Evaluating a lightning parameterization based on cloud-top height for mesoscale numerical model simulations

Abstract

Abstract. The Price and Rind lightning parameterization based on cloud-top height is a commonly used method for predicting flash rate in global chemistry models. As mesoscale simulations begin to implement flash rate predictions at resolutions that partially resolve convection, it is necessary to validate and understand the behavior of this method within such a regime. In this study, we tested the flash rate parameterization, intra-cloud/cloud-to-ground (IC : CG) partitioning parameterization, and the associated resolution dependency "calibration factor" by Price and Rind using the Weather Research and Forecasting (WRF) model running at 36 km, 12 km, and 4 km grid spacings within the continental United States. Our results show that while the integrated flash count is consistent with observations when model biases in convection are taken into account, an erroneous frequency distribution is simulated. When the spectral characteristics of lightning flash rate are a concern, we recommend the use of prescribed IC : CG values. In addition, using cloud-top from convective parameterization, the "calibration factor" is also shown to be insufficient in reconciling the resolution dependency at the tested grid spacing used in this study. We recommend scaling by areal ratio relative to a base-case grid spacing determined by convective core density.

Improvements to the WRF-Chem 3.5.1 model for quasi-hemispheric simulations of aerosols and ozone in the Arctic

“…These effects are evaluated by disabling in KF-CuP the effect of cumuli on tracer transport, aerosol activation, aqueous chemistry, and wet removal (NO_KFCUP_CHEM simulation). The effect of lightning NO x emissions or of the coupling between cumuli and radiation are not evaluated separately here, since they were already studied with other cumulus schemes in Wong et al (2013) and Alapaty et al (2012).…”

“…Biogenic emissions from vegetation are calculated online by the MEGAN model (Model of Emissions of Gases and Aerosols from Nature; Guenther et al, 2006). Other emissions calculated online by the WRF-Chem model include sea salt, mineral dust (both from the GOCART model; Chin et al, 2002), and lightning NO x emissions (Wong et al, 2013).…”

“…In addition, KF-CuP is coupled here to the RRTMG radiation scheme, by passing the KF-CuP cloud fraction, cloud water, cloud ice, and cloud droplet numbers to RRTMG, following the approach of Alapaty et al (2012). The lightning NO x emissions scheme of Wong et al (2013), previously coupled in WRF-Chem to other cumulus schemes, is also coupled here with KF-CuP, by linking KF-CuP cloud top heights, cloud fractions, and deep or shallow convection flags to the emission scheme. In this study, we only evaluate the effect of KF-CuP on aerosols and trace gases.…”

Simulating lightning into the RAMS model: implementation and preliminary results

“…The second group contains simple schemes that correlate the hydrometeors or other parameters computed by cloud-resolving models (nowadays with horizontal resolution ≤ 3 km) with the number of observed flashes, giving the flash rate (Price and Rind, 1992;McCaul et al, 2009;Yoshida et al, 2009;Yair et al, 2010;Wong et al, 2013). Wong et al (2013), revised the Price and Rind parametrizations by applying the methodology in cloud-resolving models.…”

“…Wong et al (2013), revised the Price and Rind parametrizations by applying the methodology in cloud-resolving models. They showed the need for a validation and tuning of the parametrizations when applying the method to cloudresolving models.…”