جستجوی مقالات مرتبط با کلیدواژه « مدل regcm » در نشریات گروه « جغرافیا »

The Great Khorasan in northeast Iran has a variety of surface structures and plains and high peaks, but due to its vicinity to the deserts of Afghanistan and Turkmenistan, it is affected by dust all the time, especially in summer. The purpose of this study was to simulate summer dust in this region by RegCM model. For this purpose, during the period 2000 to 2017, three extreme dust events were selected. The satellite image used to confirmed dust mass presence and then the synoptic structure was analyzed. Finally, the simulation results of RegCM 4.6 model were compared with the observational data including the horizontal visibility and aerosol optical depth (AOD) of Aqua satellite. The synoptic analysis showed that during the summer, low thermal pressures form in the southern Afghanistan and high pressure in the north. This structure lead to the development of north and northeast winds with speeds of 12 to 21 m / s and dust emission on the eastern border of Iran and western Afghanistan. Investigation of RegCM accuracy done by visibility, Aquas’s AOD showed that model performance in South Khorasan is better as Razavi Khorasan. The highest correlation coefficients of AOD of model and horizontal visibility were obtained at Khorasan central stations including Gonabad, Ferdows, Nahaband and Ghaen at -0.82, -0.77 and -0.44 respectively. RegCM model performed a better dust simulation in severe dust with a horizontal visibility down to less than 1000 m, high continuity and horizontal extension. Overall, the RegCM model underestimates the AOD value for the Aqua satellite algorithm.

In this study, precipitation simulated annual and seasonal in north-east of Iran (Great Khorasan) In the period 1987-2011, using RegCM4 dynamic model in two case; with and without using post-processing technique. The required data for RegCM4 model with NetCDf format, received from ICTP center. For the implementation of the main dynamic model, Convective precipitation test scheme and the horizontal resolution, performed for year 2007. According to the test, Kuo Schema had less error than Emmanuel and Gurl schemes in Precipitation and region temperature modeling. Horizontal resolution selected 30 kilometer. After model implementation with Gurl schema and 30 kilometer horizontal resolution, Precipitation and temperature output post- processed using MA model. According to results, in the study area, during 2006-2011 verification period, average annual rainfall raw bias of RegCM4 model was calculated and post-processed equal to 8.3 millimeter and 61.04 respectively. Briefly in the annual time scale, in 75% of studied stations, post-processing is effective and MA model is more efficient. In seasonal scale, bias error of average precipitation is equal to : 54.99 millimeter in the winter, 27011 millimeter in the spring, -3.6 millimeter in the summer and 7.21 millimeter in the fall. Simulation of the temperature data in the stations using RegCM4 and MA model in north-east of Iran, revealed high performance. Bias error of average temperature is equal to -2.78 for RegCM4 model and post-processed equal to -0.05. In all stations, modeled Annual temperature and observational data has difference less than 0/1 ° C. In seasonal scale, the mean bias error range according ° C is equal to: -4.1 in the winter, -4.09 in the spring, -1.8 in the summer and -1.5 in the fall.

