Evaluation of meteorological analyses, simulations, and long-range transport calculations using ANATEX surface tracer data

Abstract

Perfluorocarbon tracer data collected during the Across North America Tracer Experiment (ANATEX) are used. Three basic types of meteorological analysis and simulation are evaluated: objective analysis of observed data, prognostic simulation with observed lateral boundary conditions, and four-dimensional data assimilation (FDDA). The root-mean square data indicate that the optimum value of the Newtonian nudging coefficient for the FDDA wind field in the lower troposphere is 6 × 10-4 s-1. These data also show that trajectory errors, with respect to transport distance, are larger in low-speed wind regimes than in medium- to high-speed regimes, and suggest that the rate of increase of trajectory error decreases with time, but the uncertainty of the rate of increase is quite large during the first 18 h of transit. The overall result suggest that when both the vertical and horizontal components of the wind fields are considered, FDDA (using an appropriate value for the nudging coefficient) is better than the other methodologies. -from Authors