Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport

A nonmesocyclone tornado traversed the Hong Kong International Airport on September 6, 2004 directly impacting a surface weather station. This allowed for 1-second 10-meter above ground level (AGL) wind observations through the core of the tornado. Integration of these 10-meter AGL wind data with Ground-Based Velocity Track (GBVTD) wind retrievals derived from LIDAR data provided a time history of the three-dimensional wind field of the tornado. These data indicate a progressive decrease in radial inflow with time and little to no radial inflow near the time the tornado crosses the surface weather station. Anemometer observations suggest that the tangential winds approximate a modified-Rankine vortex outside the radius of maximum winds, suggesting that frictionally induced radial inflow was confined below 10 m AGL. The radial-height distribution of angular momentum depicts an increase in low-level angular momentum just prior to the tornado reaching its maximum intensity

Aerial Damage Survey of the 2013 El Reno Tornado Combined with Mobile Radar Data

A detailed damage survey of the El Reno, Oklahoma, tornado of 31 May 2013 combined with rapid-scanning data recorded from two mobile radars is presented. One of the radars was equipped with polarimetric capability. The relationship between several suction vortices visually identified in pictures with the high-resolution Doppler velocity data and swath marks in fields is discussed. The suction vortices were associated with small shear features in Doppler velocity and a partial ringlike feature of high spectral width. For the first time, a suction vortex that created a swath mark in a field was visually identified in photographs and high-definition video while the rotational couplet was tracked by radar. A dual-Doppler wind synthesis of the tornadic circulation at low levels near the location of several storm chaser fatalities resolved ground-relative wind speeds in excess of 90 m s−1, greater than the minimum speed for EF5 damage. The vertical vorticity analysis revealed a rapid transition from a single tornadic vortex centered on the weak-echo hole (WEH) to suction vortices surrounding the WEH and collocated with the ring of enhanced radar reflectivities. Several bands/zones of enhanced convergence were resolved in the wind syntheses. One of the bands was associated with an internal or secondary rear-flank gust front. An inner band of convergence appeared to be a result of the positive bias in tornado-relative radial velocity owing to centrifuging of large lofted debris swirling within the tornado. An outer band of convergence formed at the northern edge of a region of strong inflow that was lofting small debris and dust into the storm

Observational and Modeling Analysis of Land–Atmopshere Coupling over Adjacent Irrigated and Rainfed Cropland during the GRAINEX Field Campaign

The Great Plains Irrigation Experiment (GRAINEX) was conducted in the spring and summer of 2018 to investigate Land-Atmosphere (L-A) coupling just prior to and through the growing season across adjacent, but distinctly unique, soil moisture regimes (contrasting irrigated and rainfed fields). GRAINEX was uniquely designed for the development and analysis of an extensive observational dataset for comprehensive process studies of L-A coupling, by focusing on irrigated and rainfed croplands in a ~100 x 100 km domain in southeastern Nebraska. Observation platforms included multiple NCAR EOL Integrated Surface Flux Systems and Integrated Sounding Systems, NCAR CSWR Doppler Radar on Wheels, 1200 radiosonde balloon launches from 5 sites, the NASA GREX airborne L-Band radiometer, and 75 University of Alabama-Huntsville Environmental Monitoring Economic Monitoring Sensor Hubs (EMESH mesonet stations). An integrated observational and modeling approach to advance knowledge of L-A coupling processes and precipitation impacts in regions of heterogeneous soil moisture will be presented. Specifically, through observation of land surface states, surface fluxes, near surface meteorology, and properties of the atmospheric column, an examination of the diurnal planetary boundary layer evolving characteristics will be presented. Results from a hierarchy of modeling platforms (e.g. single column, large-eddy, and mesoscale simulations) will also be presented to complement the observational findings. The modeling effort will generate high spatiotemporal resolution datasets to: 1) generate a multi-physics ensemble to test the robustness and potentially advance physical parameterizations in high resolution weather and climate models, 2) comparison of prescribed forcing from observations and those from offline land surface model simulations and high resolution operational analyses, 3) determine the ability of model simulations to reproduce observed boundary layer evolution, with particular attention to the processes that compose the L-A coupling chain and metrics (e.g. mixing ratio diagrams), and 4) in combination with observations, isolate the impacts of soil moisture heterogeneity on planetary boundary layer characteristics, cloud development, precipitation, mesoscale circulation patters and boundary layer development. Initial results from the observational and modeling analysis will be presented

