Trend Analysis of Lake Surface Temperatures in Lake Van

Abstract

In this study, the change and trend of water surface temperatures of Lake Van has been investigated. For the period of 2016- 2020; NASA-Day, NASA-Night satellite and measurement data obtained from the Turkish State Meteorological Service for 3 stations were compared. In addition, the monthly, the annual (minimum-average-maximum), the seasonal trend analysis of day and night longterm satellite data (2001-2020) and their significance levels were determined by the Theil-Sen and Innovative Trend Analysis. Measurement data covering for the period of 2016-2020 and NASA-Day, NASA-Night satellite data were highly compatible (R=0,94- 0,99). NASA-Night water surface temperatures were found to be more compatible with measurement data than NASA-Day satellite data. NASA-Day and NASA-Night water surface temperatures covering for the period of 2001-2020 were found to be homogeneous at a 1% significant level. Water surface temperatures tend to increase both in the short and long term. The highest increase in monthly analyses (0,094 °C/year) was determined in June for NASA-Day and in April for NASA-Night (0,104 °C/year). The highest increase in seasonal analyses was seen in night data (0,080-0,099 °C/year) in the spring season. The average increase in long-term annual average water surface temperatures was calculated as 0,043 °C/year. It was concluded that this value is smaller than the increase determined for the Eastern Black Sea (0,11 °C/year), higher than the calculated for the Aegean and Eastern Mediterranean (0,055°C/year), approximately 1,5 times the increase determined for the South Caspian Sea (0,029 ± 0,009 °C /year) and about 4 times the increase (as 0,011 °C/year) for the oceans.

Keywords

• lake van
• lake surface temperature
• trend analysis
• homogeneity