Chad: which indicators track drought impact?

tcd-drought 2025-03-03 (endorsed): SEAS5 JAS + GeoSahel biomass over 7 Sahelian provinces. Main season used here: Jul–Sep. Production target: Millet, Sorghum (FAOSTAT, national, % from 2001–2024 trend).

Framework area

Indicator	r with production	R²	Leave-one-out R²	p	AUC, impact seasons	AUC, CERF-dated	AUC, EM-DAT
Temperature	-0.38	0.14	-0.03	0.068	0.76	0.86	0.75
Biomass (zFPARc)	+0.41	0.17	-0.03	0.048	0.75	0.92	0.71
FAO ASI	-0.38	0.15	-0.00	0.064	0.81	0.76	0.78
FAO mean VHI	+0.43	0.18	-0.06	0.036	0.67	0.86	0.62
Rainfall (CHIRPS/ASAP)	+0.15	0.02	-0.29	0.470	0.73	0.87	0.70
Rainfall (ERA5)	+0.18	0.03	-0.64	0.407	0.78	0.82	0.78
SPI-3	+0.35	0.12	-0.12	0.094	0.70	0.81	0.72
Water balance	+0.39	0.15	-0.13	0.058	0.64	0.76	0.70

Combination	R²	Leave-one-out R²	Coefficients (z per sd)
Temperature + Biomass (zFPARc)	0.18	-0.07	-3.30 (p 0.567), +5.44 (p 0.349)
Temperature + Rainfall (CHIRPS/ASAP)	0.15	-0.22	-8.45 (p 0.093), -1.94 (p 0.690)
Temperature + FAO ASI	0.18	-0.06	-4.53 (p 0.346), -4.79 (p 0.320)
Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.17	-0.24	+8.32 (p 0.071), -0.93 (p 0.834)
Temperature + Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.19	-0.25	-4.49 (p 0.484), +5.64 (p 0.342), -2.29 (p 0.640)
Temperature + FAO mean VHI	0.20	-0.08	-3.25 (p 0.524), +6.19 (p 0.230)

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

Quadrant	Seasons	Mean production anomaly	Impact-season rate	Seasons
hot / low biomass	11	-7.7%	27%	2002, 2004, 2006, 2008, 2009, 2011, 2013, 2014, 2015, 2017, 2023
hot / high biomass	1	-8.2%	100%	2021
cool / low biomass	1	+6.7%	0%	2019
cool / high biomass	11	+7.4%	9%	2001, 2003, 2005, 2007, 2010, 2012, 2016, 2018, 2020, 2022, 2024

Impact seasons (5): 2009, 2011, 2016, 2017, 2021.

National mean of ASAP units

Indicator	r with production	R²	Leave-one-out R²	p	AUC, impact seasons	AUC, CERF-dated	AUC, EM-DAT
Temperature	-0.36	0.13	-0.04	0.083	0.80	0.82	0.81
Biomass (zFPARc)	+0.42	0.18	-0.03	0.041	0.72	0.82	0.75
FAO ASI	-0.31	0.10	-0.08	0.138	0.59	0.51	0.57
FAO mean VHI	+0.40	0.16	-0.08	0.056	0.69	0.79	0.65
Rainfall (CHIRPS/ASAP)	+0.11	0.01	-0.26	0.598	0.63	0.71	0.65
Rainfall (ERA5)	+0.15	0.02	-0.64	0.475	0.76	0.76	0.78
SPI-3	+0.36	0.13	-0.11	0.080	0.70	0.73	0.71
Water balance	+0.46	0.21	+0.01	0.025	0.67	0.78	0.76

Combination	R²	Leave-one-out R²	Coefficients (z per sd)
Temperature + Biomass (zFPARc)	0.19	-0.09	-3.14 (p 0.525), +6.18 (p 0.217)
Temperature + Rainfall (CHIRPS/ASAP)	0.14	-0.19	-8.32 (p 0.091), -2.42 (p 0.613)
Temperature + FAO ASI	0.15	-0.10	-5.29 (p 0.251), -3.40 (p 0.457)
Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.18	-0.19	+7.99 (p 0.050), +1.38 (p 0.723)
Temperature + Biomass (zFPARc) + Rainfall (CHIRPS/ASAP)	0.19	-0.24	-3.37 (p 0.605), +6.07 (p 0.271), -0.29 (p 0.955)
Temperature + FAO mean VHI	0.17	-0.10	-3.50 (p 0.495), +5.39 (p 0.296)

