## 3 Results  
### Influences of Meteorological Parameters (Temperature, Atmospheric Pressure, Rainfall)  
For such long-term monitoring periods, getting a representative view of the evolution of external parameters is important. In a temperate climate, soil properties--specifically water content and temperature--can have an influence on soil-gas dynamics, especially considering the geology of surface formations (mainly detrital rocks with high clay content). Estimating the relative influence of one parameter to the other on the soil gas concentration and/or the flux and their evolutions through time, is not straightforward using the existing database. Some characteristics can nevertheless be highlighted using the dataset.  
Figure 2 presents the temperature, pressure and soil water content evolutions during the 8 years of monitoring as monitored at each point during field acquisitions. The right insert details the atmospheric temperature data from Pau-Uzein airport, the data from the Barasol probe and the temperatures measured during sampling in the soil. As the thermal state of the atmosphere influences soil temperature, especially in the present case where soil temperatures were measured at shallow depth, the soil temperatures should be lower during winter than during summer, as shown by the whisker data. \"Low season\" soil temperatures mainly fall in a narrow range from 8.3 to 9.4 \({}^{\circ}\)C mean value. However, colder climatic conditions during the field surveys can cause strong temperature decreases in soil, as in March 2010 (mean value 4.3 \({}^{\circ}\)C); \"Indian summer\" conditions, on the contrary, can lead to soil temperatures over 10 \({}^{\circ}\)C, as in December 2012 (mean value 10.7 \({}^{\circ}\)C) and in December 2014 (mean value 10.3 \({}^{\circ}\)C). Annual climatic variations linked to the local conditions (temperate climate with oceanic influence), are thus reflected in the database, with statistically lower temperatures during winter, but these long-term trends can be overlapped by variations of higher frequency. These variations are partly linked to the geographical location of each monitoring point (e.g., hill slope oriented north and covered by trees vs. southwest oriented glade) and the time the measurements are performed.  
During the 2008 to 2015 period, the mean atmospheric pressure was very close to 1015 hPa (calculated value: 1017 \(\pm\) 8 hPa). The variability is higher during winter as a result of more frequent low-pressure events. Information from the pressure sensor of the Barasol probe is similar to that measured in the atmosphere (mean value close to 1021 \(\pm\) 8 hPa).  
Rainfall amounts and their derivate the soil-water contents were variable one year to the other (Figure 2). Generally, strong events occur in November (2009,2010,2013) with monthly amounts greater than 200 mm, but thunderstorms may lead to even larger amounts at other times, such as \(>\)250 mm in May 2013. The rainfall regime is variable because of the location of the study area, near the Pyrenees Mountains to the south and not far from the sea in the west. The result is that the general rule of winter being wetter than summer is not always true here. If \"low season\" monitoring pointed to water contents varying between 30 and 40%, similar values were measured in June 2009 or June 2011. However, soil-water content was generally low after summer and below 20% in September.