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- Lind, Petter, 1979-, et al.
(author)
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Benefits and added value of convection-permitting climate modeling over Fenno-Scandinavia
- 2020
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 55:7-8, s. 1893-1912
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Journal article (peer-reviewed)abstract
- Convection-permitting climate models have shown superior performance in simulating important aspects of the precipitation climate including extremes and also to give partly different climate change signals compared to coarser-scale models. Here, we present the first long-term (1998–2018) simulation with a regional convection-permitting climate model for Fenno-Scandinavia. We use the HARMONIE-Climate (HCLIM) model on two nested grids; one covering Europe at 12 km resolution (HCLIM12) using parameterized convection, and one covering Fenno-Scandinavia with 3 km resolution (HCLIM3) with explicit deep convection. HCLIM12 uses lateral boundaries from ERA-Interim reanalysis. Model results are evaluated against reanalysis and various observational data sets, some at high resolutions. HCLIM3 strongly improves the representation of precipitation compared to HCLIM12, most evident through reduced “drizzle” and increased occurrence of higher intensity events as well as improved timing and amplitude of the diurnal cycle. This is the case even though the model exhibits a cold bias in near-surface temperature, particularly for daily maximum temperatures in summer. Simulated winter precipitation is biased high, primarily over complex terrain. Considerable undercatchment in observations may partly explain the wet bias. Examining instead the relative occurrence of snowfall versus rain, which is sensitive to variance in topographic heights it is shown that HCLIM3 provides added value compared to HCLIM12 also for winter precipitation. These results, indicating clear benefits of convection-permitting models, are encouraging motivating further exploration of added value in this region, and provide a valuable basis for impact studies.
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| 2. |
- Lind, Petter, 1979-, et al.
(author)
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Climate change information over Fenno-Scandinavia produced with a convection-permitting climate model
- 2022
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 61:1-2, s. 519-541
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Journal article (peer-reviewed)abstract
- This paper presents results from high-resolution climate change simulations that permit convection and resolve mesoscale orography at 3-km grid spacing over Fenno-Scandinavia using the HARMONIE-Climate (HCLIM) model. Two global climate models (GCMs) have been dynamically down-scaled for the RCP4.5 and RCP8.5 emission scenarios and for both near and far future periods in the 21st century. The warmer and moister climate conditions simulated in the GCMs lead to changes in precipitation characteristics. Higher precipitation amounts are simulated in fall, winter and spring, while in summer, precipitation increases in northern Fenno-Scandinavia and decreases in the southern parts of the domain. Both daily and sub-daily intense precipitation over Fenno-Scandinavia become more frequent at the expense of low-intensity events, with most pronounced shifts in summer. In the Scandinavian mountains, pronounced changes occur in the snow climate with a shift in precipitation falling as snow to rain, reduced snow cover and less days with a significant snow depth. HCLIM at 3-km grid spacing exhibits systematically different change responses in several aspects, e.g. a smaller shift from snow to rain in the western part of the Scandinavian mountains and a more consistent decrease in the urban heat island effect by the end of the 21st century. Most importantly, the high-resolution HCLIM shows a significantly stronger increase in summer hourly precipitation extremes compared to HCLIM at the intermediate 12-km grid spacing. In addition, an analysis of the statistical significance of precipitation changes indicates that simulated time periods of at least a couple of decades is recommended to achieve statistically robust results, a matter of important concern when running such high-resolution climate model experiments. The results presented here emphasizes the importance of using “convection-permitting” models to produce reliable climate change information over the Fenno-Scandinavian region.
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| 4. |
- Lind, Petter, 1979-
(author)
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Kilometer-scale climate modeling of precipitation in the Nordic region
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Future changes in precipitation, in particular extremes, are among the most impact-relevant consequences of a warming climate driven by increases in atmospheric greenhouse gas concentrations. Still, climate model projections of future changes in regional and local precipitation remain uncertain. This is in part due to inabilities of climate models to properly represent important atmospheric moist processes, such as convection, as well as surface properties like complex terrain, primarily since these models are typically run at relatively coarse horizontal resolution. The application of a new generation of kilometer-scale ”convection-permitting” models (CPMs), which treat deep convection explicitly, has led to a step-change improvement in simulating precipitation, especially short-duration local intense events. Therefore, CPMs have proven to be valuable tools in understanding precipitation in present climate and its response to rising global temperatures.Here, the performance of the HARMONIE-Climate (HCLIM) CPM in a regional context has been investigated as well as the added value of this model in comparison with HCLIM run with standard grid resolution of ~10 km. In the present climate, the HCLIM CPM applied over the Nordic region outperforms both the coarser-scale HCLIM and a global reanalysis data set, especially for precipitation on sub-daily time scales in summer when precipitation is often convective. This is corroborated in a study investigating how precipitation is related to large-scale atmospheric circulation, which revealed differences between the HCLIM CPM and its coarser counterpart in convection-dominated circulation types in summer. By improving the frequency and intensity distributions, the wet bias seen in the coarser HCLIM version is reduced by the CPM while also better capturing intense precipitation events, but also improvements in the partitioning between snow and rain in complex terrain.In projections of a future warmer climate, the HCLIM CPM simulates stronger increases in heavy precipitation compared to the coarser-scale HCLIM version, most notably in the warm season, sometimes in excess of the thermodynamically constrained increase in atmospheric moisture content of ~7%/oC, referred to as the Clausius-Clapeyron scaling relation (CC-relation). Applying the HCLIM CPM over European sub-regions with different temperature and humidity conditions reveal consistently stronger increase of sub-daily precipitation at the local scale compared to the scales represented by coarser models. However, the environmental conditions played an important role in the scaling of precipitation with temperature; a scaling larger than the CC-relation was found in regions with relatively moist conditions, while in dry areas the scaling was in line with or smaller than the CC-relation.It is concluded that there is a clear benefit of using HCLIM at the convection-permitting scale, a fit-for-purpose model to investigate precipitation processes and their change following global warming over the Nordic region and elsewhere.
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| 5. |
- Lind, Petter, 1979-, et al.
(author)
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Spatial and temporal characteristics of summer precipitation over Central Europe in a suite of high-resolution climate models
- 2016
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In: Journal of Climate. - 0894-8755 .- 1520-0442. ; 29:10, s. 3501-3518
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Journal article (peer-reviewed)abstract
- High-impact, localized intense rainfall episodes represent a major socio-economic problem for societies worldwide, and at the same time these events are notoriously difficult to simulate properly in climate models. Here, the authors investigate how horizontal resolution and model formulation influence this issue by applying the HARMONIE regional climate model (HCLIM) with three different setups; two using convection parameterization at 15 and 6.25 km horizontal resolution (the latter within the “grey-zone” scale), with lateral boundary conditions provided by ERA-Interim reanalysis and integrated over a pan-European domain, and one with explicit convection at 2 km resolution (HCLIM2) over the Alpine region driven by the 15 km model. Seven summer seasons were sampled and validated against two high-resolution observational data sets. All HCLIM versions underestimate the number of dry days and hours by 20-40%, and overestimate precipitation over the Alpine ridge. Also, only modest added value were found of “grey-zone” resolution. However, the single most important outcome is the substantial added value in HCLIM2 compared to the coarser model versions at sub-daily time scales. It better captures the local-to-regional spatial patterns of precipitation reflecting a more realistic representation of the local and meso-scale dynamics. Further, the duration and spatial frequency of precipitation events, as well as extremes, are closer to observations. These characteristics are key ingredients in heavy rainfall events and associated flash floods, and the outstanding results using HCLIM in convection-permitting setting are convincing and encourage further use of the model to study changes in such events in changing climates.
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