Predicate Precipitation Depending on Geopotential Height Values and Positions at 500 hpa Level Over Iraq | ||
| Al-Mustansiriyah Journal of Science | ||
| Article 1, Volume 25, Issue 3, September 2014, Pages 13-20 | ||
| Author | ||
| Dheyaa A. Belal | ||
| Abstract | ||
| Precipitation happens over Iraq during the transition al seasons and in winter and this shows that the precipitation depends on the general circulation pattern. The (500 hpa) level in mid latitudes will be at height about (5600 m) when dense cold air above less dense warm air will triggers instable weather. The aim of this work is to forecast the precipitation as a basic process and choosing (500hpa) level as a guide to achieve the forecasting because it is the level of non-divergence of wind, and because it is far from earth surface to get rid of friction force that would enable us to check the upward vertical motion and downward vertical motion since the upward vertical motion causes instable condition. Data were taken from Iraqi Meteorological Organization and Seismology for the period (2002-2011) in Baghdad as central point with position (33-34)oN latitude (44-45)oE longitude. Precipitation over Baghdad is divided into three categories. The first category represents the highest recorded precipitation, the second is for arbitrary values as intermediate values and the third category is the lowest value which is less than (0.001mm). Geopotential height values were extracted from the archives of the European Center for Medium-Range Weather Forecasts (ECMWF), at 500 hpa level with a resolution of 0.75◦ × 0.75◦ grid of latitudes and longitudes of the same days of precipitation depending on the categories that were selected using the (Panoply) program. The values were carefully tested for errors. The data of the selected parameters were plotted using GrADS program for forecasting region and took the values of geopotential height and check the produced maps for two times (0600, 1200)GMT. geopotential maps gave a significant indication and the axis of trough was very useful in forecasting precipitation if it lies between Cyprus and Crete islands. The relationship between precipitation amount and geopotential height is indirect, but the value of geopotential height may be repeated while the amount of precipitation may be not with the same amount because the indicator does not belong to 500 hpa level and the geopotential height cannot create it artificially because it depends on general circulation pattern. | ||
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