Robert Trapp

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Papers by Robert Trapp

Mobile radiosonde deployments during the Mesoscale Predictability Experiment (MPEX): Rapid and adaptive sampling of upscale convective feedbacks

Bulletin of the American Meteorological Society, 2016

The Mesoscale Predictability Experiment (MPEX) was a field campaign conducted 15 May through 15 J... more The Mesoscale Predictability Experiment (MPEX) was a field campaign conducted 15 May through 15 June 2013 within the Great Plains region of the United States. One of the research foci of MPEX regarded the upscaling effects of deep convective storms on their environment, and how these feed back to the convective-scale dynamics and predictability. Balloon-borne GPS radiosondes, or “upsondes,” were used to sample such environmental feedbacks. Two of the upsonde teams employed dual-frequency sounding systems that allowed for upsonde observations at intervals as fast as 15 min. Because these dual-frequency systems also had the capacity for full mobility during sonde reception, highly adaptive and rapid storm-relative sampling of the convectively modified environment was possible. This article documents the mobile sounding capabilities and unique sampling strategies employed during MPEX.

An Object-Oriented Characterization of Extreme Precipitation-Producing Convective Systems in the Midwestern United States

Monthly Weather Review, 2012

Extreme precipitation was identified in the midwestern United States using an object-oriented app... more Extreme precipitation was identified in the midwestern United States using an object-oriented approach applied to the NCEP stage-II hourly precipitation dataset. This approach groups contiguous areas that exceed a user-defined threshold into “objects,” which then allows object attributes to be diagnosed. Those objects with precipitation maxima in the 99th percentile (>55 mm) were considered extreme, and there were 3484 such objects identified in the midwestern United States between 1996 and 2010. Precipitation objects ranged in size from hundreds to over 100 000 km2, and the maximum precipitation within each object varied between 55 and 104 mm. The majority of occurrences of extreme precipitation were in the summer (June, July, and August), and peaked in the afternoon into night (1900–0200 UTC) in the diurnal cycle. Consistent with the previous work by the authors, this study shows that the systems that produce extreme precipitation in the midwestern United States vary widely acr...

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Extreme storms

1. Human activities have contributed substantially to observed ocean–atmosphere variability in th... more 1. Human activities have contributed substantially to observed ocean–atmosphere variability in the Atlantic Ocean (medium confidence), and these changes have contributed to the observed upward trend in North Atlantic hurricane activity since the 1970s (medium confidence). 2. Both theory and numerical modeling simulations (in general) indicate an increase in tropical cyclone (TC) intensity in a warmer world, and the models generally show an increase in the number of very intense TCs. For Atlantic and eastern North Pacific hurricanes and western North Pacific typhoons, increases are projected in precipitation rates (high confidence) and intensity (medium confidence). The frequency of the most intense of these storms is projected to increase in the Atlantic and western North Pacific (low confidence) and in the eastern North Pacific (medium confidence). 3. Tornado activity in the United States has become more variable, particularly over the 2000s, with a decrease in the number of days p...

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Extreme storms

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A Storm Safari in Subtropical South America: Proyecto RELAMPAGO

Bulletin of the American Meteorological Society

This article provides an overview of the experimental design, execution, education and public out... more This article provides an overview of the experimental design, execution, education and public outreach, data collection, and initial scientific results from the Remote Sensing of Electrification, Lightning, and Mesoscale/Microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign. RELAMPAGO was a major field campaign conducted in the Córdoba and Mendoza provinces in Argentina and western Rio Grande do Sul State in Brazil in 2018–19 that involved more than 200 scientists and students from the United States, Argentina, and Brazil. This campaign was motivated by the physical processes and societal impacts of deep convection that frequently initiates in this region, often along the complex terrain of the Sierras de Córdoba and Andes, and often grows rapidly upscale into dangerous storms that impact society. Observed storms during the experiment produced copious hail, intense flash flooding, extreme lightning flash rates, and other unusual lightning phenomena, but f...

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Hybrid Prediction of Weekly Tornado Activity Out to Week 3: Utilizing Weather Regimes

Geophysical Research Letters

Final report: A Bottom-up Approach to Improve the Representation of Deep Convective Clouds in Weather and Climate Models

Future changes in hail occurrence in the United States determined through convection-permitting dynamical downscaling

Journal of Climate

The effect of anthropogenically enhanced greenhouse gas concentrations on the frequency and inten... more The effect of anthropogenically enhanced greenhouse gas concentrations on the frequency and intensity of hail depends on a range of physical processes and scales. These include the environmental support of the hail-generating convective storms and the frequency of their initiation, the storm volume over which hail growth is promoted, and the depth of the lower atmosphere conducive to melting. Here, we use high-resolution (convection permitting) dynamical downscaling to simultaneously account for these effects. We find broad geographical areas of increases in the frequency of large hail ([Formula: see text]35-mm diameter) over the United States, during all four seasons. Increases in very large hail ([Formula: see text]50-mm diameter) are mostly confined to the central United States, during boreal spring and summer. And, although increases in moderate hail ([Formula: see text]20-mm diameter) are also found throughout the year, decreases occur over much of the eastern United States in ...

