Tesis Magíster
Radiación solar y vapor de agua; implicancias en el ciclo hidrológico y atmósfera terrestre bajo forzamiento radiactivo por CO2
Solar radiation and water vapor; implications in the hydrologic cycle and earth atmosphere under CO2 radiative forcing
Autor
Moreno Rudloff, Valeria Viviana
Institución
Resumen
In the past 65 million years, the Early Eocene (~ 56 - 48 mya) is considered the warmest geological period on Earth. Paleoclimate records show maximum sea surface temperatures around 35ºC in the tropics and mean annual temperatures higher than 14ºC at the poles, which suggests that between poles and subtropics there is a difference from 0 to 20ºC -considering uncertainties- (Lunt et al., 2012), knowns as the meridional low-gradient problem. Tested in many General Circulation Models (GCM), a radiative CO2 forcing up to 1000ppm does not perfectly reproduce the temperature gradients suitable for paleoclimatic records. Possibly, there are some global radiative mechanisms that are not correctly represented, and the hydrologic cycle response it seems the key within the GCMs. Therefore, this study explores the sensitivity of the PlaSim (GCM from the University of Hamburg) by modifying CO2 concentration and the short-wave radiation absorption due to water vapor. According to Collins et al. (2006), water vapor absorption parameters have conceptual and numerical discrepancies between models, besides the contribution in the greenhouse effect and the atmospheric structure and precipitation regime. The investigation corroborate that high concentrations of CO2 decrease meridional temperature gradient due to an increase of meridional heat transport under extreme greenhouse conditions. However, the meridional temperature gradient also decreases in response to a decrease in the water vapor absorption parameter, due to a lower cooling at midlatitudes associated with greater cloud patterns and static instability. A decrease in the water vapor absorption parameter has remarkable consequences in the whole hydrologic cycle, particularly in the increase in global precipitation and the increase in the atmospheric efficiency at turn water vapor into precipitation under CO2 radiative forcing. The key lies in the generalized instability of the atmosphere (relative warming of the lower troposphere), which allows a greater convective mass flow (mainly in mid latitudes) thus stimulate cloud formation and precipitation. PFCHA-Becas PFCHA-Becas