Inter-comparison of HARMONIE and WRF model simulations in convective-permitting scale over western area of Iran

Ever increasing attention is being paid to the use of Numerical Weather Prediction (NWP) models in the convection-permitting mode for providing high-resolution forecasts. In such applications, the use of NWP models and comparison among the simulations of models help us to understand the problems associated with these scales and to unravel the systematic errors of the models. In this study, two weeks of “model simulation experiments” have been conducted with the HARMONIE-AROME and the WRF-ARW meso-scale NWP models at 2.5 km horizontal resolution, in order to partly resolve convective phenomena on the same domain over the mountainous areas of the west of Iran for the period of 1–15 December 2013. All experiments have been conducted by using the ECMWF ERA-Interim reanalyses for the lateral boundary conditions, and for this reason, they are called “model simulation experiments”. The HARMONIE Verification System has been used for the validation, and operational radiosonde and SYNOP observations from the ECMWF have been used for the verification. The precipitation observations from some climatological stations of Iran have also been used. The model simulations described in this study were run up to +72 h. The motivation for this long simulation time is to investigate any possible systematic model problems that could hide possible impact of data assimilation in the planned data assimilation forecast experiments. Generally, the WRF and HARMONIE have a comparable performance, both of which have similar results for some variables at all forecast lead times. For 24-hour accumulated precipitation forecasts, the correlation coefficient, the bias and the root mean square error (RMSE) were used to compare the performance of both models over the same area. For the correlation coefficient and the RMSE, the WRF has slightly better verification scores at all lead times. The results for the temperature at 2 m, wind speed and direction at 10 m, and specific humidity (mixing ratio) at 2 m are verified by using different verification scores. A similar behavior is found for both models in the error standard deviation (STDV) verification score; although some minor differences are observed at some lead times and for some variables. A more significant difference is related to the bias of specific humidity at 2 m for the WRF and HARMONIE as over-estimation of moisture for the HARMONIE and its under-estimation for the WRF. Considering the upper air profiles of the bias and the STDV of the error, both similarities and differences were shown for the vertical structures of various quantities as obtained by the two model simulations. While the strongest similarity was seen in the bias and the STDV of the temperature error profiles, the relative humidity at 850 hPa exhibited the largest differences in both measures of error. A dry bias, which increased with the forecast time, was noticed for the WRF at low levels (850 hPa) as verified against the radiosonde data as well as the SYNOP data at 2 m level.