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

Zusammenfassung

We studied the seasonal evolution of clouds in four climatic regions within the Iberian Peninsuladuring the 2000-2012 period by using satellite data from CERES and MODIS instruments. Weanalysed cloud cover, cloud optical thickness, cloud-top temperature, and long- and shortwaveradiative effect on top of the atmosphere for these four climatic regions. Cloud cover is larger inthe north (regions 1 and 4) than in the south (regions 2 and 3) and shows a seasonal behaviourwith summer minima for all regions. The maximum cover is found in region 1, with a meanyearly value of 61%. Region 3 shows the minimum cloud cover with an annual average around43%. Cloud optical thickness ranges between 10 and 22 for low clouds, and between 8 and 20for high clouds. Moreover, cloud-top temperature for low clouds is 265-285 K and in the rangeof 240-269 K for high clouds. Shortwave radiative effect is negative and ranging between−50and−150Wm−2for low clouds and from−50to−175Wm−2for high clouds. Longwaveradiative effect is positive and in the range of 5-20Wm−2for low clouds and around 75Wm−2for high clouds. Generally, the longwave effect is lower than that for shortwave resulting in anet radiative effect of between 40Wm−2and−150Wm−2for low clouds and in the range of10 - 90Wm−2for high clouds.Key words:cloud optical thickness, cloud cover, radiative effect, CERES, MODIS