El Salvador: which indicators track drought impact?

lac-dry-corridor 2026-03-13 (endorsed): national average. Main season used here: May–Aug (Primera). Production target: Maize (corn), Beans, dry (FAOSTAT, national, % from 2001–2024 trend).

National mean of ASAP units

Indicator	r with production	R²	Leave-one-out R²	p	AUC, impact seasons	AUC, CERF-dated	AUC, EM-DAT	AUC, framework bad years
Temperature	-0.26	0.07	-0.09	0.222	0.68	0.89	0.54	0.86
Biomass (zFPARc)	+0.27	0.07	-0.09	0.201	0.50	0.61	0.32	0.45
FAO ASI	-0.28	0.08	-2.66	0.192	0.60	0.93	0.44	0.61
FAO mean VHI	+0.15	0.02	-0.12	0.494	0.61	0.68	0.45	0.69
Rainfall (CHIRPS/ASAP)	+0.18	0.03	-0.12	0.387	0.71	0.98	0.59	0.81
Rainfall (ERA5)	+0.06	0.00	-0.16	0.789	0.75	1.00	0.64	0.88
SPI-3	+0.20	0.04	-0.10	0.338	0.66	0.91	0.52	0.76
Water balance	+0.36	0.13	-0.18	0.080	0.68	0.84	0.56	0.82

Combination	R²	Leave-one-out R²	Coefficients (z per sd)
Temperature + Biomass (zFPARc)	0.11	-0.17	-1.94 (p 0.393), +2.12 (p 0.352)
Temperature + Rainfall (CHIRPS/ASAP)	0.07	-0.17	-2.66 (p 0.399), -0.03 (p 0.994)
Temperature + FAO ASI	0.09	-2.63	-1.55 (p 0.553), -1.94 (p 0.458)
Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.09	-0.15	+2.46 (p 0.271), +1.34 (p 0.546)
Temperature + Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.11	-0.25	-1.92 (p 0.555), +2.12 (p 0.364), +0.03 (p 0.991)
Temperature + FAO mean VHI	0.07	-0.18	-2.95 (p 0.317), -0.47 (p 0.872)

Hot vs cool, low vs high biomass (median splits)

Quadrant	Seasons	Mean production anomaly	Impact-season rate	Seasons
hot / low biomass	5	-2.3%	20%	2002, 2015, 2016, 2023, 2024
hot / high biomass	7	-2.7%	29%	2003, 2004, 2009, 2014, 2018, 2019, 2021
cool / low biomass	7	+1.9%	14%	2001, 2007, 2008, 2011, 2013, 2017, 2020
cool / high biomass	5	+3.4%	0%	2005, 2006, 2010, 2012, 2022

Impact seasons (4): 2008, 2014, 2015, 2018.

How impact records were dated to seasons

Record	Period	Season	Rule
CERF 2015 Rapid Response $2.7M	2015-05-01 → 2015-09-28	2015	overlap
CERF 2019 Rapid Response $2.0M	2018-06-01 → 2018-08-28	2018	overlap
CERF 2026 Rapid Response $2.5M	2026-05-01 → 2026-08-28	2026	overlap
EM-DAT 2001-9383-SLV (400000 affected)	2001-05-01 → 2001-12-28	2000	last-season-before-impact
EM-DAT 2009-9415-SLV (n/a affected)	2009-01-01 → 2009-12-28	2008	last-season-before-impact
EM-DAT 2014-9580-SLV (700000 affected)	2015-04-01 → 2016-12-28	2014	last-season-before-impact
EM-DAT 2018-9277-SLV (386610 affected)	2018-06-01 → 2019-03-28	2018	last-season-before-impact

