Evaluation of hourly forecasts of the European Centre for Medium‐Range Weather Forecasts over the southeastern extension of the Tibetan Plateau

Abstract

AbstractThe accuracy of rainfall and low‐level atmospheric circulation forecasts of the European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) is evaluated through comparison with gauge observations during the warm seasons (May–September) from 2019 to 2020 over the southeastern extension of the Tibetan Plateau (SETP). The IFS can suitably capture the spatial distribution of the rainfall frequency over the SETP but generally overestimates the rainfall amount and frequency and underestimates the rainfall intensity. The IFS can hardly simulate the early‐morning and morning peaks in the gauge observations. In two regions along the southern edges of the SETP, exhibiting distinct diurnal features, the difference in the peak time of the rainfall frequency between these two key regions cannot be reproduced in IFS simulations. The simulated rainfall occurs earlier at night, which can be related to the earlier strengthening of southerlies and water vapour flux in the IFS simulations. In the afternoon, the low‐elevation atmosphere is warmer and wetter, in addition to more unstable energy in the IFS simulations, which can contribute to the forecast deviation in the afternoon rainfall frequency.