I agree that SPQ-9A was a fire control radar for guns. I also think that this is different from a surface radar. A surface radar has a very narrow radar beam going of the water surface to detect navigational hazards and other ships (and everything else on the surface, e.g. periscopes, boats etc.). Its main purpose is navigation and situation awareness on the surface. The fire control radar is for guiding guns and/or missiles.

You quoted a book from 1986. SPQ-9B was first tested in 1993-95 and operationally evaluated in 2002! It looks very different compared to the description in the book. It does not has larger radom, but no radom at all. It is a very different radar, it is a phased array radar.

Here is SPQ-9A:

[url=https://commons.wikimedia.org/wiki/Category:AN/SPQ-9#/media/File:SPQ-9_radome_on_USS_Nicholson_(DD-982).jpg/2]Wikimedia Commons

Radartutorial.eu

Here SPQ-9B:

[url=https://commons.wikimedia.org/wiki/File:AN_SPQ-9B_radar_on_board_mast_of_JS_Atago(DDG-177)_left_front_view_at_JMSDF_Maizuru_Naval_Base_April_13,_2019.jpg]Wikimedia Commons

SPQ-9B got the the additional function (not only capability!) to detect and track air targets. It is not longer a fire control radar only or even mainly for the guns, but its used to warn against incoming missiles and guide the defence against them. It is used also on aircraft carriers and is part of the air defence.