Fig 3 - uploaded by P.K. Kunhikrishnan
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Pictorial representation of data assimilation window in time. Observational data point is available at t = 12 Hrs. Y-axis shows the percentage of alteration in model variables for the corresponding time.
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In this article, we describe a simple yet effective method for insertion of observational datasets in a mesoscale atmospheric model used in one-dimensional configuration through Nudging. To demonstrate the effectiveness of this technique, vertical profiles of meteorological parameters obtained from GLASS Sonde launches from a tiny island of Kaashid...
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Citations
... The spatial discretization is achieved by second order quadratically conservative and fourth quadratically conservative finite differences for advection and second order differencing for other terms, while temporal discretization is treated with a second order leap-frog scheme for large time steps with Asselin time filter option. Depending on the choice of Users and availability of lateral boundary conditions, ARPS can be configured in one-, two-and three-dimensional modes (Subrahamanyam et al., 2008). This model has a salient feature that the base state of the model variables can be initialized through a single sounding profile and time dependent fields can be opted for self initialization using analytic functions. ...
... Within the permissible constraints of the model, it was noticed that these parameters required hyper-tuning with greater accuracy and quantification. For nowcasting purpose, ARPS model-simulated forecast products are vastly used and are considered to be reasonably accurate up to +6 hours (Subrahamanyam et al., 2008). ...
... Table 2 describes ARPS model run configuration used in the present study, while Table 3 provides a glimpse of major differences between the two models. One of the basic differences in the two model simulations is that HRM is initialized with a global model analyses and its lateral boundary conditions are taken from the forecast of global model, whereas the base-state field for ARPS domain is generated through vertical column GPS ascents and potential temperature perturbations are generated through symmetric random option available within the model code (Subrahamanyam et al. 2006(Subrahamanyam et al. , 2008Xue et al. 1995). ...
... Since C-11 campaign was mostly influenced with frequent thundershowers and associated rainfall events, ARPS model was customized for SHAR domain and made operational for providing the probability of thunderstorm for ?6 to ?12 h, and forecast products were updated regularly in time during the launch window. The ARPS model was initialized with the vertical profiles of meteorological parameters obtained from the indigenously developed balloon-borne Pisharoty sondes (Satyanarayana 2008;Subrahamanyam et al. 2008). The entire exercise was focused on the consolidation of the model-simulated parameters in a scientific and logical way to provide the probability of thunderstorm occurrence. ...
Accurate knowledge of different meteorological parameters over a launch site is very crucial for efficient management of satellite launch operations. Local weather over the Indian satellite launch site located at Sriharikota High Altitude Range (SHAR: 13. 72°N, 80. 22°E) is very much dependent on the atmospheric circulation prevailing over the Bay of Bengal oceanic region and topography-induced convective activities. With a view to providing severe weather threat prediction in terms of launch commit criteria (LCC), two numerical atmospheric models namely high-resolution regional model (HRM) and advanced regional prediction system (ARPS) are made operational over SHAR in a synoptic and mesoscale domain, respectively. In the present research article, two launch campaigns through Polar Satellite Launch Vehicle (PSLV-C11 and PSLV-C12) when contrasting weather conditions prevailed over the launch site are chosen for demonstration of potential of two models in providing location-specific short-to-medium-range weather predictions meeting the needs of LCC. In the case of PSLV-C11 campaign, when the launch site underwent frequent thundershower-associated rainfall, ARPS model-derived meteorological fields were effectively used in prediction of probability of the wet spells. On the other hand, Bay of Bengal underwent severe cyclonic storm during PSLV-C12 campaign, and its formation was reasonable captured through HRM simulations. It is concluded that a combination of HRM and ARPS provide reliable short-to-medium-range weather prediction over SHAR, which has got profound importance in launch-related activities.
Modeling homogeneous Atmospheric Boundary Layers (ABLs) in Computational Wind Engineering (CWE) requires that all of the conservation equations are in equilibrium. A standard approach is to apply appropriate boundary conditions in order to maintain the inlet prescribed ABL profiles. Recently, the investigation has turned to the implementation of suitable source terms in the momentum equation. In the present work, the ABL is numerically simulated for neutral, stable and unstable atmosphere using nudging, a type of Data Assimilation. Simulations were performed with an in-house code that solves the Reynolds-averaged Navier-Stokes equations and the standard k-ε turbulence model in steady state. The prescribed inlet flow profiles correspond to the reference data, which is used to define the nudging source terms that are added to the equations. The source terms play a role resembling a body-force and a source-sink mechanism in the momentum and TKE equations, respectively. This novel approach is shown to be reliable in ensuring streamwise homogeneity, under both neutral and non-neutral conditions, for the equilibrium ABL.
