I think it was been solved. Using gmt 6.2.0_50eafd2_2021.02.10 (Ubuntu 20.04.2 LTS) and the test data, running:
gmt grdimage -R0/360/1980-01-01/1984-01-01 -JX10cd/-10ct test.nc -Bxa20f10g10 -Bpyf1og1o -Bsya1yf1yg1y -BWSen --FONT_ANNOT_PRIMARY=6p --FONT_ANNOT_SECONDARY=10p -png case1
results:
As I didn’t have tmp.txt, I couldn’t test this command.


