Introduction
The Copernicus pan-Arctic Regional Reanalysis (CARRA2) is a very high resolution (2.5 km) reanalysis system covering the full Arctic. The Arctic is an essential area of the Globe having a significantly stronger warming than other parts of the Earth. The CARRA2 dataset is a successor of the CARRA1 data with a full pan-Arctic coverage and it will cover more than 40 years of reanalysis from September, 1985 to present (it will be completed until Q2 2026). From 2027 onwards monthly timely update service is also planned adding 1 month new data to the dataset (with 2-3 months delay with respect to real time). The new pan-Arctic regional reanalysis system adds value to the ERA5 global reanalysis with the use of more (local) observations, with the better description of surface characteristic (like sea ice or glaciers for instance) and with its higher horizontal resolution. The new CARRA2 system has similar quality than that of CARRA1, but wider spatial and temporal coverage. All the details of the CARRA2 system is described in its Copernicus pan-Arctic Regional Reanalysis (CARRA2): Full system documentation.
Known issues
Warm 2m temperature over forest regions
The CARRA2 reanalysis dataset can exhibit unusually warm 2m temperatures when compared to other models or independent datasets. These warm temperatures are associated with the high-vegetation patches in the model and thus appear in regions dominated by forests. Prominent examples are Siberia or the Sahtu region in Canada. This deficiency is related to the fact that although the CARRA2 system describes the surface characteristics (like forests in this case) better than CARRA1, but the diagnostic formula used to determine the 2m temperature is unable to interpret the new canopy processes properly when they are translated to actual 2m temperature values. A note explaining all the details will be published soon. Meanwhile, it is recommended to use the 2m temperature variable with care over forest areas.
