SERIALS

正Acta Geographica Sinica ISSN0375-5444 CN11-1856/P Acta Geologica Sichuan ISSN1006-0995 CN51-1273/P Acta Geologica Sinica ISSN0001-5717 CN11-1951/P Acta Geologica Sinica(English Edition)ISSN1000-9515 CN11-2001/P Acta Geoscientica Sinica ISSN1006-3021 CN11-3474/P Acta Micropalaeontologica Sinica ISSN1000-0674 CN32-1189/Q     

EXPLORATION ENGINEERING

正20141864 Deng Mengchun(Institute of Exploration Technology,CAGS,Chengdu 611734,China);Huang Shenghui Rock Sample Collection and Division Technologies for Air Reverse Circulation Sampling Drilling(Exploration Engineering,ISSN1672-7428,CN11-5063/TD,40(7),2013,p.73-76,80,16 illus.,5 refs.)     

Remote estimation of terrestrial evapotranspiration by Landsat 5 TM and the SEBAL model in cold and high‐altitude regions: a case study of the upper reach of the Shule River Basin,China

Evapotranspiration (ET) is an important expenditure in water and energy balances, especially on cold and high‐altitude land surfaces. Daily ET of the upper reach of the Shule River Basin was estimated using Landsat 5 TM data and the Surface Energy Balance Algorithm for Land (SEBAL) model. Based on observations made at the Suli station, the algorithms of land surface temperature and soil heat flux in SEBAL were modified. Land surface temperature was retrieved and compared with ground truth via three methods: the radiative transfer equation method, the mono‐window algorithm, and the single‐channel method. We selected the best of these methods, mono‐window algorithm, for estimating ET. The average error of daily ET estimated by the modified SEBAL model and measured by the eddy covariance system was 16.4%, with a root‐mean‐square error of 0.52 mm d^?1. The estimated ET means were 3.09, 2.48, and 1.48 mm d^?1 on June 9 (DOY 160), June 25 (DOY 176), and July 27 (DOY 208) of the year 2010, respectively. The average estimated ET on the glacier surface of all days was more than 3 mm d^?1, a measurement that is difficult to capture in‐situ and has rarely been reported. This study will improve the understanding of water balance in cold, high‐altitude regions. Copyright © 2016 John Wiley & Sons, Ltd.     

Rain on snow induced urban floods in cold maritime climate: Risk,indicators and trends

Urban floods pose a societal and economical risk. This study evaluated the risk and hydro-meteorological conditions that cause pluvial flooding in coastal cities in a cold climate. Twenty years of insurance claims data and up to 97 years of meteorological data were analysed for Reykjavík, Iceland (64.15°N; <100 m above sea level). One third of the city's wastewater collection system is combined, and pipe grades vary from 0.5% to 10%. Results highlight semi-intensive rain (<7 mm/h; ≤3 year return period) in conjunction with snow and frozen ground as the main cause for urban flood risk in a climate which undergoes frequent snow and frost cycles (avg. 13 and 19 per season, respectively). Floods in winter were more common, more severe and affected a greater number of neighbourhoods than during summer. High runoff volumes together with debris remobilized with high winds challenged the capacity of wastewater systems regardless of their age or type (combined vs. separate). The two key determinants for the number of insurance claims were antecedent frost depth and total precipitation volume per event. Two pluvial regimes were particularly problematic: long duration (13–25 h), late peaking rain on snow (RoS), where snowmelt enhanced the runoff intensity, elongated and connected independent rainfall into a singular, more voluminous (20–76 mm) event; shorter duration (7–9 h), more intensive precipitation that evolved from snow to rain. Closely timed RoS and cooling were believed to trigger frost formation. A positive trend was detected in the average seasonal snow depth and volume of rain and snowmelt during RoS events. More emphasis, therefore, needs to be placed on designing and operating urban drainage infrastructure with regard to RoS co-acting with frozen ground. Furthermore, more detailed, routine monitoring of snow and soil conditions is important to predict RoS flood events.     

Monitoring over‐winter soil water dynamics in a freezing and snow‐covered environment using a thermally insulated tensiometer

Water potential below a frozen soil layer was continuously monitored over an entire winter period (using thermally insulated tensiometers sheltered in a heated chamber) along with other soil, snow and atmospheric variables. In early winter, the freezing front advanced under a thin snow cover, inducing upward soil water flow in the underlying unfrozen soil. The freezing front started to retreat when the snow cover became thick enough to insulate the soil, resulting in the reversal of the flow direction in the unfrozen zone. These data provide a clear illustration of soil water dynamics, which have rarely been monitored with a tensiometer. Copyright © 2005 John Wiley & Sons, Ltd.     

