Land use change suppresses precipitation

Transcription

1 Land use change suppresses precipitation W. Junkermann, 1 J. Hacker, 2 T. Lyons 3 and Udaysankar Nair 4 FZK, IMK-IFU, Garmisch- Partenkirchen, Germany 1 Airborne Research Australia, Flinders University, Adelaide, Australia 2 Murdoch University, Perth, Australia 3 National Space Science Technology Center, Huntsville, Alabama, USA 4

2 Outline Background Experimental setup Results Summary

3 RAINFALL Bates et al. Climatic Change, 89, 28, RUNOFF DROUGHT IN WESTERN AUSTRALIAN WHEAT BELT FORSCHUNGSZENTRUM KARLSRUHE IMK-IFU

4 Precipitation change distribution -clouds over natural vegetation + - IOCI, 22

5 The BUFEX experiment 12/26, 8/27 airborne investigations in a natural laboratory comparing meteorology and aerosols 2 seasons homogeneous landscape <- 1 km 4 km -> > 8 km Lake King Airstrip ~25 km ->

6 Background Experimental setup Results Summary

7 AUSTRALIA BUFEX CAMPAGNE, 26/27

8 AUSTRALIA BUFEX CAMPAGNE, 26/27 GRIMM SMPS, nm 2 min GRIMM 1.18, 3 nm 15 um 6 sec TSI 31 > 1 nm 2 sec FSSP um 1 sec Meteorology (temp, dewpoint) and radiation parameters (radiation balance, albedo)

9 Background Experimental setup Results Summary

10 PARTICLES > 1 nm (red) ALTITUDE [m] WEST ~ NUMBER OF PARTICLES TSI CPC COUNTS PBL 4 km NO nm-size PARTICLES OVER THE FOREST!!! VERTICAL MIXED UP TO PBL ALTITUDE [m] EAST PBL 1 2 NUMBER OF PARTICLES

11 PARTICLES > 1 nm (red) km NO nm SIZE PARTICLES OVER THE FOREST!!! SIZE DISTRIBUTIONS (dn/dln(dp) [/cm 3 ] WEST ultrafines Channel [nm] (dn/dln(dp) [/cm 3 ] EAST Channel [nm]

12 PARTICLES > 1 nm (red) (dn/dln(dp) [/cm 3 ] Channel [nm] 4 km - INDEPENDENT FROM SEASON -NO DEPENDENCE ON VEGETATION ON AGRICULTURE (dn/dln(dp) [/cm 3 ] SIZE DISTRIBUTIONS OVER THE AGRICULTURE Channel [nm]

13 SOURCE REGIONS FOR NUCLEATION- PARTICLES SUMMER WINTER

14 a (dn/dln(dp) [/cm 3 ] c (dn/dln(dp) [/cm 3 ] Number Size Distribution 11: New particle production Channel [nm] Number Size Distribution 14: aged new particles CCN Channel [nm] Particle Diameter (nm) b (dn/dln(dp) [/cm 3 ] d Number Size Distribution 1 : 6: 12: 18: 24: east / morning + afternoon Channel [nm] LAKE STUBBS

15 NUCLEATION AEROSOL EFFECT ON PRECIPITATION -> HIGHER DROPLET NUMBER AND REDUCTION OF DROPLET SIZES DUE TO ENHANCED CCN (FLETCHER, 1962, Lohmann and Feichter, 25.) ALTITUDE [m a.s.l.] E W E HORIZONTAL W CCN [/cm3] PARTICLES > 1 nm [/cm3] CCN as particles > 5 nm

16 CLOUDS OVER BOTH AREAS, CLOUDS OVER BOTH AREAS, Experimental proof

17 NUMBER OF DROPLETS [/cm3] a WEST NUMBER OF DROPLETS LIQUID WATER CONTENT EAST :45 4:15 4:45 5:15 5:45 UTC UTC diff 8 h LWC [g/m3] METEOROLOGIC DIFFERENCES

18 NUMBER OF DROPLETS [/cm3] CCN 4/cm3 WEST Number of droplets per size bin WEST NUMBER OF DROPLETS LIQUID WATER CONTENT EAST Droplet size (diameter) [um] EAST UTC diff 8 h CCN 28/cm3 LWC [g/m3]

19 Parameter Temperature (air) [ o C] Pressure [hpa] Dewpoint [ o C] West (agriculture) East (natural vegetation) ground cloud base ground cloud base Water [g/m3] CCN Cloud droplets [/cm3] ~ 4 ~ Average diameter [um] Liquid water content [g/m3].1.15 Note the difference of water vapor converted into LWC

20 Background Experimental setup Results > Landuse change Summary

21 SOURCE REGIONS FOR NUCLEATION- PARTICLES SUMMER WINTER

22 DIFFERENCES BETWEEN THE LAKES? MOIST DRY High GROUNDWATER TABLE low ~ 2 m > 2 m

23 DIFFERENCES BETWEEN THE LAKES? MOIST DRY High GROUNDWATER TABLE low ~ 2 m DEFORESTATION > 2 m

24 SUMMARY Enhanced ultrafine particle numbers over agriculture Nucleation source not related to vegetation Salt lake chemistry / emissions, most probably halogen (iodine?) chemistry Enhanced CCN numbers affect cloud microphysics Modification of cloud microphysics can explain the observed precipitation patterns

25 Long term experiment, natural laboratory Deforestation >rising ground water table (GWT) ->GWT close to surface ~ 197 ->wet chemistry in salt lakes ->increased number of CCN -> ->reduction of precipitation

26 Acknowledgement Admiral James Stirling Settlers who helped clearing the forest National Science Foundation grant ATM and Australian Research Council's Discovery funding scheme (project DP664515) One of the aircraft was donated by the late Ms. Joyce Schultz

27 Thank you for your attention 1827

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29 NUMBER OF DROPLETS [/cm3] ALTITUDE [m a.s.l.] NUMBER OF DROPLETS LIQUID WATER CONTENT :45 4:15 4:45 5:15 5:45 UTC UTC diff 8 h a DEWPOINT WEST b c d 3 6 CCN [/cm3] EAST DROPLETS [/cm3] LWC [g/m3] CLOUD BASE EAST WEST