scholarly journals Can We Expect More Extreme Precipitation on the Monthly Time Scale?

2006 ◽  
Vol 19 (4) ◽  
pp. 630-637 ◽  
Author(s):  
Rasmus E. Benestad
Keyword(s):  
Extreme Precipitation ◽  
Climate Model ◽  
Global Climate Model ◽  
Distribution Functions ◽  
Monthly Precipitation ◽  
High Latitudes ◽  
Assessment Report ◽  
The Past ◽  
Ipcc Report ◽  
Instrumental Records

Abstract The Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report states that instrumental records show an increase in precipitation by +0.5%–1% decade−1 in much of the Northern Hemisphere mid- and high latitudes and a decrease of −0.3% decade−1 over subtropical land areas. It has been postulated that these trends are associated with the enhanced levels of atmospheric CO2. In this context, it is natural to ask how continuing rising levels of CO2 may affect the climate in the future. The past IPCC reports have documented numerous studies where increased greenhouse gas concentrations have been prescribed in global climate model simulations. Now, new simulations with state-of-the-art climate models are becoming available for the next IPCC report [the Fourth Assessment Report (AR4)], and results from a number of these simulations are examined in order to determine whether they indicate a change in extreme precipitation on a monthly basis. The analysis involves a simple record–statistics framework and shows that the upper tails of the probability distribution functions for monthly precipitation are being stretched in the mid- and high latitudes where mean-level precipitation increases have already been reported in the past. In other words, values corresponding to extreme monthly precipitation in the past are, according to these results, becoming more frequent.

Downscaling of precipitation on a lake basin: evaluation of rule and decision tree induction algorithms

2012 ◽  
Vol 43 (3) ◽  
pp. 215-230 ◽  
Author(s):  
Manish Kumar Goyal ◽  
C. S. P. Ojha
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Lake Basin ◽  
Monthly Precipitation ◽  
M5 Model Tree ◽  
Reanalysis Dataset ◽  
Model Tree ◽  
Basin Scale ◽  
M5 Model

We investigate the performance of existing state-of-the-art rule induction and tree algorithms, namely Single Conjunctive Rule Learner, Decision Table, M5 Model Tree, Decision Stump and REPTree. Downscaling models are developed using these algorithms to obtain projections of mean monthly precipitation to lake-basin scale in an arid region in India. The effectiveness of these algorithms is evaluated through application to downscale the predictand for the Lake Pichola region in Rajasthan state in India, which is considered to be a climatically sensitive region. The predictor variables are extracted from (1) the National Centre for Environmental Prediction (NCEP) reanalysis dataset for the period 1948–2000 and (2) the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1 and COMMIT for the period 2001–2100. M5 Model Tree algorithm was found to yield better performance among all other learning techniques explored in the present study. The precipitation is projected to increase in future for A2 and A1B scenarios, whereas it is least for B1 and COMMIT scenarios using predictors.

scholarly journals Fidelity of the Observational/Reanalysis Datasets and Global Climate Models in Representation of Extreme Precipitation in East China

2018 ◽  
Vol 32 (1) ◽  
pp. 195-212 ◽  
Author(s):  
Sicheng He ◽  
Jing Yang ◽  
Qing Bao ◽  
Lei Wang ◽  
Bin Wang
Keyword(s):  
Extreme Precipitation ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Yangtze River Basin ◽  
Global Climate Model ◽  
Global Climate Models ◽  
Global Ocean ◽  
East China ◽  
Cmip5 Models

AbstractRealistic reproduction of historical extreme precipitation has been challenging for both reanalysis and global climate model (GCM) simulations. This work assessed the fidelities of the combined gridded observational datasets, reanalysis datasets, and GCMs [CMIP5 and the Chinese Academy of Sciences Flexible Global Ocean–Atmospheric Land System Model–Finite-Volume Atmospheric Model, version 2 (FGOALS-f2)] in representing extreme precipitation over East China. The assessment used 552 stations’ rain gauge data as ground truth and focused on the probability distribution function of daily precipitation and spatial structure of extreme precipitation days. The TRMM observation displays similar rainfall intensity–frequency distributions as the stations. However, three combined gridded observational datasets, four reanalysis datasets, and most of the CMIP5 models cannot capture extreme precipitation exceeding 150 mm day−1, and all underestimate extreme precipitation frequency. The observed spatial distribution of extreme precipitation exhibits two maximum centers, located over the lower-middle reach of Yangtze River basin and the deep South China region, respectively. Combined gridded observations and JRA-55 capture these two centers, but ERA-Interim, MERRA, and CFSR and almost all CMIP5 models fail to capture them. The percentage of extreme rainfall in the total rainfall amount is generally underestimated by 25%–75% in all CMIP5 models. Higher-resolution models tend to have better performance, and physical parameterization may be crucial for simulating correct extreme precipitation. The performances are significantly improved in the newly released FGOALS-f2 as a result of increased resolution and a more realistic simulation of moisture and heating profiles. This work pinpoints the common biases in the combined gridded observational datasets and reanalysis datasets and helps to improve models’ simulation of extreme precipitation, which is critically important for reliable projection of future changes in extreme precipitation.

