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PMSE dependence on frequency observed simultaneously with VHF and UHF radars in the presence of precipitation

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Plasma Science and Technology 2018年第11期20卷 61-69页

作者： safi ullah Hailong LI Abdur RAUF Lin MENG Bin WANG Maoyan WANG School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054People＇s Republic of China

Using PMSE （polar mesosphere summer echoes） observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite （GOES） a special condition is shown for the occurrence of rare observed UHF PMSE. When electron flux observed from GOES satellites show a decrease, then after being in the presence of precipitation UHF PMSE occurs. The heating effect on PMSE is small when the UHF electron density is enhanced at 90 km due to particle precipitation. We analyzed and compared the frequency dependence of PMSE under the condition of high energy particle precipitation in July of 2004 and 2007 at well separated frequencies （224 and 930 MHz） at the same site, height, and time. The frequency index varies with height and time. At different heights, the maximum as well as the minimum value of volume reflectivity at VHF is greater than that at UHF with 2 to 3 orders of magnitude. A new qualitative method for the analysis of dust distribution is used by analyzing the relationship between volume reflectivity and frequency index. In agreement with the results of the model it is shown that dust particles of smaller size generally did not occur at the edges, instead they occurred in the middle PMSE regions.

关键词： polar mesosphere summer echoes (PMSE) volume reflectivity ionospheric disturbances

Comparison of the reaction of polar mesosphere winter echoes and polar mesosphere summer echoes to high-frequency heating in terms of modulated characteristics

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Earth and Planetary Physics 2023年第2期7卷 247-256页

作者： safi ullah HaiLong Li Abdur Rauf Shahid ullah Khan Sufyan ullah Khan ShuCan Ge Bin Wang MaoYan Wang Lin Meng School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Department of Physics Riphah International University Islamabad CampusIslamabad 45210Pakistan Department of Physics University of Science and Technology BannuBannu 28101Pakistan National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationQingdao 266107China School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China

In this work,for the first time,we have analyzed and compared the responses of polar mesosphere winter echoes(PMWE)and their summer counterpart,polar mesosphere summer echoes(PMSE),to high-frequency(HF)heating in terms of modulated characteristics(i.e.,backscatter intensity reduction,recovery,and overshoot).Both PMWE and PMSE observations were from the same site(Tromsφ,Norway;69.6°N,19.2°E)and radar(EISCAT[European Incoherent Scatter Scientific Association]very high frequency,224 MHz).The heating patterns of both PMWE and PMSE were found to be similar;however,PMSE was more greatly affected by HF *** mesosphere summer echoes showed recovery and overshoot more frequently than did *** addition,the mean recovery and overshoot of PMSE were greater than those of *** associated electron temperature enhancement was estimated for both PMWE and PMSE and showed that,compared with PMWE,the electron temperature enhancement was more significant in *** strong heating effects on PMSE may be due to the considerable increase in electron temperature.

关键词： polar mesosphere winter echo polar mesosphere summer echo electromagnetic wave heating experiment dusty plasma ionosphere

Projection of precipitation extremes over South Asia from CMIP6 GCMs

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Journal of Arid Land 2023年第3期15卷 274-296页

作者： Adnan ABBAS Asher S BHATTI safi ullah Waheed ullah Muhammad WASEEM ZHAO Chengyi DOU Xin Gohar ALI Land Science Research Center Nanjing University of Information Science&TechnologyNanjing 210044China Department of Geology Bacha Khan UniversityCharsadda 24420Pakistan Department of Atmospheric and Oceanic Sciences/Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Center of Excellence in Water Resources University of Engineering and TechnologyLahore 54890Pakistan Pakistan Meteorological Department Sector H-8/2Islamabad 44000Pakistan

Extreme precipitation events are one of the most dangerous hydrometeorological disasters,often resulting in significant human and socio-economic losses *** is therefore important to use current global climate models to project future changes in precipitation *** present study aims to assess the future changes in precipitation extremes over South Asia from the Coupled Model Intercomparison Project Phase 6(CMIP6)Global Climate Models(GCMs).The results were derived using the modified Mann-Kendall test,Sen's slope estimator,student's t-test,and probability density function *** extreme precipitation indices were assessed,including wet days(RR1mm),heavy precipitation days(RR10mm),very heavy precipitation days(RR20mm),severe precipitation days(RR50mm),consecutive wet days(CWD),consecutive dry days(CDD),maximum 5-day precipitation amount(RX5day),and simple daily intensity index(SDII).The future changes were estimated in two time periods for the 21^(st) century(i.e.,near future(NF;2021-2060)and far future(FF;2061-2100))under two Shared Socioeconomic Pathway(SSP)scenarios(SSP2-4.5 and SSP5-8.5).The results suggest increases in the frequency and intensity of extreme precipitation indices under the SSP5-8.5 scenario towards the end of the 21^(st) century(2061-2100).Moreover,from the results of multimodel ensemble means(MMEMs),extreme precipitation indices of RR1mm,RR10mm,RR20mm,CWD,and SDII demonstrate remarkable increases in the FF period under the SSP5-8.5 *** spatial distribution of extreme precipitation indices shows intensification over the eastern part of South Asia compared to the western *** probability density function of extreme precipitation indices suggests a frequent(intense)occurrence of precipitation extremes in the FF period under the SSP5-8.5 scenario,with values up to 35.00 d for RR1mm and 25.00-35.00 d for *** potential impacts of heavy precipitation can pose serious challenges to the study area regarding floodin

