Understanding responses of summer continental daily temperature variance to perturbations in the land surface evaporative resistance
Understanding responses of summer continental daily temperature variance to perturbations in the land surface evaporative resistance
复制标题
了解夏季大陆日气温变化对地表蒸发阻力扰动的响应
DOI：
10.1175/jcli-d-21-1011.1
复制
发表时间：
2022
影响因子：
4.9
通讯作者：
Laguë, Marysa M.
中科院分区：
文献类型：
--
作者：
Kong, Wenwen;McKinnon, Karen A.;Simpson, Isla R.;Laguë, Marysa M.
了解陆地表面条件和大气环流对大陆日温度变化的作用是改善极端温度预测的关键。蒸发阻力（rs）是土地覆盖类型的函数，反映了水分蒸发或蒸腾的难易程度，是陆-气相互作用的强有力控制因素。本研究探讨rsperturbations对夏季每日温度变化的影响，使用简单的土地界面模式（SLIM）模拟，forrsonly，全球土地覆盖从森林到作物/草地的转换。减少会导致全球变冷。冷却是较大的潮湿地区和较弱的干燥地区，主要是由于在短波辐射（SW）和潜热通量（LH）的扰动。由于更大的陆面蒸发，减少的云量增加，从而减少了大多数陆地地区的西南气流。当rs减少时，较潮湿的地区会经历强烈的蒸发冷却，而较干燥的地区会变得更加潮湿，从而经历较少的冷却。热平流通过阻尼SW和LH的组合影响进一步塑造温度响应。温度方差在干旱地区增加，在湿润地区减少。温度方差的变化在很大程度上可以从SW和LH的组合方差的变化来解释，包括SW和LH的协方差变化的重要贡献。相比之下，热平流方差的变化的影响主要影响北方半球中纬度地区。Significance StatementThis study aims to better understand processes governing daily near-surface air temperature variance over land.我们使用一个理想化的建模框架来探索陆地表面蒸发阻力（一个参数，控制它是多么难从表面蒸发水）对夏季每日温度变化的影响。我们发现，在全球陆地表面的蒸发阻力的均匀减少导致的温度方差的变化，可以预测从短波辐射和潜热通量的组合方差的变化。水平平流的变化对改变北方中纬度地区的温度变化是很重要的。我们的研究结果揭示了预测温度变化的特性作为表面条件的函数。
Understanding the roles of land surface conditions and atmospheric circulation on continental daily temperature variance is key to improving predictions of temperature extremes. Evaporative resistance (rs, hereafter), a function of the land cover type, reflects the ease with which water can be evaporated or transpired and is a strong control on land–atmosphere interactions. This study explores the effects ofrsperturbations on summer daily temperature variance using the Simple Land Interface Model (SLIM) by mimicking, forrsonly, a global land cover conversion from forest to crop/grassland. Decreasingrscauses a global cooling. The cooling is larger in wetter areas and weaker in drier areas, and primarily results from perturbations in shortwave radiation (SW) and latent heat flux (LH). Decreasingrsenhances cloud cover due to greater land surface evaporation and thus reduces incoming SW over most land areas. Whenrsdecreases, wetter areas experience strong evaporative cooling, while drier areas become more moisture-limited and thus experience less cooling. Thermal advection further shapes the temperature response by damping the combined impacts of SW and LH. Temperature variance increases in drier areas and decreases in wetter areas asrsdecreases. The temperature variance changes can be largely explained from changes in the combined variance of SW and LH, including an important contribution of changes in the covariance of SW and LH. In contrast, the effects of changes in thermal advection variance mainly affect the Northern Hemisphere midlatitudes.Significance StatementThis study aims to better understand processes governing daily near-surface air temperature variance over land. We use an idealized modeling framework to explore the effects of land surface evaporative resistance (a parameter that controls how hard it is to evaporate water from the surface) on summer daily temperature variance. We find that a uniform decrease of evaporative resistance across the global land surface causes changes in the temperature variance that can be predicted from changes in the combined variance of shortwave radiation and latent heat flux. The variance of horizontal advection is important in altering the temperature variance in the Northern Hemisphere midlatitudes. Our findings shed light on predicting the characteristics of temperature variability as a function of surface conditions.