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Sensitivity of WRF simulated typhoon track and intensity over the South China Sea to horizontal and vertical resolutions
Wu Zhiyuan, Jiang Changbo, Deng Bin, Chen Jie, Liu Xiaojian
2019, 38(7): 74-83. doi: 10.1007/s13131-019-1459-z
Keywords: sensitivity analysis, typhoon track and intensity, horizontal and vertical resolutions, Typhoon Kai-tak, WRF
To determine the grid resolutions of the WRF model in the typhoon simulation, some sensitivity analysis of horizontal and vertical resolutions in different conditions has been carried out. Different horizontal resolutions (5, 10, 20, 30 km), nesting grids (15 and 5 km), different vertical resolutions (35-layers, 28-layers, 20-layers) and different top maximum pressures (1 000, 2 000, 3 500, 5 000 Pa) had been used in the mesoscale numerical model WRF to simulate the Typhoon Kai-tak. The simulation results of typhoon track, wind speed and sea level pressure at different horizontal and vertical resolutions have been compared and analyzed. The horizontal and vertical resolutions of the model have limited effect on the simulation effect of the typhoon track. Different horizontal and vertical resolutions have obvious effects on typhoon strength (defined by wind speed) and intensity (defined by sea level pressure, SLP), especially for sea level pressure. The typhoon intensity simulated by the high-resolution model is closer to the real situation and the nesting grids can improve computational accuracy and efficiency. The simulation results affected by vertical resolution using 35-layers is better than the simulation results using 20-layers and 28-layers simulations. Through comparison and analysis, the horizontal and vertical resolutions of WRF model are finally determined as follows:the two-way nesting grid of 15 and 5 km is comprehensively determined, and the vertical layers is 35-layers, the top maximum pressure is 2 000 Pa.
Numerical simulations and comparative analysis for two types of storm surges in the Bohai Sea using a coupled atmosphere-ocean model
LI Yong, CHEN Xin, JIANG Xingyu, LI Jianfen, TIAN Lizhu
2019, 38(9): 35-47. doi: 10.1007/s13131-019-1383-9
Keywords: the Bohai Sea, extratropical storm surge, typhoon storm surge, coupled atmosphere-ocean model, WRF, ROMS
The Bohai Sea is extremely susceptible to storm surges induced by extratropical storms and tropical cyclones in nearly every season. In order to relieve the impacts of storm surge disasters on structures and human lives in coastal regions, it is very important to understand the occurring of the severe storm surges. The previous research is mostly restricted to a single type of storm surge caused by extratropical storm or tropical cyclone. In present paper, a coupled atmosphere-ocean model is developed to study the storm surges induced by two types of extreme weather conditions. Two special cases happened in the Bohai Sea are simulated successively. The wind intensity and minimum sea-level pressure derived from the Weather Research and Forecasting (WRF) model agree well with the observed data. The computed time series of water level obtained from the Regional Ocean Modeling System (ROMS) also are in good agreement with the tide gauge observations. The structures of the wind fields and average currents for two types of storm surges are analyzed and compared. The results of coupled model are compared with those from the uncoupled model. The case studies indicate that the wind field and structure of the ocean surface current have great differences between extratropical storm surge and typhoon storm surge. The magnitude of storm surge in the Bohai Sea is shown mainly determined by the ocean surface driving force, but greatly affected by the coastal geometry and bathymetry.
Biases of the Arctic climate in a regional ocean-sea ice-atmosphere coupled model: an annual validation
LIU Xiying
2014, 33(9): 56-67. doi: 10.1007/s13131-014-0518-2
Keywords: Arctic climate, coupled model, numerical simulation
The Coupling of three model components, WRF/PCE (polar climate extension version of weather research and forecasting model (WRF)), ROMS (regional ocean modeling system), and CICE (community ice code), has been implemented, and the regional atmosphere-ocean-sea ice coupled model named WRF/PCEROMS-CICE has been validated against ERA-interim reanalysis data sets for 1989. To better understand the reasons that generate model biases, the WRF/PCE-ROMS-CICE results were compared with those of its components, the WRF/PCE and the ROMS-CICE. There are cold biases in surface air temperature (SAT) over the Arctic Ocean, which contribute to the sea ice concentration (SIC) and sea surface temperature (SST) biases in the results of the WRF/PCE-ROMS-CICE. The cold SAT biases also appear in results of the atmospheric component with a mild temperature in winter and similar temperature in summer. Compared to results from the WRF/PCE, due to influences of different distributions of the SIC and the SST and inclusion of interactions of air-sea-sea ice in the WRF/PCE-ROMS-CICE, the simulated SAT has new features. These influences also lead to apparent differences at higher levels of the atmosphere, which can be thought as responses to biases in the SST and sea ice extent. There are similar atmospheric responses in feature of distribution to sea ice biases at 700 and 500 hPa, and the strength of responses weakens when the pressure decreases in January. The atmospheric responses in July reach up to 200 hPa. There are surplus sea ice extents in the Greenland Sea, the Barents Sea, the Davis Strait and the Chukchi Sea in winter and in the Beaufort Sea, the Chukchi Sea, the East Siberian Sea and the Laptev Sea in summer in the ROMS-CICE. These differences in the SIC distribution can all be explained by those in the SST distributions. These features in the simulated SST and SIC from ROMS-CICE also appear in the WRF/PCE-ROMS-CICE. It is shown that the performance of the WRF/PCE-ROMS-CICE is determined to a large extent by its components, the WRF/PCE and the ROMS-CICE.
