Noah LSM is a scientific and operational land surface scheme of both NCEP and NCAR and can be used to describe the land surface processes either in a stand-alone (e.g. NLDAS, GLDAS, LIS etc) or in the coupled land-atmospheric model system (e.g. WRF, GFS). The model has deficiency in modeling snowpack because several factors that influence mass and energy balance on the surface are either ineffectively considered or missed. For example, in Noah version 2.7.1, snow surface temperature is the controlling factor to initiate melt which results in early melting-the main reason for model's strong snow water equivalent (SWE) bias. Snow surface temperature also affects the sublimation rate during the snow accumulation period. With the onset of melt event, snow melting further speeds up because in the model warm snowpack does not have any liquid water holding capacity. All these processes are further influenced by albedo of the snow.
Therefore, the main purpose of this dissertation is to improve SWE simulation in Noah LSM which is achieved by modifying snow surface temperature, snow melt, and snow albedo estimation processes. By preserving single layer snowpack in Noah LSM, force-restore method is used to compute snow surface temperature. Snowmelt is controlled by accounting for internal energy of the snowpack and assuming liquid water energy equal to zero at melting point. Timing and amount of snowmelt is further improved by adding liquid water holding capacity to the ripen snowpack. Two different albedo decay formulations were studied and inclusion of the decay scheme enhances SWE estimation. The methods are tested at local and regional scale. Experiments show that including above elements in Noah can substantially reduce bias of SWE estimation, especially in areas with SWE being observed. Overall, the modified method improves snow simulation by Noah LSM by retaining the simplicity of the control model. It is suggested that the proposed method can be used to replace the current formulation for SWE estimation in the Noah LSM.
|Commitee:||Famiglietti, Jay, Hsu, Kuo-lin, Sanders, Brett F.|
|School:||University of California, Irvine|
|Department:||Civil Engineering - Ph.D.|
|School Location:||United States -- California|
|Source:||DAI-B 72/11, Dissertation Abstracts International|
|Subjects:||Geological, Civil engineering|
|Keywords:||Albedo, Land surface modeling, Noah land surface model, Snow physics, Snow surface temperature, Snow water equivalent|
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