Climatological Drought Analyses Using Spi, Deciles, Ppn, Edi and Rainy Days in Chile

doi:10.21203/rs.3.rs-159170/v2

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Climatological Drought Analyses Using Spi, Deciles, Ppn, Edi and Rainy Days in Chile

https://doi.org/10.21203/rs.3.rs-159170/v2

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Since 2010, a large area of Chile is in a period of severe drought, with impacts on the population and the water resource systems. Therefore, it is necessary to carry out research on drought behavior in Chile, its prediction and monitoring, should be addressed to find suitable measures to reduce its effects. A simple calculation model is presented for the SPI, PPN, DEC and EDI indexes. Based on the hypothesis that these indexes are an indicator of the drought condition in the central-southern area of Chile; the proposed model takes as the only input variable the cumulative number of raining days. The most efficient index for the model is identified, the study is regionalized and temporal and spatial analysis of the model is carried out. A modified index of drought is obtained, based on a simple rainfall day counter. The model represents an efficient method to show a drought event.

drought

SPI

rainy days

drought in Chile

Table 1

Drought classification based on indices.

Category	PPN	Deciles	SPI	EDI
Extreme drought	PPN ≤ 25	1	SPI ≤ -2	EDI ≤ -2
Severe drought	25 < PPN ≤ 50	2	-2 < SPI ≤ -1.5	-2 < EDI ≤ -1.5
Moderate drought	50 < PPN ≤ 75	3	-1.5 < SPI ≤ -0.84	-1.5 < EDI ≤ -0.84
Normal	75 < PPN ≤ 125	4 a 7	-0.84 < SPI ≤ 0.84	-0.84 < EDI ≤ 0.84
Moderately wet	125 < PPN ≤ 150	8	0.84 < SPI ≤ 1.5	0.84 < EDI ≤ 1.5
Severely wet	150 < PPN ≤ 250	9	1.5 < SPI ≤ 2	1.5 < EDI ≤ 2
Extremely wet	PPN > 250	10	SPI > 2	EDI > 2

Table 2

Model analysis for station i.

Year / Month	Real	Estimated	(1) Exactly right	(2) Measured drought?	(3) Drought modeling?	(4) Drought condition is certain	(5) identified drought
19861	20	26	NO	YES	YES	NO	YES
19862	60	90	NO	NO	YES	NO	NO
...	...	...	...	...	...	...	...
201612	...	...	...	...	...	...	...
-	-	-	% successes	% of total	% of total	% of total measured drought events	% of total measured drought events

Table 3

Results of SPI model.

Station	(1) Exact success	(2) SPI drought?	(3) SPI* drought?	(4) Drought condition is certain	(5) Identified drought	Coefficient of determination (R²)
1	…	…	…	…	…	...
…	…	…	…	…	…	...
145	…	…	…	…	…	...
Minimum	50.3%	14.2%	1.9%	1.4%	9.6%	0.23
Mean	63.2%	20.3%	14.1%	31.7%	49.8%	0.66
Maximum	75.5%	25%	20.4%	57.7%	76.7%	0.82

Table 4

Results of PPN model.

Station	(1) Exact success	(2) SPI drought?	(3) SPI* drought?	(4) Drought condition is certain	(5) Identified drought	Coefficient of determination (R²)
Minimum	36.3%	5.6%	0.0%	0.0%	0.0%	0.19
Mean	63.1%	26.6%	19.0%	40.0%	53.8%	0.65
Maximum	91.1%	47.6%	43.5%	71.4%	91.7%	0.83

Table 5

Results of DECILES model.

Station	(1) Exact success	(2) SPI drought?	(3) SPI* drought?	(4) Drought condition is certain	(5) Identified drought	Coefficient of determination (R²)
Minimum	36.8%	29.0%	0.5%	0.0%	1.9%	0.17
Mean	47.3%	29.0%	18.0%	19.3%	48.8%	0.61
Maximum	58.9%	29.0%	29.3%	37.0%	71.3%	0.79

Table 6

Results of EDI model.

