Variability of the horizontal gradients of the air and the water surface temperatures in the vernal frontal zone period of Lake Ladoga |
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| Authors: | M A Naumenko V V Guzivaty S G Karetnikov |
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| Institution: | 1. Institute of Limnology, Russian Academy of Sciences, St. Petersburg, Russia
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| Abstract: | Every year, the during springtime heating conditions, the seasonal thermal frontal zone appears in Lake Ladoga. It features high horizontal water temperature gradients. The coastal waters, stably stratified in density, interact with the waters of the open lake that are unstably stratified because of the free convection developing in the temperature range between 0°C and the maximum density of the water at 4°C. In Lake Ladoga, the advance of the vernal frontal zone lasts about 7?C8 weeks from mid-May to the beginning of July. Both the water temperature and air temperature distributions over the water??s surface show that large spatial temperature ranges exist in the vernal front reaching more than 11°C. We investigated the spatial horizontal gradients of the water??s surface and the air temperature using a spatial grid with a resolution of 5 km. The surface water temperature and the air temperature gradients were compared with each other as well as with the temperatures in the region of varying depths. During the spring peak of the frontal activity in Lake Ladoga, most of the fronts feature mean temperatures greater than 4°C. This indicates that the thermal bar marks the offshore edge of the most extensive frontal zone. |
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