The Desert Dust and its Impacts: General Considerations

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1 UNIVERSITY OF ATHENS SCHOOL OF PHYSICS, DIVISION OF ENVIRONMENT AND METEOROLOGY ATMOSPHERIC MODELING AND WEATHER FORECASTING GROUP The Desert Dust and its Impacts: General Considerations George Kallos

2 Aerosol Direct and Indirect effects Direct Effects : Scattering and absorption of solar and terrestrial radiation Indirect Effects : Polluted clouds contain more cloud droplets that are smaller in size IPCC, 2007

3 Aerosol & Radiation: Atmospheric heating due to dust 07/04/ UTC 08/04/ UTC During the day Heating inside the dust layer and Cooling beneath During the night Cooling inside the dust layer and Heating beneath

4 Εφαρµογή Ολοκληρωµένου Συστήµατος ΜΕΤΑΒΟΛΗ ΤΗΣ ΑΠΟΡΡΟΦΗΤΙΚΟΤΗΤΑΣ ΤΗΣ ΑΤΜΟΣΦΑΙΡΑΣ

5 Εφαρµογή Ολοκληρωµένου Συστήµατος ΜΕΤΑΒΟΛΗ ΤΗΣ ΘΕΡΜΟΚΡΑΣΙΑΣ

6 Εφαρµογή Ολοκληρωµένου Συστήµατος ΥΕΤΟΣ WDE NDE WDE NDE WDE NDE WDE NDE

7 Εφαρµογή Ολοκληρωµένου Συστήµατος ΕΠΙ ΡΑΣΗ ΣΤΗΝ ΑΤΜΟΣΦΑΙΡΙΚΗ ΣΤΗΛΗ 2W Ψύξη στην ανώτερη τροπόσφαιρα λόγω ανάκλασης Θέρµανση στη µέση τροπόσφαιρα λόγω απορρόφησης Ψύξη κατώτερης τροπόσφαιρας λόγω εκποµπής και εξασθένησης SW από τα ανώτερα στρώµατα Θέρµανση κοντά στην επιφάνεια λόγω εκποµπής των ανώτερων στρωµάτων και παγίδευσης υπέρυθρης ακτινοβολίας

8 Εφαρµογή Ολοκληρωµένου Συστήµατος ΕΠΙ ΡΑΣΗ ΣΤΗΝ ΑΤΜΟΣΦΑΙΡΙΚΗ ΣΤΗΛΗ 18E Ψύξη στην ανώτερη τροπόσφαιρα λόγω ανάκλασης Θέρµανση στη µέση τροπόσφαιρα λόγω απορρόφησης Ψύξη κατώτερης τροπόσφαιρας λόγω εκποµπής και εξασθένησης SW από τα ανώτερα στρώµατα Θέρµανση κοντά στην επιφάνεια λόγω εκποµπής των ανώτερων στρωµάτων και παγίδευσης υπέρυθρης ακτινοβολίας

9 Εφαρµογή Ολοκληρωµένου Συστήµατος Στη Σαουδική Αραβία Temperature model Bias MAY 2008 JUNE 2008 JULY 2008 AUGUST BIAS SKIRON BIAS WRF Temperature model Correlation Coef. CORR SKIRON CORR WRF RMSE SKIRON RMSE WRF Temperature model RMSE MAY 2008 JUNE 2008 JULY 2008 AUGUST MAY 2008 JUNE 2008 JULY 2008 AUGUST 2008

10 The integrated model RAMS / ICLAMS The development is carried out on the RAMS ver. 6 in the framework of CIRCE project It has two-way interactive nesting capabilities Explicit cloud microphysical scheme It can be nested inside of global systems It can run with configurations from a few meters horizontal resolution up to hemispheric It also includes: Detailed soil surface and water interaction processes Detailed dust cycle description Detailed sea salt cycle Gas phase chemistry module with photochemical processes Aqueous phase chemistry Gas to particle conversion and heterogeneous chemical reactions Dry and wet deposition Aerosol-cloud-radiative transfer interaction Explicit cloud nucleation scheme based on atmospheric composition It can be used mainly for case studies and scenario development related to aerosol processes and feedbacks in the atmosphere

