Understanding balloon-borne frost point hygrometer measurements after contamination by mixed-phase clouds
نویسندگان
چکیده
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 climate. However, risk contamination from sublimating hydrometeors collected intake tube may render these unusable, particularly after crossing low clouds containing supercooled droplets. A large set (sub)tropical during 2016–2017 StratoClim balloon campaigns at southern slopes Himalayas allows us to perform an in-depth analysis this type contamination. We investigate efficiency wall contact freezing droplets subsequent sublimation UTLS using computational fluid dynamics (CFD). find that airflow can enter with impact angles up 60∘, owing pendulum motion payload. Supercooled radii > 70 µm, as they frequently occur mid-tropospheric clouds, typically undergo when entering tube, whereas only about 50 % 10 µm radius freeze, < 5 mostly avoid contact. According CFD, icy account for occasionally observed unrealistically high mixing ratios (χH2O 100 ppmv) stratosphere. Furthermore, we use CFD differentiate between stratospheric caused outgassing payload, revealing latter starts playing a role ascent altitudes (p 20 hPa).
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ژورنال
عنوان ژورنال: Atmospheric Measurement Techniques
سال: 2021
ISSN: ['1867-1381', '1867-8548']
DOI: https://doi.org/10.5194/amt-14-239-2021