Three Dimensional Distribution of Atomic Hydrogen in the Milky Way
  A new model for three dimensional distribution of atomic hydrogen gas in the
Milky Way is derived using the 21cm LAB survey data. The global features of the
gas distribution such as spiral arms are reproduced. The Galactic plane warps
outside the solar orbit and the thickness of the gas disk flares outward the
Galaxy. It is found that the mass of atomic hydrogen gas within a radius of 20
kpc is 4.3*10^9 M_Sun.
