Réf. Lenderink & van Meijgaard 2008 - A

Référence bibliographique complète

LENDERINK, G., VAN MEIJGAARD, E. 2008. Increase in hourly precipitation extremes beyond expectations from temperature changes. Nature Geoscience, 1, 511-514, doi:10.1038/ngeo262

Abstract: Changes in precipitation extremes under greenhouse warming are commonly assumed to be constrained by changes in the amounts of precipitable water in the atmosphere [1–4]. Global climate models generally predict only marginal changes in relative humidity [5], implying that the actual amount of atmospheric precipitable water scales with the water vapour content of saturation, which is governed by the Clausius–Clapeyron relation. Indeed, changes in daily precipitation extremes in global climate models seem to be consistent with the 7% increase per degree of warming given by the Clausius–Clapeyron relation [3,4] , but it is uncertain how general this scaling behaviour is across timescales. Here, the authors analyse a 99-year record of hourly precipitation observations from De Bilt, the Netherlands, and find that one-hour precipitation extremes increase twice as fast with rising temperatures as expected from the Clausius–Clapeyron relation when daily mean temperatures exceed 12 °C. In addition, simulations with a high-resolution regional climate model show that one-hour precipitation extremes increase at a rate close to 14% per degree of warming in large parts of Europe. The results demonstrate that changes in short-duration precipitation extremes may well exceed expectations from the Clausius–Clapeyron relation. These short-duration extreme events can have significant impacts, such as local flooding, erosion and water damage.

Mots-clés
 

Organismes / Contact

Royal Netherlands Meteorological Institute (KNMI), 3730 AE De Bilt, The Netherlands - e-mail: lenderin@knmi.nl


(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
Precipitation      

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
Western Europe   Observations at De Bilt, the Netherlands     1971–2000 and 2071–2100

(1) - Modifications des paramètres atmosphériques
Reconstitutions
 
Observations

Here, the authors of the present study investigate how modelled intensities compare with observations. Furthermore, the dependency of precipitation intensity on temperature found in the present-day climate is linked to the climate response in a long climate simulation with a regional climate model. They analyse a 99-year record of hourly precipitation observations from De Bilt, the Netherlands, and find that one-hour precipitation extremes increase twice as fast with rising temperatures as expected from the Clausius–Clapeyron relation when daily mean temperatures exceed 12 °C [see details in the study].

In the observations, the most pronounced temperature scaling is found for the most extreme hourly precipitation intensities. This suggests that on this timescale the processes involved are comparatively simple. Daily intensities show a more complex behaviour, indicating a complex interplay between processes at the daily level. On average, daily intensities increase at a slower rate with temperature than hourly intensities. But because hourly intensities naturally cannot exceed the daily sum, this distinction in scaling cannot hold infinitely. Interestingly, although there is no sign of a levelling off for hourly intensities, daily intensities indeed seem to increase steeply for temperatures above 22 °C

Modélisations

There is a general consensus that the character of precipitation—for instance, average, intensity and frequency— will change as climate changes [2,6,7]. However, predictions of future precipitation changes are also highly uncertain. Our understanding of the essential processes involved in precipitation formation— ranging from the large-scale atmospheric dynamics [8,9], meso-scale convective circulations [10], to the local precipitation microphysics at the smallest spatial and temporal scales [11]—is limited, as is our ability to model these processes in global and regional climate models.

The notion that the Clausius–Clapeyron relation may constrain future changes in extreme precipitation is based on the following arguments [1]. First, the atmospheric relative humidity remains relatively constant as climate changes, which causes the actual precipitable water to scale with the saturation value. Second, intense precipitation totals are mainly determined by the precipitable water already in the atmosphere. Third, the nature of the atmospheric circulation, with mainly the upward motions producing precipitation, does not change considerably. Whereas there is reasonable support that the first two assumptions are approximately valid at least at the larger scale [5,12,13], the third assumption is generally questioned [5,8,14]. Many global climate models (GCMs) predict changes in the large-scale atmospheric circulation and related changes in precipitation [8,9]. At the scale of convective showers, increased latent heat release may intensify the upward motions giving rise to a scaling exceeding the Clausius–Clapeyron relation, a super-Clausius–Clapeyron scaling [1]. Despite these reservations, the Clausius–Clapeyron relation is found to be a good predictor for changes in extreme daily precipitation in GCMs [2–4].