11 JO1D Photolysis rates modeled and derived from actinic flux measurements at Finokalia on April Photolysis rates JO1D for April JO1D * 1e5 (1/sec) JO1D Model Photolysis rates JO1D for April Aerosols feedback 4 3 JO1D * 1e5 (1/sec) JO1D Model

12 JNO2 Photolysis rates modeled and derived from actinic flux measurements at Finokalia on April without dust Photolysis rates JNO2 for April JNO2 * 1e3 (1/sec) JNO2 Model with dust Photolysis rates JNO2 for April Dust feedback JNO2 * 1e3 (1/sec) JNO2 Model

13 Aerosol-Cloud Interaction Condensates (cloud,rain,ice,graupel,hail, pristine ice,aggregates) drop growth (collision, coalescence) activation Aerosol Natural and/or anthropogenic particles

14 CCN properties and an isolated cloud formation Pristine - After 80 min After 80 min run Hazy - After 80 min (g Kg -1 ) Particle distribution Model setup: 2D domain, dx=300m, 35 vertical layers Duration of runs: 6 hours Horizontally uniform initialization with a convectively-unstable profile The number of cloud droplets is explicitly calculated from the aerosol properties and the atmospheric conditions two distributions of initial CN: A. Pristine (100 cm -3 ) B. Hazy (1500 cm -3 ) Pristine - After 100 min Hazy - After 100 min Pristine - After 170 min Hazy - After 170 min Total condensates mixing ratio (g kg -1 ) for the pristine and the hazy scenarios

15 Effects of CCN on precipitation Maximum precipitation rate (mm h -1 ) for the pristine and hazy air mass scenarios. Values are taken every 10 minutes. Hourly accumulated precipitation (mm) over the domain, for the pristine and hazy CCN scenarios. Accumulated precipitation over the entire domain was 286 mm for the pristine and 215 mm for the hazy case. Most of this difference can be attributed to the inhibition of precipitation during the early stages of cloud development.

16 Effects of GCCN on precipitation A third - GCCN - aerosol mode with a median diameter of 10µm, σ=2, and total concentration=5 cm -3 has been added Adding GCCN to a hazy environment resulted in the reduction of the number of cloud droplets that nucleated. Bigger droplets were allowed to form and the rainfall during the early stages of cloud development was increased. b In contrary, GCCN did not change significantly the warm stage precipitation for the pristine environment. Adding a few GCCN for this case did not significantly change the cloud droplet spectrum because these clouds already contained a limited number of droplets which allowed them to grow fast to rain droplets. Solomos et al., ACP, a

17 Dust storms as hazardous phenomena In general, the mobilization of dust suppresses precipitation Although, this is not always the case Under certain conditions may lead in stormy weather that has as a result lightning and flooding This can be assisted by the presence of sea salt and/or anthropogenic pollution

18 Effects of airborne particles on cloud dynamics 5% hygroscopic dust 20% hygroscopic dust 5% hygroscopic dust + INx10 W-E cross-section of rain mixing ratio (colour palette in g/kg) and ice mixing ratio (black line contours in g/kg) over Haifa. Dust may act both as CCN and IN. By Increasing the percentage of hygroscopic mineral dust or increasing the ice condensation nuclei (IN) concentration by an order of magnitude, both resulted into the freezing of more particles and to the release of latent heat at higher levels. The clouds exhibited stronger updrafts reached higher tops and produced more rain.

19 The role of soot and dust as IN The aerosol particles were assumed to be either dust or soot. Increasing the amount of particles in a two-layer cloud system triggered precipitation and heavy rainfall and hailfall was produced. Further increasing the concentration of airborne particles resulted in more but smaller ice particles. The size of these elements was not sufficient to form rain droplets and precipitation was inhibited. Accumulated rainfall (mm) for various dust concentrations (red line in µg m -3 ) and black carbon concentrations (black line in µg m -3 ). Blue labels denote particle concentration in µg m -3. Total condensates mixing ratio (color palette in g Kg -1 ) and hail mixing ratio (red contours in g Kg -1 ) after 4 hours run for the case of 500 µg m -3 soot.

