Abstract
Abstract. Sequential sampling of rainwater from Hurricane Irene was carried out in Wilmington, NC, USA on 26 and 27 August 2011. Eleven samples were analyzed for pH, major ions (Cl−, NO3−, SO42−, Na+, K+, Mg2+, Ca2+, NH4+), dissolved organic carbon (DOC) and hydrogen peroxide (H2O2). Hurricane Irene contributed 16% of the total rainwater and 18% of the total chloride wet deposition received in Wilmington NC during all of 2011. This work highlights the main physical factors influencing the chemical composition of tropical storm rainwater: wind speed, wind direction, back trajectory and vertical mixing, time of day and total rain volume. Samples collected early in the storm, when winds blew out of the east, contained dissolved components indicative of marine sources (salts from sea spray and low DOC). The sea-salt components in the samples had two maxima in concentration during the storm the first of which occurred before the volume of rain had sufficiently washed out sea salt from the atmosphere and the second when back trajectories showed large volumes of marine surface air were lifted. As the storm progressed and winds shifted to a westerly direction, the chemical composition of the rainwater became characteristic of terrestrial storms (high DOC and NH4+ and low sea salt). This work demonstrates that tropical storms are not only responsible for significant wet deposition of marine components to land, but terrestrial components can also become entrained in rainwater, which can then be delivered to coastal waters via wet deposition. This study also underscores why analysis of one composite sample can lead to an incomplete interpretation of the factors that influence the chemically divergent analytes in rainwater during extreme weather events.
Highlights
IntroductionSamples collected early in the storm, when winds weather events contributed over half the annual wet depoblew out of the east, contained dissolved components indicative of marine sources (salts from sea spray and low dissolved organic carbon (DOC))
Changes in air parcel origin and elevation as well as wind speed and direction experienced in Wilmington throughout Hurricane Irene allowed for an evaluation of how these physical factors influence the composition of rainwater www.atmos-chem-phys.net/13/2321/2013/
The air parcel origin (Fig. 7e) was marine initially with an increase in terrestrial influences with shifting wind direction as the storm passed by the region
Summary
Samples collected early in the storm, when winds weather events contributed over half the annual wet depoblew out of the east, contained dissolved components indicative of marine sources (salts from sea spray and low DOC). As the storm progressed and winds shifted to a westerly direction, the chemical composition of the rainwater became two hurricanes mond, 2005). In addition to the depositionSocf imeanricnee-dserived compocharacteristic of terrestrial storms (high DOC and NH+4 and low sea salt). This work demonstrates that tropical storms nents to land as a result of hurricanes and typhoons, shifting winds during the course of a storm could result in delivery of are responsible for significant wet deposition of ma- terrestrial compounds to coastal waters via wet deposition. Rine components to land, but terrestrial components can become entrained in rainwater, which can be delivered
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