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Features of aerosol optical depth and its relation to extreme temperatures in China during 1980–2001

Acta Oceanologica Sinica 2011年第2期30卷 33-45页

作者： HU Ting sun zhaobo LI Zhaoxin Jiangsu Key Laboratory of Meteorological Disaster Nanjing University of Information Scienceand Technology Nanjing 210044 China The Department of Atmospheric Science Nanjing University of Information Science andTechnology Nanjing 210044 China Laboratoire de Meteorologie Dynamique CNRS France

Based on Total Ozone Mapping Spectrometer （TOMS） monthly aerosol optical thickness （AOT） measurements in 1980–2001 a study is made of space/time patterns and difference between land and sea of AOT 0.50 μm thick over China,which are put into correlation analysis with synchronous extreme temperature indices （warm/cold day and night）.Results suggest that 1） the long-term mean AOT over China is characterized by typical geography,with pronounced land-sea *** AOT has significant seasonality and its seasonal difference is diminished as a function of latitude.2） On the whole,the AOT displays an appreciably increasing trend,with the distinct increase in the eastern Qinghai-Tibetan plateau and SW China,North China,the mid-lower Changjiang （MiLY） valley as well as the South China Sea,but marginal decrease over western/northern Xinjiang and part of South China.3） The AOT over land and sea is marked by conspicuous intra-seasonal and -yearly oscillations,with remarkable periods at one-,two-yr and more （as interannual periods）.4） Land AOT change is well correlated with extremely temperature ***,the correlations of AOT to the extreme temperature indices are more significant in Eastern China with 110 ° E as the *** high-correlation regions are along the Southern China coastline,the Loess Plateau and the Sichuan Basin,and even higher in North China Plain and the mid-lower Changjiang River reaches.5） Simulations of LMDZ-regional model indicate that aerosol effects may result in cooling all over China,particularly in Eastern *** contribution of aerosol change may result in more decrease in the maximum temperature than the minimum,with decrease of 0.11/0.08 K for zonal average,respectively.

关键词： aerosol optical thickness extreme temperature index space/time pattern trend correlation

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基于鸽群优化改进动态窗的多无人车协同编队避障控制

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工程科学学报 2024年第7期46卷 1279-1285页

作者：李兆博孙双蕾北京航空航天大学自动化科学与电气工程学院北京100083 北京特种机械研究所北京100143

在复杂未知的战场环境中,无人车集群较单台无人车可承担更为复杂的任务,无人车集群协同编队避障行驶是群体智能领域研究热点之一.针对未知环境下无人车集群在规避障碍物时容易出现动态位置与预期队形偏差较大问题,本文提出了一种基于改... 详细信息

在复杂未知的战场环境中,无人车集群较单台无人车可承担更为复杂的任务,无人车集群协同编队避障行驶是群体智能领域研究热点之一.针对未知环境下无人车集群在规避障碍物时容易出现动态位置与预期队形偏差较大问题,本文提出了一种基于改进动态窗的无人车编队协同避障控制方法,在基本动态窗路径评价函数的方位角评价因子、障碍物评价因子、速度评价因子基础上,增加了无人车编队的方向协同因子和队形保持因子.同时,基于变权重鸽群优化算法对改进动态窗的路径评价函数各系数进行优化.当无人车集群感知到障碍物时,通过改进动态窗算法进行相对位置及速度的自适应协同调整,更好地保证无人车编队避障行驶过程中队形位置的精确性.最后,以3台无人车构成三角形编队避障行驶为例进行仿真验证.仿真结果表明基于改进动态窗和变权重鸽群优化算法的无人车编队在规避障碍物时,队形位置偏差相对较小.可见,本文提出的改进算法能够使得无人车集群在规避障碍物过程中提高动态编队的稳定性和精确性.

关键词：无人车鸽群优化动态窗口法协同编队避障控制

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基于修正幂律指数递减的致密气井产能评价新方法

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石油化工应用 2022年第6期41卷 11-15,20页

作者：孙召勃中国海洋石油国际有限公司北京100029

致密气是我国天然气勘探开发的重要新领域之一,目前已经有许多致密气井投产,并积累了大量的气井试采动态数据。本文以有效分析致密气井现场试采数据进而指导气井下一步的生产为目标,研究气井不同渗流阶段瞬时递减率的变化规律,对常规气... 详细信息

致密气是我国天然气勘探开发的重要新领域之一,目前已经有许多致密气井投产,并积累了大量的气井试采动态数据。本文以有效分析致密气井现场试采数据进而指导气井下一步的生产为目标,研究气井不同渗流阶段瞬时递减率的变化规律,对常规气井幂律指数递减模型进行分段修正,引入直线段特征线分析方法,并给出了这种分析方法在致密气藏多段压裂水平井中应用的理论依据,将原来毫无章法的散点拟合求参变为直线拟合求参。研究表明,通过对产量的分阶段评价,降低了原有方法进行产能预测时极易出现的多解性问题;致密气井前期产量递减规律为修正幂律递减模式,后期为双曲递减模式。

