# The Combined ASTER MODIS Emissivity over Land (CAMEL) Part 2: Uncertainty and Validation
## 4 Validation with Laboratory Spectra
### RTTOV IASI Brightness Temperature Calculations
#### 4.3.2 Results
Figure 9: Nighttime RTTOV calculated minus observed IASI BT biases (**top panels**) for a constant 0.98 emissivity (black) and the CAMEL emissivity dataset (red) with associated mean emissivity spectra (**bottom panels**) for 29 September 2008 for the (**a**) evergreen broad-leaf forest; (**b**) cropland; (**c**) grassland; (**d**) savanna; (**e**) open shrub; and (**f**) barren/desert land IGBP categories. De-biased variances (explanation in text) are used as the better emissivity estimate and are shown in figures. The number of samples, N, are listed in figure legends. Note that the bottom panel \(y\)-axis limits change for the desert/barren land category. The last spectral region assessed, the 10-13 \(\upmu\)m region, does not show an obvious improvement with the use of the CAMEL. For the average of the four case days, more land classifications show an increase, rather than a decrease, in the CAMEL de-biased variances. Improvement is seen, however, in the barren/desert land and open shrub categories, with the average CAMEL variances being 52% and 80% of the 0.98 variance respectively. The deciduous needle forest and mixed forest categories have the largest average increases of 10-13 CAMEL de-biased variances with respect to the 0.98 values, with 15% being the largest increase. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**IGBP Category** & **15 January 2008** & **14 April 2008** & **15 July 2008** & **29 September 2008** \\ \hline  & **0.98** & **CAMEL** & **0.98** & **CAMEL** & **0.98** & **CAMEL** & **0.98** & **CAMEL** \\ \hline
1: Evergreen Needle Forests & 3.48 & 3.48 & 1.35 & 1.45 & 3.48 & 3.38 & 2.89 & 2.86 \\
2: Evergreen Broad Forests & 5.21 & 4.95 & 5.76 & 5.49 & 6.19 & 5.81 & 2.33 & 2.14 \\
3: Deciduous Needle Forests & 1.98 & 1.98 & 5.99 & 6.02 & 7.91 & 7.49 & 1.31 & 1.29 \\
4: Deciduous Broad Forests & 2.22 & 2.23 & 1.92 & 2.06 & 3.03 & 2.84 & 4.37 & 4.44 \\
5: Mixed Forests & 1.97 & 1.96 & 1.24 & 1.3 & 5.34 & 4.96 & 2.73 & 2.64 \\
6: Closed Shrubs & 2.27 & 1.98 & 3.61 & 3.57 & 3.62 & 3.2 & 2.87 & 2.41 \\
7: Open Shrubs & 4.8 & 2.57 & 4.16 & 1.48 & 4.83 & 1.89 & 4.31 & 1.62 \\
8: Woody Savanna & 3.01 & 2.88 & 3.92 & 3.59 & 4.67 & 4.21 & 3.08 & 2.67 \\
9: Savanna & 3.76 & 2.93 & 3.77 & 3.11 & 4.68 & 3.75 & 2.18 & 1.52 \\
10: Grassland & 2.85 & 2.34 & 2.9 & 2.17 & 2.56 & 1.92 & 2.26 & 1.63 \\
11: wetland & 1.83 & 1.84 & 1.24 & 1.3 & 3.63 & 3.4 & 2 & 1.78 \\
12: Cropland & 2.71 & 2.51 & 2.19 & 1.81 & 3.47 & 3.12 & 2.84 & 2.61 \\
13: Urban Area & 2.67 & 2.68 & 1.77 & 1.9 & 4.39 & 4.22 & 3.78 & 3.71 \\
14: Crop Mosaic & 3.34 & 3.15 & 2.62 & 2.45 & 3.9 & 3.55 & 3.1 & 2.75 \\
15: Antarctic/Permanent Snow & 1.25 & 1.3 & 1.16 & 1.2 & 1.46 & 1.45 & 1.57 & 1.72 \\
16: Barren/Desert & 6.96 & 2.28 & 13.4 & 2.16 & 10.3 & 2.62 & 14.2 & 1.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Variance over the 8–9 \(\upmu\)m region of de-biased IASI calculated minus observed BTs are averaged by IGBP land classification categories for four focus days and shown below in units of Kelvin for nighttime cases. De-biased variances for BTs calculated using a constant 0.98 emissivity and the CAMEL HSR emissivity module are shown. The corresponding number of samples are shown in Figure 10.  
Figure 10: Number of samples for de-biased variances listed in Table 4.