# Sentinel-3A SRAL Global Statistical Assessment and Cross-Calibration with Jason-3

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## Abstract

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## 1. Introduction

## 2. Data and Methods

#### 2.1. Sentinel-3A Data

#### 2.2. Jason-3 Data

#### 2.3. Data Analysis Methods

_{i}is the ith value of parameter a during the given time period. N is the total observation number. a

_{mean}and a

_{SD}are the mean and standard deviation of a.

_{i}and b

_{i}are the ith collocated data of SAR or PLRM mode parameter in the given time period. N is the total number of collocated data pairs. The bias and RMSE are the bias and root mean square error of the differences of parameter a and b.

## 3. Results and Discussion

#### 3.1. Edited Measurements

#### 3.2. Cycle by Cycle Statistical Analyses

#### 3.2.1. Wet Tropospheric Correction

#### 3.2.2. Ionospheric Correction

#### 3.2.3. Sea State Bias (SSB) Correction

#### 3.2.4. Significant Wave Height

#### 3.2.5. Backscattering Coefficient (Sigma0)

#### 3.2.6. Wind Speed

#### 3.2.7. Sea Surface Height

#### 3.3. Comparisons at Self-Crossovers

#### 3.4. Comparisons with Jason-3

#### 3.4.1. Cross-Calibration with Jason-3

#### 3.4.2. Cycle by Cycle Statistical Analysis on Jason-3 Cycle

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**The spatial distribution of self-crossovers of Sentinel-3A (blue) and dual-crossovers between Sentinel-3A and Jason-3 (red).

**Figure 2.**Cycle by cycle percentages of rejected measurement by Sentinel-3A SRAL by the thresholds of (

**a**) number of 20 Hz range measurements, number of 20 Hz Sigma0 measurements and radiometer wet tropospheric correction, and (

**b**) RMS of 20 Hz range measurements, RMS of 20 Hz Sigma0 measurements, dual frequency ionospheric correction, Sigma0 and SWH during cycle 3–41.

**Figure 3.**Cycle by cycle mean of (

**a**) number and (

**b**) RMS of 20 Hz range measurements according to Jason-3 repeat cycles.

**Figure 4.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of wet tropospheric corrections according to Sentinel-3A repeat cycles.

**Figure 5.**Cycle by cycle biases and RMSEs of differences of wet tropospheric correction between SAR and PLRM mode.

**Figure 6.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of ionospheric corrections according to Sentinel-3A repeat cycles.

**Figure 7.**Cycle by cycle biases and RMSEs of differences of dual frequency ionospheric correction between SAR and PLRM mode.

**Figure 8.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of SSB corrections according to Sentinel-3A repeat cycles.

**Figure 9.**Cycle by cycle biases and RMSEs of differences of SSB correction between SAR and PLRM mode.

**Figure 10.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of SWHs according to Sentinel-3A repeat cycles.

**Figure 12.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of backscattering coefficients according to Sentinel-3A repeat cycles.

**Figure 13.**Cycle by cycle biases and RMSEs of differences of backscattering coefficients between SAR and PLRM mode.

**Figure 14.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of wind speeds according to Sentinel-3A repeat cycles.

**Figure 16.**Cycle by cycle (

**a**) means and (

**b**) standard deviations of SLA according to Sentinel-3A repeat cycles.

**Figure 17.**Cycle by cycle biases and standard deviations of SLA differences between SAR and PLRM mode.

**Figure 18.**Cycle by cycle biases and RMSEs of differences of (

**a**) radiometer wet tropospheric correction, (

**b**) dual frequency ionospheric correction, (

**c**) SSB correction, (

**d**) SWH, (

**e**) Sigma0 and (

**f**) wind speed at the self-crossovers of Sentinel-3A

**Figure 19.**Cycle by cycle biases and RMSEs of SAR mode SLA differences at the self-crossovers of Sentinel-3A.

**Figure 21.**Cycle by cycle biases and RMSEs of (

**a**) radiometer wet tropospheric correction, (

**b**) dual frequency ionospheric correction, (

**c**) SSB correction, (

**d**) SWH, (

**e**) backscattering coefficient, and (

**f**) wind speed differences at dual-crossovers between Sentinel-3A and Jason-3 with measurement time difference of 30 min.

