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A set of decadal simulations has been completed and evaluated for gains using the Regional Arctic System Model (RASM) to dynamically downscale data from a global Earth system model and two atmospheric reanalyses. RASM is a fully coupled atmosphere-land-ocean-sea ice regional Earth system model. Nudging to the forcing data is applied to approximately the top half of the atmospheric domain. RASM simulations were also completed with a modification to the atmospheric physics for evaluating changes to the modeling system. The results show that for the top half of the atmosphere, the RASM simulations follow closely to that of the forcing data, regardless of the forcing data. The results for the lower half of the atmosphere, as well as the surface, show a clustering of atmospheric state and surface fluxes based on the modeling system. At all levels of the atmosphere the imprint of the weather from the forcing data is present as indicated in the pattern of the annual means. Biases, in comparison to reanalyses, are evident in the Earth system model forced simulations for the top half of the atmosphere but are not present in the lower atmosphere. This suggests that bias correction is not needed for fully coupled dynamical downscaling simulations. While the RASM simulations tended to go to the same mean state for the lower atmosphere, there are a differences in the variability and changes of weather patterns across the ensemble of simulations. These differences in the weather result in variances in the sea ice and oceanic states. [ABSTRACT FROM AUTHOR]

An extreme warming event near the North Pole, with temperature rising above 0 ℃, was observed in late December 2015. This specific event has been attributed to cyclones and their associated moisture intrusions. However, little is known about the characteristics and drivers of similar events in the historical record. Here, using data from ERA5, we study these winter extreme warming events with temperature above 0 ℃ over the high Arctic (poleward of 80° N) occurred during 1980–2021. In ERA5, such extreme events can only be found over the Atlantic sector. They occur rarely, with a seasonal occurrence frequency less than one over most of the regions. Furthermore, even when occurring, they tend to be short-lived, with the majority of the events lasting for less than a day. By examining their surface energy budget, we found that these events transition with increasing latitude from a regime dominated by turbulent heat flux into the one dominated by downward longwave radiation. Blockings over the northern Eurasia are identified as a key ingredient in driving these events, as they can effectively deflect the eastward propagating cyclones poleward, leading to intense moisture and heat intrusions into the high Arctic. Using an atmospheric river (AR) detection algorithm, the roles of ARs in driving these events are explicitly quantified. The importance of ARs in inducing these events increases with latitude. Poleward of about 83° N, ARs are the direct driver for 100 % of these events, corroborating the indispensable roles ARs played in driving these events. Over the past four decades, both the frequency, duration, and magnitude of these events have been increasing significantly. As the Arctic continues to warm, these events are likely to increase in both frequency, duration and magnitude, with great implications for the local sea ice, hydrological cycle and ecosystem. [ABSTRACT FROM AUTHOR]

An extreme warming event near the North Pole, with temperature rising above 0 ℃, was observed in late December 2015. This specific event has been attributed to cyclones and their associated moisture intrusions. However, little is known about the characteristics and drivers of similar events in the historical record. Here, using data from ERA5, we study these winter extreme warming events with temperature above 0 ℃ over the high Arctic (poleward of 80° N) occurred during 1980–2021. In ERA5, such extreme events can only be found over the Atlantic sector. They occur rarely, with a seasonal occurrence frequency less than one over most of the regions. Furthermore, even when occurring, they tend to be short-lived, with the majority of the events lasting for less than a day. By examining their surface energy budget, we found that these events transition with increasing latitude from a regime dominated by turbulent heat flux into the one dominated by downward longwave radiation. Blockings over the northern Eurasia are identified as a key ingredient in driving these events, as they can effectively deflect the eastward propagating cyclones poleward, leading to intense moisture and heat intrusions into the high Arctic. Using an atmospheric river (AR) detection algorithm, the roles of ARs in driving these events are explicitly quantified. The importance of ARs in inducing these events increases with latitude. Poleward of about 83° N, ARs are the direct driver for 100 % of these events, corroborating the indispensable roles ARs played in driving these events. Over the past four decades, both the frequency, duration, and magnitude of these events have been increasing significantly. As the Arctic continues to warm, these events are likely to increase in both frequency, duration and magnitude, with great implications for the local sea ice, hydrological cycle and ecosystem. [ABSTRACT FROM AUTHOR]

The accurate measurement of precipitation in Antarctica continues to be an elusive task for studies involving the meteorology and climatology of the ice-covered continent. The two primary difficulties with measuring [...]

Between January 2012 and June 2017 a small unmanned aerial system (UAS), known as the Small Unmanned Meteorological Observer (SUMO), was used to observe the state of the atmospheric boundary layer in the Antarctic. During 6 Antarctic field campaigns 116 SUMO flights were completed. These flights took place during all seasons over both permanent ice and ice free locations on the Antarctic continent and over sea ice in the western Ross Sea. Sampling was completed during spiral ascent and descent flight paths that observed the temperature, humidity, pressure and wind up to 1000 m above ground level and sampled the entire depth of the atmospheric boundary layer as well as portions of the free atmosphere above the boundary layer. A wide variety of boundary layer states were observed including very shallow, strongly stable conditions during the Antarctic winter and deep, convective conditions over ice free locations in the summer. The Antarctic atmospheric boundary layer data collected by the SUMO sUAS, described in this paper, can be retrieved from the United States Antarctic Program Data Center (https://www.usap-dc.org). The data for all flights conducted on the continent are available at https://www.usap-dc.org/view/dataset/601054 (Cassano 2017; https://doi.org/10.15784/601054) and data from the Ross Sea flights, are available at https://www.usap-dc.org/view/dataset/601191 (Cassano 2019; https://doi.org/10.15784/601191). [ABSTRACT FROM AUTHOR]

ABSTRACT The atmospheric state and synoptic situation associated with widespread summer June, July, and August temperature extremes in southern Alaska is explored. Using ERA-Interim data and a self-organizing map framework, the evolution of the atmospheric state leading up to days that are defined as experiencing extreme surface temperature are compared with the evolution for non-extreme days. The variables evaluated include circulation at the surface and aloft and surface radiative fluxes. For warm extremes, blocking evident in the 500 hPa flow combined with anomalously large surface downward shortwave radiation allowed surface temperatures to become extreme. For cold extremes, an upper level trough and cold air advection aloft coupled with a more minor role of anomalously negative surface downward shortwave radiation were important. The self-organizing map framework allowed an investigation of these details beyond a composite analysis of all extremes. [ABSTRACT FROM AUTHOR]

The article features the study conducted on surface wind fields of the Ross Ice Shelf region in Antarctica. Researchers define four wind regimes for austral autumn including barrier wind, strong katabatic, weak katabatic and light wind wherein each was characterized through wind rose plots and corresponding sea level pressure from the Antarctic Mesoscale Prediction System (AMPS). They concluded that the research provides a better understanding of the composition of the surface wind field in the area and an insight to the characteristics of the Ross Ice Shelf air stream.