Long-term Trends and Spatio-temporal Variations in Atmospheric Aerosols at UFS (TP I/02)

Transcription

1 Long-term Trends and Spatio-temporal Variations in Atmospheric Aerosols at UFS (TP I/02) Jia Sun 1, Markus Hermann 1, Ludiwg Ries 2, Wolfram Birmili 2 and Alfred Wiedensohler 1 1 Leibniz Institute for Tropospheric Research, Leipzig, Germany; 2 German Federal Environment Agency (UBA), Germany.

2 SP I /02 Networking in VAO-II SP I /02: Investigating the climate efficiency of atmospheric aerosols considering possible changes of transport patterns on the basis of the 10-year aerosol time series R&D Projects AP I: Atmospheric Variability and Trends R&D Projects AP II: Alpine Environment: Dangers and Risks R&D Projects AP III: Alpine Water Supply SP I/01 SP I/02 SP I/03 SP II/01 SP II/02 SP II/03 SP III/01 SP III/02 SP III/03 SP IV ALP DAZ 2/34

3 Introduction 1. Aerosol particles are relevant for both climate and human health effects. Climate-relevant effects -- particle interactions with clouds and solar radiation (direct and indirect aerosol effects) Health effects -- penetrate deep into the human body after inhalation. 2. Aerosol measurements at Schneefernerhaus (UFS) can be considered as representative of a large scale over Central Europe. UFS is located around 300 m below the Zugspitze summit. Both polluted air from the lower troposphere and less polluted air from the free troposphere can be detected here. Henne et al. (2004) 3/34

4 Instruments CPC particle number concentration (PNC), SMPS particle number size distribution (PNSD) are continuously measured at UFS. CPC particle number concentration is measured by a Butanol CPC (TSI model 3772) from 2007 to PNSD is measured by a particle mobility size spectrometer (SMPS, TSI model 3936) since SMPS PNC in cm -3 4/34

5 Outline 1 Temporal variation of atmospheric aerosol at UFS 2 Long-term and large-scale trends transport of atmospheric aerosols 3 Spatial variability of the PNC on the synoptic scale 5/34

6 Particle number concentration (PNC) metrics N[25-60 nm]: Nucleation mode New particle formation; traffic Local scale N[ nm]: Accumulation mode Traffic (diesel) Regional scale dn/dlogdp in cm N[ nm]: Accumulation mode Aged accumulation mode particles (also involves cloud processing) Synoptic scale N[ nm]: Aitken mode Traffic (diesel) Aged nucleation mode particles Local scale Dp in nm 6/34

7 Annual variation of PNCs 1 New particle formation at all sites 2 Higher PBL height influenced aerosol at UFS 3 Higher PBL height more vertical dilution 4 Higher PBL height more pollutant Aerosols at UFS are mainly influenced by free troposphere during winter and by injected air parcels from planetary boundary layer (PBL) during summer.

8 Outline 1 Temporal variation of atmospheric aerosol at UFS 2 Long-term and large-scale trends transport of atmospheric aerosols 3 The variability of the PNC on the synoptic scale 8/34

9 Long-term trends at UFS ( ) Decreasing trends of PNCs are detected at UFS, relative slopes vary from -3.5% to -2.1%. * Trends are significant at α = (method: Customized Sen-Theil trend estimator)

10 Trends in background & contaminate periods Less pollutant aerosols were transferred to UFS by PBL. Based on the radon baseline recognition method by Esther, whole time period are divided into background period (Free Troposphere influenced) and contaminate period (PBL influenced).

11 Mixing layer height changes The mixed boundary layer height has reduced, this could be a reason for decreasing particle number concentrations. Q: Besides PBL height change, what are other possible reasons for PNC decreasing trends?

12 Outline 1 Temporal variation of atmospheric aerosol at UFS 2 Long-term and large-scale trends transport of atmospheric aerosols 3 Spatial variability of the PNC on the synoptic scale (tentative results) 12/34

13 Back trajectory cluster analysis (BCLM) Back-trajectory cluster method (BCLM), by W. Birmili back trajectory pseudo-potential temperature PM10 concentration Database: HYSPLIT Period: 96h CS = Cold Season TS = Transition season WS = Warm Season ST = Stagnant A = Anticyclonic C = Cyclonic 13/34

14 Mean concentration levels at UFS N[ ] at UFS N[ ] (cm -3 ) 1. PNCs are higher in summer and lower in winter. 2. PNCs are higher under Anti-cyclonic condition. 3. Origin region, residence time also influence the PNC levels. Q: Under which weather condition, does PNCs change?

15 Conclusion 1. PNC temporary variation at UFS Aerosols at UFS are mainly influenced by FT during winter and by injected air parcels from PBL during summer. PNCs decreased at UFS since PBL height changes would be one of the potential drives to explain decreasing trends. 2. PNC spatial variation on synoptic scale Back trajectory classification is an efficient way to explain the spatial variation of PNCS, especially accumulation mode particles. PBL height, weather condition (anti-cyclonic) are two main drivers which influence PNC levels on synoptic scale. 15/34

16 Working plan Part 0: Complete SMPS data set; Progress: Finish Progress: Finish Part II: Aerosol climatology and PBL influence at UFS on synoptic scale Part I: long-term ( ) trends and possible reasons Progress: Preliminary results 16/34

17 Thanks!

18 Temporary variation of PNCs To have a better understanding of the PNC at UFS, two other mountain sites and one rural background site from German Ultrafine Aerosol Network (GUAN) are involved: Melpitz: is located in eastern Germany, ca. 50 km northeast of Leipzig. Measurements at Melpitz are representative for the Central European background atmosphere. Schauinsland : is located at 1205 m a.s.l. near the Schauinsland peak in the Black Forest in south-western Germany. Melpitz Hohenpeissenberg (MOHp): is located on a solitary hill about 980 m a.s.l. in the rural countryside of southern Bavaria, approximately 40 km north of the Alpine mountain range. Schauinsland Hohenpeissenberg Zugspitze 18/34

19 Trends in high temperature days (daily max temperature > 5 C, > 0 C, > -5 C)

20 Trends at UFS and other sites ( )

21 Introduction 1. Aerosol particles are relevant for both human health and climate effects. Climate-relevant effects include particle interactions with clouds and solar radiation, which are commonly classified into direct and indirect aerosol effects Health effects of ambient aerosol particles are linked to their ability to penetrate deep into the human body after inhalation. 2. The aerosol measurements at Schneefernerhaus (UFS) can be considered as representative of a large scale over Central Europe. UFS is located around 300 m below the Zugspitze summit. It occupies a special position, because both polluted air from the lower troposphere and less polluted air from the free troposphere can be detected here. 21/34

22 Mean concentration levels at UFS N[ ] N[25-100] N[ ] (cm -3 ) N[25-100] (cm -3 )

23 Air mass frequency changes ( ) Tentative results

24 Night-time [00:00-04:00] and day-time [12:00-16:00] trend PNCs decrease more during day-time (PBL influenced period). Less pollutant aerosols were transferred to UFS by PBL. * Trends are significant at α = 0.95

25 Long-term trend analysis method We need a trend analysis method that is Robust against outliers Insensitive to seasonal bias Customized Sen-Theil trend estimator (Median slope) 25/34

26 Long-term trend analysis method 1. Basic Criteria Different year Same season Same weekday Same hour Additional Criteria Particular month T > T 0 Particular Hour.. 2. Significance test probability distr. median(slope i ) 26/34 slope