scholarly journals Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

2011 ◽  
Vol 4 (3) ◽  
pp. 3017-3053 ◽  
Author(s):  
A. Held ◽  
D. A. Orsini ◽  
P. Vaattovaara ◽  
M. Tjernström ◽  
C. Leck
Keyword(s):  
Heat Flux ◽  
Arctic Ocean ◽  
Particle Deposition ◽  
Deposition Velocity ◽  
Sensible Heat Flux ◽  
Number Concentration ◽  
The Arctic ◽  
Sensible Heat ◽  
Central Arctic Ocean ◽  
Near Surface

Abstract. Temperature and particle number concentration profiles were measured at small height intervals above open and frozen leads and snow surfaces in the central Arctic. The device used was a gradient pole designed to investigate potential particle sources over the central Arctic Ocean. The collected data was fitted according to basic logarithmic flux-profile relationships to calculate the sensible heat flux and particle deposition velocity. Independent measurements by the eddy covariance technique were conducted at the same location. General agreement was observed between the two methods when logarithmic profiles could be fitted to the gradient pole data. In general, snow surfaces behaved as weak particle sinks with a maximum deposition velocity vd = 1.3 mm s−1 measured with the gradient pole. The lead surface behaved as a weak particle source before freeze-up with an upward flux Fc = 5.7 × 104 particles m−2 s−1, and as a relatively strong heat source after freeze-up, with an upward maximum sensible heat flux H = 13.1 W m−2. Over the frozen lead, however, we were unable to resolve any significant aerosol profiles.

scholarly journals Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

2011 ◽  
Vol 4 (8) ◽  
pp. 1603-1616 ◽  
Author(s):  
A. Held ◽  
D. A. Orsini ◽  
P. Vaattovaara ◽  
M. Tjernström ◽  
C. Leck
Keyword(s):  
Heat Flux ◽  
Arctic Ocean ◽  
Particle Deposition ◽  
Deposition Velocity ◽  
Sensible Heat Flux ◽  
Number Concentration ◽  
The Arctic ◽  
Sensible Heat ◽  
Central Arctic Ocean ◽  
Near Surface

Abstract. Temperature and particle number concentration profiles were measured at small height intervals above open and frozen leads and snow surfaces in the central Arctic. The device used was a gradient pole designed to investigate potential particle sources over the central Arctic Ocean. The collected data were fitted according to basic logarithmic flux-profile relationships to calculate the sensible heat flux and particle deposition velocity. Independent measurements by the eddy covariance technique were conducted at the same location. General agreement was observed between the two methods when logarithmic profiles could be fitted to the gradient pole data. In general, snow surfaces behaved as weak particle sinks with a maximum deposition velocity vd = 1.3 mm s−1 measured with the gradient pole. The lead surface behaved as a weak particle source before freeze-up with an upward flux Fc = 5.7 × 104 particles m−2 s−1, and as a relatively strong heat source after freeze-up, with an upward maximum sensible heat flux H = 13.1 W m−2. Over the frozen lead, however, we were unable to resolve any significant aerosol profiles.

scholarly journals Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics

2008 ◽  
Vol 9 (1) ◽  
pp. 165-171 ◽  
Author(s):  
J. L. Heitman ◽  
R. Horton ◽  
T. J. Sauer ◽  
T. M. DeSutter
Keyword(s):  
Heat Flux ◽  
Soil Water ◽  
Heat Balance ◽  
Measurement Techniques ◽  
Sensible Heat Flux ◽  
Soil Surface ◽  
Water Evaporation ◽  
Sensible Heat ◽  
Near Surface ◽  
Evaporation Zone

Abstract Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patterns. Immediately after rainfall, evaporation occurred near the soil surface. Within 6 days after rainfall, the evaporation zone proceeded > 13 mm into the soil profile. Evaporation rates at the 3-mm depth reached peak values > 0.25 mm h−1. Evaporation occurred simultaneously at multiple measured depth increments, but with time lag between peak evaporation rates for depths deeper below the soil surface. Implementation of finescale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation.

scholarly journals Measurements of turbulence transfer in the near-surface layer over the Antarctic sea-ice surface from April through November in 2016

