On the numerical resolution in a thermodynamic sea-ice model

2002 ◽  
Vol 48 (161) ◽  
pp. 301-311 ◽  
Author(s):  
Bin Cheng
Keyword(s):  
Sea Ice ◽  
Spatial Resolution ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Warm Up ◽  
Surface Heat Fluxes ◽  
Numerical Resolution ◽  
Main Components ◽  
The Impact ◽  
Ice Model

AbstractThe numerical integration of the heat-conduction equation is one of the main components in a thermodynamic sea-ice model. The spatial resolution in the ice normally varies from a minimum of three layers up to a few tens of layers. The temporal resolution varies from a few minutes up to hours. In this paper the impact of numerical resolution on the prediction of a one-dimensional thermodynamic ice model is studied. Analytical solutions for idealized cases were derived and compared with the numerical results. For the full ice model, groups of simulations were made, applying average climatic weather-forcing data corresponding to the ice-freezing, ice-thermal equilibrium and ice warm-up seasons. Special attention was paid to the effect of model spatial resolution. Early in the freezing season, the influence of resolution on model predictions is not significant. When the shortwave radiation becomes large, its absorption within the ice or snow cover was found to modulate the effect of numerical resolution on predictions of ice temperature and surface heat fluxes (e.g. the model run with a coarse spatial resolution yielded large daily variations in surface temperature). Resolution also affects the in-ice temperature profile. For process studies, a two-layer scheme for the solar radiation penetrating into the ice is suitable for a fine-spatial-resolution ice model.

scholarly journals Arctic Intense Summer Storms and Their Impacts on Sea Ice—A Regional Climate Modeling Study

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 218 ◽  
Author(s):  
Alexander Semenov ◽  
Xiangdong Zhang ◽  
Annette Rinke ◽  
Wolfgang Dorn ◽  
Klaus Dethloff
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Chukchi Sea ◽  
Regional Climate ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Energy Budgets ◽  
Sea Ice Concentration ◽  
Storm Activity

Various temporal and spatial changes have manifested in Arctic storm activities, including the occurrence of the anomalously intense storms in the summers of 2012 and 2016, along with the amplified warming and rapidly decreased sea ice. To detect the variability of and changes in storm activity and understand its role in sea ice changes, we examined summer storm count and intensity year-by-year from ensemble hindcast simulations with an Arctic regional coupled climate model for the period of 1948–2008. The results indicated that the model realistically simulated the climatological spatial structure of the storm activity, characterized by the storm count and intensity. The simulated storm count captures the variability derived from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP–NCAR) reanalysis, though the simulated one is higher than that in the reanalysis. This could be attributed to the higher resolution of the model that may better represent smaller and shallower cyclones. The composite analysis shows that intense storms tend to form a low-pressure pattern with centers over the Kara Sea and Chukchi Sea, respectively, generating cyclonic circulation over the North Atlantic and North Pacific Arctic Ocean. The former drives intensification of the transpolar drift and Fram Strait sea ice export, and the latter suppresses thick ice transport from the Canada Basin to the Beaufort–Chukchi Seas, in spite of an increase in sea ice transport to the East Siberian Sea. Associated with these changes in sea ice transport, sea ice concentration and thickness show large decreases in the Barents–Kara Seas and the Chukchi–East-Siberian Seas, respectively. Energy budgets analysis suggests that more numerous intense storms substantially decrease the downward net sea ice heat fluxes, including net radiative fluxes, turbulent fluxes, and oceanic heat fluxes, compared with that when a lower number of intense storms occur. The decrease in the heat fluxes could be attributable to an increased cloudiness and the resultant reduction of downward shortwave radiation, as well as a destabilized boundary layer induced increase in upward turbulent fluxes.

scholarly journals The Impact of an Intense Cyclone on Short‐Term Sea Ice Loss in a Fully Coupled Atmosphere‐Ocean‐Ice Model

2020 ◽  
Vol 47 (4) ◽  
Author(s):  
Daniel P. Stern ◽  
James D. Doyle ◽  
Neil P. Barton ◽  
Peter M. Finocchio ◽  
William A. Komaromi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Short Term ◽  
The Impact ◽  
Fully Coupled ◽  
Ice Model

The Impact of Outer-Core Surface Heat Fluxes on the Convective Activities and Rapid Intensification of Tropical Cyclones

2020 ◽  
Vol 77 (11) ◽  
pp. 3907-3927
Author(s):  
Chin-Hsuan Peng ◽  
Chun-Chieh Wu
Keyword(s):  
Inner Core ◽  
Surface Wind ◽  
Outer Core ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Core Surface ◽  
Surface Heat Fluxes ◽  
The Impact

