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Correlation of Rainfall Anomalies in Rwanda from September to December (SOND) with Indian Ocean Dipole (IOD) and El Nino Southern Oscillation (ENSO) Events

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Journal of Geoscience and Environment Protection 2024年第6期12卷 115-134页

作者： Frank Rusanganwa Ling Zhang Jonah Kazora Joseph Ndakize Sebaziga Samuel Ekwacu College of Atmospheric Science Nanjing University of Information Science and Technology Nanjing China Rwanda meteorology agency (Meteo-Rwanda) Kigali Rwanda School of Science and Technology University of Rwanda Kigali Rwanda Uganda National Meteorological Authority (UNMA) Kampala Uganda

Understanding the relationship between rainfall anomalies and large-scale systems is critical for driving adaptation and mitigation strategies in socioeconomic sectors. This study therefore aims primarily to investigate the correlation between rainfall anomalies in Rwanda during the months of September to December (SOND) with the occurrences of Indian Ocean Dipole (IOD) and El Nino Southern Oscillation (ENSO) events. The study is useful for early warning and forecasting of negative effects associated with extreme rainfall anomalies across the country, using Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), the National Centers for Environmental Prediction (NCEP) National Center for Atmospheric Research (NCAR) reanalysis sea surface temperature and ERA5 reanalysis datasets, during the period of 1983-2021. Both empirical orthogonal function (EOF), correlation analysis and composite analysis were used to delineate variability, relationship and the related atmospheric circulation between Rwanda seasonal rainfall September to December (SOND) with Indian Ocean Dipole (IOD) and El-Nino Southern Oscillation (ENSO). The results for Empirical Orthogonal Function (EOF) for the reconstructed rainfall data set showed three modes. EOF-1, EOF-2 and EOF-3 with their total variance of 63.6%, 16.5% and 4.8%, Indian ocean dipole (IOD) events resulted to a strong positive correlation of rainfall anomalies and Dipole model index (DMI) (r = 0.42, p value = 0.001, DF = 37) significant at 95% confidence level. The composite analysis for the reanalysis dataset was carried out to show the circulation patterns during four different events correlated with September to December seasonal rainfall in Rwanda using T-test at 95% confidence level. Wind anomaly revealed that there was a convergence of south westerly winds and easterly wind over the study area during positive Indian Ocean Diploe (PIOD) and PIOD with El Nino concurrence event years. The finding of this study will cont

关键词： Correlation Rainfall Anomalies Rwanda Indian Ocean Dipole El Nino Southern Oscillation

Spatial Variation and Trend of Extreme Precipitation in Africa during 1981-2019 and Its Projected Changes at the End of 21^st Century

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Journal of Geoscience and Environment Protection 2024年第3期12卷 192-221页

作者： Fabien Habiyakare Tong Jiang Ibrahim Yahaya Daudi Ndabagenga James Kagabo Buda Su School of Atmospheric Sciences Key Laboratory of Meteorological Disaster of Ministry of Education Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Nanjing China Rwanda meteorology agency (Meteo Rwanda) Kigali Rwanda Institute for Disaster Risk Management/School of Geographical Sciences Nanjing University of Information Science & Technology Nanjing China Department of Geography Gombe State University Gombe State Nigeria

This study comprehensively examines the patterns and regional variation of severe rainfall across the African continent, employing a suite of eight extreme precipitation indices. The analysis extends to the assessment of projected changes in precipitation extremes using five General Circulation Models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6) under four Shared Socioeconomic Pathways (SSPs) scenarios at the long-term period (2081-2100) of the 21st century. Furthermore, the study investigates potential mechanisms influencing precipitation extremes by correlating extreme precipitation indices with oceanic system indices, specifically Ni?o 3.4 for El Ni?o-Southern Oscillation (ENSO) and Dipole Mode Index (DMI) for the Indian Ocean Dipole (IOD). The findings revealed distinct spatial distributions in mean trends of extreme precipitation indices, indicating a tendency toward decreased extreme precipitation in North Africa, Sahel region, Central Africa and the Western part of South Africa. Conversely, West Africa, East Africa and the Eastern part of South Africa exhibit an inclination toward increased extreme precipitation. The changes in precipitation extreme indices indicate a general rise in both the severity and occurrence of extreme precipitation events under all scenarios by the end of the 21st century. Notably, our analysis projects a decrease in consecutive wet days (CWD) in the far-future. Additionally, correlation analysis highlights significant correlation between above or below threshold rainfall fluctuation in East Africa and South Africa with oceanic systems, particularly ENSO and the IOD. Central Africa abnormal precipitation variability is also linked to ENSO with a significant negative correlation. These insights contribute valuable information for understanding and projecting the dynamics of precipitation extreme in Africa, providing a foundation for climate adaptation and mitigation efforts in the region.

