NKFIH KH130337 Granulometric analysis of recent Saharan dust - Summaries
Summary of the research and its aims for experts
In the course of the proposed research, complex grain size and grain shape analysis of samples extracted from the annually emitted hundreds of millions of tonnes of Saharan mineral dust will be achieved. The collection of samples is based on our previous studies on possible source areas (e.g. Western Sahara; Atlas foreland: Chott Melrhir and Chott Jerid), relatively close proximity of sources (Canary Islands; Antikhytera; Crete), and remote regions (Alps; Carpathian Basin).
By using the automated static image analysis granulometry, we are able to obtain direct grain size and grain shape information on the investigated minerals completed with light transmittance and Raman-spectra (correlated with mineralogy) of the particles. The exact determination of size and shape parameters of irregularly shaped, anisotropic mineral particles is already a key issue in many scientific fields (e.g. sedimentology, geomorphology, atmospheric physics and chemistry, aerobiology), however the accurate answers to these questions are still missing. As part of our proposed project both the size and shape of particles, both their dependence on origin, transport and sedimentation will be explored. So, we could also monitor the changes of environmental conditions by analyses of these parameters.
What is the major research question?
In our research, we will determine by direct methods the particle size and particle shape, main mineralogical character and optical properties of dust material deflated from Saharan source areas. The synoptic meteorological background, transport mechanism and mode of deposition, as well as correlations of these processes with granulometric characteristics would also be defined.
We will also investigate the further possible application of the size and shape parameters gained by automated static image analysis in a deeper understanding of dust transport and deposition processes. Since both the geological and geomorphological characteristics of source areas, the mode and distance of transportation both the deposition mechanisms have an effect on the sampled mineral particles, we will apply multivariate mathematical-statistical methods to determine the weighting scores of different factors in formation of individual granulometric fingerprint. As a result of environmental changes, each of these factors may change over time, so it is more important to know the effects of all these factors.
What is the significance of the research?
Our preliminary results have shown that theoretically obtained, remote sensed and indirectly measured grain size data of Saharan are contradictory and incomparable with the direct results of our automated static image analyses. Consequently, the usage of these previous data causes problem in (1) the determination of quantity of transported dust material and (2) the mass of deposited mineral particles; (3) the deeper understanding of mechanisms of dust transportation; and (4) the determination of effects of dust on climatic, cloud physical and other environmental processes.
Precise and accurate granulometric properties serve as important input data for dust transport and deposition models to help partially eliminate the identified underestimation of deposition of numerical simulations.
Changes in atmospheric circulations through the effects of current climate change can be well observed in the Sahara dust transport processes, especially in the case of North African dust transport to Europe and, consequently, to Hungary. Arctic amplification due to increased warming in Arctic regions influences high-altitude jet-streams, which have higher north-south amplitudes and slower east-west propagation leading to more frequent development of cold drops and longer stationary meridional flow situations. As a consequence, intense and prolonged dust storm situations develop, the seasonal distribution of which also changes; it has been observed also in recent years that the number of episodes in winter and at the beginning of spring is increasing.
Similar examination of aeolian dust particles has not been done so far, and we have only partly dealt with such determination of granulometry of recent dust material. That is why we will be the first to provide detailed direct grain size and grain shape information on Saharan dust particles.
Summary and aims of the research for the public
Billions of tons of mineral dust that is emitted every year through dust storms into the atmosphere are important part of our climatic and environmental system: mineral dust affects the amount of solar radiation reaching the surface; has an effect on aerobiological processes, cloud formation, soil development, health situation. Nevertheless, the level of our scientific knowledge of dust cannot be considered satisfactory. We do not have sufficiently accurate data on (1) the amount; (2) grain size; and (3) mineral composition of Saharan dust transported towards Europe. The inadequate appearance of these three factors makes both the reconstruction and interpretation of past events and estimation of direction and potential effects of future changes difficult and inaccurate.
In the course of our research, we would like to analyse the grain size and previously not investigated grain shape of Saharan dust from source to distant settling regions. All these will be completed with mineralogical analyses, time series derived from satellite images and measurements, synoptic meteorological background and air-mass trajectories, providing fundamental new data about Saharan dust events affecting our country as well as about key properties of mineral dust material. All these data and information would lead to a deeper understanding of the potential impacts of current climate change and to more accurate knowledge if past environmental processes.