Melo Aguilar, Camilo Andrés

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First Name
Camilo Andrés
Last Name
Melo Aguilar
Universidad Complutense de Madrid
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Now showing 1 - 6 of 6
  • Publication
    The Role of Internal Variability in ITCZ Changes Over the Last Millennium
    (American Geophysical Union, 2022-02-10) Roldán Gómez, Pedro J.; González Rouco, J. Fidel; Melo Aguilar, Camilo Andrés; Smerdon, J. E.
    Tropical hydroclimate is modulated by the position and intensity of the Intertropical Convergence Zone (ITCZ). Reconstructions and simulations of the Last Millennium (LM) suggest latitudinal variations of the ITCZ that impact the hydroclimate over large regions of the world. These ITCZ shifts have been generally linked to external radiative forcing, but analyses of the Community Earth System Model - Last Millennium Ensemble (CESM-LME) demonstrate a significant contribution of internal variability over multidecadal and centennial timescales. In contrast to changes driven by external forcing, which are associated with an asymmetric warming between the Northern and Southern Hemispheres, the contribution of internal variability in the CESM-LME is associated with cooling and warming of the eastern Pacific. While external forcing remains the main driver of ITCZ changes in the Atlantic basin, the contribution of internal variability in the CESM-LME exceeds that of the forcing for the Pacific and Indian Ocean basins. Plain Language Summary The Intertropical Convergence Zone (ITCZ) is a wide region of increased precipitation around the Equator. The position of the ITCZ changes over time. It moves to the north during summer in the Northern Hemisphere and to the south during boreal winter. In addition to these seasonal shifts, the ITCZ also changes over longer timescales. We have used a climate model to analyze ITCZ shifts over the Last Millennium. We have found that changes in the positioning of the ITCZ over the Atlantic Ocean are mainly linked to variations in solar luminosity and volcanic events, while for the Pacific and Indian Ocean, internally driven fluctuations in atmosphere and ocean states are dominant. The understanding of the mechanisms behind ITCZ shifts allows for a better assessment of tropical hydroclimatic events, such as persistent droughts and floods that are associated with alterations in the intensity and duration of tropical monsoons, as well as for better understanding its responses under intensified climate change conditions.
  • Publication
    European warm-season temperature and hydroclimate since 850 CE
    (IOP Publishing Ltd, 2019-08) González Rouco, J. Fidel; Melo Aguilar, Camilo Andrés
    The long-term relationship between temperature and hydroclimate has remained uncertain due to the short length of instrumental measurements and inconsistent results from climate model simulations. This lack of understanding is particularly critical with regard to projected drought and flood risks. Here we assess warm-season co-variability patterns between temperature and hydroclimate over Europe back to 850 CE using instrumental measurements, tree-ring based reconstructions, and climate model simulations. We find that the temperature–hydroclimate relationship in both the instrumental and reconstructed data turns more positive at lower frequencies, but less so in model simulations, with a dipole emerging between positive (warm and wet) and negative (warm and dry) associations in northern and southern Europe, respectively. Compared to instrumental data, models reveal a more negative co-variability across all timescales, while reconstructions exhibit a more positive co-variability. Despite the observed differences in the temperature–hydroclimate covariability patterns in instrumental, reconstructed and model simulated data, we find that all data types share relatively similar phase-relationships between temperature and hydroclimate, indicating the common influence of external forcing. The co-variability between temperature and soil moisture in the model simulations is overestimated, implying a possible overestimation of temperature-driven future drought risks.
  • Publication
    Near-surface soil thermal regime and land-air temperature coupling: A case study over Spain
    (John WiIley & Sons LTD, 2022-04-29) Melo Aguilar, Camilo Andrés; González Rouco, J. Fidel; Steinert, Norman; Beltrami, Hugo; Cuesta Valero, Francisco José; García García, Almudena; García Pereira, Félix; García Bustamante, Elena; Roldán Gómez, Pedro J.; Schmid, Thomas; Navarro, Jorge
    Understanding the near-surface soil thermal regime and its connection to the atmospheric state is important for the assessment of several climate-related processes. However, the lack of in situ soil temperatures measurements limits the analysis of such processes. In this study, we have developed a quality-controlled soil temperature database for Spain that consists of 39 sites spanning from 1987 to 2018. We have used this database to assess the near-surface soil thermal regime. Likewise, we evaluate at seasonal to multidecadal timescales the land-air temperature coupling over Spain by analysing the structure of the surface air temperature (SAT) and the ground surface temperature (GST) covariance and also their long-term evolution. In addition, we have employed the ERA5-Land reanalysis to test the consistence between observations and reanalysis. The results show that the near-surface soil thermal structure is dominated by conduction despite some influence of hydrology-related processes. Regarding the land-air temperature coupling, we have found a strong connection between SAT and GST. However, in the summer months there is an offset in SAT-GST at some sites due to limited evaporation and enhanced sensible heat fluxes. Furthermore, multidecadal SAT-GST decoupling may exist over some sites as a response to decreasing precipitation. The ERA5-Land represents the observations' climatology well, but it underestimates the summer soil temperature observations and the long-term trends at some sites.
  • Publication
    Dynamical and hydrological changes in climate simulations of the last millennium
    (Copernicus Gesellschaft MBH, 2020-07-22) Roldán Gómez, Pedro José; González Rouco, Jesús Fidel; Melo Aguilar, Camilo Andrés; Smerdon, Jason E.