关键词： Extreme Precipitation Mann-Kendall Trend Projections Oceanic System Africa

Potential Driving Systems Associated with Extreme Rainfall across East Africa during October to December (OND) Season 2019

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Journal of Geoscience and Environment Protection 2024年第7期12卷 25-49页

作者： Constantine Ingeri Wang Wen Joseph Ndakize Sebaziga Vedaste Iyakaremye Samuel Ekwacu Prosper Ayabagabo Anthony Twahirwa Jonah Kazora School of Atmospheric Sciences Nanjing University of Information Science and Technology Nanjing China Rwanda meteorology agency (Meteo Rwanda) Kigali Rwanda School of Science and Technology University of Rwanda (UR-CST) Kigali Rwanda Climate and Clean Air Coalition Secretariat Paris France Rwanda Environment Management Authority (REMA) Kigali Rwanda Uganda National Meteorological Authority (UNMA) Kampala Uganda Department of Earth and Climate Science University of Nairobi Nairobi Kenya

The East African (EA) region highly experiences intra-seasonal and inter-annual variation in rainfall amounts. This study investigates the driving factors for anomalous rainfall events observed during the season of October-November-December (OND) 2019 over the region. The study utilized daily rainfall data from Climate Hazards Group InfraRed Precipitation with Station Data Version 2 (CHIRPSv2) and the driving systems data. Statistical spatiotemporal analysis, correlation, and composite techniques were performed to investigate the teleconnection between OND 2019 seasonal rainfall and global synoptic climate systems. The findings showed that the OND 2019 experienced seasonal rainfall that was twice or greater than its seasonal climatology and varied with location. Further, the OND 2019 rainfall showed a positive correlation with the Indian Ocean Dipole (IOD) (0.81), Nino 3 (0.51), Nino 3.4 (0.47), Nino 4 (0.40), Pacific Decadal Oscillation (PDO) (0.22), and North Tropical Atlantic (NTA) (0.02), while El Nino-Southern Oscillation (ENSO) showed a negative correlation (−0.30). The region was dominated by southeasterly warming and humid winds that originated from the Indian Ocean, while the geopotential height, vertical velocity, and vorticity anomalies were closely related to the anomalous rainfall characteristics. The study deduced that the IOD was the major synoptic system that influenced maximum rainfall during the peak season of OND 2019. This study therefore provided insights on the diagnosis study of OND 2019 anomalous rainfall and its attribution over the EA. The findings of the study will contribute to improvements in forecasting seasonal rainfall by regional climate centers and national meteorological centers within the region.

关键词： East Africa Driving Climate Systems October-November-December (OND) 2019 Rainfall

Typhoon-and pollution-driven enhancement of reactive bromine in the mid-latitude marine boundary layer

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National Science Review 2024年第4期11卷 93-101页

作者： Shanshan Wang Qinyi Li Ruifeng Zhang Anoop Sharad Mahajan Swaleha Inamdar Nuria Benavent Sanbao Zhang Ruibin Xue Jian Zhu Chenji Jin Yan Zhang Xiao Fu Alba Badia Rafael P.Fernandez Carlos A.Cuevas Tao Wang Bin Zhou Alfonso Saiz-Lopez Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3) Department of Environmental Science and Engineering Fudan University Institute of Eco-Chongming(IEC) Department of Atmospheric Chemistry and Climate Institute of Physical Chemistry Blas CabreraCSIC Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Environment Research Institute Shandong University Centre for Climate Change Research Indian Institute of Tropical MeteorologyMinistry of Earth Sciences Department of Chemistry University of Colorado Boulder Institute of Environment and Ecology Tsinghua Shenzhen International Graduate SchoolTsinghua University Sostenipra Research Group Institute of Environmental Science and Technology(ICTA)Universitat Autonoma de Barcelona(UAB) Institute for Interdisciplinary Science (ICB) National Research Council (CONICET)

