Previsão de ondas equatoriais em modelos operacionais

This project builds on three main objectives. First, it is pretended to establish a novel multivariate method for real-time identification of equatorial waves (EWs) in analyses and forecasts. The technique follows a similar procedure as that of Yang et al. (2021), but is based on the recent methodologies of Castanheira and Marques (2023) and Cruz et al (2024) for the identification of EWs. As in Yang et al. (2021), the real-time technique proceeds by using an off-centered time window extended with forecasts beyond the current analysis. However, different from Yang et al. (2021), this technique uses a multivariate approach, i.e. the horizontal wind and geopotential fields are projected simultaneously onto the Hough vectors, and no previous space-time spectral analysis is necessary to separate eastward- and westward-moving waves. Subsequently, open source software tools will be produced for a practical implementation of this multivariate method for real-time identification of EWs. These tools can be used to identify EWs in operational model forecasts, which are associated to the likelihood of extreme precipitation and increases in precipitation amount. In the final stage of the project, it is planned the realization of a seminar to present the results and training the use of the software. Elements of various national meteorological institutes from Portuguese spoken countries in the tropical region (e.g. Angola, Guinea-Bissau, Mozambique, etc.) will be invited to participate in the seminar. Second, tacking advantage of the forecast tools developed previously, equatorial wave forecasting will be assessed in operational numerical weather prediction (NWP) systems. The main challenge to be address is to assess the relationship between the models’ ability to simulate equatorial waves and forecast skill. That is, how well EWs are represented in these operational NWP models, e.g. their structures, amplitude and phase speed, and how this influences precipitation forecasts. For these analysis, two global NWP systems will be used, the National Centers for Environmental Prediction - Global Forecast System (NCEP-GFS) and the European Centre for Medium-Range Weather Forecasts - Integrated Forecast System (ECMWF-IFS). Third, to address the influence of cumulus parameterization on the simulation of EWs, it will be performed a series of experiments using the Advanced Research Weather Research and Forecasting (WRF) model to simulate known events of clear manifestation of EWs. Experiments with different parameterizations, such as simplified Arakawa Schubert (SAS), Betts-Miller-Janjic (BMJ), improved Kain-Fritch (KFT), modified Tiedtke (TDK), etc., different resolutions and initial conditions will be considered. In addition, to check the hypothesis that resolved convection leads to a better representation of EWs in NWP models, it will be also carried out a high-resolution experiment with explicitly resolved convection. Operational GFS and/or IFS analysis will be used for initial and boundary conditions. Identification of EWs will be performed using the recent methodology of Castanheira and Marques (2023), for both the original analysis (GFS and/or IFS) and the WRF forecasts.