Abstract
Recent climate modeling studies point to an increase in tropical cyclone rainfall rates in response to climate warming. These studies indicate that the percentage increase in tropical cyclone rainfall rates often outpaces the increase in saturation specific humidity expected from the Clausius-Clapeyron relation (~7% °C−1). We explore the change in tropical cyclone rainfall rates over all oceans under global warming using a high-resolution climate model with the ability to simulate the entire intensity spectrum of tropical cyclones. Consistent with previous results, we find a robust increase of tropical cyclone rainfall rates. The percentage increase for inner-core tropical cyclone rainfall rates in our model is markedly larger than the Clausius-Clapeyron rate. However, when the impact of storm intensity is excluded, the rainfall rate increase shows a much better match with the Clausius-Clapeyron rate, suggesting that the “super Clausius-Clapeyron” scaling of rainfall rates with temperature increase is due to the warming-induced increase of tropical cyclone intensity. The increase of tropical cyclone intensity and environmental water vapor, in combination, explain the tropical cyclone rainfall rate increase under global warming.
Highlights
Rainfall associated with tropical cyclones (TCs) is a prominent component of global precipitation.[1,2] The heavy rainfall and resultant freshwater flooding and/or landslides associated with landfalling TC events account for numerous fatalities and large socioeconomic losses.[3,4] One of the most prominent examples is Hurricane Harvey in 2017, the second costliest tropical cyclone and the wettest tropical cyclone on record in the United States.[5]
HiFLOR projects an increase of total precipitable water in tropical oceans (30oS–30oN) of 13.6%, close to the increase of saturated water vapor content (12.6%) indicated by the 1.8 K increase of tropical sea surface temperature (SST), assuming a 7% increase in water vapor content per degree Celsius increase in SST
We explored the physical mechanisms responsible for the projected increases of inner-core TC rainfall rates in response to climate warming, examining all TC basins and using a high-resolution global climate model (HiFLOR)
Summary
Rainfall associated with tropical cyclones (TCs) is a prominent component of global precipitation.[1,2] The heavy rainfall and resultant freshwater flooding and/or landslides associated with landfalling TC events account for numerous fatalities and large socioeconomic losses.[3,4] One of the most prominent examples is Hurricane Harvey in 2017, the second costliest tropical cyclone (behind Hurricane Katrina in 2005) and the wettest tropical cyclone on record in the United States.[5] The unprecedented rainfall from Harvey produced catastrophic flooding in the Houston metropolitan area, the primary cause for deaths and property damage. This study focuses on the future change of TC rainfall rate rather than TC translation speed,[10] it is worthwhile to point out that the latter is another important factor that affects future local rainfall amounts. There is growing interest on the extent to which the slow translation speed of Harvey may be part of a broader global slowdown of TC translation speed.[10,11,12,13]
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