Seasonal analysis of cloud characteristics and radiative effect over the Iberian Peninsula using MODIS-CERES observations

We studied the seasonal evolution of clouds in four climatic regions within the Iberian Peninsula during the 2000-2012 period by using satellite data from CERES and MODIS instruments. We analysed cloud cover, cloud optical thickness, cloud-top temperature, and long-and shortwave radiative effect on top of the atmosphere for these four climatic regions. Cloud cover is larger in the north (regions 1 and 4) than in the south (regions 2 and 3) and shows a seasonal behaviour with summer minima for all regions. The maximum cover is found in region 1, with a mean yearly value of 61%. Region 3 shows the minimum cloud cover with an annual average around 43%. Cloud optical thickness ranges between 10 and 22 for low clouds, and between 8 and 20 for high clouds. Moreover, cloud-top temperature for low clouds is 265-285 K and in the range of 240-269 K for high clouds. Shortwave radiative effect is negative and ranging between -50 and -150 W m -2 for low clouds and from -50 to -175 W m -2 for high clouds. Longwave radiative effect is positive and in the range of 5-20 W m -2 for low clouds and around 75 W m -2 for high clouds. Generally, the longwave effect is lower than that for shortwave resulting in a net radiative effect of between 40 W m -2 and -150 W m -2 for low clouds and in the range of 10 -90 W m -2 for high clouds.