Contribution of tropical cyclones to extreme rainfall events in the southeastern United States

Abstract

[1] Extreme precipitation has been increasing in the United States over the past century. In light of the associated impacts and possible linkages to climate change, this topic has garnered a great deal of attention from the scientific community and general public. Because tropical cyclones are a common source of heavy rainfall in the southeastern United States, we examined the contribution of tropical cyclone precipitation relative to overall extreme precipitation from all weather systems combined. We used a surface observation network over the period 1972-2007, consisting of first-order and Cooperative Observer Program weather stations. Furthermore, to account for precipitation that may be unmeasured by rain gauges because of windy conditions during tropical cyclones, we employed a wind-corrected data set and the North American Regional Reanalysis. According to several metrics of extreme precipitation, we found that extreme precipitation from tropical cyclones has been increasing over the past few decades. Additionally, the contribution of tropical cyclone precipitation to overall extreme precipitation has been significantly increasing by approximately 5%-10% per decade in the southeastern Atlantic coastal states. We attribute this rise in tropical cyclone contribution to an increase in both the storm wetness (precipitation per storm) and storm frequency over the period of record. There is little evidence that changes in storm duration are responsible for the increase. As such, we believe that an important factor in accurately projecting changes in extreme precipitation rests on whether tropical cyclone activity is driven more by natural decadal oscillations or by large-scale warming of the environment.

Moisture transport by Atlantic tropical cyclones onto the North American continent

“…On average, 0.15 Eg (ensemble mean) of moisture, equivalent to 11.4 % ( Table 3) of seasonal onshore moisture transport can be attributed to Atlantic TCs during 1980-2012, which is of comparable magnitude as the precipitation percentages (10 % of Florida's annual rainfall (Knight and Davis 2007); 4−15 % of the South East US (Rodgers et al 2001;Knight and Davis 2009;Konrad and Perry 2009;Prat and Nelson 2013)). The mean value for 1980-1994, a relatively quiet TC period (Goldenberg 2001), is 8.8 %, and the mean for the more active 1994-2012 period is 14.1 %.…”

“…Lastly, the atmospheric moisture exchange across the coastline is relevant to the continental-scale water budget, but precipitation responses are relevant in both coastal and inland areas. Landfalling TCs and their associated rainfall generally weaken quickly due to the isolation of the inner core from the warm, moist ocean surface (Ren et al 2007;Knight and Davis 2009;Dare et al 2012). Despite this general weakening, interactions with other synoptic systems (Konrad and Perry 2009;Dare et al 2012) or local orography (Brun and Barros 2014) may continue to produce rainfall further inland.…”

The potential role of land cover on secular changes of the hydroclimate of Peninsular Florida

“…1 It is one of the wettest regions of the continental US 2 that also experiences a fair share of extreme wet events from land falling tropical cyclones. [3][4][5] Florida, owing to its relatively mild climate has witnessed an explosive growth in its population in the twentieth Century, expanding at 20-80% per decade. 6 This high growth rate was stymied slightly by the great recession in the first decade of the new century, and the population is now anticipated to reach 23 million by 2030.…”

Contribution of large-scale midlatitude disturbances to hourly precipitation extremes in the United States

“…Note that color bars cover different ranges contribution to 1-h AMP is weaker and falls within the confidence range and is thus proportionate to the jet stream frequency. In the rest of the US, the jet stream contribution to 1-h AMP is nominal as precipitation extremes in these areas are generally set when other extra-tropical frontal systems (Marquardt Collow et al 2016), tropical cyclones (Knight and Davis 2009;Kunkel et al 2010), meso-scale convective systems (Kunkel et al 2012) or purely localized convective processes transit over the region.…”