February 2020 was anomalously warm in the Antarctic Peninsula region and registered one of the most intense heatwaves ever recorded in Western Antarctica. The event featured unprecedented regional mean temperature anomalies (+4.5 °C) over the Antarctic Peninsula between 6 and 11 February 2020 and the highest local temperature of the continental Antarctic region. Taking flow analogs of the event from past (1950–1984) and recent (1985–2019) periods of the ERA5 reanalysis, here we quantify the role of recent climate change in the magnitude of this 6-day regional heatwave. Results show that 2020-like heatwaves over the Antarctic Peninsula are now at least ~0.4 °C warmer than in the past period, which represents a ~25% increase in magnitude. Given the observed atmospheric circulation conditions, the probability of experiencing 6-day regional mean anomalies above ~2 °C has increased ten times since 1950–1984. The aggravated severity of the event can be largely ascribed to long-term summer warming of the Antarctic Peninsula rather than recent atmospheric circulation trends.

The Antarctic Peninsula (AP) experienced a new extreme warm event and record-high surface melt in February 2022, rivaling the recent temperature records from 2015 and 2020, and contributing to the alarming series of extreme warm events over this region showing stronger warming compared to the rest of Antarctica. Here, the drivers and impacts of the event are analyzed in detail using a range of observational and modeling data. The northern/northwestern AP was directly impacted by an intense atmospheric river (AR) attaining category 3 on the AR scale, which brought anomalous heat and rainfall, while the AR-enhanced foehn effect further warmed its northeastern side. The event was triggered by multiple large-scale atmospheric circulation patterns linking the AR formation to tropical convection anomalies and stationary Rossby waves, with an anomalous Amundsen Sea Low and a record-breaking high-pressure system east of the AP. This multivariate and spatial compound event culminated in widespread and intense surface melt across the AP. Circulation analog analysis shows that global warming played a role in the amplification and increased probability of the event. Increasing frequency of such events can undermine the stability of the AP ice shelves, with multiple local to global impacts, including acceleration of the AP ice mass loss and changes in sensitive ecosystems.

This paper describes a methodology for processing spectral raw data from Micro Rain Radar (MRR), a K-band vertically pointing Doppler radar designed to observe precipitation profiles. The objective is to provide a set of radar integral parameters and derived variables, including a precipitation type classification. The methodology first includes an improved noise level determination, peak signal detection and Doppler dealiasing, allowing us to consider the upward movements of precipitation particles. A second step computes for each of the height bin radar moments, such as equivalent reflectivity (Z_e), average Doppler vertical speed (W), spectral width (σ), the skewness and kurtosis. A third step performs a precipitation type classification for each bin height, considering snow, drizzle, rain, hail, and mixed (rain and snow or graupel). For liquid precipitation types, additional variables are computed, such as liquid water content (LWC), rain rate (RR), or gamma distribution parameters, such as the liquid water content normalized intercept (N_w) or the mean mass-weighted raindrop diameter (D_m) to classify stratiform or convective rainfall regimes. The methodology is applied to data recorded at the Eastern Pyrenees mountains (NE Spain), first with a detailed case study where results are compared with different instruments and, finally, with a 32-day analysis where the hydrometeor classification is compared with co-located Parsivel disdrometer precipitation-type present weather observations. The hydrometeor classification is evaluated with contingency table scores, including Probability of Detection (POD), False Alarm Rate (FAR), and Odds Ratio Skill Score (ORSS). The results indicate a very good capacity of Method3 to distinguish rainfall and snow (PODs equal or greater than 0.97), satisfactory results for mixed and drizzle (PODs of 0.79 and 0.69) and acceptable for a reduced number of hail cases (0.55), with relatively low rate of false alarms and good skill compared to random chance in all cases (FAR < 0.30, ORSS > 0.70). The methodology is available as a Python language program called RaProM at the public github repository.

The upward evolution of temperatures in the Antarctic Peninsula has weakened and even reversed in the last two decades. Due to the long-term variability in the region it is not easy to assess whether recent cooling trends are consistent with the internal variability or not. For this reason, this paper assesses the robustness of the trends by analysing their sensitivity with respect to the period selected. Every possible temperature trend in the interval 1958–2016 has been calculated and displayed in a two-dimensional parameter diagram. The results suggest that the warming observed in the Antarctic Peninsula since 1958 is quite robust, as all periods longer than 30 years exhibit statistically significant changes, especially in summer (with lower magnitude and higher significance) and autumn and winter (with larger magnitude and lower significance). Periods shorter than 30 years exhibit alternations of warming and cooling periods, and therefore do not represent robust trends even if they are statistically significant. Consequently, the recent 20-year cooling trend cannot be considered at the moment as evidence of a shift in the overall sign of the trend.

In this paper, we illustrate a new, simple and complementary ground-based methodology to retrieve the vertically resolved atmospheric precipitation intensity through a synergy between measurements from the National Aeronautics and Space Administration (NASA) Micropulse Lidar network (MPLNET), an analytical model solution and ground-based disdrometer measurements. The presented results are obtained at two mid-latitude MPLNET permanent observational sites, located respectively at NASA Goddard Space Flight Center, USA, and at the Universitat Politècnica de Catalunya, Barcelona, Spain. The methodology is suitable to be applied to existing and/or future lidar/ceilometer networks with the main objective of either providing near real-time (3 h latency) rainfall intensity measurements and/or to validate satellite missions, especially for critical light precipitation (<3 mm h${}^{-1}$).

Using clustering analysis for the sea level pressure field of the ERA-Interim reanalysis between 1979 and 2016, five synoptic pressure patterns have been obtained for the Drake area and Antarctic Peninsula (AP) region (45°–75°S, 20°–120°W), and the resulting daily series has been made available to the scientific community. The five patterns have been named according to their most important features as follows: low over the Weddell Sea (LWS), low over the Amundsen and Bellingshausen Seas (LAB), low over the Drake Passage (LDP), zonal flow over the Drake Passage (ZDP), and ridge over the Antarctic Peninsula (RAP). Each atmospheric pattern is described after analyzing its development and evolution. A frequency analysis shows that the five atmospheric patterns present a similar annual frequency but a large seasonal variability. The transitions from one pattern to another tend to follow a cycle in which synoptic atmospheric waves are displaced eastward by a quarter wavelength. Four of the five atmospheric patterns (all except RAP) are very influenced by the southern annular mode (SAM); however, only LAB and LWS are influenced to some degree by ENSO. The occurrence of the LAB pattern presents a positive trend showing agreement with other studies that indicate an enhancement of the Amundsen–Bellingshausen Seas low. Finally, atmospheric circulation patterns have been related to the airmass advection and precipitation in Livingston Island, showing the potential application for studying the changes in the surface mass balance on the AP cryosphere.