Olivia KellnerPh.D. Candidate, Purdue University
Climate Specialist, Indiana State Climate Office
Twister Tracking: Analysis of Weather Events in Indiana
Photos: Doyle McIntosh
2014 Indiana GIS Conference May 8, 2014
Land-surface Heterogeneity in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012
Founding science and hypothesis
DataClimatology
MethodsFindings
Geospatial AnalysisMethodsMapsFindings
Conclusionshttp://www.angelfire.com/theforce/storm_chasingf5/Historical%20and%20Major%20Tornado%20Outbreaks%20the%20one.htm
http://www.srh.noaa.gov/ohx/?n=april31974_40thanniversary
http://www.crh.noaa.gov/ilx/events/may302004/040530_rpts.gif
Kellner, O. and D. Niyogi, 2013, Land-surface Heterogeneity Signature in Tornado Climatology? An Illustrative Analysis over Indiana 1950-2012, Earth Interactions, e-view, doi: http://dx.doi.org/10/1175/2013EI000548.1.
Presentation Outline:
Founding science: Land-surface heterogeneity:
where the land cover or land
use is not uniform across an
area
Leads to a heterogeneous
boundary layer in terms of
temperature, dew points,
vertical velocities, and winds
Mahmood et al., 2011
Fig. 5. Inner domain average modeled (a) relative humidity, (b) dew point temperature, (c) ground temperature, (d) two-meter temperature, and (e) planetary boundary layer height for control, bare soil, grassland, and forest.
Mahfouf et al., 1987
Can these
surface
discontinuities
modify the
boundary layer
enough to
impact storm
dynamics and
evolution?
Convective weather and land surface heterogeneity: physiographic boundaries, land use changes, & urban areas
From Brown and Arnold, 1998: Figure 6. Spatial distribution for all convective cloud masses(dots, both initial and vertically enhanced) for 34 weak synoptic flow days, July–August, 1986–1991, in the aggregate.
From Changnon et al., 1991 Journal of Applied Meteorology
Indiana’s land surface, rich with physiographic boundaries, land-surface heterogeneity, topography, and distinct, isolated urban regions may influence the evolution of convective weather (specifically tornado touchdown locations).
Hypothesis
http://media.wfyi.org/NaturalHeritage/learn/regions.htmlhttps://ou-gisapplications.wikispaces.com/Indiana+Land+Usehttp://pubs.usgs.gov/of/2004/1451/rupp/
ClimatologyStorm Prediction Center
(SPC) Storm reports, available in their Severe Weather Database Files Inclusive of
DateTimeTouchdown in lat/longCountyF-scaleInjuriesFatalities
SPC SVRGIS webpage: http://www.spc.noaa.gov/gis/svrgis/ Tornado touchdown points States Cities Counties Population Density (2010
raster file, density per square kilometer)
Land cover: U.S.G.S Enhanced Historical Land-use and Land-cover Data sets
DEM: Ball State University
Storm and Geospatial Data Sources
Geospatial Data
Implementation of .csv files of storm data into Excel
Sort data by:DateTimeF-scale
Compute tornado days and climatological data by parameters investigatedMonthYearF-scale
Weak (F0-F1) and Strong (F2-F5)Increase/decrease in annual tornado days
Also investigated antecedent rainfall at 1, 3, and 6 month periods and ENSO phase to annual number of tornado days
Climatology Development
ClimatologyMost active time of day
weak tornadoes: 4-7pm LST;
strong tornadoes: 2-4pm and 5-8pm LST;
all tornadoes 4-8pm LSTMajority of Indiana’s
tornadoes are weak tornadoes (50%)
30-year moving averages show no increase or decrease in annual tornado days
30-year moving averages by climate division show an increase in annual tornado days in southern most climate divisions from 1 day a year to 3 days a year
ENSO: rate at which ENSO changes phase appears to relate to more active seasons in Indiana
Weak relationship between 6-month antecedent drought conditions and number of tornado days
This shift is a result of the windshear environment more common with strong tornadoes
Spatial analyst tools: Kernel densityMap algebra Slope calculator
Conversion toolsAnalysis tools:
Buffer“Select features within”
Methods
Investigate the potential impacts of:
Changes in elevationChange in slope of 5
degrees or more over a distance of ~100 meters
Change in land cover6 classes
ForestUrbanAgricultureBarrenWetlands/water bodiesRange land
Urban areasCity centroidsUrban area shapefiles
Population densityPeople per square
kilometer
Elevation & Tornado Touchdown Points
http://jasonahsenmacher.wordpress.com/category/terrain/
http://pubs.usgs.gov/of/2004/1451/rupp/
Is this happening here in Indiana?
Urban Areas, City Centroids, & Tornado Touchdown Points
~1 mile
~9 miles
Tornado “rings” ?~Noted by Fujita in other citiessuch as Chicago in early 1970s
Population & Tornado Touchdown Points
Percentage of Total Tornadoes 1950-2012 (1285 total) within 1-4 km of Different 2010 Population Density
Classes (People/km2)
Class Class Range: 1 km 2 km 3 km 4 km
Class 2 238-847 39 51 60 67
Class 3 848-1,779 24 30 35 41
Class 4 1,780-3,309 10 13 16 19
Class 5 3,310-6,497 1 2 3 4
Class 6 6,498-13,879 0 0 0 1
Correlation: -0.79 -0.79 -0.80 -0.80
An indirect relationship: higher percentage of tornado touchdown points in land area with lower populations
However, the spatial distribution closeto major cities towns suggest a populationbias…
El Niño vs. La Niña Years
Spatially different patterns -> La Niña more concentrated touchdown locations In terms of climatology, no year has a greater risk for more tornadoesTransition between phases appears to contribute to active and less active tornado years
ConclusionsMeteorology &
climatology are very cartographically intensive sciences (forecasters constantly look at & analyze maps)! Sadly, a gap between
those that know meteorology & the benefits of geospatial analysis is present
Indiana tornado days have not increased or decreased through time Note that tornado days
are not the same as tornadoes!
Any given day can have 1 – 20+ tornadoes
Several land surface relationships may be occurring topographyphysiographic regions land use : 42 % & 64%
touched down within 1 km of forest & urban land areas, respectively
All tornadoes: 43% & 61% touched down within 1 km of forest and urban, respectively
Supports land-surface heterogeneity hypotheses:Boundaries of temperature,
dewpoints, CAPE, vertical velocities , & surface roughness when transitioning from one land use to another
Thank you! - Questions?!?!Special thanks to Dr. David L. Arnold & Tim
Samaras for inspiration and devotion to novel, challenging research seeking to unravel the unsolved mysteries of severe weather & tornadoes
NWS Indianapolis for continued supportDev Niyogi & the Indiana State Climate Office
Email: [email protected]