Sensitivity of the Arctic sea ice concentration forecasts to different atmospheric forcing: a case study
YANG Qinghua, LIU Jiping, ZHANG Zhanhai, SUI Cuijuan, XING Jianyong, LI Ming, LI Chunhua, ZHAO Jiechen, ZHANG Lin
2014, 33(12): 15-23. doi: 10.1007/s13131-014-0566-7
Keywords: Arctic Ocean
A regional Arctic configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) is used as the coupled ice-ocean model for forecasting sea ice conditions in the Arctic Ocean at the National Marine Environmental Forecasting Center of China (NMEFC), and the numerical weather prediction from the National Center for Environmental Prediction Global Forecast System (NCEP GFS) is used as the atmospheric forcing. To improve the sea ice forecasting, a recently developed Polar Weather Research and Forecasting model (Polar WRF) model prediction is also tested as the atmospheric forcing. Their forecasting performances are evaluated with two different satellite-derived sea ice concentration products as initializations: (1) the Special Sensor Microwave Imager/Sounder (SSMIS) and (2) the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). Three synoptic cases, which represent the typical atmospheric circulations over the Arctic Ocean in summer 2010, are selected to carry out the Arctic sea ice numerical forecasting experiments. The evaluations suggest that the forecasts of sea ice concentrations using the Polar WRF atmospheric forcing show some improvements as compared with that of the NCEP GFS.
A numerical simulation of latent heating within Typhoon Molave
LIU Yang, LIN Wenshi, LI Jiangnan, WANG Gang, YANG Song, FENG Yerong
2017, 36(7): 39-47. doi: 10.1007/s13131-017-1082-3
Keywords: latent heat, weather research and forecasting model, Typhoon Molave, thermodynamic structure, cloud microphysics, zero degree isotherm
The weather research and forecasting (WRF) model is a new generation mesoscale numerical model with a fine grid resolution (2 km), making it ideal to simulate the macro- and micro-physical processes and latent heating within Typhoon Molave (2009). Simulations based on a single-moment, six-class microphysical scheme are shown to be reasonable, following verification of results for the typhoon track, wind intensity, precipitation pattern, as well as inner-core thermodynamic and dynamic structures. After calculating latent heating rate, it is concluded that the total latent heat is mainly derived from condensation below the zero degree isotherm, and from deposition above this isotherm. It is revealed that cloud microphysical processes related to graupel are the most important contributors to the total latent heat. Other important latent heat contributors in the simulated Typhoon Molave are condensation of cloud water, deposition of cloud ice, deposition of snow, initiation of cloud ice crystals, deposition of graupel, accretion of cloud water by graupel, evaporation of cloud water and rainwater, sublimation of snow, sublimation of graupel, melting of graupel, and sublimation of cloud ice. In essence, the simulated latent heat profile is similar to ones recorded by the Tropical Rainfall Measuring Mission, although specific values differ slightly.
