### 1. Summary of the processing

^{*1}

Removal of the data noise level

Removal of low coherence data

Removal of shadow area data

Removal of the speckle noise

Bias correction

^{*2}

Correction of false velocity unfolding

^{*3}

Reduction processing of the second-trip echo

horizontal / vertical grid interval: 1km

*2：Bias correction is applied only to the cruise during which the receiver trouble occurred.

*3：Correction of false velocity unfolding is not applied to single-PRF observation.

### 2. Details of filter processing

#### 2.1 Removal of the noise level data (IRIS Programmer's Manual, 2010; Katsumata et al., 2008)

*Z*min is the threshold reflectivity to be obtained (in dB);

*r*is the range distance in km;

*Z*min(1km) is the threshold reflectivity at the range distance of 1km (in dB);

*C*

*gas*is the gaseous attenuation coefficient (dB/km).

*Z*min(1km) and

*C*

*gas*are taken from the dataset in IRIS/Open RAW format.

#### 2.2 Removal of Low coherence data

We adopt 0.3 as the SQI and remove the data with the value less than 0.3.

Before the MR01-K05 cruise, RVP7 was not installed. Therefore, the correction using SQI is not carried out.

See “IRIS Programmer's Manual, 2010” for detailed correction method.

#### Removal of Shadow area data (Katsumata et al., 2008)

The data in these shadows are removed by referring to look-up tables. The look-up tables are constructed statistically from the observational data. To simplify, we assume the shadow depends only on the azimuth and elevation, not on range distance, because all obstacles existed only in the vicinity of the radars.

In case of the MIRAI, the data in the azimuths with an anomaly of the averaged reflectivity of less than ‒3 dB (i.e., half power) are removed as the shadow direction.

#### 2.4 Removal of the speckle noise

#### 2.5 Correction of false velocity unfolding (Katsumata et al., 2005)

* The unfolding is not carried out for the single-PRF observation.

#### 2.6 Reduction processing of the second-trip echo (Katsumata et al., 2005)

#### 2.7 Conversion from polar coordinate system to rectangular coordinate system

The weighted value is expressed in the following expressions.

*d*: Distance from the interpolation point

*W*(

*d*) : Weighted coefficient of the data which separated only distance (d) from the interpolation point

*H*: Half bandwidth

#### 2.8 Addition of the latitude and longitude information

The conversion from the grid position (X, Y) in the rectangular coordinate system to the latitude and longitude is made with the Lambert azimuthal equal-area projection method (Nakatsuka, 2006).

In this case, the earth is supposed to be GRS80 ellipse.

### 3. References

Katsumata, M., T. Ushiyama, K. Yoneyama, and Y. Fujiyoshi 2008 : Correction of Radar Reflectivity Using TRMM and Distrometer, SOLA, 4, 101-104

Nakatsuka, T., 2006 : Library Software for Geophysical Data Processing and Representation (2), GSJ Open-File Report, no.442

IRIS Programmer’s Manual, 2010 : ftp://ftp.sigmet.com/outgoing/manuals/program/3data.pdf

RVP7 User's Manual, 2003 : ftp://ftp.signet.com/outgoing/manuals/rvp7user/5algor.pdf