The 2015 Plains Elevated Convection at Night Field Project

The central Great Plains region in North America has a nocturnal maximum in warm-season precipitation. Much of this precipitation comes from organized mesoscale convective systems (MCSs). This nocturnal maximum is counterintuitive in the sense that convective activity over the Great Plains is out of phase with the local generation of CAPE by solar heating of the surface. The lower troposphere in this nocturnal environment is typically characterized by a low-level jet (LLJ) just above a stable boundary layer (SBL), and convective available potential energy (CAPE) values that peak above the SBL, resulting in convection that may be elevated, with source air decoupled from the surface. Nocturnal MCS-induced cold pools often trigger undular bores and solitary waves within the SBL. A full understanding of the nocturnal precipitation maximum remains elusive, although it appears that bore-induced lifting and the LLJ may be instrumental to convection initiation and the maintenance of MCSs at night. To gain insight into nocturnal MCSs, their essential ingredients, and paths toward improving the relatively poor predictive skill of nocturnal convection in weather and climate models, a large, multiagency field campaign called Plains Elevated Convection At Night (PECAN) was conducted in 2015. PECAN employed three research aircraft, an unprecedented coordinated array of nine mobile scanning radars, a fixed S-band radar, a unique mesoscale network of lower-tropospheric profiling systems called the PECAN Integrated Sounding Array (PISA), and numerous mobile-mesonet surface weather stations. The rich PECAN dataset is expected to improve our understanding and prediction of continental nocturnal warm-season precipitation. This article provides a summary of the PECAN field experiment and preliminary findings

Building the Games Students Want to Play: BiblioBouts Project Interim Report #3

The University of Michigan's School of Information and its partner, the Center for History and New Media at George Mason University, are undertaking the 3-year BiblioBouts Project (October 1, 2008 to September 30, 2011) to support the design, development, testing, and evaluation of the web-based BiblioBouts game to teach incoming undergraduate students information literacy skills and concepts. This third interim report describes the BiblioBouts Project team’s 6-month progress achieving the project's 4 objectives: designing, developing, deploying, and evaluating the BiblioBouts game and recommending best practices for future information literacy games. This latest 6-month period was marked by extensive progress in the deployment and evaluation of the alpha version of BiblioBouts. Major tasks that will occupy the team for the next 6 months are applying evaluation findings to game redesign and enhancement. For general information about game design, pedagogical goals, scoring, game play, project participants, and playing BiblioBouts in your course, consult the BiblioBouts Project web site.Institute of Museum and Library Serviceshttp://deepblue.lib.umich.edu/bitstream/2027.42/69157/1/bbInterimReportToIMLS03.pd

A comparison of radar observations to real data simulations of axisymmetric tornadoes

The interaction between a tornado and its immediate environment is critical in determining tornado vortex dynamics. This research was the first to integrate tornado-scale observations into a numerical model of a tornado vortex. As such, this allowed for the direct comparison between observed and modeled tornado vortex structure. To enable this comparison, two methodologies were utilized: (1) an axisymmetric retrieval technique was developed to extract, from single-Doppler radar data, the 3D wind distribution and tornado vortex structure; and (2) a tornado-scale model was created that allowed for the specification of observed winds at the lateral and top boundaries. The axisymmetric analysis of the 12 May 2004 DOW data revealed different vortical structures at different times in the tornado’s evolution. Correspondingly, differences existed in the peak velocities and low-level angular momentum transport. As such, the second portion of this research addressed the issue of how well these observations can be modeled as well as the subsequent insight gained from analysis of the model results. Axisymmetric analyses from both the 12 May 2004 Harper, KS and 30 May 1998 Spencer, SD tornadoes were used as lateral boundary conditions on the numerical model. These boundary conditions were chosen during different times of the tornadoes’ life cycles. The model results showed variability in vortex structure between each of the different sets of boundary conditions. Despite the analysis of fully two-celled vortices in the radar data, the model was unable to replicate a fully two-celled flow. To some degree this was shown to depend upon the chosen roughness values. The boundary conditions were found to exert control over tornado vortex intensity. The differences between the radar analyses and model results elucidated the critical properties of the flow necessary to replicate observations

The Great Plains Irrigation Experiment (GRAINEX)

Extensive expansion in irrigated agriculture has taken place over the last half century. Due to increased irrigation and resultant land use land cover change, the central United States has seen a decrease in temperature and changes in precipitation during the second half of 20th century. To investigate the impacts of widespread commencement of irrigation at the beginning of the growing season and continued irrigation throughout the summer on local and regional weather, the Great Plains Irrigation Experiment (GRAINEX) was conducted in the spring and summer of 2018 in southeastern Nebraska. GRAINEX consisted of two, 15-day intensive observation periods. Observational platforms from multiple agencies and universities were deployed to investigate the role of irrigation in surface moisture content, heat fluxes, diurnal boundary layer evolution, and local precipitation. This article provides an overview of the data collected and an analysis of the role of irrigation in land-atmosphere interactions on time scales from the seasonal to the diurnal. The analysis shows that a clear irrigation signal was apparent during the peak growing season in mid- July. This paper shows the strong impact of irrigation on surface fluxes, near-surface temperature and humidity, as well as boundary layer growth and decay