Lake stratification and temperature profiles simulated using downscaled GCM output

A mathematical in-lake water temperature model (WATEMP-Lake) was developed to investigate future responses of lake stratification and temperature prof iles to future climate change due to rising concentrations of atmospheric g reenhouse gases (GHGs). The model was used to simulate daily water temperat ure profiles and stratification characteristics in summer (June, July, and August -JJA) for Suwa Lake in Japan as a case study. For future assessments , the model uses surface climate variables obtained from a downscaling meth od that was applied to the UK Hadley Centre's coupled ocean/atmosphere mode l forced by combined CO2 and sulphate aerosol changes (HadCM2SUL). The down scaling method employed mean sea level surface pressure to derive three air flow indices identified as: the total shear vorticity (Z) -a measure of cyc lonicity -, the strength of the resultant flow (F), and the overall flow di rection (D). Statistical relationships between these indices and seven dail y meteorological time series were formulated to represent climate variable series at sites around Suwa Lake. These relationships were used to downscal e the observed climatology of 1979-1995 and that of 2080-2099 using HadCM2S UL outputs. (C) 1998 IAWQ Published by Elsevier Science Ltd. All rights res erved.