Results in Physics 6 (2016) 1183–1184

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From drought to flooding in less than a week over South Carolina

http://dx.doi.org/10.1016/j.rinp.2016.11.0122211-3797/� 2016 Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

E-mail address: Jonathan.Case-1@nasa.gov

Jonathan L. CaseENSCO, Inc./NASA Short-term Prediction Research and Transition [SPoRT] Center, 320 Sparkman Dr., Huntsville, AL 35805, United States

a r t i c l e i n f o a b s t r a c t

Article history:Received 15 June 2016Received in revised form 2 November 2016Accepted 8 November 2016Available online 10 November 2016

Keywords:Extreme precipitationFloodingNASALand surface modelingSoil moisture

A deep tropical moisture connection to Hurricane Joaquin led to historic rainfall and flooding over SouthCarolina from 3 to 5 October 2015, erasing the prevailing moderate to severe meteorological and agricul-tural drought that had developed fromMay through September. NASA’s Global Precipitation Mission con-stellation of satellites and a real-time implementation of the NASA Land Information System highlight theprecipitation and land surface response of this event.� 2016 Elsevier B.V. This is an open access article under the CCBY-NC-ND license (http://creativecommons.

org/licenses/by-nc-nd/4.0/).

Introduction

A closed upper-level low pressure system over the SoutheasternU.S. combined with a deep tropical moisture connection from Hur-ricane Joaquin led to historic rainfall and flooding over South Car-olina (SC) in early October 2015. A wide swath of central SC fromthe coast to Columbia received over 500 mm rainfall (�20+ inches),most of it during a 2–3 day span. The rainfall erased the prevailingmoderate to severe drought in the Carolinas that had developedduring the late spring and summer. The NASA Global PrecipitationMeasurement (GPM) mission and Short-term Prediction Researchand Transition (SPoRT; [2]) Center’s real-time configuration ofthe NASA Land Information System (hereafter, SPoRT-LIS; [1,3])are used to estimate the precipitation and soil moisture responsefor this extreme event.

Method and datasets

The SPoRT-LIS runs the Noah land surface model to generateobservationally-driven, modeled soil moisture estimates at �3-km resolution over a 2-meter deep soil column across the Conti-nental U.S., for enhanced situational awareness and input tolocal/regional numerical weather prediction models. Drivers ofthe SPoRT-LIS include regional and global operational atmosphericanalyses, satellite-derived green vegetation fraction, and griddedanalyses of blended radar/rain gauge precipitation estimates. Addi-tionally, the GPM constellation of satellites provide global esti-

mates of half-hourly precipitation rates through the IntegratedMulti-satellite Retrievals for GPM (IMERG) product.

Results and discussion

Fig. 1a shows the IMERG 24-h rainfall estimates ending 1200UTC 4 October (approximate peak of event), as displayed in theoperational NOAA/National Weather Service (NWS) decision sup-port system. The net effect of the extreme rainfall was the nearcomplete removal of all drought categories in the Carolinas, as seenin the U.S. Drought Monitor’s weekly product before and after theevent (Fig. 1b–c).

The response of the land surface to this extreme rainfall wascaptured by the real-time SPoRT-LIS, which depicted substantialchanges in soil moisture content over the entire 2-m soil column.Fig. 2 compares the SPoRT-LIS 0–2 m relative soil moisture (RSM)from 28 September and 5 October, with Fig. 3 highlighting theone-week change in 0–2 m RSM. The RSM represents how the vol-umetric soil moisture scales between wilting (0%) and saturation(100%) for a given soil composition, where the wilting point indi-cates that vegetation can no longer extract moisture from the soiland saturation indicates no infiltration is possible (thus, additionalprecipitation goes to runoff). Previous experience by NWS forecast-ers in the Huntsville, AL weather forecast office have found thattotal column RSM values of �60% and above indicate an enhancedthreat for areal and river flooding over northern Alabama; how-ever, these thresholds can vary depending on river basin and regio-nal soil composition. Values of 0–2 m RSM ranged from �25 to 35%on 28 September, prior to the rain event. However, by 5 October,

Fig. 1. (a) Precipitation estimate (inches) by NASA’s GPM IMERG product for the24 h ending 1200 UTC 4 October 2015; official U.S. Drought Monitor weeklyproducts valid (b) 29 September, and (c) 6 October.

Fig. 2. SPoRT-LIS 0–2 m relative soil moisture valid on 28 September (left), and 5 October 2015 (right). Masked white areas represent water or urban pixels.

ig. 3. One-week change in SPoRT-LIS 0–2 m RSM for the week ending 5 October015. Maximum weekly changes exceeding 60 units occurred in central Southarolina.

1184 J.L. Case / Results in Physics 6 (2016) 1183–1184

total column RSM increased to well above 65% in most of centralSC, and parts of North Carolina. The maximum weekly change in0–2 m RSM (Fig. 3) exceeded 60 units in central SC, suggesting adramatic shift away from wilting toward saturation. Most areasof SPoRT-LIS 0–2 m RSM exceeding �60% corresponded to areasof active river flooding across parts of southern Virginia and theCarolinas, as measured by the U.S. Geological Survey/NOAA streamgauge network (not shown).

The SPoRT-LIS also includes a daily soil moisture percentileindicating where the current gridded 0–2 m RSM soil moisture val-ues lie in the present day’s historical (33-year) soil moisture distri-bution for every county in the Continental U.S. The percentileproduct from late September depicted soil moisture between�5th–30th percentile across the Carolinas (not shown), corre-sponding closely to the U.S. Drought Monitor moderate to severedrought areas. However, after the 250–500+ mm of rainfall, theearly October soil moisture exceeded the 98th percentile in centralSC where the most severe flooding took place. More details of thisevent are documented in the NASA SPoRT blog post available at:https://nasasport.wordpress.com/2015/10/05/from-drought-to-

F2C

flooding-in-less-than-a-week-over-the-carolinas-as-depicted-by-sport-lis/.

Acknowledgements

This research was funded by Dr. Tsengdar Lee of the NASAScience Mission Directorate’s Earth Science Division for the SPoRTprogram at the NASA Marshall Space Flight Center.

References

[1] Case JL, White KD, Guyer B, Meyer J, Srikishen J, Blankenship CB et al., Real-timeland information system over the continental U.S. for situational awareness andlocal numerical weather prediction applications. 30th Conf. Hydrology, NewOrleans, LA, Amer. Meteor. Soc., 3.3; 2016.

[2] Jedlovec G. Transitioning research satellite data to the operational weathercommunity: the SPoRT paradigm. In: Bruzzone L, editor. Geoscience and remotesensing newsletter, March. New York: Institute of Electrical and ElectronicsEngineers Inc.; 2013. p. 62–6.

[3] Kumar SV, Peters-Lidard CD, Tian Y, Houser PR, Geiger J, Olden S, et al. Landinformation system � an interoperable framework for high resolution landsurface modeling. Environ Model Softw 2006;21(10):1402–15. doi: http://dx.doi.org/10.1016/j.envsoft.2005.07.004.