1 / 30

Using Submillimeter to measure cloud ice mass from earth viewing Satellites

This presentation discusses the importance of measuring cloud ice mass using submillimeter technology and its impact on Earth's radiation budget and the hydrologic cycle. It highlights the current knowledge of ice clouds and the requirements for accurate measurements. The presentation also emphasizes the global distribution of cloud ice at cloud-system-resolving scales and the need for daily global coverage. The difficulties in measuring ice clouds with traditional technology are also addressed.

hornung
Download Presentation

Using Submillimeter to measure cloud ice mass from earth viewing Satellites

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. U.Wisconsin-GSFC-JPL Using Submillimeter to measure cloud ice mass from earth viewing Satellites SIRICE Steve Ackerman/U.Wisc David Starr/GSFC K. Frank Evans/CSU 11 October 2005

  2. U.Wisconsin-GSFC-JPL Why Submillimeter to measure cloud ice mass from earth viewing Satellites? Sat-Precip and Model Precip Validation Efforts

  3. Science Team PI S. Ackerman (UW) Science team is composed of internationally recognized leaders in ice cloud studies SIRICE Management Status Review September 27, 2005- Science

  4. Outline of Presentation • Summary • Why ice clouds? • What is current knowledge of ice clouds? • What are requirements: • Spectral region • Spatial and temporal sampling • What orbit • Summary of objectives SIRICE Management Status Review September 27, 2005- Science

  5. Provide the global distribution of cloud ice at cloud-system-resolving scales • Ice water path: IWP - vertically-integrated (column) mass of ice particles per unit area, => the Earth’s Radiation Budget and linkage to the Hydrologic Cycle. • IWC weighted mean equivalent particle diameter (Dme). Crystal size => cloud radiative properties and ice crystal fall speed (vertical ice mass flux), a key model parameter. • Need measurements of IWP and Dme • Daily Global coverage (1600-km swath from LEO) at • Cloud-system resolving (10-km resolution requirement) with • Useful accuracy (±25% requirement: Ohring et al, 2004; GCSS, 2000) over • Dynamic range (5-5000 g m-2 and 40 – 800 microns) • required to quantify coupling of the Global Water and • Energy Cycles (Precipitation and Radiation Budget) SIRICE Management Status Review September 27, 2005- Science

  6. Why ice clouds? • Ice clouds are: • Crucial to Earth’s Radiation Budget (Energy Cycle) • (~large area coverage, highly variable properties) SIRICE Management Status Review September 27, 2005- Science

  7. Why ice clouds ? • Ice clouds are: • Crucial to Earth’s Radiation Budget (Energy Cycle) • (~large area coverage, highly variable properties) • Difficult to measure with traditional technology • (ICSSP/GOES, MODIS, AIRS, AMSU-B, CloudSat/CALIPSO) • - Estimates of global mean IWP range from 20 to 150 g m2 !!! SIRICE Management Status Review September 27, 2005- Science

  8. Why ice clouds? • Ice clouds are: • Crucial to Earth’s Radiation Budget (Energy Cycle) • (~ large area coverage, highly variable properties) • Difficult to measure with traditional technology • (ICSSP/GOES, MODIS, AIRS, AMSU-B, CloudSat/CALIPSO) • - Estimates of global mean IWP range from 20 to 150 g m2 !!! • Generated directly by Precipitating Cloud Systems (Water/Hydrologic and Energy Cycles), or sublimated ice and vapor detrained earlier • What doesn’t fall out as Precipitation, gets detrained ! SIRICE Management Status Review September 27, 2005- Science

  9. Why are ice cloud measurements needed? Ice is transported into the upper troposphere by: Convection (thunderstorms) Large scale lifting (e.g. fronts) => cirrus => cirrus This ice will: • Lead to heating associated with the ice – energy and hydrological cycle • Sublimate and moisten upper/mid troposphere - impacts energy budget • Fall out as precipitation – impacts hydrological cycle SIRICE Management Status Review September 27, 2005- Science

  10. Why ice clouds ? • Ice clouds are: • Crucial to Earth’s Radiation Budget (Energy Cycle) • (~ large area coverage, highly variable properties) • Difficult to measure with traditional technology • (ICSSP/GOES, MODIS, AIRS, AMSU-B, CloudSat/CALIPSO) • - Estimates of global mean IWP range from 20 to 150 g m2 !!! • Generated directly by Precipitating Cloud Systems (Water/Hydrologic and Energy Cycles), or sublimated ice and vapor detrained earlier • What doesn’t fall out as Precipitation, gets detrained ! SIRICE Management Status Review September 27, 2005- Science

