LEXPLORE PLATFORM

LéXPLORE Letters No. 47

This newsletter was generated on the 04-06-2024.

The figures below are showing data for the period 14-05-2024 to 28-05-2024.

Until today, Thetis sampled 4385 depth profiles on Lake Geneva. In this Newsletter we show 50 profiles, so just 1.14% of the recorded data. The complete data set is available at Datalakes.

Data highlights of this issue

May was considered to be rather wet in Switzerland and the automatic weather station on our platform also recorded plenty of precipitation. Even though the May 27th precipitation event shows the highest daily rainfall amount, it seems that the May 22nd precipitation event had the larger impact on the lake. Looking at the backscattering time series, we see a sudden and strong increase in particles in the water after May 22nd. Clearly, these two precipitation events had a different impact on the runoff into the lake. This might be due to a different temporal (short and heavy vs long and steady) or spatial distribution of the rainfall between the two precipitation events. That said, pretty much all along the second half of May we find high backscattering values, fueled by high precipitation sums.

Another noteworthy event is the windy episode on May 20th that produced waves of up to 1 meter. This is an extreme value in our wave height time series. This event shuffled the water column, pushing colder water to the surface, visible especially in the water temperature anomalies of the following days.

Curiously, we find very positive Chlorophyll A anomalies close to the surface on May 23rd. A mixture of high nutrient availability from the runoff event together with rather calm weather that day and a generally high availability of thermal energy in the water could explain this sudden but short-lived bloom. But a more in-depth analysis needs to investigate the reference data as well. The episode of positive Chlorophyll A anomalies was then ended by the May 27th precipitation event.

What is displayed

Data from the Thetis profiler:

  • Water Temperature in °Celsius

  • Water Temperature Anomaly on daily resolution with respect to to the available daily climatology from Thetis so far in Kelvin

  • Dissolved Oxygen mg/L

  • Oxygen Saturation in %

  • Chlorophyll A in μg/L

  • Chlorophyll A Anomaly on daily resolution with respect to to the available daily climatology from Thetis so far in μg/L

  • Backscattering of light 700 nm in 1.e-2 m-1, representing zooplankton or larger particles in the water

Data from the automatic weather station:

  • Air Temperature in °Celsius

  • Wind Speed in m/s

  • Precipitation in mm

Data from the wave buoy:

  • Wave height in decimeter

Authorship and further information

This newsletter is created by EPFL, specifically Martin Wegmann.

For more information about LéXPLORE, contacting us and possibilities to visit the platform: lexplore.info

If you want to know more about the Chlorophyll distribution across Lake Geneva, have a look at the satellite data map by our colleagues at CIPEL.

If you want to know more about the water temperature distribution across Lake Geneva, have a look at the lake reanalysis and forecasts by our colleagues at EAWAG.

If you want to use figures from the LéXPLORE Letters, you can use the following citation:

EPFL, Limnology Center 2024: LéXPLORE Letters, 47, https://lexplore.info/wp-content/uploads/2024/06/lexplore-letters-2024-06-04.html