Variation Trends of Asymmetrical Precipitable Water Vapor Outside the Tropical Cyclone Center Over the WNP and WSP Ocean

Precipitable water vapor (PWV) is one of the crucial driving forces for tropical cyclone (TC) genesis. Under the impact of global warming, TCs have changed their way to concentrate PWV from the ambient atmosphere. This study starts with the asymmetric characteristics of PWV in the TC's north and south sides using altimetry-satellite-based PWV profiles paired with 367 TCs over the western Pacific Ocean between 2008 and 2020. The results suggest that the TC-concentrated PWV has a north-leaning and south-leaning property over the western North Pacific (WNP) and western South Pacific (WSP), respectively. Moreover, it is observed that the radius of TC-concentrated PWV has broadened by 5.44% (5.83%) over the WNP (WSP) from 2008 to 2020. In contrast, the PWV gradient has decreased by 23.5% (17.5%) over the WNP (WSP). Our findings highlight that the TC-concentrated PWV can be used as an important indicator of TC responses to global warming. Global warming has deepened people's impression in tropical cyclone (TC) in the recent decades. For instance, the asymmetrical properties of precipitable water vapor (PWV) in the TC's north and south sides have a sensitive response to global warming. The sea surface temperature warmed at a rate of 0.047 (0.045) & DEG;C per year over the western North (South) Pacific Ocean between 2008 and 2020, which directly results in an increase of 0.16 (0.31) kg & BULL;m-2 yr-1 in PWV. This makes it easier for TCs to concentrate more water vapor into the TC's vortex area. Statistically, the TC-concentrated PWV radius expanded by 5.44% (5.83%) or 4.0 (4.7) km & BULL;yr-1 over the western North (South) Pacific Ocean during the period 2008-2020. This finding provides another clue to TC's slowdown of translation speed and the increased TC-induced flood risk in the recent decades. The tropical cyclone (TC)-concentrated precipitable water vapor (PWV) features a north-leaning (south-leaning) property for TCs over western North Pacific (WNP) (western South Pacific (WSP)) ocean basinsThe TC-concentrated PWV area outstretches by 5.44% (5.83%) between 2008 and 2020 over WNP (WSP) ocean basinsThe spatial gradient of TC-concentrated PWV decreased by 23.5% (17.5%) between 2008 and 2020 over WNP (WSP) ocean basins