scholarly journals Understanding cryogenic frost point hygrometer measurements after contamination by mixed-phase clouds

2020 ◽  
Author(s):  
Teresa Jorge ◽  
Simone Brunamonti ◽  
Yann Poltera ◽  
Frank G. Wienhold ◽  
Bei P. Luo ◽  
...  
Keyword(s):  
Water Vapour ◽  
Large Set ◽  
Pendulum Motion ◽  
Upper Troposphere ◽  
Frost Point ◽  
Depth Analysis ◽  
Air Chemistry ◽  
Computational Fluid Dynamics Cfd ◽  
Mixed Phase Clouds ◽  
Stratospheric Water Vapour

Abstract. Balloon-borne water vapour measurements in the (sub)tropical upper troposphere and lower stratosphere (UTLS) by means of frost point hygrometers provide important information on air chemistry and climate. However, the risk of contamination from sublimating hydrometeors collected by the intake tube may render these measurements difficult, particularly after crossing low clouds containing supercooled droplets. A large set of measurements during the 2016–2017 StratoClim balloon campaigns at the southern slopes of the Himalayas allows us to perform an in-depth analysis of this type of contamination. We investigate the efficiency of wall-contact and freezing of supercooled droplets in the intake tube and the subsequent sublimation in the UTLS using Computational Fluid Dynamics (CFD). We find that the airflow can enter the intake tube with impingement angles up to 60°, owing to the pendulum motion of the payload. Supercooled droplets with radii > 70 μm, as they frequently occur in mid-tropospheric clouds, typically undergo contact freezing when entering the intake tube, whereas only about 50 % of droplets with 10 μm radius freeze, and droplets  100 ppmv) in the stratosphere. Furthermore, we use CFD to differentiate between stratospheric water vapour contamination by an icy intake tube and contamination caused by outgassing from the balloon and payload, revealing that the latter starts playing a role only at high altitudes (p 

scholarly journals Understanding balloon-borne frost point hygrometer measurements after contamination by mixed-phase clouds

2021 ◽  
Vol 14 (1) ◽  
pp. 239-268
Author(s):  
Teresa Jorge ◽  
Simone Brunamonti ◽  
Yann Poltera ◽  
Frank G. Wienhold ◽  
Bei P. Luo ◽  
...  
Keyword(s):  
Water Vapour ◽  
High Water ◽  
Large Set ◽  
Mixing Ratios ◽  
Frost Point ◽  
Depth Analysis ◽  
Air Chemistry ◽  
Computational Fluid Dynamics Cfd ◽  
Impact Angles ◽  
Mixed Phase Clouds

Abstract. Balloon-borne water vapour measurements in the upper troposphere and lower stratosphere (UTLS) by means of frost point hygrometers provide important information on air chemistry and climate. However, the risk of contamination from sublimating hydrometeors collected by the intake tube may render these measurements unusable, particularly after crossing low clouds containing supercooled droplets. A large set of (sub)tropical measurements during the 2016–2017 StratoClim balloon campaigns at the southern slopes of the Himalayas allows us to perform an in-depth analysis of this type of contamination. We investigate the efficiency of wall contact and freezing of supercooled droplets in the intake tube and the subsequent sublimation in the UTLS using computational fluid dynamics (CFD). We find that the airflow can enter the intake tube with impact angles up to 60∘, owing to the pendulum motion of the payload. Supercooled droplets with radii > 70 µm, as they frequently occur in mid-tropospheric clouds, typically undergo contact freezing when entering the intake tube, whereas only about 50 % of droplets with 10 µm radius freeze, and droplets < 5 µm radius mostly avoid contact. According to CFD, sublimation of water from an icy intake can account for the occasionally observed unrealistically high water vapour mixing ratios (χH2O > 100 ppmv) in the stratosphere. Furthermore, we use CFD to differentiate between stratospheric water vapour contamination by an icy intake tube and contamination caused by outgassing from the balloon and payload, revealing that the latter starts playing a role only during ascent at high altitudes (p < 20 hPa).

