内蒙古巴林左旗二叠系碎屑锆石LA ICP MS U Pb年龄及构造意义

内蒙古巴林左旗碧流台地区分布一套碎屑岩,以砂板岩组合为特征,时代原为早二叠世。对该套地层所取砂岩样品进行LA-ICP-MS U-Pb年代学研究,对取自长石岩屑砂岩样品中100颗碎屑锆石进行测试分析,结果显示,100颗锆石的谐和年龄主要集中分布在4个年龄区间,分别为253~298Ma,309~362Ma,428~595Ma,851~1526Ma,最年轻的一组锆石年龄为253~298Ma,存在266Ma的锆石峰值年龄。266Ma的年龄限定了地层的沉积时限,即地层应在晚二叠世沉积,且砂岩的碎屑锆石年龄特征和地层岩性组合与区域上发育的林西组可以对比,故将该套地层划为林西组。年龄数据普值特征反映出,该地层具有多物源供给的特点,但物源主体来自东北各地块,未见华北板块的物源区年龄信息,表明华北板块与西伯利亚板块在晚二叠世并未完全碰撞闭合,253~298Ma的锆石年龄与西拉木伦缝合带附近与板块俯冲、碰撞相关的岩浆事件相吻合,表明两大板块的最终碰撞拼合时间应晚于266Ma。     

云南思茅盆地景谷地区下白垩统曼岗组风成砂岩沉积学特征及其古气候意义

本文通过野外剖面的观察和实测,室内薄片鉴定、阴极发光分析、粒度分析、扫描电镜及能谱测试分析,研究了云南思茅盆地景谷地区下白垩统曼岗组风成砂岩沉积学特征,详细了解了风成砂岩的发育特征,以期为研究区白垩纪古气候研究提供新的资料,为我国钾盐勘探提供一定的地质依据和新的思路。研究结果表明:1研究区曼岗组主要出露一套中—细粒石英砂岩、岩屑石英砂岩,发育中—大型交错层理、平行层理,碎屑颗粒分选中等-好,以次圆状-圆状为主,孔隙不发育,杂基含量少;2曼岗组中段发育具平行层理的石英砂岩,粒度分布呈双众数,带状分布,石英颗粒为浑圆状,颗粒表面见Fe、Mn质薄膜,颗粒表面具明显的碟形坑等特征,属于典型的风成砂岩,初步判定其沉积环境为风成沙丘和丘间沉积;3景谷地区下白垩统曼岗组风成砂岩,整体表现为干热型气候,曼岗组中段为丘间沉积,曼岗组上段和下段为沙丘沉积。其在搬运沉积成岩过程中经历了强烈的物理、化学风化作用,整体表现为氧化环境,风力较大,风速稳定,持续时间长。此外,可能还经历了一段时期的湿润性气候环境,这可能与大气降水、大气环流带的迁移,以及白垩纪海侵作用等有关。     

滇西思茅盆地景谷地区曼岗组石英颗粒表面特征及其指示意义

石英具有硬度大和化学稳定性高的特点,其颗粒表面特征能很好的反映沉积环境,通过扫描电镜观察石英表面微细特征是判别沉积环境行之有效的方法。思茅盆地白垩系曾一度被认为是陆相水成沉积,笔者通过野外识别及室内基础研究发现,景谷地区下白垩统曼岗组具有风成沉积特征,需对该套地层开展石英颗粒表面特征的系统研究来进一步确定其沉积相,研究结果表明:研究区曼岗组石英颗粒表面具有明显的风成特征,磨圆度高,普遍发育典型的蝶形撞击坑、新月形撞击坑、毛玻璃化表面,存在沙漠漆,极易与水成特征相区别;而其较强的溶蚀作用与沉淀作用则显示了当时干旱炎热的气候条件。在风成沉积确定的基础上,笔者再结合典型沉积构造,粒度分析、岩性特征等沉积特征进行综合分析,认为研究区曼岗组应属沙漠沉积。     

Optical observations of the broad-lined type Ic supernova SN 2012ap

The optical observations of the type Ic supernova(SN Ic) SN 2012 ap in NGC 1729 are presented. A comparison with other SNe Ic indicates that SN 2012 ap is highly reddened(with E(B- V)host～0.8 mag) and may represent one of the most luminous SNe Ic ever observed, with an absolute V-band peak magnitude of ～-19.3±0.5 mag after extinction correction. The near-maximum-light spectrum shows wide spectral features that are typical of broad-lined SNe Ic. One interesting feature in the spectrum is the appearance of some narrow absorption features that can be attributed to the diffuse interstellar bands, consistent with the large reddening inferred from the photometric method. Based on the light curves and the spectral data, we estimate that SN 2012 ap produced a56 Ni mass of ～ 0.3 ± 0.1M in the explosion, with an ejecta mass of 2.4+0.7-0.7M and a kinetic energy of E5K= 1.1+0.4-0.4× 102 erg. The properties of its progenitor are also briefly discussed.     