Season table

	t_primera_nat	t_dt_primera_nat	rain_primera_nat	wsi_primera_nat	spi_primera_nat	z_primera_nat	z_dt_primera_nat	t_postrera_nat	t_dt_postrera_nat	rain_postrera_nat	wsi_postrera_nat	spi_postrera_nat	z_postrera_nat	z_dt_postrera_nat	era5_nat	asi_nat	mvhi_nat	prod_anom	impact	impact_cerf	impact_emdat	impact_plus_undated	bad_year
year
2001	26.31	-0.08	84.36	96.39	-0.76	-1.06	-0.81	24.93	-0.32	61.13	96.56	-1.22	-0.54	-0.33	5.36	0.27	0.56	-15.57	0	0	0	0	0
2002	26.79	0.36	93.04	86.89	-0.06	-0.73	-0.49	25.35	0.06	74.30	93.81	-0.39	-0.31	-0.13	6.17	0.22	0.52	-6.03	0	0	0	0	0
2003	26.42	-0.06	99.74	94.90	0.19	-0.06	0.15	25.63	0.30	79.11	97.42	-0.01	0.22	0.39	6.94	0.50	0.56	-8.99	0	0	0	0	0
2004	26.66	0.15	89.69	96.49	-0.11	-0.11	0.08	25.49	0.13	78.87	96.92	-0.25	0.18	0.33	6.41	1.16	0.53	-7.28	0	0	0	0	0
2005	26.11	-0.44	111.90	98.12	0.53	0.36	0.53	25.00	-0.40	99.92	96.51	1.55	0.04	0.17	10.24	0.00	0.60	-0.66	0	0	0	0	0
2006	26.35	-0.23	114.86	98.71	1.14	0.34	0.49	25.41	-0.03	79.83	99.05	-0.02	0.44	0.56	7.36	0.00	0.62	3.32	0	0	0	0	0
2007	26.16	-0.46	80.91	97.96	-1.25	-0.22	-0.09	24.72	-0.75	89.23	96.57	0.75	-0.30	-0.20	7.75	1.96	0.53	-5.35	0	0	0	0	0
2008	25.68	-0.97	113.56	98.20	0.96	-0.31	-0.20	24.59	-0.92	87.29	96.17	0.67	-0.60	-0.51	9.46	0.06	0.60	17.19	1	0	1	1	0
2009	26.74	0.05	93.94	96.24	-0.09	-0.05	0.04	26.17	0.62	71.66	97.79	-0.77	0.13	0.19	6.31	0.08	0.57	4.31	0	0	0	0	1
2010	26.04	-0.69	157.80	99.20	2.42	-0.06	0.01	25.12	-0.46	67.57	93.37	-0.27	-0.82	-0.77	13.41	0.02	0.63	0.12	0	0	0	0	0
2011	26.29	-0.48	106.11	97.10	0.46	-0.16	-0.12	25.04	-0.58	106.56	96.19	1.62	-0.17	-0.14	8.52	0.03	0.62	-2.99	0	0	0	0	0
2012	26.44	-0.36	93.12	98.94	-0.24	0.61	0.63	25.62	-0.04	66.97	96.01	-0.40	0.35	0.37	5.99	0.16	0.55	20.96	0	0	0	0	0
2013	26.72	-0.12	98.87	98.38	0.18	-0.22	-0.22	25.62	-0.07	90.03	99.05	0.50	-0.02	-0.02	6.18	0.23	0.57	14.13	0	0	0	0	0
2014	27.29	0.42	91.55	97.06	-0.19	0.42	0.40	25.46	-0.27	92.58	97.15	0.73	0.20	0.19	5.83	0.19	0.55	7.97	1	0	1	1	1
2015	28.07	1.16	54.80	92.14	-1.99	-0.89	-0.93	26.23	0.47	103.43	91.92	0.44	-0.86	-0.89	4.08	9.62	0.47	-8.20	1	1	0	1	1
2016	27.35	0.41	79.60	97.96	-0.58	-0.25	-0.32	26.28	0.48	61.48	97.60	-1.44	-0.04	-0.09	5.64	0.38	0.55	17.73	0	0	0	0	0
2017	26.68	-0.30	96.95	98.13	0.08	-0.20	-0.28	25.83	-0.01	67.77	97.42	-0.66	0.02	-0.04	8.20	0.15	0.62	11.58	0	0	0	0	0
2018	27.24	0.22	76.02	96.76	-0.67	0.42	0.31	26.08	0.21	79.54	95.06	-0.16	0.08	-0.01	5.28	0.90	0.59	-13.79	1	1	1	1	1
2019	27.51	0.46	76.35	98.41	-1.02	0.23	0.11	26.18	0.27	80.15	98.22	-0.31	0.41	0.31	6.14	0.80	0.57	-2.71	0	0	0	0	0
2020	26.78	-0.31	114.53	97.82	0.98	-0.14	-0.29	25.60	-0.35	105.18	98.92	0.91	0.08	-0.04	9.27	0.83	0.58	-5.76	0	0	0	0	0
2021	27.11	-0.02	94.53	98.80	-0.24	0.60	0.43	26.25	0.27	64.75	97.90	-0.35	0.47	0.34	8.09	0.69	0.57	1.52	0	0	0	0	0
2022	26.44	-0.73	97.94	99.16	0.07	0.50	0.31	25.83	-0.19	79.88	98.85	0.09	0.31	0.16	9.04	0.44	0.60	-6.98	0	0	0	0	0
2023	27.97	0.76	75.46	97.28	-1.09	-0.03	-0.24	26.91	0.86	89.72	98.42	0.25	0.22	0.05	5.59	0.98	0.57	-8.11	0	0	0	0	0
2024	27.21	-0.03	114.15	96.18	1.23	-0.47	-0.71	26.12	0.02	79.73	97.92	-0.46	-0.36	-0.55	10.09	0.82	0.60	-6.96	0	0	0	0	0
2025	27.60	0.33	106.62	95.90	0.56	0.41	0.15	26.27	0.14	91.00	96.51	0.90	0.33	0.13	5.72	0.44	0.57	NaN	0	0	0	0	0