scholarly journals 30 years of upper air soundings on board of R/V POLARSTERN

2016 ◽  
Author(s):  
Amelie Driemel ◽  
Bernd Loose ◽  
Hannes Grobe ◽  
Rainer Sieger ◽  
Gert König-Langlo
Keyword(s):  
Austral Summer ◽  
Weather Forecast ◽  
The Arctic ◽  
Radiosonde Data ◽  
Polar Regions ◽  
Weather Forecasts ◽  
Northern Summer ◽  
Special Value ◽  
Remote Sensing Systems ◽  
Antarctic Research

Abstract. The research vessel and supply icebreaker POLARSTERN is the flagship of the Alfred-Wegener-Institut in Bremerhaven (Germany) and one of the infrastructural pillars of German Antarctic research. Since its commissioning in 1982, POLARSTERN has conducted 30 campaigns to Antarctica (157 legs, mostly austral summer), and 29 to the Arctic (94 legs, northern summer). Usually, POLARSTERN is more than 300 days per year in operation and crosses the Atlantic Ocean in a meridional section twice a year. The first radiosonde on POLARSTERN was released on the 29th of December 1982, two days after POLARSTERN started on its maiden voyage to the Antarctic. And these daily soundings have continued up to the present. Due to the fact that POLARSTERN has reliably and regularly been providing upper air observations from data sparse regions (oceans and polar regions), the radiosonde data are of special value for researchers and weather forecast services alike. In the course of 30 years (1982-12-29 to 2012-11-25) a total of 12378 radiosonde balloons were started on POLARSTERN. All radiosonde data can now be found at doi:10.1594/PANGAEA.810000. Each dataset contains the directly measured parameters air temperature, relative humidity and air pressure, and the derived altitude, wind direction and wind speed. 432 datasets additionally contain ozone measurements. Although more sophisticated techniques (meteorological satellites, aircraft observation, remote sensing systems, etc.) have nowadays become increasingly important, the high vertical resolution and quality of radiosonde data remains paramount for weather forecasts and modelling approaches.

scholarly journals 30 years of upper air soundings on board of R/V <i>POLARSTERN</i>

2016 ◽  
Vol 8 (1) ◽  
pp. 213-220 ◽  
Author(s):  
Amelie Driemel ◽  
Bernd Loose ◽  
Hannes Grobe ◽  
Rainer Sieger ◽  
Gert König-Langlo
Keyword(s):  
Austral Summer ◽  
Weather Forecast ◽  
The Arctic ◽  
Radiosonde Data ◽  
Data Sets ◽  
Polar Regions ◽  
Data Set ◽  
Northern Summer ◽  
Special Value ◽  
Remote Sensing Systems

Abstract. The research vessel and supply icebreaker POLARSTERN is the flagship of the Alfred-Wegener-Institut in Bremerhaven (Germany) and one of the infrastructural pillars of German Antarctic research. Since its commissioning in 1982, POLARSTERN has conducted 30 campaigns to Antarctica (157 legs, mostly austral summer), and 29 to the Arctic (94 legs, northern summer). Usually, POLARSTERN is more than 300 days per year in operation and crosses the Atlantic Ocean in a meridional section twice a year. The first radiosonde on POLARSTERN was released on the 29 December 1982, 2 days after POLARSTERN started on its maiden voyage to the Antarctic. And these daily soundings have continued up to the present. Due to the fact that POLARSTERN has reliably and regularly been providing upper air observations from data sparse regions (oceans and polar regions), the radiosonde data are of special value for researchers and weather forecast services alike. In the course of 30 years (29 December 1982 to 25 November 2012) a total of 12 378 radiosonde balloons were started on POLARSTERN. All radiosonde data can now be found at König-Langlo (2015, doi:10.1594/PANGAEA.810000). Each data set contains the directly measured parameters air temperature, relative humidity and air pressure, and the derived altitude, wind direction and wind speed. 432 data sets additionally contain ozone measurements.Although more sophisticated techniques (meteorological satellites, aircraft observation, remote-sensing systems, etc.) have nowadays become increasingly important, the high vertical resolution and quality of radiosonde data remains paramount for weather forecasts and modelling approaches.

scholarly journals Validation of 7 Years in-Flight HY-2A Calibration Microwave Radiometer Products Using Numerical Weather Model and Radiosondes

