下垫面对郑州城市强降水的影响:城市化及地形影响的数值模拟研究
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摘要
利用WRF-ARW中尺度区域数值模式耦合单层城市冠层模式(slab-UCM),采用ERA-interim 0.5°×0.5°再分析资料作为初始场和边界条件,对2016年6月5日郑州地区发生的一次强对流天气进行模拟,并通过改变下垫面的土地利用类型与地形高度数据设置敏感性试验,探究了城市化及郑州西北部山脉地形对对流性强降水过程的影响。结果表明:1)此次强降水过程主要受高层的低槽系统影响,前期的对流不稳定层结为对流触发提供了有利的热力条件;2)城市热岛效应能够改变下垫面的热力状况,有利于在城市地区激发更强的上升运动,使降水向城区集中;3)郑州西北侧山脉激发的重力波能够使郑州地区对流增强;4)山脉能够阻挡低层干空气向郑州地区输送,因此山脉高度的削减造成郑州地区低层相对湿度减小,使雨滴蒸发冷却增强,进而导致与降水相联系的冷池的增强,雨带移速加快,进一步导致累积降水的减少。
Based on the 0. 5°×0. 5° ERA-interim reanalysis data,a heavy rainfall event that occurred on June 5,2016 in Zhengzhou w as simulated using the Advanced Research Weather Research and Forecasting M odel( WRF-ARW)coupled w ith a slab urban canopy model( UCM). Sensitivity experiments w ith the modified land-use categories and terrain height are conducted to investigate the impacts from urbanization and topography of the mountain to the northw est of Zhengzhou on this heavy rainfall event.The conclusions can be summarized as follow s:1) The results show that the severe rainfall events are mainly favored by the ageostrophic-forced ascending motion associated w ith an eastw ard-migrating upper-level trough and the unstable convective stratification in the vicinity of Zhengzhou.2) The precipitation pattern simulated in the control experiment is w ell consistent w ith the observational data.The sensitivity experiment( NO_CITY) in w hich the land-use category of Zhengzhou is changed from urban land to grass features significantly low er rainfall amount in the urban area comparing w ith the control experiment( CTL).Further analysis shows that the urban surface temperature in NO_CITY are clearly decreased comparing to that in CTL since the modified land-use type w eakens the thermodynamical effect of urban surface. The decreased surface temperature in turn suppresses the sensible heat flux and leads to w eak ascent in the center of Zhengzhou.It is indicated that the effect of urban heat island tends to enhance upw ard motion and thus convection in the urban area,w hich increases the rainfall amount and results in the precipitation more concentrated in the city.3) The sensitivity experiment in w hich the mountain to the northw est of Zhengzhou has a reduced orographic height( LOW_M ONT) also show s low er rainfall amount than CTL.The results show that this remarkable difference can be attributed to tw o main factors.Firstly,the gravity w ave excited by the orographic effect can promote the convection in Zhengzhou region and thus increase the rainfall in urban area.The low er the mountain is,the w eaker the gravity w ave excited w ill be. Hence,the convection in Zhengzhou in LOW_M ONT is suppressed,w hich results in a low er rainfall amount. Secondly,through examining the low-level relative humidity field,it is found that the mountain to the northw est of Zhengzhou plays an important role in hampering the northw ard transport of the low-level dry air.Therefore,as the height of the mountain is artificially low ered,a larger amount of low-level dry air is advected northw ards and thus low ers the relative humidity in Zhengzhou region.The decreased low-level relative humidity enhances the evaporation cooling,and thus the cold pool is associated w ith the precipitation.The strong cold pool helps the rain band to move fast. The faster the rain band moves,the less time the rainfall w ill sustain.Therefore,this effect leads to a further decrease in the total rainfall in LOW_M ONT experiment.