A hindcast of the Bohai Bay oil spill during June to August 2011
YANG Yiqiu, LI Yan, LIU Guimei, PAN Qingqing, WANG Zhaoyi
2017, 36(11): 21-26. doi: 10.1007/s13131-017-1135-7
Keywords: oil spill, hindcast, Lagrangian random walk, oil distribution, swept area
An operational three-dimensional oil spill model is developed by the National Marine Environmental Forecasting Center (NMEFC), State Oceanic Administration, China, and the model has been running for 9 a. On June 4 and 17, 2011, oil is spilled into the sea water from two separate oil platforms in the Bohai Bay, i.e., Platforms B and C of Penglai 19-3 oilfield. The spill causes pollution of thousands of square kilometres of sea area. The NMEFC's oil spill model is employed to study the Penglai 19-3 oil-spill pollution during June to August 2011. The wind final analysis data of the NMEFC, which is based on a weather research and forecasting (WRF) model, are analyzed and corrected by comparing with the observation data. A corrected current filed is obtained by forcing the princeton ocean model (POM) with the corrected wind field. With the above marine environmental field forcing the oil spill model, the oil mass balance and oil distribution can be produced. The simulation is validated against the observation, and it is concluded that the oil spill model of the NMEFC is able to commendably simulate the oil spill distribution. Thus the NMEFC's oil spill model can provide a tool in an environmental impact assessment after the event.
Down-scaled regional ocean modeling system (ROMS) for high-resolution coastal hydrodynamics in Korea
LIM Hak-Soo, KIM Chang S, PARK Kwang-Soon, SHIM Jae Seol, CHUN Insik
2013, 32(9): 50-61. doi: 10.1007/s13131-013-0352-y
Keywords: down-scaled operational oceanographic system, regional oceanmodeling system, wave coupled model, real-time monitoring system
A down-scaled operational oceanographic system is developed for the coastal waters of Korea using a regional ocean modeling system (ROMS). The operational oceanographic modeling system consists of atmospheric and hydrodynamic models. The hydrodynamic model, ROMS, is coupled with wave, sediment transport, and water qualitymodules. The system forecasts the predicted results twice a day on a 72 h basis, including sea surface elevation, currents, temperature, salinity, storm surge height, and wave information for the coastal waters of Korea. The predicted results are exported to the web-GIS-based coastal information system for real-time dissemination to the public and validation with real-time monitoring data using visualization technologies. The ROMS is two-way coupledwith a simulatingwaves nearshoremodel, SWAN, for the hydrodynamics and waves, nested with themeteorologicalmodel,WRF, for the atmospheric surface forcing, and externally nested with the eutrophicationmodel, CE-QUAL-ICM, for the water quality. The operational model, ROMS, was calibrated with the tidal surface observed with a tide-gage and verified with current data observed by bottom-mounted ADCP or AWAC near the coastal waters of Korea. To validate the predicted results, we used real-time monitoring data derived from remote buoy system, HF-radar, and geostationary ocean color imager (GOCI). This down-scaled operational coastal forecasting system will be used as a part of the Korea operational oceanographic system(KOOS) with other operational oceanographic systems.
Distribution characteristics of wave energy in the Zhe-Min coastal area
Qin Ye, Zhongliang Yang, Min Bao, Weiyong Shi, Hongyuan Shi, Zaijin You, Wenyan Zhang
2022, 41(5): 163-172. doi: 10.1007/s13131-021-1859-2  Published:2022-05-31
Keywords: SWAN model, wave energy, wave power density, effective duration, Zhe-Min coastal area
A 10-year (2003–2012) hindcast was conducted to study the wave field in the Zhe-Min coastal area (Key Area OE-W2) located off Zhejiang and Fujian provinces of China. Forced by the wind field from a weather research and forecasting model (WRF), high-resolution wave modelling using the SWAN was carried out in the study area. The simulated wave fields show a good agreement with observations. Using the simulation results, we conducted statistical analysis of wave power density in terms of spatial distribution and temporal variation. The effective duration of wave energy in the sea area was discussed, and the stability of wave energy was evaluated using the coefficient of variation of wave power density. Results indicate that the wave energy resource in the study area was about 4.11×106 kW. The distribution of wave energy tends to increase from the north (off Zhejiang coast) to the south (off Fujian coast), and from near-shore area to the open sea. The sea areas with wave power density greater than 2 kW/m are mostly distributed seaward of the 10-m isobath, and the contours of the wave power density are almost parallel to the shoreline. The sea areas around the islands that are far from the mainland are rich in wave energy, usually more than 6 kW/m, and therefore are of obvious advantages in planning wave energy development and utilization. The effective duration of wave energy in the offshore area shows an increasing trend from north (off Zhejiang coast) to south (off Fujian coast), with values of ~3 500 h in the north and ~4 450 h in the south. The coefficient of variation of wave energy in this region is mostly in the range of 1.5–3.0, and gradually decreases from the north to the south, suggesting that the wave energy in the south is more stable than that in the north.