Southern Ocean precipitation: Toward a process‐level understanding

Abstract

Large differences continue to exist between current precipitation products over the Southern Ocean (SO). This limits our ability to close the hydrological cycle over the SO and Antarctica, as well as limiting our understanding of a range of climatological and meteorological processes. This uncertainty arises from the absence of long-term, high-quality surface observational records of precipitation suitable for evaluation across a range of temporal and spatial scales. We have no "truth" for precipitation across this region that covers $15% of the Earth's surface. These differences extend to spatial and temporal distributions and trends. Precipitation products that have been calibrated and evaluated against established observations in the Northern Hemisphere potentially may be biased due to fundamental differences in the dynamics and microphysics over the remote SO. This review first considers recent advances in our understanding of the precipitation of the SO, including spatial and temporal variability, thermodynamic phase, and response to climate drivers. We then examine several commonly used precipitation products derived from satellite observations (both passive and active), reanalyses, and merged products. Where possible, we examine the skill of these products across a range of precipitation processes that commonly occur across the SO. Finally, we look briefly at the potential of new resources, such as dual-polarized radars and maritime disdrometers, that can be used in field campaigns specifically designed to observe precipitation at the process level, and ultimately used to evaluate precipitation products over the SO.

Southern Ocean Low Cloud and Precipitation Phase Observed During the Macquarie Island Cloud and Radiation Experiment (MICRE)

“…But given the potential for interannual variability, it will take several more years of data to be confident that these differences represent real seasonal variations. Furthermore, the longerterm data collected at Macquarie Island and other SO sites suggest that the climate of the region is changing (e.g., Adams, 2009;Fogt & Marshall, 2020;Manton et al, 2020;Siems et al, 2022), and relating how climate changes are affecting cloud properties (i.e., cloud feedbacks) at Macquarie would be of great value. This might be done, for example, by estimating cloud feedbacks following the approach in Terai et al (2019) that has been applied to measurements at several Northern Hemisphere ARM sites.…”

“…The station is situated in the middle of the SO storm track and is a suitable location to observe SO cloud and precipitation systems carried by prevailing westerly winds. The data collected from this site have been used in many studies of the climate over the SO in the region south of New Zealand and Tasmania (e.g., De Lisle, 1965; Streten, 1988), including in more recent years wind shear and the thermodynamic structure of the lower troposphere (Hande et al., 2012; Lang et al., 2018) and precipitation (Adams, 2009; Manton et al., 2020; Siems et al., 2022).…”

Characterizing Precipitation and Improving Rainfall Estimates Over the Southern Ocean Using Ship‐Borne Disdrometer and Dual‐Polarimetric C‐Band Radar

“…Clouds and precipitation over the Southern Ocean (SO) play a critical role in influencing freshwater fluxes, air‐sea fluxes, and radiative properties of the region (Caldeira & Duffy, 2000; Pauling et al., 2016; Siems et al., 2022; Wood, 2012). The SO is characterized by fewer land masses and anthropogenic aerosol sources than the Northern Hemisphere, creating a more pristine environment and a distinct mix of cloud and precipitation processes.…”

Characteristics and Variability of Precipitation Across Different Sectors of an Extra‐Tropical Cyclone: A Case Study Over the High‐Latitudes of the Southern Ocean

“…Fundamentally these differences arise from a lack of high‐quality observations suitable for evaluation across a range of temporal and spatial scales. Observations from isolated island sites are often intermittent and can suffer from orographic effects (Manton et al., 2020), and sparse ship observations are often of limited quality due to limited instrumentation, the harsh physical environment and sampling biases (Siems et al., 2022).…”

“…• Distinctive characteristics of precipitation across different sectors of an extra-tropical cyclone are observed • Largest precipitation was recorded during the cyclone period where its phases were largely constituted of mixed-phase and snow • WRF reproduced the frontal precipitation intensity, while it is underestimated during the cyclone period (Manton et al, 2020), and sparse ship observations are often of limited quality due to limited instrumentation, the harsh physical environment and sampling biases (Siems et al, 2022).…”