Collaborative Research: Systematic Evaluation and Further Improvement of Present Broadband Radiative Transfer Modeling Capabilities

陆地气候系统对辐射收支十分敏感。因此，准确了解大气-海洋耦合系统中的太阳辐射和热红外辐射，对于可靠的气候研究至关重要。 这种敏感性的一个例子是太阳常数下降1%可能导致冰河时代的建议。CO2倍增对辐射强迫的影响约为4 Wm-2，而由于对云的光学特性了解不足等原因，辐射模拟的不确定性可能大于这一值。在20世纪80年代和90年代，许多研究人员在开发和改进用于一般气候模式（GCM）的辐射传输方案方面取得了实质性进展，并发表了各种GCM辐射代码的相互比较。自那时以来，在光散射计算方法、云和气溶胶的光学和微物理特性的现场测量和实验室研究、气体吸收线参数和水蒸气连续吸收、各种海洋成分的光学特性以及求解辐射传输方程的数值方案的效率等方面取得了重大进展。迫切需要将上述进展纳入辐射传输建模能力。此外，在许多现有的辐射传输模式中，海洋和大气没有耦合。海水、溶解的有机物（所谓的黄色物质）和浮游植物对辐射的散射和吸收对加热最上层的水层产生影响，从而影响到海洋表面温度和大气-海洋混合层的深度等热特性和动力特性。 海洋对辐射的反射，包括波浪状的空气-水界面和白浪的影响，也会影响辐射的光谱特征和强度，从而影响大气中的辐射加热和冷却速率。总体目标是系统地评估和进一步提高目前的辐射传输建模能力。学术价值：研究成果将包括：1）系统量化上述辐射传输模型的潜在误差/不准确性; 2）将现有的辐射传输模拟能力扩展到大气-海洋耦合系统; 3）实现冰云和尘埃气溶胶的光谱一致性参数化; 4）开发和实现计算效率高的辐射传输解算器。更广泛的影响：研究工作将改进目前用于气候模型的辐射传输包，并对大气辐射传输和气候研究社区做出宝贵贡献。 此外，光散射建模和参数化的能力可以找到潜在的应用在其他领域，如遥感沙尘气溶胶和冰云的属性。相关的教育追求将集中在指导博士后研究人员，培训研究生，并开发教材。这一努力将有助于培训辐射传输和光散射学科的年轻研究人员，这是大气物理学的一个非常独特的分支。此外，RRTMG到课堂教学的整合将直接受益于大气科学的教育计划，特别是在大气辐射传输模拟的实践经验。

The terrestrial climate system is sensitive to the radiation budget. Thus, accurate knowledge about the solar and thermal infrared radiation in the coupled atmosphere-ocean system is critical to robust climate study. An example of this sensitivity is the suggestion that a 1% decrease in the solar constant could lead to an ice age. The effect of doubling CO2 on radiative forcing is approximately 4 Wm-2, whereas uncertainties in radiation simulations due to, for example, insufficient knowledge about the optical properties of clouds, may be larger than this value. During the 1980s and 1990s, many researchers made substantial progress in developing and improving radiative transfer schemes used in general climate models (GCMs), and various intercomparisons of GCM radiation codes were published. Since that time, significant progress has been made in light scattering computational methods, in-situ measurements and laboratory studies of the optical and microphysical properties of clouds and aerosols, gaseous absorption line parameters and the water vapor continuum absorption, optical properties of various oceanic constituents, and the efficiency of numerical schemes for solving radiative transfer equations. There is a pressing need to incorporate the aforesaid progress into radiative transfer modeling capabilities. Moreover, the ocean and atmosphere are not coupled in many existing radiative transfer models. The scattering and absorption of radiation by oceanic water, dissolved organic matter (the so-called yellow substance), and phytoplankton have an influence in heating the uppermost water layers, and consequently affect thermal and dynamic properties such as the sea surface temperature and depth of the mixed atmosphere-ocean layer. The reflection of radiation by the oceans, including the effects of a wavy air-water interface and whitecap, can also affect the spectral characteristics and magnitude of radiation and, thus, the radiative heating and cooling rates in the atmosphere. The overarching goal is to systematically evaluate and further improve current radiative transfer modeling capabilities. Intellectual Merit:The outcomes of the study will include 1) systematic quantification of the potential errors/inaccuracies of the aforesaid radiative transfer models, 2) extension of the current radiative transfer modeling capabilities to an atmosphere-ocean coupled system, 3) implementation of spectrally consistent parameterizations of ice clouds and dust aerosols, and 4) development and implementation of a computationally efficient radiative transfer solver.Broader Impacts:The research effort will improve the radiative transfer package currently used in climate models, and be a valuable contribution to the atmospheric radiative transfer and climate study communities. Furthermore, the light scattering modeling and parameterization capabilities can find potential applications in other areas such as remote sensing of dust aerosol and ice cloud properties. The associated educational pursuits will focus on mentoring a postdoc researcher, training a graduate student, and developing teaching materials. This effort will contribute to training young researchers in the discipline of radiative transfer and light scattering that is a quite unique branch of atmospheric physics. Furthermore, the integration of RRTMG into classroom teaching will directly benefit the educational program in atmospheric sciences, particularly, in hands-on experience in atmospheric radiative transfer simulation.