# Evaluation of the Urban Weather Generator on the City of Toulouse (France)
## 3 Experimental Results
### Analysis of UWG Performances on UHI Days  
We now analyze UWG performances on simulated air temperatures during the two pairs of days submitted to UHI. To this end, we have depicted in Figure 11 the simulated vs. measured air temperatures at Carmes station. The blue line corresponds to the ideal situation where \(\dot{T}=T\) and enables us to indicate how far/close from the measurements our simulations are. We also represent each point in a different color according to the simulation hour to highlight behaviors correlated to the period of the day. This figure shows that the simulations overestimate air temperatures rather in the middle of the night until early morning (left part of the figure where points correspond to the morning and are up to the blue line) while they underestimate them in the afternoon (right part of the figure where points correspond to the afternoon and are below the blue line). To evaluate the most relevant/irrelevant simulations, the standardized residuals (see Section 2.3.3) are depicted in Figure 12 in the function of simulated air temperatures. A similar color in the function of the hour of the day has been used. As previously mentioned, a value higher than 3 (i.e., 3 times the standard deviation which has been normalized to 1) indicates a too-large error that can be considered as an outlier. It is interesting to note that no outliers have been simulated in this case (which is a good property). However, two groups can be identified on this figure depending on the time of simulation:  
* Late night and morning hours (from midnight to 9 a.m.) have negative standardized residuals and low simulated air temperatures. In this situation, air temperatures are overestimated by UWG;
* Afternoon and evening hours (from 10 a.m. to 8 p.m.) have positive standardized residuals and high simulated air temperatures. In this situation, air temperatures are underestimated by UWG during the daytime. These observations are consistent with Figure 11 but the standardized residual analysis enables guaranteeing that UWG simulates relatively consistent air temperatures without outliers. Figure 9: Standard deviation of the elementary effects vs. overall sensitivity measure (the average of the absolute value of the elementary effects). Figure 10: **Air temperatures simulations for August 2020, 5 th–6 th (left) and 19 th–20 th (right) at** Carmes station using Centre equestre rural station. Each subfigure represents 10 simulations when a single specific parameter is varied to illustrate its influence on the output. The lightest (resp. darkest) line corresponds to a simulation with the lowest (resp. highest) value of the associated parameter. (**a**) Temporal evolution of the Air temperature for different **reference heights** -100 m, 200 m- (differences between simulations \(max=5.23\) \({}^{\circ}\)C, \(mean=0.45\)\({}^{\circ}\)C). (**b**) Temporal evolution of the Air temperature for different **reference heights** -100 m, 200 m- (differences between simulations \(max=3.4\)\({}^{\circ}\)C, \(mean=0.25\)\({}^{\circ}\)C). (**c**) Temporal evolution of the Air temperature for different **nighttime urban boundary layer heights** -30 m, 100 m- (differences between simulations: \(max=5.5\)\({}^{\circ}\)C, \(mean=0.76\)\({}^{\circ}\)C). (**d**) Temporal evolution of the Air temperature for different **nighttime urban boundary layer heights** -30 m, 100 m- (differences between simulations: \(max=3.3\)\({}^{\circ}\)C, \(mean=0.18\)\({}^{\circ}\)C). (**e**) Temporal evolution of the Air temperature for different **building densities** -0.1, 0.8- (differences between simulations: \(max=5.6\)\({}^{\circ}\)C, \(mean=0.87\)\({}^{\circ}\)C). (**f**) Temporal evolution of the Air temperature for different **building densities** -0.1, 0.8- (differences between simulations: \(max=3.8\)\({}^{\circ}\)C, \(mean=0.47\)\({}^{\circ}\)C). (**g**) Temporal evolution of the Air temperature for different **facade lengths** -4 m, 4270 m- (differences between simulations: \(max=0.9\)\({}^{\circ}\)C, \(mean=0.16\)\({}^{\circ}\)C).