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Abstract. Transport and scavenging of chemical constituents in deep convection is important to understanding the composition of the troposphere and therefore chemistryclimate and air quality issues. High resolution cloud chemistry models have been shown to represent convective processing of trace gases quite well. To improve the representation of sub-grid convective transport and wet deposition in large-scale models, general characteristics, such as species mass flux, from the high resolution cloud chemistry models can be used. However, it is important to understand how these models behave when simulating the same storm. The intercomparison described here examines transport of six species. CO and O 3 , which are primarily transported, show good agreement among models and compare well with observations. Models that included lightning production of NO x reasonably predict NO x mixing ratios in the anvil compared with observations, but the NO x variability is much larger than that seen for CO and O 3 . Predicted anvil mixing ratios of the soluble species, HNO 3 , H 2 O 2 , and CH 2 O, exhibit significant differences among models, attributed to different schemes in these models of cloud processing including the role of the Correspondence to: M. C. Barth (barthm@ucar.edu) ice phase, the impact of cloud-modified photolysis rates on the chemistry, and the representation of the species chemical reactivity. The lack of measurements of these species in the convective outflow region does not allow us to evaluate the model results with observations.

Abstract. The early, prelightning, electrification of a storm resulting from noninductive (NI) charging involving graupel, cloud ice/snow, and supercooled cloud water in a riming environment is studied using a comparative approach in a two-dimensional storm electrification model. The primary schemes examined are NI charge transfers based on the laboratory work of Takahashi [1978] and Saunders et al. [1991 ]. The NI mechanism, based on Takahashi's work, develops a positive dipole (positive charge above negative) and electric fields approaching 185 kV m-'as the cloud enters the dissipating stage. Charge transfers, based on the work of Saunders and colleagues, had to be reduced in magnitude to produce electrification that is consistent with the observations. In addition, the Saunders scheme produces an initially inverted dipole (negative charge above positive) which resolves to a positive dipole in the latter part of the simulation and produces electric fields approaching 250 kV in '•. Sensitivity tests show that the NI scheme, based on Takahashi's work, is sensitive to the number concentration of ice crystals, whereas the Saunders-based scheme is much less sensitive to ice crystal numbers. The Saunders parameterization has strong positive charging of graupel at low effective liquid water content and low temperature. This positive charging can result in an unusual cloud-top charge structure when used at full value but is benign when the charging is reduced in magnitude. The charge structure resulting from the Saunders scheme is quite sensitive to the calculation of the effective water content, which determines the level of charge reversal. Both of the NI schemes are capable of producing electrification that approaches thunderstorm levels.

In this investigation we compare the results of the Storm Electrification Model (SEM) simulation of the July 19 Cooperative Convective Precipitation Experiment (CCOPE) case study cloud against the actual observations with respect to the cloud's electrical characteristics, as deduced from the data of two aircraft. It is found that the SEM reproduces the basic charge and electric field structure of the cloud on a time scale similar to that observed. The comparability of the modeled and observed values of field strength and charge within the cloud is directly related to the proximity of the aircraft to the main active core of the cloud. The character of the electric field external to the cloud appears to be well modeled, at least at the time of observation. A feature which was not observed, but appears in the model, is a charge‐screening layer at the top of the anvil. In addition, the model predicts electric field strengths sufficient to initiate a lightning discharge at approximately the same time in cloud evolution as that when an intracloud discharge was recorded.

The parameterization of an intracloud lightning discharge has been implemented in our Storm Electrification Model. The initiation, propagation direction, and termination of the discharge are computed using the magnitude and direction of the electric field vector as the determining criteria. The charge redistribution due to the lightning is approximated assuming the channel to be an isolated conductor with zero net charge over its entire length. Various simulations involving differing amounts of charge transferred and distribution of charges have been done. Values of charge transfer, dipole moment change, and electrical energy dissipation computed in the model are consistent with observations. The effects of the lightning-produced ions on the hydrometeor charges and electric field components depend strongly on the amount of charge transferred. A comparison between the measured electric field change of an actual intracloud flash and the field change due to the simulated discharge shows favorable agreement. Limitations of the parameterization scheme are discussed.1.