Seasonal Variations of the Relative Optical Air Mass Function for Background Aerosol and Thin Cirrus Clouds at Arctic and Antarctic Sites

Tomasi, Claudio; Petkov, Boyan; Mazzola, Mauro; Ritter, Christoph; Sarra, Alcide di; Iorio, Tatiana Di; Guasta, Massimo Del

doi:10.3390/rs70607157

Cited by 8 publications

(4 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note that when the sondes reached the ground In general, all the flights reached a top height above 10 km (Figure 4 and Figures S7-14), namely well above the tropopause height (about 7-8 km). This is consistent with previous observations made with meteorological operational Vaisala PTU sondes (Tomasi et al, 2015). The vertical distributions of f, ⁄ and SLWC associated with the flights L03 and L04 are shown in Figures 6 and 7, respectively.…”

Section: Launches On 25 December 2021supporting

confidence: 91%

In situ observations of supercooled liquid water clouds over Dome C, Antarctica by balloon-borne sondes

Ricaud,

Durand,

Grigioni

et al. 2024

Preprint

View full text Add to dashboard Cite

Abstract. Clouds in Antarctica are key elements that affect radiative forcing and thus Antarctic climate evolution. Although the vast majority of clouds are composed of ice crystals, a non-negligible fraction is constituted of supercooled liquid water (SLW, water held in liquid form below 0 °C). Numerical weather prediction models have a great difficulty to forecast SLW clouds over Antarctica favouring ice at the expense of liquid water, and therefore incorrectly estimating the cloud radiative forcing. Remote sensing observations of SLW clouds have been carried out for several years at Concordia station (75° S, 123° E, 3233 m above mean sea level), combining active LIDAR measurements (SLW cloud detection) and passive HAMSTRAD microwave measurements (liquid water path, LWP). The present project aimed at in situ observations of SLW clouds using sondes developed by the company Anasphere, specifically designed for SLW content (SLWC) measurements. These SLWC sondes were coupled to standard meteorological pressure-temperature-humidity sondes from the Vaisala Company and released under meteorological balloons. During the 2021–2022 summer campaign, 15 launches were made, of which 7 were scientifically exploitable. Above a height of 400 m above ground level, we found that the SLWC sondes detected SLW clouds in a vertical range consistent with LIDAR observations. In nominal operation, the LWP values obtained either by HAMSTRAD or vertically-integrated from the SLWC sonde profiles were consistent in spite of their low values (< 10 g m-2). On some occasions far from nominal operation (surface fog, low vertical ascent of the balloon), the LWPs from the SLWC sonde were overestimated by a factor of 5–10 compared to the HAMSTRAD values. In general, the SLW clouds were observed in a layer close to saturation (U > 80 %) or saturated (U ~100–105 %) just below or at the lowermost part of the entrainment zone or capping inversion zone which exists at the top of the Planetary Boundary Layer and is characterized by an inflection point in the potential temperature vertical profiles. Our results are consistent with the theoretical view that SLW clouds form and pertain at the top of the Planetary Boundary Layer.

show abstract

Section: Launches On 25 December 2021supporting

confidence: 91%

In situ observations of supercooled liquid water clouds over Dome C, Antarctica by balloon-borne sondes

Ricaud,

Durand,

Grigioni

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

“…Orbiting at 705 km altitude, the CALIPSO mini-satellite has been observing clouds and aerosols since 2006 to better understand the role of clouds and aerosols in climate. To ac-complish this mission, the CALIPSO satellite is equipped with a lidar, a camera, and an infrared imager (Winker et al, 2009). CALIOP is a dual-wavelength (532 and 1064 nm) backscatter lidar.…”

Section: Caliop On Board Calipsomentioning

confidence: 99%

“…2. the tropospheric depolarization lidar (Tomasi et al, 2015) to obtain vertical profiles of backscattering and depolarization ratio.…”

