Dee Sylvia G, Nusbaumer Jesse, Bailey Adriana, Russell James M, Lee Jung-Eun, Konecky Bronwen, Buenning Nikolaus H, Noone David C
Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI 02912.
Brown University, Institute at Brown for Environment and Society, Providence, RI 02912.
J Geophys Res Atmos. 2018 Jul 27;123(14):7254-7270. doi: 10.1029/2017JD027915. Epub 2018 Jun 19.
General circulation models (GCMs) predict that the global hydrological cycle will change in response to anthropogenic warming. However, these predictions remain uncertain, in particular for precipitation [IPCC, 2013]. Held and Soden [2006] suggest that as lower-tropospheric water vapor concentration increases in a warming climate, the atmospheric circulation and convective mass fluxes will weaken. Unfortunately, this process is difficult to constrain, as convective mass fluxes are poorly observed and incompletely simulated in GCMs. Here, we demonstrate that stable hydrogen isotope ratios in tropical atmospheric water vapor can trace changes in temperature, atmospheric circulation and convective mass flux in a warming world. We evaluate changes in temperature, the distribution of water vapor, vertical velocity () and advection, and water isotopes in vapor ( ) in water isotopeenabled GCM experiments for modern vs. high atmospheres to identify spatial patterns of circulation change over the tropical Pacific. We find that slowing circulation in the tropical Pacific moistens the lower troposphere and weakens convective mass flux, both of which impact the of water vapor in the mid-troposphere. Our findings constitute a critical demonstration of how water isotope ratios in the tropical Pacific respond to changes in radiative forcing and atmospheric warming. Moreover, as changes in can be observed by satellites, our results develop new metrics for the detection of global warming impacts to the hydrological cycle and, specifically, the strength of the Walker Circulation.
通用循环模型（GCMs）预测，全球水文循环将因人为变暖而发生变化。然而，这些预测仍然存在不确定性，尤其是在降水方面[政府间气候变化专门委员会，2013年]。赫尔德和索登[2006年]指出，在气候变暖的情况下，随着对流层低层水汽浓度的增加，大气环流和对流质量通量将会减弱。不幸的是，这一过程难以得到约束，因为对流质量通量在通用循环模型中的观测数据很少，模拟也不完全。在此，我们证明，热带大气水汽中稳定氢同位素比值可以追踪气候变暖背景下温度、大气环流和对流质量通量的变化。我们在启用了水同位素的通用循环模型实验中，评估了现代与高排放大气中温度、水汽分布、垂直速度（）和对流以及水汽中的水同位素（）的变化，以确定热带太平洋上空环流变化的空间模式。我们发现，热带太平洋环流减缓会使对流层低层变得湿润，并削弱对流质量通量，这两者都会影响对流层中层水汽的。我们的研究结果为热带太平洋水同位素比值如何响应辐射强迫和大气变暖的变化提供了关键的证明。此外，由于卫星可以观测到的变化，我们的结果为检测全球变暖对水文循环的影响，特别是沃克环流的强度，开发了新的指标。
