Synoptic classification of lower troposphere profiles for dust days

The goal of this research is to identify meteorological characteristics distinguishing dust storm days from no-dust days. During this pioneering research, the vertical profiles of temperature, wind components, and humidity for days with dust and with no dust were compared and analyzed in order to identify features accompanying dusty conditions. Three data sets, all for the 49 year period of 1958-2006, were used. The first was the daily dust observations at Tel Aviv, Israel. The second was the eastern Mediterranean daily surface synoptic classification. The third was the vertical data over the eastern Mediterranean grid point closest to Tel Aviv at 32.5°N, 35°E. The two latter data sets were based on the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis. The meteorological parameters were averaged over the 49 year period by season, pressure level, synoptic-type, and dust and no-dust days. Prominent differences between dust 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 higher during dust episodes. This result, linking dust and humidity, looks promising for future research on connection between desert dust, ice nuclei, and precipitation. The governing eastern Mediterranean synoptic systems are low-pressure systems. For these systems, vertical velocity (Omega) values are negative. It was found that absolute Omega values were higher on dust days than on days with no dust. Southerly and westerly components of wind were found 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 dust days the lower troposphere is unstable.