# Can Data Assimilation Improve Short-Term Prediction of Land Surface Variables?
## 3 Results
### Impacts of Assimilation on Land Surface Variables Prediction
#### 3.1.3 Sensible Heat Flux  
The performance of H from OL and MLDAS with a prediction lead time of 30 days is shown in Figure 4. Table 2 shows the \(NIC_{RMSD}\) of MLDAS and OL prediction in 2003 to 2005. Overall, \(RMSD_{Analysis}\) is decreased compared to \(RMSD_{Model}\) in 10 of the 12 experiments. The result indicates that data assimilation can potentially improve the prediction skill of H in the Noah-MP model. Larger \(NIC_{RMSD}\) can be seen in scenario IV (assimilation of 105 days) with 57.07% in 2003, 47.80% in 2004, and 47.57% in 2005, indicating that a longer assimilation period results in better prediction performance for H. On the contrary, \(NIC_{RMSD}\) is negative in scenario I over 2003 and 2005, revealing that assimilating observations with large uncertainties into the model does not improve the prediction performance, but even degrades it. Details on H prediction in different assimilation scenarios from 2003 to 2005 are given in Figure 4. Considering that there are subtler differences in H prediction between MLDAS \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multicolumn{3}{c}{**2003**} & \multicolumn{3}{c}{**2004**} & \multicolumn{3}{c}{**2005**} \\ \cline{2-9}  & \(RMSD_{Model}\) & \(RMSD_{Analysis}\) & \(NIC_{RMSD}\) & \(RMSD_{Model}\) & \(RMSD_{Analysis}\) & \(NIC_{RMSD}\) & \(RMSD_{Model}\) & \(RMSD_{Analysis}\) & \(NIC_{RMSD}\) \\  & **(W/m\({}^{2}\))** & **(W/m\({}^{2}\))** & **(\%)** & **(W/m\({}^{2}\))** & **(W/m\({}^{2}\))** & **(\%)** & **(W/m\({}^{2}\))** & **(W/m\({}^{2}\))** & **(\%)** \\ \hline
**Scenario I** & 26.716 & 29.411 & \(-\)10.09 & 48.168 & 46.886 & **2.66** & 36.926 & 52.082 & \(-\)41.04 \\ \hline
**Scenario II** & 32.043 & 21.718 & **32.22** & 20.031 & 7.822 & **60.95** & 63.834 & 25.284 & **60.39** \\ \hline
**Scenario III** & 15.021 & 7.552 & **49.72** & 7.961 & 5.210 & **34.56** & 9.853 & 5.745 & **41.70** \\ \hline
**Scenario IV** & 22.453 & 9.640 & **57.07** & 12.422 & 6.484 & **47.80** & 34.707 & 18.198 & **47.57** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: \(NIC_{RMSD}\) of sensible heat fluxes in different assimilation scenarios (I–IV) in 2003, 2004, and 2005. Positive \(NIC_{RMSD}\) numbers are marked in bold. Figure 4: Sensible heat fluxes prediction from OL and MLDAS in 2003–2005. Predictions of four assimilation scenarios are given. Columns represent different assimilation scenarios in each year. The red solid line in each subplot represents MLDAS prediction in one future month; the blue dashed line in each subplot represents OL simulation; and the green hollow scatters represent H benchmarks. and OL compared with SM, H prediction from four scenarios with lead times of 30 days are given to highlight the differences. In general, both MLDAS and OL can fit the benchmarks quite well. In Scenario I, the OL slightly outperformed the MLDAS in prediction, especially in 2003 and 2005. However, for scenarios II-IV, prediction in MLDAS can better capture the variations in benchmarks both in trend and magnitude. Among scenarios II-IV, scenario II (assimilation of 45 days) improves the prediction skill of MLDAS most significantly, which can also be seen from \(NIC_{RMSD}\) in Table 2. Note that H predictions are relatively low with some cases lower than \(-50\) W/m\({}^{2}\) in scenario II-IV. To confirm the accuracy of benchmarks and predictions, raw observations of H from AmeriFlux were checked. There are also several H observations smaller than 0 W/m\({}^{2}\) at this site during the middle of summer, indicating that the benchmarks and predictions are reliable here. Details regarding the observations can be seen at: [[https://ameriflux.lbl.gov/data/download-data/](https://ameriflux.lbl.gov/data/download-data/)]([https://ameriflux.lbl.gov/data/download-data/](https://ameriflux.lbl.gov/data/download-data/)) (accessed on 10 October 2022). There are probably two reasons for this.