2020 ◽  
Vol 61 (82) ◽  
pp. 12-23
Author(s):  
Changwei Liu ◽  
Zhiqiu Gao ◽  
Qinghua Yang ◽  
Bo Han ◽  
Hong Wang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Roughness Length ◽  
Sensible Heat Flux ◽  
Surface Energy Budget ◽  
The Arctic ◽  
Conductive Heat ◽  
Near Surface ◽  
Antarctic Sea Ice ◽  
The Antarctic

AbstractThe surface energy budget over the Antarctic sea ice from 8 April 2016 through 26 November 2016 are presented. From April to October, Sensible heat flux (SH) and subsurface conductive heat flux (G) were the heat source of surface while latent heat flux (LE) and net radiation flux (Rn) were the heat sink of surface. Our results showed larger downward SH (due to the warmer air in our site) and upward LE (due to the drier air and higher wind speed in our site) compared with SHEBA data. However, the values of SH in N-ICE2015 campaign, which located at a zone with stronger winds and more advection of heat in the Arctic, were comparable to our results under clear skies. The values of aerodynamic roughness length (z0m) and scalar roughness length for temperature (z0h), being 1.9 × 10−3 m and 3.7 × 10−5 m, were suggested in this study. It is found that snow melting might increase z0m. Our results also indicate that the value of log(z0h/z0m) was related to the stability of stratification. In addition, several representative parameterization schemes for z0h have been tested and a couple of schemes were found to make a better performance.

scholarly journals Meteorological and cloud conditions during the Arctic Ocean 2018 expedition

2020 ◽  
Author(s):  
Jutta Vüllers ◽  
Peggy Achtert ◽  
Ian M. Brooks ◽  
Michael Tjernström ◽  
John Prytherch ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
High Frequency ◽  
Mixed Boundary ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Central Arctic Ocean ◽  
Surface Exchange ◽  
Surface Water Chemistry ◽  
Near Surface ◽  
The Arctic Ocean

Abstract. The Arctic Ocean 2018 (AO2018) expedition took place in the central Arctic Ocean in August and September 2018. An extensive suite of instrumentation provided detailed measurements of surface water chemistry and biology, sea ice and ocean physical and biogeochemical properties, surface exchange processes, aerosols, clouds, and the state of the atmosphere. The measurements provide important information on the coupling of the ocean and ice surface to the atmosphere and in particular to clouds. This paper provides: (i) an overview of the synoptic-scale atmospheric conditions and its climatological anomaly to help interpret the process studies and put the detailed observations from AO2018 into a larger context, both spatially and temporally; (ii) a statistical analysis of the thermodynamic and near-surface meteorological conditions, boundary layer, cloud, and fog characteristics; (iii) a comparison of the results to observations from earlier Arctic Ocean expeditions, in particular AOE96, SHEBA, AOE2001, ASCOS, ACSE, and AO2016, to provide an assessment of the representativeness of the measurements. The results show that near-surface conditions were broadly comparable to earlier experiments, however the thermodynamic vertical structure was quite different. An unusually high frequency of well-mixed boundary layers up to about 1 km depth occurred, and only a few cases of the prototypical Arctic summer single-layer stratocumulus deck were observed. Instead, an unexpectedly high amount of multiple cloud layers and mid-level clouds was present throughout the campaign. These differences from previous studies are related to the high frequency of cyclonic activity in the central Arctic in 2018.

scholarly journals The open-ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

2016 ◽  
Vol 16 (20) ◽  
pp. 13173-13184 ◽  
Author(s):  
Manisha Ganeshan ◽  
Dong L. Wu
Keyword(s):  
Heat Flux ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Surface Wind Speed ◽  
Open Ocean ◽  
The Other ◽  
Arctic Climate ◽  
The Arctic ◽  
Sensible Heat ◽  
Early Fall

