By David Bromwich et al.
Key messages from
Winter Targeted Observing Periods during the Year of Polar Prediction in the Southern Hemisphere (YOPP-SH)
David Bromwich (The Ohio State University), T. J. Anurose, Shweta Bhati, Margaret A. Hendry, Garry Hayman, Hamish Gordon, Paul Field, Saji Mohandas, Heather Rumbold, Prafull Yadav, Narendra Gokul Dhangar, Avinash Parde, Sandeep Wagh, Sachin Ghude, Andrew N. Ross, Daniel Smith, Stephen Dorling, John P. George, V. S. Prasad, and M. Ravichandran. Published online in BAMS, September 2024. For the full, citable article, right click the title link for options.
The Polar Prediction Project (PPP) was a 10-yr (2013–22) initiative of the World Meteorological Organization (WMO)’s World Weather Research Programme (WWRP) aimed at significantly improving weather and environmental prediction and services for the polar regions on time scales up to seasons. Its flagship activity was the Year of Polar Prediction (YOPP). PPP-YOPP officially concluded at the end of 2022. As part of YOPP, the YOPP in the Southern Hemisphere (YOPP-SH) focused on prediction and services for Antarctica and the Southern Ocean. YOPP-SH started in 2015 and continued until the end of 2024. A special observing period (SOP) during austral summer was conducted from November 16, 2018 to February 15, 2019.
The YOPP-SH community then decided that atmospheric predictability during austral winter should also be explored. Part of the motivation was the increasing evidence of rapid climate change impacting Antarctica, signified by low sea ice coverage since 2016. An additional motivation was the growing interest in year-round scientific investigations and the associated support needed. Consequently, a new SOP from April 16 to August 31, 2022 was organized. In view of the limited personnel and physical resources available during the winter, a modified observing strategy from the summer was developed. Under the SOP umbrella, enhanced radiosonde releases and in situ process observations were focused on targeted observing periods (TOPs) of 5–10-days duration each, fashioned after the TOP conducted in the Arctic.
The TOPs were focused on the scientific goals of improving numerical weather prediction (NWP) via enhanced radiosonde observations, better characterizing large oceanic cyclones and atmospheric rivers (ARs) impacting coastal Antarctica, and testing and enhancing the prediction of clouds and precipitation by weather forecast models. Based on the summer experiment, efforts were made to entrain lower-latitude stations with the aim of improving the forecasting for major events affecting Antarctica from the north. Twenty-four stations participated, with observations from 14 national Antarctic programs and weather services—namely, Argentina, Australia, Chile, China, France, Germany, Italy, Japan, Korea, New Zealand, Portugal, Ukraine, United Kingdom, and the United States.
Based on extensive consultations with the YOPP-SH community, seven TOPs were conducted during the winter SOP. Four TOPs involved both the Antarctic Peninsula and East Antarctica, so-called pan-Antarctic or circum-Antarctica, that are most effective for improving NWP in the Southern Ocean and Antarctica. Two considered East Antarctica and one the Antarctic Peninsula. The Antarctic Peninsula TOP5 immediately preceded the second East Antarctic TOP6, so together they form a fifth pan-Antarctic TOP. A total of ∼1,100 additional radiosondes were launched, more than doubling the routine number of soundings at these stations. High-time-resolution radiosonde data during the TOPs were collected from around 60 radiosonde stations and 2 ships in the Antarctic, sub-Antarctic, and surrounding landmasses by the National Center for Atmospheric Research (NCAR) gathering the transmissions from the Global Telecommunications System (GTS). Data that did not get on the GTS from the participating stations were collected from the station operators to make the dataset as complete as possible. These observations together with related data are archived at the Antarctic Meteorological Research and Data Center (https://amrdcdata.ssec.wisc.edu/group/year-of-polar-prediction-in-the-southern-hemisphere).
The additional radiosonde ascents during the seven TOPs are actively being evaluated for their impact on forecast skill via data denial experiments with the goal of refining the observing system to improve NWP for winter conditions, which is becoming steadily more important for Antarctic science and operations. In addition, extensive observations focusing on clouds and precipitation, primarily during ARs, are being applied to refine model microphysical parameterizations for the ubiquitous mixed-phase clouds that frequently impact coastal Antarctica. Parallel investigations are broadening the scope and impact of YOPP-SH winter SOP. Studies of the Antarctic tourist industry’s use of weather forecasts show the scope for much greater awareness of the availability of forecast products and the skill they exhibit. Conversely, tailoring the weather information for this group of users would further promote the recently advanced forecast skill. There is also the prospect of the tourist industry being actively engaged in better forecast delivery by providing observations of current weather conditions. The community-organized Sea Ice Prediction Network (SIPN) South collected and analyzed projections of the sea ice growth during winter and revealed that the forecast skill several months ahead is superior to that of the sea ice contraction phase during austral summer.
Until now, the YOPP-SH investigations have had little direct impact on the practices of the global forecasting centers (i.e., the research-to-operations connection is yet to be realized). The Polar Coupled Analysis and Prediction for Services (PCAPS) program is addressing this shortcoming by engaging with the European Centre for Medium-Range Weather Forecasts (ECMWF), the Australian Bureau of Meteorology, the National Weather Service of Argentina, and probably additional global weather centers. PCAPS is a new initiative of the WWRP to follow on from the PPP and focuses on coupled atmosphere–ocean–sea ice analysis and prediction. It spans 2024–28 with a major emphasis on service delivery (https://www.wwrp-pcaps.net/).
METADATA
![David Bromwich (center, with blue shirt) on a dog walk with his three Norfolk Terriers and other canine enthusiasts. “Notice how small the Norfolks are in relation to the adolescent Great Dane to my left.” [Photo courtesy Sandra Augustine]](https://headlines.ametsoc.org/wp-content/uploads/2026/02/Bromwich_Personal_Picture2.jpeg "Bromwich_Personal_Picture2")
“I grew up in Australia, which is the land of extremes. The weather was a primary focus for me. Also, I was looking for a practical application for my training in physics and mathematics. Finally, I was intrigued by the novelty of the weather and climate of the Antarctic and the potential for impactful discoveries. So, polar meteorology really fit my interests.”
—David Bromwich, The Ohio State University
A Brief Conversation
with the Author
Headlines: What would you like readers to learn from this article?
David Bromwich (The Ohio State University): How well the international Antarctic community came together for the benefit of all.
Headlines: How did you become interested in the topic of this article?
DB: Through our research with the Weather Research and Forecasting (WRF) model in the polar regions that led to our development of the polar version of WRF, which we call Polar WRF.
Headlines: What surprised you the most about the work you document in this article?
DB: Just how chaotic the winter atmosphere is in the stormy latitudes of the coastal regions of Antarctica. Improving the forecasts is incremental work.
Headlines: What was the biggest challenge you encountered while doing this work?
DB: Ensuring the volunteer contributions of so many generous people were recognized and providing continued enthusiasm for this major undertaking.
“We need to complete studying the impact of all the additional observations on the weather forecasts for the Southern Ocean and Antarctica. Then the challenges will be to enhance the practices of the global forecasting centers and devising practical solutions to refining the winter observations for this remote region.”
—David Bromwich, The Ohio State University
