Anmerkungen:
Kumulative Dissertation, enthält Zeitschriftenaufsätze
Tag der Verteidigung: 26.01.2022
Zusammenfassungen in deutscher und englischer Sprache
Beschreibung:
Air temperature and surface temperature are shaped by the balance among various energy flows. Their main heating source is solar radiation that partitions into different forms of energy, depending on the evaporative condition and vegetation characteristics of the surface. Usually, evaporation and vegetation induce cooler temperatures. Previous studies showed that surface and air temperature carry similar information in their mean state, but a limited number of studies consider differences in their diurnal variations. My overarching goal is to determine if and how surface and air temperature respond differently to evaporation and what is the role of vegetation in altering these responses. To quantify these responses I develop a novel index called warming rate that accounts for solar radiation. My analysis is based on observations from multiple FLUXNET sites across different evaporation and vegetation regimes along with the continental scale of ERA5 reanalysis data. I developed two models for surface and air temperature diurnal variation to understand the physical mechanisms shaping them. Findings show that the daytime warming of surface temperature reduces strongly on evaporative days but not for air temperature. Weaker responses of air temperature are found to link with the diurnal growth of the atmospheric boundary layer height. In the forest, the diurnal variation of air temperature as well as surface temperature responds weakly to evaporation due to high aerodynamic conductance. These findings have implications when quantifying the impact of deforestation and water stress in the ecosystem, using surface and air temperatures. Differences between surface and air temperature during daytime and their physical interpretation should be considered when using them as proxies of each other. Discerning these differences could benefit the understanding of the land-atmosphere system’s responses to global change, such as drought and deforestation.