IR High Spectral Resolution The Bologna Lectures Paul Menzel NOAA/NESDIS/ORA

CrIS Spectral Coverage B CrIS will resolve the IR spectrum from 3.9 to 15.4 um with spectral resolution greater than one part in a 1000. H2O, CO2, and O3 absorption bands will be sampled at high spectral resolution.

Interferometer measurements compared with physics calculations CO2 Lines Resolving the CO2 rotation lines at better than 0.6 wavenumbers is key to improving the vertical resolution of the temperature and moisture profile retrievals. CrIS will do that. Theory from physics and meaurements from NAST agree extraordinarily well.

Moisture Weighting Functions 100 100 Advanced Sounder (3074) GOES (18) Pressure (hPa) Pressure (hPa) 1000 1000 Moisture Weighting Functions High spectral resolution advanced sounder will have more and sharper weighting functions compared to current GOES sounder. Retrievals will have better vertical resolution. UW/CIMSS

Moisture Weighting Functions These water vapor weighting functions reflect the radiance sensitivity of the specific channels to a water vapor % change at a specific level (equivalent to dR/dlnq scaled by dlnp). Moisture Weighting Functions Pressure Weighting Function Amplitude Wavenumber (cm-1) UW/CIMSS The advanced sounder has more and sharper weighting functions

Atm Sfc Temp (K) Sfc Moisture (gm/Kg) Cold: 276 4 Warm/moist: 303 23 window Inverted TBB Atm Sfc Temp (K) Sfc Moisture (gm/Kg) Cold: 276 4 Warm/moist: 303 23 Hot/dry: 308 8 UW-Madison/CIMSS

IMG demonstrates interferometer capability to detect low level inversions: example over Ontario with inversion (absorption line BTs warmer) and Texas without (abs line BTs colder) Spikes down - Cooling with height Spikes up - Heating with height A precursor to CrIS, Japan’s Interferometric Monitor of Greenhouse Gases (IMG), flown on ADEOS, is revealing a number of important findings. For example, IMG data has been used to demonstrate the capability of detecting regions with low level thermal inversions. The forecasting implications of this capability are most significant. With a geostationary interferometer, we may be able to watch the formation and strengthening of low level inversions, surface cooling and measure atmospheric moisture in the boundary layer. If so, nowcasting the formation of fog will be possible (this has numerous implications for the transportation and agricultural industries). Similarly, we may be able to anticipate and observe the formation of low level jets at night by watching the inversion form and following the horizontal advection of moisture into a storm system or convective area. During daytime, we will be able to: 1) detail surface heating; 2) measure the evolution of convective available potential energy that will feed into a storm system; and, 3) observe the atmosphere’s inhibition to convection weaken as its low level capping inversion erodes. This should help assess a convective system’s potential for rainfall, severe weather, and downburst potential given the ability to assess moisture.

Cloud particle size is revealed in high resolution infrared spectra This figure shows calculations of cirrus cloud forcing as a function of the effective radius reff , ranging from 4.5 to 22.5 m. The spectrum opens up in the IR much the same way it did in the vcisible as particle sizes change. The spectral change in cloud forcing from 800 to 1000 cm-1 shows a pronounced S-shape for smaller ice particles (less than 10 m), which becomes more linear for larger ice particles (greater than 10 m). This characteristic shape of the spectral cloud forcing between 800 and 1000 cm-1 for small and large ice particles is useful for distinguishing the ice-particle size ranges of cirrus clouds. Between 1100 and 1200 cm-1 the cloud forcing is nearly constant as a function of wavenumber, exhibiting no strong spectral dependence. Interferometers have been utilized to detect and characterize ice clouds in field experiments. With the CrIS and other advanced interferometers such measurements can become operational. Their role in global warming will be better understood.

Two flight tracks from NAST-I WV vertical structure revealed with Geo-Interferometer The capability of a satellite borne interferometer to observe small scale atmospheric water vapor features has been investigated through the National Polar-Orbiting Environmental Satellite System (NPOESS) Aircraft Sounder Test-bed Interferometer (NAST-I) data. NAST-I has similar spectral and spatial measurement properties to the anticipated Geo-Interferometer. The slide displays the NAST-I high vertical resolution sounding capability; moist and dry layers of 1- to 2-km atmospheric depth are clearly resolved with the NAST-I system. This same vertical resolving power will be achieved with a Geo-Interferometer. Two flight tracks from NAST-I during CAMEX-3 September 14, 1998 Altitude, km --------------------------125 km------------------------- RH %

Geo-Interferometer nears Raob-like depiction of atmosphere Analysis of NOAA global raob data (tropics and mid-lat summer) VAS - past GOES - current G18 - 18 1/2cm-1 chs G50 - 50 1/2cm-1 chs GAS - ABS 2000+ 1/2cm-1 chs RAOB - T to 150mb (Q to 300mb) Information content of various geostationary measurements past, present, and possibly future are compared to that of radiosondes. A global distribution of radiosonde data gathered by NOAA is used as the data base. Information content of the satellite measurements is estimated from the trace of the vertical resolution matrix, constructed from temperature and water vapor weighting functions, instrument noise, and forecast model error covariances. The VAS and GOES sounders represent past and current capabilities. G-18 represents the information content of the current 18 GOES spectral bands if they are narrowed to half wavenumber bandwidth. G-50 represents key parts of IR spectrum measured with 50 half wavenumber bands. The Geostationary Interferometer (or the GOES Atmospheric Sounder) covers the infrared spectrum from 4-15 micron with more than 2000 narrow spectral bands. RAOB is the mean information content from radiosonde measurements. The sample is chosen from atmospheric conditions in the tropics and mid-latitudes-summer; hence the moist atmosphere label. The present GOES 18 channel sounder possesses roughly 6 pieces of independent information about tropospheric temperature profiles and 4 about moisture. Enhancing the spectral resolution to half wave number or increasing the numbers of channels to 50 does not increase the information content appreciably. Only when the complete spectrum from 4 to 15 microns is sampled at high spectral resolution does the information content increase close to radiosonde quality.

