scholarly journals Sensitivity of CAM5-Simulated Arctic Clouds and Radiation to Ice Nucleation Parameterization

2013 ◽  
Vol 26 (16) ◽  
pp. 5981-5999 ◽  
Author(s):  
Shaocheng Xie ◽  
Xiaohong Liu ◽  
Chuanfeng Zhao ◽  
Yuying Zhang
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Arctic Region ◽  
Atmospheric Model ◽  
Ice Nucleation ◽  
The Arctic ◽  
Liquid Water Path ◽  
Arctic Clouds ◽  
Water Path ◽  
Low Level

Abstract Sensitivity of Arctic clouds and radiation in the Community Atmospheric Model, version 5, to the ice nucleation process is examined by testing a new physically based ice nucleation scheme that links the variation of ice nuclei (IN) number concentration to aerosol properties. The default scheme parameterizes the IN concentration simply as a function of ice supersaturation. The new scheme leads to a significant reduction in simulated IN concentration at all latitudes while changes in cloud amounts and properties are mainly seen at high- and midlatitude storm tracks. In the Arctic, there is a considerable increase in midlevel clouds and a decrease in low-level clouds, which result from the complex interaction among the cloud macrophysics, microphysics, and large-scale environment. The smaller IN concentrations result in an increase in liquid water path and a decrease in ice water path caused by the slowdown of the Bergeron–Findeisen process in mixed-phase clouds. Overall, there is an increase in the optical depth of Arctic clouds, which leads to a stronger cloud radiative forcing (net cooling) at the top of the atmosphere. The comparison with satellite data shows that the new scheme slightly improves low-level cloud simulations over most of the Arctic but produces too many midlevel clouds. Considerable improvements are seen in the simulated low-level clouds and their properties when compared with Arctic ground-based measurements. Issues with the observations and the model–observation comparison in the Arctic region are discussed.

scholarly journals Low-level mixed-phase clouds in a complex Arctic environment

2020 ◽  
Vol 20 (6) ◽  
pp. 3459-3481 ◽  
Author(s):  
Rosa Gierens ◽  
Stefan Kneifel ◽  
Matthew D. Shupe ◽  
Kerstin Ebell ◽  
Marion Maturilli ◽  
...  
Keyword(s):  
Large Scale ◽  
Local Wind ◽  
Liquid Water Path ◽  
Water Path ◽  
Local Boundary ◽  
Low Level ◽  
Ice Water Path ◽  
Mixed Phase Clouds ◽  
Ice Water ◽  
Surface Coupling

Abstract. Low-level mixed-phase clouds (MPCs) are common in the Arctic. Both local and large-scale phenomena influence the properties and lifetime of MPCs. Arctic fjords are characterized by complex terrain and large variations in surface properties. Yet, not many studies have investigated the impact of local boundary layer dynamics and their relative importance on MPCs in the fjord environment. In this work, we used a combination of ground-based remote sensing instruments, surface meteorological observations, radiosoundings, and reanalysis data to study persistent low-level MPCs at Ny-Ålesund, Svalbard, for a 2.5-year period. Methods to identify the cloud regime, surface coupling, and regional and local wind patterns were developed. We found that persistent low-level MPCs were most common with westerly winds, and the westerly clouds had a higher mean liquid (42 g m−2) and ice water path (16 g m−2) compared to those with easterly winds. The increased height and rarity of persistent MPCs with easterly free-tropospheric winds suggest the island and its orography have an influence on the studied clouds. Seasonal variation in the liquid water path was found to be minimal, although the occurrence of persistent MPCs, their height, and their ice water path all showed notable seasonal dependency. Most of the studied MPCs were decoupled from the surface (63 %–82 % of the time). The coupled clouds had 41 % higher liquid water path than the fully decoupled ones. Local winds in the fjord were related to the frequency of surface coupling, and we propose that katabatic winds from the glaciers in the vicinity of the station may cause clouds to decouple. We concluded that while the regional to large-scale wind direction was important for the persistent MPC occurrence and properties, the local-scale phenomena (local wind patterns in the fjord and surface coupling) also had an influence. Moreover, this suggests that local boundary layer processes should be described in models in order to present low-level MPC properties accurately.

scholarly journals The role of droplet sedimentation in the evolution of low-level clouds over southern West Africa

2018 ◽  
Vol 18 (19) ◽  
pp. 14253-14269 ◽  
Author(s):  
Christopher Dearden ◽  
Adrian Hill ◽  
Hugh Coe ◽  
Tom Choularton
Keyword(s):  
West Africa ◽  
Liquid Water ◽  
Large Scale ◽  
Monsoon Season ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Droplets ◽  
Water Path ◽  
Low Level

