while Dpeak is the maximum duration fraction in the pollen sampling
period prior to that (0900–1000 EDT, ‘‘decrease’’) or just after it
(‘‘increase’’, 1100–1200 EDT, see Fig. 14b). Fig. 15 shows that at
the lowest threshold value, Dpeak/Dtrough 1.1 for 16 July and
1.3 for 17 July. As the threshold is increased, Dpeak/Dtrough
increases for both days, the fastest for 17 July as Dtrough is
strongly reduced and becomes near zero at the higher thresholds.