## Deterministic models assimilating RO

### Global Spectral Model (GSM)

- Spectral model
- Horizontal resolution: TL959 (0.1875°(20 km) Reduced Gaussian Grid)
- Vertical resolution: 100 vertical levels, sigma-p hybrid coordinate, lid at 0.01 hPa

### Meso-scale Model (MSM)

- Grid model
- Horizontal resolution: 5 km
- Vertical resolution: 48+2 layers up to 21.8 km

## Data assimilation method

### Global Analysis (GA)

- 4D-Var, 6-hr data assimilation window, increment resolution TL319 (~55 km)
- Analysis times (T): 00, 06, 12, 18 Z
- Time window: T ± 3 hrs
- Data cut-off time (time after the start of the assimilation window):
- Early analysis: 5 hrs 20 mins
- Cycle analysis: 14 hrs 50 mins (T=00,12), 10 hrs 50mins (T=06,18)

### Meso-scale Analysis (MA)

- 4D-Var, 3-hr data assimilation window, Horizontal resolution of inner model: 15 km
- Analysis times (T): 00, 03, 06, 09, 12, 15, 18, 21 Z
- Time window: (T-3hrs) – T
- Data cut-off time (time after the start of the assimilation window):3hrs50mins

## RO quantity assimilated

### Global Analysis (GA)

- Bending angle
- 1D operator
- Tangent point drift included
- No vertical thinning
- No bias correction applied

### Meso-scale Analysis (MA)

- Refractivity
- 1D operator
- Tangent point drift included
- No vertical thinning
- No bias correction applied

## Observation error characteristics

### Global Analysis (GA)

Observation error depends on impact height only:

- 1% of observed bending angle for h > 10 km,
- linear variation from 20% at h=0 km to 1% at h=10 km,
- lower limit of 3*10^-6 rad

### Meso-scale Analysis (MA)

Observation error depends on geometric height only:

The refractivity errors are calculated using a linear interpolation between these points:

Geometric height (m) | error(%) |

0 | 10.0 |

10000 | 0.5 |

20000 | 0.18 |

30000 | 0.04 |

## Impact

An adjoint sensitivity study has not been conducted yet using the latest JMA global model.