Abstract. Large-eddy simulations are performed to investigate the influence of cloud microphysics on the evolution of low-level clouds that form over southern West Africa during the monsoon season. We find that, even in clouds that are not precipitating, the size of cloud droplets has a non-negligible effect on liquid water path. This is explained through the effects of droplet sedimentation, which acts to remove liquid water from the entrainment zone close to cloud top, increasing the liquid water path. Sedimentation also produces a more heterogeneous cloud structure and lowers cloud base height. Our results imply that an appropriate parameterization of the effects of sedimentation is required to improve the representation of the diurnal cycle of the atmospheric boundary layer over southern West Africa in large-scale models.

scholarly journals Implications of Limited Liquid Water Path on Static Mixing within Arctic Low-Level Clouds

2014 ◽  
Vol 53 (12) ◽  
pp. 2775-2789 ◽  
Author(s):  
Joseph Sedlar
Keyword(s):  
Mixed Layer ◽  
Liquid Water ◽  
Heat Budget ◽  
Single Layer ◽  
Specific Humidity ◽  
The Arctic ◽  
Liquid Water Path ◽  
Stable Layer ◽  
Water Path ◽  
Low Level

AbstractObservations of cloud properties and thermodynamics from two Arctic locations, Barrow, Alaska, and Surface Heat Budget of the Arctic (SHEBA), are examined. A comparison of in-cloud thermodynamic mixing characteristics for low-level, single-layer clouds from nearly a decade of data at Barrow and one full annual cycle over the sea ice at SHEBA is performed. These cloud types occur relatively frequently, evident in 27%–30% of all cloudy cases. To understand the role of liquid water path (LWP), or lack thereof, on static in-cloud mixing, cloud layers are separated into optically thin and optically thick LWP subclasses. Clouds with larger LWPs tend to have a deeper in-cloud mixed layer relative to optically thinner clouds. However, both cloud LWP subclasses are frequently characterized by an in-cloud stable layer above the mixed layer top. The depth of the stable layer generally correlates with an increased temperature gradient across the layer. This layer often contains a specific humidity inversion, but it is more frequently present when cloud LWP is optically thinner (LWP < 50 g m−2). It is suggested that horizontal thermodynamic advection plays a key role modifying the vertical extent of in-cloud mixing and likewise the depth of in-cloud stable layers. Furthermore, longwave atmospheric opacity above the cloud top is generally enhanced during cases with optically thinner clouds. Thermodynamic advection, cloud condensate distribution within the stable layer, and enhanced atmospheric radiation above the cloud are found to introduce a thermodynamic–radiative feedback that potentially modifies the extent of LWP and subsequent in-cloud mixing.

scholarly journals Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

2016 ◽  
Vol 16 (7) ◽  
pp. 4661-4674 ◽  
Author(s):  
Quentin Coopman ◽  
Timothy J. Garrett ◽  
Jérôme Riedi ◽  
Sabine Eckhardt ◽  
Andreas Stohl
Keyword(s):  
Long Range ◽  
Liquid Water ◽  
Specific Humidity ◽  
The Arctic ◽  
Liquid Water Path ◽  
Arctic Clouds ◽  
Low Level ◽  
Microphysical Properties ◽  
Lower Tropospheric Stability ◽  
Pollution Concentrations

Abstract. The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol–cloud interaction (ACInet) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACInet is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACInet averages 0.12 ± 0.02 for cloud-droplet effective radius and 0.16 ± 0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds.

Ice microphysics of low-level ice clouds in the Arctic: Satellite analysis

2021 ◽  
Author(s):  
Iris Papakonstantinou-Presvelou ◽  
Johannes Quaas
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Arctic Region ◽  
Open Ocean ◽  
The Arctic ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Low Level ◽  
Level Ice ◽  
Satellite Analysis

&lt;p&gt;This study investigates low-level ice clouds in the Arctic and their potential relation to the surface aerosols. These aerosols or ice nucleating particles (INPs), are necessary for the heterogeneous nucleation of ice in temperatures above -38&amp;#176;C. Several studies in the past have investigated the sources of INPs and their nucleating behavior with response to the temperature. According to these studies, it has been suggested that a marine source of INPs coming from sea spray is able to nucleate ice in temperatures close to -5&lt;sup&gt;o&lt;/sup&gt;C. What we do here is a large-scale comparison of boundary-layer ice clouds over open ocean and sea ice, over the whole Arctic region for the time period of 2006-2016. We use for this purpose a satellite-retrieved quantity, the ice crystal number concentration (N&lt;sub&gt;i&lt;/sub&gt;), which we investigate in relation to the temperature. We study clouds with regard to the region and season they form and we examine their coupling to the surface. Our findings show - contrary to previous expectation - enhanced ice crystal numbers over sea ice compared to open ocean, in temperatures above -10&lt;sup&gt;o&lt;/sup&gt;C. In lower temperatures this difference still persists for the lower Arctic latitudes (&lt;70&lt;sup&gt;o&lt;/sup&gt;N), especially for clouds that are coupled to the surface.&lt;/p&gt;

