Wong, John, The University of Colorado, Boulder, and
Mary Barth, NCAR, and David Noone, The University of Colorado, Boulder
Upper tropospheric ozone
has been shown to be sensitive to lightning-generated NOx (LNOx), especially
during monsoon seasons when an upper-air anticyclone forms providing a region
in which ozone precursors are accumulated over an extended period of time. The
parameterization of LNOx emissions in chemistry transport models (CTMs) is
based on three parts: 1) prediction of lightning flash rate based on model
variables, 2) prediction of the intracloud to cloud-to-ground flash ratio based
on model variables to locate the LNOx emission altitudes, and 3) estimation of
the amount of NO produced per flash. In this study, we evaluate the ability of
the widely-used Price and Rind (1992) lightning flash rate parameterization,
which is based on cloud-top height, using the Weather Research and Forecasting
model coupled with Chemistry (WRF-Chem) by comparing model-predicted lightning
flashes with data from the National Lightning Detection Networks (NLDN) and
from the Earth Networks Total Lightning Networks (ENTLN) for the contiguous
United States. The WRF-Chem model reasonably predicts both integrated total and
CG flash counts at 36 km resolution when compared against observational data
for summer 2006 and 2011. However, the Price and Rind (1993) IC:CG ratio
parameterization, which is based on the depth of the cold cloud, does not give
IC:CG ratios similar to those determined from the ENTLN observations. Further,
when WRF-Chem was run at 12 km horizontal resolution, the Price and Rind (1994)
resolution dependency factor did not scale well to produce similar lightning
flash frequency. Based on these results, recommendations are made regarding any
further utilization of the Price and Rind parameterizations. WRF-Chem
sensitivity simulations are also being conducted to estimate the influence of
LNOx on ozone during the North American monsoon period. The model results are
evaluated with data sets from satellite-borne and balloon-borne instruments,
and their sensitivities to varying levels of NO per flash and other parameters
are quantified in this study.