In the present work, we simulate the Pliocene climate with the EC-Earth climate model as an equilibrium state for the current warming climate induced by rising CO₂ in the atmosphere. The simulated Pliocene climate shows a strong Arctic amplification featuring pronounced warming sea surface temperature (SST) over the North Atlantic, in particular over the Greenland Sea and Baffin Bay, which is comparable to geological SST reconstructions from the Pliocene Research, Interpretation and Synoptic Mapping group (PRISM; Dowsett et al., 2016). To understand the underlying physical processes, the air–sea heat flux variation in response to Arctic sea ice change is quantitatively assessed by a climate feedback and response analysis method (CFRAM) and an approach similar to equilibrium feedback assessment. Given the fact that the maximum SST warming occurs in summer while the maximum surface air temperature warming happens during winter, our analyses show that a dominant ice-albedo effect is the main reason for summer SST warming, and a 1 % loss in sea ice concentration could lead to an approximate 1.8 W m⁻² increase in shortwave solar radiation into open sea surface. During the winter months, the insulation effect induces enhanced turbulent heat flux out of the sea surface due to sea ice melting in previous summer months. This leads to more heat released from the ocean to the atmosphere, thus explaining why surface air temperature warming amplification is stronger in winter than in summer.

The reduction of Arctic sea ice concentration (SIC) is a key indicator of global warming. In September 2012, SIC reached its lowest recorded value. Since then, sea ice melt has slowed down, showing a linear trend of only −0.4±6.8%/decade from 2012 to 2023, compared to −11.3±3.3%/decade from 1996 to 2011. Here, we demonstrate that the recent slowdown in September sea ice melt is closely coupled with the multi-decadal variability of the preceding summer North Atlantic Oscillation (NAO), which has transitioned from the lowest point of its negative phase in the early 2010s to a positive phase. During this shift, decreased heat and moisture, along with reduced downward longwave radiation, have contributed to offsetting the long-term decline, leading to a slowdown in Arctic sea ice melting. Additionally, the Atlantic Multidecadal Oscillation plays a primary role in driving the interdecadal variability of the NAO and Arctic sea ice by modulating wave-mean flow interactions.

Arctic winter daily warming events have sparked growing interest, particularly in recent years, when Arctic daily temperatures have approached melting point several times. This analysis reveals that the impact of the El Niño-Southern Oscillation (ENSO) on the frequency of Arctic daily warming events experienced an obvious change around the late 1970s, which may be attributed to changes in ENSO intensity. Since the late 1970s, due to stronger ENSO intensities, ENSO has induced a stronger Rossby wave; then, El Niño (La Niña) has deepened (weakened) the Aleutian Low and strengthened anomalous northerlies (southerlies) over the North Pacific, thereby decreasing (increasing) the frequency of Arctic daily warming events. In contrast, before the late 1970s, the ENSO did not have an apparent direct impact on the frequency of Arctic daily warming events due to its weaker intensity. Our findings provide a potential relationship between the equator and the Arctic to improve the prediction accuracy of extreme Arctic daily warming events. By analyzing Coupled Model Intercomparison Project phase-6 models, we confirm that the potential relation may be strengthened under the global warming scenario.

This study analyzed the diurnal variations of summer deep convective precipitation (DCP) over the Qinghai-Tibet Plateau (QTP) and its southern region. The results show that DCP is the main type of precipitation over the QTP. The precipitation intensity of DCP is less than 3 mm/h over the QTP, which is much lower than the precipitation intensity in non-plateau regions. DCP over non-plateau regions is related to the convergence of surface wind, but that over the QTP are not. The mean maximum echo of DCP is less than 26 dBZ over the QTP, less than in non-plateau regions. The mean altitude of maximum echo decreases from about 7.5 km in the western plateau to 6 km in the eastern plateau, while it reaches only 4.5–5 km in the non-plateau region. The DCP frequency peak occurs in the afternoon in the major area of the QTP including valley region. The peak time of DCP frequency is different from its intensity, and the former is 1 to 2 h earlier. Study also indicates strong diurnal variations in frequency, intensity, and the maximum echo over the QTP, which is consistent with diurnal changes of geopotential height fields of 500 hPa and 200 hPa.

Recently, the occurrence of Arctic winter daily warming events has attracted substantial attention from the media and scholars alike. Herein, these events are investigated further, particularly in respect of their relation with the Arctic Oscillation (AO). We define a Pacific pattern–Arctic rapid tropospheric daily warming (Pacific-RTDW) event, when the Arctic winter daily warming is triggered by a warm humid air mass that is transported by storms from the North Pacific into the Arctic. An anomalous northwest–southeast dipole pattern at 500-hPa geopotential is identified spanning from the Arctic to the North Pacific and associated with AO. The dipole pattern could favor the occurrence of Pacific-RTDW events because it induces a strong southerly in the middle troposphere, which mid-high-latitude storms may follow into the Arctic. In particular, the correlation between AO and the occurrence frequency of Pacific-RTDW events has strengthened since the early 1980s. This shift is attributed to the intensified Pacific storm-track (PST) activity intensity, which is possibly related to the phase transition of the Pacific decadal oscillation (PDO) and has induced stronger synoptic-scale eddy feedbacks to low-frequency flows since this period. Accordingly, stronger feedbacks of the synoptic-scale eddies could provide a favorable condition for the formation of such a dipole pattern associated with the AO, bolstering the connection between AO and Pacific-RTDW events. In contrast, the eddy feedback to the flow is not strong enough and is, therefore, unable to provide favorable conditions before this period due to the comparatively weak PST intensity. Significance Statement: The Arctic winter daily warming event may lead to more severe cold air outbreaks invading the Northern Hemisphere midlatitudes. We explored the climatic conditions favorable for the occurrence of Arctic winter daily warming events, thereby revealing that the correlated atmospheric circulation features a northwest–southeast dipole pattern. Additionally, since the early 1980s, the intensified Pacific storm-track activity is believed to have contributed to strengthening of the correlation between the Arctic Oscillation and the occurrence frequency of Arctic winter daily warming events. The findings here are expected to assist in prediction of future Arctic winter daily warming events.