Table S1.

Parameters of the ³⁵S box model for calculating ³⁵SO₄²⁻ in San Diego, California

Parameter	Value
Height, km
Planetary boundary layer (box 1)	0.6
Buffer layer (box 2)	1.0
Free troposphere (box 3)	8.0
Lower stratosphere (box 4)	16.0
Cosmic ray production rate of 35S (atoms cm−3 d−1)
P1	2.8 × 10−6
P2	2.8 × 10−6
P3	6.5 × 10−5
P4	1.1 × 10−4
35SO2 lifetime (d)
τox−1 = τox−2	4 (8)*
τox−3 = τox−4	8
τd	1.5
τc1 = τc2	5 (∞)*
τc3 = τc4	143
τλ	126
35SO42− removal lifetime (d)
τr1 = τr2	12 (3)*
τr3	24
τr4	365
Air mass mixing time (d)
τ12 = τ21	1 (τ12 = ∞)*
τ23 = τ32	14 (τ12 = ∞)*
τ34 = τ43	290
τH	30
τHS	1

The San Diego ³⁵S box model and input parameters are adopted from refs. 18 and 28.

^*Values in parentheses represent those during the Santa Ana period (April 29 to May 3, 2014) as used in ref. 18.