Evaluation of weather station network in Jordan

Abstract

Ce travail consiste en l’étude de la distribution des stations météorologiques en Jordanie selon le standard de l’organisation mondiale de la météorologie par l’utilisation de la moyenne journalière des températures minimum et maximum dans 35 stations. L’objectif est de montrer l’importance de l’optimisation de cette distribution pour une meilleure utilisation des données météorologiques. Le pays a été partagé en 18 zones en tenant compte de l’homogénéité topographique. L’analyse paramétrique de la moyenne journalière des températures minimum et maximum a été effectuée durant la période 1999-2001. Il en ressort que la densité du réseau en Jordanie a atteint 0.6 stations/1000Km². La distance entre les stations du réseau jordanien atteint en moyenne 115 Km. L’évolution des températures maximum (minimum) a généré 5 (11) paramètres qui ont permis d’élucider à 92% (99%) les variations enregistrées. L’application de l’analyse polynomiale en utilisant la saturation des paramètres obtenus par l’analyse paramétrique fait apparaître 10 zones météorologiques en Jordanie. En revanche, la régression linéaire de la relation entre la disposition des stations et les distances qui les séparent ne montre pas une relation directe. Il est déduit que la variation de température seule ne peut pas permettre de différencier les zones météorologiques. En effet, l’altitude et le relief constituent également des paramètres déterminant. L’étude a montré que le nord-ouest de la Jordanie est la région la plus complexe, nécessitant une plus grande couverture par les stations, suivie par les régions centre et sud. Il a été montré également que les zones où la pluviométrie dépasse 200mm sont suffisamment couvertes. L’étude recommande d’une part l’installation de 3 nouvelles stations à oued Araba, sur les rives est de la mer morte et enfin au sud-est du pays, et d’autre la suppression de 25 stations dans les régions où la densité de couverture est élevée.

Mots clés: Jordanie; station météorologique; zones climatiques; analyse paramétrique; régression linéaire.

This study aims to evaluate weather stations distribution in Jordan according to the World Meteorological Organization (WMO) criteria; using the daily average maximum and minimum temperatures in 35 climatic stations. Signifïcance of this study lies in highlighting the importance of weather stations distribution on areas of Jordan, which enables researchers utilize climatic statistics available there in applied climatological studies. Some areas in Jordan suffer from rareness of such stations while other such as the northern and middle areas, enjoy intensity of climatic stations. This study depended on dividing Jordan, according to geographical homogeneity, into 18 geographical areas. Factor analysis was applied on the maximum and minimum daily average temperatures in 35 climatic stations during the period 1999 to 2001. Loading factors resulting from the analysis of the climatic stations allowed determining the homogeneous climatic areas. Cluster analysis was also applied on results of the factor analysis of similar station compounds for one cluster after determining the stations of each cluster; then each cluster was mapped by a line determining approximately the climatic region borders. A table of homogeneous climatic stations was prepared; associated with the area, number of stations along with sufficiency or rareness reference in each region according to the WMO criteria which is one station per 1000 km². Correlation coefficient among the stations was calculated according to maximum and minimum temperatures. These coefficients were used in a simple regression pattern among distance between stations and their correlating coefficients. This study showed that intensity of the weather station network in Jordan was 0.6 stations per 1000 km²; however, these stations were not fairly distributed. The desert area seemed void of climatic stations; the northern area had 4 stations per 1000 km²; whereas the southern and middle zones showed fair station distributions. The Jordanian weather stations’ network is considered reasonable in comparison with other countries, since the average distance between the climatic stations is 115 km in Jordan and 155 km in Turkey. However, it is 35 km in New Zealand and 28 km in Ireland. Maximum temperatures highlighted 5 factors through applying factor analysis. These factors explained around 92% of the variance values of maximum temperatures<; On the other hand, minimum temperatures showed 11 factors, which explained 99% of variance existing in minimum temperatures; i.e., minimum temperatures were better to utilize than maximum temperatures in distinguishing the climatic regions in Jordan. Based on factor loading analysis, it is found that 10 climatic areas representing climatic regions describe correctly the whole country. No statistically significant correlation was found when applying simple regression between the stations (depending on the max and min temperatures) and distances among stations. This means that the parameter distance among the stations was not an indication to distinguish climatic regions in Jordan. This finding emphasizes that temperature alone cannot precisely distinguish the climatic regions. There must be other factors as important as temperature, such as altitude or other geographical features which should be considered. The study showed the southwestern corner of Jordan was the most geographically complex region; hence, it needs high intensity of climatic stations. However, the next is the middle then the desert areas. It also showed that 8 areas have too many climatic stations. The number of stations, in areas with an average rainfall exceeding 200 mm, is considered as sufficient. In addition, eastern desert areas were considered in need for additional climatic stations. The study suggests establishing three more stations: in Arabah Valley, the second on the eastern coast of the Dead Sea and the third in the south-eastern corner of Jordan. The study recommends disestablishment of 25 stations in intensive areas and transference of the power in these extra stations into establishing new research studies to evaluate the rain weather stations network.

Keywords: Jordan; climatic station; climatic areas; parametric analysis; linear regression.