On a (sub-)daily timescale, the highest precipitation intensities are usually related to convective showers. Climate models do not explicitly resolve these showers, but use implicit parameterizations instead. Long-standing problems with these convective parameterizations exist, related to the onset and life cycle of the convective clouds [15]. Here, the authors of the present study investigate how modelled intensities compare with observations. Furthermore, the dependency of precipitation intensity on temperature found in the present-day climate is linked to the climate response in a long climate simulation with a regional climate model.

They analyse a 99-year record of hourly precipitation observations from De Bilt, the Netherlands, and find that one-hour precipitation extremes increase twice as fast with rising temperatures as expected from the Clausius–Clapeyron relation when daily mean temperatures exceed 12 °C [see details in the study].


To test the question : "Are these relations derived from day-to-day variability in present-day climate reflected in the response of extreme precipitation to climate change?", the authors computed the relative change of summertime extreme precipitation between 1971–2000 and 2071–2100 in a climate integration with RACMO2. Simulations with a high-resolution regional climate model show that one-hour precipitation extremes increase at a rate close to 14% per degree of warming in large parts of Europe:

=> For the 99.9th percentile, the modelled change in the 1 h extremes I1 hmax is clearly much larger than the change in 1 d extremes for large parts of central Europe. For central Europe, changes in 1 h precipitation extremes are typically found to exceed 10%, in a large area even 15%, per degree. Daily extremes increase typically 5–10% per degree. The increase in intensity is smaller in France, which could be related to the much dryer average conditions in the future climate for that area. Averages of this pooled data for a large central Europe area (between 46–62 °N and −2–22 °E) show that the changes typically obey the Clausius–Clapeyron relation for 1 d and two times the Clausius–Clapeyron relation for 1 h intensity changes. Changes computed from the raw data on a grid point level give large spatial variations, but the average for central Europe is very similar to the average of the pooled data.

The response of precipitation extremes to climate change and the dependency of precipitation extremes on temperature in the present-day climate are clearly not necessarily the same. On the one hand, the dependency in the present-day climate is derived from day-to-day variations in temperature and precipitation, which are both primarily caused by large-scale atmospheric circulation variability. On the other hand, a large part of the projected change in precipitation is not related to large-scale circulation changes [8,9,18]. In particular, the change of the extremes may be dominated by thermodynamically driven processes [8,18]. In such a conceptual framework of climate change, each (extreme) wet event in the present-day climate is considered to be related to a similar wet event in the future climate, occurring with a similar atmospheric circulation yet at a higher temperature and, thus, higher moisture content of the atmosphere. In this framework, the frequency of wet events does not change considerably, whereas the authors claim (without proof, but supported by the results) that the increase in intensity of each wet event can be predicted with the present-day scaling relations.

(...)

Finally, the finding that the temperature scaling in the present-day climate is reflected in the modelled climate change signal opens ways of quantifying our confidence in future climate change predictions. In this respect, it is worrying that the model generally underestimates the temperature dependency (except for the most extreme events). Increases in extreme precipitation as climate changes may more generally follow a temperature dependency well above the Clausius–Clapeyron relation than suggested by present-day climate model results [17].

Hypothèses
 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)

The authors investigate how modelled intensities of precipitation compare with observations. Furthermore, the dependency of precipitation intensity on temperature found in the present-day climate is linked to the climate response in a long climate simulation with a regional climate model.

They start by analysing a 99-year record of quality controlled 1 h precipitation observations at De Bilt in the Netherlands. They present results for the 1 h precipitation intensity I1 h, the daily maximum of the 1 h precipitation intensity I1 hmax and the daily intensity I1 d, which is the 24 h precipitation sum. They stratified the precipitation data based on the daily mean temperature in bins of 2 °C width, and computed the 75th, 90th, 99th and 99.9th percentiles of the distribution of wet events (hours or days) in each bin.

To investigate whether or not the relations found between precipitation and temperature are reproduced by a state-of-the-art high-resolution climate model, we analysed a simulation of the present-day climate 1971–2000 from the regional climate model [16] RACMO2. RACMO2 is operated at a resolution of 25 km. For the present-day climate, RACMO2 was forced by boundaries derived from [21] ERA40. For the climate change simulation, RACMO2 was driven by output from the ECHAM5 global climate model using the A1b emission scenario for the period 1950–2100. This integration has been carried out in the EU-funded FP6 project ENSEMBLES [22].

