SYNOPTIC AND ATMOSPHERIC STABILITY CLASSIFICATION FOR THE UNITED ARAB EMIRATES

Abstract

The United Arab Emirates (UAE) is a country that has developed rapidly over the past thirty years. Future development is going to be hampered by the enormous shortage of fresh water in the country. It is critically important that a strategic management plan for water resource management be developed to avoid a water crisis for the population and environment. The first step in managing water resources is to understand the sources and sinks of fresh water. Clearly, one of the most important sources of water to any environment is precipitation and the atmospheric processes and characteristics that promote or diminish the likelihood of rainfall over an area. The synoptic circulation of a region, as well as the thermodynamic structure of the atmosphere, are important for both frontal and convectively activated rainfall. In the past little detailed research has been conducted over the UAE and surrounding regions to classify and characterise atmospheric processes. This study represents the first attempt to develop a synoptic circulation climatology for the region. Synoptic circulation patterns have been classified at both the surface and 500 hPa layer over a period of seven years (1995-2001). In addition, the UAE is located under the descending limb of the Hadley circulation. As in other parts of the globe, this has severe implications for the vertical thermodynamic structure of the atmosphere. Atmospheric stability over the UAE has been evaluated for the period of seven years. The implications of descending air have been determined with respect to the thermodynamic structure of the atmosphere as a function of time and space. Vertical Radiosonde data collected over the same seven year period at the Abu Dhabi International Airport have been analysed to determine the frequency of occurrence and nature of absolutely stable layers in the atmosphere. Six circulation patterns that dominate the flow at both the surface and in the upper atmosphere at 500 hPa have been identified from the synoptic climatology. The dominant circulation pattern at the surface and upper atmosphere are the Siberian high and the Subtropical high, respectively. The Siberian high occurs at the surface predominantly during the winter season with a maximum frequency of occurrence in January (48%). The Subtropical high occurs in the upper atmosphere throughout the year, however, it is dominant during the summer months occurring 80 % of the time in August. Absolute stable layers are a permanent feature of the atmosphere over the UAE. A maximum of six layers have been identified in the atmosphere at a given time. Surface inversions occur throughout the year. Absolute stable layers have been identified at 850, 700, 600, 500 and 400 hPa. The surface inversions as well as the layers at 850 and 700 hPa have a distinctly seasonal pattern of occurrence. The absolute stable layers at the remaining pressure layers do not vary significantly with season. The surface and 600 hPa layers are by far the most dominant in the atmosphere and certainly have the most important control on vertical movement and accumulation of pollutants in the atmosphere.