# Coupled Spatiotemporal Characterization of Monsoon Cloud Cover and Vegetation Phenology
## 3 Results
### Time Series Comparison of Distinct Spatiotemporal Patterns  
Endmember time series provide temporal information that is complementary to the spatial patterns that are shown above. For the example dataset, we present endmember time series as averages of the pixels within endmember regions that were identified from the temporal feature space in Figure 2 and are outlined in white in Figure 3. We display the median, along with the first and third quartiles, of the annual cycle of each endmember region in order to demonstrate both overall phenology and interannual variability in each distinct endmember region (Figures 4 and 5). Individual years are examined later using the full 17-year time series for these same endmember regions (Figures 6 and 7). Examination of Jabal Al Qara endmember time series (Figure 4) reveals both common behavior and substantial differences among regions. The monsoon dominates all endmembers, with NDVI from mid-June through mid-September consistently below the global mean (thin horizontal lines) for all endmembers, including the Nejd. As explained above, this results from the near-zero NDVI of clouds versus the small but positive NDVI of bare soil, regolith, and NPV. Grasslands in Jabal Al Qara are clearly differentiated from forests on the basis of amplitude and rate of senescence of post-monsoon greenness. Regardless of longitude, forests generally reach higher peak NDVI and take longer to senesce than grasslands. During the monsoon, forests also generally have longer, less interrupted cloud cover than grasslands. Additionally, clear longitudinal signals are present in both forests and grasslands. Greening is observed to be stronger in the west and weaker in the east. It is the combination of the east-to-west and forest-to-grassland gradients that gives the temporal feature space its structure. The forests of Jabal Al Qamar (Figure 5) also demonstrate an east-west gradient in phenological amplitude, but in the opposite direction. The observation that these gradients converge in the unvegetated, high elevation region between the two ranges is interesting, and, to our knowledge, a novel contribution to the biophysical geography of the area. In addition to the longitudinal gradient, both the eastern and western forests of Jabal Al Qamar show prominent but variable early greening. Figures 6 and 7 show the full 17-year time series for spatial averages of each endmember region. The years with obvious data quality issues (2002, 2011, and 2016) are included in these figures to illustrate the character of the dataset. As in Figure 4, the western grasslands of Jabal Al Qara (magenta) are consistently greener longer than the eastern grasslands (cyan). Central grasslands (yellow) generally lie between. Some years show prominent longitudinal differences, while for other years, all three grassland regions behave nearly identically. The longitudinal gradient is even more pronounced for forests than grasslands. Much of the year-to-year variability occurs coherently across the endmember regions. Some years are substantially greener than others in every region, and in some years the greening lasts longer than others (e.g., 2004 vs. 2005). However, in other years, greening occurs in a spatially variable sense and is confined to individual endmembers or subsets of endmembers (e.g., western grasslands are substantially greener in 2009 than 2010, but eastern and central grasslands are not). Additionally, the early parts of 2005, 2007, and 2010 show prominent early greening (or regreening) in the forests of both the ranges. This result was unexpected and, to our knowledge, has not been previously documented. In contrast, time series of the east and west Jabal Al Qamar forests (Figure 7) show prominent differences from the east and west Jabal Al Qara forests. One aspect of this difference is the nature of cloud cover. Persistent cloud cover has substantially shorter duration in Jabal Al Qamar than Jabal Al Qara.