Droughts over Pakistan: possible cycles, precursors and associated mechanisms

Figures & data

Table 1. List of weather stations in Pakistan.

Station no.	Station name	Elevation (MSL)	Latitude (^0N)	Longitude (^0E)
1	Nokkundi	682	28.81	62.76
2	Dalbadin	848	28.98	64.46
3	Panjgur	968	26.75	64.00
4	Lasbella	87	26.23	66.62
5	Khuzdar	1231	27.50	66.38
6	Kalat	2015	29.17	66.44
7	Sibbi	133	29.55	67.88
8	Quetta	1626	30.2	66.58
9	Zhob	1405	31.21	69.28
10	Barkhan	1097	29.92	69.74
11	Jacobabad	55	28.59	68.47
12	Badin	09	24.61	68.62
13	Hyderabad	28	25.23	68.25
14	Chhor	05	25.67	69.30
15	Padidan	46	26.91	67.98
16	Khanpur	88	28.67	70.66
17	Bahawalpur	110	29.35	71.93
18	Bahawalnagar	161	29.96	73.21
19	Multan	122	30.49	71.33
20	Lahore	214	31.52	74.40
21	Sargodha	187	32.14	72.76
22	Sialkot	255	32.52	74.65
23	Jhelum	287	32.96	73.76
24	Mianwali	210	32.71	71.55
25	D.I.Khan	171	31.93	70.85
26	Peshawar	327	34.11	71.61
27	Balakot	995	34.79	73.45
28	Chitral	1498	36.06	71.74
29	Sakardu	2317	35.39	75.66
30	Gilgit	1460	36.02	74.49

Figure 1. (a) Spatial rainfall distribution map of Pakistan (1981-2017), (b) Anomalous precipitation patterns in Pakistan (1981–2017).

Figure 2. Pakistan's standardized total rainfall for June-August from 1981 to 2017. The solid blue line represents 11-year running mean.

Table 2. Standard Single Z-Index criteria for categorizing years based on the severity of floods or droughts.

Sr. No	Grades	Single Z-index	Probabilities (%)
1	Extreme flood	Z ≥ 1.645	5
2	Severe flood	1.0367≤ Z < 1.645	10
3	Mild flood	0.5244 < Z < 1.0367	15
4	Normal	−0.5244 ≤ Z ≤ 0.5244	40
5	Mild drought	−1.0367 < Z < −0.5244	15
6	Severe drought	−1.645 < Z < −1.0367	10
7	Extreme drought	Z ≤ −1.645	5

Figure 3. (a) Time series of the SPI and Single Z-Index on Pakistan's rainfall. (b) Scatter diagram of the SPI and Z score for Pakistan's rainfall (1981-2017). Positive values indicate wetter than normal, negative values drier than normal.

Table 3. Grading of 1981 – 2017 period into flood, normal and drought years based on Pakistan's average summer rainfall and their probabilities.

Grade	Extreme drought	Severe drought	Mild drought	Normal	Mild flood	Severe flood	Extreme flood
Flood/Drought years	1987 2002	1991 2000 2001 2005	1982,1985, 1993,1999, 2004, 2009	1981, 1984, 1986, 1990, 1996, 1997, 1998, 2015, 2016, 2017	1983, 1989, 1992, 2003, 2006, 2008, 2011, 2012, 2013	1988 1995 2007 2010 2014	1994
Total	2	4	6	10	9	5	1
Probability (%)	5.4	10.8	16.2	27.1	24.3	13.5	2.7

Table 4. Correlation coefficients of Pakistan JJA composite droughts and selected meteorological parameters. The correlations are significant at 95%confidence level. All the values with asterisks are considered to be significant at 95% confidence interval. Shaded cells are chosen for further analysis.

	OND	NDJ	DJF	JFM	FMA	MAM
Air Temperature (2 m)	0.60	0.01	−0.01	−0.32*	0.12	0.50
SLP	−0.37	−0.81	−0.85	−0.71*	−0.53*	−0.58*
SST	0.83*	0.60	0.53	0.70	0.74	0.72
Geopotential Height (500 hPa)	0.06	0.06	−0.09	−0.49*	−0.25	0.33
U wind (500 hPa)	0.01	0.55	0.71	0.52	0.52	−0.68*
V wind (500 hPa)	−0.51*	0.26	0.01	−0.34	−0.45*	−0.56*

Figure 4. January to March (JFM) 2 m air temperature anomaly for composite drought years (units: °C).

Figure 5. January to March (JFM) mean sea level pressure anomaly for composite drought years (units: Pa).

Figure 6. October to December (OND) mean sea level pressure anomaly for composite drought years (units: °C).

Figure 7. January to March (JFM) geopotential height anomalies at 500 hPa (a) and 300 hPa (b) for composite drought years (units: gpm).

Figure 8. March to May (MAM) wind vector anomalies at 500 hPa (a) and 300 hPa (b) for composite drought years (units: m² s^-2).

Figure 9. Hot and dry extremes over Pakistan during the core monsoon season (JJA) and associated links with the ENSO during 1981-2017. (a) Three-month (June to August) precipitation anomalies, (b) the single Z-index anomalies, (c) Nino 3.4 SST anomalies during the same time period. Grey vertical bars denote the dry monsoon anomalies associated with the 6 most severe and extreme drought years.

Figure 10. Schematic diagram of drought severity assessment and drought prediction.

Data availability statement

The monthly reanalysis data sets that support the findings of this study are publically availabl at: https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era5

The station data was obtained from Pakista meterological department https://www.pmd.gov.pk/en/