On October 13th, Nangka, the 16th typhoon of the year, made landfall in Qionghai City, Hainan. From October 12th to14th 2020, Shanghai Typhoon Institute China Meteorological Administration, in cooperation with the Institute of Atmospheric Physics, Chinese Academy of Sciences, Hong Kong Observatory, and other institutes and research centers conducted a sea-land-air field campaign over the South China Sea aiming at Nangka. Prof. DUAN Wansuo’s team of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics identified and provided the sensitive regions, where the observations were most probable to improve the forecasts for this field campaign 24 hours in advance using conditional nonlinear optimal perturbation (CNOP) method (Fig. 1a). Massive valuable data was obtained from a variety of observational platforms.

Using the dropsonde data obtained in this field observation, Prof. DUAN’s team did assimilation experiments to illustrate the availability of the aforementioned sensitivity on improving track forecasts. It is shown that the forecasted track assimilating the dropsonde data #2-6 in the sensitive region is closer to the best than that assimilating data #7-11 in non-sensitive area, even closer than that assimilating all the data.

As another milestone after the first integration of the CNOP and Fengyun-4 satellite observations for another three typhoons Higus, Maysak, and Chan-Hom in 2020, this field observation marks the availability of CNOP in the operational targeted observations for tropical cyclones.