Understanding Heat-transfer Regimes in Past, Present and Future Climates

地球气候是热传递的产物，因为随着时间的推移，热能收益的变暖效应，包括降水中释放的潜热，必须由相等的热损失来平衡，才能在任何给定的区域实现持久的气候状态。大气层柱可以通过辐射通过顶部和底部传递热能，例如，当大气柱冷却时，通过向太空发射红外线辐射，以及通过地球表面的蒸发和热传导。横向热传递也很关键，因为在热带地区，地球从太阳接收的能量比辐射回太空的能量多，而两极附近的情况正好相反。因此，热带地区必须向两极输出热能，以平衡两个地区的收支平衡。该奖项下的工作旨在了解低、中、高纬度地区的大气热传输，同时考虑季节周期中热传输的变化以及较暖和较冷气候之间的热传输差异。例如，对现代气候的模拟显示出纬度热平衡的强烈季节变化，夏季辐射在很大程度上平衡了北半球中纬度地区的局部蒸发和地表热传导，而其他季节的横向热输送更为突出。在对“雪球地球”气候的模拟中，情况截然不同，在那里，横向输送在全球大部分地区全年都很明显。通过对现有模拟的分析和使用多种模式配置的新颖模拟，探讨了决定不同气候中大气热平衡并在气候状态之间转换期间驱动热平衡变化的潜在机制。热传输在维持地球气候方面起着至关重要的作用，考虑到需要更好地了解气候系统如何工作以及在温室气体增加和气溶胶污染变化的影响下，对该主题的研究具有社会价值。该项目还为一名研究生和一名本科生提供支持和培训，后者是通过一个校园范围的计划招募的，该计划致力于增加少数族裔在科学研究中的参与。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Earth's climate is a product of heat transfer, as the warming effect of heat energy gains, including the latent heat released in precipitation, must over time be balanced by equal heat losses to achieve a persistent climate state in any given region. An atmospheric column can transfer heat energy through its top and bottom by radiation, for instance when it cools by emitting infrared radiation to space, and by evaporation and thermal conduction at the Earth's surface. Lateral heat transfer is also critical, as in the tropics the Earth receives more energy from the sun than it radiates back to space and the opposite is true near the poles. Thus the tropics must export heat energy to the poles to balance the budgets of both regions. Work under this award seeks to understand atmospheric heat transfer in low, middle, and high latitudes, considering both changes in heat transfer over the the seasonal cycle and differences in heat transfer between warmer and colder climates. For example simulations of modern climate show strong seasonal variations in latitudinal heat balances, with radiation largely balancing local evaporation and surface heat conduction in the middle latitudes of the Northern Hemisphere in summer, while lateral heat transfer is more prominent in other seasons. The situation is quite different in simulations of the "snowball earth" climate, where lateral transfer is prominent throughout the year over most of the globe. The underlying mechanisms that determine atmospheric heat balances in different climates, and drive changes in heat balances during transitions between climate states, are explored through analysis of existing simulations and through novel simulations using a variety of model configurations.Heat transport plays an essential role in maintaining Earth's climate, and research on the topic has societal value given the need to better understand how the climate system works and how it is likely to change under the influence of greenhouse gas increases and changes in aerosol pollution. The project also provides support and training for a graduate student and an undergraduate, the latter recruited through a campus-wide program dedicated to increasing participation of underrepresented minorities in scientific research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.