Abstract. The increasing ice-free area during late summer has transformed the Arctic to a climate system with more dynamic boundary layer (BL) clouds and seasonal sea ice growth. The open-ocean sensible heat flux, a crucial mechanism of excessive ocean heat loss to the atmosphere during the fall freeze season, is speculated to play an important role in the recently observed cloud cover increase and BL instability. However, lack of observations and understanding of the resilience of the proposed mechanisms, especially in relation to meteorological and interannual variability, has left a poorly constrained BL parameterization scheme in Arctic climate models. In this study, we use multi-year Japanese cruise-ship observations from R/V Mirai over the open Arctic Ocean to characterize the surface sensible heat flux (SSHF) during early fall and investigate its contribution to BL turbulence. It is found that mixing by SSHF is favored during episodes of high surface wind speed and is also influenced by the prevailing cloud regime. The deepest BLs and maximum ocean–atmosphere temperature difference are observed during cold air advection (associated with the stratocumulus regime), yet, contrary to previous speculation, the efficiency of sensible heat exchange is low. On the other hand, the SSHF contributes significantly to BL mixing during the uplift (low pressure) followed by the highly stable (stratus) regime. Overall, it can explain  ∼  10 % of the open-ocean BL height variability, whereas cloud-driven (moisture and radiative) mechanisms appear to be the other dominant source of convective turbulence. Nevertheless, there is strong interannual variability in the relationship between the SSHF and the BL height which can be intensified by the changing occurrence of Arctic climate patterns, such as positive surface wind speed anomalies and more frequent conditions of uplift. This study highlights the need for comprehensive BL observations like the R/V Mirai for better understanding and predicting the dynamic nature of the Arctic climate.

scholarly journals A Variational Method for Computation of Sensible Heat Flux over the Arctic Sea Ice

2009 ◽  
Vol 26 (4) ◽  
pp. 838-845 ◽  
Author(s):  
Zuohao Cao ◽  
Jianmin Ma
Keyword(s):  
Heat Flux ◽  
Variational Method ◽  
Sea Ice ◽  
Variational Approach ◽  
Sensible Heat Flux ◽  
Arctic Sea Ice ◽  
Eddy Correlation ◽  
The Arctic ◽  
Sensible Heat ◽  
Arctic Sea

Abstract In this study, a variational approach was employed to compute surface sensible heat flux over the Arctic sea ice. Because the variational approach is able to take into account information from the Monin–Obukhov similarity theory (MOST) as well as the observed meteorological information, it is expected to improve the pure MOST-based approach in computation of sensible heat flux. Verifications using the direct eddy-correlation measurements over the Arctic sea ice during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment period of 1997/98 show that the variational method yields good agreement between the computed and the measured sensible heat fluxes. The variational method is also shown to be more accurate than the traditional MOST method in the computation of sensible heat flux over the Arctic sea ice.

scholarly journals The annual surface energy budget of a high-arctic permafrost site on Svalbard, Norway

2009 ◽  
Vol 3 (2) ◽  
pp. 245-263 ◽  
Author(s):  
S. Westermann ◽  
J. Lüers ◽  
M. Langer ◽  
K. Piel ◽  
J. Boike
Keyword(s):  
Heat Flux ◽  
Surface Energy ◽  
Latent Heat ◽  
Energy Budget ◽  
Sensible Heat Flux ◽  
Surface Energy Budget ◽  
Wave Radiation ◽  
Sensible Heat ◽  
Near Surface ◽  
Ground Heat Flux

Abstract. Independent measurements of radiation, sensible and latent heat fluxes and the ground heat flux are used to describe the annual cycle of the surface energy budget at a high-arctic permafrost site on Svalbard. During summer, the net short-wave radiation is the dominant energy source, while well developed turbulent processes and the heat flux in the ground lead to a cooling of the surface. About 15% of the net radiation is consumed by the seasonal thawing of the active layer in July and August. The Bowen ratio is found to vary between 0.25 and 2, depending on water content of the uppermost soil layer. During the polar night in winter, the net long-wave radiation is the dominant energy loss channel for the surface, which is mainly compensated by the sensible heat flux and, to a lesser extent, by the ground heat flux, which originates from the refreezing of the active layer. The average annual sensible heat flux of −6.9 Wm−2 is composed of strong positive fluxes in July and August, while negative fluxes dominate during the rest of the year. With 6.8 Wm−2, the latent heat flux more or less compensates the sensible heat flux in the annual average. Strong evaporation occurs during the snow melt period and particularly during the snow-free period in summer and fall. When the ground is covered by snow, latent heat fluxes through sublimation of snow are recorded, but are insignificant for the average surface energy budget. The near-surface atmospheric stratification is found to be predominantly unstable to neutral, when the ground is snow-free, and stable to neutral for snow-covered ground. Due to long-lasting near-surface inversions in winter, an average temperature difference of approximately 3 K exists between the air temperature at 10 m height and the surface temperature of the snow. As such comprehensive data sets are sparse for the Arctic, they are of great value to improve process understanding and support modeling efforts on the present-day and future arctic climate and permafrost conditions.

