Reply to Comment by E. T. Swenson, D. Das, and J. Shukla on “Unraveling the Mystery of Indian Summer Monsoon Prediction: Improved Estimate of Predictability Limit”

Abstract

Swenson et al. (2020, https://doi.org/10.1029/2020JD033037) (hereafter SN20) raise some technical issues on observed correlations between the synoptic variances and the seasonal mean of area averaged (all-India or central India) Indian summer monsoon rainfall (ISMR) reported in Saha et al. (2019, https://doi.org/10.1029/2018JD030082) (hereafter SA19). SN20 did not comment on the other major finding of SA19 on model-based prediction and predictability of the ISMR. Therefore, we focus in this reply only on the observational part of SA19 even though the modeling part is closely related to the observations. While we disagree with SN20 in all three aspects of their comments, we present additional analysis to clarify the scientific basis for our selection of area averaging, the selection of 30-year period for the study and argue that the relevant probability density function of daily rainfall is not that of the individual stations (or grid points) but that of the daily averaged rainfall over a comparable area. On the debate of small area averaging (major point of SN20), we argue that it is physically meaningless in the context of ISMR.