27 citations · 62 across the 10 of their papers we have counts for
10 papers
Principal Geodesic Analysis applied to climate time series
Nozomi Sugiura
Principal Geodesic Analysis (PGA) is applied to a climate time series. First, we transform each multidimensional sequence into the path signature. Since the signature lives in a cu…
Introduction to the signature method
Nozomi Sugiura
The sequential data observed in earth science can be regarded as paths in multidimensional space. To read the path effectively, it is useful to convert it into a sequence of number…
Simple El Niño prediction scheme using the signature of climate time series
Nozomi Sugiura, Shinya Kouketsu
El Niño is a typical example of a coupled atmosphere--ocean phenomenon, but it is unclear whether it can be described quantitatively by a correlation between relevant climate event…
Clustering global ocean profiles according to temperature-salinity structure
Nozomi Sugiura
An unsupervised clustering using a Gaussian mixture model is applied to Argo profiles distributed over the entire ocean. We employ as the coordinate components in feature space the…
Estimating the population mean for a vertical profile of energy dissipation rate
Nozomi Sugiura, Shinya Kouketsu, Shuhei Masuda +2
Energy dissipation rates are an important characteristic of turbulence; however, their magnitude in observational profiles can be incorrectly determined owing to their irregular ap…
Machine learning technique using the signature method for automated quality control of the Argo profiles
Nozomi Sugiura, Shigeki Hosoda
A profile from the Argo ocean observation array is a sequence of three-dimensional vectors composed of pressure, salinity, and temperature, appearing as a continuous curve in three…
The Onsager--Machlup functional for data assimilation
Nozomi Sugiura
When taking the model error into account in data assimilation, one needs to evaluate the prior distribution represented by the Onsager--Machlup functional. Through numerical experi…
Synchronization of coupled stick-slip oscillators
Nozomi Sugiura, Takane Hori, Yoji Kawamura
A rationale is provided for the emergence of synchronization in a system of coupled oscillators in a stick-slip motion. The single oscillator has a limit cycle in a region of the s…
A framework for interpreting regularized state estimation
Nozomi Sugiura, Shuhei Masuda, Yosuke Fujii +3
Four-dimensional variational data assimilation (4D-Var) on a seasonal-to-interdecadal time scale under the existence of unstable modes can be viewed as an optimization problem of s…
Coarse-grained sensitivity for multiscale data assimilation
Nozomi Sugiura
We show that the effective average action and its gradient are useful for solving multiscale data assimilation problems. We also present a procedure for numerically evaluating the…