Anomalous tsw (sea surface temperature) at the first day of each month in ERA5-nudged simulation

[l975421700]

Dear Community

When I run ERA5-nudged ECHAM6 simulations, I found that the daily output tsw shows anomalous large values on the first day of each month compared to the rest of the month. It does not occur in preindustrial simulation. Below are detailed configurations.

esm_tools version: 6.23.3
ECHAM6 version: 6.3.05p2-wiso
runscript: /albedo/work/user/qigao001/albedo_scratch/output/echam-6.3.05p2-wiso/pi/test7/scripts/nudged_echam6_1m.yaml
experiment location: /albedo/work/user/qigao001/albedo_scratch/output/echam-6.3.05p2-wiso/pi/test7
example anomalous tsw: ncview /albedo/work/user/qigao001/albedo_scratch/output/echam-6.3.05p2-wiso/pi/test7/unknown/test7_202201.01_echam.nc

Could you please share some thoughts on this?

Regards, Qinggang