Appearance of a Spring Maximum in Nuclear Test Debris in 1960

Arch. Met. Geoph. Biokl. A.

1969

SummaryThe downward transport of radioactive debris from the stratosphere in association with tropopause-level cyclogenesis offers a possible physical explanation for seasonal and shorter-period surface fallout increases. To examine these possibilities, a simple circulation index which is related to the degree of cyclonic activity in the upper troposphere is compared to a time series of area-averaged fallout intensity. The comparison reveals that the spring fallout peak cannot be explained adequately by an increase in cyclonic activity at this time of year. Shorter period increases, however, are strongly related to occurrences of intense cyclogenesis in the upper troposphere.The age-corrected fallout averaged over the area of the contiguous United States reveals the existence of a regular seasonal variation with a maximum in late spring and a minimum in late fall. The spring peak in 1964 is a factor of two less in 1964 than 1963 --reflecting the progressive depletion of debris following the nuclear testing moratorium of December, 1962. Zusammenfassung Die Abh~ingigkeit langperiodischer Schwankungen des radioaktiven Ausfalls an der Erdoberfl~iche von zyklogenetischen Vorg~ingen im TropopausenniveauDer nach unten gerichtete Transport radioaktiver Spurenstoffe aus der Stratosph/ire im Zusammenhang mit Zyklogenese im Tropopausenniveau bietet eine physikalische Erklfirung ffir die jahreszeitlichen und kurzperiodischen Zunahmen des radioaktiven Ausfalls an der Erdoberfl/iche. Um diese Vorg/inge zu iiberpriifen, wurde ein einfacher Zirkulationsindex, dermit der Zyklonent/itigkeit in der oberen Troposphfire zusammenh/ingt, mit den zeitlichen ~nderungen der fl/ichenhaft gemittelten Maxima yon radioaktivem Ausfall verglichen. Dieser Ver-

Section: Methodssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Die Abhängigkeit langperiodischer Schwankungen des radioaktiven Ausfalls an der Erdoberfläche von zyklogenetischen Vorgängen im Tropopausenniveau

Arch. Met. Geoph. Biokl. A.

1969

“…FRY, JEw and Ku~oDA [8] studied the 1959 peak by chemical dating methods and concluded that it contained debris which was older than could be explained by the Russian tests. Measurements taken at Argonne National Laboratory revealed an increase of cesium-137 from April to June 1960, although no nuclear tests were made in the previous year (GusTAF-SON et al [10]). Analyses of artificially produced tritium showed spring maxima for the years 1958, 1959 and 1960 that are remarkably in phase with the strontium-90 measurements for those years (LIBBY [14]).…”

Section: Literature Pertaining To the Problemmentioning

confidence: 96%

Relation of stratospheric-tropospheric mass exchange mechanisms to surface radioactivity peaks

Arch. Met. Geoph. Biokl. A.

1965

Abstract. The atmospheric origin of the debris which produced a sudden increase of surface radioactivity is studied. Because all the radioactivity measurements show the mean debris ages to be greater than one hundred days for the entire sequence, the air is inferred to have been of recent stratospheric origin in view of an assumed mean tropospheric debris residence time of one month.The trajectories of the layer which caused the sudden increase in debris concentration were traced isentropically backward from the point of the fallout increase. The computed trajectory is seen to originate in the region traditiona]ly considered to be the "jet stream front" and is shown definitely to be stratospheric air through potential vorticity considerations. The sinking motion is associated with upper air cyclogenesis and takes place to the rear of this high level cyclone. The air appears to cross the jet axis as viewed on an isobaric surface; but viewed isentropically, the trajectory is seen to "slip under" the jet core in such manner that no appreciable lateral shears are observed.Zusammenfassung. Es wird der atmosph~rische Ursprung der Ausfallprodukte, die einen pl6tzlichen Anstieg der Radioaktivit~it in Bodenn~he verursachten, untersucht. Da alle Radioaktivit/itsmessungen zeigten, dab das mittlere Alter der Ausfallprodukte in der MeBreihe gr6Ber als 100 Tage war, wird geschlossen, daB, im ttinbliek auf eine angenommene mittlere Aufenthaltszeit der Ausfallprodukte in der Troposphere yon einem Mortar, die Luft nicht lange vorher aus der Stratosphere zugestrSmt sein kann.Die R6sumg. On recherche l'origine atmosph6rique des r6sidus provoquant un aceroissement brusque de la radioaetivitd au voisinage du sol. Comme routes les mesures de la radioactivit6 ont montr6 que l'gge moyen des produits r~-siduels des diff@rentes sdries de mesure ddpassait toujours 100 jours, on en conclut que, en admettant que ces particules se maintiennent en moyenne t mois dans la trophosph~re, l'air ne parvient pas longtemps auparavant de la stratosph@re.On a recherehd ]a trajeetoire inverse des masses d'air provoquant un accroissement subit de la retomh~e radioactive. Pour ce faire, on est parti du point off la dire recrudescence avait 6t6 constat@e et, par des mdthodes isentropiques, on a reconstitu6 la trajeetoire pr6sumde des produits r~siduels. Les trajectoires ainsi calcul@es prennent naissance dans la rdgion ddnomm6e ordinairement ,,Jet Stream Front,,. L'examen de la ,,vorticity,, potentielle ~ montr~ que l'air a une origine stratosph6rique inddniable. Le mouvement subsident est lid ~ une cyclogdnbse ~ tr@s haute altitude et se produit l'arri6re de la dite ddpression. En eonsid6rant une surface isobarique, il semble que Fair traverse l'axe du courant. En considdrant les choses de mani6re isentropique, on constate cependant que la traj eetoire passe sous le noyau du courant de telle sorte qu'il n'y air pas de cisaillement la.tdriat appr@ciable.

“…276 16 b1AY 1997 assum~tion that the observed seasonal vari-tratro~ical cjlclone growth well enough to eauatorward and downward movement of ation of surface radioactive fallout (resulting from detonations of nuclear weapons that initially deposit their radioactive debris into the stratosphere) is related to the seasonal variation in the intensity of extratropical cyclones (13). Later it was found that the cyclogenesis process is active throughout the year in its movement of lower stratospheric air into the troposphere, thus leading to the assertion that the tropospheric seasonal radioactivity cycle and its spring peak depend mainly on the seasonal variations in the extratronical downward mass flux to the vicinity of the tropopause (14).…”

Section: Transport Across the Tropopausementioning

confidence: 99%

Dynamics of Transport Processes in the Upper Troposphere

1997

Science

A number of key problems in atmospheric chemistry are shaped by the strength and character of the various mechanisms acting to move and mix air in the upper troposphere. These transport processes are examined from a mechanistic perspective, with primaryemphasis on the tropopause and middle-troposphere regions in the extratropics. The roles of vertical and horizontal transport "barriers" are explored, including the processes by which such barriers are created and are overcome. These transport considerations lead to a hypothesis concerning the processes that shape the tropopause itself. Some perspectives are offered on the still immature subject of transport in the upper troposphere of the tropics.