Numerical Weather Model-based Satellite Precipitation Adjustment over Complex Terrain
Dr. Xinxuan Zhang
University of Connecticut, USA
This research contributes to the improvement of high resolution satellite applications over mountainous topography. Such mountainous regions are usually covered by sparse networks of in-situ observations while quantitative precipitation estimation from satellite sensors exhibits strong underestimation of heavy orographically enhanced storm events. To address this issue, our research applies a satellite error correction technique based solely on high-resolution numerical weather simulations.
The error correction technique has been applied on six major mountain ranges all over the world and bringssignificant improvements on the satellite precipitation products comparing with ground observations(Zhang et al. 2013*1, Zhang et al. 2016*2). So far two different satellite precipitation products, NOAA Climate Prediction Center morphing technique (CMORPH) product and the Global Satellite Mapping of Precipitation (GSMaP) product,are considered. Future study will include the newly released IMERG products as well. Hydrological model is employed to evaluatesatellite precipitation error propagation in runoff simulations.
Improving the Representation of Estuarine Processes in Earth System Models
Dr. Qiang Sun
University of Connecticut, USA
The exchange of freshwater between the rivers and estuaries and the open ocean represents a unique form of scale-interaction in the climate system. The local variability in the terrestrial hydrologic cycle is integrated by rivers over potentially large drainage basins (up to semicontinental scales), and is then imposed on the coastal ocean at the scale of a river mouth. Appropriately treating riverine freshwater discharge into the oceans in Earth system models is a challenging problem. Commonly, the river runoff is discharged into the ocean models with zero salinity and arbitrarily distributed either horizontally or vertically over several grid cells. Those approaches entirely neglect estuarine physical processes that modify river inputs before they reach the open ocean. A physically based Estuary Box Model (EBM) is developed to parameterize the mixing processes in estuaries. The EBM has a two-layer structure representing the mixing processes driven by tides and shear flow within the estuaries. It predicts the magnitude of the mixing driven exchange flow, bringing saltier lower-layer shelf water into the estuary to mix with river water prior to discharge to the upper-layer open ocean. The EBM has been tested against observations and high-resolution three-dimensional simulations of the Columbia River estuary, showing excellent agreement in the predictions of the strength of the exchange flow and the salinity of the discharged water, including modulation with the spring-neap tidal cycle. The EBM is implemented globally at every river discharge point of the Community Earth System Model (CESM). The results from experiments are compared with native salinity climatology basic on the World Ocean Database. And it shows the EBM improves the global upper ocean salinity flied. This is the first study to reveal the influences of the estuarine exchange flows in global ocean.