Trajectory model sensitivity to differences in input data and vertical transport method

摘要

In this study, trajectory model sensitivity to the input meteorological data and vertical transport method is quantified. ERA-40 and NCEP/NCAR reanalysis data sets are used to compare isentropic and kinematic 3-D tropospheric trajectories. Expanding on previous trajectory sensitivity studies, we accumulate deviation statistics for an entire year and for three geographically diverse sites. The horizontal trajectory deviations are summarized as a percentage of average distance traveled. These results allow ranking from least to greatest among the five causes of trajectory uncertainty investigated here: minor differences in computational methodology, 3–4%; time interpolation, 9–25%; vertical transport method, 18–34%; meteorological input data, 30–40%; and combined two-way differences in vertical transport method and meteorological input data, 39–47%. Although the deviations are somewhat dependent on starting location because of the influence of meteorology, at all three sites, 3-D trajectories attained higher elevations and wind speeds than isentropic trajectories. In addition, deviation statistics for 3-D trajectories exceeded those for isentropic trajectories. The reasons for this derive from uncertainties in the supplied vertical wind fields and the higher wind speeds in 3-D trajectories on the one hand and the vertical constraints imposed by the isentropic assumption on the other.