2021年河南“7.20”极端暴雨动、热力和水汽特征观测分析

利用MICAPS观测降水数据、欧洲气象中心ERA5再分析资料和FY-4A卫星云顶亮温数据,对2021年7月20日河南极端暴雨进行综合分析。结果表明,此次暴雨受200 hPa两槽一脊、大陆高压、副热带高压（副高）西伸北抬和台风“烟花”西移、“查帕卡”台风倒槽等多尺度天气系统共同影响,黄淮气旋的西南气流与副高和“烟花”之间的东南气流稳定控制河南地区,边界层急流供应充沛水汽,在太行山和嵩山迎风坡辐合抬升,致使河南暴雨长时间维持,产生极端降水量。西南气流穿过从广东和广西延伸到河南的高湿带,副高和“烟花”引导东南气流经过从东海洋面延伸到河南的相对较弱湿区,这两条水汽输送带在太行山和嵩山地形阻挡下汇合在河南北部,为暴雨供应水汽。丰富的可降水量、水汽过饱和、深厚暖云层以及降水系统较强的水汽消耗率为郑州高降水效率提供有利条件。郑州低层大气经历多次从强层结不稳定到弱层结不稳定的转化,边界层急流引起的垂直风切变和气流辐合对层结稳定度变化有重要影响。黄淮气旋内部中尺度涡旋对河南暴雨发生发展至关重要,不但提供西南气流,还产生较强的位势高度纬向平流,增强边界层急流。嵩山与太行山余脉构成喇叭口地形,边界层急流在嵩山北侧和东侧爬坡,促使山前水汽堆积,激发和加强暴雨。中尺度云团合并小尺度云团,发展成结构密实的孤立云团,稳定少动,对暴雨有重要影响。降水区上空广义湿位涡异常,由于广义湿位涡能够刻画中尺度系统的垂直风切变、涡度以及大气湿斜压性和层结不稳定等动力和热力因素垂直结构特点,所以对中尺度系统和降水落区有一定指示意义。     

华北陆块2.56～2.52 Ga增氧事件对成矿和生命演化的影响

地球表层大气氧浓度的显著增高是地球史上最重大的地质事件之一,它不仅改变了地球表层环境,促进了生命演化,而且加速了表生地质过程,形成一系列适应环境突变的岩石和重要矿床。地球在前寒武纪时期曾发生过两次大气快速增氧事件,分别为大氧化事件(GOE)和新元古代氧化事件(NOE)。本文主要论述华北陆块新太古代晚期增氧事件的时限及其对成矿和生命演化的影响。华北陆块新太古代晚期形成千余个氧化物相BIF型铁矿床和矿点,属于阿尔戈马型,累计查明资源储量约335.36亿t,占全国铁矿总资源储量46%。该类矿床和矿点形成于弱碱性氧化环境,成矿时代主要介于2.56～2.52 Ga,并经历了2.51～2.50 Ga的变质作用。通过对BIF型铁矿床中矿石的Ce异常、铁同位素组成和硫同位素非质量分馏效应(MIF-S)等特征研究,显示在2.56～2.52 Ga期间大气圈的氧浓度大幅度升高,并由缺氧还原环境变为具一定氧浓度(1%～10%PAL)的氧化环境,暗示华北陆块在此期间曾出现过一次显著的增氧事件。其对华北陆块的成矿作用产生了重要影响,主要表现在以下三个方面:(1)形成大量氧化物相BIF型铁矿床,这是中国最重要的铁矿...     

Assimilation and Simulation of Typhoon Rusa （2002） Using the WRF System

Using the recently developed Weather Research and Forecasting (WRF) 3DVAR and the WRF model, numerical experiments are conducted for the initialization and simulation of typhoon Rusa (2002).The observational data used in the WRF 3DVAR are conventional Global Telecommunications System (GTS) data and Korean Automatic Weather Station (AWS) surface observations. The Background Error Statistics (BES) via the National Meteorological Center (NMC) method has two different resolutions, that is, a 210-km horizontal grid space from the NCEP global model and a 10-km horizontal resolution from Korean operational forecasts. To improve the performance of the WRF simulation initialized from the WRF 3DVAR analyses, the scale-lengths used in the horizontal background error covariances via recursive filter are tuned in terms of the WRF 3DVAR control variables, streamfunction, velocity potential, unbalanced pressure and specific humidity. The experiments with respect to different background error statistics and different observational data indicate that the subsequent 24-h the WRF model forecasts of typhoon Rusa‘s track and precipitation are significantly impacted upon the initial fields. Assimilation of the AWS data with the tuned background error statistics obtains improved predictions of the typhoon track and its precipitation.     

