Zeng Xubin

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Zeng
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Xubin
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  • Article
    On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream
    (American Geophysical Union, 2021-09-08) Chellappan, Seethala ; Zuidema, Paquita ; Edson, James B. ; Brunke, Michael ; Chen, Gao ; Li, Xiang-Yu ; Painemal, David ; Robinson, Claire ; Shingler, Taylor ; Shook, Michael ; Sorooshian, Armin ; Thornhill, Kenneth L. ; Tornow, Florian ; Wang, Hailong ; Zeng, Xubin ; Ziemba, Luke
    The warm Gulf Stream sea surface temperatures strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalyses, affecting the turbulent surface fluxes. Known problems within the ERA5 boundary layer (too-dry and too-cool with too strong westerlies), ascertained primarily from ACTIVATE 2020 campaign aircraft dropsondes and secondarily from older buoy measurements, reinforce surface flux biases. In contrast, MERRA2 winter surface winds and air-sea temperature/humidity differences are slightly too weak, producing surface fluxes that are too low. Reanalyses boundary layer heights in the strongly forced winter cold-air-outbreak regime are realistic, whereas late-summer quiescent stable boundary layers are too shallow. Nevertheless, the reanalysis biases are small, and reanalyses adequately support their use for initializing higher-resolution cloud process modeling studies of cold-air outbreaks.
  • Article
    Use of observing system simulation experiments in the United States
    (American Meteorological Society, 2020-08-01) Zeng, Xubin ; Atlas, Robert ; Birk, Ronald J. ; Carr, Frederick H. ; Carrier, Matthew J. ; Cucurull, Lidia ; Hooke, William H. ; Kalnay, Eugenia ; Murtugudde, Raghu ; Posselt, Derek J. ; Russell, Joellen ; Tyndall, Daniel P. ; Weller, Robert A. ; Zhang, Fuqing
    The NOAA Science Advisory Board appointed a task force to prepare a white paper on the use of observing system simulation experiments (OSSEs). Considering the importance and timeliness of this topic and based on this white paper, here we briefly review the use of OSSEs in the United States, discuss their values and limitations, and develop five recommendations for moving forward: national coordination of relevant research efforts, acceleration of OSSE development for Earth system models, consideration of the potential impact on OSSEs of deficiencies in the current data assimilation and prediction system, innovative and new applications of OSSEs, and extension of OSSEs to societal impacts. OSSEs can be complemented by calculations of forecast sensitivity to observations, which simultaneously evaluate the impact of different observation types in a forecast model system.