Section: Introductionmentioning

confidence: 99%

Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica

Ricaud

Guasta²,

Bazile

et al. 2020

Atmos. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

Abstract. A comprehensive analysis of the water budget over the Dome C (Concordia, Antarctica) station has been performed during the austral summer 2018–2019 as part of the Year of Polar Prediction (YOPP) international campaign. Thin (∼100 m deep) supercooled liquid water (SLW) clouds have been detected and analysed using remotely sensed observations at the station (tropospheric depolarization lidar, the H2O Antarctica Microwave Stratospheric and Tropospheric Radiometer (HAMSTRAD), net surface radiation from the Baseline Surface Radiation Network (BSRN)), radiosondes, and satellite observations (CALIOP, Cloud-Aerosol LIdar with Orthogonal Polarization/CALIPSO, Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) combined with a specific configuration of the numerical weather prediction model: ARPEGE-SH (Action de Recherche Petite Echelle Grande Echelle – Southern Hemisphere). The analysis shows that SLW clouds were present from November to March, with the greatest frequency occurring in December and January when ∼50 % of the days in summer time exhibited SLW clouds for at least 1 h. Two case studies are used to illustrate this phenomenon. On 24 December 2018, the atmospheric planetary boundary layer (PBL) evolved following a typical diurnal variation, which is to say with a warm and dry mixing layer at local noon thicker than the cold and dry stable layer at local midnight. Our study showed that the SLW clouds were observed at Dome C within the entrainment and the capping inversion zones at the top of the PBL. ARPEGE-SH was not able to correctly estimate the ratio between liquid and solid water inside the clouds with the liquid water path (LWP) strongly underestimated by a factor of 1000 compared to observations. The lack of simulated SLW in the model impacted the net surface radiation that was 20–30 W m−2 higher in the BSRN observations than in the ARPEGE-SH calculations, mainly attributable to the BSRN longwave downward surface radiation being 50 W m−2 greater than that of ARPEGE-SH. The second case study took place on 20 December 2018, when a warm and wet episode impacted the PBL with no clear diurnal cycle of the PBL top. SLW cloud appearance within the entrainment and capping inversion zones coincided with the warm and wet event. The amount of liquid water measured by HAMSTRAD was ∼20 times greater in this perturbed PBL than in the typical PBL. Since ARPEGE-SH was not able to accurately reproduce these SLW clouds, the discrepancy between the observed and calculated net surface radiation was even greater than in the typical PBL case, reaching +50 W m−2, mainly attributable to the downwelling longwave surface radiation from BSRN being 100 W m−2 greater than that of ARPEGE-SH. The model was then run with a new partition function favouring liquid water for temperatures below −20 down to −40 ∘C. In this test mode, ARPEGE-SH has been able to generate SLW clouds with modelled LWP and net surface radiation consistent with observations during the typical case, whereas, during the perturbed case, the modelled LWP was 10 times less than the observations and the modelled net surface radiation remained lower than the observations by ∼50 W m−2. Accurately modelling the presence of SLW clouds appears crucial to correctly simulate the surface energy budget over the Antarctic Plateau.

show abstract

“…There are three main instruments relevant to this study that have been routinely running for about 10 years: 1) The H2O Antarctica Microwave Stratospheric and Tropospheric Radiometer (HAMSTRAD, Ricaud et al, 2010a) to obtain vertical profiles of temperature and water vapour, as well as the LWP. 2) The tropospheric depolarization LIDAR (Tomasi et al, 2015) to obtain vertical profiles of backscatter and depolarization to be used for the downward and upward SRs, can be computed (Driemel et al, 2018) as:…”

Section: Introductionmentioning

confidence: 99%

Supercooled liquid water clouds observed over Dome C, Antarctica: temperature sensitivity and surface radiation impact

Ricaud

Guasta²,

Lupi

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Clouds affect the Earth climate with an impact that depends on the cloud nature (solid/ liquid water). Although the Antarctic climate is changing rapidly, cloud observations are sparse over Antarctica due to few ground stations and satellite observations. The Concordia station is located on the East Antarctic Plateau (75° S, 123° E, 3233 m above mean sea level), one of the driest and coldest places on Earth. We used observations of clouds, temperature, liquid water and surface radiation performed at Concordia during 4 austral summers (December 2018–2021) to analyze the link between liquid water and temperature and its impact on surface radiation in the presence of supercooled liquid water (liquid water for temperature less than 0 °C) clouds (SLWCs). Our analysis shows that, within SLWCs, temperature logarithmically increases from -36.0 °C to -16.0 °C when liquid water path increases from 1.0 to 14.0 g m-2, and SLWCs positively impact the net surface radiation, which logarithmically increases by 0.0 to 50.0 W m-2 when liquid water path increases from 1.7 to 3.0 g m-2. We finally estimate that SLWCs have a great potential radiative impact over Antarctica whatever the season considered, up to 5.0 W m-2 over the Eastern Antarctic Plateau and up to 30 W m-2 over the Antarctic Peninsula in summer.

show abstract

Seasonal Variations of the Relative Optical Air Mass Function for Background Aerosol and Thin Cirrus Clouds at Arctic and Antarctic Sites

Cited by 8 publications

References 26 publications

In situ observations of supercooled liquid water clouds over Dome C, Antarctica by balloon-borne sondes

In situ observations of supercooled liquid water clouds over Dome C, Antarctica by balloon-borne sondes

Supercooled liquid water cloud observed, analysed, and modelled at the top of the planetary boundary layer above Dome C, Antarctica

Supercooled liquid water clouds observed over Dome C, Antarctica: temperature sensitivity and surface radiation impact

Contact Info

Product

Resources

About