The 2020/21 Extremely Cold Winter in China Influenced by the Synergistic Effect of La Niña and Warm Arctic

In the first half of winter 2020/21,China has experienced an extremely cold period across both northern and southern regions,with record-breaking low temperatures set in many stations of China.Meanwhile,a moderate La Ni?a event which exceeded both oceanic and atmospheric thresholds began in August 2020 and in a few months developed into its mature phase,just prior to the 2020/21 winter.In this report,the mid?high-latitude large-scale atmospheric circulation anomalies in the Northern Hemisphere,which were forced by the negative phase of Arctic Oscillation,a strengthened Siberian High,an intensified Ural High and a deepened East Asian Trough,are considered to be the direct reason for the frequent cold surges in winter 2020/21.At the same time,the synergistic effect of the warm Arctic and the cold tropical Pacific(La Ni?a)provided an indispensable background,at a hemispheric scale,to intensify the atmospheric circulation anomalies in middle-to-high latitudes.In the end,a most recent La Ni?a prediction is provided and the on-coming evolution of climate is discussed for the remaining part of the 2020/21 winter for the purpose of future decision-making and early warning.     

Experiments with the Improved Dynamical-Statistical-Analog Ensemble Forecast Model for Landfalling Typhoon Precipitation over South China

In recent work, three physical factors of the Dynamical-Statistical-Analog Ensemble Forecast Model for Landfalling Typhoon Precipitation (DSAEF_LTP model) have been introduced, namely, tropical cyclone (TC) track, TC landfall season, and TC intensity. In the present study, we set out to test the forecasting performance of the improved model with new similarity regions and ensemble forecast schemes added. Four experiments associated with the prediction of accumulated precipitation were conducted based on 47 landfalling TCs that occurred over South China during 2004-2018. The first experiment was designed as the DSAEF_LTP model with TC track, TC landfall season, and intensity (DSAEF_LTP-1). The other three experiments were based on the first experiment, but with new ensemble forecast schemes added (DSAEF_LTP-2), new similarity regions added (DSAEF_LTP-3), and both added (DSAEF_LTP- 4), respectively. Results showed that, after new similarity regions added into the model (DSAEF_LTP-3), the forecasting performance of the DSAEF_LTP model for heavy rainfall (accumulated precipitation ≥250 mm and ≥100 mm) improved, and the sum of the threat score (TS250 + TS100) increased by 4.44%. Although the forecasting performance of DSAEF_LTP-2 was the same as that of DSAEF_LTP-1, the forecasting performance was significantly improved and better than that of DSAEF_LTP-3 when the new ensemble schemes and similarity regions were added simultaneously (DSAEF_LTP-4), with the TS increasing by 25.36%. Moreover, the forecasting performance of the four experiments was compared with four operational numerical weather prediction models, and the comparison indicated that the DSAEF_LTP model showed advantages in predicting heavy rainfall. Finally, some issues associated with the experimental results and future improvements of the DSAEF_LTP model were discussed.     

Experiments of DSAEF_LTP Model with Two Improved Parameters for Accumulated Precipitation of Landfalling Tropical Cyclones over Southeast China

The Dynamical-Statistical-Analog Ensemble Forecast model for landfalling tropical cyclones (TCs) precipitation (DSAEF_LTP) utilises an operational numerical weather prediction (NWP) model for the forecast track, while the precipitation forecast is obtained by finding analog cyclones, and making a precipitation forecast from an ensemble of the analogs. This study addresses TCs that occurred from 2004 to 2019 in Southeast China with 47 TCs as training samples and 18 TCs for independent forecast experiments. Experiments use four model versions. The control experiment DSAEF_LTP_1 includes three factors including TC track, landfall season, and TC intensity to determine analogs. Versions DSAEF_LTP_2, DSAEF_LTP_3, and DSAEF_LTP_4 respectively integrate improved similarity region, improved ensemble method, and improvements in both parameters. Results show that the DSAEF_LTP model with new values of similarity region and ensemble method (DSAEF_LTP_4) performs best in the simulation experiment, while the DSAEF_LTP model with new values only of ensemble method (DSAEF_LTP_3) performs best in the forecast experiment. The reason for the difference between simulation (training sample) and forecast (independent sample) may be that the proportion of TC with typical tracks (southeast to northwest movement or landfall over Southeast China) has changed significantly between samples. Forecast performance is compared with that of three global dynamical models (ECMWF, GRAPES, and GFS) and a regional dynamical model (SMS-WARMS). The DSAEF_LTP model performs better than the dynamical models and tends to produce more false alarms in accumulated forecast precipitation above 250 mm and 100 mm. Compared with TCs without heavy precipitation or typical tracks, TCs with these characteristics are better forecasted by the DSAEF_LTP model.     