Station	(1) Exact success	(2) SPI drought?	(3) SPI* drought?	(4) Drought condition is certain	(5) Identified drought	Coefficient of determination (R²)
Minimum	54.0%	9.4%	0.0%	0.0%	0.0%	0.11
Mean	63.2%	19.3%	8.6%	22.8%	30.9%	0.46
Maximum	76.6%	23.7%	16.4%	61.3%	67.7%	0.66

Table 7

Review of model results for the three homogeneous regions.

Index	Region	(1) Exactly right	(2) Measured drought?	(3) Drought modeling?	(4) Drought condition is certain	(5) identified drought	Coefficient of determination (R²)
SPI	1	62%	20%	16%	32%	52%	0.69
	2	65%	20%	14%	36%	50%	0.69
	3	63%	21%	13%	27%	47%	0.60
PPN	1	49%	40%	33%	41%	70%	0.68
	2	60%	28%	19%	42%	53%	0.67
	3	77%	14%	8%	36%	41%	0.60
DEC	1	47%	29%	19%	17%	51%	0.65
	2	48%	29%	18%	20%	48%	0.62
	3	47%	29%	17%	20%	47%	0.57
EDI	1	68%	17%	9%	32%	35%	0.53
	2	62%	20%	9%	22%	31%	0.48
	3	60%	21%	8%	16%	28%	0.39

Table 8

A and B coefficients for Region 1.

Station	A	B	Station	A	B
Alicahue	2.508	-7.341	Las Puertas	2.071	-5.785
Artificio	2.355	-6.541	Lliu Lliu Embalse	2.757	-8.918
Casablanca	2.756	-8.426	Lo Rojas	2.675	-8.123
Catemu	2.579	-7.574	Longotoma	1.857	-5.151
Cerro Calán	3.409	-11.614	Los Andes	2.309	-6.944
Chacrilla	1.983	-5.413	Los Aromos	2.739	-8.66
Chalaco	2.19	-6.2	Los Panguiles	3.377	-10.849
Colliguay	2.629	-8.15	Mina Cerro Negro	1.979	-5.64
El Pedernal Hda	2.669	-7.588	Palquico	2.633	-7.765
El Salvador	2.283	-6.324	Pudahuel Stgo	2.894	-8.885
El Sobrante Hda	2.506	-7.043	Quillota	2.812	-8.616
El Trapiche	2.616	-7.526	Quinta Normal	3.073	-9.745
Estero Rabuco	2.58	-7.625	R. Los Patos	2.288	-6.759
Frutillar Alto	2.24	-6.333	Riecillos	2.573	-8.527
Fdo Las Bateas	2.476	-7.396	R. De Los Valles	2.399	-7.053
Hierro Viejo	2.133	-5.752	Rodelillo	2.536	-8.233
La Mostaza	2.217	-6.454	San Felipe	2.545	-7.324
La Viña	2.334	-6.638	Santiago (Ofcs Dga)	2.833	-9.09
Las Colmenas	2.029	-5.439	Valle Hermoso	2.117	-5.913
Las Pataguas	2.403	-7.071	Vilcuya	3.083	-10.179

Table 9

A and B coefficients for Region 2.

