UsingaDMT(DropletMeasurementTechnologies)continuousflowstreamwisethermalgradientcloudcondensationnuclei(CCN)countermountedonaCheyenneⅢAaircraft,about20flightsforaircraftmea-surementsofCCNoverNorthChinawereconductedintheautumnof2005andspringof2006.Accordingtothedesignforaircraftobservation,themethodofspiralascentordescentinthetropospherewasusedfortheverticalmeasurementofCCN,andsomecertainlevelswerechosenforhorizontalmeasurement.TheverticaldistributionsofCCNconcentrationsshowthatmostCCNparticlesareconcentratedinthelowleveloftroposphereandCCNconcentrationdecreasedwithheightincreasing.ItsuggeststhatthemainsourceofCCNisfromthesurface.Thisresultisconsistentwithformerstudiesduring1983-1985inChinawithastaticthermalgradientCCNcounter.ThecomparisonofverticalobservationsbetweenpollutedruralareanearShijiazhuangandnon-pollutedruralareanearZhangjiakoushowsthatthereisaboutfivetimesdifferenceinCCNconcentration.Butovertwopollutedcities,ShijiazhuangandHandan,thereisnonotabledifferenceinCCNconcentration.ThehorizontalflightmeasurementsforpenetratingthecumuluscloudsexperimentshowtheapparentdecreaseofCCNinclouds.ItconfirmsthatcloudhasadefiniteconsumptiveeffectonCCNparticlesbecausesomeCCNparticlescanformclouddroplets.ThesurfacemeasurementsofCCNinShijiazhuangCityweremadeduringJune-August2005.Thesta-tisticalCCNdatashowthegreatdifferenceinconcentrationatthesamesupersaturation(S)inShijiazhuangsummertime.TheminimumCCNconcentrationswere584,808,and2431cm~(-3),andthemaximumconcen-trationswere9495,16332,and21812cm~(-3)atS=0.1%,0.3%,and0.5%,respectively.CCNhasadiurnalvariationcycle.From0600BT,theconcentrationbegantoincreaseandreachedthemaximumataboutnoon.Thenitgenerallydecreasedthroughouttheafternoon.Thereasonmaybeisrelatedtotheonsetofemissionsfromvehiculartraffi