深部咸水层二氧化碳地质储存场地选址储盖层评价

深部咸水层CO2地质储存属于环保型工程项目,开展地质评价来确定良好的储盖层是实现CO2地质储存长期、有效、安全封存的首要前提。储层地质评价内容主要包括储层的物理性质及其注入能力等;盖层地质评价内容主要包括盖层发育特征及封闭能力等。在规划选址到工程选址的不同阶段,储盖层评价的内容和对象应根据不同阶段的目的依次提高精度和量化程度。通过国内深部咸水层CO2地质储存工程场地选址阶段划分,结合储盖层地质评价的主要内容,初步建立了储盖层适宜性评价指标及其分级标准,对国内深部咸水层CO2地质储存工程场地选址中的储盖层地质评价及适宜性评价工作具有一定的指导意义。     

大兴安岭绿林林场一带兴华渡口岩群原岩恢复及大地构造环境探讨

兴华渡口岩群作为额尔古纳地块的基底,其变质年龄、原岩类型及大地构造背景一直是地质学家关注的热点。以大兴安岭北段绿林林场一带兴华渡口岩群作为研究对象,利用锆石U-Pb同位素测年限定了原岩的变质时代,结合岩相学与地球化学综合分析方法开展原岩恢复,并进一步讨论了其形成的大地构造背景。研究认为兴华渡口岩群主要由斜长角闪岩类、浅粒岩类、变粒岩类和石英岩类组成;斜长角闪岩类原岩为基性火山岩,浅粒岩类原岩为英安质凝灰岩,石英岩和变粒岩原岩为泥质粉砂岩;斜长角闪岩类亏损非活动性微量元素Ta、Nd、P,大地构造环境属岛弧环境;浅粒岩类主要亏损Ta、Nd、P、Sr、Ti等元素,形成于大陆边缘造山带环境。绿林林场一带兴华渡口岩群的变质年龄下限为774.1±3.8 Ma。      

裂缝性油藏控水堵水方法研究与应用

随着油田逐渐进入后期开采,调堵井的数量不断增加,所面临的问题是如何在高温、高盐以及裂缝性等恶劣油藏条件下提高采收率技术。目前凝胶类和颗粒类堵剂依然是裂缝性油藏化学调堵体系的主流;另外基于对水体分布、能量预测等油藏地质条件全面认识下的各种物理堵水技术也得到了较好应用。从裂缝性油藏控水堵水难点出发,介绍了国内外的配套技术,重点综述了恶劣油藏条件下的各种凝胶体系,并分析了提高凝胶体系热稳定性的研究思路,认为聚合物高温碳化作用对凝胶的使用有着变革性意义。用某种高吸水材料配成的软颗粒状凝胶完井液130℃高温下与低渗岩心动态污染时,在岩心端面形成强度高、韧性好的黄-黑色胶质暂堵层,极大地避免了漏失,降低了水相圈闭的损害,在中国东海天外天高温低渗气田A1s、A7完井中取得了较好应用效果。另外,丙烯酰胺与丙烯酸叔丁酯的共聚物(PAtBA)用聚乙烯亚胺作交联剂的凝胶体系在国外已得到了成功的应用,聚乙烯亚胺有着低毒、环境友好等诸多优点,研制出性能更优越的聚合物与之交联对未来的凝胶体系研究有着重要意义。最后从控水-堵水-治水整体思路出发,提出了对今后的研究设想。     

天津地区地热流体化学成分垂向演化特征研究

天津地区地热流体化学成分具有明显的垂向分层演化特征,由浅至深不仅有TDS增高、水化学类型由HCO3-Na型向SO4-Na或Cl-Na型演化的特征,而且具有分层演化特征,即不同热储层段的地热流体水化学特征及演化规律不同,说明其补给、径流、排泄自成系统。     

武汉城市相对湿度气候学特征与长期变化趋势

在对相对湿度(RH)序列进行均一性检验和订正的基础上,分析了武汉4个城市站RH的气候学特征和长期变化趋势。结果表明:(1)迁站对RH序列引起较大非均一性偏差,其中武汉站2010年迁站引起的偏差达到8%;(2)城区年平均RH较高,介于75%~85%,武汉站最高;(3)每年1~6月城区RH逐渐增加,6月达到峰值,之后缓慢减少,但季节内变化一般很小,月际间差异仅有0.1%~2.5%,存在夏季RH最高,春、秋次之,冬季最低的季节性特征;(4)武汉城市区域1961~2015年平均RH总体呈长期减少趋势,线性变化趋势-0.81%/10 a,20世纪90年代之后下降趋势加剧;(5)近55年城区春、秋、冬3个季节平均RH均呈不同程度的下降,以春季最为明显,夏季存在较为显著的上升趋势,但1991后年及四季均呈现显著的下降趋势。     

Changes in Water Use Efficiency Caused by Climate Change,CO2 Fertilization,and Land Use Changes on the Tibetan Plateau

Terrestrial ecosystem water use efficiency(WUE) is an important indicator for coupling plant photosynthesis and transpiration, and is also a key factor linking the carbon and water cycles between the land and atmosphere. However,under the combination of climate change and human intervention, the change in WUE is still unclear, especially on the Tibetan Plateau(TP). Therefore, satellite remote sensing data and process-based terrestrial biosphere models(TBMs) are used in this study to investigate ...     

河北大茂山碘化银地面发生器增雪作业影响分析

利用常规气象资料、MICAPS资料和NECP/NCAR再分析资料,结合高斯模拟,分析了2012年11月10日唐县大茂山地基碘化银发生器增雪作业的作业条件。结果发现,此次天气背景为自西南向东北移动的冷涡云系,根据帕斯奎尔(Pasquill)稳定度分类法得出作业时间段大气处于中性层结状态;高斯模式模拟得出,有效的AgI浓度向上扩散范围高达3.0 km;作业点作业时段上空至3.2 km均处于上升气流区,计算出作业点发生器出口温度1.0℃。因冬季人工观测云底高度多为2.5~3.0 km,综合分析认为,该作业点的选址是合适的,此次作业条件较好,可以将催化剂输送到云中,起到催化作用。