Advancing global storm surge modelling using the new ERA5 climate reanalysis

This study examines the implications of recent advances in global climate modelling for simulating storm surges. Following the ERA-Interim (0.75° × 0.75°) global climate reanalysis, in 2018 the European Centre for Medium-range Weather Forecasts released its successor, the ERA5 (0.25° × 0.25°) reanalysis. Using the Global Tide and Surge Model, we analyse eight historical storm surge events driven by tropical—and extra-tropical cyclones. For these events we extract wind fields from the two reanalysis datasets and compare these against satellite-based wind field observations from the Advanced SCATterometer. The root mean squared errors in tropical cyclone wind speed reduce by 58% in ERA5, compared to ERA-Interim, indicating that the mean sea-level pressure and corresponding strong 10-m winds in tropical cyclones greatly improved from ERA-Interim to ERA5. For four of the eight historical events we validate the modelled storm surge heights with tide gauge observations. For Hurricane Irma, the modelled surge height increases from 0.88 m with ERA-Interim to 2.68 m with ERA5, compared to an observed surge height of 2.64 m. We also examine how future advances in climate modelling can potentially further improve global storm surge modelling by comparing the results for ERA-Interim and ERA5 against the operational Integrated Forecasting System (0.125° × 0.125°). We find that a further increase in model resolution results in a better representation of the wind fields and associated storm surges, especially for small size tropical cyclones. Overall, our results show that recent advances in global climate modelling have the potential to increase the accuracy of early-warning systems and coastal flood hazard assessments at the global scale.

2. The climate change debate

‘The climate change debate’ describes the combination of factors that led to recognition and acceptance of climate change, including that it was anthropogenic, beginning with climate change science research carried out in the 1950s and early 1960s. The next stages of research into this area came later in the 1980s: the observed upturn in the global temperature data set; the increased knowledge of past climate change; significant advances in global climate modelling; the emergence of global environmental awareness; increased media interest in the confrontational nature of the debate; and finally politicians and economists taking the climate change threat seriously since the late 1990s.

Organic aerosol and global climate modelling: a review

The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.

Organic aerosol and global climate modelling: a review

The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.

Imaging spectroscopy as a quantative tool for the retrieval of biogeophysical parameters

Representing the dynamic character of Vegetation in global climate modelling is a challenging task. We present a new Instrumentation approach in the form of APEX, an airborne imaging spectrometer to address the key variables and processes relevant for monitoring the biogeophysical and biochemical parameters at the local, regional and national scale. We are able to demonstrate that a large number of relevant processes and variables have been monitored successfully using imaging spectrometers. In particular, the accuracy of the variable retrieval using this observational approach has much improved and the quantification of the interaction of the radiation field with Vegetation has been made possible. The airborne instrument APEX will be made available to the scientific Community in early 2005, whereas it's space successor SPECTRA is scheduled for launch in 2008. The inclusion of the spectro-directional and thermal components will contribute toward minimizing retrieval uncertainties. Until these instruments are introduced into the market, there is enough time to develop the necessary products and to inform the scientific Community about the new possibilities.