## 3 Results  
### Spatiotemporal Consistency of Winter Wheat Planted and Harvested Areas from 2008-2018  
At the national scale, the NASS winter wheat planted and harvested areas had three phases of changes in the study period: (1) a decrease phase from 2008-2010, (2) an increase phase from 2010-2013, and (3) a decrease phase from 2013-2018 (Figure 1(a)). The CDL winter wheat planted area had similar three-phase dynamics similar to the NASS planted area (Figure 1(a)). The disagreements between the NASS planted area and CDL planted area were relatively small for most of the years (<10%). We calculated the anomaly for the mean values of 2008-2018, and the planted area from both NASS and CDL datasets showed a significant decrease from 2013 (Figure 1(b)). The NASS harvested area had a similar change pattern to the planted area but with different magnitudes over the years (Figure 1(b)). At the county scale, for all the counties with winter wheat planted areages from both NASS and CDL datasets in the period of 2008-2018, winter wheat planted areas calculated from the CDL were highly consistent with those from the NASS's officially reported dataset (R\({}^{2}\) = 0.98, \(p\) < 0.001) (Figure 2(a)). There are relatively small interannual variations in the slope values (<10%) and R\({}^{2}\) values among the individual years (Table 1). In many counties, winter wheat harvested areas were much smaller than winter wheat planted areas (Figure 2(b),c). Most of those counties with a large discrepancy between winter wheat planted area and harvested area were distributed in the Southern Great Plains and California, where some winter wheat fields were used as cool-season forage for beef cattle production (grazing or having). At the county scale, the interannual trends of winter wheat planted areas from 2008-2018 were calculated (Figure 4). As the NASS dataset has missing data in each year for various counties, only 626 counties were included (Figure 3(b),d). According to the CDL dataset, 2168 counties had a loss of winter wheat planted area and 998 counties had a gain of winter wheat planted area (Figure 3(a)). There was a geographic shift of winter wheat plant area, as shown by the loss and gain of winter wheat planted area at the county scale (Figure 3(a)). Many counties in Kansas and the Northern Great Plains (in particular, South Dakota) had large losses of winter wheat planted area (Figure 3(a)). In comparison,many counties in Oklahoma, Texas, and several other midwest states had moderate to large gains of winter wheat planted area (Figure 4a). For most states, there is a reasonable spatial agreement of loss and gain of winter wheat planted area between the NASS and CDL datasets, however, in Oklahoma and Texas, there are noticeable differences between these two datasets (Figure 4a,b). A number of counties in Oklahoma and Texas had losses of winter wheat planted area according to the NASS dataset but gains of winter wheat area according to the CDL dataset. This discrepancy could be related to the imprecise estimates of winter wheat area from the CDL dataset because of image spatial resolution, misclassifications, and misalignment of field boundaries ([PERSON] et al., 2018). For all the counties with winter wheat grain production, from planted and harvested area data from 2008-2018, grain production had noticeably stronger relationships with harvested areas than with planted area (Figure 5) due to part of the planted averages being used for grazing and hay. Table 2 lists the statistics of the linear regression models (slope, R\({}^{2}\), and RMSE) between grain production and cropping areas in the period of 2008-2018, and the poorest relationship occurred in the spring drought year of 2014.