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HIRDLS Status EOS-Chem Science Team Meeting Boulder, 29-31 March 2000 John Gille and John Barnett

HIRDLS Status EOS-Chem Science Team Meeting Boulder, 29-31 March 2000 John Gille and John Barnett. Overarching scientific themes for HIRDLS. Stratospheric ozone Monitoring ozone recovery Natural variability of the stratosphere, dynamical and chemical

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HIRDLS Status EOS-Chem Science Team Meeting Boulder, 29-31 March 2000 John Gille and John Barnett

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  1. HIRDLS StatusEOS-Chem Science Team MeetingBoulder, 29-31 March 2000John Gille and John Barnett

  2. Overarching scientific themes for HIRDLS • Stratospheric ozone • Monitoring ozone recovery • Natural variability of the stratosphere, dynamical and chemical • Defining interannual variability on a wide range of scales in time • and space • Long term climate change, including global warming • Separating trends from natural variability • Air quality • Gases and aerosols in the upper troposphere

  3. Indicator of climate changes • The stratosphere can be a sensitive indicator of changes at lower levels: • 1) Water vapour amounts are increasing at about 1% per year. • - too much to be explained by increasing CH4 in the troposphere. • - does it indicate a change in the tropopause 'cold trap' temperature, • meridional circulation, • something else? • How does it affect the chemistry and radiation? • 2) The stratosphere is cooling • - approx 0.5 C/decade in lower stratosphere (consistent with models) • - approx 1.5 C/decade in upper stratosphere (larger than models) • Can we verify these changes? • What is happening in the mesosphere?

  4. Upward trend of water vapour concentration Stratospheric water vapour amounts are increasing at 1% per year. This more than is explained by CH4 increase. HALOE satellite data give same result. Trends in stratospheric water vapour observed above Colorado by balloon-borne frost-point hygrometers from 1981-1997. Blue area is 95% confidence limit in trend. [Oltmans, Vömel, Hofmann, NOAA]

  5. Can we see the underlying changes through the ‘noise’? • Very big wintertime variations occur from year-to-year: • by some measures this winter nearly 10 times colder than last • winter for PSC formation. • These changes are assumed to be dynamic in origin. • Can we understand them? • They introduce noise, so make it very difficult to detect underlying wintertime • climatic changes unless they are very big or we wait many decades • Can we find ways to allow for themwhen measuring long term changes?

  6. 1999-2000 North Polar temperatures compared with daily means and extremes for 1979-2000 [From http://www.cpc.ncep.noaa.gov]

  7. Conditions for PSC formation at North Pole Accumulated ‘degree days’ below Type-1 PSC formation temperature (195 K) at 40 hPa (approx 20 km) at the North Pole 1992-2000 (from UK Met. Office).

  8. Transport across and along the tropopause • Our knowledge of transport of constituents, heat and momentum • across the tropopause is relatively crudely known. This is a driver • of stratospheric chemistry, dynamics and radiation and to a lesser • extent of the troposphere. • Can we make quantitative measurements of transports? • Do we understand all of the processes?

  9. Transport features observed by HIRDLS [Figure from J.Holton/UGAMP]

  10. Isentropic transport near the tropopause Particles released on 400 K isentrope between 20o S and 20oN on 1/1/99 [From Bill Randel]

  11. Stratosphere-troposphere exchange on small scales Passive tracers on the 320 K isentrope. Coloured air is stratospheric, blank is tropospheric [From Appenzeller et al. [1995]]

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