scholarly journals Processes influencing heat transfer in the near-surface ice of Greenland's ablation zone

2018 ◽  
Vol 12 (10) ◽  
pp. 3215-3227 ◽  
Author(s):  
Benjamin H. Hills ◽  
Joel T. Harper ◽  
Toby W. Meierbachtol ◽  
Jesse V. Johnson ◽  
Neil F. Humphrey ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Thermal Structure ◽  
Radiative Energy ◽  
Ablation Zone ◽  
Transient Heating ◽  
Near Surface ◽  
The Mean ◽  
Surface Ice ◽  
Mean Annual Air Temperature

Abstract. To assess the influence of various heat transfer processes on the thermal structure of near-surface ice in Greenland's ablation zone, we compare in situ measurements with thermal modeling experiments. A total of seven temperature strings were installed at three different field sites, each with between 17 and 32 sensors and extending up to 21 m below the ice surface. In one string, temperatures were measured every 30 min, and the record is continuous for more than 3 years. We use these measured ice temperatures to constrain our modeling experiments, focusing on four isolated processes and assessing the relative importance of each for the near-surface ice temperature: (1) the moving boundary of an ablating surface, (2) thermal insulation by snow, (3) radiative energy input, and (4) subsurface ice temperature gradients below the seasonally active near-surface layer. In addition to these four processes, transient heating events were observed in two of the temperature strings. Despite no observations of meltwater pathways to the subsurface, these heating events are likely the refreezing of liquid water below 5–10 m of cold ice. Together with subsurface refreezing, the five heat transfer mechanisms presented here account for measured differences of up to 3 ∘C between the mean annual air temperature and the ice temperature at the depth where annual temperature variability is dissipated. Thus, in Greenland's ablation zone, the mean annual air temperature is not a reliable predictor of the near-surface ice temperature, as is commonly assumed.

scholarly journals Processes influencing near-surface heat transfer in Greenland's ablation zone

2018 ◽  
Author(s):  
Benjamin H. Hills ◽  
Joel T. Harper ◽  
Toby W. Meierbachtol ◽  
Jesse V. Johnson ◽  
Neil F. Humphrey ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Moving Boundary ◽  
Radiative Energy ◽  
Ablation Zone ◽  
Transient Heating ◽  
Near Surface ◽  
The Mean ◽  
Surface Ice ◽  
Mean Annual Air Temperature

Abstract. To assess the influence of various mechanisms of heat transfer on the near-surface ice of Greenland's ablation zone, we incorporate highly resolved measurements of ice temperature into thermal modeling experiments. Seven separate temperature strings were installed at three different field sites, each with between 17 and 32 sensors and extending up to 20 m below the surface. In one string, temperatures were measured every 30 minutes, and the record is continuous for more than three years. We use these measured ice temperatures to constrain modeling analyses focused on four isolated processes to assess the relative importance of each to the near-surface ice temperature: 1) the moving boundary of an ablating surface, 2) thermal insulation by snow, 3) radiative energy input, and 4) temperature gradients below the seasonally active near-surface layer. In addition to these four processes, transient heating events were observed in two of the temperature strings. Despite no observations of meltwater pathways to the subsurface, these heating events are likely the refreezing of liquid water below 5–10 m of cold ice. Together with subsurface refreezing, the five heat transfer mechanisms presented here account for measured differences of up to 3 °C between the ice temperature at the depth where annual temperature variability is dissipated and the mean annual air temperature. Thus, in Greenland's ablation zone, the mean annual air temperature cannot be used to predict the near-surface ice temperature, as is commonly assumed.

scholarly journals Supplementary material to "Processes influencing near-surface heat transfer in Greenland's ablation zone"

