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Yun Lin, Jiwen Fan, Jong-Hoon Jeong, Yuwei Zhang, Cameron R. Homeyer, and Jingyu Wang

1. Introduction Urbanization is an extreme case of land-use change ( Shepherd 2005 ), along with intensive anthropogenic aerosol emissions. Worldwide urban land and population have grown rapidly over the twentieth century. All regions are expected to urbanize further during the coming decades ( Alig et al. 2004 ). In the United States, urban land is projected to increase from 39.5 million ha in 1997 to 70.5 million ha in 2025 ( Alig et al. 2004 ). Urbanization has significant local impacts on

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Alan Shapiro, Evgeni Fedorovich, and Joshua G. Gebauer

LLJ), or along or north of the intersection of an LLJ with a cold front, are more or less clear, but the mechanisms that force ascent on a lateral flank of an LLJ are still not well understood. In this regard, we believe that the recent Pu and Dickinson (2014) explanation for such a mechanism is not wholly satisfactory. In a study of vertical motions in Great Plains LLJs using a North American Regional Reanalysis (NARR) June–July climatology, Pu and Dickinson (2014) suggest that after midnight

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Shushi Zhang, David B. Parsons, and Yuan Wang

lies above the southerly peak. Parsons et al. (2019) found that on average this westerly layer was favorable for deep convection with significant CAPE and lower convective inhibition (CIN). Nocturnal MCSs that are maintained by lifting of this potentially unstable air at and above the level of the NLLJ are typically considered to be “elevated.” We do note, however, that different definitions have been used for the term “elevated” and Corfidi et al. (2008) showed that even surface-based systems

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David B. Parsons, Kevin R. Haghi, Kelton T. Halbert, Blake Elmer, and Junhong Wang

region with a nocturnal convective maximum ( Fig. 1a ) so that the composited vertical profiles of CAPE, CIN, and horizontal winds allow insight into both bores and the nocturnal convective maximum. Given that nocturnal convection can be elevated and fed by CAPE above the stable boundary layer [see Geerts et al. (2017) and references within], the use of the vertical profile of CAPE and CIN provides greater insight into the relationship between convection and the environment than can be obtained

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