scholarly journals Meteorological and cloud conditions during the Arctic Ocean 2018 expedition

2021 ◽  
Vol 21 (1) ◽  
pp. 289-314 ◽  
Author(s):  
Jutta Vüllers ◽  
Peggy Achtert ◽  
Ian M. Brooks ◽  
Michael Tjernström ◽  
John Prytherch ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
High Frequency ◽  
Heat Budget ◽  
Mixed Boundary ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
Surface Water Chemistry ◽  
Near Surface ◽  
The Arctic Ocean ◽  
Arctic Summer

Abstract. The Arctic Ocean 2018 (AO2018) took place in the central Arctic Ocean in August and September 2018 on the Swedish icebreaker Oden. An extensive suite of instrumentation provided detailed measurements of surface water chemistry and biology, sea ice and ocean physical and biogeochemical properties, surface exchange processes, aerosols, clouds, and the state of the atmosphere. The measurements provide important information on the coupling of the ocean and ice surface to the atmosphere and in particular to clouds. This paper provides (i) an overview of the synoptic-scale atmospheric conditions and their climatological anomaly to help interpret the process studies and put the detailed observations from AO2018 into a larger context, both spatially and temporally; (ii) a statistical analysis of the thermodynamic and near-surface meteorological conditions, boundary layer, cloud, and fog characteristics; and (iii) a comparison of the results to observations from earlier Arctic Ocean expeditions – in particular AOE1996 (Arctic Ocean Expedition 1996), SHEBA (Surface Heat Budget of the Arctic Ocean), AOE2001 (Arctic Ocean Experiment 2001), ASCOS (Arctic Summer Cloud Ocean Study), ACSE (Arctic Clouds in Summer Experiment), and AO2016 (Arctic Ocean 2016) – to provide an assessment of the representativeness of the measurements. The results show that near-surface conditions were broadly comparable to earlier experiments; however the thermodynamic vertical structure was quite different. An unusually high frequency of well-mixed boundary layers up to about 1 km depth occurred, and only a few cases of the “prototypical” Arctic summer single-layer stratocumulus deck were observed. Instead, an unexpectedly high amount of multiple cloud layers and mid-level clouds were present throughout the campaign. These differences from previous studies are related to the high frequency of cyclonic activity in the central Arctic in 2018.

scholarly journals The open ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

2016 ◽  
Author(s):  
Manisha Ganeshan ◽  
Dong L. Wu
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Sensible Heat Flux ◽  
Open Ocean ◽  
Arctic Climate ◽  
The Arctic ◽  
Sensible Heat ◽  
Cloud Regime ◽  
Ocean Atmosphere ◽  
Early Fall

Abstract. The increasing ice-free area during late summer has transformed the Arctic to a climate system with more dynamic boundary layer clouds and seasonal sea ice growth. The open ocean sensible heat flux, a crucial mechanism of excessive ocean heat loss to the atmosphere during the fall freeze season, is speculated to play an important role in the recently observed cloud cover increase and boundary layer (BL) instability. However, lack of observations and understanding of the resilience of the proposed mechanisms, especially in relation to meteorological and interannual variability, has left a poorly constrained BL parameterization scheme in Arctic climate models. In this study, we use multi-year Japanese cruise ship observations from R/V Mirai over the open Arctic Ocean to characterize the surface sensible heat flux (SSHF) during early fall and investigate its contribution to BL turbulence. It is found that surface-generated turbulent mixing is favored during episodes of high wind speed, and is also influenced by the prevailing cloud regime. The maximum ocean-atmosphere temperature difference is observed during cold air advection (associated with the stratocumulus regime). Yet, contrary to previous speculation, the efficiency of turbulent heat exchange is low. The SSHF contribution to BL mixing is significant during the uplift (low-pressure) followed by the highly stable (stratus cloud) regime. Overall, the open ocean sensible heat flux can explain ~ 10 % of the BL height variability, whereas mechanisms such as cloud-driven turbulence appear to be dominant. Nevertheless, there is strong interannual variability in the strength of the ocean-atmosphere coupling. The changing occurrence of Arctic climate patterns, such as positive surface wind speed anomalies, can easily enhance the ocean's contribution to BL turbulence. This study highlights the need for comprehensive boundary layer observations such as the R/V Mirai for better understanding and predicting the dynamic nature of the Arctic climate.

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