基于飞机真实轨迹的一次层状云催化的增雨效果及其作用机制的模拟研究

层状云降水效率通常较低,但却具有较高的云水资源开发潜力,是人工增雨作业的重要对象。随着中国南方地区生态改善、水库增蓄、抗旱等社会需求的增加,针对这些地区降水云系的人工增雨研究显得愈发重要。使用三维中尺度冷云催化模式,对2018年10月21日湖北省一次层状云飞机人工增雨作业过程进行了数值模拟研究,并将模拟结果与卫星、降水和机载云物理观测数据进行了对比。模式合理地模拟出了云和降水的主要宏、微观特征,观测和模拟结果均显示作业云区具有较好的冷云催化条件,在此基础上,按照实际作业中的飞机播撒轨迹,完整地模拟了此次催化作业过程。对数值模拟结果的分析表明:凝结冻结核化和凝华核化是碘化银催化剂的主要核化方式;90%以上碘化银粒子的局地活化比为0.01%—2%,平均活化比为0.07%—0.27%;云系降水是由冷云降水和暖云降水两种机制共同作用的结果,催化作业使两种降水机制均有增强,增雨效果明显;催化后4 h,整个评估区内的累计净增雨量为2.12×108 kg,局地增雨率为?51.1%—306.7%,区域平均增雨率为8.1%;催化作业也使部分地区出现减雨,主要是由于催化过程中的潜热释放引起过冷层动力场扰动,一部分云区的上升气流减弱,从而导致降水粒子的成长减弱,地面出现减雨;在过冷云区,碘化银核化使冰晶浓度升高,导致冰晶-雪、雪-霰的转化过程增强,雪、霰粒子总量增加,更多的雪、霰粒子从冷区落入暖区,在暖区上层产生更多的大雨滴,从而使暖区的云雨粒子碰并过程增强,最终地面降水增加,这是此次催化作业导致增雨的主要微物理链条。      

The Nucleus Deposit: Superposed Au–Ag–Bi–Cu Mineralization Systems at Freegold Mountain,Yukon, Canada

In this paper we present titanite U–Pb (both single crystal CA ID‐TIMS and in situ LA ICP‐MS) data, coupled with ore and gangue mineralogy and geochemical (both lithogeochemistry and microanalysis) data from the Nucleus Au–Ag–Bi–Cu deposit, in the Yukon (Canada) portion of the Tintina Au province. Arsenic‐bearing Au–Ag–Bi–Cu mineralization at Nucleus consists of two distinct styles of mineralization including: (i) reduced Au skarn and sulfide replacement; and (ii) a relatively shallow‐emplaced (as supported by textures and temperature of formation), vein‐controlled mineralization occurring mainly as veins and veinlets of various shapes (sheeted, single, stockworks, and crustiform), breccias, and disseminations. Whereas Au, Bi, and Cu mineralization from skarn is associated with hydrous retrograde alteration phases (actinolite, ferro‐actinolite, hastingsite, cannilloite, and hornblende), numerous alteration types are associated with the vein‐controlled style of mineralization and these include: biotite, phyllic, argillic, propylitic, carbonate, and quartz (silicification) alterations. The mineralization–alteration processes took place over a wide temperature range that is bracketed between 340 and 568°C, as indicated by chlorite and arsenopyrite geothermometers. The Au‐rich Nucleus deposit is characterized by anomalously high content of As and Bi (as much as 1 %), and whereas Au moderately correlates with Bi (r = 0.40) in the skarn mineralization style (where native Au is spatially associated with native Bi and Bi‐bearing sulfides), the two elements correlate poorly (r = 0.14) in the vein‐controlled type, in which native Bi‐ and Bi‐sulfide‐bearing veins are locally observed. Sphalerite from the vein‐controlled mineralized type is Fe‐rich (9.92–10.54 mol % FeS) indicative of low sulfidation conditions, as well as high temperature, with the latter further supported by arsenopyrite geothermometry (up to 491°C), low Ag content (3–7 wt.%) in Au, and the high gold fineness (926–964). Whereas molybdenite Re–Os ages from quartz‐molybdenite veins range from 75.8 to 76.2 ± 0.3 Ma, titanite from the skarn type mineralization recorded CA ID‐TIMS and LA ICP‐MS U–Pb ages of 182.6 ± 2.4 Ma and 191.0 ± 1.5 Ma, respectively, thus precluding any genetic link between the two spatially associated styles of mineralization from the Nucleus deposit area. The Au–Ag–Bi–Cu Nucleus deposit is therefore regarded as a superposed system in which two mineralization types, without any petrogenetic relationship, overlapped, possibly with remobilization of early‐formed mineralization.     

