Deep convective clouds and chemistry (DC3): Description of the field campaign and modeling of lightning NOx in the DC3 study areas
Mary C. Barth, NCAR, Boulder, CO; and C. Cantrell, S. A. Rutledge, W. Brune, C. Barthe, W. C. Skamarock, and M. Weisman
Convective transport is a major pathway of rapidly moving chemical
constituents from the boundary layer to the upper
troposphere (UT) and in some cases to the lower stratosphere (LS).
Yet the global-scale impact of convective transport on the UTLS
composition and chemistry has not been characterized. In addition,
only a few studies have attempted to examine the detailed dynamics
of deep convection and the concomitant redistribution, production,
or removal of reactive constituents. The proposed Deep Convective
Cloud and Chemistry (DC3) experiment will obtain measurements of
enough chemical species to characterize the effects of convection
on the transport and transformation of ozone and its precursors.
For example, HOx species, its precursors, and NOx species in both
inflow and outflow regions of deep convection will be measured along
with microphysical properties, storm kinematics, and lightning
discharges. These measurements are planned for over the Great Plains
of the United States, where we hope to contrast regions of remote
continental air to those more influenced by anthropogenic emissions.
The primary goals of DC3 are 1) to characterize the storm dynamics,
cloud physics, and lightning of the convective storms contrasting
environments from the U.S. High Plains to the Gulf Coast region;
2) to quantify the impact of continental, midlatitude convection on
the transport of chemical constituents to the upper troposphere in
the context of the dynamical, physical, and electrical characteristics
of the convection; 3) to determine the effects of convectively-perturbed
air masses on ozone and its related chemistry in the midlatitude upper
troposphere and lower stratosphere near the convective cores (in the
anvil region) and further downwind, 12-48 hours after the near convection
region is sampled, and 4) to contrast the influence of different
boundary-layer chemical inputs on the composition of convective outflow.
The strategy of reaching these goals as part of DC3 will be presented.
In preparation for DC3, the Weather Research and Forecasting model coupled
with Chemistry (WRF-Chem) is used to investigate the relative impact of
deep convection in the 3 DC3 locations: northeast Colorado, central Oklahoma,
and northern Alabama. These locations have characteristically different
types of storms, from high cloud base and strong shear storms in Colorado
to warm cloud bases in Oklahoma to low shear storms in Alabama.
The WRF-Chem simulations use a fine resolution (3 km or less), which is
nominally sufficient to represent convective systems and their transport
properties explicitly, without the need for convective parameterizations.
For this presentation, results of NOx produced from lightning will be emphasized.
Joint Session 6, Lightning and Atmospheric Chemistry—I
Wednesday, 14 January 2009, 8:30 AM-10:00 AM, Room 126A
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