Tropospheric reactive bromine is important for atmospheric chemistry,regional air pollution,and global *** studies have reported measurements of atmospheric reactive bromine species in different environments,and proposed their main sources,***-salt aerosol（SSA）,oceanic biogenic activity,polar snow/ice,and *** and other strong cyclonic activities（***） induce abrupt changes in different earth system processes,causing widespread destructive ***,the role of typhoons in regulating reactive bromine abundance and sources remains ***,we report field observations of bromine oxide（BrO）,a critical indicator of reactive bromine,on the Huaniao Island（HNI）in the East China Sea in July *** observed high levels of BrO below 500 m with a daytime average of9.7±4.2 pptv and a peak value of ～26 pptv under the influence of a *** field measurements,supported by model simulations,suggest that the typhoon-induced drastic increase in wind speed amplifies the emission of SSA,significantly enhancing the activation of reactive bromine from SSA *** also detected enhanced BrO mixing ratios under high NOxconditions（ppbv level） suggesting a potential pollution-induced mechanism of bromine release from *** elevated levels of atmospheric bromine noticeably increase ozone destruction by as much as ～40% across the East China *** the high frequency of cyclonic activity in the northern hemisphere,reactive bromine chemistry is expected to play a more important role than previously thought in affecting coastal air quality and atmospheric oxidation *** suggest that models need to consider the hitherto overlooked typhoon-and pollution-mediated increase in reactive bromine levels when assessing the synergic effects of cyclonic activities on the earth system.

关键词： reactive bromine atmospheric chemistry marine boundary layer atmospheric oxidation capacity marine emission

Use of Targeted Orographic Smoothing in Very High Resolution Simulations of a Downslope Windstorm and Rotor in a Sub-tropical Highland Location

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Advances in Atmospheric Sciences 2023年第11期40卷 2043-2062页

作者： Peter SHERIDAN Anlun XU Jian LI Kalli FURTADO Met Office ExeterEX13PBUK Dali National Climate Observatory Dali 671003China State Key Laboratory of Severe Weather and Institute of Tibetan Plateau meteorology Chinese Academy of Meteorological SciencesBeijing 100081China National Environment agency Singapore

Nested simulations of a downslope windstorm over Cangshan mountain,Yunnan,China,have been used to demonstrate a method of topographic smoothing that preserves a relatively large amount of terrain detail compared to typical smoothing procedures required for models with terrain-following grids to run *** simulations were carried out using the Met Office Unified Model(MetUM)to investigate downslope *** smoothing method seamlessly blends two terrain datasets to which uniform smoothing has been applied—one with a minimum of smoothing,the other smoothed more heavily to remove gradients that would cause model *** latter dataset dominates the blend where the steepest slopes exist,but this is localised and recedes outside these *** a result,increased detail is starkly apparent in depictions of flow simulated using the blend,compared to one using the default *** includes qualitative flow details that were absent in the latter,such as narrow shooting flows emerging from roughly 1-2 km wide leeside *** separation is more common due to steeper lee *** use of targeted smoothing also results in increased lee side temporal variability at a given point during the windstorm,including over flat ***-/high-pass filtering of the wind perturbation field reveals that relative spatial variability above 30 km in scale(reflecting the background flow)is similar whether or not targeting is *** this scale,when smoothing is targeted,relative flow variability decreases at the larger scales,and increases at lower *** seems linked to fast smaller scale flows disturbing more coherent flows(notably an along-valley current over Erhai Lake).Spatial variability of winds in the model is unsurprisingly weaker at key times than is observed across a local network sampling mesoscale variation,but results are compromised due to relatively few observation locations sampling the *** when targeted smoothing is applied doe