ANN-based model for predicting the bearing capacity of strip footing on multi-layered cohesive soil

In reality, footings are most likely to be founded on multi-layered soils. The existing methods for predicting the bearing capacity of 4-layer up to 10-layer cohesive soil are inaccurate. This paper aims to develop a more accurate bearing capacity prediction method based on multiple regression methods and multi-layer perceptrons (MLPs), one type of artificial neural networks (ANNs). Predictions of bearing capacity from the developed multiple regression models and MLP in tractable equations form are obtained and compared with the value predicted using traditional methods. The results indicate ANNs are able to predict accurately the bearing capacity of strip footing and outperform the existing methods.     

CLIMATOLOGICAL VARIATION FEATURES OF TYPHOON PRECIPITATION INFLUENCING FUJIAN FOR THE PAST 46 YEARS

The results of an analysis of the temporal and spatial distribution of typhoon precipitation influencing Fujian from 1960 to 2005 show that typhoon precipitation in Fujian province occurs from May to November, with the most in August. There has been a decreasing trend since 1960. Typhoon precipitation gradually decreases from the coastal region to the northwestern mainland of Fujian and the maximum typhoon precipitation occurs in the northeast and the south of Fujian. Typhoon torrential rain is one of the extreme rainfall events in Fujian. High frequencies of typhoon torrential rain occur in the coastal and southwest regions of the province. With the impact of Fujian’s terrain, typhoon precipitation occurs more easily to the east of the mountains than to the west. Atmospheric circulation at 500 hPa over Asia and sea surface temperature anomalies of the equatorial eastern Pacific are analyzed, with the finding that they are closely connected with the anomaly of typhoon precipitation influencing Fujian, possibly mainly by modulating the northbound track of typhoons via changing the atmosphere circulation to lead to the anomaly of typhoon precipitation over the province.     

Temporal precipitation estimation from nearby radar reflectivity using dynamic factor analysis in the mountainous watershed – a case during Typhoon Morakot

The radar reflectivity (Z)–rain intensity (R) relationship fluctuates in both temporal and spatial scales. The dynamic factor analysis (DFA) and min/max autocorrelation factor analysis (MAFA) was specifically designed for considering various space–time integrations of gauge rainfall and radar reflectivity. We detect representative radar reflectivity observed around rainfall stations that were most responsible for rainfall intensity and identify the crucial patterns of the radar reflectivity in the Kaoping River watershed during Typhoon Morakot. Result shows that the MAFA and DFA can reduce the uncertainty of the dynamic Z‐R relationship effectively. The MAFA separates an entire area into two subareas (southern and northern areas) according to the relationships between the radar reflectivity and min/max autocorrelation factor (MAF) axes. For both areas, the different extents of temporal rainfall correlated with the radar reflectivity were determined using DFA. Especially in the northern area, the radar reflectivity was significantly related to the rainfall intensity for most stations without mountain blockage. Mountain blockages associated with the presence of terrain and wind direction were inferred the major factors that affected the relationship between radar reflectivity and rainfall intensity in the mountainous watershed. Further study can consider the terrain effect and meteorological information, such as wind speed and direction in the DFA model, with the dominant radar reflectivity to estimate the temporal rainfall patterns. Copyright © 2012 John Wiley & Sons, Ltd.     

