Sources of seasonal variability in tropical upper troposphere and lower stratosphere water vapor and ozone: Inferences from the Ticosonde data set at Costa Rica. Issue 18 (17th September 2015)

• Record Type: Journal Article
• Authors: Schoeberl, Mark R.; Selkirk, Henry B.; Vömel, Holger; Douglass, Anne R.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 18(2015:Oct.)
• Page Start: 9684
• Page End: 9701
• Publication Date: 2015-09-17
• Subjects: tropical tropopause -- water vapor -- ozone; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2015JD023299
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: We present an analysis of joint balloonsonde profiles of water vapor and ozone made at Costa Rica from 2005 to 2011 using compositing techniques, tracer‐tracer diagrams, and back trajectory methods. Our analysis reveals important seasonal differences in structure in the upper troposphere and lower stratosphere. Water vapor amounts in boreal winter at Costa Rica are much lower than expected from local ice saturation temperatures. The boreal summer data show both higher average water vapor amounts and a much higher level of variability than the winter data. To understand this seasonal contrast, we consider three sources of tracer variability: wave‐induced vertical motion across strong vertical gradients ("wave variability"), differences in source air masses resulting from horizontal transport ("source variability"), and changes induced along parcel paths due to physical processes ("path variability"). The winter and summer seasons show different mixes of these three sources of variability with more air originating in the tropical western Pacific during winter. Key Points: Sonde‐measured Costa Rican O3 and H2 O vapor show distinct seasonal variations Water vapor is too low for the air to be locally dehydrated Three processes lead to tracer variability: waves, path changes, and sources