Based on the 0. 5°×0. 5° ERA-interim reanalysis data,a heavy rainfall event that occurred on June 5,2016 in Zhengzhou w as simulated using the Advanced Research Weather Research and Forecasting M odel( WRF-ARW)coupled w ith a slab urban canopy model( UCM). Sensitivity experiments w ith the modified land-use categories and terrain height are conducted to investigate the impacts from urbanization and topography of the mountain to the northw est of Zhengzhou on this heavy rainfall event.The conclusions can be summarized as follow s:1) The results show that the severe rainfall events are mainly favored by the ageostrophic-forced ascending motion associated w ith an eastw ard-migrating upper-level trough and the unstable convective stratification in the vicinity of Zhengzhou.2) The precipitation pattern simulated in the control experiment is w ell consistent w ith the observational data.The sensitivity experiment( NO_CITY) in w hich the land-use category of Zhengzhou is changed from urban land to grass features significantly low er rainfall amount in the urban area comparing w ith the control experiment( CTL).Further analysis shows that the urban surface temperature in NO_CITY are clearly decreased comparing to that in CTL since the modified land-use type w eakens the thermodynamical effect of urban surface. The decreased surface temperature in turn suppresses the sensible heat flux and leads to w eak ascent in the center of Zhengzhou.It is indicated that the effect of urban heat island tends to enhance upw ard motion and thus convection in the urban area,w hich increases the rainfall amount and results in the precipitation more concentrated in the city.3) The sensitivity experiment in w hich the mountain to the northw est of Zhengzhou has a reduced orographic height( LOW_M ONT) also show s low er rainfall amount than CTL.The results show that this remarkable difference can be attributed to tw o main factors.Firstly,the gravity w ave excited by the orographic effect can promote the convection in Zhengzhou region and thus increase the rainfall in urban area.The low er the mountain is,the w eaker the gravity w ave excited w ill be. Hence,the convection in Zhengzhou in LOW_M ONT is suppressed,w hich results in a low er rainfall amount. Secondly,through examining the low-level relative humidity field,it is found that the mountain to the northw est of Zhengzhou plays an important role in hampering the northw ard transport of the low-level dry air.Therefore,as the height of the mountain is artificially low ered,a larger amount of low-level dry air is advected northw ards and thus low ers the relative humidity in Zhengzhou region.The decreased low-level relative humidity enhances the evaporation cooling,and thus the cold pool is associated w ith the precipitation.The strong cold pool helps the rain band to move fast. The faster the rain band moves,the less time the rainfall w ill sustain.Therefore,this effect leads to a further decrease in the total rainfall in LOW_M ONT experiment.
引文
Dee D P,Uppala S M,Simmons A J,et al.,2011.The ERA-Interim reanalysis:configuration and performance of the data assimilation system[J].Quart J Roy M eteor Soc,137:553-597.
丁一汇,1994.暴雨和中尺度气象学问题[J].气象学报,52(3):274-284.Ding Y H,1994.Some aspects of rainstorm and mesoscale meteorology[J].Acta Meteor Sinica,52(3):274-284.(in Chinese).
高守亭,周玉淑,冉令坤,2018.我国暴雨形成机理及预报方法研究进展[J].大气科学,42(4):833-846.Gao S T,Zhou Y S,Ran L K,2018.A review on the formation mechanisms and forecast methods for torrential rain in China[J].Chin J Atmos Sci,42(4):833-846.(in Chinese).
Guo X,Fu D,Wang J,2006.M esoscale convective precipitation system modified by urbanization in Beijing city[J].Atmos Res,82:112-126.
Hendricks E A,Peng M S,Ge X,et al.,2011.Performance of a dynamic initialization scheme in the coupled ocean-atmosphere mesoscale prediction system for tropical cyclones(COAM PS-TC)[J].Wea Forecasting,26(5):650-663.
Hong S Y,Noh Y,Dudhia J,2006.A new vertical diffusion package w ith an explicit treatment of entrainment processes[J].M on Wea Rev,134(9):2318-2341.
Hoskins B J,Draghici I,Davies H C,1978.A new look at theω-equation[J].Quart J Roy M eteor Soc,104(439):31-38.
Justice C O,Tow nshend J R G,Vermote E F,et al.,2002.An overview of M ODIS land data processing and product status[J].Remote Sens Environ,83(1/2):3-15.