2018 ◽  
Author(s):  
Benjamin H. Hills ◽  
Joel T. Harper ◽  
Toby W. Meierbachtol ◽  
Jesse V. Johnson ◽  
Neil F. Humphrey ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Ablation Zone ◽  
Near Surface ◽  
Surface Heat Transfer ◽  
Supplementary Material

scholarly journals Soil temperature study in Puerto Rico

1969 ◽  
Vol 93 (3-4) ◽  
pp. 149-171
Author(s):  
Jorge L. Lugo-Camacho ◽  
Miguel A. Muñoz ◽  
Juan Pérez-Bolívar ◽  
Gregory R. Brannon
Keyword(s):  
Puerto Rico ◽  
Soil Moisture ◽  
Soil Temperature ◽  
Sea Level ◽  
Air Temperature ◽  
Temperature Regime ◽  
Soil Series ◽  
Soil Temperature Regime ◽  
The Mean ◽  
Mean Annual Air Temperature

Soil temperature measurements from a climate monitoring network in Puerto Rico were evaluated and the difference between mean summer and mean winter soil temperature, known as isotivity value, was calculated. Air and soil temperature was collected from five weather stations of the USDA-Natural Resources Conservation Service from sea level to 1,019 m above sea level and from different soil moisture regimes. Isotivity values ranged from 1.2 to 3.9° C with an average of 2.6° C. The 750-m elevation was identified as the limit between the isohyperthermic and isothermic soil temperature regimes in the perudic soil moisture regime in Puerto Rico. The greatest differences between mean annual soil temperature and mean annual air temperature were observed at Guánica, Combate and Guilarte (2.1 ° C) stations. The smallest differences were observed at Maricao (0.8° C) and Isabela (1.8° C) stations. The study also indicated that the mean annual soil temperature in Puerto Rico can be estimated by adding 1.8° C to the mean annual air temperature or by the equation y = -0.007x + 28.0° C. The equation indicates that 97 percent of the time the behavior of the mean annual soil temperature is a function of elevation. According to the updated soil temperature regime boundaries, eight soil series were established in the Soil Survey of San Germán Area. In an area under the isothermic soil temperature regime, four soil series were classified as Oxisols (Haploperox), two soil series as Inceptisols (Eutrudepts) and two soil series as Mollisols (Argiudolls). This is the first field recognition of the Haploperox soil great group in the United States and its territories.

Permafrost and active layer research on James Ross Island: An overview

2019 ◽  
Vol 9 (1) ◽  
pp. 20-36 ◽  
Author(s):  
Filip Hrbáček ◽  
Daniel Nývlt ◽  
Kamil Láska ◽  
Michaela Kňažková ◽  
Barbora Kampová ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Thermal Regime ◽  
Ground Temperature ◽  
Active Layer Thickness ◽  
Near Surface ◽  
James Ross Island ◽  
The Mean

This study summarizes the current state of the active layer and permafrost research on James Ross Island. The analysis of climate parameters covers the reference period 2011–2017. The mean annual air temperature at the AWS-JGM site was -6.9°C (ranged from -3.9°C to -8.2°C). The mean annual ground temperature at the depth of 5 cm was -5.5°C (ranged from -3.3°C to -6.7°C) and it also reached -5.6°C (ranged from -4.0 to -6.8°C) at the depth of 50 cm. The mean daily ground temperature at the depth of 5 cm correlated moderately up to strongly with the air temperature depending on the season of the year. Analysis of the snow effect on the ground thermal regime confirmed a low insulating effect of snow cover when snow thickness reached up to 50 cm. A thicker snow accumulation, reaching at least 70 cm, can develop around the hyaloclastite breccia boulders where a well pronounced insulation effect on the near-surface ground thermal regime was observed. The effect of lithology on the ground physical properties and the active layer thickness was also investigated. Laboratory analysis of ground thermal properties showed variation in thermal conductivity (0.3 to 0.9 W m-1 K-1). The thickest active layer (89 cm) was observed on the Berry Hill slopes site, where the lowest thawing degree days index (321 to 382°C·day) and the highest value of thermal conductivity (0.9 W m-1 K-1) was observed. The clearest influence of lithological conditions on active layer thickness was observed on the CALM-S grid. The site comprises a sandy Holocene marine terrace and muddy sand of the Whisky Bay Formation. Surveying using a manual probe, ground penetrating radar, and an electromagnetic conductivity meter clearly showed the effect of the lithological boundary on local variability of the active layer thickness.

