SimCloud version 1.0: a simple diagnostic cloud scheme for idealized climate models

Abstract. A simple diagnostic cloud scheme (SimCloud) for general circulation models (GCMs), which has a modest level of complexity and is transparent in describing its dependence on tunable parameters, is proposed in this study. The large-scale clouds, which form the core of the scheme, are diagnosed from relative humidity. In addition, the marine low stratus clouds, typically found off the west coast of continents over subtropical oceans, are determined largely as a function of inversion strength. A “freeze-dry” adjustment based on a simple function of specific humidity is also available to reduce an excessive cloud bias in polar regions. Other cloud properties, such as the effective radius of cloud droplet and cloud liquid water content, are specified as simple functions of temperature. All of these features are user-configurable. The cloud scheme is implemented in Isca, a modeling framework designed to enable the construction of GCMs at varying levels of complexity, but could readily be adapted to other GCMs. Simulations using the scheme with realistic continents generally capture the observed structure of cloud fraction and cloud radiative effect (CRE), as well as its seasonal variation. Specifically, the explicit low-cloud scheme improves the simulation of shortwave CREs over the eastern subtropical oceans by increasing the cloud fraction and cloud water path. The freeze-dry adjustment alleviates the longwave CRE biases in polar regions, especially in winter. However, the longwave CRE in tropical regions and shortwave CRE over the extratropics are both still too strong compared to observations. Nevertheless, this simple cloud scheme provides a suitable basis for examining the impacts of clouds on climate in idealized modeling frameworks.

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SimCloud version 1.0: a simple diagnostic cloud scheme for idealized climate models

10.5194/gmd-2020-402 ◽

2020 ◽

Author(s):

Qun Liu ◽

Matthew Collins ◽

Penelope Maher ◽

Stephen I. Thomson ◽

Geoffrey K. Vallis

Keyword(s):

Relative Humidity ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

General Circulation Models ◽

Cloud Fraction ◽

Polar Regions ◽

Modeling Framework ◽

Tropical Regions ◽

Subtropical Oceans

Abstract. SimCloud, a simple diagnostic cloud scheme for general circulation models (GCMs) is proposed in this study. The large-scale clouds, which form the core of the scheme, are diagnosed from relative humidity. In addition, marine low stratus clouds, typically found off the west coast of continents over subtropical oceans, are determined largely as a function of inversion strength. A freeze-dry adjustment based on a simple function of relative humidity may also used to reduce an excessive clouds bias in polar regions. Other cloud properties, such as the effective radius of cloud droplet and cloud liquid water content, are specified as simple functions of temperature. All of these features are user-configurable. The cloud scheme is implemented in Isca, a modeling framework designed to enable the construction of GCMs at varying levels of complexity, but could readily be adapted to other GCMs. Simulations using the scheme with realistic continents generally capture the observed structure of cloud fraction and cloud radiative effect (CRE), as well as its seasonal variation. Specifically, the explicit low cloud scheme improves the simulation of shortwave CREs over the eastern subtropical oceans by increasing the cloud fraction and cloud water path over there. The freeze-dry adjustment alleviates the longwave CRE biases in polar regions especially in winter. However, the longwave CRE in tropical regions and shortwave CRE over extratropics are still too strong compared to observations. Nevertheless, this simple cloud scheme provides a suitable basis for examining the impacts of clouds on climate in idealized modeling frameworks.

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Polar meteorology: a review of some recent research

Polar Record ◽

10.1017/s0032247400031934 ◽

1974 ◽

Vol 17 (108) ◽

pp. 277-294 ◽

Cited By ~ 1

Author(s):

Gunter Weller

Keyword(s):

Heat Source ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

General Circulation Models ◽

Cloud Formation ◽

Driving Mechanism ◽

Polar Regions ◽

International Geophysical Year ◽

Polar Meteorology

The general large-scale circulation of the global atmosphere has its basic driving mechanism in the equator-poleward temperature gradients in both hemispheres. It has become increasingly obvious over the last few decades that to understand and predict the behaviour of the atmosphere at any point, it is essential to understand the behaviour of the total global fluid system. The Global Atmospheric Research Project (GARP) is an outcome of this recognition. Studies of the heat sinks (the polar regions) are therefore just as important as studies of the heat source (the equatorial regions) to understand the meteorology of the planet. Interest in polar meteorology has undergone many cyclic fluctuations, peaking during the various international polar years and, more recently, during the International Geophysical Year, 1957–58. At the present, the focus of GARP's first objective (improved extended weather forecasts) is on the tropical heat source, where convection and cloud formation and dissipation are still relatively little understood processes. However, the second GARP objective (better understanding of the physical basis of climate) requires more attention to be devoted to the cryosphere, its long-term interaction with oceans and atmosphere, and its role as an indicator of climatic change. The idea of a polar experiment (POLEX) was initially introduced by Treshnikov and others (1968) and by Borisenkov and Treshnikov (1971). A summary of the early history of POLEX was recently given by Weller and Bierly (1973). The two closely related objectives of POLEX that most directly pertain to GARP may be restated in their simplest terms as (1) a better understanding of energy transfer processes and the heat budgets of the polar regions for the purpose of parameterizing them properly in general circulation models and climate models, and (2) provision of adequate data from the polar regions during the First GARP Global Experiment (FGGE) in 1978.