Kain J S,Fritsch J M,1990.A one-dimensional entraining/detraining plume model and its application in convective parameterization[J].J Atmos Sci,47:2784-2802.
Kiladis G N,1998.Observations of Rossby w aves linked to convection over the eastern tropical Pacific[J].J Atmos Sci,55:321-339.
Kiladis G N,Weickmann K M,1992.Circulation anomalies associated w ith tropical convection during northern w inter[J].M on Wea Rev,120:1900-1923.
孔锋,王一飞,方建,等,2018.中国夏季极端降水空间格局及其对城市化的响应(1961-2010)[J].长江流域资源与环境,27(5):61-75.Kong F,Wang Y F,Fang J et al.,2018.Spatial pattern of summer extreme precipitation and its response to urbanization in China(1961-2010)[J].Res Environ Yang.Basin,27(5):61-75.(in Chinese).
Lin Y L,Farley R D,Orville H D,1983.Bulk parameterization of the snow field in a cloud model[J].J Climate Appl M eteor,22(6):1065-1092.
M iao S G,Chen F,Li Q C,et al.,2011.Impacts of urban processes and urbanization on summer precipitation:a case study of heavy rainfall in Beijing on 1 August 2006[J].J Appl M eteor Climatol,50(4):806-825.
Nastrom G D,Fritts D C,1992.Sources of mesoscale variability of Gravity Waves.Part I:topographic excitation[J].J Atmos Sci,49:101-110.
Skamarock W C,Klemp J B,Dudhia J,et al.,2008.A description of the advanced research WRF version 3.NCAR Tech[R].Note NCAR/TN-4751STR.
沈伟,袁慧玲,陈曦,等,2017.江苏暖季短时强降水的时空不均匀特征分析[J].大气科学学报,40(4):453-462.Shen W,Yuan H L,Chen X,et al.,2017.Temporal and spatial heterogeneity of w arm-season short-time heavy rainfall in Jiangsu Province[J].Trans Atmos Sci,40(4):453-462.(in Chinese).
陶诗言,丁一汇,周晓平,1979.暴雨和强对流天气的研究[J].大气科学,3(3):227-238.Tao S Y,Ding Y H,Zhou X P,1979.The present status of the research on rainstorm and severe convective w eather in China[J].Chin J Atmos Sci,3(3):227-238.(in Chinese).
Wang J,Feng J M,Yan Z W,2015.Potential sensitivity of w arm season precipitation to urbanization extents:modeling study in Beijing-Tianjin-Hebei urban agglomeration in China[J].J Geophys Res Atmos,120(18):9408-9425.
王咏薇,任侠,翟雪飞,等,2016.南京复杂下垫面条件下的三维城市热环境模拟[J].大气科学学报,39(4):525-535.Wang Y W,Ren X,Zhai XF,et al.,2016.Numerical study of the three-dimensional thermal environment over a complex underlying surface in Nanjing[J].Trans Atmos Sci,39(4):525-535.(in Chinese).
吴迪,王澄海,何光碧,2016.青藏高原地区夏季两次强降水过程中重力波特征分析[J].高原气象,35(4):854-864.Wu D,Wang C H,He G B,2016.Gravity w ave characteristics in tw o summer heavy rainfall in the Qinghai-Xizang Plateau[J].Plateau M eteor,35(4):854-864.(in Chinese).
谢娜,王咏青,施娟,等,2011.城区下垫面特征对成都一次暴雨过程影响的数值模拟[J].高原气象,30(6):1472-1480.Xie N,Wang Y Q,Shi J,et al.,2011.Numerical simulation of city underlying surface effect on a rainstorm process in Chengdu[J].Plateau M eteor,30(6):1472-1480.(in Chinese).
徐珺,毕宝贵,谌芸,等,2018.“5.7”广州局地突发特大暴雨中尺度特征及成因分析[J].气象学报,76(4):511-524.Xu J,Bi B G,Chen Y,et al.,2018.M esoscale characteristics and mechanism analysis of the unexpected local torrential rain in Guangzhou on 7 M ay 2017[J].Acta M eteor Sinica,76(4):511-524.(in Chinese).
