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1.
The coupled atmosphere–ocean Climate Model of the Centre National de Recherches Météorologiques (CNRM) has been used to run a time-dependent climate change experiment to study the impact of increasing amounts of greenhouse gases and aerosols on the simulated water cycle. This simulation has been initialised with the oceanic temperature and salinity profiles and the atmospheric trace gas concentrations observed in the 1950s, and has been carried out for 150 years after a 20-year spin-up. The simulated climate change has been analysed as the difference between two 30-year time slices: 1970–2000 and 2070–2100 respectively. The model achieves a reasonable simulation of present-day climate and simulates a general increase in precipitation throughout the twenty first century. The main exceptions are the subtropics, where the enhanced Hadley circulation has a drying impact, and the mid-latitude continents, where the increased evaporation in spring and decreased moisture convergence in summer lead to a relative summer drying. Global and regional analyses suggest that the precipitation increase is generally limited by a decrease in the water vapour cycling rate and in the precipitation efficiency, which appear as key parameters of the simulated water cycle. In order to reduce the spread between climate scenarios, more efforts should be devoted to estimate these parameters from satellite observations and meteorological analyses, and their possible evolution over recent decades. In the present study, the impacts of global warming on the surface hydrology have been also investigated. The main findings are the amplification of the annual cycle of soil moisture in the mid-and-high latitudes, and the decrease in the Northern Hemisphere snow cover, at a rate that is consistent with recent satellite estimations and should increase during the twenty first century. The runoff simulated over the 1950–2100 period has been converted into river flow using a linear river routeing model. The trends simulated over recent decades are surprisingly consistent with the river flow measurements available from the Global Runoff Data Centre. These trends can differ from those estimated over the whole 150-year integration, thereby indicating that it is not safe to predict hydrological impacts just by extrapolating the trends found in the available observations. Our climate model seems likely to provide qualitative hydrological scenarios over large river basins, but it still shows serious biases in the simulation of present-day river flows. Regional hydrological projections remain a challenge for the global climate modelling community and downscaling techniques are still necessary for this purpose.  相似文献   

2.
The hydrological cycle can influence climate through a great variety of processes. A good representation of the hydrological cycle in climate models is therefore crucial. Attempts to analyse the global hydrological cycle are hampered by a deficiency of suitable observations, particularly over the oceans. Fully coupled general circulation models are potentially powerful tools in interpreting the limited observational data in the context of large-scale freshwater exchanges. We have looked at large-scale aspects of the global freshwater budget in a simulation, of over 1000 years, by the Hadley Centre coupled climate model (HadCM3). Many aspects of the global hydrological cycle are well represented, but the model hydrological cycle appears to be too strong, with overly large precipitation and evaporation components in comparison with the observational datasets we have used. We show that the ocean basin-scale meridional transports of freshwater come into near balance with the surface freshwater fluxes on a time scale of about 400 years, with the major change being a relative increase of freshwater transport from the Southern Ocean into the Atlantic Ocean. Comparison with observations, supported by sensitivity tests, suggests that the major cause of a drift to more saline condition in the model Atlantic is an overestimate of evaporation, although other freshwater budget components may also play a role. The increase in ocean freshwater transport into the Atlantic during the simulation, primarily coming from the overturning circulation component, which changes from divergent to convergent, acts to balance this freshwater budget deficit. The stability of the thermohaline circulation in HadCM3 may be affected by these freshwater transport changes and this question is examined in the context of an existing conceptual model.  相似文献   

