## 3 Results
### Comparison of C5 and C6 CI Products
#### 3.1.3 Temporal Evaluation  
Figure 5 shows the seasonal variations in MODIS C5 and C6 CIs averaged over the Northern Hemisphere (NH, 30-90\({}^{\circ}\)N), Southern Hemisphere (SH, 30-90\({}^{\circ}\)S), and tropics (Trop, 30\({}^{\circ}\)S-30\({}^{\circ}\)N) for different IGBP land cover types. In general, the C5 and C6 CIs show similar seasonal variations in these three latitudinal zones, which is consistent with the regional vegetation phenology [45; 46]. The CIs show opposite seasonal variations over the NH and SH, for both the C5 and C6 CIs, while the variations in the CIs in the Trop are relatively stable. In the NH, the CIs show relatively large values (less clumped) in January, reach a minimum (most clumped) in July, and exhibit relatively large values at the end of the year. In contrast, in the SH, the CIs show relatively small values in January, reach a maximum in June, and fall back to small values in December, except for the croplands that show a slight increase in October. These seasonal variations in the CIs are highly related to regional vegetation phenology, in which low CI values generally arise in the peak growing season with large LAIs and a closed canopy, while high CI values usually appear in the dormant period with lower LAIs and a sparse canopy [47; 100]. The C5 and C6 CIs also show similar values and seasonal variations for different vegetation types, which are associated with the morphology and canopy properties, as well as the growing patterns of different types. For both the C5 and C6 CIs over these three latitude regions, the CIs of evergreen/deciduous needleleaf forests (ENF/DNF) are smallest  
Figure 5: Seasonal variations in the MODIS C5 (**a**,**c**,**e**) and C6 (**b**,**d**,**f**) CIs averaged over the Northern Hemisphere (NH, 30–90\({}^{\circ}\)N), Southern Hemisphere (SH, 30–90\({}^{\circ}\)S), and tropics (Trop, 30\({}^{\circ}\)S-30\({}^{\circ}\)N) for different IGBP land cover types in 2015. The dots indicate variations in the C5 8-day CI and C6 daily CI, while the line with squares denotes variations in the monthly CI. ENF: evergreen needleleaf forests; DNF: deciduous needleleaf forests; EBF: evergreen broadleaf forests; DBF: deciduous broadleaf forests; MF: mixed forests; CSh: closed shrublands; OSh: open shrublands; WSa: woody savannas; Sav: savannas; GL: grasslands; CL: croplands; CVM: cropland/natural vegetation mosaics. (mostly clumped); the CIs of open shrublands (OSh) are largest (least clumped); the CIs of closed shrublands (CSh), grasslands (GL), croplands (CL), and cropland/natural vegetation mosaics (CVM) are relatively high; and the CIs of evergreen/deciduous broadleaf forests (EBF/DBF), woody savanna (WSa), and savanna (Sav) are relatively low. The shoots of coniferous trees enhance the clumping effect of needle leaves compared with other vegetation types with flat, broad leaves; thus, coniferous forests have lower CI values than other land cover types. Land cover types containing trees with high canopies (\(>\)2 m) show smaller CIs than shrubs, crops, and herbaceous vegetation. For seasonal variations, generally, broadleaf forests are more variable than needleleaf forests, and the variations in mixed forests (MF) are in the middle for both versions of the CIs. Most of the coniferous forests (\(\sim\)96%) that were distributed in the NH show relatively smooth seasonal variations in the low needle turnover rate [47; 101]. EBFs are mainly distributed in the Trop (\(\sim\)95%), while DBFs are primarily in the NH (\(\sim\)71%), and broadleaf forests in mid and high latitudes are more variable than those in the Trop due to the more stable climate conditions in the tropics. The seasonal variations in shrubs and savannas are commonly smaller than those in broadleaf forests but larger than those in herbaceous vegetation (i.e., CL and GL).