POA from Scada Vs. Global Incident in Coll. Plane

[emangahallah]

I am trying to compare the the Plane of Array Irradiance (POA) in w/m^2 i get from scada with the Global Incident in Coll. Plane from the PVSyst output
knowing that the meteo file i used in simulation is generated using the scada data imported as a custom file
so as i imported the POA to the PVSyst i expected that the POA should be identical with Global Incident in Coll. Plane
but there is a differences in months starting from may to november 
attached a sample of the issue
can any one explain why is this behaviour

thank you in advance