3.
 In this study we investigate the role of heat, freshwater and momentum fluxes in changing the oceanic climate and thermohaline circulation as a consequence of increasing atmospheric CO2 concentration. Two baseline integrations with a fully coupled ocean atmosphere general circulation model with either fixed or increasing atmospheric CO2 concentrations have been performed. In a set of sensitivity experiments either freshwater (precipitation, evaporation and runoff from the continents) and/or momentum fluxes were no longer simulated, but prescribed according to one of the fully coupled baseline experiments. This approach gives a direct estimate of the contribution from the individual flux components. The direct effect of surface warming and the associated feedbacks in ocean circulation are the dominant processes in weakening the Atlantic thermohaline circulation in our model. The relative contribution of momentum and freshwater fluxes to the total response turned out to be less than 25%, each. Changes in atmospheric water vapour transport lead to enhanced freshwater input into middle and high latitudes, which weakens the overturning. A stronger export of freshwater from the Atlantic drainage basin to the Indian and Pacific ocean, on the other hand, intensifies the Atlantic overturning circulation. In total the modified freshwater fluxes slightly weaken the Atlantic thermohaline circulation. The contribution of the modified momentum fluxes has a similar magnitude, but enhances the formation of North Atlantic deep water. Salinity anomalies in the Atlantic as a consequence of greenhouse warming stem in almost equal parts from changes in net freshwater fluxes and from changes in ocean circulation caused by the surface warming due to atmospheric heat fluxes. Important effects of the momentum fluxes are a poleward shift of the front between Northern Hemisphere subtropical and subpolar gyres and a southward shift in the position of the Antarctic circumpolar current, with a clear signal in sea level. Received: 3 May 1999 / Accepted: 11 December 1999  相似文献   

4.
This paper investigates the effects of river discharge on simulated climatology from 1979 to 1988 using the Hadley Centre Global Environmental Model version 2. Two experiments are performed with and without the inclusion of Total Runoff Integrating Pathways. The results show that the inclusion of flow routing can lead to the decrease of salinity over the coastal region due to freshwater. This reduction results in a shallower mixed layer depth, which in turn leads to the weakening of trade winds and a decrease in vertical mixing in the ocean. The enhanced sensible and latent heat fluxes over warmed SST improve the simulated precipitation and thermodynamic circulation. As a result, the experiment with flow routing is capable of improving the large-scale climate feature with an increase in precipitation over the eastern tropical equatorial Pacific region.  相似文献   

5.
The role of atmospheric general circulation model (AGCM) horizontal resolution in representing the global energy budget and hydrological cycle is assessed, with the aim of improving the understanding of model uncertainties in simulating the hydrological cycle. We use two AGCMs from the UK Met Office Hadley Centre: HadGEM1-A at resolutions ranging from 270 to 60 km, and HadGEM3-A ranging from 135 to 25 km. The models exhibit a stable hydrological cycle, although too intense compared to reanalyses and observations. This over-intensity is explained by excess surface shortwave radiation, a common error in general circulation models (GCMs). This result is insensitive to resolution. However, as resolution is increased, precipitation decreases over the ocean and increases over the land. This is associated with an increase in atmospheric moisture transport from ocean to land, which changes the partitioning of moisture fluxes that contribute to precipitation over land from less local to more non-local moisture sources. The results start to converge at 60-km resolution, which underlines the excessive reliance of the mean hydrological cycle on physical parametrization (local unresolved processes) versus model dynamics (large-scale resolved processes) in coarser HadGEM1 and HadGEM3 GCMs. This finding may be valid for other GCMs, showing the necessity to analyze other chains of GCMs that may become available in the future with such a range of horizontal resolutions. Our finding supports the hypothesis that heterogeneity in model parametrization is one of the underlying causes of model disagreement in the Coupled Model Intercomparison Project (CMIP) exercises.  相似文献   

6.
The authors examine the effects of external forcing agents such as greenhouse gases (GHGs) and aerosols, as well as solar variability and ozone, on global land monsoon precipitation by using a coupled climate model HadGEM1, which was developed by the Met Office Hadley Centre for Climate Research. The results indicate that HadGEM1 performs well in simulating the observed decreasing trend of global land monsoon precipitation over the past 50 years. This trend mainly occurred in the Northern Hemisphere and is ...  相似文献   

