ALBERT

Description: The data set provides 3 years of almost continuous observation of water vapor in the air at 3 levels in the lowest 42 m above Dome C on the high antarctic plateau, 123° 21' E, 75° 06' S, 3233 m above sea level. Each data is an average over the previous ½ hour. The water vapor content is measured in a heated air flow to avoid that supersaturated air at ambient temperature deposits excess moisture (above 100% with respect to ice) before reaching the humidity sensor. In fact, many reports correspond to significant supersaturation (see references provided). HMP155 thermohygrometers are used, which for the hygrometer natively report relative humidity with respect to liquid water even below 0°C. This is the variable provided in the data set, along with temperature in the heated air flow and ambient temperature. There are several conversion formulae in the literature to convert to e.g. partial pressure and relative humidity with respect to ice. As there is no clear consensus on which should be preferred in the range of temperatures at Dome C, the user is left to carry our her/his own conversions.

Description: The data set provides 3 years of almost continuous observation of water vapor in the air at 3m height on the high antarctic plateau, 123° 21' E, 75° 06' S, 3233 m above sea level. Each data is an average over the previous ½ hour. The water vapor content is measured in a heated air flow to avoid that supersaturated air at ambient temperature deposits excess moisture (above 100% with respect to ice) before reaching the humidity sensor. In fact, many reports correspond to significant supersaturation (see references provided). HMP155 thermohygrometers are used, which for the hygrometer natively report relative humidity with respect to liquid water even below 0°C. This is the variable provided in the data set, along with temperature in the heated air flow and ambient temperature. There are several conversion formulae in the literature to convert to e.g. partial pressure and relative humidity with respect to ice. As there is no clear consensus on which should be preferred in the range of temperatures at Dome C, the user is left to carry our her/his own conversions.

Description: The data set provides 3 years of almost continuous observation of water vapor in the air at 42m height on the high antarctic plateau, 123° 21' E, 75° 06' S, 3233 m above sea level. Each data is an average over the previous ½ hour. The water vapor content is measured in a heated air flow to avoid that supersaturated air at ambient temperature deposits excess moisture (above 100% with respect to ice) before reaching the humidity sensor. In fact, many reports correspond to significant supersaturation (see references provided). HMP155 thermohygrometers are used, which for the hygrometer natively report relative humidity with respect to liquid water even below 0°C. This is the variable provided in the data set, along with temperature in the heated air flow and ambient temperature. There are several conversion formulae in the literature to convert to e.g. partial pressure and relative humidity with respect to ice. As there is no clear consensus on which should be preferred in the range of temperatures at Dome C, the user is left to carry our her/his own conversions.

Description: The data set provides 3 years of almost continuous observation of water vapor in the air at 18m height on the high antarctic plateau, 123° 21' E, 75° 06' S, 3233 m above sea level. Each data is an average over the previous ½ hour. The water vapor content is measured in a heated air flow to avoid that supersaturated air at ambient temperature deposits excess moisture (above 100% with respect to ice) before reaching the humidity sensor. In fact, many reports correspond to significant supersaturation (see references provided). HMP155 thermohygrometers are used, which for the hygrometer natively report relative humidity with respect to liquid water even below 0°C. This is the variable provided in the data set, along with temperature in the heated air flow and ambient temperature. There are several conversion formulae in the literature to convert to e.g. partial pressure and relative humidity with respect to ice. As there is no clear consensus on which should be preferred in the range of temperatures at Dome C, the user is left to carry our her/his own conversions.

Description: Two Antarctic snowfall climatologies produced from the version R04 of the CloudSat 2C-SNOW PROFILE product are available here. The climatologies cover the period 2007-2010 and the area between 55 and 82 °S. The snowfall rate in the file "CloudSat_2C-SNOW PROFILE_Antarctica_20072010_SRSinf4.nc" has been calculated using only the observations with a snow retrieval status lower than 4 (Wood et al., 2013, Palerme et al., 2018). For producing the file "CloudSat_2C-SNOW-PROFILE_Antarctica_20072010_SRSinf4_1binexcluded.nc", only the observations with a snow retrieval status lower than 4 in which snowfall is observed in at least two vertical bins have been taken into account (Palerme et al., 2018). In addition to the snowfall rate, the number of CloudSat orbits used to assess the mean snowfall rate is also available. The files also provide the snowfall rate uncertainty, which represents the expected uncertainties for individual snowfall rate retrievals (Wood et al., 2013, Palerme et al., 2014).

