electric field at the earths surface. The latter result is new. Numerical calculations demonstrate that CIM is very accurate and several magnitudes faster than the exact conventional approach.     

Determination of depths to centroids of three-dimensional sources of potential-field anomalies with examples from environmental and geologic applications

A method is developed for determining the depth to the centroid (the geometric center) of ‘semi-compact' sources. The method, called the anomaly attenuation rate (AAR) method, involves computing radial averages of AARs with increasing distances from a range of assumed source centers. For well-isolated magnetic anomalies from ‘semi-compact' sources, the theoretical AARs range from 2 (close to the sources) to 3 (in the far-field region); the corresponding theoretical range of AARs for gravity anomalies is 1 to 2. When the estimated source centroid is incorrect, the AARs either exceed or fall short of the theoretical values. The levelling-off of the far-field AARs near their theoretical maximum values indicates the upper (deeper) bound of the centroid location. Similarly, near-field AARs lower than the theoretical minimum indicate the lower (shallower) bound of the centroid location. It is not always possible to determine usable upper and lower bounds of the centroids because the method depends on characteristics of sources/anomalies and the noise level of the data. For the environmental magnetic examples considered in this study, the determined deeper bounds were within 4% of the true centroid-to-observation distance. For the case of the gravity anomaly from the Bloomfield Pluton, Missouri, USA, determination of only the shallower bound of the centroid location (7 km) was possible. This estimate agrees closely with the centroid of a previously determined three-dimensional model of the Bloomfield Pluton. For satellite magnetic anomalies, the method is appropriate only for high-amplitude, near-circular anomalies due to the inherent low signal-to-noise ratio of satellite magnetic anomalies. Model studies indicate that the AAR method is able to place depths within ±20–30 km of actual center locations from a 400-km observation altitude. Thus, the method may be able to discriminate between upper crustal, lower crustal, and mantle magnetic sources. The results from the prominent Kentucky anomaly are relatively well-resolved (centroid depth 30 km below the Earth's surface). For the Kiruna Magsat anomaly, the deleterious effects from neighboring anomalies make a determination difficult (possible depth could be between 20 and 30 km). The centroid depths are deeper for the Kursk anomaly (40–50 km). These depths may indicate that magnetic anomalies from the near-surface Kursk iron formations (a known contributor) and deep crustal magnetic sources could combine to form the Kursk Magsat anomaly.     

南极中山站一名考察队员342天血压、心率、体温的连续观察

对一名中国南极考察队员在南极中山站长期居留期间的血压、心率、体温作了３４２天的连续观察,结果显示：除舒张压无明显变化外,晚间收缩压、心率、体温的总均值有明显升高,与气温、气压和相对湿度无明显关系。极夜期间的收缩压、体温无明显变化。夜间收缩压趋向升高,但未达到显著水平,而舒张压则有非常明显的下降,夜间心率也有明显的增加。极昼期间早晨的血压、心率、体温比夜间有显著升高,但未超出正常生理范围,此时期早晨的收缩压与气压、晚间收缩压与相对湿度、晚间体温与相对湿度均有明显正相关。极夜与极昼时相比早晨的收缩压、体温均无明显变化,只有心率变化显著;极夜期间的舒张压和体温均低于极昼期间的测量值。     

Detection of PPM acoustic Pulse in shallow sea channels

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Determination of the Turbulent Temperature–Humidity Correlation from Scintillometric Measurements

We report on the investigation and successful application of the bichromatic correlation of optical and microwave signals for determining the area-averaged correlation of temperature–humidity fluctuations. The additional technical effort is marginal compared to the common ‘two-wavelength method’, which has (in contrast) the restriction that only two of the three relevant meteorological structure parameters can be deduced. Therefore, in the past, it was often assumed that the turbulent humidity and temperature fluctuations are perfectly positively or negatively correlated. However, as shown in this study, over non-homogeneous terrain when the flow conditions are not ideal, this assumption is questionable. The measurements were analysed statistically, and were compared to in situ measurements of the Bowen ratio Bo and the correlation of temperature–humidity fluctuations using eddy-covariance techniques. The latter is in good agreement to that derived by scintillometry. We found that the correlation is not ±1 but as low as −0.6 for Bo smaller than −2, and up to 0.8 for Bo larger than 1.     

