Downscaling general circulation model output: a review of methods and limitations

General circulation models (GCMs) suggest that rising concentrations of greenhouse gases may have significant consequences for the global climate. What is less clear is the extent to which local (subgrid) scale meteorological processes will be affected. So-called 'downscaling' techniques have subsequently emerged as a means of bridging the gap between what climate modellers are currently able to provide and what impact assessors require. This article reviews the present generation of downscaling tools under four main headings: regression methods; weather pattern (circulation)-based approaches; stochastic weather generators; and limited-area climate models. The penultimate section summarizes the results of an international experiment to intercompare several precipitation models used for downscaling. It shows that circulation-based downscaling methods perform well in simulating present observed and model-generated daily precipitation characteristics, but are able to capture only part of the daily precipitation variability changes associated with model-derived changes in climate. The final section examines a number of ongoing challenges to the future development of climate downscaling.

Download Full-text

Boundary conditions for the Middle Miocene Climate Transition (MMCT v1.0)

10.5194/gmd-2017-171 ◽

2017 ◽

Author(s):

Amanda Frigola ◽

Matthias Prange ◽

Michael Schulz

Keyword(s):

Boundary Conditions ◽

General Circulation ◽

Middle Miocene ◽

Climate Models ◽

Global Climate ◽

Co2 Concentration ◽

General Circulation Models ◽

Global Climate Models ◽

Ice Volume ◽

Climate Transition

Abstract. The Middle Miocene Climate Transition was characterized by major Antarctic ice-sheet expansion and global cooling during the interval ~ 15–13 Ma. Here we present two sets of boundary conditions for global general circulation models characterizing the periods before (Middle Miocene Climatic Optimum; MMCO) and after (Middle Miocene Glaciation; MMG) the transition. These boundary conditions include Middle Miocene global topography, bathymetry and vegetation. Additionally, Antarctic ice volume and geometry, sea-level and atmospheric CO2 concentration estimates for the MMCO and the MMG are reviewed. The boundary-condition files are available for use as input in a wide variety of global climate models and constitute a valuable tool for modeling studies with a focus on the Middle Miocene.

Download Full-text

The Response of the Midlatitude Jet to Regional Polar Heating in a Simple Storm-Track Model

Journal of Climate ◽

10.1175/jcli-d-18-0257.1 ◽

2019 ◽

Vol 32 (10) ◽

pp. 2869-2885

Author(s):

Paolo Ruggieri ◽

Fred Kucharski ◽

Lenka Novak

Keyword(s):

General Circulation ◽

State Of The Art ◽

Global Climate ◽

Storm Track ◽

Circulation Model ◽

General Circulation Models ◽

Arctic Sea Ice ◽

The Arctic ◽

Strong Response ◽

Arctic Sea

Abstract Given the recent changes in the Arctic sea ice, understanding the effects of the resultant polar warming on the global climate is of great importance. However, the interaction between the Arctic and midlatitude circulation involves a complex chain of mechanisms, which leaves state-of-the-art general circulation models unable to represent this interaction unambiguously. This study uses an idealized general circulation model to provide a process-based understanding of the sensitivity of the midlatitude circulation to the location of high-latitude warming. A simplified atmosphere is simulated with a single zonally localized midlatitude storm track, which is analogous to the storm tracks in the Northern Hemisphere. It is found that even small changes in the position of the forcing relative to that storm track can lead to very different responses in the midlatitude circulation. More specifically, it is found that heating concentrated in one region may cause a substantially stronger global response compared to when the same amount of heating is distributed across all longitudes at the same latitude. Linear interference between climatological and anomalous flow is an important component of the response, but it does not explain differences between different longitudes of the forcing. Feedbacks from atmospheric transient eddies are found to be associated with this strong response. A dependence between the climatological jet latitude and the jet response to polar surface heating is found. These results can be used to design and interpret experiments with complex state-of-the-art models targeted at Arctic–midlatitude interactions.

