scholarly journals Precipitation Characteristics in Eighteen Coupled Climate Models

2006 ◽  
Vol 19 (18) ◽  
pp. 4605-4630 ◽  
Author(s):  
Aiguo Dai
Keyword(s):  
Climate Models ◽  
Global Climate Model ◽  
Precipitation Amount ◽  
Total Precipitation ◽  
Coupled Models ◽  
Central Pacific ◽  
Coupled Climate Models ◽  
Low Latitudes ◽  
Stratiform Precipitation ◽  
Precipitation Ratio

Abstract Monthly and 3-hourly precipitation data from twentieth-century climate simulations by the newest generation of 18 coupled climate system models are analyzed and compared with available observations. The characteristics examined include the mean spatial patterns, intraseasonal-to-interannual and ENSO-related variability, convective versus stratiform precipitation ratio, precipitation frequency and intensity for different precipitation categories, and diurnal cycle. Although most models reproduce the observed broad patterns of precipitation amount and year-to-year variability, models without flux corrections still show an unrealistic double-ITCZ pattern over the tropical Pacific, whereas the flux-corrected models, especially the Meteorological Research Institute (MRI) Coupled Global Climate Model (CGCM; version 2.3.2a), produce realistic rainfall patterns at low latitudes. As in previous generations of coupled models, the rainfall double ITCZs are related to westward expansion of the cold tongue of sea surface temperature (SST) that is observed only over the equatorial eastern Pacific but extends to the central Pacific in the models. The partitioning of the total variance of precipitation among intraseasonal, seasonal, and longer time scales is generally reproduced by the models, except over the western Pacific where the models fail to capture the large intraseasonal variations. Most models produce too much convective (over 95% of total precipitation) and too little stratiform precipitation over most of the low latitudes, in contrast to 45%–65% in convective form in the Tropical Rainfall Measuring Mission (TRMM) satellite observations. The biases in the convective versus stratiform precipitation ratio are linked to the unrealistically strong coupling of tropical convection to local SST, which results in a positive correlation between the standard deviation of Niño-3.4 SST and the local convective-to-total precipitation ratio among the models. The models reproduce the percentage of the contribution (to total precipitation) and frequency for moderate precipitation (10–20 mm day−1), but underestimate the contribution and frequency for heavy (>20 mm day−1) and overestimate them for light (<10 mm day−1) precipitation. The newest generation of coupled models still rains too frequently, mostly within the 1–10 mm day−1 category. Precipitation intensity over the storm tracks around the eastern coasts of Asia and North America is comparable to that in the ITCZ (10–12 mm day−1) in the TRMM data, but it is much weaker in the models. The diurnal analysis suggests that warm-season convection still starts too early in these new models and occurs too frequently at reduced intensity in some of the models. The results show that considerable improvements in precipitation simulations are still desirable for the latest generation of the world’s coupled climate models.

EL NINO EFFECTS ON THE ARCTIC STRATOSPHERE ACCORDING TO CMIP5 MODELS AND REANALYSIS

2021 ◽  
pp. 5-23
Author(s):  
M. A. Kolennikova ◽  
◽  
P. N. Vargin ◽  
D. Yu. Gushchina ◽  
◽  
...  
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Reanalysis Data ◽  
The Arctic ◽  
Cmip5 Models ◽  
Composite Analysis ◽  
Central Pacific ◽  
Coupled Climate Models

The response of the Arctic stratosphere to El Nio is studied with account of its Eastern and Central Pacific types for the period of 1950-2005. The study is based on the regression and composite analysis using the simulations with six CMIP5 coupled climate models and reanalysis data.

scholarly journals Effect of Model Resolution on Intense and Extreme Precipitationinthe Mediterranean Region

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 699
Author(s):  
Dario Conte ◽  
Silvio Gualdi ◽  
Piero Lionello
Keyword(s):  
Climate Change ◽  
Mediterranean Region ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Global Climate Models ◽  
Total Precipitation ◽  
Model Resolution

