In the past thirty five years NOAA, with help from NASA, has established a remote sensing capability on polar and geostationary platforms that has proven useful in monitoring and predicting severe weather such as tornadic outbreaks, tropical cyclones, and flash floods in the short term, and climate trends indicated by sea surface temperatures, biomass burning, and cloud cover in the longer term. This has become possible first with the visible and infrared window imagery of the 1970s and has been augmented with the temperature and moisture sounding capability of the 1980s. The imagery from the NOAA satellites, especially the time continuous observations from geostationary instruments, dramatically enhanced our ability to understand atmospheric cloud motions and to predict severe thunderstorms. These data were almost immediately incorporated into operational procedures. Use of sounder data in the operational weather systems is more recently coming of age. The polar orbiting sounders are filling important data voids at synoptic scales. Applications include temperature and moisture analyses for weather prediction, analysis of atmospheric stability, estimation of tropical cyclone intensity and position, and global analyses of clouds. The Advanced TIROS Operational Vertical Sounder (ATOVS) includes both infrared and microwave observations with the latter helping considerably to alleviate the influence of clouds for all weather soundings. The Geostationary Operational Environmental Satellite (GOES) Imager and Sounder have been used to develop procedures for retrieving atmospheric temperature, moisture, and wind at hourly intervals in the northern hemisphere. Temporal and spatial changes in atmospheric moisture and stability are improving severe storm warnings. Atmospheric flow fields are helping to improve hurricane trajectory forecasting. Applications of these NOAA data also extend to the climate programs; archives from the last fifteen years offer important information about the effects of aerosols and greenhouse gases and possible trends in global temperature. This talk will indicate the present capabilities and foreshadow some of the developments anticipated in the next twenty years. Summary of Spectral Signatures Labs in Bertinoro 23 Aug – 2 Sep 2004 Paul Menzel NOAA/NESDIS/ORA

Solar (visible) and Earth emitted (infrared) energy Incoming solar radiation (mostly visible) drives the earth-atmosphere (which emits infrared). Over the annual cycle, the incoming solar energy that makes it to the earth surface (about 50 %) is balanced by the outgoing thermal infrared energy emitted through the atmosphere. The atmosphere transmits, absorbs (by H2O, O2, O3, dust) reflects (by clouds), and scatters (by aerosols) incoming visible; the earth surface absorbs and reflects the transmitted visible. Atmospheric H2O, CO2, and O3 selectively transmit or absorb the outgoing infrared radiation. The outgoing microwave is primarily affected by H2O and O2.

Solar Spectrum The top of the atmosphere incoming solar radiation is characterized by a Planck blackbody of temperature about 6000 K. Of the electromagnetic energy emitted from the sun, approximately 50% lies in wavelengths longer than the visible region, about 40% in the visible region (0.4-0.7 m), and about 10% in wavelengths shorter than the visible region. The radiation sensed at the surface of the earth has been attenuated by atmospheric O3, O2, CO2, and H2O (most of the water vapor sensitive bands occur at wavelengths longer than 0.8 um). The visible remote sensing from geo orbit with GOES has been traditionally covering .5 to .9 um; from leo orbit with AVHRR two spectral bands .58 to .68 um (lower reflection from vegetation) and .72 to 1.00 um (higher vegetation reflection) have been maintained. With the launch of the MODIS, the monitoring in the visible has been expanded to 19 bands.

VIIRS, MODIS, FY-1C, AVHRR CO2 O2 H2O O2 H2O H2O H2O O2 H2O H2O CO2

MODIS IR Spectral Bands This slide shows an observed infrared spectrum of the earth thermal emission of radiance to space. The earth surface Planck blackbody - like radiation at 295 K is severely attenuated in some spectral regions. Around the absorbing bands of the constituent gases of the atmosphere (CO2 at 4.3 and 15.0 um, H20 at 6.3 um, and O3 at 9.7 um), vertical profiles of atmospheric parameters can be derived. Sampling in the spectral region at the center of the absorption band yields radiation from the upper levels of the atmosphere (e.g. radiation from below has already been absorbed by the atmospheric gas); sampling in spectral regions away from the center of the absorption band yields radiation from successively lower levels of the atmosphere. Away from the absorption band are the windows to the bottom of the atmosphere. Surface temperatures of 296 K are evident in the 11 micron window region of the spectrum and tropopause emissions of 220 K in the 15 micron absorption band. As the spectral region moves toward the center of the CO2 absorption band, the radiation temperature decreases due to the decrease of temperature with altitude in the lower atmosphere. IR remote sensing (e.g. HIRS and GOES Sounder) currently covers the portion of the spectrum that extends from around 3 microns out to about 15 microns. Each measurement from a given field of view (spatial element) has a continuous spectrum that may be used to analyze the earth surface and atmosphere. Until recently, we have used “chunks” of the spectrum (channels over selected wavelengths) for our analysis. In the near future, we will be able to take advantage of the very high spectral resolution information contained within the 3-15 micron portion of the spectrum. From the polar orbiting satellites, horizontal resolutions on the order of 10 kilometers will be available, and depending on the year, we may see views over the same area as frequently as once every 4 hours (assuming 3 polar satellites with interferometers). With future geostationary interferometers, it may be possible to view at 4 kilometer resolution with a repeat frequency of once every 5 minutes to once an hour, depending on the area scanned and spectral resolution and signal to noise required for given applications.

