James Purdom & Kenneth Eis CIRA Colorado State University, Fort Collins, CO 80523

Geostationary Hyperspectral Imaging from 0.4 to 1 microns:A Potent Tool for Convective

Analysis and Nowcasting

James Purdom&

Kenneth Eis CIRA

Colorado State University, Fort Collins, CO 80523

Nowcasting convection requires frequent imaging and sounding that can only be provided by

geostationary satellites.GOES-R: NOAA’s next generation geostationary satellite – “unique” in spectra, space and time (2012 timeframe)

The spatial and temporal variability of the phenomena being nowcast drive the observational needs as a function of its spectral, spatial and temporal domains, as well as signal to noise.

GOES-R’s Primary Earth Viewing Sensors: All play a role in nowcasting

• Advanced Baseline Imager

• Hyperspectral Environmental Suite– Hyperspectral IR

Sounder• Global mode• Mesoscale mode

– Hyperspectral visible to near IR imager

• Lightning detection sensor

• The spatial and temporal variability of the phenomena being nowcast drive the observational needs as a function of its spectral, spatial and temporal domains, as well as signal to noise.

Anticipated Highlights• Advanced Baseline

Imager• Hyperspectral

Environmental Suite– Hyperspectral IR




• 16 or more channels• 5 minute full disk

capability with rapid scan capability

• ½, 1 and 2 km resolution depending on channel







• Hyperspectral regions from about 3.9 to 15 microns

• Hourly global at 10 km spatial resolution with capability of adaptive observing with more frequent limited areas (mesoscale) at 4 km resolution



Environmental Suite– Hyperspectral IR Sounder

• Global mode• Mesoscale mode

– Hyperspectral visible to near IR imager (HES-VNIR)


• Possible attributes– Hyperspectral from

about 0.4 to 1.0 microns with 10 or 20 nanometer spectral resolution

– 150 to 300 meters spatial resolution

– 6 second views of around 4000 to 5000 sq km







• 10 km resolution over most of earth disk (basically within 62 degree zenith angle)

• Near instantaneous refresh

In satellite remote sensing, four basic parameters need to be addressed: all deal with resolution

– temporal (how often) – spatial (what size)– spectral (what wavelengths

and their width)– radiometric (signal-to-noise)

Compare cloud field evolution at different time intervals –GOES-R’s ABI with 5 minute full disk imagery (along with rapid scan capability and HES-VNIR) will provide unparalleled monitoring capability for nowcasting convection.




The cold thunderstorm overshooting top region more accurately depicted using higher resolution data: this is important because the overshooting and coldness reflects storm updraft intensity - GOES-R’s ABI will provide unparalleled capability for assessing thunderstorm development, evolution and intensity. * GOES-R’s hyperspectral sounder, in the

mesoscale mode, will have a spatial resolution similar to the 4 km GOES-8 image (bottom left)

1 Km (today’s GOES) to 250 m (GOES-R HES-VNIR)

GOES-8: ~1 km Hurricane Erin09/09/01 ~1530 Z

MODIS: ~250 m

Note the detail in the eye wall (you can see up its side), improving the resolution of visible imagery (ABI and HES-VNIR) provides enhanced ability to analyze its cloud field




Each spatial element has a continuous spectrum that may be used to analyze the surface and atmosphere




•Next slide will show - Spectral animation from AIRS covering much of the mid-wavelength infrared portion of the spectrum

•With the hyperspectral sounder operating in the mesoscale mode this type data will be available at 4 km resolution (AIRS is 10x20 km res.)

High SpectralResolution

(AIRS)resolves

H2Ospectral

Features (right)

GOES-I/M era sounder H20

Channels (above)

Hyperspectral IR sounders: the potential for very accurate surface temperatures and detection of temperature inversions

Detection of inversions is critical for severe weather forecasting. Combined with improved low-level moisture

depiction, key ingredients for night-time severe storm development can be monitored.

Spikes down - cooling with height

Spikes up -warming with height

Texas

Ontario

Brig

htne

ss T

empe

ratu

re (K

)

(low-level inversion)

(No inversion)

Wavenumber (cm-1)


• They all deal with resolution: – temporal (how often) – spatial (what size)– spectral (what wavelengths

and their width)– radiometric (signal-to-

noise)

AVIRIS Loop - Linden CA 20-Aug-1992224 Spectral Bands: 0.4 - 2.5 m

Pixel: 20m x 20m Scene: 10km x 10km

Smoke - large part.

CloudHot Area

Smoke -small part.

Fire

Shadow

Grass

Lake

Soil

Example of AVIRIS Spectral Information from a Scene Depicting Cloud, Smoke and Active Burn Areas

AVIRIS Image - Linden CA 20-Aug-1992 Spectral Signatures of Selected Pixels

The unique characteristics of the spectral signatures provide a way to identify and characterize each feature and to derive other useful information about the scene. HES-VNIR has the potential for numerous atmospheric, ocean, land applications – for some we need to filter atmospheric effects and use that information

Water Vapor: a filtered atmospheric effectnote water vapor change every 15 minutes

HES VNIR at high resolutions will be able to monitor pre-cumulus cloud moisture and moisture convergence – this will be enhanced by HES-IR

Water vapor exhibits remarkable variability in space and time (as above!); it serves as the key energy source for deep convective development. For example, releasing latent heat: a gram of water vapor condensed into a kilogram of air (about 1 cu meter) will raise that air’s temperature about 2.5 ºK. Water vapor is important on scales ranging from climate to convection.