关键词： lee wave turbulence mountain Tibetan Plateau aviation flow separation Foehn complex terrain

Control of the Dust Vertical Distribution over Western Africa by Convection and Scavenging

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Journal of Atmospheric Science Research 2024年第1期7卷 19-39页

作者： H.Senghor R.Pilon B.Diallo J.Escribano F.Hourdin J.Y.Grandpeix O.Boucher M.Gueye A.T.Gaye E.Machu National agency of Civil Aviation and meteorology PO BOX 8184Senegal Laboratory for Atmospheric-Oceanic Physics-Simeon Fongang Cheikh Anta Diop UniversityDakar10700Senegal Laboratory of Dynamic meteorology(LMD) CNRS/IPSL/UMPCParis75231France Atmospheric Composition Group Barcelona Supercomputing Center(BSC)Barcelona08034Spain Spatial and Physical Oceanography Laboratory(LOPS) Brest UniversityCNRSIRDPlouzane29280France Department of Mathematics and Computer Science University of Sine Saloum El Hadj Ibrahima NiassePO BOX 55KaolackSenegal

Saharan dust represents more than 50%of the total desert dust emitted around the globe and its radiative effect significantly affects the atmospheric circulation at a continental *** studies on dust vertical distribution and the Saharan Air Layer(SAL)showed some shortcomings that could be attributed to imperfect representation of the effects of deep convection and *** authors investigate here the role of deep convective transport and scavenging on the vertical distribution of mineral dust over Western *** multi-year(2006-2010)simulations performed with the variable-resolution(zoomed)version of the LMDZ climate *** are compared with aerosol amounts recorded by the Aerosol Robotic Network(AERONET)and with vertical profiles of the Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)*** allows a thorough examination of the respective roles of deep convective transport,convective and stratiform scavenging,boundary layer transport,and advection processes on the vertical mineral dust distribution over Western *** comparison of simulated dust Aerosol Optical Depth(AOD)and distribution with measurements suggest that scavenging in deep convection and subsequent re-evaporation of dusty rainfall in the lower troposphere are critical processes for explaining the vertical distribution of desert *** processes play a key role in maintaining a well-defined dust layer with a sharp transition at the top of the SAL and in establishing the seasonal cycle of dust *** vertical distribution is further reshaped offshore in the Inter-Tropical Convergence Zone(ITCZ)over the Atlantic Ocean by marine boundary layer turbulent and convective transport and wet deposition at the surface.

关键词： Dust Vertical distribution Sahara Sahel West Africa Climate model Convection Scavenging ITCZ

Environmental Conditions Determining the Timing of the Lifetime Maximum Intensity of Tropical Cyclones over the Western North Pacific and Their Frequency of Occurrence

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Journal of Tropical meteorology 2022年第1期28卷 1-11页

作者：秦晓昊山口宗彦碓氷典久广濑成章 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 China Department of Applied meteorology Meteorological Research InstituteJapan Meteorological AgencyTsukubaIbaraki 305-0052 Japan Department of Atmosphere Oceanand Earth System Modeling ResearchMeteorological Research InstituteJapan Meteorological AgencyTsukubaIbaraki 305-0052 Japan

Environmental conditions determining the timing of the lifetime maximum intensities of tropical cyclones(TCs)are investigated for the TCs over the western North Pacific during the period *** results show that the land controls the timings of the lifetime maximum intensities in 42% of the TCs over this basin,indicating that accurate track forecasts are beneficial for TC intensity *** respect to other TCs that are not affected by the land(i.e.,Ocean-TCs),the timings of their lifetime maximum intensities are determined by multiple oceanic *** particular,interactions between TCs and cold-core eddies occur in a large proportion(nearly 60%)of Ocean-TCs at or shortly after the times of their lifetime maximum intensities,especially in strong TCs(categories 4 and 5),suggesting that a consideration of the above interactions is necessary for improving TC intensity forecasting *** addition,unfavorable oceanic heat content conditions become common as the latitude increases over 25°N,influencing half of the *** vertical wind shear contributes detrimentally to the atmospheric environment in 17% of the TCs over this basin,especially in moderate and weak *** contrast,neither the maximum potential intensity nor the humidity in the middle level of the atmosphere plays dominant roles when TCs turn from their peak intensities to weakening.

