Model Cycle 38r2: Components and Performance

Model Cycle 38r2: Components and Performance
Technical memorandum
Date Published
Secondary Title
ECMWF Technical Memoranda
Abstract On 25 June 2013, a new model cycle (38r2) has been introduced at ECMWF. The main contributions are an increase of the number of vertical levels from 91 to 137 in high-resolution forecast model, the ensemble of data assimilations, the main assimilation and the Boundary-Conditions optional programme, revised background error variances at 137 levels based on IFS cycle 38r1, revised EDA calibration and filtering for 137 levels, deactivation of the model error cycling in the stratosphere, activation of unbalanced control vector components, a modification of surface drag, test parcel entrainment in boundary layer and shallow convection, auto-conversion in convection, an adjustment of non-orographic gravity wave drag, an oxygen absorption correction, and a revision of sea-ice/sea-surface-temperature quality control over the Caspian Sea. The scaling factor for singular vector initial perturbations in the ensemble system (ENS) has been slightly increased. Tropospheric upper-air scores are overall slightly positive in northern hemisphere and mainly neutral for Europe and southern hemisphere. Performance in the tropics is mixed with some negative results compared to observations but neutral against analyses. The main positive impacts are for geopotential in the lower stratosphere, and to a lesser extent also in the troposphere. The scores for 10-metre wind show neutral to slightly positive impact both in extra-tropics and tropics. In general cycle 38r2 is neutral for the ENS in terms of the spread and ensemble-mean skill for the extra-tropics. In the tropics, spread is also changed little. Ensemble mean error is improved for 850 hPa temperature, and slightly worse for 850 hPa wind speed. In terms of probabilistic scores, the CRPS is neutral for 500 hPa height, 850 hPa temperature and wind speed over Europe and the northern extra-tropics. Over the southern extra-tropics e-suite scores are better for 500 hPa height, but worse for days 1-3 for temperature at 850 hPa.
DOI 10.21957/xc1r0lj6l