  Based on synthetic flux spectra calculated from theoretical atmospheric
models, a calibration of temperature and metallicity for the dwarfs observed in
the Beijing-Arizona-Taiwan-Connecticut (BATC) multicolor photometric system is
presented in this paper. According to this calibration, stellar effective
temperatures can be obtained from some temperature-sensitive color indices. The
sample stars have colors and magnitudes in the ranges 0.1<d-i<0.9 and
14.0<i<20.5. The photometric metallicities for these sample stars can be
derived by fitting SEDs. We determine the average stellar metallicity as a
function of distance from the Galactic plane. The metallicity gradient is found
to be d[Fe/H]/dz=-0.37+-0.1dex/kpc for z<4 kpc and
d[Fe/H]/dz=-0.06+-0.09dex/kpc between 5 and 15 kpc. These results can be
explained in terms of different contributions in density distribution for
Galactic models `thin disk', `thick disk' and `halo' components. However, for
the gradient in z>5 kpc, it could not be interpreted according to the different
contributions from the three components because of the large uncertainty. So it
is possible that there is little or no gradient for z>5 kpc. The overall
distribution shows a metallicity gradient d[Fe/H]/dz=-0.17+-0.04dex/kpc for
z<15 kpc.