scholarly journals Annual cycle of water vapour in the lower stratosphere over the Indian Peninsula derived from Cryogenic Frost-point Hygrometer observations

2018 ◽  
Author(s):  
Maria Emmanuel ◽  
Sukumarapillai V. Sunilkumar ◽  
Muhsin Muhammed ◽  
Buduru Suneel Kumar ◽  
Nagendra Neerudu ◽  
...  
Keyword(s):  
Water Vapour ◽  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Deep Convection ◽  
Equatorial Station ◽  
Post Monsoon ◽  
Frost Point ◽  
Stratospheric Water Vapour

Abstract. In situ measurements of lower stratospheric water vapour employing Cryogenic Frost point Hygrometer (CFH) over two tropical stations, Trivandrum (8.53 °N, 76.87 °E) and Hyderabad (17.47 °N, 78.58 °E) over the Indian subcontinent are conducted as part of Tropical Tropopause Dynamics (TTD) monthly campaigns under GARNETS program. The annual variation of lower stratosphere (LS) water vapour clearly depicts the so called tape recorder effect at both the stations. The ascent rate of water vapour compares well with the velocity of Brewer-Dobson circulation and is slightly higher over the equatorial station when compared to the off-equatorial station. The column integrated water vapour in the LS varies in the range 1.5 to 4 g/m2 with low values during winter and high values during summer monsoon and post monsoon seasons and its variability shows the signatures of local dynamics. The variation in water vapour mixing ratio (WVMR) at the cold point tropopause (CPT) exactly follows the variation in CPT temperature. The difference in WVMR between the stations shows a semi-annual variability in the altitude region 18–20 km region with high values of WVMR during summer monsoon and winter over Hyderabad and during pre-monsoon and post-monsoon over Trivandrum. This difference is related to the influence of the variations in local CPT temperature and deep convection. The monsoon dynamics has a significant role in stratospheric water vapour distribution in summer monsoon season.

scholarly journals Stratospheric water vapour as tracer for vortex filamentation in the Arctic winter 2002/2003

2003 ◽  
Vol 3 (4) ◽  
pp. 4393-4410 ◽  
Author(s):  
M. Müller ◽  
R. Neuber ◽  
F. Fierli ◽  
A. Hauchecorne ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapour ◽  
Large Scale ◽  
Polar Vortex ◽  
The Arctic ◽  
Edge Region ◽  
Mixing Ratio ◽  
Particle Sedimentation ◽  
Frost Point ◽  
Contour Advection ◽  
Stratospheric Water Vapour

Abstract. During winter 2002/2003, three balloon-borne frost point hygrometers measured high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen. All measurements reveal a high H2O mixing ratio of about 7 ppmv above 24 km, thus differing significantly from the 5 ppmv that are commonly assumed for the calculation of polar stratospheric cloud existence temperatures. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. Unlike the earlier profiles, the water vapour sounding on 11 February 2003 detected the vortex edge region in the lower part of the stratosphere. Here, a striking diminuition in H2O mixing ratio stands out between 16 and 19 km. The according stratospheric temperatures clarify that this dehydration can not be caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. On the same day, ozone observations by lidar indicate a large scale movement of the polar vortex, while an ozone sonde measurement even shows laminae in the same altitude range as in the water vapour profile. Tracer lamination in the vortex edge region is caused by filamentation of the vortex. The link between the observed water vapour diminuition and filaments in the vortex edge region is highlighted by results of the MIMOSA contour advection model. In the altitude of interest, adjoined filaments of polar and mid-latitudinal air can be identified above the Spitsbergen region. A vertical cross-section reveals that the water vapour sonde has flown through polar air in the lowest part of the stratosphere. Where the low water vapour mixing ratio was detected, the balloon passed through air from a mid-latitudinal filament from about 425 to 445 K, before it finally entered the polar vortex above 450 K. The MIMOSA model results elucidate the correlation that on 11 February 2003 the frost point hygrometer measured strongly variable water vapour concentrations as the sonde detected air with different origins, respectively. Instead of being linked to dehydration due to PSC particle sedimentation, the local diminuition in the stratospheric water vapour profile of 11 February 2003 has been found to be caused by dynamical processes in the polar stratosphere.