Download Full-text

On the potential use of glacier and permafrost observations for verification of climate models

Annals of Glaciology ◽

10.1017/s026030550001435x ◽

1997 ◽

Vol 25 ◽

pp. 400-406 ◽

Cited By ~ 2

Author(s):

Martin Beniston ◽

Wilfried Haeberli ◽

Martin Hoelzle ◽

Alan Taylor

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Regional Climate ◽

Model Performance ◽

Regional Climate Models ◽

General Circulation Models ◽

Model Verification ◽

Dominant Feature

While the capability of global and regional climate models in reproducing current climate has significantly improved over the past few years, the confidence in model results for remote regions, or those where complex orography is a dominant feature, is still relatively low. This is, in part, linked to the lack of observational data for model verification and intercomparison purposes.Glacier and permafrost observations are directly related to past and present energy flux patterns at the Earth-atmosphere interface and could be used as a proxy for air temperature and precipitation, particularly of value in remote mountain regions and boreal and Arctic zones where instrumental climate records are sparse or non-existent. It is particularly important to verify climate-model performance in these regions, as this is where most general circulation models (GCMs) predict the greatest changes in air temperatures in a warmer global climate.Existing datasets from glacier and permafrost monitoring sites in remote and high altitudes are described in this paper; the data could be used in model-verification studies, as a means to improving model performance in these regions.

Download Full-text

Potential changes in the number of wet days and its effect on future intense and annual precipitation in northern Oman

Hydrology Research ◽

10.2166/nh.2017.188 ◽

2017 ◽

Vol 49 (1) ◽

pp. 237-250 ◽

Cited By ~ 3

Author(s):

Luminda Niroshana Gunawardhana ◽

Ghazi A. Al-Rawas ◽

Andy Y. Kwarteng ◽

Malik Al-Wardy ◽

Yassine Charabi

Keyword(s):

General Circulation ◽

Climate Models ◽

Coastal Region ◽

General Circulation Models ◽

Precipitation Intensity ◽

Annual Precipitation ◽

Monsoon Period ◽

Precipitation Characteristics ◽

The Future ◽

Precipitation Records

Abstract The changes in the number of wet days (NWD) in Oman projected by climate models was analyzed, focusing mostly on variation of precipitation intensity and its effect on total annual precipitation (PTOT) in the future. The daily precipitation records of 49 gage stations were divided into five regions. Of the five general circulation models studied, two of them were selected based on their performance to simulate local-scale precipitation characteristics. All regions studied, except the interior desert region of the country, could experience fewer wet days in the future, with the most significant decreases estimated in southern Oman. The contribution from the cold frontal troughs to the PTOT in the northeast coastal region would decrease from 85% in the 1985–2004 period to 79% during the 2040–2059 period and further decrease to 77% during the 2080–2099 period. In contrast, results depict enhanced tropical cyclone activities in the northeast coastal region during the post-monsoon period. Despite the decreases in the NWD, PTOT in all regions would increase by 6–29% and 35–67% during the 2040–2059 and 2080–2099 periods, respectively. These results, therefore, show that increases in precipitation intensity dominate the changes in PTOT.

Download Full-text

The Climatology of the Atmospheric Boundary Layer in Contemporary Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-17-0498.1 ◽

2018 ◽

Vol 31 (22) ◽

pp. 9151-9173 ◽

Cited By ~ 6

Author(s):

Richard Davy

Keyword(s):

Boundary Layer ◽

General Circulation ◽

Climate Models ◽

Global Climate ◽

Coupled Model ◽

General Circulation Models ◽

Global Climate Models ◽

Cmip5 Models ◽

Seasonal Cycles ◽

Layer Depth

Here, we present the climatology of the planetary boundary layer depth in 18 contemporary general circulation models (GCMs) in simulations of the late-twentieth-century climate that were part of phase 5 of the Coupled Model Intercomparison Project (CMIP5). We used a bulk Richardson methodology to establish the boundary layer depth from the 6-hourly synoptic-snapshot data available in the CMIP5 archives. We present an ensemble analysis of the climatological mean, diurnal cycle, and seasonal cycle of the boundary layer depth in these models and compare it to the climatologies from the ECMWF ERA-Interim reanalysis. Overall, we find that the CMIP5 models do a reasonably good job of reproducing the distribution of mean boundary layer depth, although the geographical patterns vary considerably between models. However, the models are biased toward weaker diurnal and seasonal cycles in the boundary layer depth and generally produce much deeper boundary layers at night and during the winter than are found in the reanalysis. These biases are likely to reduce the ability of these models to accurately represent other properties of the diurnal and seasonal cycles, and the sensitivity of these cycles to climate change.

