I have not seen this of kind of graph before. In general could you explain this graph in terms of what it means to you? Specifically, could you please explain why a deeper isotherm indicates recharge phase and a shallower isotherm indicates discharge phase? Is it because a deeper isotherm signifies a mixed layer (IE under Easterly trade wind La Nina conditions) versus a stratified layer (IE under calmer El Nino conditions)? Thanks, Pamela Gray http://www.cpc.ncep.noaa.gov/products/GODAS/ocean_briefing_new/wwv_n3.gif