2019 ◽  
Vol 11 (13) ◽  
pp. 1616 ◽  
Author(s):  
Zhilu Wu ◽  
Jungang Wang ◽  
Yanxiong Liu ◽  
Xiufeng He ◽  
Yang Liu ◽  
...  
Keyword(s):  
Microwave Radiometer ◽  
The Arctic ◽  
Radiosonde Data ◽  
Polar Regions ◽  
Systematic Bias ◽  
Tropical Regions ◽  
Numerical Weather ◽  
Numerical Weather Model ◽  
Weather Model ◽  
Interim Products

Haiyang-2A (HY-2A) has been working in-flight for over seven years, and the accuracy of HY-2A calibration microwave radiometer (CMR) data is extremely important for the wet troposphere delay correction (WTC) in sea surface height (SSH) determination. We present a comprehensive evaluation of the HY-2A CMR observation using the numerical weather model (NWM) for all the data available period from October 2011 to February 2018, including the WTC and the precipitable water vapor (PWV). The ERA(ECMWF Re-Analysis)-Interim products from European Centre for Medium-Range Weather Forecasts (ECMWF) are used for the validation of HY-2A WTC and PWV products. In general, a global agreement of root-mean-square (RMS) of 2.3 cm in WTC and 3.6 mm in PWV are demonstrated between HY-2A observation and ERA-Interim products. Systematic biases are revealed where before 2014 there was a positive WTC/PWV bias and after that, a negative one. Spatially, HY-2A CMR products show a larger bias in polar regions compared with mid-latitude regions and tropical regions and agree better in the Antarctic than in the Arctic with NWM. Moreover, HY-2A CMR products have larger biases in the coastal area, which are all caused by the brightness temperature (TB) contamination from land or sea ice. Temporally, the WTC/PWV biases increase from October 2011 to March 2014 with a systematic bias over 1 cm in WTC and 2 mm in PWV, and the maximum RMS values of 4.62 cm in WTC and 7.61 mm in PWV occur in August 2013, which is because of the unsuitable retrieval coefficients and systematic TB measurements biases from 37 GHz band. After April 2014, the TB bias is corrected, HY-2A CMR products agree very well with NWM from April 2014 to May 2017 with the average RMS of 1.68 cm in WTC and 2.65 mm in PWV. However, since June 2017, TB measurements from the 18.7 GHz band become unstable, which led to the huge differences between HY-2A CMR products and the NWM with an average RMS of 2.62 cm in WTC and 4.33 mm in PWV. HY-2A CMR shows high accuracy when three bands work normally and further calibration for HY-2A CMR is in urgent need. Furtherly, 137 global coastal radiosonde stations were used to validate HY-2A CMR. The validation based on radiosonde data shows the same variation trend in time of HY-2A CMR compared to the results from ECMWF, which verifies the results from ECMWF.

Polar Regions

Ecology ◽  
2012 ◽  
Author(s):  
Dieter Piepenburg ◽  
Manfred Bölter
Keyword(s):  
Metabolic Pathways ◽  
Climatic Conditions ◽  
The Arctic ◽  
Individual Species ◽  
Polar Regions ◽  
Ecological Aspects ◽  
International Projects ◽  
Antarctic Research ◽  
The Rich ◽  
Impacts Of Climate Change

The polar regions have gained the attention of scientists and the general public alike, especially since explorers first visited these remote and inhospitable places, characterized by the most extreme climatic conditions on Earth, and reported their fascination about them. Scientific research, in the modern sense, however, started little more than one hundred years ago, with Fridtjof Nansen’s seminal Fram expedition to the Arctic Ocean (1893–1896). The early studies that followed the “heroic phase” of the exploration of the polar regions addressed a wide variety of topics, ranging from broad landscape descriptions to very detailed analyses of individual species, adaptations, or metabolic pathways. Much work was done on ecological aspects of the polar environments and their differentiation into geographical and biotic regions. The exploitation of the surprisingly great wealth of natural resources the polar regions house, such as the rich whale populations and, later, the abundant Antarctic krill in the Southern Ocean, were an important driving force behind many ecological investigations. In the recent past, the study of the impacts of climate change, which are particularly severe in both polar regions, came increasingly into focus of researchers. Scientific fieldwork in polar regions is difficult and costly, and since the early days, ecological research has largely been conducted within the framework of multidisciplinary, often international projects. Over the last three decades, international cooperation in polar research has greatly increased, most often under the wings of the Scientific Committee on Antarctic Research (SCAR) and the International Arctic Science Committee (IASC).

