Atmospheric reanalyses depend on a mix of observations and model forecasts. In data-sparse regions such as the Arctic, the reanalysis solution is more dependent on the model structure, assumptions, and data assimilation methods than in data-rich regions. Applications such as the forcing of ice–ocean models are sensitive to the errors in reanalyses. Seven reanalysis datasets for the Arctic regio...

This paper proposes the hypothesis that the low-frequency variability of the North Atlantic Oscillation (NAO) arises as a result of variations in the occurrence of upper-level Rossby wave–breaking events over the North Atlantic. These events lead to synoptic situations similar to midlatitude blocking that are referred to as high-latitude blocking episodes. A positive NAO is envisaged as being a...

This study aims to assess the performance of European Center for Medium-Range Weather Forecasting (ECMWF) Reanalysis fifth generation (ERA5) in terms progress made over its predecessor, ERA-Interim, East Africa (EA) reproducing observed rainfall. The rainfall used as reference are Global Precipitation Climatology (GPCC) and Climate Research Unit Time Series (CRU-TS). ERA5 predecessor is evaluat...

Sudden stratospheric warmings are prominent examples of dynamical wave–mean flow interactions in the Arctic stratosphere during Northern Hemisphere winter. They are characterized by a strong temperature increase on time scales of a few days and a strongly disturbed stratospheric vortex. This work investigates a wide class of supervised learning methods with respect to their ability to classify ...

The distribution of the daily wintertime North Atlantic Oscillation (NAO) index in the 40-yr ECMWF ReAnalysis (ERA-40) is significantly negatively skewed. Dynamical and statistical analyses both suggest that this skewness reflects the presence of two distinct regimes—referred to as ‘‘Greenland blocking’’ and ‘‘subpolar jet.’’ Changes in both the relative occurrence and in the structure of the r...

Abstract. This study compares trends in the Hadley cell (HC) strength using different metrics applied to ECMWF ERA5 and ERA-Interim reanalyses for period 1979–2018. The HC is commonly evaluated by derived from mass-weighted zonal-mean stream function isobaric coordinates. Other include upper tropospheric velocity potential, vertical mid-troposphere, water vapour transport lower troposphere. Sev...

Abstract. The tropopause layer plays a key role in manifold processes atmospheric chemistry and physics. Here we compare the representation characteristics of lapse rate according to definition World Meteorological Organization (WMO) as estimated from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data. Our study is based on 10-year records (2009 2018) ECMWF's state-of-th...