## 3 Results and Discussion  
Figure 2 shows the temporal plots of dekadal NDVI climatology and the corresponding Kcp and Kc for two locations with a high proportion of herbaceous cover (potential crop pixels). The major difference between NDVI_1 and NDVI_2 profiles is that NDVI_1 contains a higher proportion of tree (T) cover (27%) and lower bare (B) cover (1%), while NDVI_2 contains a higher proportion of bare (21%) and lower tree (2%) covers. The herbaceous (H) component is comparable on both: 72% and 77% for NDVI_1 and NDVI_2, respectively. Also, NDVI_1 is located in northern Illinois with a \"B1\" marker, while NDVI_2 is located in northwestern Dakota (\"B21\") (Figure 4). The numbers in the location marker such as \"B1\" and \"B21\" refer to the bare cover percentages. Both locations showed a comparable start of season by crossing the 0.3 NDVI threshold around dekad 12 (20-30 April). The overall seasonal pattern is comparable in that both experience their peak NDVI in the time period between dekad 19 and dekad 23. However, NDVI_1 shows a higher magnitude during the peak  
Figure 3: Temporal profile of AVHRR NDVI climatology, corresponding Kcp, and control Kc profiles for two noncropland locations with different proportion of bare (B), herbaceous (H), and tree (T) cover percentages. NDVI_3: B = 0%, H = 62%, T = 38; NDVI_4: B = 42%, H= 58%, T=0%. season while NDVI_2 shows a higher magnitude during the early and late season. Also, NDVI_1 crosses back the 0.3 NDVI threshold about 2 dekads earlier than NDVI_2 toward the end of season. The corresponding Kcp patterns for NDVI_1 and NDVI_2 are shown as Kcp_1 and Kcp_2. The transformation of NDVI into Kcp patterns involves changes both in magnitude and temporal patterns. For example, in terms of peak magnitude, NDVI_1 is higher than NDVI_2. But the peak magnitude is about the same for Kcp_1 and Kcp_2 mostly because the assumption of cereal crops being grown on both locations with comparable ground cover will result in a comparable peak water-use coefficient under unlimited soil water condition. Temporally, the differences between NDVI and Kcp patterns are more pronounced during early and late seasons. On the other hand, during the dormant stages of the crops (before start of season and after end of season), the Kcp values are held constant to a minimum threshold value of 0.3. The NDVI patterns of the two locations are also close to each other during this period, unlike the peak season. From Figure 2 it can be shown that NDVI_1 will be transformed into a crop water-use pattern (Kcp_1) characterized by a steep increase and decrease in water-use before and after the peak-season, respectively. On the other hand, NDVI_2 will be transformed into a water-use pattern (Kcp_2) characterized by a longer season with a gradual increase and decrease in water use before and after the peak growing season. The actual water use in each case will depend on the atmospheric demand (reference ET) and availability of soil moisture in the area, as shown in Equation 1.  
A plot of a typical Kc profile for a cereal crop with a 170-day growing season shows that Kcp_1 closely matches with the Kc curve, indicating that the use of published Kc values will work well for this location. However, the use of a published Kc profile will not represent well the Kcp_2, which will potentially underestimate the overall vegetation water use in this example. Figure 3 shows the temporal plots of dekadal NDVI climatology and the corresponding Kcp for two other locations with a relatively high proportion of tree cover (0%, 62%, 38% for bare (B), herbaceous (H), and tree (T), respectively) for NDVI_3 and a high proportion of bare areas (42%, 58%, 0% for B, H, T covers, respectively) for NDVI_4. The conversion from NDVI LSP to Kcp has a different effect on the two cover types, especially when compared to the traditional Kc-based water-use pattern.