ACI in deep and ice clouds or Where is the missing warming?

1. ACI in deep and ice cloudsorWhere is the missing warming? By Daniel Rosenfeld MarkkuKulmala, Ulrich Pöschl, AvichayEfrayim, Oliver Lauer, Ramon Braga, Federico Bianchi, TuukkaPetäjä, Douglas Worsnop, Minghuai Wang, Cheng Yuan, Feiyue Mao, Shocai Yu, Zhanqing Li

2. ACI forcing from low clouds grossly underestimated, because: • Drop concentrations was not retrieved in broken clouds, where most needed. • AOD is blind to low CCN, where most needed. • Observations reversed cause and effect. • Radiative convective equilibrium (RCE) is inherently buffered, but RCE is rarely reached. • Tuned down aerosol suppression of rain for avoiding too much cooling from low cloud. • Misinterpretation of volcanic perturbations. A Likely explanation is compensation by positive forcing from deep & cirrus clouds

3. reff threshold for triggering warm rain rthresh= 6.0 mm rthresh= 8.2 mm rthresh= 10.6 mm “Simulated temperature trend best matches to observed trend when the model adopts the threshold radius that worst reproduces satellite-observed microphysical statistics and vice versa.” Suzuki et al., GRL 2013

4. MIROC5.2(KK00): Aerosols rain suppression fit to CLOUDSAT X6 cooling compared to IPCC !!! Dismissed. If accepted, world should have cooled! OR: Missing aerosol warming by deep and/or ice clouds Jing and Suzuki, 2018

5. Climate Sensitivity,  Ts = The change in equilibrium surface temperature due to radiative forcing (RF) 5

6. Rosenfeld et al., Science, 2008 Colder and wider anvils radiate less IR energy to space positive RF Detrained vapor add GHG aloft Growing Mature Dissipating Hail

7. ACP, 2010 Anvils expanding to Semi-transparent Cirrus Cloud top cooling Cloud top height [km] Radiative Forcing Wm-2 Cloud Brightening Cloud optical thickness

8. Visible, 0.6 mm

9. Thermal IR, 10.8 mm

10. 1 LongwaveEmissitivty Shortwave albedo 0 Cloud Thickness

11. Hypothesis 1 • CCN invigorate deep convective clouds by suppressing warm rain. • More supercooled water is freezing aloft and provide latent heat of freezing. • The stronger updrafts and supercooled water produce more lightning. • Clouds with higher and colder anvils produce more positive radiative forcing. • Evaporation of the larger amount of smaller ice particles enhances vapor aloft, which act as strong GHG with positive radiative forcing.

12. Alternative hypothesis: aerosol warming effect on deep clouds Rosenfeld et al., Science, 2008 Colder and wider anvils radiate less IR energy to space positive RF Detrained vapor add GHG aloft Growing Mature Dissipating Hail

13. + – After Noninductive Charge Separation Before

14. Annual average lightning density [flashes km-2] Why is Continental - Maritime classification so fundamental? TRMM annual average rainfall amount [mm / day] There is little relation between lightning and rainfall amount

15. Hypothesis 2 • Ultrafine aerosols particles (UAP) invigorate deep convective clouds with warm rain by additional drop activation aloft. • Without the UAP large S (>10%) would occur  less condensation  less latent heat release  weaker clouds. • In addition to invigoration, UAPs nucleate many small supercooled water droplets, invigoration and lightning. • The activated droplets freeze to more ice with smaller particles and longer living cirrus. • The evaporation aloft produces additional positive radiative forcing.

16. Fan, Rosenfeld et al., Science 2018

17. See effects in next slide C_ UAP CCN

18. Hypothesis 2: Adding UAP Hypothesis 1: Adding CCN C_ UAP CCN

19. Adding UAP • Higher and colder cloud tops • Larger number concentrations • Larger mass concentration • longer living and colder anvils • More positive radiative forcing

20. Avichay will show that the UAPs dominate the lightning Hoppel minimum Thornton et al., GRL 2017

21. Re of SAZ

22. Nd [cm-3] Reff of SAZ [mm]

23. CAPE – Convective Available Potential Energy [J/kg] Reff of SAZ [mm]

24. Hypothesis 3 • VOC (+) rise in the clouds to the upper troposphere, where they nucleate to SOA (+) particles. • The particles, when ingested to the supercooled parts of growing convective clouds, can invigorate them. • In addition to invigoration, UAPs nucleate many small supercooled water droplets, invigoration and lightning. • The activated droplets freeze to more ice with smaller particles and longer living cirrus. • The evaporation aloft produces additional positive radiative forcing.

28. Hypothesis 4 • VOC (+) rise in the clouds to the upper troposphere, where they nucleate to SOA (+) particles. • The particles becomes glassy at the very cold temperature of the upper tropical troposphere. • The glassy particles serve as good ice nuclei (IN) at low ice supersaturation. • This supports the formation of long living cirrus in the tropical upper troposphere. • These optically thicker cirrus clouds produce more positive radiative forcing.

29. Nucleated SOA particle conc. Natural VOC Anthropogenic VOC BL aerosol concentrations Water vapor LW emission Cirrus ice crystals SW reflectance Net energy at TOA Net warming Large net warming Small net warming Net=0 Height for glassification IN Mountain observatories height Rain initiation height Cloud base Ground Terpene α-Pinene Pristine Amazon Polluted India and China

31. Hypothesized Expectations • Nucleated SOAut (SOA in upper troposphere) tends to become glassy, hence good IN at relatively low ice S. • +SOAut +Cirrus(ut)  +Positive radiative forcing. • Hypothesized relationship between SOAut and VOCbl: SOAut = VOCbl*(COut-CObg)/(CObl-CObg), where ut=upper troposphere; bl=boundary layer; bg=background of CO. • +SOAut and/or +BL aerosols  +anvils and +lightning for the same surface precipitation  +vapor(ut) +positive radiative forcing. • In short, +Lightning for the same surface precipitation +warming.

32. Supporting papers and figures

35. The high ice clouds have large net positive radiative effect

37. July-August

38. Anomalies Two dirty hot chimneys CarbonateousAerosols ppbm Vertical Motion ppbv

40. 2010-2015 2001-2006 CarbonateousAerosols

41. From Mian Chin, GOCART originator: Aerosols accumulate because too little scavenging. Will introduce scavenging by clouds. CO All Aerosols SULFATE NITRATE ORGANIC DUST

42. Conclusions • Four mechanisms for possible positive cloud-mediated aerosol forcing are identified for deep convective and ice clouds. • This may reconcile the excessive negative cloud-mediated aerosol forcing for boundary layer marine clouds, as compared to top-down considerations of Earth’s energy budget. • Tantalizing positive indications are available and are being further perused. • There is a critical need for measurements of upper troposphere aerosols at a better sensitivity than presently available.