The Weather Research and Forecasting (WRF) model and its three-dimensional variational data assimilation system are used in this study to assimilate the INSAT-3D, a recently launched Indian geostationary meteorological satellite derived from atmospheric motion vectors (AMVs) over the South Asian region during peak Indian summer monsoon month (i.e., July 2014). A total of four experiments were performed daily with and without assimilation of INSAT-3D-derived AMVs and the other AMVs available through Global Telecommunication System (GTS) for the entire month of July 2014. Before assimilating these newly derived INSAT-3D AMVs in the numerical model, a preliminary evaluation of these AMVs is performed with National Centers for Environmental Prediction (NCEP) final model analyses. The preliminary validation results show that root-mean-square vector difference (RMSVD) for INSAT-3D AMVs is ～3.95, 6.66, and 5.65 ms?1 at low, mid, and high levels, respectively, and slightly more RMSVDs are noticed in GTS AMVs (～4.0, 8.01, and 6.43 ms?1 at low, mid, and high levels, respectively). The assimilation of AMVs has improved the WRF model of produced wind speed, temperature, and moisture analyses as well as subsequent model forecasts over the Indian Ocean, Arabian Sea, Australia, and South Africa. Slightly more improvements are noticed in the experiment where only the INSAT-3D AMVs are assimilated compared to the experiment where only GTS AMVs are assimilated. The results also show improvement in rainfall predictions over the Indian region after AMV assimilation. Overall, the assimilation of INSAT-3D AMVs improved the WRF model short-range predictions over the South Asian region as compared to control experiments. 相似文献
The global model analysis has significant impact on the mesoscale model forecast as global model provides initial condition (IC) and lateral boundary conditions (LBC) for the mesoscale model. With this objective, four operational global model analyses prepared from the European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS), NCEP Global Forecasting System (GFS), and National Centre for Medium Range Weather Forecasting (NCMRWF) are used daily to generate IC and LBC of the mesoscale model during 13th December 2012 to 13th January 2013. The Weather Research and Forecasting (WRF) model version 3.4, broadly used for short-range weather forecast, is adopted in this study as mesoscale model. After initial comparison of global model analyses with Atmospheric Infrared Sounder (AIRS) retrieved temperature and moisture profiles, daily WRF model forecasts initialized from global model analyses are compared with in situ observations and AIRS profiles. Results demonstrated that forecasts initialized from the ECMWF analysis are closer to AIRS-retrieved profiles and in situ observations compared to other global model analyses. No major differences are occurred in the WRF model forecasts when initialized from the NCEP GDAS and GFS analyses, whereas these two analyses have different spatial resolutions and observations used for assimilation. Maximum RMSD is seen in the NCMRWF analysis-based experiments when compared with AIRS-retrieved profiles. The rainfall prediction is also improved when WRF model is initialized from the ECMWF analysis compared to the NCEP and NCMRWF analyses. 相似文献
Summary It is shown that there exists a mechanism that can cause north-northwest movement of tropical cyclones in addition to already recognised mechanisms such as steering current and beta drift. This mechanism depends on the interaction between organised convection and dynamics. In the initial stages of formation of a cyclone, it is assumed that the hydrodynamic instabilities result in an incipient disturbance that organises some convection giving rise to a heat source. The atmospheric response to a localized heat source located off the equator in the northern hemisphere produces a low level vorticity field with a maximum in the northwest sector of the original heat source. If the Ekman-CISK which depends on the low level vorticity, was the dominating mechanism for moisture convergence, the location of the heat source would move to the new location of vorticity maximum. A repetition of this process would result in a northwest movement of the heat source and hence that of the cyclone. The movement of a tropical vortex under the influence of this mechanism which depends on asymmetries created by linear dispersion of Rossby waves is first illustrated using a linear model. It is then demonstrated that this process also enhances the motion of a tropical vortex in a nonlinear model. Importance of this feedback and the resulting movements of a tropical vortex in determining the actual track of a cyclone and in bogusing an initial vortex for prediction models are illustrated.With 6 Figures 相似文献
Climate Dynamics - Modification of the vertical structure of non-adiabatic heating by significant abundance of the stratiform rain in the tropics has been known to influence the large-scale... 相似文献
Natural Hazards - The present study focuses on investigating the impacts of a sudden dust storm on the atmospheric boundary layer (ABL) over Ahmedabad (23.02°N, 72.57°E), an urban site... 相似文献
The tropical cyclones are very destructive during landfall, generating high wind speeds, heavy intensive rainfall, and severe storm surges with huge coastal inundations that have massive socioeconomic and ecological catastrophic effects on human beings and the economic well-being. The sizable ecological effects of cyclonic storms cannot be ignored because of the uncertainty of impact, intensity induced by a warming ocean, and sea level rise. The Super Cyclonic Storm Amphan which falls under the category five classifications under the scheme of the India Meteorological Department (IMD), on the basis the maximum sustained wind speeds gusting up to 168 km/h affected parts of West Bengal and Odisha in India, and south-west Bangladesh between May 16 and 20, 2020. In this work, we have focused on the coastal districts of Kendrapada, Bhadrak, Balasore in Odisha, Purba Medinipur, and South Twenty-Four Parganas in West Bengal, India and, Khulna, Barisal division of Bangladesh that have been seriously affected by the Super Cyclonic Storm Amphan. The objective of the study is to analyze the eco-physical assessment of tropical cyclone Amphan using geospatial technology. Therefore, shoreline change detection and enhance vegetation index have been used in this research work to systematically analyze the eco-physical impact parameters of Cyclonic Storm Amphan using ortho-rectified Landsat 8/OLI imagery and MODIS dataset of USGS with high spatial resolutions of 30–500 m. The result highlights that about 60.33% of the total transects of the study area was eroded, but only 24.99% of the total transects experienced accretion, and 14.68% of the total transects depicted stability. The scientific study will benefit coastal managers and policymakers in formulating action plans for coastal zone management, natural resilience, and sustainable future development.
Natural Hazards - This study uses a high-resolution Weather Research and Forecasting model coupled with the chemistry module (WRF-Chem) to analyze the dust storm that occurred during 12?17... 相似文献
