Cloud Phase Simulation at High Latitudes in EAMv2: Evaluation Using CALIPSO Observations and Comparison With EAMv1

Abstract

Clouds play an essential role in global climate through interactions with radiation and hydrological cycle. The extensive coverage and strong radiative effects make clouds an important modulator of the energy budget at the surface and top of the atmosphere. Cloud radiative effects are controlled by cloud optical depth and other optical properties that are closely related to cloud microphysical properties such as amount, size, shape, and thermodynamic phase of cloud hydrometeors (Curry & Ebert, 1992;Curry et al., 1996;Shupe & Intrieri, 2004). Cloud albedo is more sensitive to variations in cloud liquid water than cloud ice water. The shortwave radiative cooling effect due to liquid water usually dominates the net cloud radiative effect in mixed-phase clouds, highlighting the importance of cloud thermodynamic phase on cloud radiative forcing (Sun & Shine, 1994). In addition, differences in microphysical properties between liquid and ice are critical for global precipitation. Satellite observations have demonstrated that most of the Earth's precipitation originates from the ice phase and mixed-phase cloud processes, while warm rain mechanisms are more critical for precipitation over tropical and subtropical oceans (Field & Heymsfield, 2015;Heymsfield et al., 2020;Mülmenstädt et al., 2015). The distinct roles of cloud liquid and cloud ice on precipitation formation make cloud phase one of the key factors influencing the hydrological cycle in the Earth system. Moreover, the cloud liquid and ice microphysical properties in the present-day climate can also have a significant impact on the Arctic amplification (Middlemas et al., 2020) and future global climate change (Bjordal et al., 2020;Lohmann & Neubauer, 2018;Tsushima et al., 2006). For example, it has been found that the predicted Arctic amplification strength is highly sensitive to the ice particle size and number concentration of ice nucleating particles in the present-day environment (Tan & Storelvmo, 2019;Tan et al., 2022). Across the globe, if clouds in the present-day climate have a lower ice water amount, the phase transition from ice to liquid would be less significant in a future warmer climate, which would result in a weaker

Evaluating EAMv2 Simulated High Latitude Clouds Using ARM Measurements in the Northern and Southern Hemispheres

“…We note that the overestimated occurrence of large LWP in the Arctic is consistent with Zhang, Xie, et al. (2022), in which the CALIPSO simulator‐derived liquid cloud fraction is substantially overestimated against the CALIPSO‐GOCCP data. However, inconsistent results are shown in the ice phase evaluation.…”

“…The excessive clouds in the Arctic are consistent with Zhang, Xie, et al. (2022), where they also found that EAMv2 overestimates supercooled liquid clouds in the Arctic compared to the CALIPSO‐GOCCP data.…”

“…For simulated IWP, although Zhang, Xie, et al. (2022) shows a much‐improved ice phase cloud cover in EAMv2 compared to EAMv1, the evaluation in this study still indicates that EAMv2 underestimates cloud ice water as compared with ground‐based remote sensing retrievals at the NSA site. Such a discrepancy suggests that different instrument limitations must be considered in the model evaluation.…”

Ship‐Based Observations and Climate Model Simulations of Cloud Phase Over the Southern Ocean

“…The main model biases seen in E3SM include the underestimation of ice phase and the overestimation of liquid phase at temperatures between −40°C and 0°C for all cloudy samples. Even though previous studies have reported similar biases in E3SM using high‐latitudinal observations (Yang et al., 2021; M. Zhang et al., 2020, 2022), a unique contribution of this work is to investigate the latitudinal dependence of such model bias. The underestimation of ice phase and overestimation of liquid phase are found to be more severe at higher latitudes than lower latitudes, indicating a possible larger radiative bias for underestimating the amount of absorbed shortwave radiation at higher southern latitudes.…”

“…Even though previous studies have reported similar biases in E3SM using high-latitudinal observations (Yang et al, 2021;M. Zhang et al, 2020M. Zhang et al, , 2022, a unique contribution of this work is to investigate the latitudinal dependence of such model bias.…”