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The principal objectives of this paper are to develop and validate an optimum interpolation method for the spatial analysis of monthly precipitation in Turkey. A two-dimensional optimum interpolation objective analysis scheme has been developed for the spatial analysis of precipitation. The model is developed for generating statistically optimum interpolation based on the irregular distribution of meteorological stations. One question that affects the optimum interpolation method and, indeed, all such techniques, is how many observations should be allowed to influence a given grid point? The method developed in this paper addresses this question. For the implementation of the method, 52 stations are considered for Turkey, with 30 years of monthly data at each point. It is observed that each monthly average spatial correlation function shows a monotonically decreasing pattern based on 15 km interval averages. The method provides high estimation accuracy in dense station locations such as in northwestern Turkey. Precipitation contour maps obtained by the optimum interpolation method indicate two spatial trends over Turkey which have not been identified in any previous study. [ABSTRACT FROM AUTHOR]

Contour maps of any meteorological variable cannot give radius or area of influences around the measurement station by considering the records at surrounding sites. The main purpose of this paper is to propose a trigonometric point cumulative semivariogram (TPCSV) concept for deciding on a spatial dependence function and then its use for regional prediction. The TPCSV provides a unique opportunity for the establishment of a regional objective prediction method whereby the radius of influence helps to predict wind velocity at any site by using the weighted averages. The spatial correlations and weightings are obtained through the TPCSV provided that the distance between two sites is known. If the slope of TPCSV is greater than 80° after some distance, then beyond this distance the regional correlation is considered as negligible. The implementation of the proposed methodology is presented for 68 wind velocity measurement stations in Turkey. The proposed method yields the least prediction error compared with other objective methodologies. It is seen that areas of influence at Central Anatolia are generally bigger than coastal areas of Turkey. [ABSTRACT FROM AUTHOR]

Temperature has a control on growth, development and yield of crops. Extreme high and low temperatures can be a limiting factor on crops. Extreme temperatures have accompanied global average temperature increase. Investigating the changes in indices derived using daily minimum and maximum temperatures may provide information about how extreme temperatures related to crop production have changed under global warming. In this sense, it is aimed in this study to investigate the climatology and monotonic temporal trends of a number of temperature-based agroclimatic indices across western Anatolia, Türkiye. The indices included number of frost days (NFD), first fall/winter frost (FFF), last winter/spring frost (LSF), frost period (FP), accumulated frost (AF), plant heat stress day (PHSD), plant heat stress accumulation (PHSA), growing season start (GSS), growing season end (GSE), growing season length (GSL) and growing degree-day (GDD). Significance of trends was assessed using Mann–Kendall test, and trend rates were quantified by Sen's slope estimator. The results firstly showed that southern low-elevation stations have the lowest frequency, intensity and duration of frost as a result of rarely occurring frost events. These stations are also characterized by the highest GDD, the earliest GSS, the latest GSE and hence the longest GSL, even with never-ending growing seasons in many years. They are also exposed to the highest heat stress in terms of frequency and intensity. On the other hand, northern high-elevation stations have completely opposite character for all indices in comparison to southern low-elevation stations. Trend analysis revealed that frequency of frost events had decreasing trends (i.e., decreased NFD), accompanied by later onset of FFF, earlier onset of LSF and hence shortened FP and decreased AF. As for growing season indices, in general, GSS occurred earlier, GSE occurred later and GSL extended. Growing degree-day and heat stress indices had substantial increasing trends, implying that, over the course of study period, the study area had more thermal accumulation and exposed to more heat stress that may hinder crop development. [ABSTRACT FROM AUTHOR]

Degree-days as a measure of accumulated temperature deviations from a base temperature have many practical applications in various human related activities such as home cooling, heating, plant growth in agriculture and power generation in addition to energy requirement. Longtemperature records are necessary for their reliable estimations at given stations. In this paper, degree-day measure has been applied tomonthly temperature records for systematically changed base temperature values from - 25 deg. C to + 35 deg. C with 5 deg. C increments at 255 meteorology stations in Turkey. The results are represented in the form of spatial degree-day distribution maps, which are then related to various climatic, meteorological and topographic features of Turkey. For instance, free surface water bodies in forms of surrounding seas, lakes and rivers insert retardation in the expansion of heating degree-days over large regions. On the other hand, cold air penetration from polar regions in the northeastern Turkey originating from Siberia appears at moderate base temperature heating degree-days. [ABSTRACT FROM AUTHOR]

