阻塞形势下内蒙古东南部地区一次冷涡暴雨过程水汽特征分析

使用常规观测资料、FY-2G卫星及1°×1°的NCEP再分析资料,对2017年7月6—7日内蒙古东南部地区一次冷涡暴雨天气过程进行分析。结果表明:在稳定的"一槽一脊"型环流背景下,阻塞高压稳定维持,西风槽东移受阻移动缓慢,加深为涡,暴雨发生在冷涡发展加强阶段;低空急流建立,一方面形成偏南水汽输送,为暴雨提供源源不断的水汽,水汽收支主要集中在700 hPa以下,暴雨发生前水汽净收入明显增大,南、北边界水汽贡献率大;另一方面,偏南暖湿气流的输送使不稳定层结建立,能量在暴雨区积聚,偏南低空急流与高空急流耦合,又为暴雨发生提供了动力条件;暴雨发生前后湿度场变化显著,大气可降水量最大达到55—60 kg·m^-2,且暴雨发生前增幅显著,增幅近2倍。暴雨区700 hPa (850 hPa)上比湿不低于7 g·kg^-1(12 g·kg^-1),强降水出现在水汽图上白亮区断裂消失后,高层比湿峰值附近和相当黑体温度<230 K为强降水高发区。     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi region.     

THE TEMPORAL AND SPATIAL DISTRIBUTION OF SEA SURFACE WIND ALONG THE COAST OF GUANGDONG PROVINCE IN CHINA

Temporal and spatial distribution characteristics of sea surface wind in Guangdong''s coastal areas were analyzed with data from four offshore observational stations between 2012 and 2015. The results are shown as follows: (1) The probability distribution of wind speed was basically consistent with Gaussian distribution characteristics; winds of Beaufort force 6 or higher were observed mainly in far offshore stations from October to March. (2) The probability distribution of wind direction was represented well by Weibull distribution. The deviation of wind direction of far station was relatively small for it was mainly controlled by monsoon over the South China Sea, while the near offshore station had a relatively large diurnal variation because of the influence of local synoptic systems such as sea-land breeze. (3) There were significant seasonal differences in wind speed and direction observed by different offshore observational stations. In strong wind seasons, the deviation of wind direction was relatively small while the deviation of wind speed was relatively large, and vice versa. In contrast with Class I station, the other three stations exhibited approximately normal distribution of wind direction and wind speed deviations. (4) Wind direction diurnal variation was moderate in windy periods, while it was obvious in relatively lower speed conditions. The deviation of wind speed in windy periods was generally greater because it was influenced by mesoscale weather systems for 10-20 h, and the influence was complicated, resulting in greater local differences in wind speed.     

GRAPES全球集合预报系统模式扰动随机动能补偿方案初步探究

为了体现次网格尺度能量升尺度转换过程中存在的不确定性, 文中将随机动能补偿(Stochastic Kinetic Energy Backscatter, SKEB)方案应用于GRAPES(Global/Regional Assimilation and Prediction System)全球集合预报系统(GRAPES-GEPS), 以更好地表征模式误差并且增大集合离散度。使用的SKEB方案基于具有一定时、空相关特征的随机型以及由数值扩散导致的局地动能耗散率来构造随机流函数强迫。并根据流函数与水平风速旋转分量的关系, 将SKEB方案中的流函数强迫转化为适用于GRAPES全球模式的水平风速扰动。结果表明, SKEB方案的使用一方面能够提高GRAPES对大气动能谱的模拟能力; 另一方面能够改善GRAPES-GEPS的集合离散度与集合平均误差的关系, 增加了集合离散度, 并在一定程度上减小了集合平均误差, 尤其是在热带地区这种改进更为显著。而且该方案使得热带地区连续分级概率评分(CRPS评分)显著减小。就降水预报而言, 从Brier评分与相对作用特征面积(AROC, Area under the Relative Operating Characteristics)的结果来看, SKEB方案有助于改善中国地区小雨[0.1 mm, 10 mm)、中雨[10 mm, 25 mm)与大雨[25 mm, 50 mm)量级降水的概率预报技巧, 而对暴雨[50 mm, ∞)量级降水预报技巧影响很小(24 h降水量)。总体上, 模式扰动随机动能补偿方案提高了GRAPES-GEPS的概率预报技巧。      