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

Quadrant	Seasons	Mean production anomaly	Impact-season rate	Seasons
hot / low biomass	8	-5.0%	50%	2002, 2006, 2009, 2011, 2014, 2015, 2017, 2021
hot / high biomass	4	+2.9%	25%	2004, 2010, 2016, 2023
cool / low biomass	4	-6.9%	0%	2001, 2013, 2019, 2024
cool / high biomass	8	+6.4%	0%	2003, 2005, 2007, 2008, 2012, 2018, 2020, 2022

Impact seasons (5): 2009, 2011, 2016, 2017, 2021.

How impact records were dated to seasons

Record	Period	Season	Rule
CERF 2010 Rapid Response $3.8M	2009-06-01 → 2009-09-28	2009	overlap
CERF 2011 Rapid Response $6.0M	2011-06-01 → 2011-09-28	2011	overlap
CERF 2018 Rapid Response $10.2M	2017-06-01 → 2017-10-28	2017	overlap
CERF 2026 Rapid Response $4.4M	2026-07-01 → 2026-09-28	2026	overlap
EM-DAT 2001-9044-TCD (800000 affected)	2001-01-01 → 2001-12-28	2000	last-season-before-impact
EM-DAT 2009-9654-TCD (2400000 affected)	2009-12-01 → 2010-07-28	2009	last-season-before-impact
EM-DAT 2012-9160-TCD (1600000 affected)	2012-06-01 → 2013-02-28	2011	last-season-before-impact
EM-DAT 2017-9342-TCD (1886800 affected)	2017-03-01 → 2017-05-28	2016	last-season-before-impact
EM-DAT 2022-9335-TCD (2135362 affected)	2022-06-01 → 2022-08-28	2021	last-season-before-impact