This study explores the role of model resolution on the simulation of precipitation and on the estimate of its future change in the Mediterranean region. It compares the results of two regional climate models (RCMs, with two different horizontal grid resolutions, 0.44 and 0.11 degs, covering the whole Mediterranean region) and of the global climate model (GCM, 0.75 degs) that has provided the boundary conditions for them. The regional climate models include an interactive oceanic component with a resolution of 1/16 degs. The period 1960–2100 and the representative concentration pathways RCP4.5 and RCP8.5 are considered. The results show that, in the present climate, increasing resolution increases total precipitation and its extremes over steep orography, while it has the opposite effect over flat areas and the sea. Considering climate change, in all simulations, total precipitation will decrease over most of the considered domain except at the northern boundary, where it will increase. Extreme precipitation will increase over most of the northern Mediterranean region and decrease over the sea and some southern areas. Further, the overall probability of precipitation (frequency of wet days) significantly decreases over most of the region, but wet days will be characterized with precipitation intensity higher than the present. Our analysis shows that: (1) these projected changes are robust with respect to the considered range of model resolution; (2) increasing the resolution (within the considered resolution range) decreases the magnitude of these climate change effects. However, it is likely that resolution plays a less important role than other factors, such as the different physics of regional and global climate models. It remains to be investigated whether further increasing the resolution (and reaching the scale explicitly permitting convection) would change this conclusion.

scholarly journals Verification of the EURO-CORDEX RCM Historical Run Results over the Pannonian Basin for the Summer Season

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 714
Author(s):  
Irida Lazić ◽  
Milica Tošić ◽  
Vladimir Djurdjević
Keyword(s):  
Air Temperature ◽  
Climate Models ◽  
Climate Model ◽  
Dynamical Downscaling ◽  
Pannonian Basin ◽  
Global Climate Model ◽  
Precipitation Amount ◽  
Summer Season ◽  
Positive Temperature ◽  
Near Surface

In previous projects that focused on dynamical downscaling over Europe, e.g., PRUDENCE and ENSEMBLES, many regional climate models (RCMs) tended to overestimate summer air temperature and underestimate precipitation in this season in Southern and Southeastern Europe, leading to the so-called summer drying problem. This bias pattern occurred not only in the RCM results but also in the global climate model (GCM) results, so knowledge of the model uncertainties and their cascade is crucial for understanding and interpreting future climate. Our intention with this study was to examine whether a warm-and-dry bias is also present in the state-of-the-art EURO-CORDEX multi-model ensemble results in the summer season over the Pannonian Basin. Verification of EURO-CORDEX RCMs was carried out by using the E-OBS gridded dataset of daily mean, minimum, and maximum near-surface air temperature and total precipitation amount with a horizontal resolution of 0.1 degrees (approximately 12 km × 12 km) over the 1971–2000 time period. The model skill for selected period was expressed in terms of four verification scores: bias, centered root mean square error (RMSE), spatial correlation coefficient, and standard deviation. The main findings led us to conclude that most of the RCMs that overestimate temperature also underestimate precipitation. For some models, the positive temperature and negative precipitation bias were more emphasized, which led us to conclude that the problem was still present in most of the analyzed simulations.

scholarly journals Comparison of warming trends predicted over the next century around Antarctica from two coupled models

1998 ◽  
Vol 27 ◽  
pp. 576-582 ◽  
Author(s):  
Siobhan P. O'Farrell ◽  
William M. Connolley
Keyword(s):  
Climate Models ◽  
Winter Season ◽  
Drake Passage ◽  
Weddell Sea ◽  
Coupled Models ◽  
Coupled Climate Models ◽  
Temperature Signal ◽  
Antarctic Continent ◽  
Definition Of ◽  
The Antarctic

