Journal: International Journal of Climatology

Abbreviation

Int. j. climatol.

Publisher

Wiley

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ISSN

0899-8418
1097-0088

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Publications 1 - 10 of 19
  • The local climate impact of an African city during clear-sky conditions-Implications of the recent urbanization in Kampala (Uganda)
    Item type: Journal Article
    Brousse, Oscar; Wouters, Hendrik; Demuzere, Matthias; et al. (2020)
    International Journal of Climatology
    This study aims at assessing and understanding the impact of recent urbanization on the (surface) urban heat island ((S)UHI) under clear‐sky conditions in a tropical African city using different sources of remotely sensed data sets together with an urban climate model (UCM). The observed SUHI during clear sky conditions is found to be about 4°C on average over the capital city of Kampala, Uganda. The UCM, consisting of TERRA_URB embedded in COSMO‐CLM, represents the SUHI well during night but overestimates it by about 3°C in the mean during day. Moreover, a systematic warm land surface temperature bias of about 4°C is identified by night. Improved urban input parameters—derived from Local Climate Zones following the World Urban Database and Access Portal Tool (WUDAPT) framework—lead to a more realistic representation of spatial land surface temperatures patterns. In addition, this parameterization of the UCM can properly represent atmospheric variables such as air temperature, specific and relative humidity, as observed by the automated weather stations. A model sensitivity study furthermore demonstrates that the stronger urban heat island induced by the recent urbanization of Kampala over the past 15 years strongly interacts with the lake–land breeze circulation. Stronger daytime convection over the hotter city leads to areas of convergence that amplify the afternoon lake breeze in the Southern parts of the metropolis. Overall, this study demonstrates that the city of Kampala has a tangible effect on the regional climate that needs to be considered when studying present and future climate impacts.
  • Testing a weather generator for downscaling climate change projections over Switzerland
    Item type: Journal Article
    Keller, Denise E.; Fischer, Andreas M.; Liniger, Mark A.; et al. (2017)
    International Journal of Climatology
    Climate information provided by global or regional climate models (RCMs) are often too coarse and prone to substantial biases for local assessments or use in impact models. Hence, statistical downscaling becomes necessary. For the Swiss National Climate Change Initiative (CH2011), a delta-change approach was used to provide daily climate scenarios at the local scale. Here, we analyse a Richardson-type weather generator (WG) as an alternative method to downscale daily precipitation, minimum and maximum temperature. The WG is calibrated for 26 Swiss stations and the reference period is 1980–2009. It is perturbed with change factors derived from RCMs (ENSEMBLES) to represent the climate of 2070–2099 assuming the SRES A1B emission scenario. The WG can be run in multi-site mode, making it especially attractive for impact-modellers that rely on a realistic spatial structure in downscaled time-series. The results from the WG are benchmarked against the original delta-change approach that applies mean additive or multiplicative adjustments to the observations. According to both downscaling methods, the results reveal mean temperature increases and a precipitation decrease in summer, consistent with earlier studies. For the summer drying, the WG indicates primarily a decrease in wet-day frequency and correspondingly an increase in mean dry spell length of between 18 and 40% at low-elevation stations. By definition, these potential changes cannot be represented by a delta-change approach. In winter, both methods project a shortening of the frost period (−30 to −60 days) and a decrease of snow days (−20 to −100%). The WG demonstrates though, that almost present-day conditions in snow-days could still occur in the future. As expected, both methods have difficulties in representing extremes. If users focus on changes in temporal sequences and need a large number of future realizations, it is recommended to use data from a WG instead of a delta-change approach.
  • Climatological analysis of urban heat island effects in Swiss cities
    Item type: Journal Article
    Canton, Jacopo; Dipankar, Anurag (2024)
    International Journal of Climatology