AbstractThe rapid intensification (RI) of Typhoon Soudelor (2015) is simulated using a full-physics model. To investigate how the outer-core surface heat fluxes affect tropical cyclone (TC) structure and RI processes, a series of numerical experiments are performed by suppressing surface heat fluxes between various radii. It is found that a TC would become quite weaker when the surface heat fluxes are suppressed outside the radius of 60 or 90 km [the radius of maximum surface wind in the control experiment (CTRL) at the onset of RI is roughly 60 km]. However, interestingly, the TC would experience stronger RI when the surface heat fluxes are suppressed outside the radius of 150 km. For those sensitivity experiments with capped surface heat fluxes, the members with greater intensification rate show stronger inner-core mid- to upper-level updrafts and higher heating efficiency prior to the RI periods. Although the outer-core surface heat fluxes in these members are suppressed, the inner-core winds become stronger, extracting more ocean energy from the inner core. Greater outer-core low-level stability in these members results in aggregation of deep convection and subsequent generation and concentration of potential vorticity inside the inner core, thus confining the strongest winds therein. The abovementioned findings are also supported by partial-correlation analyses, which reveal the positive correlation between the inner-core convection and subsequent 6-h intensity change, and the competition between the inner-core and outer-core convections (i.e., eyewall and outer rainbands).

scholarly journals Impacts of Atmospheric Reanalysis Uncertainty on Atlantic Overturning Estimates at 25°N

2018 ◽  
Vol 31 (21) ◽  
pp. 8719-8744 ◽  
Author(s):  
Helen R. Pillar ◽  
Helen L. Johnson ◽  
David P. Marshall ◽  
Patrick Heimbach ◽  
So Takao
Keyword(s):  
Climate Model ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Labrador Sea ◽  
Surface Heat Fluxes ◽  
Ensemble Mean ◽  
Meridional Overturning ◽  
The Impact ◽  
Average Uncertainty

Atmospheric reanalyses are commonly used to force numerical ocean models, but despite large discrepancies reported between different products, the impact of reanalysis uncertainty on the simulated ocean state is rarely assessed. In this study, the impact of uncertainty in surface fluxes of buoyancy and momentum on the modeled Atlantic meridional overturning at 25°N is quantified for the period January 1994–December 2011. By using an ocean-only climate model and its adjoint, the space and time origins of overturning uncertainty resulting from air–sea flux uncertainty are fully explored. Uncertainty in overturning induced by prior air–sea flux uncertainty can exceed 4 Sv (where 1 Sv ≡ 106 m3 s−1) within 15 yr, at times exceeding the amplitude of the ensemble-mean overturning anomaly. A key result is that, on average, uncertainty in the overturning at 25°N is dominated by uncertainty in the zonal wind at lags of up to 6.5 yr and by uncertainty in surface heat fluxes thereafter, with winter heat flux uncertainty over the Labrador Sea appearing to play a critically important role.

scholarly journals Snow dune growth increases polar heat fluxes

2021 ◽  
Author(s):  
Kelly Kochanski ◽  
Gregory Tucker ◽  
Robert Anderson
Keyword(s):  
Sea Ice ◽  
Snow Depth ◽  
Radiative Heat ◽  
Heat Fluxes ◽  
Ice Melting ◽  
Surface Energy Fluxes ◽  
Starting Point ◽  
Climate Simulations ◽  
Quantitative Results ◽  
The Impact

Abstract. Falling snow often accumulates in dunes. These bedforms are found on up to 14 % of the surface of Earth, and appear occasionally on other planets. They have been associated with increased heat fluxes and rapid sea ice melting (Petrich et al., 2012; Popović et al., 2018). Their formation, however, is poorly understood (Filhol and Sturm, 2015; Kochanski et al., 2019a; Sharma et al., 2019). Here, we use field observations to show that dune growth is controlled by snowfall rate and wind speed. We then use numerical experiments to generate simulated dune topographies under varied wind and snowfall conditions, and use those to quantify conductive and radiative heat fluxes through snow. Our results show that dune growth leads to decreased snow cover, more variable snow depth, and significant increases in surface energy fluxes. We provide quantitative results that will allow modelers to account for the impact of snow bedforms in snow, sea ice, and climate simulations. In addition, this work offers a starting point for process-based studies of one of the most widespread bedforms on Earth.

scholarly journals The impact of atmospheric mineral aerosol deposition on the albedo of snow and sea ice: are snow and sea ice optical properties more important than mineral aerosol optical properties?

2015 ◽  
Vol 15 (16) ◽  
pp. 23131-23172
Author(s):  
M. L. Lamare ◽  
J. Lee-Taylor ◽  
M. D. King
Keyword(s):  
Optical Properties ◽  
Sea Ice ◽  
Atmospheric Aerosols ◽  
Aerosol Deposition ◽  
Shortwave Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Polar Snow ◽  
The Impact

