Page History

The land sea mask used in the ECMWF IFS changed with the introduction of 41R1. Figures in the table below illustrates illustrate where there have been changes (please refer to titles on the imagesthe title on each image). Mostly the changes were for the better, with some notable improvements over Europe (mostly the land area is now bigger - row 9 below shows an example). However there were unfortunately were  some areas of degradation also, specifically in the Pacific, where some islands have unfortunately 'disappeared' due to errors in the new geographical dataset used by ECMWF - all the examples instances of this are included shown on the following table, in rows 2-7. Their geographical location is Locations of these are also marked on the global map on row 1. Following consultation it was decided to wait until the next cycle (41R2) before these errors in the Pacific are rectified. Row 8 illustrates that there have also been some significant changes in the land and sea points around Antarctica.

Row Label	Area	Map Link	Comments
1	Globe		Shows locations of all subsequent plots
2	Samoa and Niue	Image Modified	Samoa reduced from 11 land gridpoints to 1. Niue now sea point.
3	Tahiti and the Marquesas	Image Modified	Main Tahiti and Marquesas islands are now just sea points.
4	Chatham	Image Modified	Chatham island is now just sea points.
5	Micronesia	Image Modified	Micronesia island is now just a sea point.
6	Marion	Image Modified	Marion island is now just a sea point.
7	Noname	Image Modified	Nameless island near Antarctica is now just a sea point (lower left of plot)
8	Antarctic Peninsular		The distinction between permanent sea ice and land around Antarctica is blurred. Locally there are some large changes in 41R1 compared to 40R1 (not just in this area).
9	Baltic		This is solely an illustration of the fact that over Europe there are more land points in 41R1 than there used to be in 40R1 (more green dots), and not just in the Baltic. 41R1 is believed to be much more accurate in the European region.