EO-1’s hyperion: a glimpse to the future

Hyperion (IHOP Day 173, 1650 UTC)Hyperion is hyperspectral sensor on NASA’s EO-1

Derived Water Vapor ImageMean CWV: 35.1 mm

37.4 mm (no clds)

Raob @ 18 UTC: 34.5 mm

WV Image Histogram

CWV (cm)

•This case is being investigated with Mike Griffin of MIT/LL

Spatial Simulations (7.5 km x 30 km)

256 x 1000 51 x 210 16 x 65 4 x 16 1 x 4

HSI 30m HES-VNIR 150m ABI VIS 480m ABI IR 2km ABS 7.5km

Notice how readily cloud free fields of view can be detected at higher resolutions, allowing for detailed column water vapor retrievals – in synergy with HES-IR, this will provide powerful information for nowcasting convection

Great Plains severe thunderstorm viewed by GOES-West and GOES-East

From geostationary altitude we see the side of the base, side and top of clouds. Different viewing perspectives allow for stereo height determination of various features.

The development and evolution of deep convection

Unique in space and time

•To the right is the first ever one minute interval imagery taken by a geostationary satellite. It covers 6 minutes, and illustrates the dynamic nature of a strong (large hail) thunderstorm. The area covered is approximately 160 x 160 km.

•Notice the cloud field variability, differences in cloud motion, cloud top and anvil growth, cloud growth along a front at the top of the image

Viewing Perspective, t and , determine what we see

with HES-VNIR

• Differences in scattering as a function of sun-scatterer-detector geometry allow for a variety of atmospheric, land, costal zone and ocean applications (think of MISR)

• Stereo cloud height determinations: accuracy is in large part a function of spatial resolution (shadows can also provide exceptionally accurate cloud height depending on time of day and viewing geometries)

• Exceptional CMV’s (u, u', v, v', w') in complex situations: potential for nearly 50 times higher resolution than today (150m vs 1000m) and over 10 times higher than GOES-R’s ABI (150m vs 500m)

• Pre-cumulus moisture field and its changes in time

• Over land atmospheric instability can change dramatically due to surface heating, an increase in low level moisture due to advection and evaporation as well as precipitation effects

• For nowcasting, one question is how representative is a sounding the further one is displaced from it as a function of space and time

• Thermodynamic soundings at different locations in these images will provide different information. This is especially true in the boundary layer where the fuel for deep convection is found. GOES-R will provide greatly enhanced capabilities to monitor moisture with HES-IR and HES-VNIR, and surface temperature with HES-IR and ABI.

Photo of thunderstorm from manned s/c

Photo of convection from airplane

•GOES-8 loop from 1033 to 1615: this loop illustrates the changes that have occurred in the cloud field (and boundary layer) since the launch of a “representative” rawinsonde.

MODIS at 1 km resolution compared to same data at 250 meters (similar to HES-VNIR)

Notice how well the cloud field can be analyzed at 250 meters. Everywhere there isn’t a cloud you can compute moisture from HES-VIS/NIR, and where there are the bigger holes you can do the total job with HES-IR (some are representative of a modified boundary layer due to storm outflow air)

Severe Weather

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GOES Visible Loop at 1 to 30 minute Intervals July 24, 2000 severe weather July 24, 2000 severe weather

outbreak across South Dakota outbreak across South Dakota and Nebraska produces hail, and Nebraska produces hail, tornadoes, flash flooding and tornadoes, flash flooding and damaging windsdamaging winds One minute interval visible One minute interval visible

imagery shows storm imagery shows storm evolution over 2 hr periodevolution over 2 hr period

Important for severe weather: Vertical wind shear, evolving instability field, updraft strength, anvil development and blocking, rotating cloud top

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Vertical shear ABI (cloud motion) HES-IR (moisture motion) HES-VNIR (cloud and

moisture motion) Evolving instability field

ABI (surface heating) HES-IR (instability and

surface heating) HES-VNIR (detailed

moisture field) Updraft strength

ABI (IR top temperature) ABI and HES-VNIR

(overshooting top height) Above with HES-IR

(updraft efficiency)

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Updraft strength ABI (IR top temperature) ABI and HES-VNIR

(overshooting top height) Above with HES-IR

(updraft efficiency) Anvil development and

blocking ABI (growth and detailed

upper level atmospheric motion and water vapor behavior)

HES-IR and VNIR (as ABI but with better spectral definition)

Rotating overshooting top ABI and HES-VNIR

Oklahoma City tornado of May 3, 1999 left damage easily detected by Landsat 5 several days later (30 meter resolution), with residual damage even evident almost one year later. There are other instances where Landsat imagery has been used to locate areas of storm damage from hail, wind and tornadoes. Frequent hyper-spectral views possible from HES-VNIR point to a new and exciting potential

High resolution Hyperspectral: We infer today, we will see and measure with GOES-R

– Very accurate cloud motion vectors with accurate cloud bases and cloud tops

– High resolution water vapor measurements in the presence of cumulus cloudiness

– A few implications (with ABI and HES-IR & VNIR)

• Monitor the growth and destabilization of the boundary layer over land

• Cloud growth rate and cloud top behavior

• Smoke, haze, dust, aerosols, visibility in cloud free areas

• Damage paths for large storms• Areas of flooding (wet ground)

Shear, cold air production, evolving instability field, updraft strength, anvil development, blocking, cloud motion, rotating cloud top, rain area, hail swath and tornado damage path –

High resolution Hyperspectral: And we haven’t even talked about hurricanes and other phenomena – like

moisture, aerosols and plume tracking for “local disasters”

Documents

James Purdom & Kenneth Eis CIRA Colorado State University, Fort Collins, CO 80523