Hsu, C.¹, M.J. Prather¹, O. Wild², J.K. Sundet³, I.S.A. Isaksen³, E.V. Browell⁴, M.A. Avery⁴, and G.W. Sachse⁴

1. Earth System Science, University of California, Irvine, California, USA.
2. Frontier Research System for Global Change, Yokohama, Japan.
3. Department of Geophysics, University of Oslo, Oslo, Norway.
4. NASA Langley Research Center, Virginia, USA.

Observations of CO and O₃ from the TRACE-P campaign are compared with modeled distributions from the FRSGC/UCI CTM driven by the Oslo T63L40 ECMWF forecast meteorology. The model-measurement comparison is made within the context of how well the TRACE-P observations represent the springtime chemistry and ozone distributions over eastern Asia and the western Pacific in March 2001, and uses the 4-D extended domain from the model to provide unbiased statistics. A key question is whether the limited sampling density or mission strategy led to a statistically biased sample. To address this question, we examine a diverse range of statistical analyses of the observations of CO and O₃. The middle percentiles of the cumulative probability functions for CO in the free troposphere are representative (and reproduced by the CTM), but those in the boundary layer are not. The frequency of low-CO, stratospheric influence, is well matched along flight tracks, but is atypical of the extended domain. The percentiles of the latitude-by-height distribution of lidar O₃ show how the CTM reproduces the non-representative clumpy nature of the observations, but has too low a tropopause about the jet region (30-35N). Adaptive kernel estimation of the 2-D probability density of O₃-CO correlations shows a very good simulation of two different chemical regimes (stratospheric and polluted) that is quite different from the extended domain, but also highlights the failure to predict CO>400 ppb. Empirical orthogonal function analysis of the O₃ vertical profiles shows how six EOFs can effectively describe the 4-D structures of O₃ over this entire domain. The latitude-by-longitude maps of the principal components provide an excellent test of the CTM simulation along flight tracks and clearly show the unique sampling of O₃ events by the TRACE-P flights. In many cases the ability of the model to simulate the non-representative observations implies a clear skill in matching the unique meteorological and chemical features of the region.

J. Geophys. Res., 109, in press, doi:10.1029/2003JD004002.

(Submitted: 23 July 2003; Revised: 29 October 2003; Accepted: 14 November 2003)