Last updated: 2023/11/24

This page describes the format of FALMA waveform data recorded after October, 2018.

File name

Data files are always named in the following way (for example AKKL1548422986.bz2):

• The first three characters indicate the site name
• The fourth character is always L for FALMA waveform data (meaning LF)
• The next 10 digits indicate the unix time of the start of the data (one file always contains the data of one full second at this unix time)
• The remaining four characters are always .bz2 (compressed in bz2 format)

Data format

FALMA waveform data are stored in a very simple format.

• One file only contains data points recorded in the one second stored in signed int16 (no other information), so the value of recorded data is always in the range of -2¹⁵ to 2¹⁵.
• Waveform data are recorded with a sampling rate of 1 MS/s, so each file contains 10⁶ data points in signed int16.
• All data are compressed in the bz2 format. If a file is decompressed, the size is always exactly 2*10⁶ bytes (any other size indicates the file is corrupted).

With Python(3), waveform data can be read with the following code (no need to decompress):

import bz2
import numpy as np

fileName = 'AKKL1548422986.bz2'
fid = bz2.BZ2File(fileName)
dataMat = np.frombuffer(fid.read(), np.int16) 
fid.close()
#The length of dataMat is always 1,000,000

import bz2
import numpy as np

fileName = 'AKKL1548422986.bz2'
fid = bz2.BZ2File(fileName)
dataMat = np.frombuffer(fid.read(), np.int16) 
fid.close()
#The length of dataMat is always 1,000,000

Sign convention

Waveforms are recorded in the atmospheric electricity sign convention, so a negative return stroke produces an initial positive electric field change.

Locations of FALMA sites

(Not all sites are currently working)