Abstract
Unexpected high levels of OH and NO were recorded at the South Pole (SP) Atmospheric Research Observatory during the 1998–99 ISCAT field study. Model simulations suggest a major photochemical linkage between observed OH and NO. A detailed comparison of the observations with model predictions revealed good agreement for OH at NO levels between 120 and 380 pptv. However, the model tended to overestimate OH for NO levels <120 pptv, while it underestimated OH at levels >380 pptv. The reasons for these deviations appear not to involve NO directly but rather HOx radical scavenging for the low NO conditions and additional HOx sources for the high NO conditions. Because of the elevated levels of NO and highly activated HOx photochemistry, the SP was found to be a strong net source of surface ozone. It is quite likely that the strong oxidizing environment found at the South Pole extends over the entire polar plateau.
Highlights
OH and NO were constrained to their observed median values
The HNO3 valuesthemselvesranged from 120to 750 pptv
NO sensorhada 2cdetectionlimit (LOD) of 6 pptv.The OH datawas alsotaken at 1min. intervalsfor Dec. 12- 30, '98
Summary
TheSPwasfoundtobe a strongnetsourceof surfaceozone.It is as discussedby Davis et al [this issue],the 1998 quitelikely thatthe strongoxidizingenvironmenftoundat the ISCAT observationasppearto dramaticallyalterthisperception. Thesepredictionswererealizedfromdirectobservationosf both Thephotochemistroyf nearsurfaceairattheSouthPole(SP) species[Mauldinet al., this issue;andArimoto,unpublished hasreceivedminimalattentionfromthemodelingcommunityin results]. Reflectsthe factthatotherthan03 model results with the observationsusing the new' NO andCO, little dataexistedtojustify detailedmodelstudiesT. He observations,along with other in-situ data, as input to the recentfield studyISCAT (Investigationof SulfurChemistryin model.The SPbudgetsfor OH andHOxandthesignificanceof the AntarcticTropospherep) rovidesextensivephotochemical HOx/NOxchemistryto 03 formationhavealsobeenexplored. Database and Model Description earlier SCATE program(Sulfur Chemistryin the Antarctic 2.1.
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