A radar-based study of severe hail outbreaks over the contiguous United States for 2000-2011

International Journal of Climatology

Preliminary Results From The Intermountain Precipitation Experiment (ipex)

Egs General Assembly Conference Abstracts, 2002

The Bow Echo and MCV Experiment (BAMEX): Observations and Opportunities

Bulletin of the American Meteorological Society, Jul 1, 2004

Characteristics of Sub-diurnal Extreme Precipitation-Producing Systems

Agu Spring Meeting Abstracts, May 1, 2008

ABSTRACT Few studies examine sub-diurnal precipitation extremes, instead focusing on daily extrem... more ABSTRACT Few studies examine sub-diurnal precipitation extremes, instead focusing on daily extremes. However, flash flooding occurs on shorter time-scales and significantly impacts life and property. Case studies have identified storm systems responsible for significant flooding events, but this study seeks to quantify the characteristics of systems that produce sub-diurnal extreme precipitation. Sub-diurnal extreme precipitation events are identified by examining hourly precipitation data from select stations in Indiana and Illinois during the period of 1956-2005. Timeseries of precipitation accumulations for 3- and 6- hour periods are fitted to the Pareto distribution to determine the 10-year return levels for the stations. An extreme precipitation event is defined as one that exceeds the 10-year return level over both a 3-hour and a 6-hour period. Stations in Indiana have return levels ranging from 2.02 in. to 2.74 in. for 3-hour periods, and 2.46 in. to 3.16 in. for 6-hour periods. Stations in Illinois have return levels ranging from 2.43 in. to 2.84 in. for 3-hour periods, and 2.84 in. to 3.39 in. for 6-hour periods. These return levels yield about 6 events per station over the 50-year period of record for Indiana and between 3 and 7 events per station in Illinois. Multisensor precipitation data are available beginning in 1996 for stage II analyses and 2002 for stage IV analyses. This results in a total of 6 extreme precipitation events from the Indiana stations and 5 from the Illinois stations. The automated classification procedure developed by Baldwin et al. (2005) is applied to stage II/IV analyses for each hour of each event to determine the statistical characteristics for each event. Areas of continuous precipitation above a user-defined threshold are considered a single object. The threshold value of 5 mm (0.20 in.), used here, is considered the lower bound for convective precipitation. Object characteristics include: number of pixels (4 km x 4 km), mean precipitation, variance, maximum precipitation, shape, and orientation angle. During each hour of an extreme precipitation event the object whose centroid is closest to the station is used to define the characteristics of the precipitating system. Over the course of an extreme precipitation event the maximum precipitation identified in the object corresponds well to hours in which extreme heavy precipitation (&gt; 1.00 in.) occurs. While object sizes seem to be closely related to the amount of maximum precipitation from hour to hour, sizes range from hundreds to thousands of pixels during peak maximum precipitation.

Numerical Simulation of the Genesis of Tornado - Vortices

Thesis the University of Oklahoma 1994 Source Dissertation Abstracts International Volume 55 03 Section B Page 0957, 1994

The effects of cloud base rotation on microburst dynamics: a numerical investigation

Numerical simulation of tornadolike vortices in asymmetric flow

Geophysical Monograph Series, 2000

ABSTRACT Most current knowledge of the dynamics of tornadolike vortices has been obtained from ax... more ABSTRACT Most current knowledge of the dynamics of tornadolike vortices has been obtained from axisymmetric models with initial vertical vorticity. One question which continues to elude researchers is how tornadoes, which appear at least locally axisymmetric, are born out of nonaxisymmetric ambient flow with initial horizontal vorticity only.

Mesoscale Thermodynamic Influences on Convection Initiation near a Surface Dryline in a Convection-Permitting Ensemble

Monthly Weather Review, 2015

In this study, the authors examine initiation of severe convection along a daytime surface drylin... more In this study, the authors examine initiation of severe convection along a daytime surface dryline in a 10-member ensemble of convection-permitting simulations. Results indicate that the minimum buoyancy Bmin of PBL air parcels must be small (Bmin > −0.5°C) for successful deep convection initiation (CI) to occur along the dryline. Comparing different ensemble members reveals that CAPE magnitudes (allowing for entrainment) and the width of the zone of negligible Bmin extending eastward from the dryline act together to influence CI. Since PBL updrafts that initiate along the dryline move rapidly northeast in the vertically sheared flow as they grow into the free troposphere, a wider zone of negligible Bmin helps ensure adequate time for incipient storms to mature, which, itself, is hastened by larger CAPE. Local Bmin budget calculations and trajectory analysis are used to quantify physical processes responsible for the reduction of negative buoyancy prior to CI. Here, the grid-reso...

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The Initiation of Deep Convective Clouds

Mesoscale-Convective Processes in the Atmosphere, 2013

The Atmospheric Mesoscale

Mesoscale-Convective Processes in the Atmosphere, 2013

Sensitivity of the warm rain process in convective clouds to regional trends in tropospheric warming in the contiguous U.S

The Mesoscale Predictability Experiment (MPEX)

Bulletin of the American Meteorological Society, 2015

The Mesoscale Predictability Experiment (MPEX) was conducted from 15 May to 15 June 2013 in the c... more The Mesoscale Predictability Experiment (MPEX) was conducted from 15 May to 15 June 2013 in the central United States. MPEX was motivated by the basic question of whether experimental, subsynoptic observations can extend convective-scale predictability and otherwise enhance skill in short-term regional numerical weather prediction. Observational tools for MPEX included the National Science Foundation (NSF)–National Center for Atmospheric Research (NCAR) Gulfstream V aircraft (GV), which featured the Airborne Vertical Atmospheric Profiling System mini-dropsonde system and a microwave temperature-profiling (MTP) system as well as several ground-based mobile upsonde systems. Basic operations involved two missions per day: an early morning mission with the GV, well upstream of anticipated convective storms, and an afternoon and early evening mission with the mobile sounding units to sample the initiation and upscale feedbacks of the convection. A total of 18 intensive observing periods ...

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