Abstract:

The climatological distributions and the long-term trends in the extreme precipitation events were investigated over Guangxi province, China. The extreme precipitation events were diagnosed using the 0.25°×0.25° APHRODITE’s (Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation) daily gridded precipitation from the Research Institute for Humanity and Nature and Meteorological Research Institute of Japan Meteorological Agency. The Fast Fourier Transform (FFT) was used to identify the periodicities of the temporal variations in the different extreme precipitation events. A two-dimension Cross-Correlation Analysis (CCA) was performed to examine the lag-correlations between the Niño3.4 index from the CPC/NOAA and the different extreme precipitation indicators. Based on the lagged periods indicated by the CCA, the potential responses of the different extreme indicators to the different phases of ENSO were analyzed. The result shows a slight increasing trend in dry days (DD) and slight decreasing trends in heavy-rain days (HRD), consecutive dry days (CDD) and consecutive wet days (CWD) during 1951-2007. The FFT power spectrums of the different extreme precipitation indicators exhibit significant spectrum power with periods around 3-7 years, implying a potential association with ENSO. The CCA indicates a positive (negative) correlation between the wet (drought) events and ENSO with a lagged period around 6-18 months. The mean Niño3.4 index averaged during the 6-18 months, as indicated by the CCA, was used to identify the corresponding phases of ENSO for the extreme precipitation in each month. The potential responses in the El Niño phases relative to the La Niña phases show a general decrease (increase) in the DD (HRD) and CDD (CWD). However, these potential responses are not statistically significant in most of the region over Guangxi province. As shown by the NCEP/NCAR 40-year reanalysis data, the responses of moist static stability, the lower-level difference of temperature and dew-point, and the mid-tropospheric barotropic moist potential vorticity tend to be unfavorable for the increase in extreme rainfall in the El Niño phases, which may limit statistical significance of the responses of the different extreme precipitation indicators.

Key words: extreme precipitation events, Guangxi province, ENSO