tokens: cloud temperature is assumed to be 5000 K, the column density, , will be enhanced for a given cloud mass. Therefore, for the initial mass function with α = −1 and adopted in this work, the model will produce more systems and overproduce the gas covering fraction for such systems. On the other hand, by increasing the temperature of clouds to be 20000 K, all the gas clouds become highly ionized with . Such a scenario cannot produce any high column density systems as observed. This suggests that the adopted cloud temperature with 10 4 K is perhaps reasonable for reproducing the gas properties of high gas absorbers. Survival of clouds – One of the key assumptions in our model is that the clouds are not destroyed by the hydrodynamic instability. Although a number of studies have shown that various mechanisms can suppress the effect of hydrodynamical instability (e.g. Vietri et al. 1997 ; McCourt et al. 2015 ; Armillotta et al. 2017 ; Gronke Oh 2018 ), it is still unclear how these mechanisms operate in reality. This problem is related to the problem of entraining the cool gas along with a hot wind (e.g. Zhang et al. 2017 ). However, we argue that the existence of cool gas and the evidence of contribution from outflows in the haloes (e.g. Bordoloi et al. 2011 ; Lan Mo 2018 ) suggest that either the cool gas outflows must survive over the hydrodynamic instability, as we assume in our model, or cool gas is redistributed in the haloes by some other mechanisms associated with outflows (e.g. Thompson et al. 2016 ; Lochhaas et al. 2018 ). Gas properties at large scales – Our model has difficulties in explaining systems with beyond 100 kpc (e.g. Zhu et al. 2014 ; Huang et al. 2016 ; Lan Mo 2018 ) due to the low volume density of the hot ambient gas as shown in Fig. 2 . It is, therefore, likely that some of the systems at large distances are produced by neighbouring haloes due to spatial clustering of haloes. Such ‘two-halo’ term is not included in our current model, but should be modelled. 5 SUMMARY We develop a flexible semi-analytic framework to explore the physical properties of the cool pressure-confined circumgalactic clouds with mass from 10 to . We take into account the effects of gravity and interaction between hot gas and cool gas and model the trajectory, the lifetime, and the observed properties of the cool clouds with cloudy simulations. The ensemble properties of the cool CGM are explored by populating clouds following various mass functions in the haloes with three origins, outflows, inflows, and in situ formation. With this framework, we investigate how different mechanisms affect the observed properties of the cool CGM. Our results are summarized as follows: The pressure-confined cool gas clouds have with sizes about 10–100 pc similar to the properties of strong metal absorbers, sub-DLAs, and DLAs observed towards background spectra. We illustrate the effect of hot gas on the motion and lifetime of cool gas clouds; the ram pressure from the
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