Jack Rabbit II 2015 and 2016 Chlorine Release Field Data Added to JR I and Lyme Bay Field Data in Testing of Similarity Relations for Variations of Maximum Concentrations with Downwind Distance

The Jack Rabbit II (JR II) field experiments, carried out in August and September 2015 and 2016 at the U.S. Army Dugway Proving Ground, Utah, involved nine releases of 4.5 to 20 tons of pressurized liquefied chlorine. In 2015, the releases were inside a “mock urban” array of about 80 CONEX shipping containers set up on a staggered grid in a packed gravel area 122 m square. Outside of the gravel area was a flat desert playa extending many km in all directions. Releases were from a 15 cm hole at the bottom of a tank mounted 1 m above a 25 m diameter concrete pad constructed near the upwind edge of the CONEX array. In 2016, the CONEXs were removed. The 2016 releases were downwards as in 2015 except for one release oriented 45 degrees downward in the downwind direction, and one release upwards. Wind speeds, u, at a height of 2 m ranged from 2 to 5 m/s during the nine JR II trials. Chlorine concentrations C and u were measured on the gravel pad starting at about 50 m upwind of the source, and on 90° arcs at distances, x, of 0.2, 0.5, 1, 2, 5, and 11 km. The 2016 trials involved additional arcs at 0.085 and 0.12 km. The maximum C at the minimum averaging time (1 to 3 seconds) was identified on each downwind distance arc. Previously we presented graphs in which it was shown that C­_maxu/Q varied with x^-5/3 for other chlorine release data from the 1927 Lyme Bay and the 2010 JR I field experiments. In this formula, C_max is arc-maximum concentration in mass per unit volume, and Q is average chlorine mass emission rate to the atmosphere over the observed duration of visible release. It is found that within reasonable uncertainty bounds the JR II observations follow the same power law.