GIFTS Simulation of Hurricane Bonnie: Winds from Water Vapor Retrieval Tracking The fast coverage of a full disk in about 30 minutes is important for obtaining wind profiles from geostationary temperature and moisture sounding data (an simulation of these winds can be found in this slide). A relatively long dwell time and more limited area coverage self-validation mode of operation will enable 0.3 cm-1 spectral resolution radiances to be achieved with very high radiometric precision. The self-validation mode will be for radiance, sounding, and chemistry product validation of the routine larger area, higher frequency, spectra and geophysical products provided by the global and regional sounding modes of operation. GIFTS can achieve good simultaneity with earth orbiting satellite observations to enhance overall earth science objectives. aboard the NASA ER-2 aircraft flew near Andros Island, Bahamas on the evening of September 14, 1998. NAST data was used to infer high spatial resolution retrievals of water vapor at 800 mb. Half-hourly GIFTS data would provide observations of water vapor flux and wind profile information. In this case, an animated set of half-hourly interval images of water vapor (in terms of mixing ratio and relative humidity) are derived from a time series of NAST-I profile retrievals from spectral radiance observations over a small area near Andros Island, Bahamas. These animations imply that the water vapor flux can be observed. The flow is seen to change direction with altitude. These experimental results, which imply a strong vertical shear in wind direction, indicate that vertical profile information about the wind velocity can be achieved by observing the displacement of water vapor features at different atmospheric levels, a unique element of the GIFTS measurement concept proposed.

A sequence of images from the NAST demonstrates the elevator effect when viewing low into the atmosphere in the window regions and higher levels when in the absorption bands. The colow scale is adjusted for each image to maximize the contrast within the scene. The color bars on the right indicate the temperature range and give a sense of the atmospheric layer being viewed. This loop was prepared by David Tobin at the University of Wisconsin.

This sequence of images from the NAST demonstrates the different amount of detail detected in a portion of the aircraft flight in each spectral band. The color scale remains fixed for each image to indicate the relative changes from one spectral band to the next. The color bars on the right indicate the temperature range. Notice how the different the cloud appears in different parts of the spectrum. This loop was prepared by David Tobin at the University of Wisconsin.

ABS TRD noise (upper) and CrIS brightness temperature spectra (lower) calculated for low level temperature inversion

ABS/CrIS vs GOES retrieval for low level temperature inversion

Current retrieval strategy: - use all channels in a regression for first guess - then use a sub-set of channels for physical retrieval

1-km temperature rms and 2 km water vapor mixing ratio % rms from CrIS and GOES retrievals simulated from 590 global raobs Geo-I gets 1 K for 1 km T(p) and 15% for 2 km Q(p)

Simulated CrIS and GOES CTP rms for very high (about 200 hPa), high (about 300 hPa), medium (about 500 hPa), and low (about 850 hPa) clouds with ECA from 0.1 to 1.0 using 75 CONUS raobs.

Simulated Comparison of Current Sounder and ABS Significant improvements in surface and total column parameters are made with interferometers

Time series of low-level vertical temperature structure during 9 hours prior to Oklahoma/Kansas tornadoes on 3 May 1999 Truth> Geo-I> Note Geo-I improves depiction of boundary layer heating and surface inversion Current GOES> Geo-I traces evolution of 800 hPa inversion with 60-80% error reduction

3 May 1999 – Oklahoma/Kansas tornado outbreak GIFTS/GOES Retrieved-Temperature Errors Truth> Geo-I Errors> Standard Deviation = 0. 6o Note Geo-I reduces errors by 80% and captures 800mb inversion GOES Errors> Standard Deviation = 3. 5o Geo-I correctly captures the important vertical temperature variations

Time series of low-level vertical moisture structure during 9 hours prior to Oklahoma/Kansas tornadoes on 3 May 1999 Truth> Geo-I> Note Geo-I retains strong vertical gradients for monitoring convective instability Current GOES> Geo-I traces moisture peaks and gradients with greatly reduced errors

3 May 1999 – Oklahoma/Kansas tornado outbreak GIFTS/GOES Retrieved-Moisture (g/kg) Errors Truth> Geo-I Errors> Standard Dev. = 0.9 g/kg Note Geo-I reduces errors and captures low-level moisture peaks and vertical gradients GOES Errors> Standard Dev. = 2.4 g/kg Geo-I correctly captures important vertical moisture variations

Expectations from the Geo-Interferometer * depicts water vapor as never before by identifying small scale features of moisture vertically and horizontally in the atmosphere * tracks atmospheric motions much better by discriminating more levels of motion and assigning heights more accurately * characterizes life cycle of clouds (cradle to grave) and distinguish between ice and water cloud ( which is very useful for aircraft routing) and identify cloud particle sizes (useful for radiative effects of clouds) * measures surface temperatures (land and sea) by accounting for emissivity effects (the improved SSTs would be useful for sea level altimetry applications) * distinguishes atmospheric constituents with improved certainty; these include volcanic ash (useful for aircraft routing), ozone, and possibly methane plus others trace gases.