一次降雹过程的AgI系列催化模拟研究

云数值模拟是研究降雹过程和人工防雹试验的重要手段。利用三维冰雹云AgI催化模式,对北京1996年6月10日的一次降雹过程进行AgI不同催化高度、催化剂量和催化时间的系列催化模拟试验,并优选催化方案,为外场防雹设计和作业提供依据。在催化系列模拟中发现,不同催化高度的催化剂均在上升到-5℃高度后开始核化。在2.1~4.9 km高度范围内催化,AgI成核率比较高,防雹效果较好。核化的人工冰晶有效弥补了该高度上自然冰晶的不足。小剂量催化,可在减雹的同时增加部分降雨量,而大剂量催化,在减雹的同时会减少降雨。在催化时间、剂量和高度的系列催化试验中得出,采用在模拟的第15分钟在5 km高度附近播撒AgI,连续4次以5×106 kg-1的催化剂量进行催化,催化效果较好,可减少降雹量约60%,同时可避免降雨量的大幅减少。     

2014年春季华北两次降水过程的人工增雨催化数值模拟研究

在WRF中尺度模式中耦合了中国气象科学研究院发展的CAMS（Chinese Academy of Meteorological Sciences）云微物理方案,并在CAMS方案中增加了直接播撒冰晶（S1方案）和播撒碘化银催化剂（S2方案）两种云催化方案。利用此模式,对2014年我国华北干旱期间开展飞机增雨作业的两次降水过程（个例1:5月9～10日;个例2:5月10～11日）进行了云催化数值模拟研究,分析了催化对降水和云物理量场影响,对比了S1和S2方案催化效果的异同。结果表明,在云层适当部位播撒催化剂,两种催化方案均会达到增雨效果,催化会引起云中各水凝物的明显变化,并导致催化区域温度、垂直速度的变化。个例1中,S2方案的催化影响范围要大于S1方案,在播撒区下游地区,S2方案催化效果要强于S1方案;而个例2中两方案催化效果没有表现出显著差异。S1和S2方案的催化效果在不同个例中表现不同,其重要原因在于两种催化方案的催化机制差异以及云系动力条件、水汽条件的不同。通过采用适当的催化剂量,在其他催化设置条件相同的情况下,S1和S2方案可以取得相似的催化效果,但需注意由于二者催化机制的差异,在一些具体云系条件下,二者的催化效果会有一定差异。当实际人工增雨作业采用碘化银催化剂时,相应的催化模拟研究使用S2方案更为适合。     

周成旭,吴玉霖

通过连续观察和摄影，详细研究了夜光藻的二分裂和核分裂过程。发现夜光藻分裂时具核外突细胞膜现象，双鞭毛配子和多种状态的配子结合。结果表明，二分裂是夜光藻的主要繁殖方式，核分裂形成营养细胞的机会甚微，且具有某种程度的性健化不完善。     

一次人工增雨作业效果的中尺度数值模拟

本文根据AgI播撒影响机制,把AgI催化过程耦合到初始条件、边界条件更完善且有业务化能力的中尺度WRF模式中,并利用该模式对溧阳天目湖积云增雨过程进行中尺度催化数值模拟分析。实况资料及数值模拟分析结果表明,该模式成功地模拟了溧阳天目湖地区的对流云系,作业后催化云的强回波面积扩大,平均回波强度增加,地面降水量增加,且微物理过程分析表明,作业后催化云中高空冰晶、雪、霰冰相大粒子含量增加,相应地低空雨水含量增加,导致地面降水量增加。     

Observations of Comet C/2001 A2 (Linear) with the Multipupil Fiber Spectrograph

We present preliminary results of observations of the spectrum of comet C/2001 A2(LINEAR) obtained with the Multipupil Fiber Spectrograph, installed in the PrimeFocus of the 6-m Telescope of the SAO of the RAS (Northern Caucasus, NizhnyArkhyz), on August 11/12, 12/13 and 14/15, 2001. High resolution spectra of thecomet were obtained in the range from 3800–5200 AA. The emission lines in the spectrum of comet C/2001 A2 (LINEAR) on Aug. 12, 2001 were identified. Thefluorescent continuum in the spectrum of comet C/2001 A2 (LINEAR) on Aug. 12,2001 is detected.     

