Model simulations are highly sensitive to the formulation of the atmospheric mixing process or entrainment in the deep convective parameterizations used in their atmospheric component. In this paper, we have implemented stochastic entrainment in the deep convection scheme of NCAR CAM5 and analyzed the improvements in model simulation, focusing on the South Asian Summer Monsoon (SASM), as compared to the deterministic entrainment formulation in the default version of the model. Simulations using stochastic entrainment (StochCAM5) outperformed default model simulations (DefCAM5), as inferred from multiple metrics associated with the SASM. StochCAM5 significantly alleviated some of the longstanding SASM biases seen in DefCAM5, such as precipitation pattern and magnitude over the Arabian Sea and western Equatorial Indian ocean, early monsoon withdrawal, and the overestimation in the frequency of light precipitation and the underestimation in the frequency of large-to-extreme precipitation. Related SASM dynamical and thermodynamical features, such as Somali Jet, low-level westerly winds, and meridional tropospheric temperature gradient (MTTG), are improved in StochCAM5. Further, the simulation of monsoon intra-seasonal oscillation (MISO), Madden Julian Oscillation (MJO), and equatorial Kelvin waves are improved in StochCAM5. Many essential climate variables, such as shortwave and longwave cloud forcing, cloud cover, relative and specific humidity, and precipitable water, show significant improvement in StochCAM5.

模型模拟对大气混合过程的公式或在其大气成分中使用的深对流参数化中的夹带高度敏感。在本文中，我们在 NCAR CAM5 的深对流方案中实施了随机夹带，并分析了模型模拟的改进，重点是南亚夏季风 (SASM)，与模型默认版本中的确定性夹带公式相比. 从与 SASM 相关的多个指标推断，使用随机夹带 (StochCAM5) 的模拟优于默认模型模拟 (DefCAM5)。StochCAM5 显着减轻了 DefCAM5 中一些长期存在的 SASM 偏差，例如阿拉伯海和赤道印度洋西部的降水模式和幅度，季风提前撤退，小降水频率高估，大到极端降水频率低估。StochCAM5 改进了相关的 SASM 动力学和热力学特征，例如索马里急流、低空西风和经向对流层温度梯度 (MTTG)。此外，在 StochCAM5 中改进了季风季节内振荡 (MISO)、马登朱利安振荡 (MJO) 和赤道开尔文波的模拟。许多基本气候变量，例如短波和长波云强迫、云量、相对湿度和比湿度以及可降水量，都显示出 StochCAM5 的显着改善。StochCAM5 改进了相关的 SASM 动力学和热力学特征，例如索马里急流、低空西风和经向对流层温度梯度 (MTTG)。此外，在 StochCAM5 中改进了季风季节内振荡 (MISO)、马登朱利安振荡 (MJO) 和赤道开尔文波的模拟。许多基本气候变量，例如短波和长波云强迫、云量、相对湿度和比湿度以及可降水量，都显示出 StochCAM5 的显着改善。StochCAM5 改进了相关的 SASM 动力学和热力学特征，例如索马里急流、低空西风和经向对流层温度梯度 (MTTG)。此外，在 StochCAM5 中改进了季风季节内振荡 (MISO)、马登朱利安振荡 (MJO) 和赤道开尔文波的模拟。许多基本气候变量，例如短波和长波云强迫、云量、相对湿度和比湿度以及可降水量，都显示出 StochCAM5 的显着改善。