Detecting Supercooled Water Clouds Using Passive Radiometer Measurements

Zhou, Ganning; Wang, Jianjie; Yin, Yan; Hu, Xiuqing; Letu, Husi; Sohn, Byung Ju; Yung, Yuk L.; Liu, Chao

doi:10.1029/2021gl096111

Cited by 12 publications

(3 citation statements)

References 25 publications

(49 reference statements)

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“…0. When aerosols are present, the ratio is positive and can be used to distinguished between predominantly liquid or ice aerosol content, and is based on previous published studies using this ratio (Miller et al, 2014;Zhou et al, 2022;Noh et al, 2019). Specifically, if the aerosol is predominantly liquid water then R tends to be larger than if the cloud were predominantly ice.…”

Section: Spectral Discriminationmentioning

confidence: 99%

Transport of the Hunga Tonga volcanic aerosols inferred from Himawari-8 limb measurements

Prata

2023

Preprint

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Abstract. The Hunga Tonga-Hunga Ha'apai (Hunga Tonga; 21.545 ºS, 178.393 ºE) volcanic eruption of 15 January 2022 produced copious amounts of aerosols that reached high into the stratosphere, exceeding 30 km and settling into layers a few kilometres deep between 22–28 km. The Advanced Himawari Imager (AHI) on board the geostationary Himawari-8 platform at 140.7 ºE was able to monitor the eruption at 10 minute intervals and 0.25 km2 to 4 km2 spatial resolution within 16 spectral channels ranging from visible to infrared wavelengths and over a latitude/longitude field of view of ~±75º. Here a new use of these data is proposed where the the limb region of of the field of view is exploited to detect aerosol layers extending vertically into the atmosphere. The analyses provide vertical profiles of scattered visible light and are compared to Caliop space lidar measurements. Hunga Tonga aerosols are detected using the ratio of near infrared reflectances at 1.61 µm and 2.25 µm, in the western limb from 22 January and in the eastern limb from 31 January 2022 up until the present time (September 2023). The average zonal velocity is estimated to be ~-25 ms-1 (westwards) and the meridional velocity to be ~0.2 ms-1 (northwards). The latitudinal spread is characterised by a gradual northerly movement of the main layer situated between 22–28 km in the first 60 days, and stagnation or slight southerly spread thereafter. The current methodology does not provide quantitative estimates of the amount or type of aerosol, but based on the spectral properties of water and ice clouds the analysis suggests there is a strong liquid water content in the aerosol layers.

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Section: Spectral Discriminationmentioning

confidence: 99%

Transport of the Hunga Tonga volcanic aerosols inferred from Himawari-8 limb measurements

Prata

2023

Preprint

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“…100% RH) would normally result in condensation, a metastable state known as supersaturation frequently occurs in the free atmosphere due to a lack of condensation nuclei [10][11][12]. Furthermore, the phenomenon of supercooling, where water vapour condenses into liquid water even at temperatures below 0 degrees Celsius, is also common in the upper-air atmosphere [13][14][15]. Consequently, meteorological RH is conventionally defined based on the saturation vapour pressure of liquid water, even at temperatures below 0 degrees Celsius [9].…”

Section: Introductionmentioning

confidence: 99%

Relative humidity measurements of a thin-film humidity sensor in condensing conditions in the temperature range from −40 °C to 5 °C

Lee,

Choi

et al. 2024

Meas. Sci. Technol.

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In condensing conditions, metastable states such as supersaturation of water vapour and supercooling of liquid water are commonly observed in the free atmosphere. This study investigates the response of a polymeric thin-film humidity sensor under condensing conditions at various temperatures (-40 °C, -20 °C, -5 °C, and 5 °C) and different relative humidity (RH) levels. To ensure precise control of RH, a saturator-based humidity generator operating in a two-temperature mode is utilized. The condensing conditions are achieved in two ways: by increasing water vapour pressure (WVP) at a fixed temperature and by decreasing the temperature while maintaining a constant WVP. In general, when measuring RH under condensing conditions, the sensor indicates a temporary supersaturation state with an RH peak exceeding 100% before the onset of condensation. Subsequently, the RH value exhibits a delayed decrease when exposed to a non-condensing RH level. The experiments with a constant WVP demonstrate a lower likelihood of ice condensation compared to those with a constant temperature. This study demonstrates the measurement capability and behaviour of thin-film humidity sensors above 100% RH in the supersaturation states that are commonly observed in the free atmosphere at meteorologically-relevant temperatures.

