  Photoevaporation is an important dispersal mechanism for protoplanetary
disks. We conduct hydrodynamic simulations coupled with ray-tracing radiative
transfer and consistent thermochemistry to study photoevaporative winds driven
by ultraviolet and X-ray radiation from the host star. Most models have a
three-layer structure: a cold midplane, warm intermediate layer, and hot wind,
the last having typical speeds $\sim 30~\mathrm{km\ s}^{-1}$ and mass-loss
rates $\sim 10^{-9}~M_\odot~\mathrm{yr}^{-1}$ when driven primarily by ionizing
UV radiation. Observable molecules including CO, OH and H2O re-form in the
intermediate layer and survive at relatively high wind temperatures due to
reactions being out of equilibrium. Mass-loss rates are sensitive to the
intensity of radiation in energy bands that interact directly with hydrogen.
Comparison with previous works shows that mass loss rates are also sensitive to
the treatment of both the hydrodynamics and the thermochemistry. Divergent
results concerning the efficiency of X-ray photoevaporation are traced in part
to differing assumptions about dust and other coolants.
