With 48r1 climate fields, including orography, land-sea mask, lake cover, lake depth and glacier mask, have been updated. These fields are now based on more up-to-date and higher resolution information. As a result the features of a grid point could change e.g. from a lake point in 47r1 to a land point in 48r1. 

For any application it is essential that whenever 48r1 parameters are combined with these climate fields, they are taken from the same 48r1 cycle.

The impact of the climate fields upgrade will be mainly local.

Note that some climate fields have been added to the test Open Data and will become available in ECMWF Open Data as standard 

Mean orography differences

The mean orography in 48r1 ​is based on T15999 input (at 1.4 km) instead of T7999 (2.8 km) as in 47r3. Small differences of mean orography are mainly due to the higher resolution of input fields and the correction of an orographic shift. 


In 48r1 inland water surfaces affecting the surface temperature are described using the new GSWE global dataset from JRC. Lakes, reservoir, rivers and coastal areas cover details have been improved particularly in the northern latitudes (> 60N).


The lake cover (cl) update increases lake cover fraction in northern latitudes, due to thawing in former permafrost regions. For the lakes, there is no longer any deep penetration of ocean into land and preservations of lake water when aggregating to a coarser resolution. 


47r3

48r1

The lake depth (dl) is a static field with a mean depth value in each grid box. Depths deeper then 1282 m are coloured in peach (most right colour). Violet and blue colours correspond to 3-5-10m, green-yellow - 25m.


The main source for the new glacier cover is GLIMS (Global Land Ice Measurements from Space, shapefile, 2017) with regional corrections for Greenland, Iceland, Svalbard, Antarctica (+extra gap filling in the middle of the continent).

References

Choulga, M., Kourzeneva, E., Balsamo, G., Boussetta, S., and Wedi, N.: Upgraded global mapping information for earth system modelling: an application to surface water depth at the ECMWF, Hydrol. Earth Syst. Sci., 23, 4051–4076, https://doi.org/10.5194/hess-23-4051-2019, 2019.

Choulga et al. 2019. Example of land sea mask obtained by the global 30m resolution GSWE aggregated to 1km on Google Earth Engine
https://hess.copernicus.org/articles/23/4051/2019/