[Insert Figure 3(a,b,c) about here]
Figure 3: The distribution of mean surface water temperature of lakes in Eurasia during the daytime (a), nighttime (b), and diurnal temperature difference (DTD) (c). Reported data are from the summer 2015.
3.2. Inter-annual variation in lake surface temperatures
Following the IPCC AR.5 report (IPCC, 2014) and the recommendation “to track global warming hotspots with reference to global climatic zones and corresponding lake distributions”, a group of 10 typical lakes (largest lakes within a climatic zone) from Asia and 8 typical lakes from Europe (Figure 1) were selected, and analyzed with respect to inter-annual variation in LWST using MODIS LST measurements from 2001 to 2015.
3.2.1. Typical lakes from Asia
The inter-annual variations in LWST for the 10 typical lakes from Asia during the period 2001-2015 are shown in Figure 4. From the annual daytime and nighttime LWST values, there was no clear trend in lake water temperature during the study period. For Lake Baikal, a slight increase in LWST was observed with both daytime and nighttime measurements (Figure 4(a)). On the Mongolia Plateau, a slight but insignificant rise in LWST was apparent for Lake Khar Us at nighttime, whereas Lake Uvs showed a slight temperature decrease, albeit not significant, over the study period (Figure 4(e) and Figure 4(b)). Likewise, for Lake Balkhash and Khanka, a slight decrease at daytime and a slight increase at nighttime were observed, but these trends were not significant (Figure 4(c) and Figure 4(f)). Situated in the Pamir, the alpine Lake Issyk underwent a rather weak temperature decline over time, but this was not a significant trend (Figure 4(d)). It is worth noting that Lake Taymyr (Figure 4(h)), did show a strong and obvious increase in temperature during the study period (2001-2015) for both daytime and nighttime measurements (y = 0.19x - 392.76, R² = 0.51, P=0.003 for daytime; and y = 0.2x - 408.52, R² = 0.44, P=0.007 for nighttime). For Lake Van and Lake Young Bhutto, a slight increase in both of daytime and nighttime temperature was observed. For Lake Tonlesap, there was no clear trend of rising daytime LST, but a slight albeit not significant nighttime decrease in LST was noted (Figure 4(j)).