scholarly journals Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS

2008 ◽  
Vol 8 (1) ◽  
pp. 1635-1671 ◽  
Author(s):  
S. C. Müller ◽  
N. Kämpfer ◽  
D. G. Feist ◽  
A. Haefele ◽  
M. Milz ◽  
...  
Keyword(s):  
Water Vapour ◽  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Horizontal Resolution ◽  
Polar Regions ◽  
Upper Troposphere ◽  
Vertical Range ◽  
Stratospheric Water Vapour

Abstract. We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 3–20%, when compared to satellite experiments. A good agreement with a difference of 3.3% was found between AMSOS and in-situ hygrosondes FISH and FLASH and an excellent matching of the lidar measurements from the DIAL instrument in the short overlap region in the upper troposphere.

scholarly journals Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS

2008 ◽  
Vol 8 (12) ◽  
pp. 3169-3183 ◽  
Author(s):  
S. C. Müller ◽  
N. Kämpfer ◽  
D. G. Feist ◽  
A. Haefele ◽  
M. Milz ◽  
...  
Keyword(s):  
Water Vapour ◽  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Horizontal Resolution ◽  
Polar Regions ◽  
Upper Troposphere ◽  
Vertical Range ◽  
Stratospheric Water Vapour

Abstract. We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 0 to –20%, when compared to satellite experiments. Also a comparison between AMSOS and in-situ hygrosondes FISH and FLASH have been performed. A matching in the short overlap region in the upper troposphere of the lidar measurements from the DIAL instrument and the AMSOS dataset allowed water vapour profiling from the middle troposphere up to the mesosphere.

scholarly journals Stratospheric water vapour as tracer for Vortex filamentation in the Arctic winter 2002/2003

2003 ◽  
Vol 3 (6) ◽  
pp. 1991-1997 ◽  
Author(s):  
M. Müller ◽  
R. Neuber ◽  
F. Fierli ◽  
A. Hauchecorne ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapour ◽  
Large Scale ◽  
Polar Vortex ◽  
The Arctic ◽  
Edge Region ◽  
Particle Sedimentation ◽  
Frost Point ◽  
Lagrangian Advection ◽  
Stratospheric Clouds ◽  
Stratospheric Water Vapour

Abstract. Balloon-borne frost point hygrometers measured three high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen during winter 2002/2003. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. The water vapour sounding on 11 February 2003 was obtained within the vortex edge region of the lower stratosphere. Here, a significant reduction of water vapour mixing ratio was observed between 16 and 19 km. The stratospheric temperatures indicate that this dehydration was not caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. Ozone observations on this day indicate a large scale movement of the polar vortex and show laminae in the same altitude range as the water vapour profile. The link between the observed water vapour reduction and filaments in the vortex edge region is indicated in the results of the semi-lagrangian advection model MIMOSA, which show that adjacent filaments of polar and mid latitude air can be identified above the Spitsbergen region. A vertical cross-section produced by the MIMOSA model reveals that the water vapour sonde flew through polar air in the lowest part of the stratosphere below 425 K, then passed through filaments of mid latitude air with lower water vapour concentrations, before it finally entered the polar vortex above 450 K. These results indicate that on 11 February 2003 the frost point hygrometer measured different water vapour concentrations as the sonde detected air with different origins. Instead of being linked to dehydration due to PSC particle sedimentation, the local reduction in the stratospheric water vapour profile was in this case caused by dynamical processes in the polar stratosphere.

