Attributing extreme precipitation in South China Pearl River Delta
region to anthropogenic influences based on pseudo global warming method
Abstract
In the context of the human-induced warming climate, a greater amount of
water vapor will be hold in the atmosphere, leading to more-intense
precipitation extremes on global scale. However, there is no consensus
yet on how much changes in those extremes are attributable to human
influences on a regional basis. In this study, human-influenced
variations in frequency and intensification of precipitation extremes
over the South China (SC) Pearl River Delta (PRD) region are
quantitatively assessed using the cloud-resolving Weather Research and
Forecasting (WRF) model based on the reversed pseudo global warming
(PGW) method. Forty extreme precipitation (95th percentile) events that
occurred in different seasons for 1998-2018 over the PRD region are
identified and dynamically downscaled by the WRF. The model was forced
with present and counterfactual initial and boundary conditions, with
the latter being derived by subtracting the CMIP5 7-model ensemble mean
changes from ERA-Interim reanalysis. As inferred from these global
models, the 1000-500 hPa tropospheric temperature has warmed by
~0.9 (0.8) ℃ over PRD (SC) due to human influences.
Preliminary results show that such human-induced warming can lead to
about 20% or more increase in the frequency of daily rainfall in PRD,
with the greater enhancement in non-rainy season events. Human impacts
also intensify the 95th percentile of PRD daily rainfall by around 12%
(8%) in the non-rainy (rainy) season. This super-CC increase of
non-rainy season cases probably implies the possible dynamic feedbacks,
in addition to moisture-related thermodynamic effect in human-influenced
extreme precipitation variations.