Monthly documents were created by the Antarctic Meteorological Research and Data Center to identify and track the time and position of Cloud Mass Meridional Transport events (CMMTs) around Antarctica and the Southern Ocean. These events were originally called Cloud Mass Transport events (CMTs) by Staude (2007) who first observed them in McIDAS-X by using a combination of infrared satellite imagery from geostationary and polar orbiting satellites (Kohrs et. al, 2013). These satellite images and animations can be found at https://doi.org/10.48567/y8as-0m56 (AMRDC, 2026).
The longevity of this project has seen the format of the monthly documents evolve over time. Unless specified otherwise, all the files are ASCII text.
01 November 1992 - 31 October 2012
-
Coordinates: The Western Hemisphere is negative (150° W = -150). The Eastern Hemisphere is positive (90° E = 90).
-
Regions: Marie Byrd Land, Ellsworth Land, Queen Maud Land, Enderby Land, Queen Mary Coast, Wilkes Land, Victoria Land, and Skirting Events.
-
Date and Time Format: MMM DD TZ, where M = month, D = day, T = hour of the day, and Z = Zulu time. The start and end dates/times are given, followed by the frames the CMMT can be found at.
-
Available Data: In each ASCII text file, the letters, “LS,” will appear near the top of the page followed by a series of numbers. These represent the available frames for a month. Until 08 Apr 2009, 00 UTC, 3-hourly data was used and 248 was the maximum number of frames available. After 08 Apr 2009, 00 UTC, hourly data is used and the frames are broken down into three 10-day periods (1-10, 11-20, 21-30), where each period contains up to 240 frames. For months with 31 days, an extra 24 frames are added after the three sections of 240 frames.
-
A 30-day month with no missing data after 2009 should look like this: LS 1-240, 1-240, 1-240.
-
A 30-day month with missing data after 2009 could look like this: LS 1-228 232-240, 1-240, 1-135 137-240.
-
A 31-day month with no missing data after 2009 should look like this: LS 1-240, 1-240, 1-240, 1-24.
-
CMMT Duration: Listed on the right-hand side of the page (i.e., 2d = 2 days).
01 November 2012 - 31 December 2022
-
Coordinates: Not listed. Should a CMMT move through two or more regions, then all of the regions it passes through are listed rather than the coordinates.
-
Regions: Marie Byrd Land, Ellsworth Land, Queen Maud Land, Enderby Land, Queen Mary Coast, Wilkes Land, Victoria Land, West Antarctic Skirting event, and East Antarctic Skirting event.
-
Date and Time Format: TTZ MMM DD, where TTZ = hour of the day in Zulu time, MMM = month (written out in abbreviated letters), and DD = day.
-
The start and end dates/times are given, but the frames are excluded. Mp4 animations were used in favor of McIDAS-X after 2012.
-
Example: 22Z Jan 1st - 18Z Jan 2nd
-
CMMT Duration: Listed on the right-hand side of the page (i.e., 2d = 2 days). Events less than 2 days will be written as <2d or <1d.
-
Available Data: Gaps of data bigger than 12 hours are listed near the top of the page in parentheses and bold text. Gaps less than 12 hours may exist in the data, but are not documented in the monthly text files.
- Example: (No footage 12Z Jan 8th to 23Z Jan 31st)
-
Non-CMMTs: Cloud masses that satisfy CMMT criteria for at least 12 hours and at most 47 hours. <1d events are 12-23 hours and <2d events are 24-47 hours. Non-CMMTs are not counted as CMMTs in any document or CSV file.
-
Events by Duration: At the bottom of the page, all of the non-CMMTs and CMMTs are organized by duration. Durations with zero CMMTs are not listed.
-
Commentary: Comments for events are listed below an event to explain why a decision was made. Events without comments are usually intuitive, or have no complications when viewing the event. Some vocabulary in the comments may not be intuitive to the reader. A pdf file titled CMMTJustifications Metadata will have definitions of the most common comments.
Citations:
Antarctic Meteorological Research and Data Center: Antarctic Satellite Composite Imagery. AMRDC Data Repository. Accessed 04-06-2026, https://doi.org/10.48567/y8as-0m56.
Kohrs, Richard A., Lazzara, Matthew A., Robaidek, Jerrold O., Santek, David A. and Knuth, Shelley L. Global satellite composites - 20 years of evolution. Atmospheric Research, Volume 135, 2014, p. 8-34, https://doi.org/10.1016/j.atmosres.2013.07.023.
Staude, J., 2007: Poleward Propagating Weather Systems in Antarctica. M.S. thesis, Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, 90 pp, https://www.aos.wisc.edu/uwaosjournal/Volume4/theses/Staude.pdf