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Climatology and Forcing of the Quasi-Biennial Oscillation in the MAECHAM5 Model

Journal of Climate ◽

10.1175/jcli3830.1 ◽

2006 ◽

Vol 19 (16) ◽

pp. 3882-3901 ◽

Cited By ~ 168

Author(s):

M. A. Giorgetta ◽

E. Manzini ◽

E. Roeckner ◽

M. Esch ◽

L. Bengtsson

Keyword(s):

Gravity Wave ◽

Zonal Wind ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

Middle Atmosphere ◽

General Circulation Models ◽

Wave Drag ◽

Quasi Biennial Oscillation ◽

Biennial Oscillation

Abstract The quasi-biennial oscillation (QBO) in the equatorial zonal wind is an outstanding phenomenon of the atmosphere. The QBO is driven by a broad spectrum of waves excited in the tropical troposphere and modulates transport and mixing of chemical compounds in the whole middle atmosphere. Therefore, the simulation of the QBO in general circulation models and chemistry climate models is an important issue. Here, aspects of the climatology and forcing of a spontaneously occurring QBO in a middle-atmosphere model are evaluated, and its influence on the climate and variability of the tropical middle atmosphere is investigated. Westerly and easterly phases are considered separately, and 40-yr ECMWF Re-Analysis (ERA-40) data are used as a reference where appropriate. It is found that the simulated QBO is realistic in many details. Resolved large-scale waves are particularly important for the westerly phase, while parameterized gravity wave drag is more important for the easterly phase. Advective zonal wind tendencies are important for asymmetries between westerly and easterly phases, as found for the suppression of the easterly phase downward propagation. The simulation of the QBO improves the tropical upwelling and the atmospheric tape recorder compared to a model without a QBO. The semiannual oscillation is simulated realistically only if the QBO is represented. In sensitivity tests, it is found that the simulated QBO is strongly sensitive to changes in the gravity wave sources. The sensitivity to the tested range of horizontal resolutions is small. The stratospheric vertical resolution must be better than 1 km to simulate a realistic QBO.

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Water resources of the Desna river basin under future climate

Journal of Water and Climate Change ◽

10.2166/wcc.2021.034 ◽

2021 ◽

Author(s):

Osypov Valeriy ◽

Speka Oleh ◽

Chyhareva Anastasiia ◽

Osadcha Nataliia ◽

Krakovska Svitlana ◽

...

Keyword(s):

Water Resources ◽

River Basin ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

Assessment Tool ◽

General Circulation Models ◽

Future Climate ◽

Moderate Increase ◽

Water Balance Components

Abstract Climate change impact on water resources has been observing in Ukraine since the end of the 20th century. For now, only large-scale climate impact studies cover Ukraine territory, having low credibility for a specific catchment. This study aims to calculate future changes in river discharge, water flow components, and soil water within the Desna basin and evaluate vulnerability trends on this basis. The framework assembles the process-based SWAT (Soil and Water Assessment Tool) model and eight high-resolution regional climate models (RCMs) driven by RCP4.5 and RCP8.5 emission scenarios. The climate models are provided by the Euro-CORDEX initiative and based on three RCMs (RCA4, HIRHAM5, and RACMO22E) forced by five general circulation models (CNRM-CM5, EC-EARTH, IPSL-CM5A-MR, HadGEM2-ES, and MPI-ESM-LR). The results preferably show a moderate increase in the annual discharge till the end of the 21st century. The intra-annual changes of water balance components negatively affect the vegetation period because of higher dryness and temperature stress but reduce flood risk, diffuse pollution, and water erosion in the far future. In the river basin management plan, the highest attention should be paid to adaptive strategies in agriculture because of possible water deficit in the vegetation season under future climate scenarios.

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Assessing the Representation of Australian Regional Climate Extremes and Their Associated Atmospheric Circulation in Climate Models

Journal of Climate ◽

10.1175/jcli-d-19-0287.1 ◽

2020 ◽

Vol 33 (4) ◽

pp. 1227-1245 ◽

Cited By ~ 2

Author(s):

Carly R. Tozer ◽

James S. Risbey ◽

Didier P. Monselesan ◽

Dougal T. Squire ◽

Matthew A. Chamberlain ◽

...

