Near
real-time monitoring of drought at a 5-km scale that will help policy makers in
water management at a district level is now possible, thanks to tools developed
and made available online by researchers at the Indian Institute of Technology
(IIT) Gandhinagar.
The
researchers offer precipitation and temperature datasets and drought indicators
available from 1980 to April 2017 covering the entire South Asian region. The
data will be updated weekly. Besides drought, the datasets can also be used for
monitoring heat and cold waves in South Asia.
“We don’t
know whether a particular region is in drought as we don’t have real-time
rainfall and temperature data at appropriate scale. IMD [Indian Meteorology
Department] provides daily rainfall data mainly during the monsoon season.
There’s no real-time information at high-resolution about drought after the
monsoon season,” says Prof. Vimal Mishra from the Civil Engineering department
at IIT Gandhinagar and one of the two researchers who developed the dataset.
Also, IMD’s
drought information is based only on rainfall data and does not incorporate the
role of air temperature. But higher temperature after the monsoon season can
cause drought-like situation due to increased evaporation and transpiration
losses.
At the district level
The team
wanted to provide information in near real-time on whether a region of interest
is under drought and what part of a district or sub-basin is under drought.
The
emphasis was to develop a dataset at a finer resolution (5 km) as the data
provided by IMD and other agencies is coarse (resolution of 25 km). The
researchers used CHIRPS global rainfall data which are available at 5 km
resolution and corrected the data for bias and errors. CHIRPS stands for
Climate Hazards Group InfraRed Precipitation with Station. “The corrected data
compares well with the IMD data once we aggregate our data to the IMD scale,”
says Prof. Mishra.
The
precipitation dataset at a finer resolution of 5 km over the entire South Asian
region was evaluated against a standard rainfall database (APHRODITE) that is
available for South Asia and satellite-based information. Earlier studies have
shown that the Aphrodite database matches the IMD rainfall data quite well. The
results were published in the journal Scientific Data.
“The
drought indices — standardised precipitation index and standardised
precipitation evapotranspiration index — were estimated using the
bias-corrected, high-resolution data and evaluated against satellite-based
drought products. The validation gives us the confidence that our dataset can
indicate the severity and extent of drought at a district and sub-basin level
in south Asia,” says Saran Aadhar from the Civil Engineering department at IIT
Gandhinagar and the first author.
The
researchers used the drought indices to assess severity and extent of drought
in 2015 for a four-month period from June to September. “The developed dataset
and drought indicators performed well over the South Asian region. Apart from
IMD, this is an additional effort to provide more real-time information on
drought that can be used for decision-making,” says Prof. Mishra.
Source:THE HINDU-5th October,2017
