[A-CG36] Dynamics of Oceanic and Atmospheric Waves, Vortices, and Circulations

[ACG36-11] An introduction of seamless detection of cutoff lows and preexisting troughs

*Kasuga Satoru¹, Meiji Honda², Jinro Ukita², Shozo Yamane³, Hiroaki Kawase⁴, Akira Yamazaki⁵ (1.Mie University, 2.Niigata University, 3.Doshisha University, 4.Meteorological Research Institute, 5.JAMSTEC)

Keywords:Cutoff lows

A new automated numerical scheme to detect cutoff lows and their preexisting troughs from meteorological global reanalysis data has been proposed (Kasuga et al. 2021). The proposed scheme quantifies the geometric features of depression from its horizontal height profile. The height slope of a line intersecting the depression bottom and the nearest tangential point (optimal slope) locally indicates not only the intensity but also scale and background height gradient of an isolated depression from a raw snapshot field of geopotential height on a pressure level. Thus, the proposed scheme is easy to handle, and the products are highly objective. In the process of the calculation, a local background height slope is automatically removed from a geopotential height field, so that the cutoff low and its preexisting trough are seamlessly detected as an identical depression. Using two-dimensional Gaussian as a depression in an simply idealized height field, we have confirmed that the above features of the proposed detection are mathematically proved and mathematical features are also observed in the reanalysis. Details of the detection and differences from the preceding schemes will be introduced on the session. A tracking scheme using the parameters obtained from the detection scheme have been also developed and will be introduced in the session A-GC33.