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Processes Controlling Water Vapor in the Winter Arctic Stratospheric MiddleworldAbstract: Water vapor in the winter arctic stratospheric middleworld (that part of the stratosphere with potential temperatures lower than the tropical tropopause) is important for two reasons: (1) the arctic middleworld is a source of air for the upper troposphere because of the generally downward motion, and thus its water vapor content helps determine upper tropospheric water, a critical part of the earth's radiation budget; and (2) under appropriate conditions, relative humidities will be large even to the point of stratospheric cirrus cloud formation, leading to the production of active chlorine species that could destroy ozone. On a number of occasions during SOLVE, clouds were observed in the stratospheric middleworld by the DC-8 aircraft. The relationship between ozone and CO from aircraft measurements taken during the early, middle and late part of the winter of 1999-2000 show that recent mixing with tropospheric air extends up to ozone values of about 350-450 ppbv. Above that level, the relationship suggests stratospheric air with minimal tropospheric influence. The transition is quite abrupt, particularly in early spring. Trajectory analyses are consistent with these relationships, with a significant drop-off in the percentage of trajectories with tropospheric PV values in their 10-day history as in-situ ozone increases above 400 ppbv. The water distribution is affected by these mixing characteristics, and by cloud formation. Significant cloud formation along trajectories occurs up to ozone values of about 400 ppbv during the early spring, with small, but nonzero probabilities extending to 550 ppbv. Cloud formation in the stratospheric middleworld is minimal during early and midwinter. Also important is the fact that, during early spring 30% of the trajectories near the tropopause (ozone values less than 200 ppbv) have minimum saturation mixing ratios less than 5 ppmv. Such parcels can mix out into the troposphere and could lead to very dry conditions in the upper troposphere at high latitudes during spring,
Document ID
20010007248
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Pfister, Leonhard
(NASA Ames Research Center Moffett Field, CA United States)
Selkirk, Henry B.
(NASA Ames Research Center Moffett Field, CA United States)
Jensen, Eric J.
(NASA Ames Research Center Moffett Field, CA United States)
Podolske, James
(NASA Ames Research Center Moffett Field, CA United States)
Sachse, Glen
(NASA Ames Research Center Moffett Field, CA United States)
Avery, Melody
(NASA Ames Research Center Moffett Field, CA United States)
Schoeberl, Mark R.
(NASA Ames Research Center Moffett Field, CA United States)
Hipskind, R. Stephen
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Subject Category
Geophysics
Funding Number(s)
PROJECT: RTOP 622-65-07-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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