Impact of brown coal quarries hydric reclamation on microclimate, air quality, water and soil ecosystems

Motivation

Former coal mine Ležáky has been restored by the hydric recultivation and the result of this restoration is the origination of new artificial lake Most. New surface has different thermal properties (heat capacity, thermal conductivity), roughness and albedo compared with the original surface. These changes influence the atmosphere and affect the local temperature, humidity and other meteorological elements. The aim of the meteorological part of the study is to quantify these influences. Together with statistical analysis of historical and newly measured data, numerical weather prediction model (NWP) COSMO is used.

Data

We have available measurements from five meteorological stations:

  • observatory Milešovka – 837 m a.s.l. , about 20 km from the lake,
  • observatory Kopisty – 240 m a.s.l., less than 1 km from the lake, 80 m high meteorological mast.
  • CELIO – 264 m a.s.l. on the left bank  of the lake
  • AK Most – in the height of 330 m a.s.l. on the right bank of the lake
  • the lake station – placed directly on the lake surface (Fig. 2). Besides usual meteorological element it measures also lake water temperature in 16 vertical levels up to 20 m.

For model analysis we use also data from the objective analysis of the European Centre for Middle Range Weather Forecasting (ECMWF).

Elaboration, results

We made statistical comparison of two periods: 1998 – 2000 – that means the period when the lake hasn´t been flooded yet, levitra on line and 2009 – 2011 – the period after lake flooding. The second period is the period when the atmosphere, as we suppose, could already have been affected by the lake. The results show that the air humidity has increased in the second period and that air temperature in 2 m at 7, 14 and 21 UTC has decreased. To analyse the impact of the lake on precipitation we used the statistical methods principal component analysis and Mann-Whitney-Wicoxon test. The results don´t show any significant impact of the lake on precipitation amount.

In the second part of analysis we used numerical weather prediction model COSMO to simulate the affect of lake Most on air temperature. First step was to find right parameters of the model with 333 m horizontal resolution. We determined right boundary conditions, turbulence scheme and the model field size. We made a number of model integrations and their analyses for warm and cold part of the year, for different lake sizes, for snow conditions and for real data and orography.

One of the results is pictured at figure 1 where the mean values of the lake influence on air temperature in the vertical level 0.2 m above the surface and for four lake sizes are shown. Delta means the difference between lake water temperature and air temperature in 2 m. It is obvious that the lake influence depends significantly on its size.

We determined the most important parameters that influence the lake affect on air temperature. These parameters are: air temperature and humidity in 2 m, water temperature in the mixing layer, wind speed in 10 m and lake size. Surface temperature has been defined as the supplemental parameter. These parameters have been used as input parameters to the developed simple physical model ALAKE and afterwards to the software ALAKE.

Průměrné hodnoty vlivu jezera na teplotu vzduchu v hladině 0,2 m nad zemským povrchem

Figure 1. Mean values of lake influence at the elevation of 0.2 m above the surface for four lake lengths equalled 8, 4, 3 and 2 grid points and indicated by L8, L4, L3 and L2, respectively. The left coast of the lake was at x=69. Mean values were calculated over the warm period (left column) and cold (right column) in dependence on D (delta).