Roman Andrea Brogli


Last Name

Brogli

First Name

Roman Andrea

ORCID

0000-0002-4232-8800

Organisational unit

Filters

2019 - 201912020 - 20233
Reset filters

Search Results

Publications 1 - 4 of 4
  • Disentangling Drivers and Patterns of European Climate Change
    Item type: Doctoral Thesis
    Brogli, Roman Andrea (2019)
    Combined observations of the earth’s atmosphere, oceans, and land surface show a clear change in the global climate system over the past 100 years. The planet’s continuously rising temperature, which is shown by these observations, is predominantly driven by persistent human greenhouse gas emissions. The global warming trend is expected to continue throughout the 21st century as long as greenhouse gases accumulate in the atmosphere. Increased global temperatures threaten humans, life, and ecosystems on the planet by potentially triggering illnesses such as heat strokes, food insecurity, biodiversity loss, and natural hazards. In regions where precipitation is decreasing together with increasing temperature, temperature-related hazards are amplified and additional hazards connected to water scarcity arise. Model simulations of the future climate show substantial regional variations in both temperature and precipitation changes. It is critical to gain further confidence in such projected spatial climate change patterns, especially for vulnerable regions, where there is a risk of amplified warming or strong changes in precipitation. To gain further confidence, there is a need to understand which changes in the climate system cause these spatial patterns. Scientific confidence in the projected patterns is essential for developing effective regional strategies to mitigate and adapt to climate change. The goal of this thesis is to determine the causes of spatial patterns of future temperature and precipitation changes in climate simulations. The focus is on prominent patterns of climate change in Europe, namely on the projected amplified summer warming pattern in the Mediterranean and the projected year-round precipitation decline in the same region. We find that the amplified Mediterranean summer warming is predominantly caused by spatially different lapse-rate changes. Lapse-rate changes are substantial throughout the continent but weakest in the Mediterranean. The influence of Hadley circulation changes on the European summer climate is found to be negligible. The Mediterranean summer precipitation decline can largely be explained by thermodynamic changes including warming contrasts between land and ocean, lapse-rate changes, and changes in atmospheric humidity. Circulation changes further contribute to the summer precipitation decline but are of secondary importance. The situation in winter is different, where circulation changes and connected changes in the atmospheric state are the main cause for the precipitation decline in the Mediterranean. Our results also indicate that lapse-rate changes are not exclusively important for the pattern of summer land temperature changes in Europe but also in many other mid-latitude and tropical regions on the northern and southern hemispheres during summer. The connection of lapse-rate changes to amplified summer warming patterns increases the confidence in the regional projections since lapse-rate changes are a consequence of the well-understood higher moisture-holding capacity of warmer air. The confidence in the Mediterranean precipitation decline should be considered larger in summer than in winter since the influence of uncertain circulation changes is smaller in summer compared to winter.
  • Future summer warming pattern under climate change is affected by lapse-rate changes
    Item type: Journal Article
    Brogli, Roman Andrea; Lund Sørland, Silje; Kröner, Nico; et al. (2021)
    Weather and Climate Dynamics
    Greenhouse-gas-driven global temperature change projections exhibit spatial variations, meaning that certain land areas will experience substantially enhanced or reduced surface warming. It is vital to understand enhanced regional warming anomalies as they locally increase heat-related risks to human health and ecosystems. We argue that tropospheric lapse-rate changes play a key role in shaping the future summer warming pattern around the globe in mid-latitudes and the tropics. We present multiple lines of evidence supporting this finding based on idealized simulations over Europe, as well as regional and global climate model ensembles. All simulations consistently show that the vertical distribution of tropospheric summer warming is different in regions characterized by enhanced or reduced surface warming. Enhanced warming is projected where lapse-rate changes are small, implying that the surface and the upper troposphere experience similar warming. On the other hand, strong lapse-rate changes cause a concentration of warming in the upper troposphere and reduced warming near the surface. The varying magnitude of lapse-rate changes is governed by the temperature dependence of the moist-adiabatic lapse rate and the available tropospheric humidity. We conclude that tropospheric temperature changes should be considered along with surface processes when assessing the causes of surface warming patterns.
  • The pseudo-global-warming (PGW) approach: Methodology, software package PGW4ERA5 v1.1, validation, and sensitivity analyses
    Item type: Journal Article
    Brogli, Roman Andrea; Heim, Christoph; Mensch, Jonas; et al. (2023)
    Geoscientific Model Development
    The term "pseudo-global warming"(PGW) refers to a simulation strategy in regional climate modeling. The strategy consists of directly imposing large-scale changes in the climate system on a control regional climate simulation (usually representing current conditions) by modifying the boundary conditions. This differs from the traditional dynamic downscaling technique where output from a global climate model (GCM) is used to drive regional climate models (RCMs). The PGW climate changes are usually derived from a transient global climate model (GCM) simulation. The PGW approach offers several benefits, such as lowering computational requirements, flexibility in the simulation design, and avoiding biases from global climate models. However, implementing a PGW simulation is non-trivial, and care must be taken not to deteriorate the physics of the regional climate model when modifying the boundary conditions. To simplify the preparation of PGW simulations, we present a detailed description of the methodology and provide the companion software PGW4ERA5 facilitating the preparation of PGW simulations. In describing the methodology, particular attention is devoted to the adjustment of the pressure and geopotential fields. Such an adjustment is required when ensuring consistency between thermodynamical (temperature and humidity) changes on the one hand and dynamical changes on the other hand. It is demonstrated that this adjustment is important in the extratropics and highly essential in tropical and subtropical regions. We show that climate projections of PGW simulations prepared using the presented methodology are closely comparable to traditional dynamic downscaling for most climatological variables.
  • COSMO-CLM regional climate simulations in the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework: A review
    Item type: Review Article
    Sørland, Silje L.; Brogli, Roman Andrea; Pothapakula, Praveen K.; et al. (2021)
    Geoscientific Model Development
    In the last decade, the Climate Limited-area Modeling Community (CLM-Community) has contributed to the Coordinated Regional Climate Downscaling Experiment (CORDEX) with an extensive set of regional climate simulations. Using several versions of the COSMO-CLM-Community model, ERA-Interim reanalysis and eight global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were dynamically downscaled with horizontal grid spacings of 0.44g (g1/4g50gkm), 0.22g (g1/4g25gkm), and 0.11g (g1/4g12gkm) over the CORDEX domains Europe, South Asia, East Asia, Australasia, and Africa. This major effort resulted in 80 regional climate simulations publicly available through the Earth System Grid Federation (ESGF) web portals for use in impact studies and climate scenario assessments. Here we review the production of these simulations and assess their results in terms of mean near-surface temperature and precipitation to aid the future design of the COSMO-CLM model simulations. It is found that a domain-specific parameter tuning is beneficial, while increasing horizontal model resolution (from 50 to 25 or 12gkm grid spacing) alone does not always improve the performance of the simulation. Moreover, the COSMO-CLM performance depends on the driving data. This is generally more important than the dependence on horizontal resolution, model version, and configuration. Our results emphasize the importance of performing regional climate projections in a coordinated way, where guidance from both the global (GCM) and regional (RCM) climate modeling communities is needed to increase the reliability of the GCM-RCM modeling chain.
Publications 1 - 4 of 4