Season table

	t_JAS_aoi	t_dt_JAS_aoi	rain_JAS_aoi	wsi_JAS_aoi	spi_JAS_aoi	z_JAS_aoi	z_dt_JAS_aoi	t_JAS_nat	t_dt_JAS_nat	rain_JAS_nat	wsi_JAS_nat	spi_JAS_nat	z_JAS_nat	z_dt_JAS_nat	era5_nat	era5_aoi	asi_nat	asi_aoi	mvhi_nat	mvhi_aoi	prod_anom	impact	impact_cerf	impact_emdat	impact_plus_undated
year
2001	27.97	-0.06	34.76	75.41	0.36	0.20	0.49	26.57	-0.18	65.26	86.59	0.81	-0.05	-0.12	2.76	3.35	0.04	0.06	0.62	0.64	-8.55	0	0	0	0
2002	28.75	0.71	31.91	66.31	-0.56	-0.61	-0.35	27.24	0.47	50.98	79.63	-0.72	-0.32	-0.37	2.23	2.74	5.43	4.61	0.48	0.50	-17.20	0	0	0	0
2003	27.64	-0.42	36.88	79.68	0.62	0.32	0.55	26.50	-0.30	55.69	86.95	0.40	0.25	0.20	2.72	3.48	3.29	0.06	0.54	0.60	3.36	0	0	0	0
2004	28.55	0.46	24.63	65.14	-0.86	-0.52	-0.31	27.00	0.19	47.77	81.95	-0.74	0.23	0.18	2.13	2.33	5.12	2.96	0.49	0.50	-30.81	0	0	0	0
2005	27.76	-0.34	38.06	82.35	1.05	0.47	0.66	26.71	-0.12	56.58	90.14	0.58	0.48	0.44	2.81	3.55	0.04	0.09	0.58	0.62	1.95	0	0	0	0
2006	28.58	0.46	32.11	70.60	-0.14	-0.62	-0.45	27.13	0.27	56.72	83.95	0.18	-0.22	-0.26	2.20	2.70	0.64	0.19	0.55	0.60	18.79	0	0	0	0
2007	27.76	-0.38	30.09	69.87	-0.14	0.44	0.58	26.59	-0.29	50.81	83.25	-0.20	0.43	0.39	2.42	2.80	1.81	0.30	0.56	0.63	-9.19	0	0	0	0
2008	28.20	0.04	30.13	67.27	-0.08	-0.35	-0.23	26.77	-0.13	54.97	81.03	0.28	0.13	0.11	2.41	2.81	0.62	0.01	0.61	0.68	-8.31	0	0	0	0
2009	29.27	1.09	26.21	65.55	-1.06	-0.62	-0.53	27.65	0.73	47.22	79.08	-0.82	-0.44	-0.46	2.02	2.28	3.81	1.15	0.50	0.59	-26.20	1	1	1	1
2010	28.12	-0.08	38.04	81.80	0.65	0.27	0.34	26.87	-0.06	58.26	89.77	0.75	0.09	0.08	2.94	3.63	0.15	0.24	0.63	0.71	38.71	0	0	0	0
2011	28.72	0.50	29.20	63.02	-0.39	-0.82	-0.77	27.17	0.22	54.37	79.63	0.09	-0.48	-0.49	2.20	2.34	0.90	0.64	0.56	0.58	-25.73	1	1	1	1
2012	27.66	-0.57	34.44	84.19	0.87	0.88	0.91	26.48	-0.49	55.99	90.60	0.86	0.71	0.70	2.70	3.15	0.29	0.02	0.68	0.75	49.65	0	0	0	0
2013	28.25	-0.00	24.06	63.42	-0.82	-0.30	-0.30	26.89	-0.10	49.39	80.59	-0.20	-0.09	-0.09	2.25	2.78	1.08	0.54	0.60	0.64	-2.01	0	0	0	0
2014	28.50	0.23	33.62	66.80	-0.26	-0.51	-0.53	27.12	0.10	54.12	79.96	-0.29	-0.33	-0.32	2.22	2.77	5.18	0.25	0.56	0.63	14.13	0	0	0	0
2015	29.13	0.84	31.39	64.48	-0.59	-0.53	-0.58	27.73	0.70	51.89	80.98	-0.60	-0.62	-0.61	1.98	2.30	8.83	4.23	0.50	0.56	-1.55	0	0	0	0
2016	28.26	-0.05	31.67	78.15	0.14	0.20	0.13	27.18	0.12	53.38	87.44	0.08	0.15	0.17	2.46	3.14	1.33	0.80	0.59	0.65	15.71	1	0	1	1
2017	28.67	0.34	30.97	77.90	-0.01	-0.30	-0.39	27.24	0.16	54.79	87.83	0.05	-0.05	-0.02	2.25	2.64	3.73	2.15	0.55	0.60	5.87	1	1	0	1
2018	27.88	-0.46	35.43	81.03	0.88	0.71	0.59	26.90	-0.20	54.05	90.14	0.38	0.28	0.31	2.63	3.21	3.93	0.39	0.63	0.72	12.45	0	0	0	0
2019	28.09	-0.28	40.30	76.88	0.88	-0.22	-0.37	27.01	-0.11	61.76	87.62	0.71	-0.15	-0.12	2.56	2.81	0.94	0.16	0.65	0.67	6.65	0	0	0	0
2020	27.80	-0.58	40.64	81.46	0.53	0.23	0.06	26.83	-0.30	57.54	89.08	-0.12	0.11	0.15	2.51	3.13	2.37	0.40	0.64	0.72	2.37	0	0	0	0
2021	28.61	0.21	37.27	73.68	0.23	0.07	-0.12	27.37	0.21	56.90	84.69	-0.02	-0.17	-0.12	1.85	2.10	6.46	2.26	0.60	0.66	-8.17	1	0	1	1
2022	28.07	-0.35	46.51	87.65	1.29	0.62	0.41	26.81	-0.37	67.91	92.11	1.30	0.07	0.12	2.45	2.62	5.74	0.48	0.65	0.74	-1.48	0	0	0	0
2023	29.86	1.41	33.04	73.14	0.44	-0.02	-0.26	28.08	0.88	51.85	86.13	0.13	0.09	0.14	1.42	1.37	4.52	1.45	0.61	0.65	-12.09	0	0	0	0
2024	27.69	-0.77	52.45	93.07	1.74	0.64	0.38	26.83	-0.39	71.90	92.12	1.37	-0.10	-0.04	4.16	5.47	1.84	0.60	0.70	0.78	-23.62	0	0	0	0
2025	28.37	-0.11	42.41	80.40	0.58	0.57	0.28	27.07	-0.17	66.54	85.26	0.57	-0.06	0.01	2.07	2.10	11.50	1.50	0.62	0.72	NaN	0	0	0	0