20 What are the Density Currents? The density currents are meso-beta/gamma mechanisms generated by the downdrafts of storms They produce dust with a mechanism that is not usually described by conventional dust cycle modeling Recent field experiments and satellite observations indicate a strong link between convective outflows and dust mobilization in certain desert areas

21 Density Currents and dust production Density currents are usually meso-beta/gamma mechanisms that produce dust clouds at various scales and environments The formation of a density current that is responsible for African dust mobilization It is the result either of deep tropical convective activity over the sub-sahel region or of orographic storms generated over the Atlas mountains (Carbone, 1982, J.Atm.Sc.) (Knippertz et al., 2007, JGR)

22 Dust production along the propagating front Mesoscale systems are dust sources by themselves due to the distinct conditions occurring

23 Generation of dust associated density currents in the Sahel region MSG/SEVIRI image over West Africa on 14 July :00 UTC

24 Generation of dust associated density currents in Middle East

25 CHEMICAL COMPOSITION OF AEROSOLS Morocco 15 August MODIS

26 CHEMICAL COMPOSITION OF AEROSOLS

27 AEROSOL NUMBER DISTRIBUTION Daily average mass concentration of aerosols from MODIS satellite (left) and from the model simulation (right) (µg/cm2) for August 16 and 27, The black areas in the satellite images are areas with no satellite data. Astitha et al., ACP 2010

28 Air quality and regional climate Aerosol number distribution: Location: South of Canary Islands (16 August 2005) 5,0 km Vertical Profile P :00-8:00UTC 5,0 km Vertical Profile P :00-8:00UTC 4,0 3,0 Aitken Mode Diameter: µm Units:parts/cm 3 CRST (*1500) DSO4 (*100) PSO4 (*1500) NA (*100) 4,0 3,0 Accumulation Mode Diameter: µm Units:parts/cm 3 CRST (*200) DSO4 PSO4 (*100) NA (*10) 2,0 2,0 1,0 1,0 0,0 0,00 0,20 0,40 0,60 0,80 1,00 1,20 0,0 0,00 0,20 0,40 0,60 0,80 1,00 1,20 CWC(g/m3) CRST_1 DSO4_1 PSO4_1 NA_1 CWC(g/m3) CRST_2 DSO4_2 PSO4_2 NA_2 5,0 km Vertical Profile P :00-14:00UTC 5,0 km Vertical Profile P :00-14:00UTC 4,0 3,0 Aitken Mode Diameter: µm Units:parts/cm 3 CRST (*1500) DSO4 (*100) PSO4 (*1500) NA (*100) 4,0 3,0 Accumulation Mode Diameter: µm Units:parts/cm 3 CRST (*200) DSO4 PSO4 (*100) NA (*10) 2,0 2,0 1,0 1,0 0,0 0,00 0,20 0,40 0,60 0,80 1,00 1,20 CWC(g/m3) CRST_1 DSO4_1 PSO4_1 NA_1 0,0 0,00 0,20 0,40 0,60 0,80 1,00 1,20 CWC(g/m3) CRST_2 DSO4_2 PSO4_2 NA_2 Astitha et al., ACP, 2010

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30 Aerosol impact on health Aerosol particles are responsible for causing great harm to human health. They can cause breathing and respiratory problems, irritation, inflammation and cancer.

31 Aerosol impact on health Fine particles penetrate deep into the lung (Alveolar region AI), while coarse particles (diameter greater than 1µm) are deposited in the upper respiratory system (Extrathoracic region ET) Drossinos, Y. and Housiadas, C., Aerosol Flows in The Multiphase Flow Handbook (2005).

32 Working Issues Dust and sea salt particle production mechanisms Mapping of dust production areas, dust composition (spatial distribution) Better understanding of local phenomena such as density currents in arid areas Further exploitation of the remote sensing information and intercalibration with models and other data sources Heterogeneous processes on dust and sea salt particles Nucleation and condensation processes The role of bacteria on dust and sea salt particles on nucleation and condensation processes