Shelters used to protect air temperature sensors from solar radiation induce a measurement error. This work presents a semi-empirical model based on meteorological variables to evaluate this error. The model equation is based on the analytical solution of a simplified energy balance performed on a naturally ventilated shelter. Two main physical error causes are identified from this equation: one is due to the shelter response time and the other is due to its solar radiation sensitivity. A shelter intercomparison measurement campaign performed by the World Meteorological Organization (WMO) is used to perform a non-linear regression of the model coefficients. The regression coefficient values obtained for each shelter are found to be consistent with their expected physical behavior. They are then used to simply classify shelters according to their response time and radiation sensitivity characteristics. Finally, the ability of the model to estimate the temperature error within a given shelter is assessed and compared to the one of two existing models (proposed by Cheng and by Nakamura). For low-response-time shelters, our results reduce the root mean square error by about 15% (0.07 K) on average when compared with other compensation schemes.

The greening of cities has become a major component of current urban development policies. This greening is taking new and variable forms, and is increasingly associated with rainwater management techniques. This increase in vegetated surfaces can potentially encourage evapotranspiration. Increasing this process has a twofold advantage. On the one hand, It provides stormwater runoff reduction benefits and, on the other, it promotes cooling in the urban environment. However, in order to better quantify and optimise evapotranspiration, it is necessary to be able to measure it for different kind of urban surfaces. In an urban environment, where surfaces are very heterogeneous, it is therefore necessary to have continuous measurements, over the long term (several seasons) and, if possible, on different types of surfaces with relatively small areas: just a few dozen m². In order to verify whether Eddy Covariance measurements can be adapted to these singular surfaces, measurements were carried out on a green roof (situated in Broué (28), France) covering an area of approximately 1900 m² (16.5 m x 115 m) during the summers of 2022 and 2023. Two measurement systems were used (an IRGASON from Campbell Scientific and a Gill WindMaster associated with a LI-COR LI-7500). In an attempt to limit the footprint to the roof surface, the instruments were placed at a height of 50cm above the roof surface. In addition to these measurements, the energy balance was monitored and complementary measurements were made using a transpiration chamber. The latent heat flux measurements obtained by EC indicate fluxes generally below 150 W.m2, which represents between 10 and 45% of the net radiation depending on the soil water content. Comparison with the transpiration chamber shows that the latter underestimates the fluxes compared with the EC measurement. However, the final objective is to determine whether measurements at such a low height are realistic and can limit the footprint at the roof surface, spectral analyses of these measurements and footprints are currently being studied.