THERMAL LENSES AND INTERNAL SOLITONS IN CHAPAIA LAKE, MEXICO.pdf

Vol. 17 No. 4 CHIN. J. OCEANOL. LIMNOL. 1999 THERMAL LENSES AND INTERNAL SOLITONS IN CHAPAIA LAKE, MEXICO Filonov, A. E. , Tereshehenko, I. E. (Phy~/cs/)epazwa~, UnitmsityofGuadalajaraApdo. Poad 4L079, G,,~h/ajam, 44421, Jal., M~.oo) Received May 12, 1998; revision accepted Dec. 3, 1998 Instrumental measurements of the circulation and thermic regimen of tropical Ompah Lake revealed the surface temperature variatiom in its eastern part. In all of the cress-sections, spatial variations Of 3~ were ordinarily registered over a distance of just 100- 300 m. The movements of the in- ternal thermal front in the water body with 2~ fluctuation were registered at a buoy station. The front s forepart was a c ~ e d by intemive internal waves in the form of internal KdeV solitons. The front near the buoy station was formed by the movement of the warm water body coming from the eastern shallow part of the lake and stimulated by the morning breeze. Key words: Chapah Lake (Mexico), temperature and current measurements, thermal fronts, in- ternal solitom INTRODUCTION The largest lake in Mexico and third largest in Latin America, Chapala Lake (approximately 20~ is 1500 m above sea level, measures 75 x 25 km, has average depth of 6 m (maximum depth close to 11 m) and a mountain chain along its northern and southern shores (Fig. l a ) . The Lerma River flows into it; the Santiago River flows out of it. The beautiful landscape, and warm cli- mate conducive to breeze circulation along its shore; absence of abrupt temporature variations, and the moderate air humidity attract many tourists to the lake. Many retirees from Canada and the Unit- ed States, for whom the climate is curative, live in the small town of Ajijic in the northwestern re- gion of the lake. Unfortunately, during the past decades, the lake water has become polluted with anthropogenic agents, which enter the lake through discharges from the Lemaa River and neighboring areas. This causes luxurian