杨波,孙继松,毛旭,等,2016.北京地区短时强降水过程的多尺度环流特征[J].气象学报,74(6):919-934.Yang B,Sun J S,Mao X,et al.,2016.M ulti-scale characteristics of atmospheric circulation related to short-time strong rainfall events in Beijing[J].Acta M eteor Sinica,74(6):919-934.(in Chinese).
杨军,张磊,李宝东,等,2017.太行山东麓一次强对流降雹过程中的地形强迫[J].大气科学学报,40(2):253-262.Yang J,Zhang L,Li B D,et al.,2017.The orograrhic impact of a severe convection over the Taihang M ontains[J].Trans Atmos Sci,40(2):253-262.(in Chinese).
Yang P,Ren G Y,Yan P C,2017.Evidence for a strong association of short-duration intense rainfall w ith urbanization in the Beijing urban area[J].JClimate,30(15):5851-5870.
叶丽梅,江志红,霍飞,2014.南京地区下垫面变化对城市热岛影响的数值模拟[J].大气科学学报,37(5):642-652.Ye L M,Jiang Z H,Huo F,2014.Numerical simulation of the impact of land cover change on the urban heat island effect in Nanjing[J].Trans Atmos Sci,40(2):253-262.(in Chinese).
章翠红,夏茹娣,王咏青,2018.地形、冷池出流和暖湿空气相互作用造成北京一次局地强降水的观测分析[J].大气科学学报,41(2):207-219.Zhang C H,Xia R D,Wang Y Q,2018.Observational analysis of a local heavy rainfall in Beijing caused by terrain,cold pool outflow and w arm moist air interactions[J].Trans Atmos Sci,41(2):207-219.(in Chinese).
Zhang C L,Chen F,M iao S G,et al.,2009.Impacts of urban expansion and future green planting on summer precipitation in the Beijing metropolitan area[J].J Geophys Res,114,D02116.
Zhong S,Yang X Q,2015.M echanism of urbanization impact on a summer cold-frontal rainfall process in the greater Beijing metropolitan area[J].JAppl M eteor Climatol,54(6):1234-1247.
张赟程,王晓峰,张蕾,等,2017.海风与热岛耦合对上海强对流天气影响的数值模拟[J].高原气象,36(3):705-717.Zhang Y C,Wang X F,Zhang L,et al.,2017.Numerical simulation of the impacts of the sea-breeze and the urban heat island on the severe convective event in Shanghai[J].Plateau Meteor,36(3):705-717.(in Chinese).
周晶,刘蕾,霍飞,等,2018.不同下垫面数据和城市冠层参数化方案对江苏气温影响的个例分析[J].气象科学,38(3):342-350.Zhou J,Liu L,Huo F,et al.,2018.Impact of different underlying surface data and urban canopy schemes on simulation of the temperature in Jiangsu:a WRFcase study[J].J M eteor Sci,38(3):342-350.(in Chinese).
Zhou S W,M a Y,Ge X Y,2016.Impacts of the diurnal cycle of solar radiation on spiral rainbands[J].Adv Atmos Sci,33(9):1085-1095.
丁一汇,1994.暴雨和中尺度气象学问题[J].气象学报,52(3):274-284.Ding Y H,1994.Some aspects of rainstorm and mesoscale meteorology[J].Acta Meteor Sinica,52(3):274-284.(in Chinese).
高守亭,周玉淑,冉令坤,2018.我国暴雨形成机理及预报方法研究进展[J].大气科学,42(4):833-846.Gao S T,Zhou Y S,Ran L K,2018.A review on the formation mechanisms and forecast methods for torrential rain in China[J].Chin J Atmos Sci,42(4):833-846.(in Chinese).
Guo X,Fu D,Wang J,2006.M esoscale convective precipitation system modified by urbanization in Beijing city[J].Atmos Res,82:112-126.
