The title says it all, pretty much.
Another delayed insight follows:
If it is indeed true that Jesus is Jehovah
then it seems to follow that the apparent differences between the behaviour of Jehovah and Jesus, as depicted on the Old and New Testaments - these differences are perhaps a consequence of the incarnation; are perhaps a consequence of the effect of Jesus becoming Man, inhabiting a mortal body.
Much (not all) of the differences between Old and New Testaments would therefore seem to be a consequence of this difference in God the Son, the story of whose relationship with his chosen people these books record.
To save us, to atone for our sins, God the Son needed to become mortal Man - and this, presumably, had an effect on Him, as well as its effect on us - one effect perhaps being seen in the differences between the 'personality' of the Old and New Testament God.