Search Results
Abstract
Although tornadoes produced by quasi-linear convective systems (QLCSs) generally are weak and short-lived, they have high societal impact due to their proclivity to develop over short time scales, within the cool season, and during nighttime hours. Precisely why they are weak and short lived is not well understood, although recent work suggests that QLCS updraft width may act as a limitation to tornado intensity. Herein, idealized simulations of tornadic QLCSs are performed with variations in hodograph shape and length as well as initiation mechanism to determine the controls of tornado intensity. Generally, the addition of hodograph curvature in these experiments results in stronger, longer-lived tornadic like vortices (TLVs). A strong correlation between low-level mesocyclone width and TLV intensity is identified (R2 = 0.61), with a weaker correlation in the low-level updraft intensity (R2 = 0.41). The tilt and depth of the updraft are found to have little correlation to tornado intensity. Comparing QLCS and isolated supercell updrafts within these simulations, the QLCS updrafts are less persistent, with the standard deviations of low-level vertical velocity and updraft helicity to be approximately 48% and 117% greater, respectively. A forcing decomposition reveals that the QLCS cold pool plays a direct role in the development of the low-level updraft, providing the benefit of additional forcing for ascent while also having potentially deleterious effects on both the low-level updraft and near-surface rotation. The negative impact of the cold pool ultimately serves to limit the persistence of rotating updraft cores within the QLCS.
Abstract
Although tornadoes produced by quasi-linear convective systems (QLCSs) generally are weak and short-lived, they have high societal impact due to their proclivity to develop over short time scales, within the cool season, and during nighttime hours. Precisely why they are weak and short lived is not well understood, although recent work suggests that QLCS updraft width may act as a limitation to tornado intensity. Herein, idealized simulations of tornadic QLCSs are performed with variations in hodograph shape and length as well as initiation mechanism to determine the controls of tornado intensity. Generally, the addition of hodograph curvature in these experiments results in stronger, longer-lived tornadic like vortices (TLVs). A strong correlation between low-level mesocyclone width and TLV intensity is identified (R2 = 0.61), with a weaker correlation in the low-level updraft intensity (R2 = 0.41). The tilt and depth of the updraft are found to have little correlation to tornado intensity. Comparing QLCS and isolated supercell updrafts within these simulations, the QLCS updrafts are less persistent, with the standard deviations of low-level vertical velocity and updraft helicity to be approximately 48% and 117% greater, respectively. A forcing decomposition reveals that the QLCS cold pool plays a direct role in the development of the low-level updraft, providing the benefit of additional forcing for ascent while also having potentially deleterious effects on both the low-level updraft and near-surface rotation. The negative impact of the cold pool ultimately serves to limit the persistence of rotating updraft cores within the QLCS.
In an intriguing paper, Schultz et al. (2006 , hereafter S06 ) have reviewed observations of mammatus clouds in the scientific literature and offered some candidate mechanisms for the formation of mammatus. This reasonably comprehensive review is both interesting and stimulating. I concur with the authors that although mammatus cloud formations have little or no direct societal impact, they are a fascinating enigma, certainly worthy of careful scientific scrutiny. One candidate mechanism they
In an intriguing paper, Schultz et al. (2006 , hereafter S06 ) have reviewed observations of mammatus clouds in the scientific literature and offered some candidate mechanisms for the formation of mammatus. This reasonably comprehensive review is both interesting and stimulating. I concur with the authors that although mammatus cloud formations have little or no direct societal impact, they are a fascinating enigma, certainly worthy of careful scientific scrutiny. One candidate mechanism they
( Wandishin et al. 2008 , 2010 ; Cintineo and Stensrud 2013 ; Durran and Weyn 2016 ), and data assimilation analysis errors arising from lack of low-level observations (e.g., Dong et al. 2011 ; Potvin and Wicker 2013a ). Little has been done, however, to examine the sensitivity of storm forecasts to initial-condition (IC) resolution. Impacts of limited IC resolution are of critical concern to the envisioned Warn-on-Forecast (WoF) paradigm ( Stensrud et al. 2009 , 2013 ), in which kilometer
( Wandishin et al. 2008 , 2010 ; Cintineo and Stensrud 2013 ; Durran and Weyn 2016 ), and data assimilation analysis errors arising from lack of low-level observations (e.g., Dong et al. 2011 ; Potvin and Wicker 2013a ). Little has been done, however, to examine the sensitivity of storm forecasts to initial-condition (IC) resolution. Impacts of limited IC resolution are of critical concern to the envisioned Warn-on-Forecast (WoF) paradigm ( Stensrud et al. 2009 , 2013 ), in which kilometer
atmosphericcarbon dioxide burden). The major drawback wouldbe the hea'/,y demands on computer time to generateprescribed change and unperturbed control sampledclimate ensembles. However, in order to assesspossible anthropogenic impact on a GCM's inherentvariability of mean climatic states (the analog tothe natural interannual variability of the real climate system and a key climate measure for agricultural and other societal purposes) multiple realizations are an absolute necessity. Of course, theseobjective
atmosphericcarbon dioxide burden). The major drawback wouldbe the hea'/,y demands on computer time to generateprescribed change and unperturbed control sampledclimate ensembles. However, in order to assesspossible anthropogenic impact on a GCM's inherentvariability of mean climatic states (the analog tothe natural interannual variability of the real climate system and a key climate measure for agricultural and other societal purposes) multiple realizations are an absolute necessity. Of course, theseobjective
