Ground based in situ observations of nephelometer at Madrid (CIEMAT) (ES0021U). These measurements are gathered as a part of the following projects ACTRIS and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: aerosol_light_backscattering_coefficient in pm10, aerosol_light_backscattering_coefficient in pm10, aerosol_light_backscattering_coefficient in pm10, aerosol_light_scattering_coefficient in pm10, aerosol_light_scattering_coefficient in pm10, aerosol_light_scattering_coefficient in pm10