Acclimations of macroalgae as reflected in photosynthetic parameters derived from PAM fluorometry, and possible implications for abundance patterns

The presences of the common macroalgae Ulva sp. and Jania rubens vary between seasons along the Israeli Mediterranean intertidal zone. To reveal some of the potential acclimation mechanisms of these algae, we examined their photosynthetic traits during the year using rapid light curves (RLC) derived from pulse amplitude modulated (PAM) fluorometry. In addition, the relationships between those photosynthetic traits and the relative abundances of the two algae were investigated. Ulva sp. showed high maximal electron transport rates (ETR_max) (49.7–68.8 μmol electrons m⁻² s⁻¹) and onsets of light saturation values (E_k) (75.8–85.6 μmol photons m⁻² s⁻¹) in the winter months of December–February, while low values were found in the summer months of June–July (5.2–20.6 μmol electrons m⁻² s⁻¹ and 6.0–23.7 μmol photons m⁻² s⁻¹, respectively). At noon time (during the highest irradiance of the day), the maximal effective quantum yield (Y₀) did not vary significantly during the year. These results indicate that seasonal irradiance influences the number of reaction centres per thallus area. Both algae showed depressions in Y₀ at noon (23.8% for Ulva sp. and 20.3% for Jania rubens), indicating an efficient non‐photochemical quenching mechanism. A positive correlation between the relative abundance and the photosynthetic parameter Y₀ was found for Jania rubens when Y₀ was sampled in the morning or noon, indicating that growth rate and primary production for this alga can be estimated from RLCs. No such correlation was found for Ulva sp., indicating that, in addition to photosynthetic traits, the relative seasonal abundance of this alga is influenced by other factors such as grazing and/or catastrophic events.     

闪电初始预击穿过程辐射脉冲特征及电流模型

利用2012年青海大通地区高精度闪电三维辐射源定位结果和宽带电场脉冲波形同步数据,基于3种改进的传输线模型和粒子群优化算法,拟合发生在不同距离上不同类型闪电初始预击穿过程的双极性脉冲波形结构,反演初始流光通道内电流波形和特征参数,对比分析3种模型对初始预击穿过程和梯级先导双极性脉冲波形的拟合效果,统计分析4类闪电初始预击穿脉冲的物理特征。结果表明:3种改进的传输线模型均能较好地拟合出双极性脉冲结构,且MTLE模型更合理。负地闪的初始预击穿过程和梯级先导过程呈现出相同的传输特征,即均以梯级形式发展,且拟合物理参量也较为接近。初始流光向上的路径长度大于初始流光向下的路径长度,初始流光向上击穿进入上部正电荷区的路径上中和的总电荷量和总垂直偶极矩远大于初始流光向下的路径上中和的总电荷量和总垂直偶极矩。     

新一代天气雷达地物回波及电磁干扰质控算法业务试运行评估

对雷达基数据质控方法的定量评估是业务应用推广的重要步骤。本文针对中国气象科学研究院研发的地物回波及电磁干扰回波质控算法在"新一代天气雷达建设业务软件系统开发及应用(ROSE)"系统中的业务试应用,使用2014年4—10月系统试运行的10个雷达站的数据,提出了评估方法及评估指标。利用统计和典型个例分析方法对算法进行了初步业务试运行的效果评估,验证了算法的可靠性,提出了适用范围及改进措施。结果表明:该方法对地物回波的识别成功率为92.29%,但存在漏判和误判。参与评估的CB雷达径向速度资料质量高,识别效果好;SA和SB雷达的识别效果受到了观测模式等导致径向速度资料质量变差的影响。电磁干扰回波的识别成功率为94.39%,能有效识别小于5个径向的窄条幅状干扰回波,但仍需改进算法完成对麻点状、螺旋状和大面积径向干扰回波的自动识别。对雷达资料的定量应用,需采取质控,而预报员的实时观测可根据情况进行选择性质控。