RT info:eu-repo/semantics/bachelorThesis
T1 Estudio de la incidencia de episodios de calima en Canarias mediante modelos climáticos globales
A1 Herrera Cruz, Cristina
K1 Aerosoles atmosfericos
K1 GCM
K1 CMIP6
K1 GFDL
K1 MIROC
AB At present, the study of atmospheric aerosols has aroused great interest, especially inplaces where, due to their geographical location, there are many invasions. One exampleis the Canary Islands, which suffers episodes of desert dust from the African continent.These episodes, known as calima, affect the radiative balance and cloud formation, aswell as influence human health and ecosystems.The study of desert dust intrusions has evolved over the years thanks to advances inobservational methods and numerical models. In the present study, the potential of theGCMs (Global Climate Models) of the new phase of CMIP (Coupled ModelIntercomparison Project), CMIP6, will be evaluated. For this purpose, the results of thesimulations of these models will be compared with the observations of recent past years.In particular, the only three models that have made daily data on dust concentrationsavailable, i.e. IPSL, GFDL and MIROC6, will be used. These three models allow us theanalysis of aerosol transport and generation through simulations.For the observations, the data studied are from MERRA version 2 (Modern-EraRetrospective analysis for Research and Applications). They are obtained from thereanalysis of space-based aerosol observations. For the simulated models and theobservations we worked with column dust concentrations (kg m-2) and in order to studythe incidence of calima episodes the data associated with a focused grid point in theCanary Islands was chosen.This study begins by studying the percentile associated with the concentrationcorresponding to an atmospheric aerosol episode, i.e. the 60th percentile. Once thepercentile was determined, using the information on dust episodes provided byMinisterio para la Transición Ecológica y el Reto Demográfico, the monthly meancolumn concentration, the number of days above the 60th percentile and the number ofdays above the 95th percentile were analysed for two periods: the historical period andthe future period. The historical period is from 1980 to 2009 and the future period isdivided into two, mid-century (2030-2059) and late century (2070-2099). In addition,the SSP (Shared Socioeconomic Pathways) scenarios from CMIP6 describing CO2concentrations in the future will be used for the future period.So first of all, the monthly averages of dust column concentrations in the historicalperiod for the three CMIP6 models and for the MERRA2 measurements are compared,which allows us to discard the IPSL model for future simulations, as its behaviour isquite far from the observed one. Then the monthly averages of dust columnconcentration in the future are analysed for the GFDL models in the SSP585 andSSP245 scenarios and MIROC6 in the SSP126, SSP245, SSP370 and SSP585scenarios. Since a general increase in the monthly mean dust column concentrations is observed, the number of days above the 60th and 95th percentile is studied to determinewhether this increase is due to the increased intensity of the episodes or the duration ofthese intrusions.For the historical period, the IPSL model does not represent the stationarity of theobservations and the number of days above the 60th percentile is much higher than forthe 95th percentile. Therefore, it can be said that the calima episodes were not toointense in the past. For the future, an increase in the number of days with dust intrusionsis generally observed for the two selected CMIP6 models, which indicates that theincrease in the monthly mean is due to the longer duration of the dust intrusions and, toa lesser extent, to the intensity. So, in order to obtain more information on this matter,this work was finalised by studying the future trends for MIROC and GFDL.A study of the trends in annual dust column concentrations shows a gradual increase,which can be associated with more dust episodes as well as with an increase in intensity.Consequently, the trend in the number of annual days of extreme events (95thpercentile) was analysed for both models and an increasing behaviour was observed.However, although the increase in desert aerosol concentrations can be related to theincrease in the number of these episodes, a study of the average dust concentrations forthe events in each year has been carried out. From this study, which turned out not to bestatistically significant, it is possible to conclude that it cannot be considered animportant cause for the growth of dust concentrations.Finally, it can be concluded, in first place, that the potential of the MIROC and GFDLmodels is favourable and consequently they postulate to be good simulators for thefuture. Furthermore, the future increase in frequency and intensity of desert dustintrusions is evident, in particular for the worst-case scenario concerning CO2concentrations. Therefore, under the initial conditions and assumptions proposed, thiswork reflects the worsening of the calima episodes in the Canary Islands and stimulatescontributing to the slowing down of climate change.
YR 2021
FD 2021
LK http://riull.ull.es/xmlui/handle/915/25738
UL http://riull.ull.es/xmlui/handle/915/25738
LA es
DS Repositorio institucional de la Universidad de La Laguna
RD 27-dic-2024