7.
River discharge forms a major freshwater input into the Arctic Ocean, and as such it has the potential to influence the oceanic circulation. As the hydrology of Arctic river basins is dominated by cryospheric processes such as snow accumulation and snowmelt, it may also be highly sensitive to a change in climate. Estimating the water balance of these river basins is therefore important, but it is complicated by the sparseness of observations and the large uncertainties related to the measurement of snowfalls. This study aims at simulating the water balance of the Barents Sea drainage basin in Northern Europe under present and future climate conditions. We used a regional climate model to drive a large-scale hydrological model of the area. Using simulated precipitation derived from a climate model led to an overestimation of the annual discharge in most river basins, but not in all. Under the B2 scenario of climate change, the model simulated a 25% increase in freshwater runoff, which is proportionally larger than the projected precipitation increase. As the snow season is 30–50 day shorter, the spring discharge peak is shifted by about 2–3 weeks, but the hydrological regime of the rivers remains dominated by snowmelt.  相似文献   

8.
The dependence of the annual mean tropical precipitation on horizontal resolution is investigated in the atmospheric version of the Hadley Centre General Environment Model. Reducing the grid spacing from about 350 km to about 110 km improves the precipitation distribution in most of the tropics. In particular, characteristic dry biases over South and Southeast Asia including the Maritime Continent as well as wet biases over the western tropical oceans are reduced. The annual-mean precipitation bias is reduced by about one third over the Maritime Continent and the neighbouring ocean basins associated with it via the Walker circulation. Sensitivity experiments show that much of the improvement with resolution in the Maritime Continent region is due to the specification of better resolved surface boundary conditions (land fraction, soil and vegetation parameters) at the higher resolution. It is shown that in particular the formulation of the coastal tiling scheme may cause resolution sensitivity of the mean simulated climate. The improvement in the tropical mean precipitation in this region is not primarily associated with the better representation of orography at the higher resolution, nor with changes in the eddy transport of moisture. Sizeable sensitivity to changes in the surface fields may be one of the reasons for the large variation of the mean tropical precipitation distribution seen across climate models.  相似文献   

9.
Diagnostic methods are defined in order to compare two numerical simulations of ocean dynamics in a region of freshwater influence. The first one is a river plume simulation based on a high resolution numerical configuration of the POM coastal ocean model in which mixing parametrizations have been previously defined. The second one is a simulation based on the NEMO Global Ocean Model used for climate simulations in its half-a-degree configuration in which a river inflow is represented as precipitation on two coastal grid cells. Both simulations are forced with the same freshwater inflows and wind stresses. The divergence of volumetric fluxes above and below the halocline are compared. Results show that when an upwelling wind blows, the two models display similar behavior although the impact of lack of precision can be observed in the NEMO configuration. When a downwelling wind blows, the NEMO Global Ocean configuration can not reproduce the coastally trapped baroclinic dynamics because its grid resolution is too coarse. To find a parametrization to help represent these dynamics in ocean general circulation models, a method based on energy conservation is investigated. This method shows that it is possible to link the energy fluxes provided by river inflows to the divergence of energy fluxes integrated over the grid cells of ocean general circulation models. A parametrization of the dynamics created by freshwater inflows is deduced from this method. This enabled creation of a box model that proved to have the same behavior as the fluxes previously computed from the high resolution configuration.  相似文献   

10.
Use of ocean data assimilation in meteorological applications is expected to reveal the influence of cloud-covered oceanic mesoscale processes on wintertime weather and climate in coastal areas. In particular, eddy-resolving Ocean Circulation Model (OCM) data assimilation that reproduces seasonally persistent oceanic mesoscale eddies is useful when simulating coastal precipitation. In the present study, the OCM-assimilation sea surface temperature (SST) is applied to a long-term atmospheric simulation over the Japan/East Sea area in the 2004/2005 winter season (December–February, DJF), to investigate seasonal and daily influences of oceanic mesoscale eddies on precipitation. The simulated winter precipitation is improved by the OCM assimilation via the DJF evaporation around a cold tongue. The strong intrusion of the southeast-directed cold tongue reduces the degree of overestimation by coastal precipitation simulations in December and January. In contrast, the ocean assimilation barely improves the simulation results in February because of weak intrusion of the cold tongue. In December and January, an abruptly large anomaly of northwesterly surface wind (> 1 m s?1) resulting from the OCM assimilation often influences 3-hour precipitation in the downstream area of the cold tongue. In contrast, the slowly-varying anomaly of evaporation does not necessarily lead to daily precipitation anomalies, although the DJF evaporation anomaly is important in the DJF precipitation.  相似文献   

