Radiative Effects of Secondary Ice Enhancement in Coastal Antarctic Clouds

Abstract

Secondary ice production (SIP) commonly occurs in coastal Antarctic stratocumulus, affecting their ice number concentrations (Nice) and radiative properties. However, SIP is poorly understood and crudely parametrized in models. By evaluating how well SIP is captured in a cloud‐resolving model, with a high‐resolution nest within a parent domain, we test how an improved comparison with aircraft observations affects the modeled cloud radiative properties. Under the assumption that primary ice is suitably represented by the model, we must enhance SIP by up to an order of magnitude to simulate observed Nice. Over the nest, a surface warming trend accompanied the SIP increase; however, this trend was not captured by the parent domain over the same region. Our results suggest that the radiative properties of microphysical features resolved in high‐resolution nested domains may not be captured by coarser domains, with implications for large‐scale radiative balance studies over the Antarctic continent.

The impact of Secondary Ice Production on Arctic Stratocumulus

“…Interestingly, if BR is excluded from our simulations, the RS effect should be multiplied with a factor of 10 to obtain a good agreement with the observed ICNCs, i.e. the factor as in Young et al (2019). 445…”

“…The limited influence of RS in clouds with very few large raindrops to initiate this process is also quite conceivable. RS has also been found insufficient to explain the observed ICNCs in Antarctic stratocumulus clouds of similar temperature in Weather and Research Forecasting (WRF) simulations conducted by Young et al (2019). To reproduce the observations, they had to remove from the RS parameterization the liquid thresholds that allow RS activation only when sufficiently large 440 droplets are formed, and, further multiply the RS splinter production efficiency by a factor of 10.…”

“…Our results indicate that BR is likely a critical mechanism in Arctic stratocumulus clouds, where large drops are sparse and RS efficiency is limited. Thus a correct representation of this process in 490 models will likely alleviate some of the model deficiencies in representing cloud ice properties and hence the shortwave radiation budget (Young et al, 2019). As there have been significant advances in the development of laboratory instruments suitable for BR studies through the past decades, we highlight the need for new laboratory experiments with more realistic set-ups that focus on the BR mechanism.…”

Microphysics of Snowfall Over Coastal East Antarctica Simulated by Polar WRF and Observed by Radar

“…For domains with a resolution greater or equal than 9 km, the Kain‐Fritsch cumulus scheme has been activated. This physical package was set after consideration of previous evaluation studies (Bromwich et al, ; Deb et al, ; Listowski & Lachlan‐Cope, ; Young et al, ) and preliminary sensitivity tests over Adélie Land.…”

“…This physical package was set after consideration of previous evaluation studies (Bromwich et To help the simulation comparison, we provide in the following paragraphs a few elements of information about the five tested microphysical schemes. Further details regarding the primary and secondary ice generation are given in Listowski and Lachlan-Cope (2017) and Young et al (2019). Note that the performances of each scheme strongly depend upon the specific tuning of numerous parameters (Tapiador et al, 2019).…”