**Figure 22.**Cycle by cycle biases and RMSEs of SLA differences at dual-crossovers between Sentinel-3A and Jason-3 with measurement time difference of 30 min.

**Figure 23.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of radiometer wet tropospheric corrections between Sentinel-3A and Jason-3 according to Jason-3 repeat cycles.

**Figure 24.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of dual frequency ionospheric corrections between Sentinel-3A and Jason-3 according to Jason-3 repeat cycles.

**Figure 25.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of SSB corrections between Sentinel-3A and Jason-3 according to Jason-3 repeat cycles.

**Figure 26.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of SWHs between Sentinel-3A and Jason-3 according to Jason-3 repeat cycles.

**Figure 27.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of backscattering coefficients between Sentinel-3A and Jason-3 according to Jason-3 repeat cycles.

**Figure 28.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of wind speeds between Sentinel-3A and Jason-3 with Jason-3 repeat cycles.

**Figure 29.**Comparison of cycle by cycle (

**a**) means and (

**b**) standard deviations of SLAs between Sentinel-3A and Jason-3 with Jason-3 repeat cycles.

Parameter | Ku Band | C Band |
---|---|---|

Frequency | 13.575 GHz | 5.41 GHz |

Bandwidth | 350 MHz | 320 MHz |

Tracking modes | Closed loop and open loop | |

LRM pulse repetition frequency | 1920 Hz | |

SAR mode pulse repetition frequency | 18 kHz | |

SAR along track solution | ~300 m |

**Table 2.**Thresholds used for the main altimeter and radiometer parameters in the Sentinel-3A SRAL data editing procedures.

Parameter | Minimum | Maximum |
---|---|---|

Orbit-Range | −130 m | 100 m |

Sea level Anomaly | −2 m | 2 m |

Number of 20 Hz range measurements | 10 | - |

Standard deviation of 20 Hz range measurements | 0 m | 0.2 m |

Dry tropospheric correction | −2.5 m | −1.9 m |

Wet tropospheric correction | −0.5 m | −0.001 m |

Dual frequency ionosphere correction | −0.4 m | 0.04 m |

Sea state bias correction | −0.5 m | 0 m |

Backscattering coefficient | 5.0 dB | 28.0 dB |

Standard deviation of 20 Hz Sigma0 measurements | 0 dB | 0.7 dB |

Number of 20 Hz Sigma0 measurements | 10 | - |

Significant wave height | 0 m | 11 m |

Wind speed | 0 m/s | 30 m/s |

Ocean tide | −5 m | 5 m |

Solid earth tide | −1 m | 1 m |

Pole tide | −0.15 m | 0.15 m |

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**MDPI and ACS Style**

Yang, J.; Zhang, J.; Wang, C.
Sentinel-3A SRAL Global Statistical Assessment and Cross-Calibration with Jason-3. *Remote Sens.* **2019**, *11*, 1573.
https://doi.org/10.3390/rs11131573

**AMA Style**

Yang J, Zhang J, Wang C.
Sentinel-3A SRAL Global Statistical Assessment and Cross-Calibration with Jason-3. *Remote Sensing*. 2019; 11(13):1573.
https://doi.org/10.3390/rs11131573

**Chicago/Turabian Style**

Yang, Jungang, Jie Zhang, and Changying Wang.
2019. "Sentinel-3A SRAL Global Statistical Assessment and Cross-Calibration with Jason-3" *Remote Sensing* 11, no. 13: 1573.
https://doi.org/10.3390/rs11131573