Multi-temporal assessment of bio-physical parameters in lakes Garda and Trasimeno from MODIS and MERIS

Lake surface temperature (LST) reflects meteorological and climatological forcing more than any other physical lake parameter. LST is also strongly related to the mean temperature of the upper stratum which plays an important role in lake's biology depending, among other factors, on the dynamics of phytoplankton and thence of chlorophyll-a concentrations (chl-a). Satellite remote sensing is a valuable tool to study these two bio-physical parameters by providing synoptically data at spatial/temporal resolutions not achievable with traditional techniques. In this study MODIS and MERIS data are used to assess LST and chl-a concentration in two important Italian lakes. I mages data of Lake Garda in the time range from 2004 to 2009 and of Lake Trasimeno from 2005 to 2008 were used. The complexities of processes dealing with lacustrine ecosystems is reflected by the weak of correlation found between chl-a and LST in both lakes by using the entire dataset. However, by considering the time of the year with highest biological activity (i.e. from the end of spring to mid of summer) a positive correlation (r>0.5) was found between the two parameters in Lake Trasimeno. This behaviour was also observed in Lake Garda by considering LST and chl-a data from different areas. In particular the shallower south-east basin of Lake Garda was characterised by higher LST and chl-a concentrations.