B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 220
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem
Aircraft
Climbing out of BWI; at approximately 5000 ft; we got an erroneous 'Too Low Terrain' warning followed by a 'Pull Up' Warning in VMC daytime conditions; there was obviously no issue with terrain.  We also got a countdown as if we were landing as we were climbing past 10;000 ft.  The Captain's Radio Altimeter was periodically indicating RA on the ADI and at other times indicating zero and negative numbers.  We established communications with Dispatch and Maintenance; and indirect contact with the Chief Pilot. We were concerned because our flight; (although initially in VMC conditions at the time of the incident) was going to end up at [destination] at night. We didn't want an erroneous PULL UP Warning at night. Dispatch; Maintenance; and the Chief Pilot all agreed that it was a faulty Radio Altimeter and that we would continue.  We landed uneventfully and MEL'd the Captain's Radio Altimeter.Not really sure what the fix is. The real reason we are writing this ASAP is to let you know that this is an issue. We actually considered pulling the circuit breaker for the radio altimeter to prevent a go-around because we were flying at night. We were between a rock and a hard place because if the erroneous indication had happened at night on approach; we would have to follow the QRH procedures and initiate an immediate go-around. Now; what do we do; do we do another approach and hope the Radio Altimeter doesn't act up? It should be noted that the MEL procedures are to do on the ground what we considered to do in the air: Pull the circuit breaker. Not sure if this has ever happened before; but we probably need to put some procedures in place.
[Report narrative contained no additional information.]
B737-700 flight crew reported erroneous GPWS terrain warnings climbing out of BWI that were traced to a malfunctioning Captain's radio altimeter.