Global climatology of surface water temperatures of large lakes by remote sensing

Lake surface water temperatures ( LSWTs ) of 246 globally distributed large lakes were derived from Along‐Track Scanning Radiometers ( ATSR ) for the period 1991–2011. The climatological cycles of mean LSWT derived from these data quantify on a global scale the responses of large lakes' surface temperatures to the annual cycle of forcing by solar radiation and the ambient meteorological conditions. LSWT cycles reflect the twice annual peak in net solar radiation for lakes between 1°S to 12°N. For lakes without a lake‐mean seasonal ice cover, LSWT extremes exceed air temperatures by 0.5–1.7 °C for maximum and 0.7–1.9 °C for minimum temperature. The summer maximum LSWTs of lakes from 25°S to 35°N show a linear decrease with increasing altitude; −3.76 ± 0.17 °C km −1 ( R a d j 2 = 0.95), marginally lower than the corresponding air temperature decrease with altitude −4.15 ± 0.24 °C km −1 ( R a d j 2 = 0.95). Lake altitude of tropical lakes account for 0.78–0.83 ( R a d j 2 ) of the variation in the March to June LSWT –air temperature differences, with differences decreasing by 1.9 °C as the altitude increases from 500 to 1800 m above sea level (a.s.l.) We define an ‘open water phase’ as the length of time the lake‐mean LSWT remains above 4 °C. There is a strong global correlation between the start and end of the lake‐mean open water phase and the spring and fall 0 °C air temperature transition days, ( R a d j 2 = 0.74 and 0.80, respectively), allowing for a good estimation of timing and length of the open water phase of lakes without LSWT observations. Lake depth, lake altitude and distance from coast further explain some of the inter‐lake variation in the start and end of the open water phase.