scholarly journals Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M)

2014 ◽  
Vol 7 (6) ◽  
pp. 8975-9015
Author(s):  
E. M. Knudsen ◽  
J. E. Walsh
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
System Model ◽  
High Latitudes ◽  
Earth System ◽  
Projected Changes

Abstract. Metrics of storm activity in Northern Hemisphere high- and midlatitudes are evaluated from historical output and future projections by the Norwegian Earth System Model (NorESM1-M) coupled global climate model. The European Re-Analysis Interim (ERA-Interim) and the Community Climate System Model (CCSM4), a global climate model of the same vintage as NorESM1-M, provide benchmarks for comparison. The focus is on the autumn and early winter (September through December), the period when the ongoing and projected Arctic sea ice retreat is greatest. Storm tracks derived from a vorticity-based algorithm for storm identification are reproduced well by NorESM1-M, although the tracks are somewhat better resolved in the higher-resolution ERA-Interim and CCSM4. The tracks are projected to shift polewards in the future as climate changes under the Representative Concentration Pathway (RCP) forcing scenarios. Cyclones are projected to become generally more intense in the high-latitudes, especially over the Alaskan region, although in some other areas the intensity is projected to decrease. While projected changes in track density are less coherent, there is a general tendency towards less frequent storms in midlatitudes and more frequent storms in high-latitudes, especially the Baffin Bay/Davis Strait region. Autumn precipitation is projected to increase significantly across the entire high-latitudes. Together with the projected increases in storm intensity and sea level and the loss of sea ice, this increase in precipitation implies a greater vulnerability to coastal flooding and erosion, especially in the Alaskan region. The projected changes in storm intensity and precipitation (as well as sea ice and sea level pressure) scale generally linearly with the RCP value of the forcing and with time through the 21st century.

scholarly journals Sensitivity of remote aerosol distributions to representation of cloud-aerosol interactions in a global climate model

2013 ◽  
Vol 6 (1) ◽  
pp. 331-378 ◽  
Author(s):  
H. Wang ◽  
R. C. Easter ◽  
P. J. Rasch ◽  
M. Wang ◽  
X. Liu ◽  
...  
Keyword(s):  
Liquid Water ◽  
Climate Model ◽  
Global Climate Model ◽  
Fold Increase ◽  
Convective Transport ◽  
The Arctic ◽  
Cloud Base ◽  
High Latitudes ◽  
Upper Troposphere ◽  
Wet Removal

Abstract. Many global aerosol and climate models, including the widely used Community Atmosphere Model version 5 (CAM5), have large biases in predicting aerosols in remote regions such as upper troposphere and high latitudes. In this study, we conduct CAM5 sensitivity simulations to understand the role of key processes associated with aerosol transformation and wet removal affecting the vertical and horizontal long-range transport of aerosols to the remote regions. Improvements are made to processes that are currently not well represented in CAM5, which are guided by surface and aircraft measurements together with results from a multi-scale aerosol-climate model (PNNL-MMF) that explicitly represents convection and aerosol-cloud interactions at cloud-resolving scales. We pay particular attention to black carbon (BC) due to its importance in the Earth system and the availability of measurements. We introduce into CAM5 a new unified scheme for convective transport and aerosol wet removal with explicit aerosol activation above convective cloud base. This new implementation reduces the excessive BC aloft to better simulate observed BC profiles that show decreasing mixing ratios in the mid- to upper-troposphere. After implementing this new unified convective scheme, we examine wet removal of submicron aerosols that occurs primarily through cloud processes. The wet removal depends strongly on the sub-grid scale liquid cloud fraction and the rate of conversion of liquid water to precipitation. These processes lead to very strong wet removal of BC and other aerosols over mid- to high latitudes during winter months. With our improvements, the Arctic BC burden has a10-fold (5-fold) increase in the winter (summer) months, resulting in a much better simulation of the BC seasonal cycle as well. Arctic sulphate and other aerosol species also increase but to a lesser extent. An explicit treatment of BC aging with slower aging assumptions produces an additional 30-fold (5-fold) increase in the Arctic winter (summer) BC burden. This BC aging treatment, however, has minimal effect on other under-predicted species. Interestingly, our modifications to CAM5 that aim at improving prediction of high-latitude and upper tropospheric aerosols also produce much better aerosol optical depth over various other regions globally when compared to multi-year AERONET retrievals. The improved aerosol distributions have impacts on other aspects of CAM5, improving the simulation of global mean liquid water path and cloud forcing.