关键词：致密气修正幂律指数递减流动阶段产能评价

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Winter-Spring Precipitation Variability in Pakistan

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American Journal of Climate Change 2015年第1期4卷 115-139页

作者： Iftikhar Ahmad Romana Ambreen zhaobo sun Weitao Deng Department of Geography University of Balochistan Quetta Pakistan Key Laboratory of Meteorological Disaster Ministry of Education Nanjing University of Information Science & Technology Nanjing China

This study investigates the spatial-temporal variability of winter-spring (February-March-April) precipitation (WSP) in Pakistan over the period of 1961-2006 by making use of Empirical Orthogonal Function (EOF). The EOF analysis is based on ground observed data, reanalysis NCEP/NCAR of various geopotential heights and NOAA extended reconstructed sea surface temperatures (ERSST.v3). The significant modes are obviously variable at interannual time scale. The leading mode shows the node of maximum spatial variability anchored over the Peshawar Valley and Azad Kashmir (PVAK) axis. The pattern is associated with strong (weak) westerly jet over the Middle East. The pattern is also found closely associated with post monsoon and early winter El Nino. The Nino4 index can be an appropriate predictor for the first consistent single node pattern. The second significant mode represents a tripole pattern with areas of prominent variability over northwestern Pakistan, Quetta-Kalat region and northeastern Punjab. The pattern is found to be pro-NAO and in relation to this pattern, warm and stable SST anomalies appearing in the southern mid-latitudes of Indian and Atlantic basins.

关键词： Pakistan Winter-Spring Precipitation EOF Spatial Variability Interannual Variability

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Spatial-Temporal Variations in January Precipitation over the Period of 1950-2000 in Pakistan and Possible Links with Global Teleconnections: Geographical Perspective

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American Journal of Climate Change 2014年第4期3卷 378-387页

作者： Iftikhar Ahmad Romana Ambreen Shahzad Sultan zhaobo sun Weitao Deng Department of Geography University of Balochistan Quetta Pakistan Pakistan Meteorological Department Islamabad & Institute of Space and Earth Information Science Chinese University of Hong Kong Hong Kong China Key Laboratory of Meteorological Disaster Ministry of Education Nanjing University of Information Science & Technology Nanjing China

Empirical Orthogonal Function (EOF) was performed to investigate spatial variation in January precipitation over Pakistan using ground observed mean monthly precipitation data from 1950-2000 with a combination of gridded reanalysis data of sea level pressure (SLP) and 500 hPa geopotential height. The leading EOF mode captures 37.51% of the total variance and the spatial-temporal variability of January precipitation was consistent in the study area. The temporal changes explicate non-periodic interannual variability and some tacit interdecadal variation. The anomalous condition is more prominent along the western bordering mountains and northern high mountainous region than any other region of Pakistan. Based on results the study reveals spatial-temporal variation in January precipitation and possible links with global teleconnections located both in the proximity as well as in the remote areas from the study locus.

关键词： Pakistan January Precipitation EOF Analysis Spatial-Temporal Variability

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Spatial-Temporal Variations in January Temperature in Pakistan and Their Possible Links with SLP and 500-hPa Levels over the Period of 1950-2000: A Geographical Approach

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Atmospheric and Climate Sciences 2014年第4期4卷 524-533页

作者： Iftikhar Ahmad Romana Ambreen Shahzad Sultan zhaobo sun Weitao Deng Department of Geography University of Balochistan Quetta Pakistan Key laboratory of Meteorological Disaster Ministry of Education Nanjing University of Information Science & Technology Nanjing China Pakistan Meteorological Department Islamabad Pakistan

By making use of Empirical Orthogonal Function (EOF) analysis the spatial and temporal variability was investigated in January over the period of 1950 to 2000 in Pakistan. The analysis is based on the combination of ground observed mean monthly temperature data and National Centre for Environmental Prediction (NCEP) reanalysis data of sea level pressure (SLP) and 500-hPa fields. The results reasonably reveal that the variation in January temperature have links with global teleconnections at SLP and 500-hPa pressure heights. The analysis shows variability at interannual to interdecadal time scale. The interannual variation is more prominent than the interdecadal signal of temperature anomaly. The simulated coefficient patterns show reasonable variation with regional detail from south (north) to north (south) in the study area. The study could be useful as baseline information for climate change studies in Pakistan.

