Tracer and Chemical Climatologies

Initial studies focus on source regions and types using inert-NOx (i-NOx) tracers released at the same rate as NOx but given an e-fold decay time of 10 days. The lifetime is more appropriate for CO, but this allows the signature of NOx emissions to be followed rather further downwind than would otherwise be possible.

The following examples of long-range transport make use of the ECMWF IFS fields for 1996 (T21 resolution). Regional-diurnal-mean concentrations of each iNOx tracer are presented in three latitude bins (up to 150 hPa) over regions representative of Guam, Hong Kong and Japan; grey values show total iNOx, coloured values show the time-series of contributions from the particular source presented.

Total iNOx Tracer - summary for the East Asian Boundary layer
African Biomass Burning Tracer - episode at 300 hPa, Day 84
Indian Tracer (all sources) - episode at 500 hPa, Day 103
European Fossil Fuel Tracer - episode at 500 hPa, Day 51
Chinese Tracer (all sources) - episode at 800 hPa, Day 44

Further examples showing the interaction of air lifted by processes other than convection and subsidence of air from the upper troposphere and stratosphere.

Episodes of non-convected iNOx and stratospheric O3 over Japan
Vertical cross sections of a lifting period (unrotated plot)
Horizontal cross sections of a lifting period (unrotated plot)

The following example taken from GISS II' GCM fields for April (noon JST) shows surface streamlines and humdity anomaly (red positive, blue negative) associated with frontal passage. The tongue of warm, humid, rising air lies between two areas of descending air, and is directly over the main emission regions of eastern and northeastern China.
April 6, 12:00 JST

The diurnal-mean anomaly in East Asian fossil fuel i-NOx at 800 hPa is shown below; lifting in the warm sector is seen clearly in elevated concentrations over northeast China and reduced concentrations in subsiding air on either side.

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Oliver Wild

Last modified: Thu Feb 19 18:47:00 JST 2001