The impact of deformation on vortex development in a baroclinic moist atmosphere

A mathematical relation between deformation and vertical vorticity tendency is built by introducing the frontogenesis function and the complete vertical vorticity equation, which is derived by virtue of moist potential vorticity. From the mathematical relation, it is shown that properly configured atmospheric conditions can make deformation exert a positive contribution to vortex development at rates comparable to other favorable factors. The effect of deformation on vortex development is not only related to the deformation itself, but also depends on the current thermodynamic and dynamic structures of the atmosphere, such as the convective stability, moist baroclinicity and vertical wind shear(or horizontal vorticity). A diagnostic study of a heavy-rainfall case that occurred during 20–22 July 2012 shows that deformation has the most remarkable effect on the increase in vertical vorticity during the rapid development stage of the low vortex during its whole life cycle. This feature is mainly due to the existence of an approximate neutral layer(about 700 h Pa) in the atmosphere where the convective stability tends to be zero. The neutral layer makes the effect of deformation on the vertical vorticity increase significantly during the vortex development stage, and thus drives the vertical vorticity to increase.     

东北地区春季首场透雨的变化特征及与青藏高原地面加热场强度的关系

利用1958—2012年4—5月东北地区(39°~55°N、118°~135°E)101个站点逐日降水资料、青藏高原地区(25°~40°N、73.75°~103.75°E)JRA-55的地面感热和潜热通量月平均再分析资料以及NCEP/NCAR-I大气环流场的月平均再分析资料,分析了春播期首场透雨出现日期的时空变化特征及其与透雨量和播种期降水量间的关系,以及对青藏高原地面加热场强度异常的响应及其可能机制。结果表明:透雨日期自1958年以来在东北地区的西北和东南大部分区域呈现略微偏晚的趋势;中部有略微偏早的趋势。春播期首场透雨出现时间偏早(晚)的地方,首场透雨量小(大),春播期总降水量多(少)。同时,4月青藏高原地面加热场强度增强(减弱),有利于(不利于)来自北方的冷空气和南方的暖湿气流在东北上空交汇,且上升气流增强(减弱),水汽输送充沛(减少),导致该地区春季首场透雨出现的时间偏早(晚)。     

江苏一次锢囚状MCS和相关中涡旋MCV的观测分析

利用常规地面和高空气象观测资料,结合气象卫星云图和雷达回波,分析了2009年6月14日15—23时(北京时,下同),造成江苏强对流天气的一个中尺度对流系统(MCS)的锢囚状特征的形成过程及其垂直结构。地面中尺度分析表明,雷暴高压东侧在飑前倒槽北端发展的闭合低压环流的东南气流将暖湿空气输送到冷性雷暴高压的北侧形成东南一西北向的暖舌,从而形成锢囚状的结构。长三角探空网资料的垂直结构分析表明,在对流层下部地面到850 hPa为冷性的雷暴高压,在对流层中部700 hPa为冷性的α中尺度涡旋(MCV),而500 hPa已转变为暖性的MCV。静力学关系可以说明MCV仅仅存在于700~500 hPa的原因和MCS下冷上暖的热力结构密切相关。     

5—6月东北冷涡持续活动及强度特征

利用1960—2012年5—6月NCEP/NCAR逐日再分析资料,基于冷涡经典定义,采取客观识别方法检索东北冷涡活动过程,根据东北冷涡活动时空变化特征给出东北冷涡持续活动过程标准, 通过冷涡强度指数进行定量化分析,该指数对冷涡持续活动过程具有较好表征意义。冷涡活动强对应5月乌拉尔山阻塞高压、贝加尔湖阻塞高压和6月鄂霍次克海阻塞高压活动频繁。通过强弱指数年合成,得到6月强指数年冷涡系统较深厚,集中于对流层中高层,冷心结构明显,具有一定大气斜压特征; 高层存在冷中心,低层有冷空气活动,中高层西风带呈明显的上游分流和下游汇合特征,分汇流之间呈东北高、西南低的偶极子阻塞形势;弱指数年冷涡系统较浅薄,主要集中在对流层中低层,冷心结构不明显,不存在阻塞形势。