中国农业气象模式(CAMM1.0)构建与应用

为发展适宜中国区域农业种植特点的农业气象模式,基于国外作物生长模拟方法,通过模式机理过程改进或重构以及应用方式革新,建立了中国农业气象模式（Chinese AgroMeteorological Model version 1.0,CAMM1.0）。CAMM1.0利用平均温度和土壤水分改进了作物发育进程模式,利用土壤水分改进了作物叶片光合作用、干物质分配和叶面积扩展过程模式,通过蒸发比法扩展了作物蒸散过程模式;自主建立了基于发育进程的冬小麦株高、基于遥感信息的作物灌溉、遥感数据同化、作物长势与灾害评价等模式。基于互联网技术构造了实时运转平台,主要功能包括作物生长过程实时常规模拟与用户个性化定制模拟。CAMM1.0的部分子模式采用多种方法构造,便于多模式集成。CAMM1.0对作物发育进程、光合过程、株高的模拟效果较好,但对土壤水分变化过程的拟合略差,模拟产量略偏低。CAMM1.0评价淮河流域夏玉米年际干旱减弱而涝渍增加的趋势与实际基本相符。     

前倾槽背景下河套地区一次强冰雹天气成因分析

利用常规观测资料、多普勒雷达资料以及NECP(1°×1°)逐6 h再分析资料,对2016年9月22日内蒙古河套地区强冰雹天气成因进行分析,结果表明:在前倾槽有利的天气尺度环流背景下,中高层干冷空气叠加在低层暖湿空气上形成了对流不稳定层结条件。较大的对流有效位能(CAPE)、假相当位温θse高能区、0～6 km中等强度的垂直风切变有利于强冰雹的形成。反射率因子有"钩状回波"、前侧入流缺口、后侧入流缺口;前侧入流缺口表明有上升气流,强盛的上升气流有利于空中大冰雹的增长,后侧入流缺口表明有下沉气流,有可能引起破坏性大风。基本径向速度剖面有明显的中气旋特征,强烈的辐合有利于对流风暴上升运动的进一步发展;对流风暴后侧有辐散下沉气流降落到地面,辐散风出流促使对流风暴前沿的暖湿气流强迫抬升,从而使上升运动得到进一步的加强。反射率因子剖面有弱回波区、回波悬垂且55 dBZ以上的强回波核心位置超过-20℃层等温线高度以上;弱回波区左侧的回波强度高达55～60 dBZ且已经接地,表明有大冰雹降落到地面。     

钛酸镧烧结物中游离氧化镧的测定

本文研究了La(Ⅲ)与甲基百里酚蓝和溴化十六烷基吡啶在pH7.8—11.0的NH_4OH-NH_4Cl介质中生成紫色络合物的显色反应,λ_(max)=628nm,ε=8.1×10~4,La量在0—90μg/25ml范围内遵循比尔定律,烧结物中一些常见的离子不干扰测定。本法用于烧结物中游离氧化镧的测定,结果满意。     

锡石的晶体结构和形态的关系

本文对不同成因类型的锡石晶体形态进行了研究,并从PBC(周期性键链)理论出发,讨论了锡石晶体形态与晶体结构的关系。笔者认为,锡石晶体具有三种F面,即s{111}、e{101}、m{110},与Hartman对同样结构类型的金红石晶面性质划分有所差异。据锡石晶面结构性质所推导的理想晶体形态图,与晶体测量所得到的天然晶体形态图总体上相吻合。     

Neutron activation studies of the geochemical behaviours of 26 elements in deep-sea drill core sediments from the Indian Ocean

The geochemical behaviours of 26 elements in deep-sea drill core sediments from the Indian Ocean have been investigated with INAA, including Na, K, Ca, Sc, Cr, Fe, Co, Rb, Sr, Zr, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Au, Th and U. Their distribution patterns with depth are also discussed. In terms of the enrichment factors of the respective elements, their residence times in the sea have been calculated by the least squares fitting and are compared with the previous results.