WavyTropics - Droughts

Statistics from BNPB (2019) indicate that between 2010-2018 around 87% of all natural disasters in Indonesia were related to hydrometeorology. The region is primarily associated with high rainfall accumulation. However, rainfall intensity regularly fluctuates and seasonal droughts do occur (Bonal et al. 2016). In the Maritime Continent, droughts can be attributed to a narrower Intertropical Convergence Zone (ITCZ) during some periods (Xavier et al. 2020). There is also a strong connection between droughts and Indonesian fires with type of El Niño and phase of the Indian Ocean Dipole (Pan et al. 2018). According to Meteorology, Climatology, and Geophysical Agency (BMKG), about 92% of Indonesia experienced drought in 2019 due to the El Niño cycle that began at the end of 2018 (Indonesian Red Cross, 2019).

BNPB, 2019: Indonesian National Agency for Disaster Countermeasure (Badan Nasional Penanggulangan Bencana (BNPB)). http:/bnpb.cloud/dibi/tabel1b (Accessed March 15, 2019).
Bonal, D., B. Burban, C. Stahl, F. Wagner, and B. Hérault, 2016: The response of tropical rainforests to drought—lessons from recent research and future prospects. Ann. For. Sci., https://doi.org/10.1007/s13595-015-0522-5.
Xavier, P., and Coauthors, 2020: Seasonal Dependence of Cold Surges and their Interaction with the Madden–Julian Oscillation over Southeast Asia. J. Clim., https://doi.org/10.1175/jcli-d-19-0048.1.
Pan, X., M. Chin, C. M. Ichoku, and R. D. Field, 2018: Connecting Indonesian Fires and Drought With the Type of El Niño and Phase of the Indian Ocean Dipole During 1979–2016. J. Geophys. Res. Atmos., https://doi.org/10.1029/2018JD028402.

Meteorological drought is a condition in which rainfall has decreased compared to the average. Hydrological drought occurs when low water supply becomes evident.

Different definitions which were applied to the rainfall data are described below.

Drought_1 (BMKG's definition)

Currently, in drought monitoring, the Agency for Meteorology, Climatology, and Geophysics of the Republic of Indonesia (BMKG) uses an indicator called “No Rain Day” (HTH). HTH refers to the consecutive days without rainfall, counted backwards from the monitoring date.

Classification of Days:

1-5: Very short
6-10: Short
11-20: Moderate
21-30: Long
31-60: Very long
60: Extreme drought

Each day is classified into one of these categories, and the respective number (1 to 6) is assigned. However, this definition has limitations when dealing with NaN values (missing data), as even a single day of missing data halts the count, making continuous datasets essential.

This limitation does not apply to the Drought_2 and Drought_3 definitions, where a 10-day moving average is calculated, and NaN values are ignored in the process.

Drought_2

First, a 10-day moving average of daily accumulated precipitation ("daily_aw") is calculated. This technique is helpful to detect longer droughts. Then, "drought days" are defined as days ("daily_aw") with accumulated precipitation being less than the 10th percentile of daily precipitation. For calculating percentiles, only days with precipitation > 1 mm/day are considered. The final output is daily accumulated precipitation (not a 10-day moving average).

Drought_3

First, a 10-day moving average of daily accumulated precipitation ("daily_aw") is calculated. This technique is helpful to detect longer droughts. Then, "drought days" are defined as days ("daily_aw") with accumulated precipitation being less than the 5th percentile of daily precipitation. For calculating percentiles, only days with precipitation > 1 mm/day are considered. The final output is daily accumulated precipitation (not a 10-day moving average).

NOTES

Filenames

Each filename is composed of WMO number, definition used, and info if these are values or a time series vector related to values.

e.g. "WMO_96529_drought_1_values.txt"

Missing data

If you encounter the value 8888, it indicates "Unmeasured Data," while NaN and 9999 signify "No Data."
In the raw data, the time series vector remains continuous, even when data is missing.

Data Availability

Whenever possible, the timespan was set to cover all available days between 1 January 2000 and 31 December 2020.

Units

The data is classified as a number between 1 to 6 for Drought_1 or measured in mm/day for Drought_2 and Drought_3.

Data Availability

Units

TO ACCESS THE DATA, CLICK BELOW