Hendricks E A,Peng M S,Ge X,et al.,2011.Performance of a dynamic initialization scheme in the coupled ocean-atmosphere mesoscale prediction system for tropical cyclones(COAM PS-TC)[J].Wea Forecasting,26(5):650-663.
Hong S Y,Noh Y,Dudhia J,2006.A new vertical diffusion package w ith an explicit treatment of entrainment processes[J].M on Wea Rev,134(9):2318-2341.
Hoskins B J,Draghici I,Davies H C,1978.A new look at theω-equation[J].Quart J Roy M eteor Soc,104(439):31-38.
Justice C O,Tow nshend J R G,Vermote E F,et al.,2002.An overview of M ODIS land data processing and product status[J].Remote Sens Environ,83(1/2):3-15.
Kain J S,Fritsch J M,1990.A one-dimensional entraining/detraining plume model and its application in convective parameterization[J].J Atmos Sci,47:2784-2802.
Kiladis G N,1998.Observations of Rossby w aves linked to convection over the eastern tropical Pacific[J].J Atmos Sci,55:321-339.
Kiladis G N,Weickmann K M,1992.Circulation anomalies associated w ith tropical convection during northern w inter[J].M on Wea Rev,120:1900-1923.
孔锋,王一飞,方建,等,2018.中国夏季极端降水空间格局及其对城市化的响应(1961-2010)[J].长江流域资源与环境,27(5):61-75.Kong F,Wang Y F,Fang J et al.,2018.Spatial pattern of summer extreme precipitation and its response to urbanization in China(1961-2010)[J].Res Environ Yang.Basin,27(5):61-75.(in Chinese).
Lin Y L,Farley R D,Orville H D,1983.Bulk parameterization of the snow field in a cloud model[J].J Climate Appl M eteor,22(6):1065-1092.
M iao S G,Chen F,Li Q C,et al.,2011.Impacts of urban processes and urbanization on summer precipitation:a case study of heavy rainfall in Beijing on 1 August 2006[J].J Appl M eteor Climatol,50(4):806-825.
Nastrom G D,Fritts D C,1992.Sources of mesoscale variability of Gravity Waves.Part I:topographic excitation[J].J Atmos Sci,49:101-110.
Skamarock W C,Klemp J B,Dudhia J,et al.,2008.A description of the advanced research WRF version 3.NCAR Tech[R].Note NCAR/TN-4751STR.
沈伟,袁慧玲,陈曦,等,2017.江苏暖季短时强降水的时空不均匀特征分析[J].大气科学学报,40(4):453-462.Shen W,Yuan H L,Chen X,et al.,2017.Temporal and spatial heterogeneity of w arm-season short-time heavy rainfall in Jiangsu Province[J].Trans Atmos Sci,40(4):453-462.(in Chinese).
陶诗言,丁一汇,周晓平,1979.暴雨和强对流天气的研究[J].大气科学,3(3):227-238.Tao S Y,Ding Y H,Zhou X P,1979.The present status of the research on rainstorm and severe convective w eather in China[J].Chin J Atmos Sci,3(3):227-238.(in Chinese).
Wang J,Feng J M,Yan Z W,2015.Potential sensitivity of w arm season precipitation to urbanization extents:modeling study in Beijing-Tianjin-Hebei urban agglomeration in China[J].J Geophys Res Atmos,120(18):9408-9425.
王咏薇,任侠,翟雪飞,等,2016.南京复杂下垫面条件下的三维城市热环境模拟[J].大气科学学报,39(4):525-535.Wang Y W,Ren X,Zhai XF,et al.,2016.Numerical study of the three-dimensional thermal environment over a complex underlying surface in Nanjing[J].Trans Atmos Sci,39(4):525-535.(in Chinese).
吴迪,王澄海,何光碧,2016.青藏高原地区夏季两次强降水过程中重力波特征分析[J].高原气象,35(4):854-864.Wu D,Wang C H,He G B,2016.Gravity w ave characteristics in tw o summer heavy rainfall in the Qinghai-Xizang Plateau[J].Plateau M eteor,35(4):854-864.(in Chinese).
