Impacts of Atmospheric River on Cloud Radiative Effects in Polar Regions

March 3, 2026

Recently, several papers investigating the impacts of Atmospheric Rivers (ARs) on cloud radiative effects in both the Arctic and Antarctic have been published. These efforts support CW3E’s Strategic Plan (Atmospheric Rivers and Extreme Precipitation Research, Prediction, and Applications) and strengthen AR research in Polar regions.

The paper entitled “Surface radiation trends at North Slope of Alaska influenced by large-scale circulation and atmospheric rivers” was recently published in Atmospheric Chemistry and Physics. The study was led by Dan Lubin (SIO), with co-authors Xun Zou (CW3E, SIO), Johannes Mülmenstädt (PNNL), Andrew Vogelmann (BNL), Maria Cadeddu (ANL), and Damao Zhang (PNNL).

Arctic amplification refers to the rapid warming of near-surface air temperatures across the Arctic over the past century, occurring at roughly twice the global average rate. This warming results from complex interactions among the ocean, atmosphere, and land. Using a 25-year record of surface radiation measurements from the ARM North Slope of Alaska site at Utqiaġvik, this paper finds clear warming in boreal fall and a reduction in net radiation during late summer. The late-summer decrease is mainly linked to reduced shortwave radiation caused by increasing cloud liquid water. Although these trends are small relative to natural variability, they indicate early emerging climate signals. Changes in large-scale circulation patterns, including ARs, appear to play a key role in driving these summertime changes (Fig. 1).

Figure 1. Results involving the role of atmospheric rivers (ARs); (a) the total AR count over NSA in each year, with the linear trend shown as a dotted line; (b–f) time series for the Late July interval showing the net radiation flux components and MWR-measured quantities for all data in light blue and with the AR days removed in orange. The mean value in each interval is shown as a dot and the error bars are plus and minus 1 standard deviation about the mean. The linear least-squares trend is shown as a dotted line. The three numbers in each panel are the linear change in the radiative flux between 1999 and 2024 (top), the Pearson correlation coefficient from ordinary least squares (middle) and the percent confidence level in trend detection from a Mann–Kendall test (bottom), but are for the trends with the ARs removed. Figure 5 from Lubin et al. (2026).

Citation:

Lubin, D., Zou, X., Mülmenstädt, J., Vogelmann, A., Cadeddu, M., & Zhang, D. (2026). Surface radiation trends at North Slope of Alaska influenced by large-scale circulation and atmospheric rivers. Atmospheric Chemistry and Physics, 26(1), 295-311. https://doi.org/10.5194/acp-26-295-2026

Two other papers entitled “Comparison of cloud and radiation measurements to models over the Southern Ocean at Escudero Station, King George Island” and “Observations of clouds and radiation over King George Island and implications for the Southern Ocean and Antarctica” were published late 2025 in Journal of Geophysical Research: Atmospheres. This investigation was mainly supported by collaborative research funded by NSF OPP and led by Penny Rowe (NWRA), with contributions from CW3E scientists Xun Zou, Zhenhai Zhang, and F. Martin Ralph, as well as Irina Gorodetskaya (CIIMAR), Robert A. Stillwell (NSF NCAR), Raul R. Cordero (University of Chile), David Bromwich (The Ohio State University), Steven Neshyba (University of Puget Sound), and Edgardo Sepulveda (University of Chile).

Clouds strongly influence radiation and warming over the Southern Ocean and Antarctic Peninsula. Using seven years (2017-2023) of cloud and radiation measurements at Escudero Station on King George Island (Fig. 2, Left), we evaluate ERA5 reanalysis and Polar WRF (PWRF) simulations. ERA5 overestimates summer downward shortwave radiation and underestimates downward longwave radiation, likely because cloud optical depth is too low rather than errors in temperature, humidity, or cloud phase. These biases also appear during AR events, while PWRF shows much smaller radiation errors (Fig. 2, Right). Observations reveal that clouds occur nearly all the time, with frequent low-level supercooled liquid clouds that strongly affect surface energy balance. Downward cloud radiative forcing cools the surface in summer but warms it in winter. During strong AR events, weaker shortwave cloud forcing is linked to higher summertime surface temperatures, highlighting the key role of clouds in Southern Ocean and Antarctic climate variability.

Figure 2. Left: Map of the Antarctic Peninsula showing the location of Escudero Station as well as domains 2 and 3 (D02 and D03) used in PWRF and the region used for atmospheric river detection (purple dashed line). The inset panel shows domain 1 (D01), the greater Antarctic region. Topography (colors; m) is based on elevation information from the Reference Elevation Model of Antarctica (REMA; Howat et al., 2019). Right: Downwelling radiative flux at the surface during an atmospheric river in summer over Escudero Station on King George Island. Panels (a–c) show time series of downwelling broadband radiation for ERA5 clear-sky simulations (ERA5 clear), ERA5 and PWRF fluxes for the scene view, and fluxes from measurements on King George Island, after averaging over an hour. The white regions of panels (a–c) indicate the timespan of the AR event. Panels (d–f) show box-and-whiskers plots for the event. The colors correspond to the legend. The mean is indicated by an asterisk, the median by a horizontal bar, the interquartile range by boxes, and the full range by whiskers. Figures 1 & 5 from Rowe et al. (2025a).

Citations:

Rowe, P. M., Zou, X., Gorodetskaya, I., Stillwell, R. A., Cordero, R. R., Bromwich, D., Zhang, Z., Ralph, F. M., & Neshyba, S. (2025). Comparison of Cloud and Radiation Measurements to Models Over the Southern Ocean at Escudero Station, King George Island. Journal of Geophysical Research: Atmospheres, 130(16). https://doi.org/10.1029/2025jd043563

Rowe, P. M., Zou, X., Gorodetskaya, I., Stillwell, R. A., Cordero, R. R., Sepulveda, E., Bromwich, D. H., Zhang, Z., Ralph, F. M., & Neshyba, S. (2025). Observations of Clouds and Radiation Over King George Island and Implications for the Southern Ocean and Antarctica. Journal of Geophysical Research Atmospheres, 130(18). https://doi.org/10.1029/2024jd042787