GOES Sounder Spectral Bands: 14.7 to 3.7 um and vis The GOES Sounder spectral bands are indicated along with there sensitivity to a particular atmospheric layer. Blue are the temperature sensitive bands, red are moisture bands, and green are surface bands. As indicated earlier, sampling in the spectral region at the center of the absorption band yields radiation from the upper levels of the atmosphere (e.g. radiation from below has already been absorbed by the atmospheric gas); sampling in spectral regions away from the center of the absorption band yields radiation from successively lower levels of the atmosphere. Away from the absorption band are the windows to the bottom of the atmosphere. Surface temperatures of 296 K are evident in the 11 micron window region of the spectrum and tropopause emissions of 210 K in the 15 micron absorption band. As the spectral region moves toward the center of the CO2 absorption band, the radiation temperature decreases due to the decrease of temperature with altitude in the lower atmosphere.

II II I |I I ATMS Spectral Regions

MODIS

High ice cld Midlevel cld Midlevel cld Low water cld Ice reflectance High ice cld Midlevel cld Midlevel cld Low water cld

On board Terra, MODIS (Moderate Resolution Imaging Spectroradiometer) is beginning to deliver exciting data about the oceans, land , and atmosphere. The following slides explain the spectral channel selection and present a few applications examples in each area. For ocean applications, the MODIS team has selected several spectral bands that are on line and off line absorption features associated with chlorophyll and accessary pigments. The multispectral data will be used to reveal their respective concentrations in the ocean waters.

Or land applications, MODIS has several spectral bands that are above and below step function increases or decreases in the reflectivity of vegetation (increases above 0.72 um) or snow/ice (decreases above 1.4 um). The multispectral data will be used to reveal the extent of vegetation and snow/ice in the various regions of the globe.

Kaolinite montmorillonite Kaolinite montmorillonite

Optical properties of cloud particles: imaginary part of refraction index SW & LW channel differences are used for cloud identification {4 m - 11m}, {4.13 m - 12.6m}, and {4.53 m - 13.4m}

BT11-BT12 < 0 for volcanic ash BT11-BT12 > 0 for ice BT11-BT12 < 0 for volcanic ash Frank Honey 1980s

SO2 calculations from F. Prata

Fog Detection over Snow Surfaces "Non-detection" of fog over snow surfaces with VIS channels: thick clouds and snow have the same reflectance

Emissivity as a function of wavelength and surface type Emissivity more variable near 3.9 m Sandy areas appear 5-10 K cooler at IR3.9 than at IR10.8 (at night, dry atmosphere) Different appearance of land surfaces during daytime, depending on surface type IR3.9 IR10.8 Dry sand: 0.8 0.95 Emissivity as a function of wavelength and surface type

Dust and Cirrus Signals Imaginary Index of Refraction of Ice and Dust Both ice and silicate absorption small in 1200 cm-1 window In the 800-1000 cm-1 atmospheric window: Silicate index increases Ice index decreases with wavenumber Volz, F.E. : Infrared optical constant of ammonium sulphate, Sahara Dust, volcanic pumice and flash, Appl Opt 12 564-658 (1973) wavenumber

Dust IR spectra – green clr sky vs dust particles of different size

Dust IR spectra – green clr sky vs dust layers at different heights

Fog and Low Stratus

Comparison of snow reflectance in VIS and NIR 1.6 channels

Energy spectrum Source: EUMETSAT Ch08 Ch08 is in the centre of the O3 absorption band around 9 

Signals from lower parts of troposphere; But: Secondary maximum from higher than 100 hPa Weighting functions Source: EUMETSAT Figure 3c

AIRS radiance changes (in deg K) to atm & sfc changes 43

LSE is Land Surface Emissivity Inferring surface properties with S-HIS high spectral resolution data - Note the large change, especially for bare soil, in surface emissivity between 960 and 1060 cm-1. The HES minimum mission would not cover both regions. 44 Pure Vegetation 1.0 From Bob K. of SSEC. Aircraft validation measurements are consistent with a linear combination of vegetation and bare soil. S-HIS is Scanning HIS. LSE is Land Surface Emissivity Aircraft S-HIS LSE S-HIS OBS Bare Soil 12 m 9 m 0.85 Wavenumber (cm-1)