classification (experiment 3). 4. Application to a real data case In the previous section, we discussed results from a set of three observing system simulation experiments that used model-generated pseudo observations. To demonstrate the effectiveness of the proposed assimilation method for a real data case, we apply our method to the 8 May 2003 Oklahoma City, Oklahoma, tornadic supercell storm. This case has high societal impact. The storm spawned an F4 tornado that tracked through southern Oklahoma City
classification (experiment 3). 4. Application to a real data case In the previous section, we discussed results from a set of three observing system simulation experiments that used model-generated pseudo observations. To demonstrate the effectiveness of the proposed assimilation method for a real data case, we apply our method to the 8 May 2003 Oklahoma City, Oklahoma, tornadic supercell storm. This case has high societal impact. The storm spawned an F4 tornado that tracked through southern Oklahoma City
The Sensitivity of Hurricane Irene to Aerosols and Ocean Coupling: Simulations with WRF Spectral Bin MicrophysicsHurricane Research—Climate, Dynamics, and Societal Impacts , A. R. Lupo, Ed., Intech, 197–227 , doi: 10.5772/15907 . Khain , A. P. , M. Ovtchinnikov , M. Pinsky , A. Pokrovsky , and H. Krugliak , 2000 : Notes on the state-of-the-art numerical modeling of cloud microphysics . Atmos. Res. , 55 , 159 – 224 , doi: 10.1016/S0169-8095(00)00064-8 . Khain , A. P. , M. B. Pinsky , M. Shapiro , and A. Pokrovsky , 2001 : Collision rate of small graupel and water drops . J. Atmos. Sci
Hurricane Research—Climate, Dynamics, and Societal Impacts , A. R. Lupo, Ed., Intech, 197–227 , doi: 10.5772/15907 . Khain , A. P. , M. Ovtchinnikov , M. Pinsky , A. Pokrovsky , and H. Krugliak , 2000 : Notes on the state-of-the-art numerical modeling of cloud microphysics . Atmos. Res. , 55 , 159 – 224 , doi: 10.1016/S0169-8095(00)00064-8 . Khain , A. P. , M. B. Pinsky , M. Shapiro , and A. Pokrovsky , 2001 : Collision rate of small graupel and water drops . J. Atmos. Sci
convection in the tropics cannot be well represented in current RCMs. Previous studies have suggested that the RCM simulation of monsoon circulation is very sensitive to different cumulus parameterization (CP) schemes ( Zhang 1994 ; Leung et al. 1999 ; Lee and Suh 2000 ; Sun et al. 2014 ). In fact, various microphysics parameterization (MP) schemes also have a significant impact on convection through microphysical heating/cooling. While great efforts have been taken to investigate the impact of CP
convection in the tropics cannot be well represented in current RCMs. Previous studies have suggested that the RCM simulation of monsoon circulation is very sensitive to different cumulus parameterization (CP) schemes ( Zhang 1994 ; Leung et al. 1999 ; Lee and Suh 2000 ; Sun et al. 2014 ). In fact, various microphysics parameterization (MP) schemes also have a significant impact on convection through microphysical heating/cooling. While great efforts have been taken to investigate the impact of CP
influence on the adjacent oceanic forcing for the rainfall dipole than the remote impact from ENSO. On a quasi-decadal time scale, earlier work by Allan et al. (2003) showed a statistically significant dipole pattern in January–March (JFM) and a less significant dipole pattern in October–December (OND) from the correlation between the southern African rainfall and the quasi-decadal ENSO time series. On a longer time scale, such as decadal to multidecadal, more studies have been devoted to subregional
influence on the adjacent oceanic forcing for the rainfall dipole than the remote impact from ENSO. On a quasi-decadal time scale, earlier work by Allan et al. (2003) showed a statistically significant dipole pattern in January–March (JFM) and a less significant dipole pattern in October–December (OND) from the correlation between the southern African rainfall and the quasi-decadal ENSO time series. On a longer time scale, such as decadal to multidecadal, more studies have been devoted to subregional
strongly influences the radiative impact of convection and (ii) the in-cloud vertical velocity as it has a strong impact on supersaturation, aerosol–cloud interactions (activation), and microphysics. We will also discuss the spatial and temporal distributions of convective precipitation rates (which has societal and environmental impacts). Studying the sensitivity of these key convective cloud characteristics to model parameters and evaluating them against observations is a prerequisite for further use
strongly influences the radiative impact of convection and (ii) the in-cloud vertical velocity as it has a strong impact on supersaturation, aerosol–cloud interactions (activation), and microphysics. We will also discuss the spatial and temporal distributions of convective precipitation rates (which has societal and environmental impacts). Studying the sensitivity of these key convective cloud characteristics to model parameters and evaluating them against observations is a prerequisite for further use
rainfall rates typically exhibit an afternoon maximum over land, while they peak in the morning over ocean ( Nesbitt and Zipser 2003 ). Tropical cyclones (TCs) also exhibit diurnal behavior because of their characteristic, high-altitude outflow canopy and significant internal circulation. In this work, we examine cloud-resolving TC simulations to elucidate the impact of the diurnal cycle on quasi-steady TCs. A better understanding of how TCs react to diurnal insolation may lead to improved intensity
rainfall rates typically exhibit an afternoon maximum over land, while they peak in the morning over ocean ( Nesbitt and Zipser 2003 ). Tropical cyclones (TCs) also exhibit diurnal behavior because of their characteristic, high-altitude outflow canopy and significant internal circulation. In this work, we examine cloud-resolving TC simulations to elucidate the impact of the diurnal cycle on quasi-steady TCs. A better understanding of how TCs react to diurnal insolation may lead to improved intensity
