Impact of Assimilating Adaptively Thinned AIRS Cloud-Cleared Radiances on the Analysis of Polar Lows and Mediterranean Sea Tropical-Like Cyclone in a Global Modeling and Data Assimilation Framework

• Published in: Weather and forecasting Vol. 37; no. 7; pp. 1117 - 1134
• Main Authors: Ganeshan, Manisha, Reale, Oreste, McGrath-Spangler, Erica, Boukachaba, Niama
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center American Meteorological Society 01.07.2022
• Subjects: Analysis; Atmospheric Infrared Sounder; Atmospheric models; Cyclogenesis; Cyclones; Data assimilation; Data collection; Density; Earth Observing System (EOS); Experiments; Geosciences (General); Hurricanes; Impact analysis; Infrared analysis; Mesoscale phenomena; Methods; Modelling; Polar lows; Radiance; Representations; Storms; Thinning; Tropical climate; Tropical cyclones; Tropical environments; Velocity; Velocity gradient; Velocity gradients; Mediterranean Sea; Global Modeling; Tropical Cyclones (tcs)
• ISSN: 0882-8156; 1520-0434
• DOI: 10.1175/WAF-D-21-0068.1

Polar lows, and mesoscale convective cyclones bearing resemblance to tropical cyclones but originating outside of the tropics, are storms that are challenging to represent accurately in global analyses and models because of their small size, rapid growth at subsynoptic scales, occurrence in data poor oceanic regions, and difficulties in objectively validating them in analysis. Building on previous positive results obtained with respect to the representation of tropical cyclones (TCs) in a global model, a set of observing system experiments (OSEs) performed using the NASA Goddard Earth Observing System (GEOS, version 5) are investigated, focusing on three case studies—a polar low in the Sea of Okhotsk, a polar low in the Southern Ocean, and a Mediterranean Sea tropical-like cyclone that occurred during the boreal fall season of 2014. Experiments assimilating adaptively thinned cloud-cleared hyperspectral infrared radiances from the Atmospheric Infrared Sounder (AIRS) instrument on board the NASA Aqua satellite, with higher density in the vicinity of each storm and its pre-cyclogenesis environment, and lower density elsewhere, demonstrate a positive impact on the analyzed representation of each storm. The adaptive thinning experiments improve the storm intensity and structure, including vertical alignment, depth, symmetry, strength, and compactness of warm core compared to the reference experiments. The results suggest that jet-level processes associated with extremely strong horizontal velocity gradients as represented in the model analysis can be useful to locate dynamically active regions of the extratropical atmosphere where denser data coverage is likely to improve the analyzed representation of polar lows and other similar marine mesoscale convective cyclones.