About the ZHPI calculation of Ah in 'attenuation.py'

[sysumeteo]

Originally，the ZPHI method use the attenuated (measured)reflectivity to estimate Ah(r), but at line 244 in ‘attenuation.py’, a linear-PHIDP-based corrected reflectivity is used as initial reflectivity. At S band, the different is quite small to notice , but under X band , the corrected initial reflectivity result in a large bias on PIA.

[sysumeteo]

When the orignal mesured reflecitivty is used ,i found,the attenuation corrected reflectivity looks much more normal than using the pre-initial one .so i think line #244 (as below) in the code of 'attenuation.py' maybe partly doubtable.

init_refl_correct = refl + corr_phidp * a_coef