关键词： environmental conditions lifetime maximum intensity tropical cyclones frequency of occurrence

Malaria and Climate Variability in Two Northern Stations of Nigeria

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American Journal of Climate Change 2022年第2期11卷 59-78页

作者： Ademola Akinbobola Sunusi Hamisu Department of meteorology and Climate Science Federal University of Technology Akure Nigeria Nigeria Meteorological agency Abuja Nigeria

Malaria is a significant public health problem in Nigeria. The prevalence of malaria incidence across regions in Nigeria can be linked to climatic and environmental factors. This study explored what and how local weather/climate variability impact on malaria prevalence in Jos, North central and Kano, North western Nigeria. Data on monthly malaria cases from 1997 to 2018 were obtained from the hospital archives and consulting room record books. The Kano hospital is the Abdullahi Wase Specialist Hospital, a standard state government hospital that is situated in the Centre of the city. Also, same data were collected from the Plateau state general hospital, Jos. Local weather factors including rainfall, relative humidity, minimum and maximum temperature were considered in the analyses. Time series analyses were applied to evaluate the associations of malaria incidence with weather/climate factors. The results showed that malaria incidence was associated with local weather factors in Jos and Kano but at different lag times and in directions. The results reveal local weather factors strongly affect malaria occurrence in Jos than Kano. The location-specific approaches seem to be one of the keys to minimizing the potential impacts of climate change and maximizing the effects of control and prevention programs in these stations. Therefore, for effective malaria control, interventions could be synchronized with some important climatic predictors of the disease for greater impact and reduce the prevalence of the disease especially in Jos.

关键词： Malaria Weather Climate Plasmodium Time Series

The development of a powerful Mongolian cyclone on 14-15 March 2021:Eddy energy analysis

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Atmospheric and Oceanic Science Letters 2022年第6期15卷 42-49页

作者： Cholaw Bueh Anran Zhuge Zuowei Xie Mei Yong Gomboluudev Purevjav International Center for Climate and Environment Sciences Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Geographical Science Inner Mongolia Normal University HohhotChina Inner Mongolia Key Laboratory of Remote Sensing&Geography Information System Inner Mongolia Normal UniversityHohhotChina Information and Research Institute of meteorology Hydrology and EnvironmentNational Agency for Meteorology and Environmental MonitoringJuulchinhy gudamj-5UlaanbaatarMongolia

2021年3月14-15日,强蒙古气旋引起的大范围强沙尘天气袭击了蒙古国和中国北方地区.本文从高频涡动能量学的角度分析了这一超强气旋的发展过程.2021年3月初,加强的极涡向中亚伸入,并与横跨东亚和东北亚的一个大型脊协同作用,由此形成了... 详细信息

2021年3月14-15日,强蒙古气旋引起的大范围强沙尘天气袭击了蒙古国和中国北方地区.本文从高频涡动能量学的角度分析了这一超强气旋的发展过程.2021年3月初,加强的极涡向中亚伸入,并与横跨东亚和东北亚的一个大型脊协同作用,由此形成了从中亚到贝加尔湖地区的强大斜压带.在这一有利的低频环流条件下,3月13日一个移动性小槽越过萨彦岭后触发了蒙古气旋.850 hPa涡旋动能的下传在气旋的加强和成熟阶段起到了关键作用.而这一机制主要由冷锋后侧的冷空气下沉过程完成.一旦气旋开始快速发展,锋面气旋波机制就变得至关重要.我们强调,高频涡动有效位能是首先从时间平均有效势能中提取能量,然后从低频有效位能中汲取能量而剧烈增长的,这正是该超强气旋的鲜明特征.“北冷南暖”的近地面温度气候异常型为时间平均有效位能的增多和向高频涡动有效位能的转换提供了条件,而“西北冷东南暖”的温度异常型则有利于低频有效位能的增加和向高频涡动有效位能的转换.分析结果表明,高低频波之间的相互作用对蒙古气旋的增强也很重要.

关键词：蒙古气旋沙尘天气动量有效位能锋面气旋波