关键词： precipitation extremes extreme precipitation indices climate change Coupled Model Intercomparison Project 6(CMIP6) Global Climate Model(GCM) South Asia

Exploring the occurrence rate of PMSE-Es by Digisonde at Tromsø

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Earth and Planetary Physics 2021年第2期5卷 187-195页

作者： HaiLong Li ShuCan Ge Lin Meng MaoYan Wang Abdur Rauf safi ullah School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationQingdao 266107China School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China

Polar mesosphere summer echoes(PMSE)are observed simultaneously with Digisonde and EISCAT VHF *** phenomenon of irregular Es layers is called PMSE-like or PMSE-Es(Polar Mesosphere Summer Echoes-Es)and has some relationship with real *** this paper,the characteristics of irregular Es layers at 80–100 km were observed by Digisonde at Tromsøduring 2003–2014 are statistically analyzed with *** diurnal,day-to-day and year-to-year variations and discrepancies of occurrence rate between PMSE and PMSE-Es are compared with the statistical results observed by Esrange MST radar(ESRAD),and the reasons are *** results show that the trends in the occurrence rate of PMSE-Es are similar to the trends in the occurrence rate of PMSE,but there are some notable *** occurrence rate of PMSE-Es is much lower than the occurrence rate of *** minimum value of PMSE-Es appears 1–2 hours earlier than the minimum value of the PMSE occurrence rate,while PMSE-Es appear earlier than PMSE in the *** addition,there is a significant positive correlation between the annual average occurrence rates of PMSE and *** is a relatively important occurrence in the polar *** of its characteristics can provide new ideas and methods for studying the formation mechanism of PMSE.

关键词： Polar mesosphere summer echoes Digisonde EISCAT VHF radar PMSE-Es Esrange MST radar

Evolution and customisation of the RegCM model for urban climate studies:Addressing multifaceted challenges and advancing climate science

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Geography and Sustainability 2024年第4期5卷 607-624页

作者： Naushin Yasmin safi ullah Sami G.Al-Ghamdi Biological and Environmental Science and Engineering(BESE)Division Environmental Science and Engineering ProgramKing Abdullah University of Science and Technology(KAUST)23955-6900ThuwalSaudi Arabia KAUST Climate and Livability Initiative King Abdullah University of Science and Technology(KAUST)23955-6900ThuwalSaudi Arabia

The Regional Climate Model(RegCM)proves valuable for climate analysis and has been applied to a wide range of climate change aspects and other environmental issues at a regional *** model also demonstrated success in diverse areas of urban research,including urban heat island studies,extreme climate events analysis,assessing urban resilience,and evaluating urbanization impacts on climate and air ***,more studies have been conducted in utilizing RegCM to address climate change in cities,due to its enhanced ability over the years to capture meteorological phenomena at city ***,there are many challenges associated with its implementation in meso-scale research,which are attributed to various shortcomings and thus create room for further improvement in the *** paper presents a comprehensive overview of the evolution of the RegCM over the years and its customisation across various parameters,demonstrating its versatility in urban climate studies and underscoring the model’s pivotal role in addressing multifaceted challenges in urban *** addressing these aspects,the paper offers valuable insights and recommendations for researchers seeking to enhance the accuracy and efficacy of urban climate simulations using the RegCM system,thereby contributing to the advancement of urban climate science and sustainability.

