Land-water-atmosphere interaction over a deep large high-altitude lake: generation of mesoscale cyclones (limnocanes) over Lake Hovsgol (Mongolia)

Lake Hovsgol in Mongolia is a large deep mountainous lake. This lake is located in continental climate conditions and is ice-covered every year between December and June. In winter large water volume lead to significant heat inertia, late ice cover formation and strong temperature contrast between air over the lake and over land. 

We first discuss a mesoscale cyclone that has been formed over the lake in December 2023. There are extratropical mesoscale cyclones which take their energy from the large-scale baroclinic instability, such as most cyclones in the Mediterranean sea. However, some cyclones such as Medicanes (“Mediterranean hurricanes”) and polar lows develop from both baroclinic instability (like extratropical cyclones) and surface exchanges over the relatively warm sea (like tropical cyclones). There were also cases when cyclones were observed over lakes, such as Great Lakes, or Lake Victoria, but in most cases these cyclones developed elsewhere and their size was several hundreds of kilometers - much larger than the lakes themselves.

We analyse the generation, evolution and dissipation of a cyclone over lake Hovsgol in 2023 using various satellite imagery in the visible, thermal and microwave ranges, as well as meteorological data. Rapid decrease of air temperature from –8 to –30°C led to wind oriented from the coast to the lake, creation of several convergence lines and ultimately formation of a cyclone with outer radius of about 35 km. This cyclone has been generated over the lake itself (and not advected from some other regions) and its size was limited by the lake size which itself is 130x35 km. The cyclone was short lived (about 24 hours) but had a well-developed cloud-free eye with diameter of 3.5 km, comma head and outflow cirrus shield. Heavy snowfall was observed at that time by local populations. Two days after cyclone dissipation most of the lake was ice covered.

We present data on cyclone position and displacement, estimate speed and direction of wind-driven ice drift during the cyclone presence and based on this assess potential speed of surface wind. We also estimate height and temperature of cloud cover. We discuss the potential structure of the cyclone, its influence on surface water currents and ice formation.

We also present several other cases when such cyclones have been observed over lake Hovsgol in other years. These examples confirm that such events are a repeatable feature over deep and large lakes, and we propose to call them Limnocanes (by analogy with Medicanes).

This research was supported by the CNES TOSCA LAKEDDIES-II, TRISHNA and SWIRL projects. A.G. Kostianoy was supported in the framework of the Shirshov Institute of Oceanology RAS budgetary financing (Project N FMWE--2024-0016).