Level 3 products are produced for several different compositing periods. In general, longer time periods fill in more of the naturally occurring data gaps (caused by, for example, clouds, sun glint, inter-orbit gaps, ice, low light, etc.) at the expense of short-lived features, which tend to get smoothed out in longer-period composites.
View compositing time periods below. Some products are only available as a subset of the total list of compositing periods which includes the following:
Daily
One data day's worth of measurements.
Rolling 3-Day (Near Real-Time)
Three consecutive days' worth of data; there are no predetermined start and stop dates, and there are generally three 3-day composites containing any given day (e.g. Dec. 31, 2005 - Jan. 2, 2006, Jan. 1, 2006 - Jan. 3, 2006, and Jan. 2, 2006 - Jan. 4, 2006 all contain January 2, 2006).
8-Day (Weekly)
Eight consecutive days' worth of data with predetermined start and stop days; the first 8-day period of each year always begins with January 1, the second with January 9, the third with January 17, etc. The final "8-day" composite of each year comprises only five days in non-leap years (Dec. 27 - 31) or six days in leap years (Dec. 26-31).
Monthly
One calendar month's worth of data; this will be 28, 29, 30, or 31 days' worth of data depending on the month.
Rolling 32-Day
32 days' worth of data with each subsequent composite shifted 8 days further along the calendar; the start dates of the composites are the same as those of the corresponding 8-day composites; those that start in December wrap into the subsequent year. These composites are intended to be used as frames in animations; the fact that neighboring frames share 24 of the 32 days that they are composed of makes for smoother animations.
Seasonal
These are nominal boreal seasons having the following start and end dates.
Winter
- Dec. 21 through March 20 of the following year.
Spring
- March 21 through June 20 of the same year.
Summer
- June 21 through Sept. 20 of the same year.
Autumn
- Sept. 21 through Dec. 20 of the same year.
Annual
One calendar year's worth of data.
Weekly Climatology
Each one of these composites comprises data from a single 8-day period during all of the years of the mission to date. There are no more than 46 of these composites since there are 45 full 8-day composites every year plus 1 truncated (because neither 365 nor 366 are evenly divisible by 8) 8-day period at the end of every December. So, for example, at the time that I am writing this, the weekly Sea-viewing Wide Field-of-view Sensor (SeaWiFS) climatology for the beginning of January contains data from January 1 through January 8 for years 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, and 2008.
Monthly Climatology
A composite of all of the data collected during a single calendar month across all of the years of the selected mission to date.
Seasonal Climatology
A composite of all of the data collected during a single season (as defined above) across all of the years of the selected mission to date.
Entire Mission
An entire mission's worth of data in a single composite.