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Tan, Ivy

Publications and source records attributed to Tan, Ivy.

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Determining Cloud Thermodynamic Phase from Micropulse Lidar Network Data

Determining cloud thermodynamic phase is a critical factor in studies of Earth's radiation budget. Here we use observations from the NASA Micro Pulse Lidar Network (MPLNET) and thermodynamic profiles from the Goddard Earth Observing System, version 5 (GEOS-5) to distinguish liquid water, mixed-phase, and ice water clouds. The MPLNET provides sparse global, autonomous, and continuous measurements of clouds and aerosols which have been used in a number of scientific investigations to date. The use of a standardized instrument and a common suite of data processing algorithms with thorough uncertainty characterization allows for straightforward comparisons between sites. Lidars with polarization capabilities have recently been incorporated into the MPLNET project which allows, for the first time, the ability to infer a cloud thermodynamic phase. This presentation will look specifically at the occurrence of ice and mixed phase clouds in the temperature region of -10 C to -40 C for different climatological regions and seasons. We compare MPLNET occurrences of mixed-phase clouds to an historical climatology based on observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft.

mixing layer height↗
NASA NTRS2017

Contributions of Mixed-Phase Clouds to Reduced Arctic Amplification

Earth’s Arctic is particularly sensitive to global warming. The climate record shows that Arctic changes in surface temperatures far exceed that of the global mean, a phenomenon referred to as Arctic amplification. Here, we show that warming of the Arctic atmosphere causes mixed-phase clouds in the region to contain less ice and more supercooled liquid, which in turn tends to increase their amount and thick- ness, thereby inducing a positive feedback mainly by increasing downward longwave (LW) radiation at the surface. The increased downward LW radiation decreases the positive lapse rate feedback in the Arctic, thus resulting in reduced Arctic amplification. The strength of this feedback depends on the initial mean-state supercooled liquid fraction (SLF) and the ice crystal effective radii. We also show that reduced precipitation rates can result from large mean-state ice effective radii being replaced by relatively more smaller liquid droplets in the cloud phase feedback, despite having high mean-state SLFs, demonstrating the importance of the representation of cloud microphysics in the Arctic.

Tan, Ivy↗