Spatial Prediction of Soil Temperature in China

2014 ◽  
Vol 955-959 ◽  
pp. 3718-3723
Author(s):  
Hui Zhi Zhang ◽  
Xue Zheng Shi
Keyword(s):  
Soil Temperature ◽  
Spatial Patterns ◽  
Air Temperature ◽  
Ordinary Kriging ◽  
Spatial Prediction ◽  
Regression Kriging ◽  
Auxiliary Variables ◽  
Geostatistical Methods ◽  
The Mean ◽  
Mean Annual Air Temperature

Temperature affects many soil biochemical and geochemical processes. The growth of plants, seed germination, circulations of carbon and nitrogen are all significantly influenced by soil temperature, thus it is important to estimate the spatial pattern of soil temperature. This paper shows the results of spatial patterns of mean annual soil temperature interpolated from the measurements of 698 meteorological stations in China. Four geostatistical methods, ordinary kriging (OK), regression kriging with mean annual air temperature (RK-1), regression kriging with latitude, longitude and elevation (RK-2) and regression kriging with multi-auxiliary predictors (RK-3), were compared. Ordinary kriging (OK) directly interpolated the mean annual soil temperature data extracted from meteorological stations to obtain the spatial patterns of the mean annual soil temperature. For the three regression kriging methods, intensive auxiliary variables (mean annual air temperature, elevation, latitude and longitude), which were correlated with mean annual soil temperature, were used to increase the accuracy of estimation. The results suggested that RK-3 preformed best, followed by RK-1 and RK-2. The intensive data of auxiliary variables used in the regression kriging significantly improved the accuracy of interpolation results.

scholarly journals On the Temperature Distribution of Glaciers in China

1990 ◽  
Vol 36 (123) ◽  
pp. 210-216 ◽  
Author(s):  
Huang Maohuan
Keyword(s):  
Surface Layer ◽  
Temperature Distribution ◽  
Air Temperature ◽  
Minimum Temperature ◽  
Low Temperatures ◽  
Characteristic Temperature ◽  
Near Surface ◽  
Ablation Area ◽  
Polar Type ◽  
Mean Annual Air Temperature

AbstractTo date, the temperatures of 22 glaciers in China have been measured. It is suggested that the minimum temperature at the base of the active layer in the upper part of the ablation area (Tmin) be used as a characteristic temperature and compared with mean annual air temperature (Ta). The temperature distribution is discussed for various glaciers. Polar-type glaciers are characterized by low temperatures withTmin< −10°C,Tminclose toTvand a cold base in general; sub-polar-type glaciers with −10°C <Tmin< −1.0°C,Tminhigher thanTvand a melting base are usually located beneath the middle of the ablation area; and temperate-type glaciers withTmin< −1.0°C, certainly higher thanTaand a sub-freezing near-surface layer in the ablation area all the year round, because the snow cover is thinner in winter.

scholarly journals On the Temperature Distribution of Glaciers in China

1990 ◽  
Vol 36 (123) ◽  
pp. 210-216 ◽  
Author(s):  
Huang Maohuan
Keyword(s):  
Surface Layer ◽  
Temperature Distribution ◽  
Air Temperature ◽  
Minimum Temperature ◽  
Low Temperatures ◽  
Characteristic Temperature ◽  
Near Surface ◽  
Ablation Area ◽  
Polar Type ◽  
Mean Annual Air Temperature

AbstractTo date, the temperatures of 22 glaciers in China have been measured. It is suggested that the minimum temperature at the base of the active layer in the upper part of the ablation area (Tmin) be used as a characteristic temperature and compared with mean annual air temperature (Ta). The temperature distribution is discussed for various glaciers. Polar-type glaciers are characterized by low temperatures with Tmin < −10°C, Tmin close to Tv and a cold base in general; sub-polar-type glaciers with −10°C < Tmin < −1.0°C, Tmin higher than Tv and a melting base are usually located beneath the middle of the ablation area; and temperate-type glaciers with Tmin < −1.0°C, certainly higher than Ta and a sub-freezing near-surface layer in the ablation area all the year round, because the snow cover is thinner in winter.