Analyzing the Arctic Feedback Mechanism between Sea Ice and Low-Level Clouds Using 34 Years of Satellite Observations

2020 ◽  
Vol 33 (17) ◽  
pp. 7479-7501
Author(s):  
Daniel Philipp ◽  
Martin Stengel ◽  
Bodo Ahrens
Keyword(s):  
Sea Ice ◽  
Radiative Forcing ◽  
Large Scale ◽  
The Arctic ◽  
Turbulent Heat ◽  
Arctic Amplification ◽  
Surface Warming ◽  
Low Level ◽  
Gc Analysis ◽  
Csi Feedback

AbstractSatellite-based cloud, radiation flux, and sea ice records covering 34 years are used 1) to investigate autumn cloud cover trends over the Arctic, 2) to assess its relation with declining sea ice using Granger causality (GC) analysis, and 3) to discuss the contribution of the cloud–sea ice (CSI) feedback to Arctic amplification. This paper provides strong evidence for a positive CSI feedback with the capability to contribute to autumnal Arctic amplification. Positive low-level cloud fractional cover (CFClow) trends over the Arctic ice pack are found in October and November (ON) with magnitudes of up to about +9.6% per decade locally. Statistically significant anticorrelations between sea ice concentration (SIC) and CFClow are observed in ON over melting zones, suggesting an association. The GC analysis indicated a causal two-way interaction between SIC and CFClow. Interpreting the resulting F statistic and its spatial distribution as a relation strength proxy, the influence of SIC on CFClow is likely stronger than the reverse. ERA-Interim reanalysis data suggest that ON CFClow is impacted by sea ice melt through surface–atmosphere coupling via turbulent heat and moisture fluxes. Due to weak solar insolation in ON, net cloud radiative forcing (CRF) exerts a warming effect on the Arctic surface. Increasing CFClow induces a large-scale surface warming trend reaching magnitudes of up to about +8.3 W m−2 per decade locally. Sensitivities of total CRF to CFClow ranges between +0.22 and +0.66 W m−2 per percent CFClow. Increasing surface warming can cause a melt season lengthening and hinders formation of perennial ice.

scholarly journals The role of droplet sedimentation in the evolution of low level clouds over Southern West Africa

2018 ◽  
Author(s):  
Christopher Dearden ◽  
Adrian Hill ◽  
Hugh Coe ◽  
Tom Choularton
Keyword(s):  
West Africa ◽  
Liquid Water ◽  
Large Scale ◽  
Monsoon Season ◽  
Cloud Microphysics ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Droplets ◽  
Water Path ◽  
Low Level

Abstract. Large eddy simulations are performed to investigate the influence of cloud microphysics on the evolution of low level clouds that form over southern West Africa during the monsoon season. We find that, even in clouds that are not precipitating, the size of cloud droplets has a non-negligible effect on liquid water path. This is explained through the effects of droplet sedimentation, which acts to remove liquid water from the entrainment zone close to cloud top, increasing liquid water path. Sedimentation also produces a more heterogeneous cloud structure and lowers cloud base height. Our results imply that an appropriate parameterization of the effects of sedimentation is required to improve the representation of the diurnal cycle of the atmospheric boundary layer over southern West Africa in large-scale models.

scholarly journals A New Double-Moment Microphysics Parameterization for Application in Cloud and Climate Models. Part II: Single-Column Modeling of Arctic Clouds

2005 ◽  
Vol 62 (6) ◽  
pp. 1678-1693 ◽  
Author(s):  
H. Morrison ◽  
J. A. Curry ◽  
M. D. Shupe ◽  
P. Zuidema
Keyword(s):  
Climate Models ◽  
Heat Budget ◽  
Number Concentration ◽  
The Arctic ◽  
Liquid Water Path ◽  
Microphysics Scheme ◽  
Radiative Fluxes ◽  
Arctic Clouds ◽  
Single Column ◽  
Double Moment

Abstract The new double-moment microphysics scheme described in Part I of this paper is implemented into a single-column model to simulate clouds and radiation observed during the period 1 April–15 May 1998 of the Surface Heat Budget of the Arctic (SHEBA) and First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment–Arctic Clouds Experiment (FIRE–ACE) field projects. Mean predicted cloud boundaries and total cloud fraction compare reasonably well with observations. Cloud phase partitioning, which is crucial in determining the surface radiative fluxes, is fairly similar to ground-based retrievals. However, the fraction of time that liquid is present in the column is somewhat underpredicted, leading to small biases in the downwelling shortwave and longwave radiative fluxes at the surface. Results using the new scheme are compared to parallel simulations using other microphysics parameterizations of varying complexity. The predicted liquid water path and cloud phase is significantly improved using the new scheme relative to a single-moment parameterization predicting only the mixing ratio of the water species. Results indicate that a realistic treatment of cloud ice number concentration (prognosing rather than diagnosing) is needed to simulate arctic clouds. Sensitivity tests are also performed by varying the aerosol size, solubility, and number concentration to explore potential cloud–aerosol–radiation interactions in arctic stratus.

