  Local mixing-length theory is incapable of describing nonlocal phenomena in
stellar convection, such as overshooting. Therefore standard solar models
constructed with the local mixing-length theory deviate significantly from the
Sun at the boundaries of the convection zone, where convection becomes less
efficient and nonlocal effects are important. The differences between observed
and computed frequencies come mainly from the near-surface region, while the
localized sound-speed difference is just below the convective envelope. In this
paper we compute a solar envelope model using Xiong's nonlocal convection
theory, and carry out helioseismic analysis. The nonlocal model has a smooth
transition at the base of the convection zone, as revealed by helioseismology.
It reproduces solar frequencies more accurately, and reduces the localized
sound-speed difference between the Sun and standard solar models.
