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Meridional Component (meridional + component)
Selected AbstractsSeasonal variability in the response of the airflow characteristics to the changes in the macro-scale westerly flow intensity over Europe, 1971,2000INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2009Michal Marosz Abstract The aim of the research was to identify the seasonal variability of correlation between the air motion characteristics and common zonal circulation index (Rossby's Index). Air flow characteristics comprised divergence and vorticity. The spatial coverage of the research was the so called Euro-Atlantic Region covering parts of North Atlantic and Europe (40W,40E, 35N,75N). Temporal extent was 1971,2000 thus matching the latest WMO normal period. The data used was the components of the wind vector (u,zonal component, v,meridional component) and geopotential heights (hgt) from NCEP/NCAR Reanalysis. The response of the vorticity field is apparent and the greatest variability is noted at 1000 hPa. The mid and upper levels in the troposphere reveal quite homogenous response of vorticity to the macro-scale forcing. The response of the divergence field is also apparent though more complex in the vertical profile of the troposphere. The analysis of correlation was followed by the description of annual as well as seasonal shape of vorticity and divergence fields in the extremes of Rossby Index. Copyright © 2008 Royal Meteorological Society [source] Data assimilation of high-density observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005I: Impact on initial conditions for the MAP/SOP IOP2b Abstract An attempt is made to evaluate the impact of the data assimilation of high-frequency data on the initial conditions. The data assimilation of all the data available on the Mesoscale Alpine Program archive for a test case is performed using the objective analysis and the Variational Data Assimilation (Var) techniques. The objective analysis is performed using two different schemes: Cressman and multiquadric; 3D-Var is used for the variational analysis. The European Centre for Medium-Range Weather Forecasts analyses are used as first guess, and they are blended together with the observations to generate an improved set of mesoscale initial and boundary conditions for the Intensive Observing Period 2b (17,21 September 1999). A few experiments are performed using the initialization procedure of MM5, the mesoscale model from Penn State University/National Center for Atmospheric Research. The comparison between improved initial conditions and observations shows: (i) the assimilation of the surface and upper-air data has a large positive impact on the initial conditions depending on the technique used for the objective analysis; (ii) a large decrease of the error for the meridional component of the wind V at the initial time is found, if assimilation of three-hourly data is performed by objective analysis; (iii) a comparable improvement of the initial conditions with respect to the objective analysis is found if 3D-Var is used, but a large error is obtained for the V component of the wind. Copyright © 2005 Royal Meteorological Society [source] Changes in spring weather conditions and atmospheric circulation in Estonia (1955,95)INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2003Sirje Keevallik Abstract An analysis has been undertaken at Tiirikoja Meteorological Station to investigate changes in the main weather elements in late winter and spring during the period 1955,95. The relationship between these changes and the trends in the atmospheric circulation above Estonia have also been analysed. The latter was estimated from wind speed and direction data recorded at Tallinn Aerological Station at two isobaric levels (500 and 850 hPa). These data permitted the analysts to calculate zonal and meridional components of wind velocity at both levels. Linear trends were fitted to time series of monthly averages of all parameters under consideration. The results indicate that significant changes in meteorological parameters took place in March. These changes are statistically related to the changes in the average airflow in the free atmosphere above Estonia. In March the wind speed at the 500 and 850 hPa isobaric levels increased and the average airflow turned from WNW or NW to SW or WSW. Such changes in the atmospheric circulation can only partly be attributed to the intensification of the North Atlantic oscillation. Copyright © 2003 Royal Meteorological Society [source] Mountain torques and synoptic systems in the MediterraneanTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 634 2008Joseph Egger Abstract The mountains surrounding the Mediterranean exert torques T during the passage of North Atlantic systems which affect the angular momentum of the airflow passing over and around the massifs. The Alps, the Atlas range and the orographic block of Asia Minor are selected to investigate the typical flow conditions during torque events. These mountain ranges are small enough to justify a local angular momentum analysis. Both the zonal and the meridional components of a mountain's torque (T, and T,) are used as stratification parameters in a statistical investigation of the interaction of large-scale perturbations with this mountain. How are these flows affected by the obstacle? A simple scheme is tested which attempts to interpret results. The torque analysis singles out eastward-moving large-scale systems. Their isobars are oriented from southwest (northwest) to northeast (southeast) near the mountain in zonal torque T, (T,) cases. The massifs tend to generate a low-level distortion of the pressure field such that the angular momentum of the flow over the mountain is reduced. These results can be explained within the framework of the scheme. The influence of the mountains on the pressure field is seen only at heights ,4000 m. The low-level distortions of the pressure field contribute positively to the total torque for lags ,,0 in the Alps and for all lags , 2,,,2 days in Asia Minor, where only T, is evaluated. The impact of the Atlas mountains is seen only at , = 0. Copyright © 2008 Royal Meteorological Society [source] | ||||||||||