- Titel
- Airborne Observations of Riming in Arctic Mixed-phase Clouds
- Zitierfähige Url:
- https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-950095
- Datum der Einreichung
- 14.06.2024
- Datum der Verteidigung
- 05.11.2024
- Abstract (EN)
- Mixed-phase clouds (MPCs) are a key component of the Arctic climate system by contributing to surface warming. The representation of MPC processes in climate models is currently incomplete, leading to high uncertainties in the prediction of future climate change. One such MPC process is riming, which describes the freezing of liquid droplets on ice particles upon contact. The occurrence and drivers of riming are poorly understood, particularly in the Arctic. This dissertation aims at gaining a better understanding of riming in the Arctic and its influence on ice water variability in MPCs. A novel framework to consistently estimate physical and scattering properties of rimed ice particles is presented. Two methods for quantifying riming have been developed and applied to airborne cloud radar and in situ measurements. Spatial scales of ice clustering in Arctic MPCs and their relation to riming were analyzed and compared to mid-latitude MPCs. First, mass-size, cross-sectional area-size, and backscattering cross-section relations were developed as a function of the normalized rime mass M for simulated rimed aggregates. The proposed framework (“riming-dependent parameterization”) allows to consistently simulate scattering properties of rimed aggregated ice particles. For radar frequencies of 35.6 GHz and 94.0 GHz, the resulting biases are less than 1 dB assuming exponential particle size distributions when using the particle masses and scattering properties of the individual simulated particles as a reference. Further, two methods for quantifying ice particle riming are presented. The first method is based on an inverse Optimal Estimation algorithm to retrieve M from cloud radar and in situ measurements ('combined method'). The second method relies on in situ observations only, relating M to optical particle shape measurements ('in situ method'). The methods were applied to data obtained during the HALO-(AC)³ aircraft campaign, which took place west of Svalbard in spring 2022. Median M values of 0.024 and 0.021 (mean values of 0.035 and 0.033) were derived using the combined and in situ method, respectively. Compared to other temperatures, the least amount of riming occurred at − 15°C. Rimed particles were observed at low liquid water path conditions. Finally, the influence of riming on the spatial variability of ice water content (IWC) was investigated. The analysis of HALO-(AC)³ data was extended to data collected during the IMPACTS aircraft campaign, which focused on mid-latitude winter storms. Riming accounted for 66% and 63% of the total IWC during IMPACTS and HALO-(AC)³, respectively. Riming increased the probability of ice cluster occurrence at similar scales as liquid water content variability. In cold air outbreak MPCs observed during HALO-(AC)³, riming led to additional IWC clustering at spatial scales of 3-5 km, which could be lined to the presence of mesoscale updraft features. These results help to improve our understanding of riming and the link between riming and IWC variability, and can be used to evaluate and constrain models of MPCs.
- Verweis
- A riming-dependent parameterization of scattering by snowflakes using the self-similar Rayleigh-Gans approximation
Erstautorenstudie, die in der Dissertation zitiert wird
Link: https://doi.org/10.1002/qj.4573
DOI: https://doi.org/10.1002/qj.4573 - Quantifying riming from airborne data during the HALO-(AC)³ campaign
Erstautorenstudie, die in der Dissertation zitiert wird
Link: https://doi.org/10.5194/amt-17-1475-2024
DOI: https://doi.org/10.5194/amt-17-1475-2024 - How does riming influence the observed spatial variability of ice water in mixed-phase clouds?
Erstautorenstudie (preprint), die in der Dissertation zitiert wird
Link: https://doi.org/10.5194/egusphere-2024-1214
DOI: https://doi.org/10.5194/egusphere-2024-1214 - Freie Schlagwörter (EN)
- Riming, Arctic, Mixed-phase Clouds, Ice crystals, Airborne
- Klassifikation (DDC)
- 530
- Den akademischen Grad verleihende / prüfende Institution
- Universität Leipzig, Leipzig
- Version / Begutachtungsstatus
- publizierte Version / Verlagsversion
- URN Qucosa
- urn:nbn:de:bsz:15-qucosa2-950095
- Veröffentlichungsdatum Qucosa
- 03.01.2025
- Dokumenttyp
- Dissertation
- Sprache des Dokumentes
- Englisch
- Lizenz / Rechtehinweis
CC BY 4.0