简介：Therearethreebasicmethodsinradiativetransfercalculations,i.e.,line-by-line(LBL)integration,correlatedk-distributionmethod,andbandmodel.TheLBLintegrationisthemostaccurateofall,inwhich,therearetwoquadraturealgorithmsnamedinthispaperasintegrationbylinesandbysamplingpointswhencalculatingatmospherictransmittanceintheconsideredwavenumberregion.BecausetheLBLintegrationisthemostexpensiveofall,itisnecessaryandimportanttosavecalculationtimebutincreasecalculationspeedwhenitisputintouseinthedailyoperationinatmosphericremotesensingandatmosphericsounding.AsimplifiedLBLmethodisgiveninthispaperonthebasisofintegrationbylines,whichincreasescomputationalspeedgreatlywithkeepingthesameaccuracy.Then,wediscusstheeffectsofdifferentcutoffschemesonatmosphericabsorptioncoefficient,transmittance,andcoolingrateunderbothofaccurateandsimplifiedLBLmethodsindetail.Therearefourcutoffschemesdescribedinthispaper,i.e.,CUTOFFs1,2,3,and4.Itisshownbythisnumericalstudythatthewaytocutoffspectralline-winghasagreateffectontheaccuracyandspeedofradiativecalculations.TherelativeerrorsofthecalculatedabsorptioncoefficientsforCUTOFF2arethelargestunderdifferentpressures,whileforCUTOFF1,theyarelessthan2%atmostofsamplingpointsandforCUTOFFs3or4,theyarealmostlessthan5%inthecalculatedspectralregion,however,thecalculationtimeisreducedgreatly.WefindinthisstudythatthetransmittanceintheloweratmosphereisnotsensitivetodifferentLBLmethodsanddifferentcutoffschemes.Whereasforthehigheratmosphere,thedifferencesoftransmittanceresultsbetweenCUTOFF2andeachofotherthreecutoffschemesarethebiggestofallnomatterfortheaccurateLBLorforthesimplifiedLBLintegrations.Bycomparison,thebestandoptimizedcutoffschemeisgiveninthispaperfinally.