What is proper format for topographic displacement texture?

The topographic data samples are difference between planetary radius and geoid radius (gravity equipotential level which is “sea level”)
Obviously, the height can be higher and lower then zero.

Which texture format can store negative grayscale values so that displacement modifier can handle it?
In my case, the source is 16-bit signed integers (value range is between -32768 and +32767)

P.S.
I don’t care about utilities to produce the texture, i can create my own to produce any appropriate format.

SOLUTION
Blender 2.6 can only handle 8-bit or 16bit unsigned int displacement maps (PNG or TIFF)
Texture should be loaded with “non-color” colorspace to avoid conversion.
Signed displacement data should be converted to unsigned with 0-level at 32767 and modifier midpoint set to 0.5