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diurnal variations of Summer Precipitation in the Beijing Area and the Possible Effect of Topography and Urbanization

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Advances in Atmospheric Sciences 2011年第4期28卷 725-734页

作者：殷水清李维京 Deliang CHEN Jee-Hoon JEONG 郭文利 State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University Beijing 100875 School of Geography Beijing Normal University Beijing 100875 Beijing Climate Center China Meteorological Administration Beijing 100081 Department of Earth Sciences University of Gothenburg Gothenburg 40530 Sweden Beijing Regional Climate Center Beijing Meteorological Bureau Beijing 100089

The present study examined the diurnal variations of summer precipitation in the Beijing area by usingsubdaily precipitation and wind observations. A combined effect of topography and urbanization on thecharacteristics of diurnal variations was suggested. It was shown that stations located in the plain areaexhibited typical night rain peaks, whereas those in the mountainous area exhibited clear afternoon peaks ofprecipitation diurnal variations. The precipitation peaks were associated with wind fields around the Beijingarea, which were found to be highly modulated by mountain-valley circulation and urban-country circulation.The lower-tropospheric wind exhibited a clear diurnal shift in its direction from north at 0800 LST to southat 2000 LST, which reflected mountain-valley circulation. The transitions from valley to mountain windand the opposite generally happened after sunset and sunrise, respectively, and both occurred earlier for thestations located closer to mountains. By comparing the diurnal variations of precipitation at stations in anortheast suburb, an urban area, and a southwest suburb, it was revealed that the northeast suburb grouphad the highest normalized rainfall frequency, but the southwest group had the lowest from late afternoon tolate evening. On the contrary, in the early morning from about 0200 to 1000 LST, the southwest group andurban group had the highest normalized rainfall frequency. This pattern might originate from the combinedeffects of mountain-valley topography and urbanization.

关键词： diurnal variations precipitation mountain-valley circulation urban effect Beijing area

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diurnal variations of Precipitation during the Warm Season over China:1954-2001

Diurnal Variations of Precipitation during the Warm Season o...

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作者：殷水清 School of Geography Beijing Normal UniversityKey Laboratory of Environmental Change and Natural DisasterMinistry of Education Earth Sciences Centre Gothenburg UniversityGothenburgSweden

The spatial distribution and seasonal change of diurnal variations of precipitation during the warm season(May to September) over China were analyzed using 48-year hourly data from 62 rain gauges during 1954-2001.Nocturnal precipitation predominates for the stations over the Tibetan Plateau as well as in southwest and northwest China.For stations to the east of about 110°E,daytime precipitation predominates in the northern and southern part,whereas nocturnal precipitation predominates in the middle and lower reaches of the Yangtze River and the North China Plain.Further,the magnitude of diurnal variations first decreases and then increases from the south toward the north.The significant diurnal variations in vertical circulation(stronger during the day and weaker at night),the meso-local-scale mountain-valley winds,and the nighttime cooling of cloud tops could be the processes behind the nocturnal rain in the western part of China(to the west of about 11 CPE).Daytime precipitation in the eastern part of China(to the east of about 110°E) could be attributed to the moist convection connected with solar heating.The morning peaks for stations in the middle and lower reaches of the Yangtze River and the North China Plain seem to be connected with the advance and retreat of the East Asian summer monsoon.The morning maxima at coastal stations may be mainly attributed to the local land-sea breeze.The seasonal changes of the diurnal variations for the western part of China are relatively small,with nighttime precipitation maxima remaining fairly constant during the warm season.This part is not directly influenced by the monsoon.For most of the stations in the eastern part,the morning peaks tend to be strengthened/weakened along with the East Asian monsoon’s advancing/retreating.

关键词： precipitation diurnal variations China warm season the East Asian summer monsoon

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diurnal variations of Precipitation over the South China Sea Using TRMM Observations

Diurnal Variations of Precipitation over the South China Sea...

