Observations of PAN and its confinement in the Asian summer monsoon anticyclone in high spatial resolution

Title (Dublin Core)

Observations of PAN and its confinement in the Asian summer monsoon
anticyclone in high spatial resolution

Description (Dublin Core)

This paper presents an analysis of trace gases in the Asian summer monsoon (ASM) region on the basis of observations by the CRISTA infrared limb sounder taken in low-earth orbit in August 1997. The spatially highly resolved measurements of peroxyacetyl nitrate (PAN) and O<sub>3</sub> allow a detailed analysis of an eddy-shedding event of the ASM anticyclone. We identify enhanced PAN volume mixing ratios (VMRs) within the main anticyclone and within the eddy, which are suitable as a tracer for polluted air originating in India and China. Plotting the retrieved PAN VMRs against potential vorticity (PV) and potential temperature reveals that the PV value at which the PAN VMRs exhibit the strongest decrease with respect to PV increases with potential temperature. These PV values might be used to identify the extent of the ASM. Using temperature values also derived from CRISTA measurements, we also computed the location of the thermal tropopause according to the WMO criterion and find that it confines the PAN anomaly vertically within the main ASM anticyclone. In contrast, the shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. Using the relationship between PAN as a tropospheric tracer and O<sub>3</sub> as a stratospheric tracer to identify mixed air parcels, we further found the anticyclone to contain few such air parcels, whereas the region between the anticyclone and the eddy as well as the eddy itself contains many mixed air parcels. In combination, this implies that while the anticyclone confines polluted air masses well, eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere with a timescale of only a few days.

Creator (Dublin Core)

Ungermann, Jörn

Ern, Mandfred

Kaufmann, Martin

Müller, Rolf

Spang, Reinhold

Ploeger, Felix

Vogel, Bärbel

Riese, Martin

Date (Dublin Core)

2018-09-10

Type (Dublin Core)

info:eu-repo/semantics/Text

Format (Dublin Core)

info:eu-repo/semantics/application/pdf

Identifier (Dublin Core)

10.5194/acp-16-8389-2016

https://acp.copernicus.org/articles/16/8389/2016/

Source (Dublin Core)

eISSN: 1680-7324

Language (Dublin Core)

eng

Relation (Dublin Core)

info:eu-repo/grantAgreement/EC/FP7/603557

Rights (Dublin Core)

info:eu-repo/semantics/openAccess

Item