    This work presents a high-resolution spatiotemporal analysis of the urban heat island (UHI) effect in Swiss cities during the last 6 years. The entire alpine country is simulated at once using the COSMO model at 1.1 km resolution, validated against a dense national measurement network. Additionally, the bulk parametrisation TERRA URB is used to model the dynamical and thermal effects of urban areas. The resulting data allows us to perform the first comprehensive analysis over the entire Switzerland, with a focus on the UHI effect with intra-urban and across cities comparisons, and to report on the current state of urban warming. Despite the medium-small size of the cities, the UHI is of considerable magnitude especially when considering peak values in ideal weather conditions. The present results confirm previous analyses performed for individual cities, and shed new light on the country-wide picture by highlighting features such as the marked seasonality of the UHI intensity as well as the influence of local climate and topographical features on the urban climate. A thorough discussion is also presented highlighting the absence of simple relationships between UHI intensity and bulk city parameters and weather patterns.
  • A review of studies on observed precipitation trends in Italy
    Item type: Review Article
    Caporali, Enrica; Lompi, Marco; Pacetti, Tommaso; et al. (2021)
    International Journal of Climatology
    Research to detect changes in precipitation variables has become a topic of particular interest to understand modifications in water resources availability. The review is focused on the Italian territory, outlining the “state of the art” of changes in precipitation regime through a review of 54 published studies on observed rainfall trend analyses, in the period 1999–2018. The aim is to combine a large body of knowledge in a single review and to explain the main patterns of rainfall changes occurred in Italy over the last decades. The analysis focused on the Total Precipitation (TP) and the number of Wet Days (WDs) indices at the annual and seasonal scale. A weight factor is introduced to take into account the differences among studies in geographical area, time series length, and number of stations. The review is accompanied by the discussion of other rainfall related variables, that is, precipitation intensity, extreme rainfall events and meteorological droughts, which are useful to provide a broader picture of rainfall changes. Overall, there is an agreement about the tendency of a decrease in wet days on the entire Italy, with limited discrepancies in the various regions. A decrease in wet days is accompanied by a negative trend (although less evident) in total precipitation, especially in winter. Nevertheless, a univocal direction of trends (or lack of thereof) in annual total precipitation and mostly hydrological extreme events is difficult to achieve. © 2020 Royal Meteorological Society.
  • Review of urban climate research in (sub)tropical regions
    Item type: Conference Paper
    Roth, Matthias (2007)
    International Journal of Climatology
  • Freezing of lakes on the Swiss plateau in the period 1901-2006
    Item type: Journal Article
    Hendricks Franssen, Harrie-Jan; Scherrer, S. C. (2008)
    International Journal of Climatology
  • An intercomparison of a large ensemble of statistical downscaling methods over Europe: Results from the VALUE perfect predictor cross‐validation experiment
    Item type: Journal Article
    Gutiérrez, José M.; Maraun, Douglas; Widmann, Martin; et al. (2019)
    International Journal of Climatology
  • Evaluating SINGV-RCM for Long-Term High-Resolution Climate Simulations Over Southeast Asia
    Item type: Journal Article
    Prasanna, Venkatraman; Dipankar, Anurag; Liu, Jianyu; et al. (2025)
    International Journal of Climatology
    Long-term convection-permitting dynamical downscaling has been carried out over Southeast Asia and the Western Maritime Continent, using the Singapore Regional Climate Model (SINGV-RCM) at 8 and 2 km spatial resolutions, respectively. SINGV-RCM is forced with ERA5 reanalysis data for 36 years (1979–2014) at 8 km resolution over Southeast Asia (79E-160E; 16S-24N) with a regular update of the sea surface temperature at 6-h intervals. Subsequently, the 8 km domain simulation is used for forcing a smaller domain over the Western Maritime Continent at a resolution of 2 km (93E-110E; 7.2S-9.9N) for 20 years (1995–2014). Rainfall characteristics including the diurnal cycle, monthly annual cycle, and daily extremes over land and ocean from the two simulations are evaluated against the high-resolution IMERG precipitation data available from 2001 to 2014. SINGV-RCM captures mean and extreme rainfall well; however, there are noticeable biases in the rainfall magnitude over the Ocean. These biases agree with the earlier publications on convection-permitting simulation over the maritime Continent. Models' skill is further evaluated in terms of mean, bias, pattern correlation and RMSE for 8 and 2 km simulations against the IMERG precipitation data.