11.
We have performed experiments using an ocean model to study the sensitivity of tropical Pacific Ocean to variations in precipitation induced freshwater fluxes. Variations in these fluxes arise from natural causes on all time scales. In addition, estimates of these fluxes are uncertain because of differences among measurement techniques. The model used is a quasi-isopycnal model, covering the Pacific from 40?°S to 40?°N. The surface forcing is constructed from observed wind stress, evaporation, precipitation, and sea surface temperature (SST) fields. The heat flux is produced with an iterative technique so as to maintain the model close to the observed climatology, but with only a weak damping to that climatology. Climatological estimates of evaporation are combined with various estimates of precipitation to determine the net surface freshwater flux. Results indicate that increased freshwater input decreases salinity as expected, but increases temperatures in the upper ocean. Using the freshwater flux estimated from the Microwave Sounding Unit leads to a warming of up to 0.6?°C in the western Pacific over?a case with zero net freshwater flux. SST is sensitive to the discrepancies among different precipitation observations, with root-mean-square differences in SST on the order of 0.2–0.3?°C. The change in SST is more pronounced in the eastern Pacific, with difference of over 1?°C found among the various precipitation products. Interannual variation in precipitation during El Niño events leads to increased warming. During the winter of 1982–83, freshwater flux accounts for about 0.4?°C (approximately 10–15% of the maximum warming) of the surface warming in the central-eastern Pacific. Thus, the error of SST caused by the discrepancies in precipitation products is more than half of the SST anomaly produced by the interannual variability of observed precipitation. Further experiments, in which freshwater flux anomalies are imposed in the western, central, and eastern Pacific, show that the influence of net freshwater flux is also spatially dependent. The imposition of freshwater flux in the far western Pacific leads to a trapping of salinity anomalies to the surface layers near the equator. An identical flux imposed in the central Pacific produces deeper and off-equatorial salinity anomalies. The contrast between these two simulations is consistent with other simulations of the western Pacific barrier layer formation.  相似文献   

12.
A long-term simulation for the period 1990–2010 is conducted with the latest version of the International Centre for Theoretical Physics' Regional Climate Model(RegCM4), driven by ERA-Interim boundary conditions at a grid spacing of 25 km. The Community Land Model(CLM) is used to describe land surface processes, with updates in the surface parameters,including the land cover and surface emissivity. The simulation is compared against observations to evaluate the model performance in reproducing the present day climatology and interannual variability over the 10 main river basins in China,with focus on surface air temperature and precipitation. Temperature and precipitation from the ERA-Interim reanalysis are also considered in the model assessment. Results show that the model reproduces the present day climatology over China and its main river basins, with better performances in June–July–August compared to December–January–February(DJF).In DJF, we find a warm bias at high latitudes, underestimated precipitation in the south, and overestimated precipitation in the north. The model in general captures the observed interannual variability, with greater skill for temperature. We also find an underestimation of heavy precipitation events in eastern China, and an underestimation of consecutive dry days in northern China and the Tibetan Plateau. Similar biases for both mean climatology and extremes are found in the ERA-Interim reanalysis, indicating the difficulties for climate models in simulating extreme monsoon climate events over East Asia.  相似文献   

13.
利用Hadley气候预测与研究中心的区域气候模式系统PRECIS单向嵌套该中心全球海-气耦合气候模式HadCM3高分辨率的大气部分HadAM3H,分析了SRES A2情景下2071-2100年相对于气候基准时段（1961-1990年）中国区域的气候变化,包括气温和降水的年际、季节和日时间尺度的变化以及极端气候事件的变化趋势。模拟结果表明：气温呈明显增加趋势,其中新疆和东北地区增温明显。而降水表现了更大的年际变化和季节变化,冬季南方降水减少,但沿黄河流域的降水明显增加,夏季与冬季相比呈现出相反的趋势。此外,连续高温日数呈现增加趋势,而连续霜冻日数呈现减少趋势。连续湿日数也表现出一定的增加趋势。  相似文献   

