How Representative are the ''Alacant and the Valencia Anchor Stations'' Measurements of their Respective Surrounding Meteorology?

The application of the Valencia and the Alacant Anchor Stations to validation activities of low spatial resolution Earth Observation remote sensing missions make it necessary to study the representativity and significance of the actual meteorological stations measurements with respect to the area they represent.

Meteorological simulations carried out with The Atmospheric Pollution Model (TAPM) (Hurley, 2005) carried out for the whole year of 2004 with the temporal resolution of one hour. The spatial resolution is 1 km, covering a total area of 75 x 75 km2. The grid is chosen such that the Anchor Station is placed in the central point, that is, the coordinate (38, 38).

The correlation between the simulated time series for every grid point and the corresponding Anchor Station simulated values is established by means of the Pearson�s correlation coefficient. The following figures show the correlation maps obtained for the parameters analysed, namely, temperature, relative humidity, u and v wind components, and precipitation.

Correlation maps centered at the Valencia Anchor Station relative to the following meteorological parameters: a) temperature, b) relative humidity, c) u wind component, d) v wind component, e) precipitation

A limit has been established in the correlation coefficients for each of the parameters and the zone of influence of the whole station has been taken as the intersection of the zones obtained for each of the parameters. Instead of using five correlation coefficients �one for each parameter- a specific percentile value, namely, 75, 85 95, has been chosen as limiting value for each of the correlation coefficients, thus defining different approximations degrees. The values of the limiting correlation coefficients relative to each meteorological parameter and for each proposed percentile are given in the following Table 1 for both Anchor Stations.

Limiting correlation coefficients for every parameter (temperature, relative humidity, u wind component, v wind component, precipitation) and percentile, respectively for the Valencia and the Alacant Anchor Stations

The graphical representation of the intersection of the areas obtained for each meteorological parameter is given in the followinf figure, where the red area represents the intersection of the zones obtained for each parameter taking as limiting R values those obtained for percentile 95; the yellow area for percentile 85 and the white area for percentile 75. The black area shows lower correlation values.

Demarcation of the Valencia and the Alacant Anchor Stations, respective representative areas with three approximation degrees: the red area represents the intersection of the zones obtained for each parameter taking as limiting R values those obtained for percentile 95; the yellow area for percentile 85 and the white area for percentile 75. The black area shows lower correlation values

[Hurley P. (2005): The Air Pollution Model (TAPM) Version 3. Part 1: Technical Description, CSIRO Atmospheric Research Technical Paper No. 55]