Low-Frequency Atmospheric Oscillations over the Southeastern Pacific (original) (raw)
Bulletin of the American Meteorological Society
Gravity waves (GWs) play an important role in many atmospheric processes. However, the observation-based understanding of GWs is limited, and representing them in numerical models is difficult. Recent studies show that small islands can be intense sources of GWs, with climatologically significant effects on the atmospheric circulation. South Georgia, in the South Atlantic, is a notable source of such “small island” waves. GWs are usually too small scale to be resolved by current models, so their effects are represented approximately using resolved model fields (parameterization). However, the small-island waves are not well represented by such parameterizations, and the explicit representation of GWs in very-high-resolution models is still in its infancy. Steep islands such as South Georgia are also known to generate low-level wakes, affecting the flow hundreds of kilometers downwind. These wakes are also poorly represented in models. We present results from the South Georgia Wave E...
A 10-year radar-based climatology of mesoscale convective system archetypes and derechos in Poland
Monthly Weather Review
In this study a 10-year (2008-2017) radar-based mesoscale convective system (MCS) and derecho climatology for Poland is presented. This is one of the first attempt for a European country to investigate morphological and precipitation archetypes of MCSs as prior studies were mostly based on satellite data. Despite its ubiquity and significance for society, economy, agriculture and water availability, little is known about climatological aspects of MCSs over Central Europe. Our results indicate that MCSs are not rare in Poland as an annual mean of 77 MCSs and 49 days with MCS can be depicted for Poland. Their lifetime ranges typically from 3 to 6 hours with initiation time around afternoon hours (12-14 UTC) and dissipation stage in the evening (19-20 UTC). Most frequent morphological type of MCSs is a broken line (58% of cases), then areal / cluster (25%) and quasi-linear convective system (QLCS; 17%), usually associated with a bow-echo (72% of QLCS). QLCS feature also with the longes...