    Simulations of climate of the last millennium (LM) show that external forcing had a major contribution to the evolution of temperatures; warmer and colder periods like the Medieval Climate Anomaly (MCA; ca. 950–1250 CE) and the Little Ice Age (LIA; ca. 1450–1850 CE) were critically influenced by changes in solar and volcanic activity. Even if this influence is mainly observed in terms of temperatures, evidence from simulations and reconstructions shows that other variables related to atmospheric dynamics and hydroclimate were also influenced by external forcing over some regions. In this work, simulations from the Coupled Model Intercomparison Project Phase 5 and Paleoclimate Modelling Intercomparison Project Phase 3 (CMIP5/PMIP3) are analyzed to explore the influence of external forcings on the dynamical and hydrological changes during the LM at different spatial and temporal scales. Principal component (PC) analysis is used to obtain the modes of variability governing the global evolution of climate and to assess their correlation with the total external forcing at multidecadal to multicentennial timescales. For shorter timescales, a composite analysis is used to address the response to specific events of external forcing like volcanic eruptions. The results show coordinated long-term changes in global circulation patterns, which suggest expansions and contractions of the Hadley cells and latitudinal displacements of westerlies in response to external forcing. For hydroclimate, spatial patterns of drier and wetter conditions in areas influenced by the North Atlantic Oscillation (NAO), Northern Annular Mode (NAM), and Southern Annular Mode (SAM) and alterations in the intensity and distribution of monsoons and convergence zones are consistently found. Similarly, a clear short-term response is found in the years following volcanic eruptions. Although external forcing has a greater influence on temperatures, the results suggest that dynamical and hydrological variations over the LM exhibit a direct response to external forcing at both long and short timescales that is highly dependent on the particular simulation and model.
  • Publication
    Methodological and physical biases in global to subcontinental borehole temperature reconstructions: an assessment from a pseudo-proxy perspective
    (Copernicus Gesellschaft MBH, 2020-03-06) Melo Aguilar, Camilo Andrés; González Rouco, J. Fidel; García Bustamante, Elena; Steinert, Norman; Jungclaus, Johann H.; Navarro, Jorge; Roldán Gómez, Pedro J.
    Borehole-based reconstruction is a wellestablished technique to recover information of the past climate variability based on two main hypotheses: (1) past ground surface temperature (GST) histories can be recovered from borehole temperature profiles (BTPs); (2) the past GST evolution is coupled to surface air temperature (SAT) changes, and thus, past SAT changes can be recovered from BTPs. Compared to some of the last millennium (LM) proxy-based reconstructions, previous studies based on the borehole technique indicate a larger temperature increase during the last few centuries. The nature of these differences has fostered the assessment of this reconstruction technique in search of potential causes of bias. Here, we expand previous works to explore potential methodological and physical biases using pseudo-proxy experiments with the Community Earth System Model Last Millennium Ensemble (CESM-LME). A heat-conduction forward model driven by simulated surface temperature is used to generate synthetic BTPs that are then inverted using singular value decomposition. This procedure is applied to the set of simulations that incorporates all of the LM external forcing factors as well as those that consider the concentration of the green house gases (GHGs) and the land use land cover (LULC) changes forcings separately. The results indicate that methodological issues may impact the representation of the simulated GST at different spatial scales, with the temporal logging of the BTPs as the main sampling issue that may lead to an underestimation of the simulated GST 20th-century trends. Our analysis also shows that in the surrogate reality of the CESM-LME the GST does not fully capture the SAT warming during the industrial period, and thus, there may be a further underestimation of the past SAT changes due to physical processes. Globally, this effect is mainly influenced by the GHG forcing, whereas regionally, LULC changes and other forcings factors also contribute. These findings suggest that despite the larger temperature increase suggested by the borehole estimations during the last few centuries of the LM relative to some other proxy reconstructions, both the methodological and physical biases would result in a underestimation of the 20th-century warming.
  • Publication
    Land–air interactions and subsurface heat transport: the role of external forcing and implications for last millennium temperature reconstructions
    (Universidad Complutense de Madrid, 2021-06-30) Melo Aguilar, Camilo Andrés; González Rouco, Jesús Fidel
    The energy exchanges at the land-atmosphere interface play a fundamental role in several weather and climatic processes both in the atmosphere and below the land surface. A part of the radiation that reaches the surface is reflected away or dissipated by sensible and latent heat fluxes back to the atmosphere while the ground heat flux balances the excess of incoming energy. This surface energy balance establishes a link between the atmosphere and the ground surface that often translates into a strong coupling between the surface air temperature (SAT) and the ground surface temperature (GST). In turn, the surface temperature stands as the key variable since it aects the amount of heat owing into the soil through thermal conduction, thus controlling the distribution of temperature below thesurface. The coupling between SAT and GST and the conductive heat transport of the surface temperature into the soil stand as the central assumptions for reconstructing the past surface temperature variations from present-day subsurface temperature measurements in a technique known as borehole reconstructions. As with every type of temperature reconstruction method, the borehole technique is subject to uncertainty sources principally due to the inuence of physical processes at the surface that interrupt the SAT{GST coupling assumption over adiversity of temporal scales. Understanding the physical mechanisms behind such processes is crucial to gain con dence in the borehole technique estimates regarding the past SAT variations...