Keyword(s):

General Circulation ◽

Large Scale ◽

Climate Models ◽

Extreme Event ◽

Wave Train ◽

Regional Climate ◽

Climate Extremes ◽

General Circulation Models ◽

Dry Spells ◽

Rainfall Extremes

AbstractWe assess the representation of multiday temperature and rainfall extremes in southeast Australia in three coupled general circulation models (GCMs) of varying resolution. We evaluate the statistics of the modeled extremes in terms of their frequency, duration, and magnitude compared to observations, and the model representation of the midtropospheric circulation (synoptic and large scale) associated with the extremes. We find that the models capture the statistics of observed heatwaves reasonably well, though some models are “too wet” to adequately capture the observed duration of dry spells but not always wet enough to capture the magnitude of extreme wet events. Despite the inability of the models to simulate all extreme event statistics, the process evaluation indicates that the onset and decay of the observed synoptic structures are well simulated in the models, including for wet and dry extremes. We also show that the large-scale wave train structures associated with the observed extremes are reasonably well simulated by the models although their broader onset and decay is not always captured in the models. The results presented here provide some context for, and confidence in, the use of the coupled GCMs in climate prediction and projection studies for regional extremes.

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The Energetics of Ocean Heat Transport

Journal of Climate ◽

10.1175/jcli3436.1 ◽

2005 ◽

Vol 18 (14) ◽

pp. 2604-2616 ◽

Cited By ~ 69

Author(s):

Anand Gnanadesikan ◽

Richard D. Slater ◽

P. S. Swathi ◽

Geoffrey K. Vallis

Keyword(s):

Heat Transport ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

Thermohaline Circulation ◽

Mechanical Energy ◽

General Circulation Models ◽

Ocean Heat Transport ◽

Energy Of Mixing ◽

The Relationship

Abstract A number of recent papers have argued that the mechanical energy budget of the ocean places constraints on how the thermohaline circulation is driven. These papers have been used to argue that climate models, which do not specifically account for the energy of mixing, potentially miss a very important feedback on climate change. This paper reexamines the question of what energetic arguments can teach us about the climate system and concludes that the relationship between energetics and climate is not straightforward. By analyzing the buoyancy transport equation, it is demonstrated that the large-scale transport of heat within the ocean requires an energy source of around 0.2 TW to accomplish vertical transport and around 0.4 TW (resulting from cabbeling) to accomplish horizontal transport. Within two general circulation models, this energy is almost entirely supplied by surface winds. It is also shown that there is no necessary relationship between heat transport and mechanical energy supply.

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A new spatially distributed Added Value Index for Regional Climate Models: the EURO-CORDEX and the CORDEX-CORE highest resolution ensembles

10.5194/egusphere-egu2020-2611 ◽

2020 ◽

Author(s):

James M. Ciarlo` ◽

Erika Coppola ◽

Adriano Fantini ◽

XueJie Gao ◽

Yao Tong ◽

...

Keyword(s):

General Circulation ◽

Climate Models ◽

Regional Climate ◽

Regional Climate Models ◽

General Circulation Models ◽

New Method ◽

Added Value ◽

Tropical Regions ◽

Spatially Distributed ◽

Rcp 8.5

<p>Regional Climate Models (RCMs) have undergone substantial development, resulting in increasingly reliable high-resolution simulations. Despite this, the added value of these simulations compared to their driving General Circulation Models (GCMs) has been a recurring issue. Past studies have used different techniques to quantify the added value of a RCM. A new method is now being presented, based on these past studies, that quantifies the added value and presents it spatially. The method was also adapted to assess the Downscaling Signal (DS) in climate change simulations and compare this to the added value.</p><p>This new method has been used to assess the daily precipitation of the 55-model EURO-CORDEX ensemble and the CORDEX-CORE ensemble, focusing especially on the higher-end of the PDFs. This revealed an overall positive added value across all domains, especially in areas of complex topography, cost-lines, and tropical regions. This DS was similar to that of the added value when looking at RCP 8.5 far-future simulations.</p>

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Investigating the consistency between proxy-based reconstructions and climate models using data assimilation: a mid-Holocene case study

Climate of the Past ◽

10.5194/cp-9-2741-2013 ◽

2013 ◽

Vol 9 (6) ◽

pp. 2741-2757 ◽

Cited By ~ 20

Author(s):

A. Mairesse ◽

H. Goosse ◽

P. Mathiot ◽

H. Wanner ◽

S. Dubinkina

Keyword(s):

