Resolution tests to determine the minimum number of isothermal vs. nonisothermal layers needed for numerical convergence. The left panel shows various temperature–pressure profiles computed using 51, 201, and 1001 isothermal layers vs. 21, 101, and 501 nonisothermal layers, demonstrating that the use of isothermal layers is not an efficient approach. The right panel shows the deviation or error in the synthetic spectrum, as a function of wavelength, using the model with 501 nonisothermal layers as a reference.