关键词： Pakistan January Temperature Interannual Variability Spatial Variations Empirical Orthogonal Function

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Regional Characteristics of Temperature Anomalies in Pakistan with Emphasis on Spatial Distribution at Decadal Scale: A Case Study of August (1950s-2000s)

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Atmospheric and Climate Sciences 2014年第4期4卷 721-726页

作者： Iftikhar Ahmad Romana Ambreen Shahzad Sultan zhaobo sun Muhammad Nawaz Department of Geography University of Balochistan Quetta Pakistan Pakistan Meteorological Department Islamabad Pakistan Institute of Space and Earth Information Science Chinese University of Hong Kong Hong Kong China Nanjing University of Information Science and Technology Nanjing China

In this paper the month of August was assessed from 1950s-2000s based on the temperature data from 53 stations that covers almost all Pakistan. The temperature coefficient has been calculated by making use of linear regression. The results have been mapped that show considerable variability of temperature at decadal scale in different areas of Pakistan. The rugged terrains especially and rest of Pakistan generally reflect significant temperature variability in the decades of 1950s, 1960s, 1970s, 1980s, 1990s and 2000s as well. This change in temperature varies from region to region and decade to decade in Pakistan. The temperature anomalies achieved in the country are complicated at local level and did not follow the simple perception that winter months are warming and summer months are cooling. In this study, a geographical approach has been adopted to explain the spatial-temporal dynamics of temperature variation over the study period in Pakistan with emphasis on regional detail.

关键词： Temperature Anomalies August Decadal Scale Spatial Distribution Pakistan

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A Study of Decadal December Temperature Variability in Pakistan

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American Journal of Climate Change 2014年第5期3卷 429-437页

作者： Romana Ambreen Iftikhar Ahmad Shahzad Sultan zhaobo sun Muhammad Nawaz Department of Geography University of Balochistan Quetta Pakistan Pakistan Meteorological Department Islamabad Pakistan Institute of Space and Earth Information Science Chinese University of Hong Kong Hong Kong China Nanjing University of Information Science and Technology Nanjing China

The spatial distribution of December temperature in Pakistan has been assessed by statistical method based on mean monthly data from 51 ground stations. The analysis is performed at decadal scale over the period of 1950-2000. December is one of the representative months of winter season in Pakistan, the country with subtropical location and complex rugged terrains, plateaus and plains. The results support a slight rising temperature trend in December. However, this change in temperature varies from region to region as well as from decade to decade and reflects a complicated spatial-temporal structure of temperature anomalies. The assessment shows that the temperature anomalies in different national territories at local scale do not follow the assumption that winter months are warming in northern hemisphere. Both the isothermal shift and temperature anomalies confirm that the mountainous areas of Pakistan face more temperature variability than plains.

关键词： Temperature Anomaly December Pakistan Decadal Scale Spatial Distribution

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冬季北太平洋风暴轴垂直结构的变化特征及其与我国极端低温事件的关系

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大气科学 2016年第2期40卷 401-410页

作者：王超孙照渤王娜南京信息工程大学气象灾害教育部重点实验室南京210044 南京信息工程大学科学学院南京210044 山东省气候中心济南250000

采用NCEP/NCAR和ERA-40再分析资料,对比分析了冬季垂直尺度上北太平洋风暴轴的时空演变特征,揭示了北太平风暴轴垂直结构具有显著年际变化特征。冬季北太平洋风暴轴垂直结构主要呈现出全区一致、上下反相两种分布型,细分为全区一致增强... 详细信息

采用NCEP/NCAR和ERA-40再分析资料,对比分析了冬季垂直尺度上北太平洋风暴轴的时空演变特征,揭示了北太平风暴轴垂直结构具有显著年际变化特征。冬季北太平洋风暴轴垂直结构主要呈现出全区一致、上下反相两种分布型,细分为全区一致增强型、全区一致减弱型、上层增强下层减弱型和上层减弱下层增强型。研究表明:冬季北太平洋风暴轴的垂直结构与我国极端低温事件的关系密切,风暴轴呈全区一致增强(全区一致减弱)型垂直结构时,我国整体区域极端低温频次偏少(多);风暴轴呈上层增强下层减弱(上层减弱下层增强)型垂直结构时,我国东北地区极端低温频次偏多(少),其余地区偏少(多)。

关键词：北太平洋风暴轴垂直结构极端低温

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冬季太平洋SSTA对北太平洋风暴轴年际变化的影响(英文)

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Advances in Atmospheric Sciences 2001年第5期18卷 1029-1042页

作者：朱伟军孙照渤周兵 Nanjing Institute of Meteorology LASG Institute of Atmospheric Physics Chinese Academy of Sciences

Investigation is conducted of the interannual variability of the northern Pacific storm track and its concurrent association with 500 hPa height and Pacific sea surface temperature (SST) during winter. Evidence suggests that during the studying period the center of the northern winter Pacific storm track experiences substantial interannual variability in the variation of its latitude, longitude and intensity. Singular value decomposition (SVD) of 15 winter 500 hPa filtered geopotential height variance over the storm track with the tropical and northern Pacific SST shows that the first coupled mode depicts the effect on the track of SSTA over the equatorial central and eastern Pacific, while the second one reflects the impact of Kuroshio SSTA on the track. Further Composite analysis indicates, moreover, that the SSTA over Kuroshio (equatorial central and eastern Pacific) during winter, which is relative to WP (PNA) teleconnection response pattern in 500 hPa height field, respectively, exerts crucial influence on the interannual variability in vigor and meridianal (zonal) displacement of the track over its central and western (eastern) part.

关键词： storm track interannual variability SVD analysis teleconnection pattern

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