  11. Why ice clouds? • Ice clouds are: • Crucial to Earth’s Radiation Budget (Energy Cycle) • (~ large area coverage, highly variable properties) • Difficult to measure with traditional technology • (ICSSP/GOES, MODIS, AIRS, AMSU-B, CloudSat/CALIPSO) • - Estimates of global mean IWP range from 20 to 150 g m2 !!! • Generated directly by Precipitating Cloud Systems (Water/Hydrologic and Energy Cycles), or sublimated ice and vapor detrained earlier • What doesn’t fall out as Precipitation, gets detrained ! • • Estimates of global mean IWP range from 20-150 g m2 !!! • => Ice clouds are a major unconstrained/free tuning knob (largest remaining uncertainty) available to GCM’s to achieve agreement with observations of global energy budget (ERBE, CERES) and precipitation (AMSR, TRMM, GPM). SIRICE Management Status Review September 27, 2005- Science

  12. What is our current knowledge? The large discrepancy in mean IWP between climate models is one demonstration of our poor knowledge of ice mass in the atmosphere. Ohring et al (2004) note that for climate monitoring purposes, IWP must be measured to an accuracy of 25% and that no satellite missions meet this requirement. (NIST-NOAA-NASA workshop on Satellite Instrument Calibration for Measuring Global Climate Change) The climatology of zonal, annual mean IWP from state-of-the-art global models. SIRICE Management Status Review September 27, 2005- Science

  13. What is our current knowledge? If you change the IWP, you change the amount of precipitation: => more ice, less rain 40 40 30 30 Reflected Solar 20 20 Change in TOA Radiative Fluxes (W m-2) 10 10 If you change the IWP, you change the radiative energy budget: => more ice, brighter planet, Change in Precipitation (%) -10 -10 Precipitation -20 -20 Outgoing Infrared Warmer surface? -30 -30 25 50 75 100 Change in IWP (g m-2) Global cloud ice measurementsare essential for understanding the coupling of the global hydrologic and energy cycles. The sensitivity of GCM tropical radiative and precipitation fields to IWP. SIRICE Management Status Review September 27, 2005- Science

  14. What ranges do we need to measure? Approximately 80% of the clouds have IWP less than 100 g m-2; these clouds contain less than 10% of the total ice mass. Small IWP end is important for Earth Radiation Budget. Large IWP end is important for the Hydrologic cycle. Need to accurately measure the large range in ice mass. Fraction of pixels < IWP Fraction of mass < IWP The fraction of pixels with IWP less than a given value (blue) and the fraction of the total mass in pixels with IWP less than a given value (red) SIRICE Management Status Review September 27, 2005- Science

  15. Science Requirement: Range Science Objective • Provide global measurements of ice water path (IWP) and median mass particle diameter (Dme). • These measurements will have the temporal and spatial sampling required for accurate regional averages needed to improve the modeling of ice clouds in climate models. Scientific Measurement Requirement IWP in the range of 5 to 5000 g m-2Dme in the range of 40 to 800 microns SIRICE Management Status Review September 27, 2005- Science

  16. What wavelengths do we need? • Below 1500 GHz radiation interacts with ice particles primarily by scattering. • The change in the upwelling brightness temperature (Tb) compared to clear sky is a function of IWP and particle size. • Submillimeter-wave radiation is emitted upwards by water vapor in the opaque lower troposphere. The physics of the measurements is well known. SIRICE Management Status Review September 27, 2005- Science

  17. What wavelengths do we need? • Cirrus significantly reduces the brightness temperature in the submillimeter part of the spectrum. • The brightness temperature depression generally increases with frequency. • Brightness temperature saturates slowly for large IWP. • Polarization is a function of crystal shape Simulations demonstrate sensitivity of submm observations to ice cloud properties. SIRICE Management Status Review September 27, 2005- Science

  18. What wavelengths do we need? • A demonstration of the retrieval and its errors: IWP and median mass diameter (with error bars) are retrieved with a Bayesian algorithm (Evans et al., JGR, Feb 2002) (see top figure). Validation is accomplished through comparison with the vertically integrated radar reflectivity. (see bottom figure). The retrieval applied to CoSSIR measurements agrees very well with radar reflectivity Channel selection based on detailed trade studies. SIRICE Management Status Review September 27, 2005- Science

  19. What wavelengths do we need? • Retrieval errors in IWP as a function of IWP for combination of Submm, IR and Stereo. • This is a result of detailed sensitivity studies to determine the optimum set of wavelengths and noise requirements for meeting retrieval requirements. • One frequency with two linear polarization to determine particle shape. • Knowledge of cloud altitude improves retrievals for less than 25 g m-2, more than 50% of the observed ice cloud frequency. Channel selection based on detailed trade studies. SIRICE Management Status Review September 27, 2005- Science

