In the Continental USA, I'm told the Civil Air Patrol (CAP) is the lead agency for SAR air search. Their training material is on the CAP site: http://nesa.cap.gov and Ground to Air and Air to Ground signals are covered in the curriculum for several roles.

The Ground Crew curriculum is at:
http://nesa.cap.gov/gsar-curriculum/
In Task Guide: Ground & Urban Team Task Guide
See "Task O-0703 EMPLOY GROUND TO AIR SIGNALS" on pages 148-150 of "Ground & Urban Direction Finding Team Tasks 24 May 2004"[1][2]

The Mission Aircrew School Curriculum is at:
http://nesa.cap.gov/mas-curriculum-2
In Mission Scanner Task Guide - Dec 14
see "MS O-2021 INTREPRET EMERGENCY SIGNALS AND DEMONSTRATE AIR/GROUND TEAM COORDINATION"
{ at a quick glance, these seem to be a superset of the Ground Crew signals. Also, the "Mission Scanner" is the guy in the plane who is looking for the survivor. Looking at the pilot training - they are taught to signal to the ground, but not to interpret ground signals}

[1] http://nesa.cap.gov/gsar-curriculum/ also has
two other documents that seem pertinent:
Task Guide: GTL & GTM Reference Guide
(see Chapter 10, pp. 77-83)
Power Point: Air to Ground Coordination
[2] My personal fetish, signal mirrors, are covered in
Task O-702, "USE A SIGNAL MIRROR" of the Ground & Urban Team Task Guide, and in Chapter 10, p81 of the GTL & GTM Reference Guide, though there are some errors in the instructions. I wonder how to submit errata? Some US government manuals have an explicit procedure for that ...