A global perspective on atmospheric blocking using GPS radio occultation – one decade of observations

Abstract

Abstract. Atmospheric blocking represents a weather pattern where a stationary high-pressure system weakens or reverses the climatological westerly flow at mid-latitudes for up to several weeks. It is closely connected to strong anomalies in key atmospheric variables such as geopotential height, temperature, and humidity. Here we provide, for the first time, a comprehensive, global perspective on atmospheric blocking and related impacts by using an observation-based data set from Global Positioning System (GPS) radio occultation (RO) from 2006 to 2016. The main blocking regions in both hemispheres and seasonal variations are found to be represented well in RO data. The effect of blocking on vertically resolved temperature and humidity anomalies in the troposphere and lower stratosphere is investigated for blocking regions in the Northern and Southern hemispheres, respectively. We find a statistically significant correlation of blocking with positive temperature anomalies, exceeding 3 K in the troposphere, and a reversal above the tropopause with negative temperature anomalies below −3 K in the lower stratosphere. Specific humidity is positively correlated with temperature throughout the troposphere with larger anomalies revealed in the Southern Hemisphere. At the eastern and equatorward side of the investigated blocking regions, a band of tropospheric cold anomalies reveals advection of cold air by anticyclonic motion around blocking highs, which is less distinct in the Southern Hemisphere due to stronger zonal flow. We find GPS RO to be a promising new data set for blocking research that gives insight into the vertical atmospheric structure, especially in light of the expected increase in data coverage that future missions will provide.

Atmospheric blocking events in the North Atlantic: trends and links to climate anomalies and teleconnections

“…A large region of positive correlation is present in northeastern Canada, Labrador Sea, Greenland and Irminger Seas, and over tropical North Atlantic and North Africa, suggesting warm anomalies during blocked days over these areas, as Fig. 4 a Seasonal (JFM, AMJ, JAS and OND) non-linear correlation between blocking occurrence in the Atlantic sector and SAT anomalies and, b the average of SAT anomalies (in °C) in the winter (JFM) during the blocked and non-blocked days (left and right panels, respectively) also noted by Rimbu and Lohmann (2011) and Brunner and Steiner (2017). Conversely SATs decrease with the occurrence of blocked days from the United States toward northern Europe and part of Eurasia (e.g., Sillmann and Croci-Maspoli 2009;Stankūnavičius et al 2017;Trigo et al 2004).…”

“…During summer, the links are less pronounced over the North Atlantic and continental areas, with warm anomalies over the Indian Ocean and South Pacific during blocked days. There is no evidence of significant correlation between blocked days in the North Atlantic and SAT in summer over Europe, in agreement with Sillmann and Croci-Maspoli (2009) and Brunner and Steiner (2017). However, striking examples are the 2003 European and 2010 Russian heat extremes that resulted from exceptionally long-lasting summer-time blocking events over land, leading to precipitation deficit, pronounced droughts and significant increases in human mortality rates (Black et al 2004;Dole et al 2011).…”

Wind Power Persistence Characterized by Superstatistics

“…3 and Supplementary Note 2. This seems unexpected, as surface cyclones, which are associated with high wind speeds, usually pass Europe within only a few days due to their typical propagation velocity 68 , while atmospheric blocking events, which may cause long-lasting calms, can have a lifetime of up to several weeks 69 . We perform a synoptic analysis of selected high- and low-wind periods to examine these findings.…”

Tropical convection regimes in climate models: evaluation with satellite observations

“…These data from multiple RO satellites facilitate the provision of daily climatologies of 2.5 • × 2.5 • in latitude and longitude, which can be obtained by weighted averaging in space and time. The use of such higher resolved daily RO climatological fields has been demonstrated only recently for the investigation of atmospheric blocking (see Brunner et al, 2016;Brunner and Steiner, 2017).…”