1 Overview of the Asian monsoon anticyclone and influence on the UTLS Bill Randel Atmospheric Chemistry Division NCAR Earth System Laboratory Thanks to: Mijeong Park, Laura Pan, Louisa Emmons, Doug Kinnison, MLS team, ACE team

What is the monsoon anticyclone, and why is it interesting? dominant circulation feature of NH summer UTLS forced by deep convection over India and Bay of Bengal associated with local maxima in trace constituents (water vapor, ozone, pollutants) active region for stratosphere- troposphere coupling deep convection monsoon circulation near 16 km

monsoon circulation near 16 km carbon monoxide near 16 km MLS satellite data

Seasonal cycle of lower stratosphere H 2 O summer monsoon maximum L H Antarctic dehydration HALOE instrument on UARS satellite

summertime lower stratosphere maxima linked to Asia and North American monsoons H H L Rosenlof et al 1997 Jackson et al 1998 Dethof et al 1999 Likely contribution to water vapor entering stratosphere: Bannister et al, 2004; Gettelman et al, 2004; Park et al, 2004; Fu et al, 2006

Climatological precipitation in NH summer 6 monsoon Dynamical Background

anticyclone upper troposphere cyclone lower troposphere Cyclone at the surface, anticyclone in the upper troposphere 7

atmosphere response to steady tropical heating (Gill, 1980) longitude imposed heating latitude symmetric Rossby gyres west of heating Kelvin wave east of heating

Highwood and Hoskins (1998) Upper troposphere Lower troposphere anticyclones cyclones conv div idealized vertical structure 9 Convection, heating

Anticyclones in the UT anticyclones Convection (heating) ‘Gill-type’ Solution 10 observations Note that the anticyclone does not lie on top of the deep convection geopotential height and winds 100 hPa

Lower troposphere Upper troposphere H L cold warm Randel and Park, JGR, 2006 Dynamical Background Anticyclonic circulation extends into lower stratosphere 11 tropopause warm troposphere cold lower stratosphere

Cold, high tropopause linked to frequent cirrus frequent cirrus near tropopause Cloud fraction near 16 km

13 Potential vorticity at 360 K (~12 km) AIRS water vapor at 360 K Anticyclone is region of low PV July 10, 2003 High H 2 O confined inside anticyclone

Confinement within the anticyclone: idealized transport experiments initialize 2400 particles inside anticyclone advect with observed winds for 20 days test different pressure levels

Idealized transport simulation at 150 hPa day 0 day 10 day 20 large fraction remain inside anticyclone

Confinement within region of strongest winds

17 Earth Jupiter Persistent anticyclone (Great Red Spot)

18 Transport linked to the anticyclone: Chemical structure observed by satellites Transport pathways diagnosed from MOZART chemical transport model (Mijeong Park) Coupling with the stratosphere

MLS observations of CO Global coverage ~ 1 day ~4 km layer centered near 16 km enhanced CO mixing ratio in anticyclone MLS CO (Jun/2/2005) 100 hPa 19

MLS climatology MLS CO (Jul-Aug) 100 hPa MLS O3 (Jul-Aug) 100 hPa anticyclone high CO low ozone 20

Synoptic variability MLS CO (100 hPa) 100 hPa CO linked to monsoon convection CO OLR proxy for convection 21 Park et al, JGR, 2007

Transport pathways CO surface emission (India and South China) convective transport (main outflow near 200 hPa) confinement by anticyclone (transport to stratosphere?) 22 Transport above 200 hPa by large-scale circulation (+overshooting convection?) Diagnosed from chemical transport model Park et al, JGR, 2009

23 Asian monsoon N. American monsoon MLS H 2 O

24 Asian monsoon N. American monsoon HDO enrichment from deep convection Water vapor isotopologue HDO from ACE-FTS data MLS H 2 O Note differences between Asian and N. American monsoon

25 Anticyclonic circulation contributes to large-scale transport to/from tropics Kanopka et al, ACP, 2010 MLS observations CLaMS simulation Also: Dunkerton, 1995 Chen, 1995 isentropic summer strat-trop exchange linked to anticyclone

Hydrogen cyanide (HCN) DJFJJA tropical minimum: air with recent ocean contact ACE HCN 13.5 km max min HCN source: biomass burning HCN lifetime: ~4 years in free atmosphere, but sink from contact with ocean Observations from ACE-FTS satellite

Transport to the stratosphere via the monsoon anticyclone 27 ACE JJA climatology monsoon maximum minimum for air with recent ocean contact tropical minimum transport to stratosphere via monsoon Randel et al, Science, 2010

28 Complementary perspectives of CO vs. HCN CO lifetime ~2 months HCN lifetime ~4 years tropical minimum no tropical minimum

Key points: Asian monsoon circulation provides effective vertical transport and chemical confinement in UTLS anticyclone (region of chronic pollution) CTM with climatological sources and large-scale meteorology shows reasonable agreement with satellite observations Observations of HCN suggest monsoon transport to stratosphere - especially effective for Asian pollution (SO 2, NOx, other)

Key points: Asian monsoon circulation provides effective vertical transport and chemical confinement in UTLS anticyclone (region of chronic pollution) CTM with climatological sources and large-scale meteorology shows reasonable agreement with satellite observations Observations of HCN suggest monsoon transport to stratosphere - especially effective for Asian pollution (SO 2, NOx, other) Hofmann et al propose increases due to Chinese SO 2 increases stratospheric aerosol

Outstanding issues: Very few aircraft/balloon measurements in anticyclone (so far) How important is convective overshooting vs. large-scale transport? How does the diurnal cycle influence convective transport? What is the detailed behavior of convective and cirrus clouds? Are aerosols observed? If so, what optical properties? (absorbing?) What is the radiation balance near the tropopause? What is the detailed structure across vortex edge? (e.g. filamentation?) What are important exchange mechanisms across edge? What active chemistry is occurring? Do aerosols nucleate and grow? What controls interannual variability? How will anticyclone evolve in a changing climate?

32 12 noon 3 pm6 pm Tibet plateau convection in late afternoon CALIPSO, Cloudsat observations at 1:30 convective cloud statistics from 3-hour geostationary (CLAUS) data Blue = deep, high convective clouds (Motivated from Jonathan Wright, Rong Fu)

33 Thank you ASM-STE workshop

34 Extra slides

35 from Larry Thomason and Jean-Paul Vernier SAGE II satellite observations (cloud cleared; likely due to aerosols)

36

37 WACCM simulation of HCN - climatological sources - parameterized ocean sink ACE observations WACCM model

Tracers are simulated well by chemistry transport model 38 observationsMOZART model Park et al, JGR, 2009

One day 39

CO max over deep convection hPa Model vs. observations Park et al, JGR, 2009

MLS water vapor MLS H2O (Jul-Aug) 100 hPa MLS H2O (Jul-Aug) 216 hPa max inside the anticyclone max over deep convection 41 Park et al, JGR, hPa 216 hPa (level of convective outflow)

42 15 km CALIPSO satellite lidar cloud observations Tibet