This paper investigales the climate change in two atmosphere ice-ocean coupled climate models — the UKMO and the CSIRO— in the Antarctic region over the next century. The objectives were to sec if an enhanced level of greenhouse-gas forcing results in a surface temperature signal above background variability, and to see if this pattern of change resembles the change seen to date in Antarctica, especially the warming around the Peninsula. The models show that although reduced sea-ice compactness is responsible for regions of enhanced air-temperature anomalies, these ice-compactness anomalies are determined by different mechanisms in the respective models. The pattern of warming in both models does not match the differential rates of warming seen in the observations of temperature change over the Antarctic continent in the lait few decades. Also the level of background ocean variability in the Drake Passage and Weddell Sea region hampers the clear definition of a signal over the Antarctic Peninsula in the coupled models. Although no winter enhancement in warming over the Peninsula region IS found, an autumn anomaly is seen in one of the models. The mechanism for this feature IS documented, and an explanation of why it does not persist throughout the winter season is presented.

scholarly journals Contributions of the Liquid and Ice Phases to Global Surface Precipitation: Observations and Global Climate Modeling

2020 ◽  
Vol 77 (8) ◽  
pp. 2629-2648 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Carl Schmitt ◽  
Chih-Chieh-Jack Chen ◽  
Aaron Bansemer ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Climate Model ◽  
Climate Modeling ◽  
Global Climate ◽  
Global Climate Model ◽  
Precipitation Amount ◽  
Precipitation Process ◽  
Total Precipitation ◽  
Surface Precipitation ◽  
Freezing Level ◽  
Global Climate Modeling

Abstract This study is the first to reach a global view of the precipitation process partitioning, using a combination of satellite and global climate modeling data. The pathways investigated are 1) precipitating ice (ice/snow/graupel) that forms above the freezing level and melts to produce rain (S) followed by additional condensation and collection as the melted precipitating ice falls to the surface (R); 2) growth completely through condensation and collection (coalescence), warm rain (W); and 3) precipitating ice (primarily snow) that falls to the surface (SS). To quantify the amounts, data from satellite-based radar measurements—CloudSat, GPM, and TRMM—are used, as well as climate model simulations from the Community Atmosphere Model (CAM) and the Met Office Unified Model (UM). Total precipitation amounts and the fraction of the total precipitation amount for each of the pathways is examined latitudinally, regionally, and globally. Carefully examining the contributions from the satellite-based products leads to the conclusion that about 57% of Earth’s precipitation follows pathway S, 15% R, 23% W, and 5% SS, each with an uncertainty of ±5%. The percentages differ significantly from the global climate model results, with the UM indicating smaller fractional S, more R, and more SS; and CAM showing appreciably greater S, negative R (indicating net evaporation below the melting layer), a much larger percentage of W and much less SS. Possible reasons for the wide differences between the satellite- and model-based results are discussed.

Changes to ENSO under CO2 Doubling in a Multimodel Ensemble

2006 ◽  
Vol 19 (16) ◽  
pp. 4009-4027 ◽  
Author(s):  
William J. Merryfield
Keyword(s):  
Wave Speed ◽  
Climate Models ◽  
Relative Increase ◽  
Multimodel Ensemble ◽  
Central Pacific ◽  
Intergovernmental Panel ◽  
Surface Warming ◽  
Coupled Climate Models ◽  
Equatorial Wave ◽  
Induced Changes

Abstract An EOF analysis is used to intercompare the response of ENSO-like variability to CO2 doubling in results from 15 coupled climate models assembled for the Intergovernmental Panel on Climate Change Fourth Assessment Report. Under preindustrial conditions, 12 of the 15 models exhibit ENSO amplitudes comparable to or exceeding that observed in the second half of the twentieth century. Under CO2 doubling, three of the models exhibit statistically significant (p < 0.1) increases in ENSO amplitude, and five exhibit significant decreases. The overall amplitude changes are not strongly related to the magnitude or pattern of surface warming. It is, however, found that ENSO amplitude decreases (increases) in models having a narrow (wide) ENSO zonal wind stress response and ENSO amplitude comparable to or greater than observed. The models exhibit a mean fractional decrease in ENSO period of about 5%. Although many factors can influence the ENSO period, it is suggested that this may be related to a comparable increase in equatorial wave speed through an associated speedup of delayed-oscillator feedback. Changes in leading EOF, characterized in many of the models by a relative increase in the amplitude of SST variations in the central Pacific, are in most cases consistent with effects of anomalous zonal and vertical advection resulting from warming-induced changes in SST.

scholarly journals How does ocean ventilation change under global warming?

