Table 4.

Percentage (%) and absolute (Diff.) changes in parameters, including air temperature (T), specific humidity (Hum), surface pressure (Pres), the planetary boundary layer height (PBLH), and surface concentrations of dust, sea salt (Salt), black carbon (BC), organic carbon (OC), SO₂, SO₄, and NO₂ in the eleven urban environments over the CONUS between March–May of 2020 and 2019. The table also shows the correlation coefficient of all parameters with PM_2.5 in 2019 (R2019) and 2020 (R2020). The units for the parameters are as follows: T (k), Hum (10⁻³ kg/kg), Pres (millibars), PBL (m), Dust (10⁻¹¹ kg/m³), Salt (10⁻¹¹ kg/m³), BC (10⁻¹¹ kg/m³), OC (10⁻¹¹ kg/m³), SO₂ (10⁻¹¹ kg/m³), SO₄ (10⁻¹¹ kg/m³), NO₂ (ppb), and PM_2.5 (μg/m³).

		T	Hum	Pres	PBLH	Dust	Salt	BC	OC	SO2	SO4	NO2	PM2.5
Washington DC	R2019	0.07	0.16	0.20	−0.36	0.10	−0.16	0.45	0.37	0.38	0.31	0.42	–
	R2020	0.13	0.12	0.21	−0.16	0.25	−0.14	0.50	0.32	0.49	0.00	0.63	–
	Diff.	−1.56	−1	−9.31	64.00	20.9	36	−8.53	−64.5	−4.51	−0.57	2.42	−1.37
	%	−0.55	−14.7	−0.01	8.05	14.62	22.22	−8.81	−17.4	−7.70	−0.17	−23.6	−21.1
New York	R2019	−0.08	0.06	0.18	−0.37	0.02	−0.01	0.57	0.40	0.53	0.32	0.64	–
	R2020	0.13	0.17	0.12	−0.45	−0.04	0.00	0.65	0.68	0.51	0.11	0.70	–
	Diff.	−0.65	−0.7	−63.6	87.9	22.4	39.3	−8.3	−45.9	−52.9	−29.4	−3.62	−1.52
	%	−0.23	−10.2	−0.06	12.53	17.54	17.87	−7.69	−13.7	−5.36	−7.94	−26.6	−20.7
Boston	R2019	−0.35	−0.25	0.41	−0.19	−0.07	−0.14	0.64	0.36	0.71	0.09	0.70	–
	R2020	0.06	0.05	0.18	−0.37	−0.05	0.04	0.59	0.54	0.67	0.23	0.51	–
	Diff.	0.17	−0.4	−89	50.3	22.4	104	−4.50	−6.69	13.5	−23.2	−2.57	−1.18
	%	0.06	−7.33	−0.09	7.04	21.80	42.22	−6.24	−2.82	3.37	−8.34	−28.1	−18.5
Los Angeles	R2019	0.75	0.14	0.00	−0.26	0.27	0.01	0.71	0.75	0.59	0.29	0.44	–
	R2020	0.81	0.11	−0.13	−0.61	0.44	0.42	0.78	0.62	0.62	0.12	0.39	–
	Diff.	0.84	−0.1	42.2	−4.27	32.8	26.2	2.4	22.3	−13.7	−29.8	−1.54	−0.22
	%	0.29	−1.99	0.04	−0.61	19	16.95	3.76	9.70	−1.69	−11.4	−15.6	−3.29
Chicago	R2019	−0.14	−0.15	0.32	−0.22	0.17	−0.46	0.54	0.29	0.62	0.31	0.72	–
	R2020	0.02	0.03	−0.03	−0.38	−0.07	−0.35	0.63	0.45	0.56	0.48	0.60	–
	Diff.	0.24	0	20.70	44.60	6.22	17.3	−5.20	−66.9	−66.5	3.22	−2.37	−0.66
	%	0.09	−0.12	0.02	6.95	3.56	15.06	−5.94	−19.3	−8.42	0.87	−17.4	−8.05
Houston	R2019	0.27	0.30	−0.16	−0.02	0.11	0.47	0.20	0.24	0.18	0.09	0.00	–
	R2020	0.33	0.36	−0.32	−0.13	−0.28	0.30	0.30	0.31	−0.01	−0.10	0.10	–
	Diff.	1.73	0.2	−24.2	15.15	12.4	−1.51	2.30	23.6	−19.6	−13.5	−1.36	−0.34
	%	0.59	1.79	−0.02	2.12	8.31	−25.2	7.21	9.06	−2.95	−6.31	−18.7	−3.63
Philadelphia	R2019	−0.09	0.02	0.22	−0.23	0.02	−0.19	0.57	0.30	0.50	0.34	0.51	–
	R2020	0.13	0.13	0.10	−0.22	0.04	−0.05	0.47	0.57	0.44	0.07	0.66	–
	Diff.	−1.24	−0.9	−37.5	67.5	26.8	35	−14.8	−157	−70.8	−3.54	1.67	−0.33
	%	−0.44	−12.6	−0.04	8.48	20.1	21.23	−9.94	−31	−8.59	−1.04	−16	−4.82
Detroit	R2019	−0.13	−0.10	0.34	−0.21	0.09	−0.38	0.59	0.24	0.62	0.18	0.74	–
	R2020	0.02	0.05	0.06	−0.52	0.01	−0.29	0.75	0.59	0.65	0.47	0.69	–
	Diff.	−0.06	−0.1	12.7	60.2	−17.9	15	−4.30	−71.7	−19.4	−40.9	−3.1	−1.16
	%	−0.02	−2.4	0.01	8.87	−9.17	13.11	−6.48	−24	−2.39	−10.3	−24.1	−13.5
Phoenix	R2019	0.34	−0.04	0.23	−0.37	−0.11	−0.38	0.65	0.32	0.73	0.37	0.59	–
	R2020	0.81	−0.36	−0.25	0.15	0.28	0.07	0.38	0.70	0.00	0.09	0.39	–
	Diff.	1.06	0.1	103	−19.2	−29.7	24.8	5.88	22.6	7.57	14.2	1.73	0.28
	%	0.36	2.17	0.11	−1.50	−4.28	33.43	10.52	13.06	3.72	11.39	−13.2	5.50
Dallas	R2019	0.00	−0.02	0.22	−0.14	−0.11	0.18	0.20	0.17	0.48	0.36	0.38	–
	R2020	0.27	0.24	−0.21	−0.13	−0.26	0.22	0.25	0.27	0.37	0.10	0.19	–
	Diff.	1.42	0	4.35	−20.2	20.1	−37.2	−0.7	−40.8	−6.64	−6.47	−0.68	−0.54
	%	0.49	0.75	0.00	−2.76	11.03	−20	−1.48	−11.5	−1.82	−2.56	−11.6	−6.71
Seattle	R2019	0.17	0.13	0.17	−0.18	0.25	−0.29	0.35	0.47	0.56	−0.17	0.56	–
	R2020	−0.11	−0.24	0.16	−0.41	0.23	−0.22	0.52	0.52	0.81	−0.07	0.69	–
	Diff.	−1.05	−0.4	81.1	77.2	3.07	8.09	−3.44	−39.2	−9.68	−1.65	3.42	−0.42
	%	−0.37	−6.9	0.08	12.10	3.11	5.99	−5.15	−16	−3.97	−1.08	−24.3	−7.73