[1] The multiyear lidar and radar measurements obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat between June 2006 and May 2010 were used to investigate the seasonal and interannual variabilities of the vertical and horizontal cloud distributions, cloud top height above ground (H top ) thickness (CTH), effective radius (r e ), and ice water content (IWC) over the southern high latitudes poleward of 60°S. The collocated lidar and radar data were used to derive the cloud mask, which was used to classify the clouds into four classes according to the cloud base height above ground (H base ) and CTH. The Amundsen/Bellingshausen Sea region showed the highest cloud occurrence (>80%) and Antarctic Plateau had lowest cloud occurrence (<30%). The low-level clouds accounted for more than 60% of the total cloudiness, and their occurrence was greater during summer than during winter, but deep and high-level cloud occurrence, CTH, and H top were greater during winter than during summer. CTH and H top of deep and high-level clouds were greater over ocean than over land, but both CTH and H top of low-level clouds were greater over land than over ocean. The mean IWCs for high-level clouds over land and ocean were 0.85 (2.0) and 1.3 (3.1) mg/kg, respectively, and the mean r e over land and ocean were 18.0 (22.1) and 21.5 (26.4) mm, respectively, for winter (summer). The study provides a high-quality data set of cloud properties over the Antarctic region to improve our understanding and model simulations of Antarctic clouds.
A COSMIC-1/FORMOSAT-3 (Constellation Observing System for Meteorology, Ionosphere, and Climate-1 and Formosa Satellite Mission 3) follow-on mission, COSMIC-2/FORMOSAT-7, had been successfully launched into low-inclination orbits on 25 June 2019. COSMIC-2 has a significantly increased Signal-to-Noise ratio (SNR) compared to other Radio Occultation (RO) missions. This study summarized the initial assessment of COSMIC-2 data quality conducted by the NOAA (National Oceanic and Atmospheric Administration) Center for Satellite Applications and Research (STAR). We use validated data from other RO missions to quantify the stability of COSMIC-2. In addition, we use the Vaisala RS41 radiosonde observations to assess the accuracy and uncertainty of the COSMIC-2 neutral atmospheric profiles. RS41 is currently the most accurate radiosonde observation system. The COSMIC-2 SNR ranges from 200 v/v to about 2800 v/v. To see if the high SNR COSMIC-2 signals lead to better retrieval results, we separate the COSMIC-2–RS41 comparisons into different SNR groups (i.e., 0–500 v/v group, 500–1000 v/v group, 1000–1500 v/v group, 1500–2000 v/v group, and >2000 v/v group). In general, the COSMIC-2 data quality in terms of stability, precision, accuracy, and uncertainty of the accuracy is very compatible with those from COSMIC-1. Results show that the mean COSMIC-2–RS41 water vapor difference from surface to 5 km altitude for each SNR groups are equal to −1.34 g/kg (0–500 v/v), −1.17 g/kg (500–1000 v/v), −1.33 g/kg (1000–1500 v/v), −0.93 g/kg (1500–2000 v/v), and −1.52 g/kg (>2000 v/v). Except for the >2000 v/v group, the high SNR measurements from COSMIC-2 seem to improve the mean water vapor difference for the higher SNR group slightly (especially for the 1500–2000 v/v group) comparing with those from lower SNR groups.
[1] The formation of polar stratospheric clouds (PSCs) is critical to the development of polar ozone loss. However, the mechanisms of PSC formation remain poorly understood, which affects ozone loss models. Here, based on observations by the NASA A-train satellites, we show that 66% ± 16% and 52% ± 17% of PSCs over west and east Antarctica during the period June -October 2006 were associated with deep tropospheric cloud systems, with maximum depths exceeding 7 km. The development of such deep tropospheric cloud systems should cool the lower stratosphere through adiabatic and radiative processes, favoring PSC development. These deep systems also transport lower tropospheric air into the upper troposphere and lower stratosphere. These new findings suggest that Antarctic PSC formation is closely connected to tropospheric meteorology and thus governed by synoptic scale dynamics, local topography, and large-scale circulation. More dedicated studies are still needed to better understand Antarctic PSC formation. Citation: Wang,
[1] Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat satellite measurements are used to investigate the impact of tropospheric high and deep clouds on the microphysical properties of polar stratospheric clouds (PSCs) over Antarctica during the 2006 and 2007 winters. Based on the attenuated lidar scattering ratio and PSC depolarization ratio (d′), PSCs are classified into supercooled ternary solution (STS), Mix 1, Mix 2, and ice classes with significantly different microphysical properties in terms of the PSC backscattering coefficient (b 532 ) for 532 nm, the color ratio (b 1064 /b 532 ), and d′. In the early stages of the PSC season, STS accounts for more than 50% of the total PSCs, but the Mix 1, Mix 2, and ice classes become more common in the late season. During the late PSC season, close to 70% of PSCs are formed in association with high and deep tropospheric cloud systems, indicating the important role of tropospheric weather systems in Antarctic PSC formation. Tropospheric cloud systems also affect the microphysical properties of PSCs by affecting the relative occurrence of different PSC classes, especially during September and October. Our results also show that there are noticeable differences in color ratio and b 532 (at the 0.05 significance level) for the ice class and Mix 2 (late season only) for PSCs associated and not associated with high and deep tropospheric cloud systems. These results indicate that the impact of tropospheric meteorology on PSC formation should be fully considered to better understand interannual variations and recovery of the Antarctic ozone hole.
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