Synoptic classification of lower troposphere profiles for dust days

摘要

The goal of this research is to identify meteorological characteristics distinguishing duststorm days from no-dust days. During this pioneering research, the vertical profiles oftemperature, wind components, and humidity for days with dust and with no dust werecompared and analyzed in order to identify features accompanying dusty conditions. Threedata sets, all for the 49 year period of 1958-2006, were used. The first was the daily dustobservations at Tel Aviv, Israel. The second was the eastern Mediterranean daily surfacesynoptic classification. The third was the vertical data over the eastern Mediterraneangrid point closest to Tel Aviv at 32.5°N, 35°E. The two latter data sets were based on theNational Centers for Environmental Prediction/National Center for Atmospheric Researchreanalysis. The meteorological parameters were averaged over the 49 year period by season,pressure level, synoptic-type, and dust and no-dust days. Prominent differences betweendust and no-dust days were found for relative humidity and wind components during fall,winter, and spring at 700, 600, and 500 hPa levels. Relative humidity was found to be higherduring dust episodes. This result, linking dust and humidity, looks promising for futureresearch on connection between desert dust, ice nuclei, and precipitation. The governingeastern Mediterranean synoptic systems are low-pressure systems. For these systems, verticalvelocity (Omega) values are negative. It was found that absolute Omega values were higheron dust days than on days with no dust. Southerly and westerly components of wind werefound to have higher values during dust days. It was found that for most synoptic systems,temperature below the 700 hPa level was equal or higher during dust days. Thus, during dustdays the lower troposphere is unstable.