Abstract. Knowledge of the albedo of polar regions is crucial for understanding a range of climatic processes that have an impact on a global scale. Light absorbing impurities in atmospheric aerosols deposited on snow and sea ice by aeolian transport absorb solar radiation, reducing albedo. Here, the effects of five mineral aerosol deposits reducing the albedo of polar snow and sea ice are considered. Calculations employing a coupled atmospheric and snow/sea ice radiative-transfer model (TUV-snow) show that the effects of mineral aerosol deposits is strongly dependent on the snow or sea ice type rather than the differences between the aerosol optical characteristics. The change in albedo between five different mineral aerosol deposits with refractive indices varying by a factor of 2 reaches a maximum of 0.0788, whereas the difference between cold polar snow and melting sea ice is 0.8893 for the same mineral loading. Surprisingly, the thickness of a surface layer of snow or sea ice loaded with the same mass-ratio of mineral dust has little effect on albedo. On the contrary, multiple layers of mineral aerosols deposited during episodic events evenly distributed play a similar role in the surface albedo of snow as a loading distributed throughout, even when the layers are further apart. The impact of mineral aerosol deposits is much larger on melting sea ice than on other types of snow and sea ice. Therefore, the higher input of shortwave radiation during the summer melt cycle associated with melting sea ice accelerates the melt process.

scholarly journals Modeling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean

2014 ◽  
Vol 11 (12) ◽  
pp. 16953-16992
Author(s):  
V. Le Fouest ◽  
M. Manizza ◽  
B. Tremblay ◽  
M. Babin
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Temporal Trend ◽  
The Arctic ◽  
Biogeochemical Model ◽  
The Impact ◽  
Ice Model ◽  
Annual Flux

Abstract. The planktonic and biogeochemical dynamics of the Arctic shelves exhibit a strong variability in response to Arctic warming. In this study, in order to elucidate on the processes regulating the production of phytoplankton (PP) and bacterioplankton (BP) and their interactions, we employ a biogeochemical model coupled to a pan-Arctic ocean-sea ice model (MITgcm) to explicitly simulate and quantify the contribution of usable dissolved organic nitrogen (DON) drained by the major circum-Arctic rivers on PP and BP in a scenario of melting sea ice (1998–2011). Model simulations suggest that on average between 1998 and 2011, the removal of usable RDON by bacterioplankton is responsible of a ~26% increase of the annual BP for the whole Arctic Ocean. With respect to total PP, the model simulates an increase of ~8% on an annual basis and of ~18% in summer. Recycled ammonium is responsible for the PP increase. The recycling of RDON by bacterioplankton promotes higher BP and PP but there is no significant temporal trend in the BP : PP ratio within the ice-free shelves over the 1998–2011 period. This suggests no significant evolution in the balance between autotrophy and heterotrophy in the last decade with a constant annual flux of RDON into the coastal ocean although changes in RDON supply and further reduction in sea ice cover could potentially alter this delicate balance.

scholarly journals Daytime low-level clouds in West Africa – occurrence, associated drivers, and shortwave radiation attenuation

2020 ◽  
Vol 11 (4) ◽  
pp. 1133-1152
Author(s):  
Derrick K. Danso ◽  
Sandrine Anquetin ◽  
Arona Diedhiou ◽  
Kouakou Kouadio ◽  
Arsène T. Kobea
Keyword(s):  
Solar Radiation ◽  
West Africa ◽  
Moisture Flux ◽  
Heat Fluxes ◽  
Occurrence Frequency ◽  
Shortwave Radiation ◽  
High Attenuation ◽  
Low Level ◽  
Class 1 ◽  
The Impact

Abstract. This study focuses on daytime low-level clouds (LLCs) that occur within the first 2 km of the atmosphere over West Africa (WA). These daytime LLCs play a major role in the earth's radiative balance, yet their understanding is still relatively low in WA. We use the state-of-the-art ERA5 dataset to understand their occurrence and associated drivers as well as their impact on the incoming surface solar radiation in the two contrasting Guinean and Sahelian regions of WA. The diurnal cycle of the daytime occurrence of three LLC classes namely No LCC, LLC Class-1 (LLCs with lower fraction), and LLC Class-2 (LLCs with higher fraction) is first studied. The monthly evolutions of hourly and long-lasting LLC (for at least 6 consecutive hours) events are then analyzed as well as the synoptic-scale moisture flux associated with the long-lasting LLC events. Finally, the impact of LLC on the surface heat fluxes and the incoming solar irradiance is investigated. During the summer months in the Guinean region, LLC Class-1 occurrence is low, while LLC Class-2 is frequent (occurrence frequency around 75 % in August). In the Sahel, LLC Class-1 is dominant in the summer months (occurrence frequency more than 80 % from June to October); however the peak occurrence frequency of Class-2 is also in the summer. In both regions, events with No LLC do not present any specific correlation with the time of the day. However, a diurnal evolution that appears to be strongly different from one region to the other is noted for the occurrence of LLC Class-2. LLC occurrence in both regions is associated with high moisture flux driven by strong southwesterly winds from the Gulf of Guinea and significant background moisture levels. LLC Class-2 in particular leads to a significant reduction in the upward transfer of energy and a net downward energy transfer caused by the release of large amounts of energy in the atmosphere during the cloud formation. In July, August, and September (JAS), most of the LLC Class-2 events may likely be the low-level stratiform clouds that occur frequently over the Guinean region, while they may be deep convective clouds in the Sahel. Additionally, LLC Class-2 causes high attenuation of the incoming solar radiation, especially during JAS, where about 49 % and 44 % of the downwelling surface shortwave radiation is lost on average in Guinea and the Sahel, respectively.

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