Energy consumption, agricultural activities and comfort in building design are all related to temporal temperature variations. Truncationof the temperature series at a constant base temperature level leadsto surpluses and deficits as deviations. Surpluses are instances forcooling and deficits for heating. In meteorology and heat engineering these are referred to as cooling and heating degree-days, respectively. Since the temperature records are random in character their future predictions are necessary through statistical and probabilistic methods. In this paper, the degree-days are assumed to have a normal probability distribution function and therefore, their averages and standard deviations are considered sufficient for modeling cooling and heating degree-day amounts. Theoretical derivations are presented for degree-day risk calculations in their general forms and a simple implementation is given for two cities in Turkey. [ABSTRACT FROM AUTHOR]

The principal objectives of this paper are to develop and validate an optimum interpolation method for the spatial analysis of monthly precipitation in Turkey. A two-dimensional optimum interpolation objective analysis scheme has been developed for the spatial analysis of precipitation. The model is developed for generating statistically optimum interpolation based on the irregular distribution of meteorological stations. One question that affects the optimum interpolation method and, indeed, all such techniques, is how many observations should be allowed to influence a given grid point? The method developed in this paper addresses this question. For the implementation of the method, 52 stations are considered for Turkey, with 30 years of monthly data at each point. It is observed that each monthly average spatial correlation function shows a monotonically decreasing pattern based on15 km interval averages. The method provides high estimation accuracy in dense station locations such as in northwestern Turkey. Precipitation contour maps obtained by the optimum interpolation method indicate two spatial trends over Turkey which have not been identified in any previous study. [ABSTRACT FROM AUTHOR]

Wet and dry spell properties of monthly rainfall series at five meteorology stations in Turkey are examined by plotting successive wet and dry month duration versus their number of occurrences on the double-logarithmic paper. Straight line relationships on such graphs show that power-laws govern the pattern of successive persistent wet and dry monthly spells. Functional power law relationships between the number of dry and wet spells for a given monthly period are derived from the available monthly precipitation data. The probability statements for wet and dry period spells are obtained from the power law expressions. Comparison of power-law behaviours at five distinct sites in Turkey provides useful interpretation about the temporal and spatial rainfall pattern. As in temperate areas such as Turkey the rainfall amounts change mostly due to one-month-long dry or wet spells. [ABSTRACT FROM AUTHOR]

Climate is an important resource for tourism and an equally important element that needs to be included in tourism promotions. This study reveals Bursa's bioclimatological conditions. These conditions were identified by using physiologically equivalent temperature and a Climate-Tourism-Information-Scheme over 10-day periods and analyzing the mean thermal perception values that emerged. Evaluating bioclimatic conditions and meteorological parameters such as air temperature, duration of sunshine, number of wet days, amount of precipitation, and wind from the perspective of tourism will help people choose the best holiday times depending on their individual needs and circumstances. [ABSTRACT FROM AUTHOR]

Spatial and temporal patterns of trends in the diurnal temperature ranges (DTRs) of the 70 stations and the role of maximum and minimum temperatures on the year-to-year variability and the long-term trends of the DTRs in Turkey have been investigated for the period 1929-1999. The principal results of the study are as follows: (i) The daytime maximum temperatures have shown weak warming and cooling in comparison with significant warming of the night-time minimum temperatures in many regions of Turkey and in most seasons. (ii) The DTRs have significantly decreased at most of the urbanised and rapidly urbanising stations throughout the seasons except partly in winter, without showing an apparent north/south (west-east) and land/sea gradient. (iii) Annual and seasonal DTRs of some stations have shown significant increasing trends. Nevertheless, the spatial distribution of significant increasing trends in the DTR series is geographically incoherent across the country in all seasons and annually, as compared with significantly decreased DTRs. (iv) Autumn and summer DTRs have decreased generally at a higher rate than in winter and spring. (v) Changes in the temperature regime of Turkey towards the more temperate and/or warmer climate conditions are most strongly related with the significant night-time warming in spring and summer. (vi) Magnitudes and signs of correlation coefficients and correlation patterns between the DTRs and the maximum and minimum temperatures have revealed that there is an opposite physical control mechanism on the year-to-year variability and the long-term variations and trends in the DTRs, particularly for the annual, spring and summer series. (vii) Significant increases of the nighttime temperatures have most likely led to strong decreasing trends in the DTRs of most stations during the spring and summer seasons and annually and of some stations during winter and autumn. (viii) The asymmetric trends and the symmetric, but with different magnitude, trends in the maximum and minimum temperatures resulted in a significant decrease in the DTRs of many stations and are a considerable signal of ongoing changes in the climatic variability of Turkey. [ABSTRACT FROM AUTHOR]