We present several new sets of grids of model stellar atmospheres computed with modified versions of the ATLAS9 code .
Each individual set consists of several grids of models with different metallicities ranging from [ M/H ] = - 2.0 to +1.0 dex .
The grids range from 4000 to 10000 K in T _ { eff } and from 2.0 to 5.0 dex in \log { g } .
The individual sets differ from each other and from previous ones essentially in the physics used for the treatment of the convective energy transport , in the higher vertical resolution of the atmospheres and in a finer grid in the ( T _ { eff } , \log { g } ) plane .
These improvements enable the computation of derivatives of color indices accurate enough for pulsation mode identification .
In addition , we show that the chosen vertical resolution is necessary and sufficient for the purpose of stellar interior modelling .
To explain the physical differences between the model grids we provide a description of the currently available modifications of ATLAS9 according to their treatment of convection .
Our critical analysis of the dependence of the atmospheric structure and observable quantities on convection treatment , vertical resolution and metallicity reveals that spectroscopic and photometric observations are best represented when using an inefficient convection treatment .
This conclusion holds whatever convection formulation investigated here is used , i.e .
MLT ( \alpha = 0.5 ) , CM and CGM are equivalent .
We also find that changing the convection treatment can lead to a change in the effective temperature estimated from Strömgren color indices from 200 to 400 K .