Introduction New meteorological numerical methods are developed into general circulation climate models since 1970, therefore. And different climatic models have been developed. Regional Climate Model (RegCM3) is used for climate studies and dynamic downscaling of atmosphere general circulation models output. Until now, many studies have been done using this model. Sensitivity of RegCM Model to different cumulus scheme for winter precipitation 1997 and 2000 are demonstrated by Babaeian and et al (2007). Result showed That Grell scheme with approximately 20% errors have good ability for winter precipitation simulation of Iran. Onol and et al (2009) have been investigated RegCM skill over Mediterranean region countries by using Kuo scheme. They found that annual mean simulated temperature is greater than CRU data. In this paper according to the role of autumn precipitation in water resource providing of the Khorasan area and for calibration and validation of RegCM3 as a research and seasonal prediction tool, a ten years Climate of Khorasan has been modeled for autumns 19991-2000. Materials and methods In this article, RegCM3 model is used for simulation of autumn precipitation and temperature over Khorasan. RegCM was originally developed by Giorgi et al (1993a, 1993b) and then improved and new generation released by Giorgi and Mearns (1999) and Pal et al. (2000). Dynamical core of the RegCM3 is fundamentally equivalent to the hydrostatic version of the NCAR/Pennsylvania State University mesoscale model MM5 (Grell et al., 1994). Surface processes are represented in the model using the Biosphere-Atmosphere Transfer Scheme, BATS. The non-local vertical diffusion scheme of Holtslag et al. (1990) is used to calculate the boundary layer physics. In addition, the physical parametrization is mostly based on the comprehensive radiative transfer package of the NCAR Community Climate Model, CCM3 (Kiehl et al., 1996). The mass flux cumulus cloud scheme of Grell (1993) is used to represent the convective precipitation with two possible closures: Arakawa and Schubert (1974) and Fristch and Chappell (1980). The Configuration of RegCM3 Model Optimize for Simulation of Precipitation and Temperature at Autumn Seasonal (September, October & November) in 1991-2000 The model domain covers whole of Iran and centered at 35°N, 57°E. Model is ran with a horizontal resolution of 15 * 15 km. The domain is roughly stretched over the latitude 55 to 61.5?N and longitude 30 to 40?E. RegCM may use initial and lateral boundary conditions from global analysis dataset, the output of a GCM or the output of a previous RegCM simulation. In our experiments these driving datasets are compiled from the Abdus Salam International Centre for Theoretical Physics. Modeled precipitations have been compared by both observed and CMAP data and modeled temperatures have been compared by observed and NCEP reanalysis data. Result and discussion Autumn precipitation in 1991-2000 simulated by RegCM3 and their seasonal bias is calculated for Grell-AS, Grell-FC, Kuo and Emanuel scheme relative to CMAP and observation data from equation 1: Bias = (1) Table 1 show Comparison between simulated and observed precipitation bias. According to table, bias maximum are found -209.9 mm in Grell-AS scheme at 1993. Table1. Comparison between simulated and observed precipitation bias over khorasan province (mm) Kuo Grell-FC Emanuel Grell-AS OBS year -39.1 -39.5 -39.1 -148.7 149.2 1991 -37.1 -38.5 -39.5 -64.1 65.3 1992 20.2 16.5 19.2 -209.9 260.8 1993 38.5 28.5 28.2 27.4 505.6 1994 -12.4 -17.3 -24.2 -19.7 224.4 1995 -12.3 -12.5 -16.2 -16.7 233.9 1996 18 -3.2 2.2 -8.2 752.5 1997 -32.9 -34.4 -33.2 -35.6 68.9 1998 -1.4 8.3 5.5 6.8 421.5 1999 -13.6 -13.2 -13.8 -16.4 595.1 2000 -7.1 -10.4 -11.1 -51.8 327.7 mean Comparison between simulated and observed temperature bias show that Grell-FC and Emanuel are better than cumulus scheme (see table 2). Table2. Comparison between simulated and observed temperature bias over khorasan province (°C) Kuo Grell-FC Emanuel Grell-AS OBS year -5.4 -5.4 -5.02 -4.6 16.2 1991 -5.0 -4.7 -5.3 -4.7 16.1 1992 0.1 0.2 0.5 0.1 9.2 1993 -0.6 -0.3 0.2 -0.3 13.4 1994 -0.8 -0.5 -0.2 -0.6 12.1 1995 -1.0 -0.7 -0.6 -0.7 9.1 1996 -2.2 0.4 0.6 0.4 9.7 1997 -0.7 -0.6 -0.4 -0.6 12.9 1998 -2.0 2.3 -0.1 -0.6 9.8 1999 -0.4 -2.0 -0.6 -0.7 8.9 2000 -1.8 -1.1 -1.1 -1.2 11.7 mean Conclusion Comparing to the observed precipitation, minimum mean monthly and seasonal bias are found in Kuo parameterization scheme by -0.9 and -7.1 mm, respectively and minimum mean absolute errors are found in Grell-FC scheme by 19.3 and 21.3 mm. relating to the CMAP precipitation data minimum seasonal bias are found to be in Emanuel scheme by 9.3 mm. Comparison the modeled temperature shows that the minimum monthly and seasonal biases are found in Grell-FC scheme by -1.1 °C. Minimum error was -3.4°C in Grell-FC scheme by comparing the modeled data to NCEP reanalysis data. Overally, it can be conduced that Grell-AS has no suitable skill for modeling monthly to seasonal precipitation and temperature of the Khorasan province. The results of this paper can be used in operational seasonal predictions and research purposes as well.