Abstract:Based on the daily hail data at 175 stations in Beijing, Tianjin and Hebei Province (BTH for short hereinafter) during 1979 to 2008, using climate trend coefficient, trend rate, concentration degree (CD), concentration period (CP), and continuous power spectrum, the multiple time scale variation characteristics and trend variation of hail in BTH area are analyzed. It focuses on the four different key regions. Meanwhile, the significance of trend coefficient is tested by Monte Carlo scheme. The results show that the hail during last 30 years has increased obviously, the negative trend of hail is that reduction is larger in the northern areas than the southern areas, and larger in the mountain regions than the plain regions; there are 2.0-2.5 year periodic oscillations for interannual variations in all key regions, the inter annual change of the occurring frequency of hail is characteristic of quasi biennial oscillation (QBO); The hail concentration degree (HCD) in the southern area was the biggest, indicating that the time when hail occurred in this key region was relatively concentrated; The hail concentration period (HCP) in all regions except southern area being in pentad 31 (about early June), was pentads 36-37， indicating that hail mainly occurred from late June to early July. Analysis on abrupt climate change using accumulated anomaly method and Yamamoto method shows that an abrupt decreasing occurred in 1993, especially in mountain regions.