# Hot Topic

## X-ray telescope reveals the Milky Way’s halo of hot gas is fed by supernovae

2018-10-11

The Milky Way is a spiral galaxy up to 100,000 light years across, and our Sun is just one of hundreds of billions of stars within it. The galaxy has a halo, which is partly made up of gas accumulated from the vast expanses of intergalactic space but is also molded and supplemented by matter ejected from the galaxy’s stars. The balance between these two sources is not fully understood, and there is ongoing debate about the halo’s size and shape. RIKEN Researchers have mapped this halo gas using the Suzaku X-ray telescope and revealed how exploding stars have helped to shape this blazing shroud.

# Hot Topic

## Coffee Meeting on Oct. 5

2018-10-11

At the weekly coffee meeting on Oct.5 (Fri.), we enjoyed lots of good sweets from all over the world after a nice 15 min. talk by Chacha san (iTHEMS) on "A unique pair of triangles".

# Upcoming Events

## External Event

### Nerd Nite Tokyo

November 9 at 20:00 - 22:00, 2018

Dr. Ade Irma Suriajaya (Special Postdoctoral Researcher, iTHEMS)

Chacha will tell us about infinities, some bad math, and some good math.

Price: ¥1000, but speakers get in free

Food and drinks available at the event

Venue: Nagatacho GRID (2-5-3 Hirakawa-cho, Chiyoda-ku, Tokyo 102-0093)

Event Official Language: English

## Math Lecture

### Theory of Operator Algebras (4th)

October 18 at 15:30 - 17:00, 2018

Dr. Yosuke Kubota (Research Scientist, iTHEMS)

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: Japanese

## Math Lecture

### Theory of Operator Algebras (5th)

November 8 at 13:30 - 15:00, 2018

Dr. Yosuke Kubota (Research Scientist, iTHEMS)

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: Japanese

## Workshop

### Workshop on Recent Developments of Chiral Matter and Topology

December 6 - 9, 2018

The aim of this workshop is to gather researchers of high-energy and condensed-matter physics working on chiral Matter and Topology, to exchange ideas and establish collaborations to tackle unsolved issues and carry out future extensions. The workshop expects to welcome 40-60 participants who are interested in the aforementioned topics.

Organizers:

Tomoki Ozawa, Tetsuo Hatsuda (RIKEN iTHEMS)

Di-Lun Yang (RIKEN Nishina Center; YITP, Kyoto)

Chang-Tse Hsieh (Kavli IPMU / ISSP, the Univ. of Tokyo)

Jiunn-Wei Chen, Guang-Yu Guo (National Taiwan Univ.)

Hsiang-Nan Li (Academia Sinica)

Venue: National Taiwan University, Taipei, Taiwan

Event Official Language: English

## Math Lecture

### Theory of Operator Algebras (6th)

December 20 at 15:30 - 17:00, 2018

Dr. Yosuke Kubota (Research Scientist, iTHEMS)

Title: An introduction to operator algebras

Abstract: Operators are linear maps from a (usually an infinite dimensional) linear space (most frequently the Hilbert space) to itself, which is like matrices of infinite degree. Operators form an algebra by obvious addition and multiplication. Operators appear in most of the fields in mathematics, in algebra, in geometry, in analysis, ... Some of the key words at the beginning of these lectures are "spectral theory" "operator algebras" "Tomita-Takesaki theory". These lectures are for non-professional people.

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: Japanese

## Symposium

### The 7th International Symposium on Data Assimilation (ISDA2019)

January 21 - 24, 2019

The symposium will focus on the cross-cutting issues shared in broad applications of data assimilation from geoscience to various physical and biological sciences. In particular, the symposium will enhance discussions among researchers with various background on, for example, non-Gaussian and nonlinear data assimilation problems, Big Data Assimilation (BDA), high-performance computation (HPC), Uncertainty Quantification (UQ), advanced intelligence (AI) and machine learning, multi-scale and multi-component treatments, observational issues, and mathematical problems.

Abstract Submission Deadline: October 14, 2018 at 11:59 p.m. UTC

Registration Deadline: December 16, 2018 at 11:59 p.m. UTC

Submission/Registration Fee: Free

Venue: 6F auditorium, Computational Science Research Building, R-CCS, Kobe Campus, RIKEN

Event Official Language: English

# Paper of the Week

## Online Model Parameter Estimation With Ensemble Data Assimilation in the Real Global Atmosphere

2018-10-09

When and where will it rain, and how heavy? – this is a central question that meteorology tries to address. Numerical weather prediction (NWP) is a major approach using data assimilation with mathematical models to predict the weather. The NWP models discretize the earth atmosphere into 3-dimensional grids, and compute the evolution of the atmospheric states based on physical processes (e.g., fluid dynamics, radiation, and water phase changes). The NWP models cannot include subgrid-scale and complex processes explicitly, and these complex phenomena are represented by simplified equations so-called “parameterization”. Parameterization usually contains tunable model parameters, and manual tuning of these parameters is a tedious but important task. This study explores an objective and autonomous approach to optimizing these parameters using data assimilation. We chose a parameter of the subgrid-scale parameterization of raindrop initiation processes of a global NWP model. We successfully mitigated the overproduced precipitation of the NWP model by estimating the model parameter with satellite-observed precipitation data.

Figure: Global precipitation forecasts (mm 6h-1) at 0000 UTC on 16 June 2014 by an NWP model. (left) control experiment with the default model setting, (middle) test experiment with the model parameter estimation, and (right) satellite observation, respectively. Overproduced precipitation over ocean in the control experiment is successfully mitigated by the model parameter estimation.

Reference:

Shunji Kotsuki, Koji Terasaki, Hisashi Yashiro, Hirofumi Tomita, Masaki Satoh, Takemasa Miyoshi

"Online Model Parameter Estimation With Ensemble Data Assimilation in the Real Global Atmosphere: A Case With the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and the Global Satellite Mapping of Precipitation Data"

J. Geophys. Res., 123, 7375-7392 (2018)

doi: 10.1029/2017JD028092

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