Problems of development of Arctic hydrocarbon resources under the current conditions.

2021 ◽  
pp. 70-81
Author(s):  
Anna Borisovna Nikolaeva ◽  
Keyword(s):  
Economic Development ◽  
Alternative Energy ◽  
New Technologies ◽  
Recovery Period ◽  
Arctic Region ◽  
The Arctic ◽  
Expert Assessment ◽  
Low Level ◽  
The World ◽  
The Arctic Region

The Arctic is the richest and at the same time the most difficult region to develop in the world. Exploration and exploitation of its deposits are inevitable for Russia and mankind as a whole. The Arctic region is characterized by extreme nature-climatic conditions, with a rather low level of economic development and remoteness from industrial centers, a low level or lack of any infrastructure as well as by instability of the ecological system to anthropogenic impact and a long recovery period. Since the potential of the resources currently being developed will be exhausted within several decades, and the world economies are not yet ready for a full transition to alternative energy resources, it is necessary to search for and develop new hydrocarbon reserves that determines the relevance of the study.The aim of the study is to identify the main problems arising when exploiting hydrocarbons in the Arctic region. The set of problems identified predetermines an integrated approach to their solutions. In this case, it is about reforming legislation, increasing funding, and attracting new participants in the international cooperation. Since the export of oil and gas is traditional for the Russian Federation, exploitation of hydrocarbons in the region is a prerequisite for the further economic development of the country. A state policy aimed at development and improvement of new technologies, reducing environmental risks, and deep scientific research of the Arctic, is needed. The method of expert assessment was used, which is applied for solving complex tasks with lack of information, and impossibility of mathematical formalization of the solution process. The basis for the application of this method is the possibility and ability of experts to assess the importance of the problem under study and development prospects for a certain research direction. The expert assessments were highlighted during the study and analysis of the literature.

Global mapping of seasonal variations in tides from tide gauge and satellite altimeter data

2021 ◽  
Author(s):  
Inger Bij de Vaate ◽  
Henrique Guarneri ◽  
Cornelis Slobbe ◽  
Martin Verlaan
Keyword(s):  
Seasonal Variation ◽  
Sea Level ◽  
Seasonal Variations ◽  
Large Scale ◽  
Arctic Region ◽  
The Arctic ◽  
Altimeter Data ◽  
Tide Gauges ◽  
Tidal Constituents ◽  
The Arctic Region

&lt;p&gt;The existence of seasonal variations in major tides has been recognized since decades. Where Corkan (1934) was the first to describe the seasonal perturbation of the M2 tide, many others have studied seasonal variations in the main tidal constituents since. However, most of these studies are based on sea level observations from tide gauges and are often restricted to coastal and shelf regions. Hence, observed seasonal variations are typically dominated by local processes and the large-scale patterns cannot be clearly distinguished. Moreover, most tide models still perceive tides as annually constant and seasonal variation in tides is ignored in the correction process of satellite altimetry. This results in reduced accuracy of obtained sea level anomalies. &lt;/p&gt;&lt;p&gt;To gain more insight in the large-scale seasonal variations in tides, we supplemented the clustered and sparsely distributed sea level observations from tide gauges by the wealth of data from satellite altimeters. Although altimeter-derived water levels are being widely used to obtain tidal constants, only few of these implementations consider seasonal variation in tides. For that reason, we have set out to explore the opportunities provided by altimeter data for deriving seasonal modulation of the main tidal constituents. Different methods were implemented and compared for the principal tidal constituents and a range of geographical domains, using data from a selection of satellite altimeters. Specific attention was paid to the Arctic region where seasonal variation in tides was expected to be significant as a result of the seasonal sea ice cycle, yet data availability is particularly limited. Our study demonstrates the potential of satellite altimetry for the quantification of seasonal modulation of tides and suggests the seasonal modulation to be considerable. Already for M2 we observed changes in tidal amplitude of the order of decimeters for the Arctic region, and centimeters for lower latitude regions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;div&gt;Corkan, R. H. (1934). An annual perturbation in the range of tide. &lt;em&gt;Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character&lt;/em&gt;, &lt;em&gt;144&lt;/em&gt;(853), 537-559.&lt;/div&gt;

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