## 3 Evaluations of Data Quality
The differences in the window channels are relatively more significant, especially for FY-3F MWTS channel 2, which is close to 0.3 K.  
According to previous research results, MWTS has shown good performance in reducing striping noise [28; 29]. To further investigate whether the MWHS and MWTS carried by FY-3F also possess this characteristic of reducing striping noise, data from a randomly selected day near the equator were used to validate this by calculating the Striping Index (SI). The severity of striping noise can be quantified using SI [30], and it can also be used to measure the uniformity of brightness temperature [28]. The single channel calculation method for SI is given by the following formulas:  
\[\mathrm{SI}=\frac{\sum\limits_{k=1}^{K}\frac{1}{N_{i}}\sum\limits_{j=1}^{N} \sigma_{\mathrm{along}}^{2}(k,i)}{\sum\limits_{k=1}^{K}\frac{1}{M_{j}}\sum \limits_{j=1}^{M}\sigma_{\mathrm{cross}}^{2}(k,i)} \tag{3}\]  
\[\sigma_{\mathrm{along}}^{2}(k,i)=\frac{1}{M_{j}}\sum\limits_{j=1}^{M}\left( \left(\mathrm{O-B}\right)_{k,i,j}-\left(\overline{\mathrm{O-B}}\right)_{k,i,j} \right)^{2} \tag{4}\]  
\[\left(\overline{\mathrm{O-B}}\right)_{k,i,j}=\frac{1}{M_{j}}\sum\limits_{j=1}^ {M}\left(\mathrm{O-B}\right)_{k,i,j} \tag{5}\]  
\[\sigma_{\mathrm{cross}}^{2}(k,i)=\frac{1}{N_{i}}\sum\limits_{j=1}^{N}\left( \left(\mathrm{O-B}\right)_{k,i,j}-\left(\overline{\mathrm{O-B}}\right)_{k,i,j} \right)^{2} \tag{6}\]  
Figure 6: Comparison of O-B bias (**a**) and standard deviation bias (**b**) for the FY-3F MWTS (black) and FY-3E MWTS (grey) equivalent channel ascending (Asc) and descending (Desc) orbits (units: K). \[(\overline{\mathrm{O-B}})_{\mathrm{k,i,j}}=\frac{1}{\mathrm{N}}\sum_{i=1}^{ \mathrm{N}}{(\mathrm{O-B})_{\mathrm{k,i,j}}} \tag{7}\]  
In the above formulas, \(\sigma_{\mathrm{along}}^{2}\) and \(\sigma_{\mathrm{cross}}^{2}\) represent the variances in the along-track and cross-track directions, respectively. \((\mathrm{O-B})_{\mathrm{k,i,j}}\) denotes the \(\mathrm{O-B}\) for the i-th FOV on the j-th scan line within the k-th data sample. K represents the total number of data samples, M is the number of scan lines used for variance calculation within each sample, and N is the number of FOV within each sample. In the calculation, M = 20, N = 98, and K = 14. Figure 7 displays the SI for each channel of the MWHS and MWTS on FY-3F and FY-3E. The black bars represent FY-3F, while the gray bars represent FY-3E. There are no significant differences in the SI for all channels of the MWHS between the two satellites. In MWHS channels 1-4, the SI of FY-3F is an average 0.05 higher than that of FY-3E, while in the remaining channels, FY-3F is lower than FY-3E. For MWTS, the SI differences between the two satellites are more pronounced in channels 7-13. Specifically, the SI of FY-3F's channels 7-9 is averagely about 0.2 higher than that of FY-3E, while the SI of FY-3E's channels 10-13 is about 0.3 higher than that of FY-3F, with channels 11 and 12 being particularly notable, with FY-3E being about 0.4 and 0.5 higher, respectively. Overall, the striping noise of FY-3E MWHS is about 0.007 higher than that of FY-3F MWHS, and the FY-3E MWTS is about 0.3 higher than that of FY-3F MWTS. The SI of both MWHS and MWTS channels is around or within 1, indicating good performance.