关键词： RegCM Urban climate Air quality Urban heat island effect Urban design Climate extremes

Effect of ions on conductivity and permittivity in the Polar Mesosphere Summer Echoes region

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Earth and Planetary Physics 2021年第2期5卷 196-204页

作者： safi ullah HaiLong Li Abdur Rauf Lin Meng Bin Wang ShuCan Ge MaoYan Wang School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Terahertz Science and Technology Key Laboratory of Sichuan Province Chengdu 610054China National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationQingdao 266107China School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China

For the first time,the effect of ions on complex conductivity and permittivity of dusty plasma at Polar Mesosphere Summer Echoes(PMSE)altitude is *** of ions higher mass and smaller thermal velocity,generally,their effects are not considered in the study of electromagnetic properties of dusty *** this study,we modified the equations of conductivity and permittivity by adding the effect of *** the PMSE altitude region between 80 and 90 km,a local reduction in electron density(i.e.,an electron biteout),is produced by electron absorption onto dust *** bite-out condition contains high dust density and smaller electron *** simulation results in comparatively strong bite-out conditions,we found that the ion effects on conductivity become significant with smaller dust size,lower electron temperature,and lower neutral *** comparatively weak bite-out conditions,the ion effects on conductivity become significant with larger dust size,higher electron temperature,and higher neutral *** the other hand,for different dust sizes,electron temperatures and neutral density,the ion effects on complex permittivity become significant only in very strong bite-out *** on these simulation results,we conclude that,in the absence of electron bite-out conditions,the effect of ions on complex conductivity and permittivity is not significant and can be ***,during bite-out conditions,the effect of ions becomes significant and cannot be ignored because it significantly changes the conductivity and permittivity of dusty plasmas.

关键词： PMSE electromagnetic waves collision and charging effect conductivity and permittivity

Numerical Analysis of Artificial Electron Heating Effects on Polar Mesospheric Winter Echoes

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Journal of Electronic Science and Technology 2020年第3期18卷 287-295页

作者： safi ullah Hai-Long Li Abdur Rauf Lu-Yao Fu Mao-Yan Wang Lin Meng School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054

In this paper,an analytical model is used to analyze the modulated polar mesospheric winter echoes(PMWE).The winter parameters were introduced to simulate the effects of different parameters during the artificial electron heating of *** important role of the charged dust particle in the creation of PMWE is confirmed *** is found that during the heating of PMWE,the increases of the dust size,dust charge,electron temperature,initial electron density,and ion-neutral collision frequency cause the increase of the electron density irregularity,and hence the PMWE ***,with increasing the dust density,the electron density irregularity and the PMWE strength decrease.

关键词： Artificial ionospheric heating electron density irregularities polar mesospheric winter echoes(PMWE) space plasma physics(numerical simulation)

Investigation of PMSE echoes characteristics using the discontinuous EISCAT UHF observation and its relation with space environment

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Advances in Polar Science 2019年第2期30卷 132-138页

作者： Abdur RAUF LI Hailong safi ullah WANG Maoyan MENG Lin School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu 610054 China School of Physics University of Electronic Science and Technology of China Chengdu 610054 China

The observations of Polar Mesosphere Summer Echoes (PMSE) were carried out using the sporadic data of EISCAT UHF radar during the summer season from 2004 to 2015. There were 25 h of PMSE echoes with EISCAT UHF radar. PMSE echoes were mostly observed only during the early morning and fore-noon time. Moreover, the PMSE echoes are positively correlated with Lymanα radiation, but the correlation is non-significant. The occurrence of PMSE echoes in the early morning and fore-noon time and there positive correlation with Lymanαradiation suggests that solar radiations might be one important factor for PMSE echoes in this study. Very weak positive, but statistically non-significant correlation is found between PMSE occurrence rate and the local geomagneticK-indices. It is found that there is a matching between the variation in the occurrence rate of PMSE and noctilucent clouds (NLC) up to some extent and they are positively correlated. This positive correlation might support the earlier proposed idea about the role of ice particle size in producing PMSE echoes at higher frequencies.

关键词： PMSE echoes geomagnetic indices EISCAT UHF radar

On the radar frequency dependence of polar mesosphere summer echoes

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Earth and Planetary Physics 2020年第6期4卷 571-578页

作者： ShuCan Ge HaiLong Li Lin Meng MaoYan Wang Tong Xu safi ullah Abdur Rauf Abdel Hannachid School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China National Key Laboratory of Electromagnetic Environment China Research Institute of Radio Wave PropagationQingdao 266107China Department of Meteorology Stockholm UniversitySE-106-91StockholmSweden

Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local *** we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter(EISCAT)heating equipment simultaneously with very high frequency(VHF)radar and ultra high frequency(UHF)radar on 12 July *** to the experimental observations,the PMSEs occurrence rate at VHF was much higher than that at UHF,and the altitude of the PMSEs maximum observed at VHF was higher than that at *** regions were observed by VHF radar between high energetic particle precipitation and the *** addition,highfrequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle *** addition,an updated qualitative method was used to study the relationship between volume reflectivity and *** volume reflectivity was found to be inversely proportional to the fourth power of radar *** theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.

关键词： Polar mesosphere summer echoes artificial electron heating volume reflectivity energetic particle precipitation