Evaluation of MM5 and HadGEM3-RA hindcast in the CORDEX East Asia Phase Ⅱ: near-surface air temperature

2020 ◽  
Author(s):  
Seok-Woo Shin ◽  
Dong-Hyun Cha ◽  
Taehyung Kim ◽  
Gayoung Kim ◽  
Changyoung Park ◽  
...  
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
Climate Models ◽  
Extreme Values ◽  
Regional Climate ◽  
Surface Air Temperature ◽  
Regional Climate Models ◽  
Near Surface ◽  
The Mean ◽  
Cordex East Asia

&lt;p&gt;Extreme temperature can have a devastating impact on the ecological environment (i.e., human health and crops) and the socioeconomic system. To adapt to and cope with the rapidly changing climate, it is essential to understand the present climate and to estimate the future change in terms of temperature. In this study, we evaluate the characteristics of near-surface air temperature (SAT) simulated by two regional climate models (i.e., MM5 and HadGEM3-RA) over East Asia, focusing on the mean and extreme values. To analyze extreme climate, we used the indices for daily maximum (Tmax) and minimum (Tmin) temperatures among the developed Expert Team on Climate Change Detection and Indices (ETCCDI) indices. In the results of the CORDEX-East Asia phase &amp;#8544;, the mean and extreme values of SAT for DJF (JJA) tend to be colder (warmer) than observation data over the East Asian region. In those of CORDEX-East Asia phase &amp;#8545;, the mean and extreme values of SAT for DJF and JJA have warmer than those of the CORDEX-East Asia phase &amp;#8544; except for those of HadGEM3-RA for DJF. Furthermore, the Extreme Temperature Range (ETR, maximum value of Tmax - minimum value of Tmin) of CORDEX-East Asia phase &amp;#8544; data, which are significantly different from those of observation data, are reduced in that of CORDEX-East Asia phase &amp;#8545;. Consequently, the high-resolution regional climate models play a role in the improvement of the cold bias having the relatively low-resolution ones. To understand the reasons for the improved and weak points of regional climate models, we investigated the atmospheric field (i.e., flow, air mass, precipitation, and radiation) influencing near-surface air temperature. Model performances for SAT over East Asia were influenced by the expansion of the western North Pacific subtropical high and the location of convective precipitation in JJA and by the contraction of the Siberian high, the spatial distribution of snowfall and associated upwelling longwave radiation in DJF.&lt;/p&gt;

scholarly journals Regional Climate Change (Karelia, Russia)

2015 ◽  
Vol 2 ◽  
pp. 356
Author(s):  
Larisa Nazarova
Keyword(s):  
Air Temperature ◽  
Global Climate ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Climatic Conditions ◽  
Temperature And Precipitation ◽  
The Mean ◽  
Weather Stations ◽  
Meteorological Observations ◽  
Mean Annual Air Temperature

The overview of climatic conditions in Karelia is based on the data from meteorological observations carried out in 1951-2009 at Roskomgidromet weather stations situated in the study area. Taking the period in question into account, the mean annual air temperature norm has increased by 0.2-0.3°C. The greatest deviation from multiyear averages of mean monthly air temperature is observed in January and March. The investigation of the changes the basic regional climate characteristics is very important in present time because the global climate is changed. The analysis the data about air temperature and precipitation, that were obtained for the different meteorological stations in the investigated region, shows that the regional climate is changed and the main tendencies are directly proportional to the change of the global characteristics.

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