Night Water Vapor Borel Spie 8 12 08 White

Method for retrieving column water vapor at night using mid-wave infrared bands Dr. Christoph. C. Borel , and Dr. Michael Abel* *Ball Aerospace & Technologies Corp., Fairborn, OH 45324 [email_address] ; www.cborel.net SPIE Optics and Photonics Symposium, 10-14 August 2008, San Diego, California, USA OP407 Imaging Spectrometry XIII (Shen/Lewis)

Content ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The problem, solution and benefits of a mid-wave columnar water vapor retrieval for night time data ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Sensor data with CW retrieval capability Sensor data with no CW retrieval capability Accurate surface temperature

Introduction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],§ From: S. Wetzel-Seeman et al, MODIS TPW product briefing

Atmospheric transmission from visible through infrared MODTRAN TM 4: US Standard, nadir view from space to ground, 23 km rural aerosol

Current optical water vapor retrieval methods ,[object Object],[object Object],[object Object],[object Object],[object Object],MODIS bands

Transmission from sensor to a height for MWIR

Review of the physics based sea surface temperature retrieval ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],-log( σ )

Conditions which must be met for the “same temperature criterion” (STC) algorithm to work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

MODIS CWV sensitivity ,[object Object],[object Object],[object Object],Compute transmission in MWIR using MODTRAN TM 4 with water vapor scaling option:

Description of the “same temperature criterion” (STC) algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],MLS T-profile MLS RH-profile

3-band Error σ(T s,est (i,j)) surface after one iteration ,[object Object],[object Object],[object Object],[object Object],[object Object],C RH T off Optimum solution “ *” mark location for optimum RH factor for a fixed temperature offset.

3-band error surface after 3 iterations Red closer to green but a small shift in temperature offset will change the CWV estimate -> Better retrieval! 1 3

3-band Error surface after using 10 pixels 1 6 5 10 Correct solution is closer and retrieved CWV is less sensitive to temperature offset

Conclusion: STC algorithm applied to 3 and 5 MWIR MODIS bands using multiple pixels avoids ambiguity problem ,[object Object],[object Object],[object Object],[object Object],1 6 5 10

De-striping methods applied to MODIS data in the MWIR ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],20 21 22 23 24 25 20 21 22 23 24 25 MODIS-Terra MWIR bands over water MODIS-Aqua MWIR bands over water

MODIS-Aqua: Original (A), Average Intensity Match (B) and Histogram-Match (C) A B C 20 22 23 25 MYD021KM.A2007184.2350.005.2007187000128.hdf

De-striping effect for column water retrieval over water -> The de-striping of MODIS radiance data significantly improves the image quality of the CWV!

Compare MODIS IR CWV product and STC-CWV result ,[object Object],MODIS 5 km x 5 km CWV product ,[object Object],[object Object],[object Object]

Single pixel, 3 band (20, 22 and 23) STC-CWV result for Nile delta ,[object Object],[object Object],Well defined minimum! Pixels within 1-2 g/cm2 are white

Sub-pixel hot-spot detection using MODIS data ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Are these a series of sub-pixel hotpots? Is this an isolated sub-pixel hotspot?

Mixed pixel temperature variance as a function of temperature difference and pixel fill fraction The variance of the retrieved brightness temperature is very sensitive to sub-pixel hotspots!

Examples for HS detection for 2 deg variance ,[object Object],[object Object],[object Object],3 2a 2b 1

So what about the HS in the Nile Delta image? The series of hot areas have a low variance, meaning that they are not sub-pixel hotspots. The isolated hot areas have a variance exceeding 2K and thus are sub-pixel hotspots.

Close-up of the chain of hot-spots Observation: Variance of retrieved surface temperatures is very small (<0.5K) Conclusion: No sub-pixel hot-spot but a chain of lakes which remain warmer than the surrounding land Radiance image of Nile delta

4 Band (20, 22, 23 and 25) hot-spot result near Alexandria, Egypt Finding: σ (T s (i))~3K and T s >32ºC results in a sub-pixel hot-spot

Official MODIS Fire product for 7-3-2007 shows 2 hot-spots

Hotspot retrieval over North Korea using STC-CWV algorithm and Surface temp. T s T s gt 5 º C σ (T s ) σ (T s ) gt 1 º K Detected hotspots (probably fires)

Conclusions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],R=20/22, G=22 B=23/22 MYD021KM.A2007184.2350.005.2007187000128.hdf

Night Water Vapor Borel Spie 8 12 08 White

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