[A-AS04] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS04-04] From CWD to ICWD: Rethinking Consecutive Wet Days for Enhanced Understanding of Extreme Precipitation Events

*Manohar Reddy Venuthurla¹, Litan Kumar Ray¹ (1.National Institute of Technology Warangal)

Keywords:Precipitation extremes, Consecutive Wet Days, Intensity-based Consecutive Wet Days, ETCCDI, India

Changes in precipitation extremes, driven by climate change, are evident globally. Persistent precipitation over consecutive days contributes significantly to local-scale floods. The Expert Team on Climate Change Detection and Indices (ETCCDI) defines consecutive wet days (CWD) as the maximum number of continuous days with precipitation exceeding 1 mm within a specific time period. However, evaluating CWD based on duration alone may not effectively capture the precipitation intensity. Typically, flash flood risks correlate more directly with precipitation intensity rather than duration. Therefore, we proposed a modified CWD, termed Intensity-based Consecutive Wet Days (ICWD), considering the maximum intensity on the consecutive wet days in a year. ICWD yields a smaller count of wet days compared to traditional CWD but exhibits higher intensity. The average intensity difference between ICWD and CWD is around 7.57 mm throughout India during the period 1981-2020. Regions with a tropical savannah climate and humid subtropical climate show more pronounced changes in intensity under the ICWD approach. Conversely, tropical monsoon and hot desert climates exhibit lesser changes in the ICWD approach. Eastern parts of India are found to be more sensitive to the newly proposed ICWD index. In ICWD events, heavy precipitation days (Precipitation > 10mm) exhibit significant alterations in the study area. The ICWD event has fewer R10mm days (on an average 2 days) compared to the CWD event, indicating the concentration of more precipitation in a smaller number of days. Therefore, the proposed ICWD indicator provides a clear depiction of the hazardous nature of precipitation within a short duration. This study underscores the importance of assessing consecutive wet day events based on intensity rather than duration for an accurate understanding of changes in extreme precipitation events.