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第七次全国动力气象学术会议

作者： Li Weibiao~1 Luo Cong~1 Wang Dongxiao~2 Lei Ting~1 and Liu Zijie~1 1.Department of Atmospheric Sciences,Sun Yat-Sen University,Guangzhou,510275,China 2.LED,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China

＜正＞In this study,diurnal variations of precipitation and related mechanisms over the South China Sea（SCS）are studied using the TRMM data.We have found that: 1)The precipitation over the SCS has large diurnal variations with considerable regional features and seasonal variations.diurnal variations are significant all the year around over the southern of the SCS.Over the middle to northern of the SCS,however,diurnal variations are significant only in summer and autumn.Over the northern of the SCS precipitation peaks in early morning,while over the southern of the SCS it has two diumal peaks:one in the early morning and another in the late afternoon. 2)The diurnal variations of precipitation over the SCS are related to the activity of the SCS summer monsoon and the ENSO events.The diurnal variations of precipitation over the SCS become much more pronounced.In addition,after the onset of the SCS summer monsoon,the late afternoon precipitation increases remarkably over the northern of the SCS.Moreover,it is interesting to note that the early morning rainfalls are much more significant during La Nina years than those during El Nino years. 3)The land-sea breezeis responsible forthe diurnal cycle over the Kalimantan Island and its offshore area while the"static radiation-convection" mechanisms may result in the early morning rainfall peak over the SCS.

关键词： Precipitation diurnal variations South China Sea

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Formation of Low-Level Jets over Southern China in the Mei-yu Season

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Advances in Atmospheric Sciences 2023年第10期40卷 1731-1748页

作者： Xuanyu LIU Guixing CHEN Sijia ZHANG Yu DU School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityZhuhai 519082China Key Laboratory of Tropical Atmosphere-Ocean System(Sun Yat-sen University) Ministry of EducationZhuhai 519082China

This study examines the diversity of low-level jet(LLJ)formation and related physical processes over southern China.A total of 171 LLJ formation events with enhanced daily southwesterlies and early-morning maximum wind speeds were observed during the mei-yu seasons of 1989–2018.The LLJs can be further categorized into four types based on the increases in the daily mean and diurnal amplitude of the low-level winds.Analysis of the synoptic-scale disturbances shows that the two types of LLJ formation(Q1 and Q4),which feature large increases of daily southerly wind components,are mainly induced by west-east dipole patterns of pressure change,in association with the enhanced southwest vortex and/or the western Pacific subtropical high(WPSH).In contrast,the other two types(Q2 and Q3),which feature relatively large increases in their daily westerly components,are related to a northwest-southeast dipole pattern of pressure change due to the mid-latitude trough and the WPSH.We further analyze the considerable variations in the diurnal thermal forcing among the LLJ formation events.The strong(weak)daytime heating of solar radiation leads to relatively large(small)increases in the diurnal amplitude of low-level winds in Q1 and Q2(Q3 and Q4)types.Therefore,different combinations of synopticscale disturbances and diurnal thermal forcings are found to account for the diversity in LLJ formation and associated differences in downstream rainfall patterns.These results help to improve our understanding and prediction of the formation of LLJs.

关键词： low-level jets formation processes diurnal variations synoptic-scale disturbances

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Effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency

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Chinese Physics B 2013年第9期22卷 456-464页

作者：沈新勇庆涛李小凡 Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science and Technology NOAA/NESDIS/Center for Satellite Applications and Research College ParkMaryland 20740USA

The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated us ing grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven without large-scale vertical velocity. The precipitation efficiencies are respectively defined in surface rainfall, cloud, and rain microphysical budgets. We mathematically and physically demonstrate the relationship between these precipitation efficiencies. The 2 ℃ increases in spatiotemporal invariant sea surface temperature （SST） from 27 ℃ to 29 ℃ and from 29 ℃ to 31 ℃, and the inclusion of diurnal SST difference 1 ℃ and the 1℃ increase in diurnal SST difference generate opposite changes in the precipitation efficiency by changing ice cloud-radiation interactions. The radiative and microphysical processes of ice clouds have opposite effects on the precipitation efficiency because of the rainfall increase associated with the reduction in the saturation mixing ratio caused by the exclusion of radiative effects and the decrease in rainfall related to the reduction in net condensation caused by the exclusion of deposition processes. The radiative effects of water clouds on the precipitation efficiency are statistically insensitive to the radiative effects of ice clouds.

