TRAJECTORIESPage 2 of 61 2 3 4 5 6 What is a trajectory? A trajectory is the time integration of the position of a parcel of air as
it is transported by the wind. The parcel's passive transport by the wind is
computed from the average of the three-dimensional velocity vectors at the
particle's initial-position P(t) and its first-guess position
P'(t+dt). The velocity vectors are interpolated in both space and time.
P'(t+dt) = P(t) + V(P,t) dt,
and the final position is
P(t+dt) = P(t) + 0.5 [ V(P,t) + V(P',t+dt) ] dt
Trajectories may be integrated both forward and backward in time. A
measure of the integration error may be obtained by computing a backward trajectory
from the end-point-position of its forward counterpart.
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