scholarly journals Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M)

2016 ◽  
Vol 9 (7) ◽  
pp. 2335-2355 ◽  
Author(s):  
Erlend M. Knudsen ◽  
John E. Walsh
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
System Model ◽  
High Latitudes ◽  
Earth System ◽  
Projected Changes

Abstract. Metrics of storm activity in Northern Hemisphere high and midlatitudes are evaluated from historical output and future projections by the Norwegian Earth System Model (NorESM1-M) coupled global climate model. The European Re-Analysis Interim (ERA-Interim) and the Community Climate System Model (CCSM4), a global climate model of the same vintage as NorESM1-M, provide benchmarks for comparison. The focus is on the autumn and early winter (September through December) – the period when the ongoing and projected Arctic sea ice retreat is the greatest. Storm tracks derived from a vorticity-based algorithm for storm identification are reproduced well by NorESM1-M, although the tracks are somewhat better resolved in the higher-resolution ERA-Interim and CCSM4. The tracks show indications of shifting polewards in the future as climate changes under the Representative Concentration Pathway (RCP) forcing scenarios. Cyclones are projected to become generally more intense in the high latitudes, especially over the Alaskan region, although in some other areas the intensity is projected to decrease. While projected changes in track density are less coherent, there is a general tendency towards less frequent storms in midlatitudes and more frequent storms in high latitudes, especially the Baffin Bay/Davis Strait region in September. Autumn precipitation is projected to increase significantly across the entire high latitudes. Together with the projected loss of sea ice and increases in storm intensity and sea level, this increase in precipitation implies a greater vulnerability to coastal flooding and erosion, especially in the Alaskan region. The projected changes in storm intensity and precipitation (as well as sea ice and sea level pressure) scale generally linearly with the RCP value of the forcing and with time through the 21st century.

scholarly journals Can oceanic paleothermometers reconstruct the Atlantic Multidecadal Oscillation?

2011 ◽  
Vol 7 (1) ◽  
pp. 151-159 ◽  
Author(s):  
D. Heslop ◽  
A. Paul
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Large Scale ◽  
Climate Model ◽  
Low Frequency ◽  
Atlantic Multidecadal Oscillation ◽  
Sea Surface ◽  
Prediction Errors ◽  
The Past ◽  
Instrumental Records

Abstract. Instrumental records of the North Atlantic sea surface temperature reveal a large-scale low frequency mode of variability that has become known as the Atlantic Multidecadal Oscillation (AMO). Proxy and modelling studies have demonstrated the important consequences of the AMO on other components of the climate system both within and outside the Atlantic region. Over longer time scales, the past behavior of the AMO is predominantly constrained by terrestrial proxies and only a limited number of records are available from the marine realm itself. Here we use an Earth System-Climate Model of intermediate complexity to simulate AMO-type behavior in the Atlantic with a specific focus placed on the ability of ocean paleothermometers to capture the associated surface and subsurface temperature variability. Given their lower prediction errors and annual resolution, coral-based proxies of sea surface temperature appear to be capable of reconstructing the temperature variations associated with the past AMO with an adequate signal-to-noise ratio. In contrast, the relatively high prediction error and low temporal resolution of sediment-based proxies, such as the composition of foraminiferal calcite, limits their ability to produce interpretable records of past temperature anomalies corresponding to AMO activity. Whilst the presented results will inevitably be model-dependent to some degree, the statistical framework is model-independent and can be applied to a wide variety of scenarios.

scholarly journals Changes in Tropical Cyclone Activity over Northwest Western Australia in the Past 50 Years and a View of the Future 50 Years

2015 ◽  
Vol 19 (15) ◽  
pp. 1-24 ◽  
Author(s):  
Diandong Ren ◽  
Lance M. Leslie
Keyword(s):  
Tropical Cyclone ◽  
Western Australia ◽  
Large Scale ◽  
Climate Model ◽  
Permutation Test ◽  
Distribution Functions ◽  
Cyclone Activity ◽  
The Past ◽  
Probability Distribution Functions ◽  
The Mean

Abstract In the first half of this research, this study examines the trend in tropical cyclone (TC) activity over the economically important northwest Western Australia (NWA) TC basin (equator–40°S, 80°–140°E) based on statistical analyses of the International Best Track Archive for Climate Stewardship (IBTrACS) and large-scale environmental variables, which are known to be closely linked to the formation and longevity of TCs, from NCEP–NCAR reanalyses. In the second half, changes in TC activity from climate model projections for 2000–60 are compared for (i) no scenario change (CNTRL) and (ii) the moderate IPCC Special Report on Emission Scenarios (SRES) A1B scenario (EGHG). The aims are to (i) determine differences in mean annual TC frequency and intensity trends, (ii) test for differences between genesis and decay positions of CNTRL and EGHG projections using a nonparametric permutation test, and (iii) use kernel density estimation (KDE) for a cluster analysis of CNTRL and EGHG genesis and decay positions and generate their probability distribution functions. The main findings are there is little difference in the mean TC number over the period, but there is a difference in mean intensity; CNTRL and EGHG projections differ in mean genesis and decay positions in both latitude and longitude; and the KDE reveals just one cluster in both CNTRL and EGHG mean genesis and decay positions. The EGHG KDE is possibly disjoint, with a wider longitudinal spread. The results can be explained in terms of physical, meteorological, and sea surface temperature (SST) conditions, which provide natural limits to the spread of the genesis and decay points.