14.
Arctic climate change in 21st century CMIP5 simulations with EC-Earth   总被引：4，自引：2，他引：2  
The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.  相似文献   

15.
Four high resolution atmospheric general circulation models (GCMs) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre sea surface temperature and sea-ice extent. The response over Europe, calculated as the difference between the 2071–2100 and the 1961–1990 means is compared with the same diagnostic obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly, except that GCMs exhibit a larger spread. However, during summer, the spread of the RCMs—in particular in terms of precipitation—is larger than that of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution processes. The temperature response is larger than the systematic error. The situation is different for precipitation. The model bias is twice as large as the climate response. The confidence in PRUDENCE results comes from the fact that the models have a similar response to the IPCC-SRES A2 forcing, whereas their systematic errors are more spread. In addition, GCM precipitation response is slightly but significantly different from that of the RCMs.  相似文献   

16.
青海地表水资源的变化及影响因子   总被引：8，自引：0，他引：8  
通过分析近３８年青海省主要河流径流量及其流域降水、气温的变化趋势,着重研究了干旱气候对青海地表水资源的影响。结果表明,内陆河多为高山冰雪融水和雨水混合补给型河流,外流河多为以雨水补给为主的河流;青海地表水资源呈减少趋势,其减少趋势进入９０年代后尤为明显;气温和降水是影响青海地表水资源的主要气候因子,其中气温升高加剧了流域蒸发量的增大和干旱影响,减少了地表径流量;而９０年代以来降水量的减少特别是汛期降水量的减少直接影响到径流量的减少。  相似文献   

17.
In HadGEM2-A, AMIP experiments forced with observed sea surface temperatures respond to uniform and patterned +4 K SST perturbations with strong positive cloud feedbacks in the subtropical stratocumulus/trade cumulus transition regions. Over the subtropical Northeast Pacific at 137°W/26°N, the boundary layer cloud fraction reduces considerably in the AMIP +4 K patterned SST experiment. The near-surface wind speed and the air-sea temperature difference reduces, while the near-surface relative humidity increases. These changes limit the local increase in surface evaporation to just 3 W/m2 or 0.6 %/K. Previous studies have suggested that increases in surface evaporation may be required to maintain maritime boundary layer cloud in a warmer climate. This suggests that the supply of water vapour from surface evaporation may not be increasing enough to maintain the low level cloud fraction in the warmer climate in HadGEM2-A. Sensitivity tests which force the surface evaporation to increase substantially in the +4 K patterned SST experiment result in smaller changes in boundary layer cloud and a weaker cloud feedback in HadGEM2-A, supporting this idea. Although global mean surface evaporation in climate models increases robustly with global temperature (and the resulting increase in atmospheric radiative cooling), local values may increase much less, having a significant impact on cloud feedback. These results suggest a coupling between cloud feedback and the hydrological cycle via changes in the patterns of surface evaporation. A better understanding of both the factors controlling local changes in surface evaporation and the sensitivity of clouds to such changes may be required to understand the reasons for inter-model differences in subtropical cloud feedback.  相似文献   

18.

This study assesses the hydroclimatic response to global warming over East Asia from multi-model ensemble regional projections. Four different regional climate models (RCMs), namely, WRF, HadGEM3-RA, RegCM4, and GRIMs, are used for dynamical downscaling of the Hadley Centre Global Environmental Model version 2–Atmosphere and Ocean (HadGEM2-AO) global projections forced by the representative concentration pathway (RCP4.5 and RCP8.5) scenarios. Annual mean precipitation, hydroclimatic intensity index (HY-INT), and wet and dry extreme indices are analyzed to identify the robust behavior of hydroclimatic change in response to enhanced emission scenarios using high-resolution (12.5 km) and long-term (1981–2100) daily precipitation. Ensemble projections exhibit increased hydroclimatic intensity across the entire domain and under both the RCP scenarios. However, a geographical pattern with predominantly intensified HY-INT does not fully emerge in the mean precipitation change because HY-INT is tied to the changes in the precipitation characteristics rather than to those in the precipitation amount. All projections show an enhancement of high intensity precipitation and a reduction of weak intensity precipitation, which lead to a possible shift in hydroclimatic regime prone to an increase of both wet and dry extremes. In general, projections forced by the RCP8.5 scenario tend to produce a much stronger response than do those by the RCP4.5 scenario. However, the temperature increase under the RCP4.5 scenario is sufficiently large to induce significant changes in hydroclimatic intensity, despite the relatively uncertain change in mean precipitation. Likewise, the forced responses of HY-INT and the two extreme indices are more robust than that of mean precipitation, in terms of the statistical significance and model agreement.

