AerialphototakenonJuly26,2021showstherescuesceneoutsidetheFirstAffiliatedHospitalofXinxiangMedicalUniversityinWeihui,XinxiangCityofcentralChina'sHenanProvince.(Xinhua/HaoYuan)FromJuly17to22,torrentialrainstormshitcentralChina’sHenanProvince.Initscapitalcity,Zhengzhou,theequivalentofhalfitsannualrainfallpoureddownin24hoursbetweenJuly20and21.Followingarecord-breakingmaximumrainfallof201.9millimetersinanhour,1/6ofweatherstationsintheprovincerenewedtheirdailyrainfallrecords.ByAugust2,thedevastatingfloodingittriggeredhadclaimed302livesandaffectedmorethan14.53millionpeoplein150county-levelregions.Accordingtoofficialdata,over1.09millionhectaresofcropsweredamaged,andover30,600houseshavecollapsedacrosstheprovince.Therainfallisdeemedarareweathereventinclimatehistoryintermsofbothintensityandinfluence.Areviewoftheprecipitationprocessandthecharacteristicsoftherainfallismadeforaclearunderstandingofthesituation.HighextremityFigure1(Source:NationalMeteorologicalCenterofCMA)Duringtheprocessoftheheavyrainfall,20nationalweatherstationsrenewedtheirdailyrainfallrecords,whichaccountforonesixthofthetotalnumberofnationalweatherstationsinHenan.Figure1showsthosenationalweatherstationsandacomparisonofthenewrecordwiththeoldrecord.Inthemeantime,32weatherstationsintheprovincerecordedmorethan500mmofprecipitationwithinaday,and5recordedmorethan600mm.Notably,therainfallrecordedbythestationofZhengzhoutotaled624.1mmwithin24hoursfrom8:00am,July20,to8:00am,July21,anamountalmostequaltoitsannualaveragetotal.Figure2(Source:NationalMeteorologicalCenterofCMA,WorldMeteorologicalOrganization)OnJuly14and15,extremerainfallaffectedGermanyandledtofloodingthatcausedmorethan50deaths.TheincidentwasdeemedtogobeyondthedescriptionoftheGermanlanguagebyGermanChancellorAngelaMerkel.AccordingtotheGermanMeteorologicalService(DWD),about100to150mmofprecipitationoccurredin24hours.Figure2showsthattheDWDweatherstationofWipperfuerth-Gardewegrecordedthehighestprecipitationof162mminasingleday,whichwasfollowedbyCologne-Stammheimwith160mm,Kall-Sistigwith152mmandWuppertal-Buchenhofenwith151mm.Figure2alsoliststhetopfournewdailyrainfallrecordsregisteredbythe20nationalweatherstationsmentionedabove.Tomakeahorizontalcomparison,theyareparalleledwiththerainintensityclassificationoftheChinaMeteorologicalAdministration(CMA)andthehighestdailyrainfallrecordsofthefourDWDweatherstations.AccordingtotherainintensityclassificationofCMA,rainfallrecordedbythefourDWDweatherstationsarewithintherangeofverytorrentialrain(whentheprecipitationrateisbetween100mmand249.9mmper24-hour).YetthefourrenewedrainfallrecordsinHenanallexceedthelevelofextremetorrentialrain(whentheprecipitationrateismorethan250mmper24-hour),andaremorethantwotimesheavierthantherainfallrecordedbytheDWDweatherstations.HighintensityinshorttermsFigure3(Source:NationalMeteorologicalCenterofCMA,WorldMeteorologicalOrganization)1-hourprecipitationisalsouniversallyusedtomeasurerainfallintensity.AccordingtoWikipedia,thefollowingcategoriesareapplied:•Lightrain-whentheprecipitationrateis2.5mmperhour•Moderaterain-whentheprecipitationrateisbetween2.5mm-7.6mmperhour•Heavyrain-whentheprecipitationrateis7.6mmperhour•Violentrain-whentheprecipitationrateis50mmperhourDuringtheraineventinHenan,10weatherstationsinZhengzhouCity,5inXinxiangCityand1inHebiCityrecordedamaximumone-hourrainfallofmorethan100mm.Amongthem,theweatherstationofZhengzhourankedfirstwithastaggering201.9mmofrainfallfrom16:00to17:00,July20,whichwasaboutthreetimeshigherthantheviolentrainintensity.ItalsobroketheChinesemainland’srecordoneofhourlyprecipitation-hourlyrainfallof198.5mmperhourinLinzhuang,HenanonAugust5,1975,asshowninFigure3.LargeaccumulationFigure4(Source:NationalMeteorologicalCenterofCMA)Figure4showsthatfromJuly17to22,rainfallincentralandnorthernHenantotaled200~400mm.InthecitiesofZhengzhou,Xuchang,Pingdingshan,Xinxiang,Jiaozuo,HebiandAnyang,accumulatedrainfallinsomeareas(30%~60%ofarea)reached500~700mm.IncitiesofXinxiang,ZhengzhouandHebi,accumulatedrainfallinpartsofareas(30%ofarea)reached800~965.5mm,800~993.1mmand800~1122.6mmrespectively.Themaximumaccumulatedrainfall,1122.6mm,occurredintheQibinDistrictinHebiCity.AccordingtodatafromCMA,theaveragedrainfallinHenanProvincereached222.9mm,andtheaveragedrainfallinZhengzhouCityreached532.3mm.Meanwhile,theaccumulatedrainfallat10nationalweatherstationsexceededtheannualaveragedrainfallinthearea.AsshowninFigure4,rainfallrecordedintheweatherstationofZhengzhzoutotaled820.5mmwithin5days,whichismorethan127%ofitsannualaverageof641mm.LongdurationTheheavyrainslastedsixconsecutivedaysfromJuly17to22.ThemostintensifiedrainfalloccurredbetweenJuly19to21.CentralandnorthernHenanwashitbyverytorrentialrainsfor4consecutivedays,whilethecitiesofZhengzhouandXinxiangsawextremetorrentialrainstwodaysinarow.VerticalcomparisonFigure5(Source:WorldMeteorologicalOrganization,NationalMeteorologicalCenterofCMA,Xinhua,Reuters,NASAEarthObservatory,TIME)Since1994,theWorldMeteorologicalOrganizationhasbeenpublishingtheWMOStatementontheStatusoftheGlobalClimateonanannualbasis,whichrecordsmajorweatherandclimateeventsaroundtheworld.AfewextremerainfalleventsoccurredinthiscenturyarelistedforreferenceandcomparisonwiththerainfallinHenan.Editor:DisclaimerTheviewsandopinionsexpressedinthisarticlearethoseoftheauthor's,GMW.cnmakesnorepresentationsastoaccuracy,suitability,orvalidityofanyinformationonthissiteandwillnotbeliableforanyerrors,omissions,ordelaysinthisinformation.