  20. What is new and unique? SIRICE Microwave CIMS Solar, Infrared VIIRS Submm is more then an evolution of existing observations – provides new spectral measurements of clouds at Submm wavelengths that compliment planned solar, infrared and microwave observations When integrated with other coincident satellite measurements, Submm will uniquely provide the first complete description of the hydrometeor content and structure of cloud systems. SIRICE Management Status Review September 27, 2005- Science

  21. Why Submm? • Recent submillimeter technology (MLS, CoSSIR) • Well-understood strong physics and mature algorithms • Enables multiple science pathways to model improvements • Global/zonal constraints (accuracy) • Regional/seasonal constraints (sampling) • 2-year global integrated system analysis via data assimilation • Cloud system composites, seasonal/regional, to constrain the detailed cloud system models that underpin GCM’s (GCSS) • Submm observations hugely enhanced if formation fly with microwave SIRICE Management Status Review September 27, 2005- Science

  22. Unique Measurements of Hydrological Cycle Infrared – thin cloudsSolar – top of clouds Submm – Ice Water Path microwave – Liquid Water Path microwave - precipitation Need measurements a component of the hydrological cycle that we know little about – the amount of ice in the atmosphere. SIRICE Management Status Review September 27, 2005- Science

  23. Science Requirement: Complete Range Scientific Measurement Requirement IWP in the range of 5 to 5000 g m-2Dme in the range of 40 to 800 micron Rigorous and comprehensive trade studies show…. Instrument Functional Requirement Two instruments: Infrared and submillimeter wavelengths SIRICE Management Status Review September 27, 2005- Science

  24. Science Pathway Cloud ice generation in mm/day by ECMWF, July Large scale lifting Convection Latitude It is not enough to observe the zonal mean variables. Need observations as a function of process. Convective and synoptic systems transport ice into the upper troposphere. Need to resolve these processes to improve models. SIRICE Management Status Review September 27, 2005- Science

  25. Science Pathway Scientific Measurement Requirement Daily near-global coverageSample storm system spatial resolution – convective and synoptic Robust regional/seasonal statistics and data assimilation for global description of complete cloud component of global hydrological cycle.=> wide swath for global coverage Process resolving analysis and cloud system modeling.=> Resolution SIRICE Management Status Review September 27, 2005- Science

  26. Spatial Resolution Requirement 10 km fov Scientific Measurement Requirement Spatial resolution: field-of-view Optimum field of view is a trade between instrument noise, uniform scene, and the scale of the weather phenomena. These trade studies led us to a submm fov of ~10-15 km. Cirrus along front extending across midwest, along with a 10 km circle for scale. SIRICE Management Status Review September 27, 2005- Science

  27. Spatial Coverage Requirement Science Objective • Characterize IWP and Dme distributions at a cloud-process-resolving scale as a function of cloud systems and meteorological process, thus quantifying the contribution of upper tropospheric ice production by deep convection and synoptic lifting. • Application of measurements to cloud system modeling research will improve our understanding of ice cloud processes needed for improved climate predictions. Requires Robust regional/seasonal climatology => Daily near-global coverage 2-year integrated Earth System analysis via Data Assimilation=> Daily near-global coverage Resolve cloud system processes/structure for many cloud systems, convective and synoptic => ~ 10 km resolution, broad swath coverage SIRICE Management Status Review September 27, 2005- Science

  28. Spatial Coverage Requirement Scientific Measurement Requirement Daily near-global coverageSample storm system spatial resolution – convective and synoptic Instrument Functional Requirement Approximately 10 km resolution - trade of instrument noise and scale of weather systems Conical scanning with a wide swath - trade of instrument noise, rotation, and spatial coverage Polar orbit (mission requirement) - At ~ 833 km orbit => Conical Scanning Imager, ~1600 km swath SIRICE Management Status Review September 27, 2005- Science

  29. Orbit Selection Scientific Measurement Requirement Daily near-global coverageApproximately 10 km resolution Mission Functional Requirement Sun-synchronous, morning/evening orbit => captures convection over tropical waters (morning, ice lags precip max) and continents (evening), fly with planned satellite that have visible, infrared and microwave measurements to allow complete cloud system characterization. TRMM observations help with selecting equatorial crossing SIRICE Management Status Review September 27, 2005- Science

  30. Summary: Science Objectives • Provide global measurements of ice water path (IWP) and weighted median mass particle diameter (Dme). • These measurements will have the temporal and spatial sampling required for accurate regional averages needed to improve the modeling of ice clouds in climate models. • Characterize IWP and Dme distributions at a cloud-process-resolving scale as a function of cloud systems and meteorological process, thus quantifying the contribution of upper tropospheric ice production by deep convection and synoptic lifting. • Application of measurements to cloud system modeling research will improve our understanding of ice cloud processes needed for improved climate predictions. SIRICE Management Status Review September 27, 2005- Science

More Related