نشریه نیوار
پیاپی 68-69 (بهار و تابستان 1387)

Though plant growth and development is a function of genetic characteristic but the effects of weather factors are important as well. Since weather factors have complicated relationship with plant growth and development stages. Each stage of plant growth should receive optimum temperature and growth degree days (GDD) to enter to the next stages. Therefore sowing date, intercultural operations and growth period should be adjusted in order to match with plant development optimum conditions. Thus, phonologic stages of wheat (Tajan variety) were studied in Hashemabad agrometeorological Research Station in Gorgan city in 2003-2004. Results showed that during emergence period plants did not received enough rainfall to fulfill uniform germination. In tailoring period the plant were faced with shortage of light and rainfall and also temperature in emergence and stemming periods was less than optimum. Reducing of temperature in these periods was caused of spike and spikelet initiation. Also necessary temperature for leaf appearance was not supplied. On the other hand increasing of temperature was caused thermal tension in periods of pollination and grain filling resulted reduction of grain weight and yield.

In this research, a method of securing water by using source potential water and local expense is introduced. This method is one of the water harvesting and runoff surface methods. Because of ever-increasing water crises, It uses more than the other ones. In this paper, the main aspects of this execution plan, such as property space, hydrological calculation and assessment economic are considered and discussed, as a case study in Mashad. In addition, an execution pattern of this plan was shown and presentation in Kashmar. This paper emphasized a design for securing water by lower expenses that can be superseding for preparing and providing water especially for green space and decreasing the urban flood effects. The most important characteristics of this plan are, taking advantage of the chances and the challenges (such as runoff) in an area for optimum benefit and convert theses challenges to effective aspects, determining the best area for reserving and transferring the accumulated water. This study in Mashad and this execution plan in Kashmar could be attention as a pattern for similar execution plans. By especial methods for other similar areas can secure water via establishing suitable storage and decreeing runoff and flood destruction effects in urban area.

Potential vorticity (PV) which depends on relative vorticity and static stability in each latitude is a useful quantity in analyzing the synoptic systems at middle latitudes. Since PV does not depend on moisture field, it is not useful for determining the trajectory of moist synoptic systems such as those affecting south of Iran during the winter time. To diagnose the movement of such systems it is possible to use equivalent and we-bulb PV which depend on specific humidity through equivalent and wet-bulb potential temperature respectively. In this study the NCEP/NCAR reanalyzed datasets is used to calculate the equivalent and wet-bulb PV for two synoptic cases affecting south of Iran. Results show that small and negative amount of equivalent and wet-bulb PV aggress well with the location of low pressure systems at the surface. Also, it is seen that the pattern of equivalent and wet-bulb PV are similar except that the value of equivalent PV is larger than that of wet-bulb PV.

Understanding of the nature of considerable height variations of wind in the atmospheric boundary layer has an important role on wind turbines design. Since, generally aero generators hub are located at the upper level of the wind vector measurement standard level, to estimate the wind power potential at proposed level, the wind shear should be calculated. In this paper, some methods such as the suggested method by Justus and Mikhail (JM) and also the 1/7 power law has been examined to estimate and vertical extrapolation of mean wind power density. By the JM method the Weibull wind speed distribution parameters, have been vertical extrapolated. This technique is useful only for ensemble averages, and leads to large errors in individual cases. The 1/7 power law method usually gives conservative but reasonable estimates of wind power, except where the roughness of the site is large compared to the height of the reference level. To present the implementations of those methods, first the hybrid-Weibull distribution parameters of hourly averaged wind speeds of east Isfahan synoptic station, during the 1992-2005, have been calculated and then the mean wind power density at that site have been estimated. The 1/7 power law method, is the most convenient method to estimate mean wind power density. But this method doesnt always apply properly and is just a guide. Yet in the absence of actual measurement, the 1/7 power law is a reasonable, if sometimes conservative, approximation.

In this paper, precipitation variation and change has been described based on 92940 observed data of monthly precipitation during 1961-2003 all over the country and by geostatstic technique. Data analyses has done by GIS logic and software in order that some statistic such as coefficient of variation, skewness, kurtosis and long term trend overlaid and has achieved a changevariation map. In this map three regions is shown; one region that have no statistical significant change by 58.3 percent of country. The second is the high variation low extends region and finally low variation high extends region that covered about 41.7 percent of Iran.