| Long-term hydrometeorological conditions of Lake Biwa measured by a telemeter buoy system |
| Shuichi ENDOH, Yasuaki OKUMURA, Kosuke FUJITA, Shinnosuke KAWAKAMI, Junji TANAKA and Seiko KANAZAWA |
| Japanese Journal of Limnology, 71-3, 255-267, 2010 |
| Meteorological and hydrological measurements have been continuously carried
out in Lake Biwa using the telemeter buoy system. Our buoy was set up in
the southern part of the north basin where the water depth was 70 m. The
buoy has sensors of wind speed and direction, atmospheric pressure, temperature
and solar radiation on its top, and sensors of water current, electrical
conductivity, turbidity and water temperature (8 layers) below the water
surface. Observed data were immediately transmitted by e-mail from the
buoy to Shiga University using the NTTDOPA system. The daily range of atmospheric temperature on the lake was as small as 4.3 oC in annual average compared to 7.3 oC on shore. Wind speed at about 4 m above the lake surface was roughly twice that on shore. Water current velocity was around 5 cm sec-1 in winter, and gradually increased to 15 cm sec-1 in summer due to the development of the geostrophic gyre. The heat budget at the lake surface was strongly controlled by shortwave and longwave radiations, while the heat loss by evaporation is effective from summer to winter. Using the buoy s data, surface evaporation was calculated to be 504 mm yr-1. |