Data Assimilation ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

General Circulation Models ◽

Standard Test ◽

Reconstructed Signal ◽

Paleoclimate Records ◽

Using Data

Abstract. The mid-Holocene (6 kyr BP; thousand years before present) is a key period to study the consistency between model results and proxy-based reconstruction data as it corresponds to a standard test for models and a reasonable number of proxy-based records is available. Taking advantage of this relatively large amount of information, we have compared a compilation of 50 air and sea surface temperature reconstructions with the results of three simulations performed with general circulation models and one carried out with LOVECLIM, a model of intermediate complexity. The conclusions derived from this analysis confirm that models and data agree on the large-scale spatial pattern but the models underestimate the magnitude of some observed changes and that large discrepancies are observed at the local scale. To further investigate the origin of those inconsistencies, we have constrained LOVECLIM to follow the signal recorded by the proxies selected in the compilation using a data-assimilation method based on a particle filter. In one simulation, all the 50 proxy-based records are used while in the other two only the continental or oceanic proxy-based records constrain the model results. As expected, data assimilation leads to improving the consistency between model results and the reconstructions. In particular, this is achieved in a robust way in all the experiments through a strengthening of the westerlies at midlatitude that warms up northern Europe. Furthermore, the comparison of the LOVECLIM simulations with and without data assimilation has also objectively identified 16 proxy-based paleoclimate records whose reconstructed signal is either incompatible with the signal recorded by some other proxy-based records or with model physics.

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Quantification of Uncertainty in High-Resolution Temperature Scenarios for North America

Journal of Climate ◽

10.1175/jcli-d-11-00217.1 ◽

2012 ◽

Vol 25 (9) ◽

pp. 3373-3389 ◽

Cited By ~ 20

Author(s):

Guilong Li ◽

Xuebin Zhang ◽

Francis Zwiers ◽

Qiuzi H. Wen

Keyword(s):

High Resolution ◽

North America ◽

General Circulation ◽

Large Scale ◽

Climate Models ◽

Internal Variability ◽

General Circulation Models ◽

First Century ◽

Small Scale ◽

Twenty First Century

A framework for the construction of probabilistic projections of high-resolution monthly temperature over North America using available outputs of opportunity from ensembles of multiple general circulation models (GCMs) and multiple regional climate models (RCMs) is proposed. In this approach, a statistical relationship is first established between RCM output and that from the respective driving GCM and then this relationship is applied to downscale outputs from a larger number of GCM simulations. Those statistically downscaled projections were used to estimate empirical quantiles at high resolution. Uncertainty in the projected temperature was partitioned into four sources including differences in GCMs, internal variability simulated by GCMs, differences in RCMs, and statistical downscaling including internal variability at finer spatial scale. Large spatial variability in projected future temperature changes is found, with increasingly larger changes toward the north in winter temperature and larger changes in the central United States in summer temperature. Under a given emission scenario, downscaling from large scale to small scale is the most important source of uncertainty, though structural errors in GCMs become equally important by the end of the twenty-first century. Different emission scenarios yield different projections of temperature change. This difference increases with time. The difference between the IPCC’s Special Report on Emissions Scenarios (SRES) A2 and B1 in the median values of projected changes in 30-yr mean temperature is small for the coming 30 yr, but can become almost as large as the total variance due to internal variability and modeling errors in both GCM and RCM later in the twenty-first century.

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Review on Applications of 17O in Hydrological Cycle

Molecules ◽

10.3390/molecules26154468 ◽

2021 ◽

Vol 26 (15) ◽

pp. 4468

Author(s):

Yalalt Nyamgerel ◽

Yeongcheol Han ◽

Minji Kim ◽

Dongchan Koh ◽

Jeonghoon Lee

Keyword(s):

Water Vapor ◽

General Circulation ◽

Hydrological Cycle ◽

General Circulation Models ◽

Convective Precipitation ◽

Subsurface Water ◽

Polar Regions ◽

Sea Ice Concentration ◽

Moisture Source ◽

Depositional Processes

The triple oxygen isotopes (16O, 17O, and 18O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of 17O in hydrological studies. Dual-inlet isotope ratio mass spectrometry and laser absorption spectroscopy have been used to measure 17O, which provides information on atmospheric conditions at the moisture source and isotopic fractionations during transport and deposition processes. The variations of δ17O from the developed global meteoric water line, with a slope of 0.528, indicate the importance of regional or local effects on the 17O distribution. In polar regions, factors such as the supersaturation effect, intrusion of stratospheric vapor, post-depositional processes (local moisture recycling through sublimation), regional circulation patterns, sea ice concentration and local meteorological conditions determine the distribution of 17O-excess. Numerous studies have used these isotopes to detect the changes in the moisture source, mixing of different water vapor, evaporative loss in dry regions, re-evaporation of rain drops during warm precipitation and convective storms in low and mid-latitude waters. Owing to the large variation of the spatial scale of hydrological processes with their extent (i.e., whether the processes are local or regional), more studies based on isotopic composition of surface and subsurface water, convective precipitation, and water vapor, are required. In particular, in situ measurements are important for accurate simulations of atmospheric hydrological cycles by isotope-enabled general circulation models.

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