Cometary nuclear magnitudes from sky survey observations

The determination of the nuclear magnitudes of comets, and with it nuclear size frequency distributions, is strongly complicated by cometary activity. By now, only nuclear size frequency distributions for Jupiter Family comets are available, and they are still subject of uncertainties. For comets of other dynamical classes, nuclear magnitudes are known for only a few comets. The size frequency distributions are thus not well constrained.In this work we study whether nuclear magnitudes of comets can be constrained from sky survey observations as published by the Minor Planet Center. Observations from sky survey programs in which the comet was classified as a point-like source are analyzed in this respect.From the available published observations from 1998 to 2008, we derive nuclear magnitudes, as well as nuclear radii, for 84 comets. Among these are comets of the Jupiter Family, dynamically old and new isotropic comets, Halley-type comets and Centaurs. For Jupiter Family comets and for isotropic comets, the size frequency distributions are presented.Uncertainties of derived nuclear magnitudes arise from photometry and from potentially undetected activity. However, a comparison with objects with well known nuclear parameters shows that, despite substantial observational uncertainties, nuclear magnitudes are constrained to ±0.6 mag, thereby providing first indications for nuclear sizes. This is particularly relevant for isotropic comets with so far ill-constrained size distributions. Exponents of the differential size frequency distributions of for Jupiter Family comets and for isotropic comets are presented. The values derived here form a basis for future, dedicated observational studies which provide higher measurement accuracy.     

Preliminary Results of the Ground-Based Orographic Snow Enhancement Experiment for the Easterly Cold Fog （Cloud） at Daegwallyeong during the 2006 Winter

The snow enhancement experiments, carried out by injecting AgI and water vapor into orographically enhanced clouds (fog), have been conducted to confirm Li and Pitter’s forced condensation process in a natural situation. Nine ground-based experiments have been conducted at Daegwallyeong in the Taebaek Mountains for the easterly foggy days from January–February 2006. We then obtained the optimized condi- tions for the Daegwallyeong region as follows: the small seeding rate (1.04 g min-1) of AgI for the easte...     

2006 Fragmentation of Comet 73P/Schwassmann-Wachmann 3B observed with Subaru/Suprime-Cam

The fragmentation of the split Comet 73P/Schwassmann-Wachmann 3 B was observed with the prime-focus camera Suprime-Cam attached to the Subaru 8.2-m telescope. The fragmentation revealed dozens of miniature comets [Fuse, T., Yamamoto, N., Kinoshita, D., Furusawa, H., Watanabe, J., 2007. Publ. Astron. Soc. Jpn. 59 (2), 381-386]. We analyzed the Subaru/Suprime-Cam images, detecting no fewer than 154 mini-comets, mostly extending to the southwest. Three were close to the projected orbit of fragment B. We applied synchrone-syndyne analysis, modified for rocket effect analysis, to the mini-fragment spatial distribution. We found that most of these mini-comets were ejected from fragment B by an outburst occurring around 1 April 2006, and three fragments on the leading side of nucleus B could have been released sunward on the previous return. Several fragments might have been released by successive outbursts around 24 April and 2 May 2006. The ratio of the rocket force to solar gravity was 7-23 times larger than that exerted on fragment B. No significant color variation was found. The mean color index, V-R = 0.50 ± 0.07, was slightly redder than that of the Sun and similar to that of the largest fragment, C, which suggests that these mini-fragments were detected mainly through sunlight reflected by dust particles and materials on the nuclei. We examined the surface brightness profiles of all detected fragments and estimated the sizes of 154 fragments. We found that the radius of these mini-fragments was in the 5- to 108-m range (equivalent size of Tunguska impactor). The power-law index of the differential size distribution was q = −3.34 ± 0.05. Based on this size distribution, we found that about 1-10% of the mass of fragment B was lost in the April 2006 outbursts. Modeling the cometary fragment dynamics [Desvoivres, E., Klinger, J., Levasseur-Regourd, A.C., Lecacheux, J., Jorda, L., Enzian, A., Colas, F., Frappa, E., Laques, P., 1999. Mon. Not. Roy. Astron. Soc. 303 (4), 826-834; Desvoivres, E., Klinger, J., Levasseur-Regourd, A.C., Jones, G.H., 2000. Icarus 144, 172-181] revealed that it is likely that mini-fragments smaller than ∼10-20 m could be depleted in water ice and become inactive, implying that decameter-sized comet fragments could survive against melting and remain as near-Earth objects. We attempted to detect the dust trail, which was clearly found in infrared wavelengths by Spitzer. No brightness enhancement brighter than 30.0 mag arcsec⁻² (3σ) was detected in the orbit of fragment B.