Characteristics of monsoon breaks and intraseasonal oscillations over central India during the last half century

• The frequency of the short break spells (3 days) and moderate active spells (4–7 days) have increased after 1977 over central Indian region.
• The area which is more prone for breaklike conditions is identified.
• The propagation characteristics of two dominant intraseasonal oscillations of Indian summer monsoon rainfall appear to be changed during the past 50 years of period.

Using 1° × 1° daily rainfall data set of 50 years, prepared by the India Meteorological Department, a detailed analysis of active and break spells has been carried out along with the investigation of propagation characteristics and the temporal variation of the intraseasonal oscillations of Indian summer monsoon rainfall. Present analysis reveals that the frequency of the short break spells (3 days) and moderate active spells (4–7 days) have increased after 1977 over a statistically homogenous Central Indian region (16.5–26.5°N; 74.5–86.5°E). It appears that most of the break spells are spatially localized over a smaller region of central India and the frequency of breaks over this region has increased in the recent decades. The area that is prone to breaklike conditions is found to be increasing after 1977 as compared with before 1977. It is also illustrated that the behavior of the intraseasonal oscillations differs in terms of propagation during the two study periods. A new method is also proposed to identify breaks over central Indian region, which shows a good match with previous studies. The results presented here are statistical in nature.