scholarly journals Twenty Years of Polar Winds from AVHRR: Validation and Comparison with ERA-40

2009 ◽  
Vol 48 (1) ◽  
pp. 24-40 ◽  
Author(s):  
Richard Dworak ◽  
Jeffrey R. Key
Keyword(s):  
Positive Impact ◽  
Weather Prediction ◽  
The Arctic ◽  
Radiosonde Data ◽  
Wind Fields ◽  
Jet Streams ◽  
Reanalysis Product ◽  
Weather Forecasts ◽  
Flow Features ◽  
The Impact

Abstract Recent studies have shown that the Arctic climate has changed markedly over the past 20 years. Two major reanalysis products that can be used for studying recent changes unfortunately exhibit relatively large errors in the wind field over the Arctic where there are few radiosonde data available for assimilation. At least 10 numerical weather prediction centers worldwide have demonstrated that satellite-derived polar winds have a positive impact on global weather forecasts. The impact on reanalyses should be similar. Therefore, a polar wind dataset spanning more than 20 years was generated using Advanced Very High Resolution Radiometer (AVHRR) data. Comparisons with winds from radiosondes show biases in the AVHRR-derived winds of 0.1–0.8 m s−1, depending on the level. In addition, AVHRR has lower root-mean-square speed errors and speed biases than the 40-yr ECMWF reanalysis product (ERA-40) when compared with rawinsondes not assimilated into the reanalysis. Therefore, it is recommended that the historical AVHRR polar winds be assimilated into future versions of the reanalysis products. The authors also explore possible kinematic reasons for the disparities between ERA-40 and AVHRR wind fields. AVHRR and ERA-40 speed and direction differences for various kinematic flow features are investigated. Results show that, on average, AVHRR winds are faster in jet streams and ridges but are slower in troughs and jet exit regions. The results from this study could lead to a better dynamical understanding of why the reanalysis product produces a less-accurate wind vector field over regions that are void of radiosonde data.

scholarly journals Parameterizing anisotropic reflectance of snow surfaces from airborne digital camera observations in Antarctica

2020 ◽  
Vol 14 (11) ◽  
pp. 3959-3978
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Veit Helm ◽  
Evelyn Jäkel ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Outer Part ◽  
Digital Camera ◽  
Austral Summer ◽  
Anisotropic Scattering ◽  
The Arctic ◽  
Polar Regions ◽  
Wavelength Band ◽  
Surface Reflection ◽  
Airborne Measurements

Abstract. The surface reflection of solar radiation comprises an important boundary condition for solar radiative transfer simulations. In polar regions above snow surfaces, the surface reflection is particularly anisotropic due to low Sun elevations and the highly anisotropic scattering phase function of the snow crystals. The characterization of this surface reflection anisotropy is essential for satellite remote sensing over both the Arctic and Antarctica. To quantify the angular snow reflection properties, the hemispherical-directional reflectance factor (HDRF) of snow surfaces was derived from airborne measurements in Antarctica during austral summer in 2013/14. For this purpose, a digital 180∘ fish-eye camera (green channel, 490–585 nm wavelength band) was used. The HDRF was measured for different surface roughness conditions, optical-equivalent snow grain sizes, and solar zenith angles. The airborne observations covered an area of around 1000 km × 1000 km in the vicinity of Kohnen Station (75∘0′ S, 0∘4′ E) at the outer part of the East Antarctic Plateau. The observations include regions with higher (coastal areas) and lower (inner Antarctica) precipitation amounts and frequencies. The digital camera provided upward, angular-dependent radiance measurements from the lower hemisphere. The comparison of the measured HDRF derived for smooth and rough snow surfaces (sastrugi) showed significant differences, which are superimposed on the diurnal cycle. By inverting a semi-empirical kernel-driven bidirectional reflectance distribution function (BRDF) model, the measured HDRF of snow surfaces was parameterized as a function of solar zenith angle, surface roughness, and optical-equivalent snow grain size. This allows a direct comparison of the HDRF measurements with the BRDF derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite product MCD43. For the analyzed cases, MODIS observations (545–565 nm wavelength band) generally underestimated the anisotropy of the surface reflection. The largest deviations were found for the volumetric model weight fvol (average underestimation by a factor of 10). These deviations are likely linked to short-term changes in snow properties.

Is there anything natural about the polar?