  相似文献   

19.
We present climate responses of Representative Concentration Pathways (RCPs) using the coupled climate model HadGEM2-AO for the Coupled Model Intercomparison Project phase 5 (CMIP5). The RCPs are selected as standard scenarios for the IPCC Fifth Assessment Report and these scenarios include time paths for emissions and concentrations of greenhouse gas and aerosols and land-use/land cover. The global average warming and precipitation increases for the last 20 years of the 21st century relative to the period 1986-2005 are +1.1°C/+2.1% for RCP2.6, +2.4°C/+4.0% for RCP4.5, +2.5°C/+3.3% for RCP6.0 and +4.1°C/+4.6% for RCP8.5, respectively. The climate response on RCP 2.6 scenario meets the UN Copenhagen Accord to limit global warming within two degrees at the end of 21st century, the mitigation effect is about 3°C between RCP2.6 and RCP8.5. The projected precipitation changes over the 21st century are expected to increase in tropical regions and at high latitudes, and decrease in subtropical regions associated with projected poleward expansions of the Hadley cell. Total soil moisture change is projected to decrease in northern hemisphere high latitudes and increase in central Africa and Asia whereas near-surface soil moisture tends to decrease in most areas according to the warming and evaporation increase. The trend and magnitude of future climate extremes are also projected to increase in proportion to radiative forcing of RCPs. For RCP 8.5, at the end of the summer season the Arctic is projected to be free of sea ice.  相似文献   

20.
We present a dynamical downscaling of the Arctic climatology using a high-resolution implementation of the Polar Weather Research and Forecasting, version 3.6 (WRF3.6) model, with a focus on Arctic cyclone activity. The study period is 1979–2004 and the driving fields are data from the Hadley Centre Global Environmental Model, version 2, with an Earth System component (HadGEM2-ES) simulations. We show that the results from the Polar WRF model provide significantly improved simulations of the frequency, intensity, and size of cyclones compared with the HadGEM2-ES simulations. Polar WRF reproduces the intensity of winter cyclones found in ERA-Interim, the global atmospheric reanalysis produced by the European Centre for Medium-range Weather Forecasts (ECMWF), and suggests that the average minimum central pressure of the cyclones is about 10?hPa lower than that derived from HadGEM2-ES simulations. Although both models underestimate the frequency of summer Arctic cyclones, Polar WRF simulations suggest there are 10.5% more cyclones per month than do HadGEM2-ES results. Overall, the Polar WRF model captures more intense and smaller cyclones than are obtained in HadGEM2-ES results, in better agreement with the ERA-Interim reanalysis data. Our results also show that the improved simulations of Arctic synoptic weather systems contribute to better simulations of atmospheric surface fields. The Polar WRF model is better able to simulate both the spatial patterns and magnitudes of the ERA-Interim reanalysis data than HadGEM2-ES is; in particular, the latter overestimates the absorbed solar radiation in the Arctic basin by as much as 30?W?m?2 and underestimates longwave radiation by about 10?W?m?2 in summer. Our results suggest that the improved simulations of longwave and solar radiation are partly associated with a better simulation of cloud liquid water content in the Polar WRF model, which is linked to improvements in the simulation of cyclone frequency and intensity and the resulting transient eddy transports of heat and water vapour.  相似文献   

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