I am using IMD gridded daily rainfall data (0.25 deg x 0.25 deg resolution) that has been made freely downloadable. Is the daily accumulated precipitation measured / calculated from 00UTC on that day upto 00 UTC the next day, or is it from 03 UTC (i.e, 08:30 hrs LST) that day to 03 UTC the next?
Or, rather, is it the accumulated precipitation measured / calculated from 00UTC the previous day upto 00 UTC on that day, or from 03 UTC (i.e, 08:30 hrs LST) the previous day to 03 UTC that day?
For eg, if I access tha rainfall data of the 30th day (,i.e, 30 Jan) of the year, as given in the file, will the data be :
1. Accumulated precipitation from 30 Jan 00UTC to 31 Jan 00UTC? or
2. Accumulated precipitation from 30 Jan 03UTC to 31 Jan 03UTC? or
3. Accumulated precipitation from 29 Jan 00UTC to 30 Jan 00UTC? or
4. Accumulated precipitation from 29 Jan 03UTC to 30 Jan 03UTC?
Which one of the four options are correct?
Kindly help me out.
Thankyou.
Dear Gayatri,
The readings in Indian observatories are made every day by 8:30 AM. Thus, total rainfall for the preceding 24 hours ending at 08.30 am of the recording date of the measurement is recorded as daily rainfall. It should be taken as 24-hour rainfall recorded on dd/mm/yyyy at 08:30 AM.
Now, the gridded data are interpolated using the IMD station data and thus would follow a similar pattern. 8:30 IST ~ 03UTC. So to answer your question, rainfall data of the 30 Jan of the year would be 29 Jan 03UTC to 30 Jan 03UTC.
This is my understanding. Kindly correct me if otherwise. Thanks!
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