Inferred fault geometry and slip distribution of the 2010 Jiashian,Taiwan, earthquake is consistent with a thick-skinned deformation model

We invert measurements of coseismic displacements from 139 continuously recorded GPS sites from the 2010, Jiashian, Taiwan earthquake to solve for fault geometry and slip distribution using an elastic uniform stress drop inversion. The earthquake occurred at a depth of ~ 23 km in an area between the Western Foothills fold-and-thrust belt and the crystalline high mountains of the Central Range, providing an opportunity to examine the deep fault structure under Taiwan. The inferred rupture plane is oblique to the prominent orientation of thrust faults and parallel to several previously recognized NW-striking transfer zones that appear to connect stepping thrusts. We find that a fault striking 318°–344° with dip of 26°–41° fits the observations well with oblique reverse-sinistral slip under a low stress drop of about 0.5 MPa. The derived geodetic moment of 2.92 × 10¹⁸ N-m is equivalent to a M_w = 6.24 earthquake. Coseismic slip is largely concentrated within a circular patch with a 10-km radius at the depth between 10 and 24 km and maximum slip of 190 mm. We suggest this earthquake ruptured the NW-striking Chishan transfer fault zone, which we interpret as a listric NE-dipping lateral ramp with oblique slip connecting stepping thrust faults (ramps). The inferred slip on the lateral ramp is considerably deeper than the 7–15 km deep detachment identified in previous studies of western Taiwan. We infer an active basal detachment under western Taiwan at a depth of at least ~ 20–23 km based on these inversion results. The earthquake may have nucleated at the base of the lateral ramp near the intersection with the basal detachment. Coulomb stress change calculations suggest that this earthquake moved several NE-striking active thrust faults in western Taiwan nearer to failure.     

An experimental study on the rocking response of bridge piers with spread footing foundations

Some spread footing foundations from real retrofitting practices in Taiwan were extended to be uneconomically large due to the restriction of foundation uplift regulated in the design code. Although rocking mode of spread footings induced from foundation uplift is not favorable in current design code, recent studies have shown that the rocking of a spread footing may have a beneficial effect on the dynamic performance of piers by reducing the earthquake forces that can be transmitted to the pier base. This implies that the plastic deformation that occurs at the pier's plastic zone can be decreased and as a result the ductility demand of piers can possibly be reduced. In order to gain a better understanding of the structural behavior related to rocking and to clarify that if the widening and strengthening of the foundations to limit the rocking mechanism of spread footing is necessary for the retrofitting work, a series of preliminary rocking experiments were performed. A total of three circular reinforced concrete columns with spread footing foundations were tested. Using pseudo‐dynamic tests and a cyclic loading test, these columns were subjected to different levels of earthquake accelerations, including a near field ground motion. The results of the tests and the rocking behavior of the footings are discussed in this paper. From the benchmark test, the difference between the response behavior of a rocking base and a fixed base foundation was highlighted. By comparing the experimental responses of the retrofitted column with the responses of the original one, the effect of the rocking mechanism on the ductility demand and strength demand of the columns was also identified. Copyright © 2010 John Wiley & Sons, Ltd.     

Shake table tests on clutter levels of typical medicine shelves and contents subjected to earthquakes

Overturned shelves and fallen objects scattered on floors are one of the most frequently observed forms of nonstructural damage after earthquakes. The term ‘clutter’ is adopted in this study to represent this type of damage. Clutter may cause obstructions and thus hinder the use of a room. Making a seismic evaluation of clutter is a daunting task, due to the diversity of the types of shelves and objects and the way the objects are stored. Nonetheless, in order to achieve performance‐based seismic evaluation, especially for critical facilities such as hospitals, it is reasonable to undertake the estimation of clutter when examining the association between the performance of structural and nonstructural elements. Of particular interest in this paper is clutter caused by objects stored on medicine shelves in pharmacies, which are one of the critical departments for delivering post‐earthquake emergency care. Shake table tests were conducted on three conventional types of medicine shelves. Sinusoidal waves and earthquake motions were input uniaxially. The results of the tests using the sinusoidal wave input indicated the relationship between the input excitation intensity and clutter level expressed in scattering distance from the front of the shelf. Tests using earthquake motion input were then conducted and the results were compared with those for sinusoidal waves. Based on a comparison of the results from these tests, criteria for the seismic evaluation of clutter caused by medicine shelves due to earthquakes were proposed. Copyright © 2011 John Wiley & Sons, Ltd.     

基于GPRS的APN无线网络技术在地震前兆观测系统中的应用

随着通讯技术的发展,基于GPRS的APN无线网络通讯技术成为一种新型高效通讯模式,并将其应用于地震前兆观测系统.实际运行结果表明,应用该技术可提高数据传输的稳定性、可靠性、安全性和实时性,是地震前兆观测数据传输的有效通讯手段.