Polar Record ◽  
2019 ◽  
Vol 55 (5) ◽  
pp. 326-329
Author(s):  
Justiina Dahl ◽  
Peder Roberts ◽  
Lize-Marié van der Watt
Keyword(s):  
Marine Mammals ◽  
The Arctic ◽  
Polar Regions ◽  
International Geophysical Year ◽  
Alpine Regions ◽  
Polar Research Institute ◽  
Antarctic Research ◽  
Norwegian Polar Institute ◽  
Object Of Study ◽  
Research Institute

AbstractAre similarities of temperature, snow and ice cover, and (certain) marine mammals sufficient to warrant both polar regions being considered a single object of study or governance? We argue that their treatment as a unit is an invitation to examine the motivations behind the choice to be polar rather than Arctic or Antarctic. For individuals such as James Clerk Ross or Roald Amundsen, logistical requirements and analogous goals facilitated careers spanning both the Arctic and the Antarctic. This trend continued through the 20th century as individual scientists studying phenomena such as glaciers, sea ice, or aurora defined their research as “polar” in nature. Organisations such as the Scott Polar Research Institute and Norwegian Polar Institute could draw on traditions of national exploration in both polar regions, while the Arctic and Antarctic Research Institute in St. Petersburg gained its southern mandate with the importance of the International Geophysical Year. By comparison, neither the Arctic Institute in Copenhagen nor the Argentine Antarctic Institute felt any need to become polar. The creation of polar identity is ultimately a matter of geopolitics, of the value states see in instruments and symbols that speak to polar rather than Arctic or Antarctic interests. In cases such as Finland’s icebreaker industry, a technological capability justified Antarctic interest even without any national research tradition. We conclude by asking whether there is anything more natural about the polar regions than there is about the concept of a “tripolar” world in which the high alpine regions form a natural unit along with the Arctic and Antarctic.

A Comparison Study of Three Polar Grids

2008 ◽  
Vol 47 (11) ◽  
pp. 2993-3007 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
William J. Gutowski
Keyword(s):  
Data Aggregation ◽  
Velocity Potential ◽  
The Arctic ◽  
Polar Regions ◽  
Comparison Study ◽  
Summer Circulation ◽  
Meteorological Field ◽  
Northern Summer ◽  
Latitude Circle ◽  
Microwave Imager

Abstract The circumference of a latitude circle decreases toward the Poles, making it difficult to present meteorological field variables on equally spaced grids with respect to latitude and longitude because of data aggregation. To identify the best method for displaying data at the Poles, three different grids are compared that have all been designed to reduce data aggregation: the reduced latitude–longitude (RL) grid, the National Snow and Ice Data Center Equal-Area Special Sensor Microwave Imager (SSM/I) Earth (EA) grid, and the National Meteorological Center octagonal (OG) grid. The merits and disadvantages of these grids are compared in terms of depictions of the Arctic summer circulation with wind vectors, streamfunction, and velocity potential at 400 hPa where maximum westerlies are located. Using geostrophy, the 400-hPa streamfunction at high latitudes can be formed from geopotential height. In comparison with this geostrophic streamfunction, the streamfunction generated from vorticity on the OG grid shows a negligible error (∼0.5%). The error becomes larger using vorticity on the EA (∼15%) and RL (∼30%) grids. During the northern summer, the Arctic circulation at 400 hPa is characterized by three troughs. The streamfunction and velocity potential of these three troughs are spatially in quadrature with divergent (convergent) centers located ahead of (behind) these troughs. These circulation features are best depicted by the streamfunction and velocity potential generated on the OG grid. It is demonstrated by these findings that the National Meteorological Center octagonal grid is the most ideal among the three grids used for the polar regions. However, this assessment is constrained by the hemispheric perspective of meteorological field variables, because these variables depicted on the octagonal grid at higher latitudes need to be merged with those on the equal-latitude-longitude grid at lower latitudes.

scholarly journals Enhanced Viral Activity in the Surface Microlayer of the Arctic and Antarctic Oceans

2021 ◽  
Vol 9 (2) ◽  
pp. 317
Author(s):  
Dolors Vaqué ◽  
Julia A. Boras ◽  
Jesús Maria Arrieta ◽  
Susana Agustí ◽  
Carlos M. Duarte ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Food Web ◽  
Physicochemical Characteristics ◽  
The Arctic ◽  
Microbial Food Web ◽  
Surface Microlayer ◽  
Polar Regions ◽  
Nutrient Inputs ◽  
Viral Activity ◽  
The Impact

The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column.

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