private function instantiateEntity($entity_name)
    {
        $entity = null;

        if ($entity_name == 'weatherPhenomenons') {
            $entity = new WeatherPhenomenon();
        } else if ($entity_name == 'maxTemperature') {
            $entity =  new Temperature();
        } else if ($entity_name == 'minTemperature') {
            $entity = new Temperature();
        } else if ($entity_name == 'clouds') {
            $entity = new CloudLayer();
        } else if ($entity_name == 'surfaceWind') {
            $entity = new SurfaceWind();
        } else if ($entity_name = 'visibility') {
            $entity = new Visibility();
        }

        return $entity;
    }