5:15 PM - 6:45 PM
[AAS05-P06] Effects of number concentration of cloud condensation nuclei on intensity and structure of typhoon
In the Moonshot Goals 8, researches on typhoon controlling methods are now on going using numerical simulations. One of possible controlling methods is seeding with hygroscopic aerosols from aircraft. This method is proposed supposing the Rosenfeld’s hypothesis (Rosenfeld et al., 2012); typhoon intensity can be weakened with increasing number of cloud condensation nuclei (CCN) . When a large number of aerosols act as CCN are given at the outer edge of a typhoon, number of cloud droplets (Nc) are increased, deep convective clouds can be formed, convection at the outer edge can reduce the amount of water vapor entering to the typhoon center, and convection near the typhoon center would move outwards. These responses would result in typhoon weakening in terms of the central pressure. However, this hypothesis has not been examined in deep; for example, the relationship between large Nc and microphysics processes in typhoon is still unclear and only a few studies examined on the effects of number of CCN on typhoon over the Northwest Pacific region.
In this study, we investigate the effects of number of CCN on typhoon by numerical simulations for real atmospheric cases. The CReSS regional model with 4ICE-CCN (Tsuboki 2008; Murakami et al., 2021) was used with the horizontal grid spacing of 0.03 degrees. The target cases were Typhoon Jebi, Faxai and Hagibis. The value of the constant C in an equation determining the number of activated CCNs was changed in three different values (300, 3000 and 6000), the calculated Nc corresponding to the C-values were approximately 180, 880 and 1500. Totally, nine simulations were carried out for each combination of the three cases and the three C-values.
From the simulation results, a decreasing trend in central pressure (about 3 hPa) was observed at Nc: 1500. But an increase trend (about 3 hPa) was also observed by time periods. In a while a weakening response was observed at Nc: 1500, a large amount of total condensate mixing ratio was observed near the radius of maximum wind speed. The locations of the high vertical speed and the large total condensate mixing ratio were found at more outward in the large Nc case than that in the low Nc cases. Experiments applying the modified C-value over a limited region and at the limited period will be tested to clarify the spatial-temporal dependencies of the typhoon responses, near future.
Acknowledgement: This research was supported by JST "Moon Shot Type R&D Project Grant No. JPMJMS2282-04.
In this study, we investigate the effects of number of CCN on typhoon by numerical simulations for real atmospheric cases. The CReSS regional model with 4ICE-CCN (Tsuboki 2008; Murakami et al., 2021) was used with the horizontal grid spacing of 0.03 degrees. The target cases were Typhoon Jebi, Faxai and Hagibis. The value of the constant C in an equation determining the number of activated CCNs was changed in three different values (300, 3000 and 6000), the calculated Nc corresponding to the C-values were approximately 180, 880 and 1500. Totally, nine simulations were carried out for each combination of the three cases and the three C-values.
From the simulation results, a decreasing trend in central pressure (about 3 hPa) was observed at Nc: 1500. But an increase trend (about 3 hPa) was also observed by time periods. In a while a weakening response was observed at Nc: 1500, a large amount of total condensate mixing ratio was observed near the radius of maximum wind speed. The locations of the high vertical speed and the large total condensate mixing ratio were found at more outward in the large Nc case than that in the low Nc cases. Experiments applying the modified C-value over a limited region and at the limited period will be tested to clarify the spatial-temporal dependencies of the typhoon responses, near future.
Acknowledgement: This research was supported by JST "Moon Shot Type R&D Project Grant No. JPMJMS2282-04.