Trends During Satellite Era (1961-2010)
Table 2 presents the annual and seasonal trends in CDs, TCs and Severe TCs over the NIO, BOB and AS during the satellite era, 1961-2010. Frequencies of CDs, TCs and severe TCs over the BOB during the last five decades show significant decreasing trends in the monsoon and post-monsoon seasons as well as for the year as a whole (Fig. 2). Similar significant decreasing trends are observed in the frequencies of CDs, TCs and severe TCs over the NIO except for the severe TCs during the monsoon season. There are no significant trends in the pre-monsoon season over both BOB and NIO. It is interesting to note that contrasting trends emerge for post-monsoon severe TCs over BOB and NIO for the two periods 1901-2010 and 1961-2010 with significant positive trends in the former period and significant negative trends in the later period. Over the AS, there are no significant trends in CDs, TCs and severe TCs frequencies in the last five decades for any season and year as a whole unlike long-term significant increasing trend in frequency of CDs for the monsoon and post-monsoon seasons and a year as whole based on data of 19012010. It may be mentioned that these results are consistent with findings of Srivastava et al. (2000), Singh et al. (2000), Mandal and Premkrishna (2009) and Mohapatra et al. (2014).
Fig. 1 Frequency of CDs in a monsoon season and b year as a whole over the (i) BOB and (ii) AS; c frequency of CDs in post-monsoon season over the AS, d frequency of TCs over the BOB during (i) monsoon season and (ii) year as a whole and e frequency of severe TCs over the BOB during post-monsoon season for the period of 1901-2010. Linear trend lines are also shown