关键词： sea surface temperature diurnal variations clouds precipitation efficiency

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Statistical characteristics of ionospheric backscatter observed by SuperDARN Zhongshan radar in Antarctica

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Advances in Polar Science 2013年第1期24卷 19-31页

作者： HU Hongqiao LIU Erxiao LIU Ruiyuan YANG Huigen ZHANG Beichen SOA Key Laboratory for Polar Science Polar Research Institute of China School of Science Xidian University

Zhongshan HF radar, as one component of SuperDARN, has been established and in operation since April, 2010. Using data from the first two years of its operation, this paper investigates the radar＇s performance, the diurnal and seasonal variations o1 ionospheric echoes, and their dependence on geomagnetic activity. Statistical studies show that the occurrence of echoes in different beams varies at different frequencies, which arises from the direction of the beam and the area over which the beam can achieve the orthogonality condition between the wave vector and the Earth＇s magnetic field. The diurnal variation is obvious with double peak structures both in the occurrence rate and average power at 04-08 UT and 16-17 UT. The line-of-sight velocities are mainly positive on the dayside and negative on the nightside for Beam 0, which is the opposite of the trend for Beam 15. The spec- tral widths on the dayside are often higher than those on the nightside owing to the high energy particle precipitation in the cusp region. The seasonal variations are more obvious for those beams with larger numbers. The occurrence, the average power, the line-of-sight velocity, and the spectral widths are generally larger in the winter months than in the summer months. The influence of geomagnetic activity on radar echoes is significant. The peak echo occurrence appears on the dayside during geomagnetically quiet times, and shifts toward the nightside and exhibits an obvious decrease with increasing Kp. With increasing geomagnetic activity, the line-of-sight velocities increase, whereas the spectral widths decrease. The frequency dependence is investigated and it is found that in the operating frequency bands in 2010, 9-10 MHz is the most appropriate band for the SuperDARN Zhongshan radar.

关键词： SuperDARN Zhongshan radar diurnal variations seasonal variations geomagnetic activity dependence frequency dependence

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diurnal Variation of Tropical Cyclone Rainfall in the Western North Pacific in 2008-2010

Diurnal Variation of Tropical Cyclone Rainfall in the Wester...

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创新驱动发展提高气象灾害防御能力——第30届中国气象...

作者： SHU Hai-Long ZHANG Qing-Hong XU Bin Laboratory for Climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking University Meteorological Observatory Department of TechnologyBaicheng Ordnance Test Center of China National Meteorological Information Center China Meteorological Administration

diurnal variation of tropical cyclone （TC） rainfall in the western North Pacific （WNP） is investigated using the high-resolution Climate Prediction Center’s morphing technique （CMORPH） products obtained from the National Oceanic and Atmospheric Administration （NOAA）.From January 2008 to October 2010,72 TCs and 389 TC rainfall days were reported by the Joint Typhoon Warning Center’s （JTWC） best-track record.The TC rain rate was partitioned using the Objective Synoptic Analysis Technique （OSAT） and interpolated into Local Standard Time （LST）.Harmonic analysis was applied to analyze the diurnal variation of the precipitation.Obvious diurnal cycles were seen in a 1 pproximately 70% of the TC rainfall days.The harmonic amplitude and phase of the mean TC rainfall rate vary with TC intensity,life stage,season,and spatial distribution.On the basis of intensity,tropical depressions （TDs） exhibit the highest precipitation variation amplitude （PVA）,at approximately 30%,while super typhoons （STs） contain the lowest PVA,at less than 22%.On the basis of lifetime stage,the PVA in the decaying stage （more than 37%） is stronger than that in the developing （less than 20%） and sustaining （28%） stages.On the basis of location,the PVA of more than 35% （less than 18%） is the highest （lowest） over the high-latitude oceanic areas （the eastern ocean of the Philippine Islands）.In addition,a sub-diurnal cycle of TC rainfall occurs over the high-latitude oceans.On the basis of season,the diurnal variation is more pronounced during summer and winter,at approximately 30% and 32%,respectively,and is weaker in spring and autumn,at approximately 22% and 24%,respectively.

关键词： Western North Pacific Tropical cyclones precipitation diurnal variations

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