Download Full-text

Evaluation of data-driven models to downscale rainfall parameters from global climate models outputs: the case study of Latyan watershed

Journal of Water and Climate Change ◽

10.2166/wcc.2018.191 ◽

2018 ◽

Vol 11 (1) ◽

pp. 200-216 ◽

Cited By ~ 2

Author(s):

Reza Haji Hosseini ◽

Saeed Golian ◽

Jafar Yazdi

Keyword(s):

Climate Change ◽

General Circulation ◽

Climate Models ◽

Fuzzy Inference ◽

Global Climate ◽

General Circulation Models ◽

Global Climate Models ◽

Data Driven ◽

Observation Data ◽

Inference System

Abstract Assessment of climate change in future periods is considered necessary, especially with regard to probable changes to water resources. One of the methods for estimating climate change is the use of the simulation outputs of general circulation models (GCMs). However, due to the low resolution of these models, they are not applicable to regional and local studies and downscaling methods should be applied. The purpose of the present study was to use GCM models' outputs for downscaling precipitation measurements at Amameh station in Latyan dam basin. For this purpose, the observation data from the Amameh station during the 1980–2005 period, 26 output variables from two GCM models, namely, HadCM3 and CanESM2 were used. Downscaling was performed by three data-driven methods, namely, artificial neural network (ANN), nonparametric K-nearest neighborhood (KNN) method, and adaptive network-based fuzzy inference system method (ANFIS). Comparison of the monthly results showed the superiority of KNN compared to the other two methods in simulating precipitation. However, all three, ANN, KNN, and ANFIS methods, showed satisfactory results for both HadDCM3 and CanESM2 GCM models in downscaling precipitation in the study area.

Download Full-text

California Wintertime Precipitation Bias in Regional and Global Climate Models

Journal of Applied Meteorology and Climatology ◽

10.1175/2010jamc2388.1 ◽

2010 ◽

Vol 49 (10) ◽

pp. 2147-2158 ◽

Cited By ~ 33

Author(s):

Peter Caldwell

Keyword(s):

General Circulation ◽

Climate Models ◽

Global Climate ◽

Regional Climate ◽

Regional Climate Models ◽

General Circulation Models ◽

Global Climate Models ◽

Model Resolution ◽

Grid Spacing ◽

Precipitation Frequency

Abstract In this paper, wintertime precipitation from a variety of observational datasets, regional climate models (RCMs), and general circulation models (GCMs) is averaged over the state of California and compared. Several averaging methodologies are considered and all are found to give similar values when the model grid spacing is less than 3°. This suggests that California is a reasonable size for regional intercomparisons using modern GCMs. Results show that reanalysis-forced RCMs tend to significantly overpredict California precipitation. This appears to be due mainly to the overprediction of extreme events; RCM precipitation frequency is generally underpredicted. Overprediction is also reflected in wintertime precipitation variability, which tends to be too high for RCMs on both daily and interannual scales. Wintertime precipitation in most (but not all) GCMs is underestimated. This is in contrast to previous studies based on global blended gauge–satellite observations, which are shown here to underestimate precipitation relative to higher-resolution gauge-only datasets. Several GCMs provide reasonable daily precipitation distributions, a trait that does not seem to be tied to model resolution. The GCM daily and interannual variabilities are generally underpredicted.

