  Heterogeneous nucleation and subsequent growth of surface water occur on the
natural substrate when the water vapor concentration reached the point of
super-saturation. This study focuses on the parameterization of
super-saturation on the canopy-air interface by field observations monitoring
surface water formation (SWF) such as dew and frost in the evergreen shrub at
an urban cite during autumn and winter in 2015-2017. Here we show that both the
interfacial and vertical temperature differences ranged from 1 to 3 K and were
necessary but not sufficient for super-saturated condensation on the natural
surface. Excessive supplies of moisture must exist, continuously contribute to
the growth of the condensed water embryos, originate from both the local and
the external sources such as evapotranspiration and atmospheric advection
driven by the reduced air pressure, cause SWF not only on the ground soil but
also on the vegetation canopy at 1-2 m height. The super-saturation ratio is
mainly determined by the coefficient of thermophoresis deposition, which
approaches to 1. SWF on the natural surface is not only an indicator but also a
weak cleaner of air pollution. The downward thermophoresis deposition of fine
particle and droplets favors SWF and the scavenging of air pollutants. The
removal efficiency of the deposition flux during SWF event for [SO42-+NO3-] is
estimated by ~0.3 mmol (per [Ca2+] meq)/m2(per leaf area).