Fidelity of the APHRODITE Dataset in Representing Extreme Precipitation over Central Asia

Using rain-gauge-observation daily precipitation data from the Global Historical Climatology Network (V3.25) and the Chinese Surface Daily Climate Dataset (V3.0), this study investigates the fidelity of the AHPRODITE dataset in representing extreme precipitation, in terms of the extreme precipitation threshold value, occurrence number, probability of detection, and extremal dependence index during the cool (October to April) and warm (May to September) seasons in Central Asia during 1961–90. The distribution of extreme precipitation is characterized by large extreme precipitation threshold values and high occurrence numbers over the mountainous areas. The APHRODITE dataset is highly correlated with the gauge-observation precipitation data and can reproduce the spatial distributions of the extreme precipitation threshold value and total occurrence number. However, APHRODITE generally underestimates the extreme precipitation threshold values, while it overestimates the total numbers of extreme precipitation events, particularly over the mountainous areas. These biases can be attributed to the overestimation of light rainfall and the underestimation of heavy rainfall induced by the rainfall distribution–based interpolation. Such deficits are more evident for the warm season than the cool season, and thus the biases are more pronounced in the warm season than in the cool season. The probability of detection and extremal dependence index reveal that APHRODITE has a good capability of detecting extreme precipitation, particularly in the cool season.     

Midlatitude unstable air-sea interaction with atmospheric transient eddy dynamical forcing in an analytical coupled model

While recent observational studies have shown the critical role of atmospheric transient eddy (TE) activities in midlatitude unstable air-sea interaction, there is still a lack of a theoretical framework characterizing such an interaction. In this study, an analytical coupled air-sea model with inclusion of the TE dynamical forcing is developed to investigate the role of such a forcing in midlatitude unstable air-sea interaction. In this model, the atmosphere is governed by a barotropic quasi-geostrophic potential vorticity equation forced by surface diabatic heating and TE vorticity forcing. The ocean is governed by a baroclinic Rossby wave equation driven by wind stress. Sea surface temperature (SST) is determined by mixing layer physics. Based on detailed observational analyses, a parameterized linear relationship between TE vorticity forcing and meridional second-order derivative of SST is proposed to close the equations. Analytical solutions of the coupled model show that the midlatitude air-sea interaction with atmospheric TE dynamical forcing can destabilize the oceanic Rossby wave within a wide range of wavelengths. For the most unstable growing mode, characteristic atmospheric streamfunction anomalies are nearly in phase with their oceanic counterparts and both have a northeastward phase shift relative to SST anomalies, as the observed. Although both surface diabatic heating and TE vorticity forcing can lead to unstable air-sea interaction, the latter has a dominant contribution to the unstable growth. Sensitivity analyses further show that the growth rate of the unstable coupled mode is also influenced by the background zonal wind and the air–sea coupling strength. Such an unstable air-sea interaction provides a key positive feedback mechanism for midlatitude coupled climate variabilities.

     

新降雪密度估算方法研究进展

降雪深度预报是北方地区冬季气象服务的重点和难点,新降雪密度估算是降雪深度预报的关键技术。本文回顾了新降雪密度估算中需要着重考虑的气象要素,并对国内外广泛使用的几类新降雪密度估算方法进行了详细的介绍和对比,在此基础上,评述几种估算方法的特点、局限性以及它们之间的承接联系,并对未来新降雪密度估算的发展方向进行了展望。主要结论为:(1)温度、风速、湿度的垂直分布及太阳辐射、降水量是影响新降雪密度的重要气象要素。(2)目前被广泛应用的新降雪密度估算方法有设为常数法、建立公式法、后处理诊断法和基于微物理过程法等四类,四种方法各具特点和局限性,且存在着上下承接关系。(3)较为科学的后处理诊断法和基于微物理过程法有着各自的相对优势也有着难以克服的不足,未来新降雪密度的估算需要在这两种方法的相互促进、共同提高中逐步发展。     

Association of Indian Ocean ITCZ Variations with the Arctic Oscillation during Boreal Winter

In this study,the authors analyzed the associations between the Arctic Oscillation(AO)and the tropical Indian Ocean(TIO)intertropical convergence zone(ITCZ)in boreal winter for the period 1979–2009.A statistically significant AO-TIO ITCZ linkage was found.The ITCZ vertical air motion is significantly associated with the AO,with upward(downward)air motion corresponding to the positive(negative)AO phase.The Arabian Sea anticyclone plays a crucial role in linking the AO and the TIO ITCZ.The Arabian Sea vorticity is strongly linked to high-latitude disturbances in conjunction with jet stream waveguide effects of disturbance trapping and energy dispersion.During positive(negative)AO years,the Arabian Sea anticyclone tends to be stronger(weaker).The mean vorticity over the Arabian Sea,averaged from 850hPa to 200 hPa,has a significant negative correlation with AO(r=0.63).The anomalous anticyclone over the Arabian Sea brings stronger northeastern winds,which enhance the ITCZ after crossing the equator and result in greater-than-normal precipitation and minimum outgoing long-wave radiation.     

基于Hurst指数的黑龙江省作物生长季降水趋势研究

基于黑龙江省78个气象站1971—2016年逐日降水资料,综合采用墨西哥帽小波分析、Hurst指数分析等方法,对黑龙江省作物生长季(5—9月)降水量变化和未来趋势进行分析及预测。结果表明:1971—2016年,黑龙江省生长季、5月、6月降水量存在7 a、14 a、7 a左右的主周期,7月、8月、9月降水量存在2 a、3 a、7 a左右的第1主周期及6 a、11 a、21 a左右的第2主周期,各月均存在最近几年降水偏多的趋势;作物生长季降水量年际间为波动式振荡变化,7月、8月振荡幅度相对较大。年代际变化总体存在增加—减少—增加趋势,20世纪80年代、90年代降水量普遍偏多,2010年以来出现急转升高变化;单站各月Hurst指数均在0.5以上,降水存在比较明显的赫斯特现象;降水主要出现在夏季且以7月最为集中,最近几年降水偏多、7月异常降水集中以及主要流域未来7月降水的持续增加趋势在农业防灾减灾上值得关注。