حسن خالقی زواره

In this work‎, ‎sensitivity and performance of the Weather Research and Forecasting (WRF) model for surface wind field simulations are evaluated under several initial and‎ boundary conditions‎, ‎along with‎ ‎different planetary boundary layer (PBL) schemes during several dates over the Persian Gulf region‎. Since there are differences between production approaches and development periods of analysis and reanalysis data (namely‎, ‎assimilation system) on the one hand‎, ‎and‎ differences in applied method for PBL parameterization by any scheme on the other hand‎, ‎this paper aims to identify a suitable set up among the whole configurations which‎ are under examination‎. ‎To this end‎, ‎three datasets (two reanalyses and one analysis) including‎, ‎ERA-Interim‎, ‎NCEP-R2‎, ‎and NCEP-FNL and six PBL‎ schemes (two local and four nonlocal) including ACM2‎, ‎BouLac‎, ‎MYJ‎, ‎MYNN‎, ‎QNSE‎, ‎and YSU accompanied by their relevant surface-layer schemes are used‎. To assess the WRF model wind simulations, available observational wind data including 22 synoptic weather stations located in the region and‎ observations of QuikSCAT and ASCAT satellites are employed‎. Findings of this study indicate that when the wind simulations are compared with synoptic weather stations observations‎, ‎irrespective of the type of PBL scheme‎, ‎ERA-Interim and‎ NCEP-FNL datasets exhibit better performance in comparison with the NCEP-R2 and ‎when PBL schemes are also considered‎, ‎results show that combination of YSU scheme and‎ ERA-Interim reanalysis data leads to a better estimate of wind speed and combination of YSU and NCEP-FNL data generates less error for wind direction‎. Moreover‎, ‎comparison of model wind simulations and observations of QuikSCAT and ASCAT satellites shows that there are no substantial differences between various‎ configurations‎. ‎However‎, ‎using YSU and ACM2 scheme‎s, ‎WRF model generates speed and direction of the wind close to the observations of QuikSCAT‎. Although all tests have almost similar results as ASCAT satellite observations‎, ‎YSU scheme estimates are slightly better than other schemes. Overall, the results of this study revealed that the major difference between WRF wind simulations and measured winds arises from the choice of initial conditions data and it does not depend on different PBL schemes. Consequently, changing initial and boundary conditions data has a noticeable impact on the model wind results. Thus, in future studies, emphasis must be more on reanalysis and analysis datasets and the option of WRF PBL parameterization schemes should be the second priority. Due to the fairly good similarity of the model surface wind with QuikSCAT and ASCAT observations, the choice of WRF model simulations as offshore wind database can be a valid available alternative instead of QuikSCAT and ASCAT wind, particularly when meeting their limitation in spatial resolution (swath data) or temporal sampling.

The Persian Gulf with subtropical climate is located between latitudes of 23-30 degrees, whit its coast adjoiner to Iraq, Kuwait, Saudi Arabia, Qatar and United Arab Emirates from one side and to Iran from the other side. The Persian Gulf’s width in widest part is 370 km and its length is 990 km. For people living near the sea and the surrounding coastal area as well as construction of onshore and offshore structures, knowledge and understating of the wind field and its variability is essential. In addition, the most common effect of wind is seen in wind driven currents, swells, upwelling and down-welling systems. Moreover wind stress plays a key role in the modeling of air sea interaction phenomenon, e.g., determination of the drag coefficient. Although other factors such as wind palfern and oceanic current are also contributing to the in determination of this coefficient but the wind is the main governing factor. In other words, any inaccuracy in determination of the sea surface wind field could cause a large over or under estimations in atmospheric and oceanic estimations.
This work is devoted to verify the effects of different initial and boundary condition in global data (using reanalysis and analysis datasets) on numerical simulations of WRF (Weather Research and Forecasting) model over the Persian Gulf area. The main obstacle in the verification and evaluation of a model simulation is the lack of observation data with fine spatial and temporal resolution, in particular for offshore areas. Fortunately, in onshore areas, the existence of weather stations has solved the problem somehow, and for offshore areas satellite data are found to be the best dataset considering the spatial coverage. In the present study, simulations of WRF model are compared with different type of observation data. In this research, two types of data are used for verifying the model, i.e. Synoptic stations data and Satellite data (QuikSCAT and ASCAT).
The WRF model version 3.4.1 is employed with ARW dynamical core for simulating of sea surface wind field over the Persian Gulf region. Considering the connection and information exchange between the domains, a two way nesting method is applied in simulations. As the goal was just to verify the effects of different initial and boundary conditions on simulations, therefore, for all the simulations the number of domains and their analogous grid sizes are considered the same. For these simulations three domains are considered the main domain approximately covers the whole are of the Middle East, from West and some parts of Far East with 36km spatial grid spacing. First nested domain covers the southern half of Iran along with marginal countries of Persian Gulf, with a 12km spatial grid resolution and ultimately, the innermost domain of the Persian Gulf that also includes some parts of Oman Sea with 4km grid spacing. The time step for simulations is assumed 216seconds and the time period for each simulation is 30hours, from which the first 6 hours are assumed as spin-up time. To provide the initial and boundary conditions three datasets of ERA-Interim (ECMWF Re-Analysis Interim), NCEP-FNL and NCEP-R2 are employed.
Along with lots of effective factors, results from this research show that one of the sources of error in the WRF model wind simulations is the selection of initial and boundary conditions (input data). The obtained results of this work reveal that for the surface wind hindcast simulations over the Persian Gulf using WRF model, the ECMWF ERA-Interim data is a more suitable dataset to provide the initial and boundary conditions, rather than the NCEP-FNL and NCEP-R2 data. However, the NCEP-FNL is an alternative data set when the ERA-Interim data has some lacks.