scholarly journals Quantification of water vapour transport from the Asian monsoon to the stratosphere

2019 ◽  
Vol 19 (13) ◽  
pp. 8947-8966 ◽  
Author(s):  
Matthias Nützel ◽  
Aurélien Podglajen ◽  
Hella Garny ◽  
Felix Ploeger
Keyword(s):  
Mass Transport ◽  
Water Vapour ◽  
Asian Monsoon ◽  
Lagrangian Model ◽  
Vapour Transport ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Upper Troposphere ◽  
Water Vapour Transport ◽  
Stratospheric Water Vapour

Abstract. Numerous studies have presented evidence that the Asian summer monsoon anticyclone substantially influences the distribution of trace gases – including water vapour – in the upper troposphere and lower stratosphere (e.g. Santee et al., 2017). Stratospheric water vapour in turn strongly affects surface climate (see e.g. Solomon et al., 2010). Here, we analyse the characteristics of water vapour transport from the upper troposphere in the Asian monsoon region to the stratosphere employing a multiannual simulation with the chemistry-transport model CLaMS (Chemical Lagrangian Model of the Stratosphere). This simulation is driven by meteorological data from ERA-Interim and features a water vapour tagging that allows us to assess the contributions of different upper tropospheric source regions to the stratospheric water vapour budget. Our results complement the analysis of air mass transport through the Asian monsoon anticyclone by Ploeger et al. (2017). The results show that the transport characteristics for water vapour are mainly determined by the bulk mass transport from the Asian monsoon region. Further, we find that, although the relative contribution from the Asian monsoon region to water vapour in the deep tropics is rather small (average peak contribution of 14 % at 450 K), the Asian monsoon region is very efficient in transporting water vapour to this region (when judged according to its comparatively small spatial extent). With respect to the Northern Hemisphere extratropics, the Asian monsoon region is much more impactful and efficient regarding water vapour transport than e.g. the North American monsoon region (averaged maximum contributions at 400 K of 29 % versus 6.4 %).

scholarly journals Quantification of water vapour transport from the Asian monsoon to the stratosphere

2019 ◽  
Author(s):  
Matthias Nützel ◽  
Aurelien Podglajen ◽  
Hella Garny ◽  
Felix Ploeger
Keyword(s):  
Mass Transport ◽  
Water Vapour ◽  
Asian Monsoon ◽  
Lagrangian Model ◽  
Vapour Transport ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Upper Troposphere ◽  
Water Vapour Transport ◽  
Stratospheric Water Vapour

Abstract. Numerous studies have presented evidence that the Asian summer monsoon anticyclone substantially influences the distribution of trace gases – including water vapour – in the upper troposphere and lower stratosphere (e.g. Santee et al., 2017). Stratospheric water vapour in turn, is strongly affecting surface climate (cf. e.g. Solomon et al., 2010). Here, we analyse the characteristics of water vapour transport from the upper troposphere in the Asian monsoon region to the stratosphere employing a multiannual simulation with the chemistry-transport model CLaMS (Chemical Lagrangian Model of the Stratosphere). This simulation is driven by meteorological data from ERA-Interim and features a water vapour tagging that allows us to assess the contributions of different upper tropospheric source regions to the stratospheric water vapour budget. Our results complement the analysis of air mass transport through the Asian monsoon anticyclone by Ploeger et al. (2017). The results show that the transport characteristics for water vapour are mainly determined by the bulk mass transport from the Asian monsoon region. Further, we find that, although the relative contribution from the Asian monsoon region to water vapour in the deep tropics is rather small (average peak contribution of 14 % at 450 K), the Asian monsoon region is very efficient in transporting water vapour to this region (when judged according to its comparatively small spatial extent). With respect to the Northern Hemisphere extratropics, the Asian monsoon region is much more impactful and efficient regarding water vapour transport than e.g. the North American monsoon region (averaged maximum contributions at 400 K of 29 % vs. 6.4 %).

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