To test the question : "Are these relations derived from day-to-day variability in present-day climate reflected in the response of extreme precipitation to climate change?", the authors computed the relative change of summertime extreme precipitation between 1971–2000 and 2071–2100 in a climate integration with RACMO2. The data in individual grid points are pooled in small boxes of 5×4 degrees longitude–latitude to improve the signal-to-noise ratio. From this pooled data set, containing the data of about 300 individual grid points, the different percentiles of the distribution are computed. Unlike before, the percentiles are now computed using all hours and days, dry and wet, because it is the absolute frequency of occurrence of extremes that counts for society. Changes in intensity are scaled with the box mean temperature change between the control and the future period.


(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 

 


(3) - Effets du changement climatique sur l'aléa
Reconstitutions
 
Observations
 
Modélisations

Simulations with a high-resolution regional climate model show that one-hour precipitation extremes increase at a rate close to 14% per degree of warming in large parts of Europe. The results demonstrate that changes in short-duration precipitation extremes may well exceed expectations from the Clausius–Clapeyron relation. These short-duration extreme events can have significant impacts, such as local flooding, erosion and water damage.

Hypothèses

 


Paramètre de l'aléa
Sensibilité des paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 

[See above]


(4) - Remarques générales
 

(5) - Syntèses et préconisations
 

Références citées :

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2. Hegerl, G. et al. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate 664–745 (Cambridge Univ. Press, Cambridge, 2007).

3. Pall, P., Allen, M. & Stone, D. Testing the Clausius–Clapeyron constraint on changes in extreme precipitation under CO2 warming. Clim. Dyn. 28, 351–363 (2007).

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5. Bony, S. et al. How well do we understand and evaluate climate change feedback processes? J. Clim. 19, 3445–3482 (2006).

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7. Frei, C., Schöll, R., Fukutome, S., Schmidli, J. & Vidale, P. Future change of precipitation extremes in Europe: Intercomparison of scenarios from regional climate models. J. Geophys. Res. 111, D06105 (2006).

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9. van Ulden, A. P. & van Oldenborgh, G. Large-scale atmospheric circulation biases in global climate model simulations and their importance for climate change in central Europe. Atmos. Chem. Phys. 6, 863–881 (2006).

10. Trapp, R. J. et al. Changes in severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing. Proc. Natl Acad. Sci. 104, 19719–19723 (2007).

11. Baker, M. B. & Peter, T. Small-scale cloud processes and climate. Nature 451, 299–300 (2008).

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13. Ingram,W. J. On the robustness of the water vapor feedback: GCM vertical resolution and formulation. J. Clim. 15, 1917–1921 (2002).

14. Held, I. M. & Soden, B. J. Robust responses of the hydrological cycle to global warming. J. Clim. 19, 5686–5699 (2006).

15. Guichard, F. et al. Modelling the diurnal cycle of deep precipitating convection over land with cloud-resolving models and single-column models. Q. J. R. Meteorol. Soc. 130, 3139–3172 (2004).

16. Lenderink, G., van den Hurk, B., van Meijgaard, E., van Ulden, A. & Cuijpers, H. Simulation of present-day climate in RACMO2: First results and model developments. Tech. Rep. TR-252 (Royal Netherlands Meteorological Institute, De Bilt, 2003).

17. Lenderink, G., van Meijgaard, E. & Selten, F. Intense coastal rainfall in the Netherlands in response to high sea water temperatures: Analysis of the event of august 2006 from the perspective of a changing climate. Clim. Dyn. (2008, in the press).

18. Lenderink, G., van Ulden, A., van den Hurk, B. & Keller, F. A study on combining global and regional climate model results for generating climate scenarios of temperature and precipitation for the Netherlands. Clim. Dyn. 29, 157–176 (2007).

19. Schneider, T. & O’Gorman, P. A. Proc. Hawaiian Aha Huliko’a Winter Workshop 61–66 (University of Hawaii, Honolulu, 2007).

20. <http://www.knmi.nl/klimatologie/onderzoeksgegevens/index.html>.

21. Uppala, S. et al. The ERA-40 re-analysis. Q. J. R. Meteorol. Soc. 131, 2961–3012 (2005).

22. Hewitt, C. & Griggs, D. Ensembles-based predictions of climate changes and their impacts (ENSEMBLES). Eos 85, 566 (2004).