Description: Arctic snowfall climatology produced from the version R05 of the CloudSat 2C-SNOW-PROFILE product is available. It covers the 2007-2010 period over the latitudes from 58.5°N to 82°S. The monthly snowfall rates in this file have been calculated using the observations with: - a snow retrieval status lower than 3 - and a snowfall rate surface confidence 〉 1 Additionnaly, the monthly surface snowfall rate uncertainties, number of CloudSat orbits as well as number of observations are available. The number of observations over these 4 years is not sufficient to consider snowfall rates monthly (Edel et al. 2020). If one wants to obtain monthly snowfall rates, it is necessary to average multiple years.

Description: Current global warming is causing significant changes in snowfall in polar regions, directly impacting the mass balance of the ice caps. The only water supply in Antarctica, precipitation, is poorly estimated from surface measurements. The onboard cloud-profiling radar of the CloudSat satellite provided the first real opportunity to estimate precipitation at continental scale. Based on CloudSat observations, we propose to explore the vertical structure of precipitation in Antarctica over the 2007-2010 period. A first division of this dataset following a topographical approach (continent versus peripheral regions, with a 2250m topographical criterion) shows a high precipitation rate (275mm/yr at 1200meters above ground level) with low relative seasonal variation (+/-11%) over the peripheral areas. Over the plateau, the precipitation rate is low (34mm/yr at 1200m.a.g.l.) with a much larger relative seasonal variation (+/-143%). A second study that follows a geographical division highlights the average vertical structure of precipitation and temperature depending on the regions and their interactions with topography. In particular, over ice-shelves, we see a strong dependence of the distribution of precipitation on the sea-ice coverage. Finally, the relationship between precipitation and temperature is analyzed and compared with a simple analytical relationship. This study highlights that precipitation is largely dependent on the advection of air masses along the topographic slopes with an average vertical wind of 0.02m/s. This provides new diagnostics to evaluate climate models with a three-dimensional approach of the atmospheric structure of precipitation.

Description: Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual scales. Analysis of observational uncertainty and comparison to reanalysis data from ERA-5 indicate that wind speed is particularly difficult to measure at this location.

Description: Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the Eastern Antarctic plateau. In the article, we present and analyze 10 years (2010-2019) of data from 6 levels of meteorological instrumentation mounted on a 45-m tower located at Dome C, East Antarctica near the Concordia research station, producing a unique climatology of the near-surface environment. Large seasonal differences are evident in the monthly mean temperature and wind data, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer leading to near-uniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual scales. Analysis of observational uncertainty and comparison to reanalysis data from ERA-5 indicate that wind speed is particularly difficult to measure at this location.

Description: The first results of a campaign of intensive observation of precipitation in Dumont d'Urville, Antarctica, are presented. Several instruments collected data from November 2015 to February 2016 or longer, including a polarimetric radar (MXPol), a Micro Rain Radar (MRR), a weighing gauge (Pluvio2), and a Multi-Angle Snowflake Camera (MASC). These instruments collected the first ground-based measurements of precipitation in the region of Adélie Land (Terre Adélie), including precipitation microphysics. Microphysical observations during the austral summer 2015/2016 showed that, close to the ground level, aggregates are the dominant hydrometeor type, together with small ice particles (mostly originating from blowing snow), and that riming is a recurring process. Eleven percent of the measured particles were fully developed graupel, and aggregates had a mean riming degree of about 30%. Spurious precipitation in the Pluvio2 measurements in windy conditions, leading to phantom accumulations, is observed and partly removed through synergistic use of MRR data. The yearly accumulated precipitation of snow (300m above ground), obtained by means of a local conversion relation of MRR data, trained on the Pluvio2 measurement of the summer period, is estimated to be 815mm of water equivalent, with a confidence interval ranging between 739.5 and 989mm. Data obtained in previous research from satellite-borne radars, and the ERA-Interim reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) provide lower yearly totals: 655mm for ERA-Interim and 679mm for the climatological data over DDU. ERA-Interim overestimates the occurrence of low-intensity precipitation events especially in summer, but it compensates for them by underestimating the snowfall amounts carried by the most intense events. Overall, this paper provides insightful examples of the added values of precipitation monitoring in Antarctica with a synergistic use of in situ and remote sensing measurements.