Download Full-text

Hydroclimate variability in Scandinavia over the last millennium – insights from a climate model-proxy data comparison

10.5194/cp-2017-36 ◽

2017 ◽

Cited By ~ 1

Author(s):

Kristina Seftigen ◽

Hugues Goosse ◽

Francois Klein ◽

Deliang Chen

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Model Performance ◽

Circulation Model ◽

Global Climate Models ◽

Last Millennium ◽

Atmospheric Variability ◽

Out Of Sample

Abstract. The integration of climate proxy information with General Circulation Model (GCM) results offers considerable potential for deriving greater understanding of the mechanisms underlying climate variability, as well as unique opportunities for out-of-sample evaluations of model performance. In this study, we combine insights from a new tree-ring hydroclimate reconstruction from Scandinavian with projections from a suite of forced transient simulations of the last millennium and historical intervals from the CMIP5 and PMIP3 archives. Model simulations and proxy reconstruction data are found to broadly agree on the modes of atmospheric variability that produces droughts/pluvials in the region. But despite these dynamical similarities, large differences between simulated and reconstructed hydroclimate time series remain. We find simulated interannual components of variability to be overestimated, while the multidecadal/longer timescale components generally are too weak. Specifically, summertime moisture variability and temperature are weakly negatively associated at inter-annual timescales but positively correlated at decadal timescales, revealed from observational and proxy evidences. On this background, the CMIP5/PMIP3 simulated timescale dependent relationship between regional precipitation and temperature is considerably biased, because the short-term negative association is overestimated, and the long-term relationship is significantly underestimated. The lack of adequate understanding for mechanisms linking temperature and moisture supply on longer timescales has important implication for future projections. Weak multidecadal variability in models also implies that inference about future persistent droughts and pluvials based on the latest generation global climate models will likely underestimate the true risk of these events.

Download Full-text

4. Modelling future climate

10.1093/actrade/9780198867869.003.0004 ◽

2021 ◽

pp. 44-63

Author(s):

Mark Maslin

Keyword(s):

Global Economy ◽

General Circulation ◽

Climate Models ◽

Driving Forces ◽

Global Climate ◽

Three Dimensional ◽

Ghg Emissions ◽

General Circulation Models ◽

Future Climate ◽

Box Models

‘Modelling future climate’ examines the modelling of future global climate. There is a whole hierarchy of climate models, from relatively simple box models to extremely complex three-dimensional general circulation models (GCMs). Each has a role in examining and furthering the understanding of the global climate system. At the heart of the climate models is the carbon cycle, central to estimating what happens to anthropogenic carbon dioxide and methane emissions. The biggest unknown in the models is the estimation of future human global GHG emissions. It is worth noting here the shared socioeconomic pathways (SSPs) and representative concentration pathways (RCPs), a set of narratives and driving forces that model the possible shape of the global economy and global emissions in the future. The latest IPCC projections on future global temperature, precipitation, and sea level based on the different SSPs make for interesting reading.

Download Full-text

Applying the new spatially distributed Added Value Index and Climate Change Downscaling Signal for Regional Climate Models to high-resolution EURO-CORDEX and convection permitting scale simulations

10.5194/egusphere-egu21-8849 ◽

2021 ◽

Author(s):

James Ciarlo ◽

Erika Coppola ◽

Emanuela Pichelli ◽

Jose Abraham Torres Alavez ◽

Keyword(s):

Climate Change ◽

High Resolution ◽

General Circulation ◽

Climate Models ◽

Daily Precipitation ◽

Regional Climate ◽

Regional Climate Models ◽

General Circulation Models ◽

Added Value ◽

Spatially Distributed

Downscaling data from General Circulation Models (GCMs) with Regional Climate Models (RCMs) is a computationally expensive process, even more so running at the convection permitting scale (CP). Despite the high-resolution products of these simulations, the Added Value (AV) of these runs compared to their driving models is an important factor for consideration. A new method was recently developed to quantify the AV of historical simulations as well as the Climate Change Downscaling Signal (CCDS) of forecast runs. This method presents these quantities spatially and thus the specific regions with the most AV can be identified and understood.An analysis of daily precipitation from a 55-model EURO-CORDEX ensemble (at 12 km resolution) was assessed using this method. It revealed positive AV throughout the domain with greater emphasis in regions of complex topography, coast-lines, and the tropics. Similar CCDS was obtained when assessing the RCP 8.5 far future runs in these domains. This paper looks more closely at the CCDS obtained with this method and compares it to other climate change signals described in other studies.The same method is now being applied to assess the AV and CCDS of daily precipitation from an ensemble of models at the CP scale (~3 km) over different domains within Europe. The current stage of the analysis is also looking into the AV of using hourly precipitation instead of daily.

Download Full-text