Search Results

You are looking at 1 - 10 of 16 items for :

  • Planetary waves x
  • Plains Elevated Convection At Night (PECAN) x
  • All content x
Clear All
Brian J. Carroll, Belay B. Demoz, David D. Turner, and Ruben Delgado

1. Introduction The Great Plains low-level jet (LLJ) is a primarily nocturnal phenomenon of strong southwesterly winds within the planetary boundary layer (PBL) spanning hundreds of kilometers in width and length, and is most frequent and impactful during the warm-season. LLJs provide major contributions to nocturnal convection in the region, such as mesoscale convective systems (MCSs), via convergence of the wind field and advection of moisture and temperature ( Byerle and Paegle 2003 ; Trier

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

-scale environment favorable for storm formation and maintenance. Data from the North American Regional Reanalysis (NARR) reanalysis at 1800 UTC 1 July 2015 are presented to highlight characteristics of the synoptic-scale condition ( Fig. 2 ). The storm formed east of the short-wave trough located in Nebraska ( Fig. 2a ). The 500 hPa winds exhibit a strong jet stream and upper-level disturbance over Kansas. A surface stationary front stretched from Pennsylvania to a broad region of low pressure in Kansas ( Fig

Restricted access
Shushi Zhang, David B. Parsons, and Yuan Wang

and Roberts 2006 ; Koch et al. 2008a , b ; Tanamachi et al. 2008 ; Martin and Johnson 2008 ; Hartung et al. 2010 ; Marsham et al. 2011 ; Blake et al. 2017 ). These results are expected as Haghi et al. (2017) revealed that the interaction between the convectively generated cold pools and the SBL over this region typically resides in a partially blocked flow regime where bores will be generated ( Rottman and Simpson 1989 ). These bores will be long lived as the wave energy is typically

Free access
Kevin R. Haghi, Bart Geerts, Hristo G. Chipilski, Aaron Johnson, Samuel Degelia, David Imy, David B. Parsons, Rebecca D. Adams-Selin, David D. Turner, and Xuguang Wang

( Johnson and Wang 2019 ). Physical parameterization schemes, especially microphysics (MP) and planetary boundary layer (PBL) schemes, are utilized in models to represent subgrid-scale interactions. In regards to an atmospheric bore, the wave speed, wavelengths, and amplitude will be compromised by the inability of a scheme to properly resolve the subgrid-scale interactions. For example, most of the PBL schemes are designed to reproduce ambient stratification with no regard to the turbulence occurring

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

finding was supported by observational analysis utilizing surface meteorological observations and radar “fine lines” that revealed that most convective outflows generated bores. Our investigation utilizes data also taken from IHOP_2002 to explore the vertical structure of bores and their potential to initiate and maintain deep convection. A key finding of this study that was not expected from hydraulic and linear wave theory of bores was that additional wave disturbances extend over the lower

Full access
Coltin Grasmick, Bart Geerts, David D. Turner, Zhien Wang, and T. M. Weckwerth

well-mixed, deep planetary boundary layer (PBL)—to elevated nocturnal convection, which typically organizes at larger scales as the nocturnal stable boundary layer (SBL) deepens, and a low-level jet (LLJ) develops above the SBL ( Corfidi et al. 2008 ; Carbone and Tuttle 2008 ; Reif and Bluestein 2017 ). Convective cells develop when a parcel of air is lofted to its level of free convection (LFC), becoming buoyant with respect to its surrounding environment. Convective cells often initiate in the

Full access
Aaron Johnson, Xuguang Wang, Kevin R. Haghi, and David B. Parsons

conducive for gravity wave ducting ( Crook 1986 ; Koch and Clark 1999 ). The second main ingredient needed for successful NWP forecasts of bores is an accurate forecast of the parent convection that generates the density current, which in turn triggers the bore. This ingredient is satisfied in this study by initializing the simulations from analyses that include the parent convection. This is done using data assimilation that incorporates radar, surface, and upper-air observations. However, it will

Full access
Aaron Johnson and Xuguang Wang

1. Introduction Atmospheric bores are commonly observed in the nocturnal convective environment in the Great Plains ( Haghi et al. 2017 ). This is because the stable boundary layer and low-level jet often provide a suitable wave duct, while convectively generated cold pools frequently provide an obstacle to this stable and ducted low-level flow ( Rottman and Simpson 1989 ; Johnson et al. 2018 ). Several studies have demonstrated the importance of bores in both the initiation and maintenance of

Full access
Alan Shapiro, Evgeni Fedorovich, and Joshua G. Gebauer

deep-tropospheric gravity waves (e.g., Uccelini 1975 ; Koch et al. 1988 ; Fovell et al. 2006 ; Marsham and Parker 2006 ); cold fronts, density currents, and drylines (e.g., Charba 1974 ; Wilson and Schreiber 1986 ; Mahoney 1988 ; Weckwerth and Wakimoto 1992 ; Hane et al. 1993 ; Ziegler and Rasmussen 1998 ; Weiss and Bluestein 2002 ; Geerts et al. 2006 ; Weckwerth et al. 2008 ); inland or “vegetation” breezes (e.g., Sun and Ogura 1979 ; Mahfouf et al. 1987 ; Segal and Arritt 1992

Full access
Tammy M. Weckwerth, John Hanesiak, James W. Wilson, Stanley B. Trier, Samuel K. Degelia, William A. Gallus Jr., Rita D. Roberts, and Xuguang Wang

array of PECAN Integrated Sounding Arrays (PISAs) to sample the vertical profiles of lower-tropospheric winds, temperature, and water vapor. These PISAs and the scanning radars and lidars of PECAN were used to sample the specific features (e.g., LLJ, bores, and gravity waves) and atmospheric regions (e.g., SBL and lower troposphere) relevant to better understanding of NCI. This manuscript brings together past NCI work and PECAN data to document frequencies of different NCI types, as categorized by

Full access