ENERGY BUDGET MEASUREMENTS USING EDDY-CORRELATION AND BOWEN-RATIO TECHNIQUES AT THE KINOSHEO LAKE TOWER SITE DURING THE NORTHERN WETLANDS STUDY

Fluxes of heat and water vapor were measured on a 20-m tower at Kinosh eo Lake in the Hudson Bay lowlands using eddy correlation and Bowen ra tio energy balance techniques. The study period was June 25 to July 28 , 1990. Measurements were made over a peat bog consisting of a mixture of sphagnum moss and lichen hummocks and black pools. About 200 m wes t of the tower were several shallow ponds. The hummocks had a dry, ins ulating surface and were underlain by an ice layer near 50 cm depth un til mid-July. At the beginning of the period the black pools were cove red with water, and although the free water gradually disappeared over the study period, they remained saturated to the end of July. The dep th of peat near the tower was about 3 m. Despite the ice layer under t he hummocks, their daytime surface temperatures were high, near 35 deg rees C, and after the middle of July, above 40 degrees C. Inspection o f temperature, precipitation, and radiation data showed that the midsu mmer period of 1990 was warmer, drier, and sunnier than usual at Mooso nee and so by inference at Lake Kinosheo. When all the data were combi ned to yield average diurnal energy balance components, the eddy corre lation fluxes accounted for 90% of the available energy. Latent heat f lux averaged 46% of the total available energy and the sensible heat f lux averaged 34%. Daytime Bowen ratios were near 1 for the experimenta l period, suggesting that the bog behaved more like a dryland than a w etland. Eddy correlation measurements of sensible heat and latent heat flux were less than those measured using the Bowen ratio energy balan ce technique, the average ratios being 0.81 and 0.86, respectively. Th ese differences were possibly due to the difficulty in measuring energ y balance components of net radiation and ground heat flux over the mo saic surface.