An assessment of the radiative effects of ice supersaturation based on in situ observations Geophysical Research Letters

We use aircraft observations combined with the reanalysis data to investigate the radiative effects of ice supersaturation (ISS). Our results show that although the excess water vapor over ice saturation itself has relatively small radiative effects, mistaking it as ice crystals in climate models would lead to considerable impacts: on average, +2.49 W/m2 change in the top of the atmosphere (TOA) radiation, −2.7 W/m2 change in surface radiation, and 1.47 K/d change in heating rates. The radiative effects of ISS generally increase with the magnitudes of supersaturation. However, there is a strong dependence on the preexisting ice water path, which can even change the sign of the TOA radiative effect. It is therefore important to consider coexistence between ISS and ice clouds and to validate their relationship in the parameterizations of ISS in climate models.

本研究结合飞机观测与再分析资料，探究冰面过饱和（ISS）的辐射效应。研究结果表明，尽管冰饱和状态下的过量水汽本身的辐射效应相对较弱，但在气候模式中将其误判为冰晶，会带来显著影响：平均而言，大气顶（TOA）辐射变化为+2.49 W/m²，地表辐射变化为-2.7 W/m²，加热率变化为1.47 K/d。冰面过饱和的辐射效应通常随过饱和度的增大而增强，但却强烈依赖于预先存在的冰水路径，其甚至可以改变大气顶辐射效应的正负符号。因此，在气候模式的冰面过饱和参数化方案中，考虑冰面过饱和与冰云的共存状态，并验证二者的相关关系，具有重要意义。