Stable components in extended-range forecasting during the continuous high temperature event in August 2013 over the mid-eastern China

Abstract

Based on the continuous high temperature process over the mid-eastern China in August 2013, using the NCEP/NCAR (United States National Centers for Environmental Prediction/National Center for Atmospheric Research) daily average of 500 hPa height field, the wind field reanalysis data, and the NOAA (National Oceanic and Atmospheric Administration) reconstruction sea surface temperature (SST) data, through the selection method similar to the early adoption of SST forcing, band-pass filtering and empirical orthogonal function decomposition method to extract the 10-30 days of stable components, and through a stable component of diagnostic analysis, we investigate the mechanisms for sustaining and reducing high temperature process. Results show that by selecting and using the case that is the most similar to a pre-SST forcing 30-year climatology instead of the normal 30-year climatology (1981-2010), the steady-state component extracted climate proportion is reduced, and the proportion of anomalously stable components is significantly enhanced and the described influence strength and stability are improved significantly, which can more clearly show the extended maintenance mechanism of weather processes. It suggests that early consideration SST forcing in the extraction component is very necessary. Meanwhile, the analysis of extension of stable components shows that the process of maintaining and reducing high temperature is mainly caused by the combined effect of the Arctic Oscillation, continental high latitudes zonal circulation situation in Asia and the western Pacific subtropical high intensity and location.