RO applications on Climate

1
RO applications on Climate

• Rob Kursinski
• University of Arizona

2
Introduction of Significance of the Problem

• Understanding climate change requires
  observations to
• Monitor the global energy balance (role of
  CLARREO)
• Monitor the climate state its evolution
• key variables measured with high accuracy (free
  of drift, SI traceability), complete unbiased
  sampling (global, all-weather, full diurnal),
  resolution to capture key features
• Reveal signatures of climate processes
• Critical to improving climate models (cant
  afford to wait 2 decades to discover models are
  wrong)
• High precision and resolution to measure
  variability
• Reveal previously unobserved behavior
• Needed to evaluate and improve climate models and
  reduce uncertainty about future climate

3
Observational Philosophy

• Cant afford to wait for 2 decades for climate
  signals to emerge only to discover models are
  wrong.
• Improve climate models ASAP
• Need to constrain processes to improve models now
• Need an observing system that
• determines the climate state as completely as
  possible,
• as independently of models as possible
• be ready for surprises

4
GPSRO Features
AIRS H2O distribution
missing water invisible to AIRS due to clouds

• Least biased Global Obs System
• Global coverage, cloud penetration,
• similar sampling over land ocean,
• full diurnal cycling with gt 6 sat. constellation.
• Self calibrating, SI-traceable raw observable
• Assimilate without bias correction gt improves
  utility of other obs
• Resolution
• 200 m vertical, observe vertical behavior, lapse
  rates, separate free troposphere from PBL
• Coarse along-track res of 300 km, averaging good
  for climate,
• Similarity to GCMs well matched to assessing GCM
  behavior
• High precision vert resolution constrain
  processes, also fewer samples needed to achieve
  climatological accuracy
• Pressure vs. height thermometer, balanced winds
• Water vapor to 0.1 g/kg
• Sharp vertical structures tropopause, PBL top,
  0C inversion, waves, lapse rates stability

Simple model Distributions
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GPSRO Imperfections

• Ionosphere sensitivity causes profile max
  altitude to vary, leaks into strat and UT
  profiles
• External information required for upper boundary
  conditions for Abel hydrostatic integrals
• Can we use other obs like AMSU-A for this?
• Cant directly separate wet dry contributions
  to refractivity
• Limits depth of T and P profiles to above 230K
  level,
• Subtle refractivity dependence on water vapor
  above 230K level in troposphere
• Cant measure UT stratospheric water vapor
• Non-unique refractivity profiles
  (super-refraction) within warm, moist PBL
  (working on this w/ NOAA)

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GPSRO Information content

• Bending angle near surface to 40-60 km
• Refractivity free troposphere to 40-60 km
• r, T P above 230K level to 40-60 km
• Water vapor free troposphere to 240K level
• First full global sampling in clouds and
  diurnally
• Global Vertical information quality
• Passive sensors are tentative in defining their
  vertical resolution.
• Knowledge of nadir viewing weighting functions
  requires knowing the constituent density apriori
• Horizontal scales Pressure largest, then T then
  wv.
• However very wet GPSRO profiles imply little dry
  air around ENSO upwelling center (Double ITCZ is
  another story)

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GPSRO Applications (Strat-down)

• Stratosphere cooling (Steiner et al., 2009
  possibly seeing it)
• QBO changes would indicate changes in wave
  fluxes, stability, winds
• Hygropause temperatures to help understand
  stratospheric water vapor trends
• Tropopause, dynamic tropopause, temperature
  structure at tropical convection detrainment
• Where is the transition from tropospheric warming
  to stratospheric cooling?
• Tropospheric Lapse rates and stability and
  tropospheric overturning
• Is upper troposphere warming faster than surface
  as predicted
• MSU Long term, all-weather microwave BUT MSU
  data is ambiguous
• GPSRO can see to T down to 230K level
• Pressure heights to determine what is happening
  thermally below the 230K level
• Poleward migration of the jet, Strength of jets
• Diurnal evolution of ,
• Convection (dense sampling?)
• Help correct radiosonde diurnal record issues?
• Evaluate and correct other records radiosonde
  diurnal bias, MSU

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Water vapor related information

• NOTE Method of deriving water vapor
• Simple method best for climate
• El Nino in water vapor
• MJO
• Subsidence regions
• Lightning over central Africa, differences
  between Africa and Asian monsoon profiles
• Detrainment and control of (tropical) WV
  distribution
• Water vapor and clouds and precipitation
• Water vapor boundary near 0oC
• Inside clouds RH, Temperature
• Feedbacks, OLR, clouds,
• Hurricane impact before, during after
• do extreme events enhance cooling to space

Wettest Cluster 06-07 El Nino minus 07-08 La Nina
Jan
Feb
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Water vapor and climate

• Column water (PW) is apparently increasing
  approximately in accordance with
  Clausius-Clapeyron.
• PW is dominated by PBL moisture coupled closely
  to surface
• half of water vapor feedback is in the upper
  troposphere not coupled so closely to surface.
• What is the free troposphere PW doing?
• GPSRO can separate free tropospheric water vapor
  from PBL water vapor. Need long term, stable
  open loop record.

10
Relation to Clouds Precipitation

• Determine relation between cloud properties and
  relative humidity at the grid scale. Is there a
  simple relation?
• help models predict cloud properties from grid
  scale variables
• Simplicity is highly desirable if it can capture
  essential physics.
• Temperatures in clouds
• Supersaturation above freezing level?
• Water vapor-precipitation relation
• Direct observation of hydrometeors via absorption
  polarization (Spanish experiment)

A. Kursinski et al., 2010
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ENSO
PWFT-wettest

• Coupling between warm SST free troposphere
• evident in wettest GPS profiles (not AIRS or
  ECMWF, may be issue with variational assim.)
• Gravity waves track the deep convection (T.
  Tsuda)
• El Nino warming, La Nina cooling
• MJO and its role
• Which ENSO phase is wetter in the free
  troposphere?
• Tricky In El Nino, wet regions are wetter, dry
  regions expand and are drier
• Latitudinal gradient of free tropospheric water
  vapor gt Hadley circ. strength
• Observe Walker circulation via free trop water
  vapor, pressure heights in UT
• Changes in stability in UT, in tropopause height?
• Feedbacks OLR, clouds, precip, subsidence
• El Nino predictability April-May rainfall vs.
  SST in SPCZ seems to predict upcoming ENSO phase

SST
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Miscellaneous

• PBL top coupled to albedo, balance between
  surface convection and subsidence.
• Turbulence Sergeys tropical turbulence results
  are clearly correlated with high high water vapor
  profiles
• Future changes tied to changes in overturning
  rate, less frequent, more intense convection in a
  warmer climate?
• Solar-Earth coupling Ionospheric solar cycle and
  middle atmosphere climate response? Diurnal
  cycle, 27(?) day solar cycle. Lower boundary
  conditions (wave fluxes) for upper atmosphere.

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What/how can we work together

• Support intercomparison effort to establish
  consistency and accuracy of GPSRO products
• Compare with theoretical expectations
• Joint research exploring information in the GPSRO
  profiles (need )
• Define and generate new climate products
• Processing of GPSMET to extend GPSRO record back
  to 1995
• Requires developing optimum ionospheric
  correction for GPS-MET
• Mission design for COSMIC follow-on
• Number of sats/obs
• Global, diurnal regional density of sampling
• COSMIC minimal to do gridding for ENSO
• Passive microwave or IR sounder for upper
  boundary condition?