Station	A	B	Station	A	B
Ancoa Embalse	4.892	-20.532	Los Queñes	3.911	-15.381
Antupirén	3.227	-10.937	Melipilla	3.047	-9.862
Armerillo	4.109	-16.938	Melozal	4.708	-18.724
Barrera Loncha	2.784	-9.209	Millahue	2.64	-9.116
C. De Las Rosas	2.325	-7.06	Nilahue Barahona	3.885	-14.036
Cerrillos De Leyda	2.789	-9.359	Nirivilo	3.013	-11.448
Cocalán	2.874	-10.028	Pencahue	4.189	-16.146
Colbún (Maule Sur)	2.64	-10.333	Pichidegua	3.206	-10.828
Colorado	4.338	-17.693	Pichilemu	3.422	-12.349
Coltauco	3.379	-11.582	Pirque	3.035	-10.225
Convento Viejo	3.826	-14.191	Popeta	3.376	-11.875
Curicó	3.958	-14.796	Potrero Grande	4.175	-16.226
El Guindo	3.604	-13.444	Quella	3.258	-12.768
El Manzano	3.835	-14.496	Rancagua	3.366	-11.711
El Membrillo	3.133	-11.182	Ranguilí	4.056	-15.254
El Yeso Embalse	3.545	-13.077	Rapel	2.739	-9.492
E. S. Tobalaba Ad	2.675	-8.513	Rengo	3.287	-11.819
G. Freire Curicó Ad	3.927	-14.619	San Antonio	2.807	-9.069
Gualleco	3.447	-12.962	San Fernando	3.999	-14.62
Huapi	3.551	-13.755	San Gabriel	2.463	-8.35
La Candelaria	3.639	-13.205	San Javier	4.841	-18.966
La Palma	2.269	-8.274	San José De Maipo	3.375	-11.454
La Rufina	2.958	-10.432	Santa Susana	2.941	-10.986
Lago Peñuelas	2.88	-9.457	Santo Domingo Ad	3.332	-11.14
Linares	4.924	-19.827	Talca UC	4.381	-17.171
Litueche	3.434	-12.221	Tutuvén Embalse	4.373	-17.019
Lontué	3.664	-13.677	Villa Alhué	2.624	-8.401

Table 10

A and B coefficients for Region 3.

Station	A	B	Station	A	B
B. O' Higgins Chillán	5.621	-23.683	Lautaro	3.861	-17.879
Bullileo Embalse	5.247	-22.521	Liguay	4.197	-16.89
Cañete	5.491	-25.706	Llafenco	7.803	-39.032
Caracol	4.979	-21.885	Los Ángeles	6.386	-28.442
Carriel Sur (DMC)	5.845	-25.389	Los Laureles	3.995	-19.318
Cerro El Padre	4.633	-21.411	Lumaco	4.463	-20.797
Chillán Viejo	5.267	-22.448	Maquehue Temuco	6.511	-30.725
Chillancito	3.733	-15.477	Mulchén	5.601	-25.162
Cholguán	4.292	-18.544	Nueva Aldea	1.721	-7.246
Coelemu	3.226	-13.15	Parral	4.569	-19.076
Coihueco Embalse	5.173	-22.539	Pemuco	4.159	-17.378
Cunco	3.917	-17.889	Pucón	7.15	-35.433
Curacautín	4.568	-21.857	Pueblo Nuevo	5.546	-26.466
Curarrehue	5.824	-28.62	Puerto Saavedra	6.003	-28.598
Dichato	4.738	-20.281	Quilaco	5.696	-25.924
Digua Embalse	5.297	-22.67	Quillén	4.889	-22.695
Diguillín Embalse	5.896	-26.257	Quitratúe	4.618	-22.573
Freire Sendos	4.764	-22.676	S. Carlos De Purén	4.832	-21.42
Fundo Atacalco	5.617	-24.949	San Fabián	4.276	-18.046
Galvarino	4.418	-19.804	S. Perquilauquén	4.77	-20.354
Hornillo	4.377	-18.151	Traiguén	5.21	-23.988
Laguna Malleco	4.475	-21.038	Trupán	3.652	-16.467
Laja	4.219	-18.423	Tucapel	4.537	-20.032
Las Achiras	4.441	-19.979	Vilcún	3.353	-15.715
Las Mercedes	5.074	-23.287	Villarrica	5.561	-26.867
Las Trancas	4.498	-19.084

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Editorial decision: Minor Revisions Needed
01 Oct, 2022
Reviewers agreed at journal
28 Aug, 2022
Reviewers invited by journal
28 Aug, 2022
Editor assigned by journal
09 Sep, 2021
First submitted to journal
08 Sep, 2021

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Climatological Drought Analyses Using Spi, Deciles, Ppn, Edi and Rainy Days in Chile

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