Using high-resolution simulations to quantify underestimates of Tornado intensity from in situ observations

Nathan A. Dahl, David S Nolan, George H. Bryan, Richard Rotunno

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Large-eddy simulations are used to produce realistic, high-resolution depictions of near-surface winds in translating tornadoes. The translation speed, swirl ratio, and vertical forcing are varied to provide a range of vortex intensities and structural types. Observation experiments are then performed in which the tornadoes are passed over groups of simulated sensors. Some of the experiments use indestructible, error-free anemometers while others limit the range of observable wind speeds to mimic the characteristics of damage indicators specified in the enhanced Fujita (EF) scale. Also, in some of the experiments the sensors are randomly placed while in others they are positioned in regularly spaced columns perpendicular to the vortex tracks to mimic field project deployments. Statistical analysis of the results provides quantitative insight into the limitations of tornado intensity estimates based on damage surveys or in situ measurements in rural or semirural areas. The mean negative bias relative to the "true" global maximum 3-s gust at 10 m AGL (the standard for EF ratings) exceeds 10 m s-1 in all cases and 45 m s-1 in some cases. A small number of sensors are generally sufficient to provide a good approximation of the running time-mean maximum during the period of observation, although the required spatial resolution of the sensor group is still substantially higher than that previously attained by any field program. Because of model limitations and simplifying assumptions, these results are regarded as a lower bound for tornado intensity underestimates in rural and semirural areas and provide a baseline for further inquiry.

Original languageEnglish (US)
Pages (from-to)1963-1982
Number of pages20
JournalMonthly Weather Review
Volume145
Issue number5
DOIs
StatePublished - May 1 2017

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tornado
sensor
simulation
vortex
damage
gust
anemometer
experiment
large eddy simulation
surface wind
in situ measurement
statistical analysis
spatial resolution
wind velocity
in situ

Keywords

  • In situ atmospheric observations
  • Numerical analysis/modeling
  • Sampling
  • Tornadoes

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Using high-resolution simulations to quantify underestimates of Tornado intensity from in situ observations. / Dahl, Nathan A.; Nolan, David S; Bryan, George H.; Rotunno, Richard.

In: Monthly Weather Review, Vol. 145, No. 5, 01.05.2017, p. 1963-1982.

Research output: Contribution to journalArticle

Dahl, Nathan A. ; Nolan, David S ; Bryan, George H. ; Rotunno, Richard. / Using high-resolution simulations to quantify underestimates of Tornado intensity from in situ observations. In: Monthly Weather Review. 2017 ; Vol. 145, No. 5. pp. 1963-1982.
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