  We solve the $S=1/2$ Kondo lattice model within the dynamical mean field
theory. Detailed predictions are made for the dependence of the lattice Kondo
resonance and the conduction electron spectral density on temperature and band
filling $n_{c}$. Two low-energy scales are identified in the spectra: a
renormalized hybridization pseudogap scale $T^{*}$, which correlates with the
single-ion Kondo scale, and a lattice Kondo scale $T_{0} < T^{*}$, which acts
as the Fermi-liquid coherence scale. The lattice Kondo resonance is split into
a main branch, which is pinned at the Fermi level, and whose width is set by
$T_{0}$, and an upper branch at $\omega\approx T^{*}$. The weight of the upper
branch decreases rapidly away from $n_{c}=1$ and vanishes for $n_{c}\lesssim
0.7$. In contrast, the pseudogap in the conduction electron spectral density
persists for all $n_{c}$. On increasing temperature, the lattice Kondo
resonance at the Fermi level vanishes on a temperature scale of order $10
T_{0}$, as in impurity model calculations. In contrast to impurity model
spectra, however, the position of the lattice Kondo resonance depends strongly
on temperature, particularly close to the Kondo insulating state. The results
are used to make predictions on the temperature dependence of the low-energy
photoemission and inverse photoemission spectra of metallic heavy fermions and
doped Kondo insulators. We compare our results with available high-resolution
measurements on YbInCu$_4$ and YbAgCu$_4$. The loss in intensity with
increasing temperature, and the asymmetric lineshape of the low-energy spectra
are well accounted for by our model. More detailed agreement with experiment
would require including the $f$-orbital degeneracy and crystal-field excited
states.
