Heavy Dust Storm Research Articles

A jet stream associated heavy dust storm in the western Mediterranean

Examination of the dynamical structure of a heavy dust storm event over the western Mediterranean revealed an almost exact coincidence of the western boundary of the dust plume with a cold front and a significant jet stream. A confrontation was found between the dry desert air mass associated with a notable downward flowing jet stream and the moister Mediterranean air mass. Vertical cross sections across and along the dust plume indicated that the high mountain Ahaggar region over the Sahara was probably the source of dust, which was transported northward more than 2400 km and washed out by heavy rainfall.

The chemical composition of aerosols settling in Israel following dust storms

The chemical composition of settling particles from 23 heavy dust storms in Israel has been determined. These storms occurred over a 20-year period in Jerusalem and Ramat Hasharon, north of Tel Aviv. Meteorological conditions during the storms were examined and the storms classified according to their trajectories into two types: (a) North African; and (b) Arabian Desert. The North African type is by far the most common. The composition of the dust storms is monotonic. Additional interpretation of the chemical analyses using Enrichment Factors reveals the following points. (1) The settling particles are relatively enriched in Ca probably from the local terrain and in Cl derived from the Mediterranean Sea. They are also enriched in S for unexplained reasons. Other elements enriched include Pb and Br and these are presumably due to contamination from the use of leaded petrol. (2) Comparison of the two types of dust storms shows that the Arabian Desert type contains less Cl and U. The composition of an Israel Background Reference Standard is suggested for use in future ecological studies of settling particles in Israel.

The composition of clay minerals transported to Israel as indicators of Saharan dust emission

Ambient particles, following dust storms originating in the Saharan region as identified by meteorological analysis of synoptic maps, satellite pictures and back-trajectory calculations, transported over Israel, were collected and analysed. In studies of 28 heavy dust storms originating in the Saharan region, during a 22 year period (1967–1988), clay mineral analysis provided information about the characteristics of dust particles transported over Israel. Relatively high concentrations of montmorillonite and mixed-layer minerals were found in the particles when the storms originated on the western deserts of the Tibesti mountains. Following storms that originated in Saudi Arabia, Jordan and the Dead Sea deserts, the dust particles contained a high percentage of palygorskite. Following storms that originated in the Chad, Lybian plateau deserts and the Great Sand Sea of Ahaggar Massif, predominantly high concentrations of illite was found in the ambient particles in Israel. These data indicate that ambient particles in Israel following dust storms originating in the Saharan region may be characterized by their mineral content.

Ground-based television patrol of Martian cloud formations in 1969 and 1971–1972

Particular advantages of T.V. techniques for planetary observations are: high quantum efficiency, possibilities for registration of features with low contrasts, and convenient control of seeing. The photometric accuracy of T.V. pictures was found to be about 6–8%. When Mars was surveyed by Mariner 6 and 7 our groundbased T.V. photos showed the existence of bright cloud formations over northern polar regions and over the Hellas-Ausonia regions. About 50 000 T.V. pictures have been obtained in ten spectral regions (370–760 nm) during the period of August 1971 to January 1972. Television observations showed that the date of initiation of the global dust storm was September 12 when two red clouds appeared in the Hellespontus and Moab regions. For a period from about the middle of October to November 25 all surface features were obscured by a heavy dust storm. The general decline of the Martian dust storm was followed by the appearance of local dust clouds.

放射伝達に及ぼす火星大気中のダストの効果(その1)

The equations of infrared radiation transfer are numerically solved for the Martian atmosphere, with consideration of the effect of dust, which absorbs, emits and scatters light. Primary mineral constituent of dust, we assumed, is quartz. Three cases on dust concentration are considered: the first corresponds to a heavy dust storm event, the second to a dusty case and the third to out-of-storm case. From the solutions obtained by the method of an iterative numerical integration, radiative heating or cooling rates in the atmosphere are calculated as a function of height.The computation results show that on Mars, the infrared radiative cooling rates due to dust cannot be overlooked in the lower levels within dusty atmosphere. Especially, at a dust storm event, cooling in the infrared regions would be a very important term as well as heating due to absorption of the incident solar radiation by dust, and the thermal structure of the Martian atmosphere seems to be determined by dust alone. Our result also indicates that even at out-ofstorm events, cooling rate due to dust seems to have the same order as the magnitude of infrared radiative cooling due to CO2.