Why are these carrier aircraft landing with the canopy open?
Because it is the standard operating procedure, not only for this aircraft, but also for others. In the book U.S. Naval Air Superiority: Development of Shipborne Jet Fighters - 1943-1962, [Tommy H. Thomason notes](By Tommy H. Thomason):


  Leaving the canopy open for landings and takeoffs would still be standard for many years as it facilitated egress in the event of a water landing. 


Here's the Grumman F9F Panther, one of Navy's first jet fighters landing with its canopy open:



Grumman F9F-5 Panther, Bu. No. 126034, of VF-781, catches an arresting cable when landing aboard USS Oriskany (CVA-34), 15 November 1952. (U.S. Navy); image from thisdayinaviation.com

This followed through the time of Cutlass, as thanlont.blogspot.in notes:


  The ... F7U pilots all have their canopies open for landing. Although open canopies for carrier takeoffs and landings had been standard since canopies were introduced, this became pilot's choice on straight-deck carriers at some point following the addition of the barricade ... after an incident or two when the upper strap of the barricade went into the cockpit of a crashing jet. Note that the FJ-3s are taking off with open canopies.