  • New hourly extreme precipitation regions and regional annual probability estimates for the UK
    Item type: Journal Article
    Darwish, Motasem M.; Tye, Mari R.; Prein, Andreas F.; et al. (2021)
    International Journal of Climatology
    Abstract Recent flooding related to extreme precipitation in the UK has highlighted the importance of better understanding these events. Many studies have quantified annual exceedance probabilities (or return periods) for UK extreme daily precipitation using fixed regions (e.g., HadUKP) and region of interest (ROI) (e.g., Flood Estimation Handbook) approaches, although fewer have evaluated shortduration events, which are important for flash flooding. Existing UK extreme precipitation regions are based on daily datasets which have different characteristics compared to subdaily extremes, and their application to quantify shortduration extremes may therefore be inappropriate. We use a recently available, qualitycontrolled hourly precipitation dataset for the UK from 1992 to 2014 to derive various extreme precipitation indices (e.g., annual maxima, 0.99 quantile) which are combined with additional climatological variables (e.g., temperature), geographical characteristics (e.g., latitude), and weather patterns (WPs) to characterize the UK hourly extreme precipitation climatology and to define five new hourly extreme regions. These regions fulfil regional homogeneity and discordancy statistical measures, and reflect the dynamical processes associated with the weather pattern categorisation defined over the UK and surrounding European area. Thereafter, we use regional frequency analysis (RFA) to fit generalized extreme value (GEV) and generalized Pareto (GP) distributions to 1 hr annual maxima (AMAX) and 0.99 quantile (Q99) precipitation, respectively, to calculate regional annual probability estimates (AEP) for 20%, 10%, and 2% (i.e., 5, 10, and 50year return periods). The new regions capture the spatial variation of hourly precipitation across the UK. Furthermore, the AEP estimates using both distributions are similar for each region. Finally, the WPs associated with the frequency and intensity of the most extreme hourly precipitation accumulations are not identical to results reported by others for daily precipitation.
  • Downscaling climate projections over large and data sparse regions: Methodological application in the Zambezi River Basin
    Item type: Journal Article
    Peleg, Nadav; Sinclair, Scott; Fatichi, Simone; et al. (2020)
    International Journal of Climatology
    Climate impact studies often require climate data at a higher space–time resolution than is available from global and regional climate models. Weather generator (WG) models, generally designed for mesoscale applications (e.g., 101–105 km2), are popular and widely used tools to downscale climate data to finer resolution. One advantage of using WGs is their ability to generate the necessary climate variables for impact studies in data sparse regions. In this study, we evaluate the ability of a previously established state of the art WG (the AWE‐GEN‐2d model) to perform in data sparse regions that are beyond the mesoscale, using the Zambezi River basin (106 km2) in southeast Africa as a case study. The AWE‐GEN‐2d model was calibrated using data from satellite retrievals and climate re‐analysis products in place of the absent observational data. An 8‐km climate ensemble at hourly resolution, covering the period of 1976–2099 (present climate and RCP4.5 emission scenario from 2020), was then simulated. Using the simulated 30‐member ensemble, climate indices for both present and future climates were computed. The high‐resolution climate indices allow detailed analysis of the effects of climate change on different areas within the basin. For example, the southwestern area of the basin is predicted to experience the greatest change due to increased temperature, while the southeastern area was found to be already so hot that is less affected (e.g., the number of 'very hot days' per year increase by 18 and 9 days, respectively). Rainfall intensities are found to increase most in the eastern areas of the basin (1 mm·d−1) in comparison to the western region (0.3 mm·d−1). As demonstrated in this study, AWE‐GEN‐2d can be calibrated successfully using data from climate reanalysis products in the absence of ground station data and can be applied at larger scales than the mesoscale.
Publications 1 - 10 of 19