Slide 1

RO applications on Climate Rob Kursinski University of Arizona Slide 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 Slide 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 Slide 4 GPSRO Features Least biased Global Obs System Global coverage, cloud penetration, similar sampling over land & ocean, full diurnal cycling with > 6 sat. constellation. Self calibrating, SI-traceable raw observable Assimilate without bias correction => 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 missing water invisible to AIRS due to clouds AIRS H2O distribution Simple model Distributions Slide 5 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) Slide 6 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) Slide 7 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 Slide 8 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 0 o C 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 Slide 9 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. Slide 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 Slide 11 ENSO 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 => 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 PW FT-wettest Slide 12 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. Slide 13 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?