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“…Satellite remote sensing is an important method to determine global cloud properties [23][24][25][26]. In recent years, spaceborne active remote sensing has been widely used to retrieve vertical profiles of thermodynamic cloud phases [10,[27][28][29][30][31][32].…”

Section: Introduction 1backgroundmentioning

confidence: 99%

Cloud Top Thermodynamic Phase from Synergistic Lidar-Radar Cloud Products from Polar Orbiting Satellites: Implications for Observations from Geostationary Satellites

et al. 2023

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The cloud thermodynamic phase is a crucial parameter to understand the Earth’s radiation budget, the hydrological cycle, and atmospheric thermodynamic processes. Spaceborne active remote sensing such as the synergistic radar-lidar DARDAR product is considered the most reliable method to determine cloud phase; however, it lacks large-scale observations and high repetition rates. These can be provided by passive instruments such as SEVIRI aboard the geostationary Meteosat Second Generation (MSG) satellite, but passive remote sensing of the thermodynamic phase is challenging and confined to cloud top. Thus, it is necessary to understand to what extent passive sensors with the characteristics of SEVIRI are expected to provide a relevant contribution to cloud phase investigation. To reach this goal, we collect five years of DARDAR data to model the cloud top phase (CTP) for MSG/SEVIRI and create a SEVIRI-like CTP through an elaborate aggregation procedure. Thereby, we distinguish between ice (IC), mixed-phase (MP), supercooled (SC), and warm liquid (LQ). Overall, 65% of the resulting SEVIRI pixels are cloudy, consisting of 49% IC, 14% MP, 13% SC, and 24% LQ cloud tops. The spatial resolution has a significant effect on the occurrence of CTP, especially for MP cloud tops, which occur significantly more often at the lower SEVIRI resolution than at the higher DARDAR resolution (9%). We find that SC occurs most frequently at high southern latitudes, while MP is found mainly in both high southern and high northern latitudes. LQ dominates in the subsidence zones over the ocean, while IC occurrence dominates everywhere else. MP and SC show little seasonal variability apart from high latitudes, especially in the south. IC and LQ are affected by the shift of the Intertropical Convergence Zone. The peak of occurrence of SC is at −3 ∘C, followed by that for MP at −13 ∘C. Between 0 and −27 ∘C, the occurrence of SC and MP dominates IC, while below −27 ∘C, IC is the most frequent CTP. Finally, the occurrence of cloud top height (CTH) peaks lower over the ocean than over land, with MP, SC, and IC being undistinguishable in the tropics but with separated CTH peaks in the rest of the MSG disk. Finally, we test the ability of a state-of-the-art AI-based ice cloud detection algorithm for SEVIRI named CiPS (Cirrus Properties for SEVIRI) to detect cloud ice. We confirm previous evaluations with an ice detection probability of 77.1% and find a false alarm rate of 11.6%, of which 68% are due to misclassified cloud phases. CiPS is not sensitive to ice crystals in MP clouds and therefore not suitable for the detection of MP clouds but only for fully glaciated (i.e., IC) clouds. Our study demonstrates the need for the development of dedicated cloud phase distinction algorithms for all cloud phases (IC, LQ, MP, SC) from geostationary satellites.

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Detecting Supercooled Water Clouds Using Passive Radiometer Measurements

Cited by 12 publications

References 25 publications

Transport of the Hunga Tonga volcanic aerosols inferred from Himawari-8 limb measurements

Transport of the Hunga Tonga volcanic aerosols inferred from Himawari-8 limb measurements

Relative humidity measurements of a thin-film humidity sensor in condensing conditions in the temperature range from −40 °C to 5 °C

Cloud Top Thermodynamic Phase from Synergistic Lidar-Radar Cloud Products from Polar Orbiting Satellites: Implications for Observations from Geostationary Satellites

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