[A-AS01] From Weather Predictability to Controllability

[AAS01-P09] Relationship between tropical cyclone intensity and large-scale atmospheric responses

*Tomoe Nasuno^1,2, Yohei Yamada¹, Masuo Nakano^1,2, Chihiro Kodama^1,2 (1.Japan Agency for Marine-Earth Science and Technology, 2.Typhoon Science and Technology Research Center, Yokohama National University)

Keywords:Tropical Cyclones, Rossby wave response, global nonhydrostatic model

Tropical cyclones (TCs) do not only cause disastrous weather events but also have an influence on the large-scale atmospheric environment. Downstream development of Rossby waves along the westerly jet and enhancement of remote precipitation through moisture transport are typical examples. However, dependence of such atmospheric responses to the TC intensity is not well known, which is relevant to the estimation of possible side effect by TC intervention. Taking an advantage of high-resolution global atmospheric model, we aim to clarify how and to what extent TC intensity modification can cause systematic change in the atmospheric responses. We conducted sensitivity simulations varying the TC intensity for four TC cases (TY1821, TY1915, TY1919, TY2214) which induced severe damages over Japan. In the sensitivity simulations, we reduce the TC intensity at different degrees by horizontal smoothing within the inner core, with keeping other conditions same as the unperturbed simulation (CTL). We evaluate the modification impact by pattern correlation of atmospheric fields (500-hPa geopotential height) between the sensitivity simulations and CTL and root mean square difference (RMSD), averaged in the western North Pacific domain. We confirm that the pattern correlation keeps nearly unity within the first week after the modification, while RMSD slightly increases after 4~5 days for all the TC cases. We further examine the evolution of the modification impact by regression of the 500-hPa geopotential height on the degree of TC intensity reduction. We find that the impacts are limited around the TC during initial few days, and synoptic-scale wave-like signal emanates from TC to the higher latitudes after the 3~6 days from modification, which is considered as the period when the systematic impact of modification significantly appears. Beyond one week after the modification, large-scale wavy patterns along the midlatitude westerly jet develop. The regressed synoptic-scale patterns during the 3~6 days indicate that the TC intensity reduction tends to reduce the atmospheric responses to the TC in CTL. At the same time, the areas where disturbance exists are also sensitive to the change in the TC intensity, sometimes leading to large amplification of the modification impact.