The coupling of winds, aerosols and chemistry in Titan's atmosphere

2008 ◽  
Vol 367 (1889) ◽  
pp. 665-682 ◽  
Author(s):  
Sebastien Lebonnois ◽  
Pascal Rannou ◽  
Frederic Hourdin
Keyword(s):  
Complex System ◽  
Climate Model ◽  
Global Climate ◽  
Thermal Structure ◽  
Global Climate Model ◽  
Lower Atmosphere ◽  
Strongly Coupled ◽  
Atmospheric Structure ◽  
The Past ◽  
Production Mechanisms

The atmosphere of Titan is a complex system, where thermal structure, radiative transfer, dynamics, microphysics and photochemistry are strongly coupled together. The global climate model developed over the past 15 years at the Pierre-Simon Laplace Institute has been exploring these different couplings, and has demonstrated how they can help to interpret the observed atmospheric structure of Titan's lower atmosphere (mainly in the stratosphere and troposphere). This review discusses these interactions, and our current understanding of their role in the context of this model, but also of other available works. The recent Cassini results, and the importance of the production mechanisms for Titan's haze, have put forward the need to explore the mesosphere and the couplings between upper and lower atmosphere, as well as the current limits of available models.

scholarly journals Large-scale emergence of regional changes in year-to-year temperature variability by the end of the 21st century

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Dirk Olonscheck ◽  
Andrew P. Schurer ◽  
Lucie Lücke ◽  
Gabriele C. Hegerl
Keyword(s):  
Global Warming ◽  
Large Scale ◽  
Climate Model ◽  
Climate Extremes ◽  
Temperature Variability ◽  
High Latitudes ◽  
Large Ensembles ◽  
Proxy Reconstructions ◽  
Instrumental Records ◽  
The Tropics

AbstractGlobal warming is expected to not only impact mean temperatures but also temperature variability, substantially altering climate extremes. Here we show that human-caused changes in internal year-to-year temperature variability are expected to emerge from the unforced range by the end of the 21st century across climate model initial-condition large ensembles forced with a strong global warming scenario. Different simulated changes in globally averaged regional temperature variability between models can be explained by a trade-off between strong increases in variability on tropical land and substantial decreases in high latitudes, both shown by most models. This latitudinal pattern of temperature variability change is consistent with loss of sea ice in high latitudes and changes in vegetation cover in the tropics. Instrumental records are broadly in line with this emerging pattern, but have data gaps in key regions. Paleoclimate proxy reconstructions support the simulated magnitude and distribution of temperature variability. Our findings strengthen the need for urgent mitigation to avoid unprecedented changes in temperature variability.

scholarly journals Can oceanic paleothermometers reconstruct the Atlantic Multidecadal Oscillation?

2010 ◽  
Vol 6 (5) ◽  
pp. 2177-2197 ◽  
Author(s):  
D. Heslop ◽  
A. Paul
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Large Scale ◽  
Climate Model ◽  
Low Frequency ◽  
Atlantic Multidecadal Oscillation ◽  
Sea Surface ◽  
Prediction Errors ◽  
The Past ◽  
Instrumental Records

Abstract. Instrumental records of North Atlantic sea surface temperature reveal a large-scale low frequency mode of variability that has become known as the Atlantic Multidecadal Oscillation (AMO). Proxy and modelling studies have demonstrated the important consequences of the AMO on other components of the climate system both within and outside the Atlantic region. Over longer time scales the past behavior of the AMO is predominantly constrained by terrestrial proxies and only a limited number of records are available from the marine realm itself. Here we use an Earth System-Climate Model of intermediate complexity to simulate AMO-type behavior in the Atlantic with a specific focus placed on the ability of ocean paleothermometers to capture the associated surface and subsurface temperature variability. Given their lower prediction errors and annual resolution, coral-based proxies of sea surface temperature appear to be capable of reconstructing the temperature variations associated with the past AMO with an adequate signal-to-noise ratio. Contrastingly, the relatively high prediction error and low temporal resolution of sediment-based proxies, such as the composition of foraminiferal calcite, limits their ability to produce interpretable records of past temperature anomalies corresponding to AMO activity.

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