Ocean Science ◽  
2007 ◽  
Vol 3 (1) ◽  
pp. 43-53 ◽  
Author(s):  
A. Gnanadesikan ◽  
J. L. Russell ◽  
Keyword(s):  
Global Warming ◽  
Climate Models ◽  
Critical Role ◽  
The Arctic ◽  
Oxygen Minimum Zones ◽  
Ocean Ventilation ◽  
Deep Waters ◽  
Coupled Climate Models ◽  
Low Latitudes ◽  
Oxygen Minimum

Abstract. Since the upper ocean takes up much of the heat added to the earth system by anthropogenic global warming, one would expect that global warming would lead to an increase in stratification and a decrease in the ventilation of the ocean interior. However, multiple simulations in global coupled climate models using an ideal age tracer which is set to zero in the mixed layer and ages at 1 yr/yr outside this layer show that the intermediate depths in the low latitudes, Northwest Atlantic, and parts of the Arctic Ocean become younger under global warming. This paper reconciles these apparently contradictory trends, showing that the decreases result from changes in the relative contributions of old deep waters and younger surface waters. Implications for the tropical oxygen minimum zones, which play a critical role in global biogeochemical cycling are considered in detail.

scholarly journals How does ocean ventilation change under global warming?

2006 ◽  
Vol 3 (4) ◽  
pp. 805-826
Author(s):  
A. Gnanadesikan ◽  
J. L. Russell ◽  
F. Zeng
Keyword(s):  
Global Warming ◽  
Mixed Layer ◽  
Climate Models ◽  
Upper Ocean ◽  
Earth System ◽  
Ocean Ventilation ◽  
The Earth ◽  
Biological Cycling ◽  
Coupled Climate Models ◽  
Low Latitudes

Abstract. Since the upper ocean takes up much of the heat added to the earth system by anthropogenic global warming, one would expect that global warming would lead to an increase in stratification and a decrease in the ventilation of the ocean interior. However, multiple simulations in global coupled climate models using an ideal age tracer which is set to zero in the mixed layer and ages at 1 yr/yr outside this layer show that the intermediate depths in the low latitudes become younger under global warming. This paper reconciles these apparently contradictory trends, showing that a decrease in upwelling of old water from below is responsible for the change. Implications for global biological cycling are considered.

scholarly journals Antarctic Ocean and Sea Ice Response to Ozone Depletion: A Two-Time-Scale Problem

2015 ◽  
Vol 28 (3) ◽  
pp. 1206-1226 ◽  
Author(s):  
David Ferreira ◽  
John Marshall ◽  
Cecilia M. Bitz ◽  
Susan Solomon ◽  
Alan Plumb
Keyword(s):  
Sea Ice ◽  
Time Scale ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Southern Annular Mode ◽  
Ozone Hole ◽  
Coupled Models ◽  
Sea Ice Extent

Abstract The response of the Southern Ocean to a repeating seasonal cycle of ozone loss is studied in two coupled climate models and is found to comprise both fast and slow processes. The fast response is similar to the interannual signature of the southern annular mode (SAM) on sea surface temperature (SST), onto which the ozone hole forcing projects in the summer. It comprises enhanced northward Ekman drift, inducing negative summertime SST anomalies around Antarctica, earlier sea ice freeze-up the following winter, and northward expansion of the sea ice edge year-round. The enhanced northward Ekman drift, however, results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice. With sustained bursts of westerly winds induced by ozone hole depletion, this warming from below eventually dominates over the cooling from anomalous Ekman drift. The resulting slow time-scale response (years to decades) leads to warming of SSTs around Antarctica and ultimately a reduction in sea ice cover year-round. This two-time-scale behavior—rapid cooling followed by slow but persistent warming—is found in the two coupled models analyzed: one with an idealized geometry and the other with a complex global climate model with realistic geometry. Processes that control the time scale of the transition from cooling to warming and their uncertainties are described. Finally the implications of these results are discussed for rationalizing previous studies of the effect of the ozone hole on SST and sea ice extent.

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