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

Convective weather & land surface heterogeneity

From Brown and McCann, 2004

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 ExcelSort 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 LST

Majority 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

Geospatial Analysis

Dr. T. T. Fujita, University of Chicago

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

Land-use, Land-cover change & Tornado Touchdown Points

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: okellner@purdue.edu