谢娜,王咏青,施娟,等,2011.城区下垫面特征对成都一次暴雨过程影响的数值模拟[J].高原气象,30(6):1472-1480.Xie N,Wang Y Q,Shi J,et al.,2011.Numerical simulation of city underlying surface effect on a rainstorm process in Chengdu[J].Plateau M eteor,30(6):1472-1480.(in Chinese).
徐珺,毕宝贵,谌芸,等,2018.“5.7”广州局地突发特大暴雨中尺度特征及成因分析[J].气象学报,76(4):511-524.Xu J,Bi B G,Chen Y,et al.,2018.M esoscale characteristics and mechanism analysis of the unexpected local torrential rain in Guangzhou on 7 M ay 2017[J].Acta M eteor Sinica,76(4):511-524.(in Chinese).
杨波,孙继松,毛旭,等,2016.北京地区短时强降水过程的多尺度环流特征[J].气象学报,74(6):919-934.Yang B,Sun J S,Mao X,et al.,2016.M ulti-scale characteristics of atmospheric circulation related to short-time strong rainfall events in Beijing[J].Acta M eteor Sinica,74(6):919-934.(in Chinese).
杨军,张磊,李宝东,等,2017.太行山东麓一次强对流降雹过程中的地形强迫[J].大气科学学报,40(2):253-262.Yang J,Zhang L,Li B D,et al.,2017.The orograrhic impact of a severe convection over the Taihang M ontains[J].Trans Atmos Sci,40(2):253-262.(in Chinese).
Yang P,Ren G Y,Yan P C,2017.Evidence for a strong association of short-duration intense rainfall w ith urbanization in the Beijing urban area[J].JClimate,30(15):5851-5870.
叶丽梅,江志红,霍飞,2014.南京地区下垫面变化对城市热岛影响的数值模拟[J].大气科学学报,37(5):642-652.Ye L M,Jiang Z H,Huo F,2014.Numerical simulation of the impact of land cover change on the urban heat island effect in Nanjing[J].Trans Atmos Sci,40(2):253-262.(in Chinese).
章翠红,夏茹娣,王咏青,2018.地形、冷池出流和暖湿空气相互作用造成北京一次局地强降水的观测分析[J].大气科学学报,41(2):207-219.Zhang C H,Xia R D,Wang Y Q,2018.Observational analysis of a local heavy rainfall in Beijing caused by terrain,cold pool outflow and w arm moist air interactions[J].Trans Atmos Sci,41(2):207-219.(in Chinese).
Zhang C L,Chen F,M iao S G,et al.,2009.Impacts of urban expansion and future green planting on summer precipitation in the Beijing metropolitan area[J].J Geophys Res,114,D02116.
Zhong S,Yang X Q,2015.M echanism of urbanization impact on a summer cold-frontal rainfall process in the greater Beijing metropolitan area[J].JAppl M eteor Climatol,54(6):1234-1247.
张赟程,王晓峰,张蕾,等,2017.海风与热岛耦合对上海强对流天气影响的数值模拟[J].高原气象,36(3):705-717.Zhang Y C,Wang X F,Zhang L,et al.,2017.Numerical simulation of the impacts of the sea-breeze and the urban heat island on the severe convective event in Shanghai[J].Plateau Meteor,36(3):705-717.(in Chinese).
周晶,刘蕾,霍飞,等,2018.不同下垫面数据和城市冠层参数化方案对江苏气温影响的个例分析[J].气象科学,38(3):342-350.Zhou J,Liu L,Huo F,et al.,2018.Impact of different underlying surface data and urban canopy schemes on simulation of the temperature in Jiangsu:a WRFcase study[J].J M eteor Sci,38(3):342-350.(in Chinese).
Zhou S W,M a Y,Ge X Y,2016.Impacts of the diurnal cycle of solar radiation on spiral rainbands[J].Adv Atmos Sci,33(9):1085-1095.