  Reconstruction of energies of very-high-energy gamma-rays observed by imaging
atmospheric Cherenkov telescopes is affected by changes in the atmospheric
conditions and the performance of telescope components. Reliable calibration
schemes aimed at these effects are necessary for the forthcoming Cherenkov
Telescope Array (CTA) to achieve its goals on the maximally allowed systematic
uncertainty of the global energy scale. A possible means of estimating the
atmospheric attenuation of Cherenkov light is the method of the Cherenkov
transparency coefficient (CTC). The CTC is calculated using the telescope
detection rates, dominated by the steady cosmic ray background, while properly
correcting for the hardware and observational conditions. The coefficient can
also be used to relatively calibrate the optical throughput of telescopes on
the assumption of homogeneous atmospheric transparency above the array. Using
Monte Carlo simulations, we investigate here the potential of the CTC method
for the atmospheric monitoring and telescope cross-calibration at the CTA array
in the southern hemisphere. We focus on the feasibility of the method for the
array of telescopes of three sizes in different observation configurations and
under various levels of atmospheric attenuation.
