Environment '93
              Symposium on Remote Sensing in Environmental
                      Research and Global Change  
                        3-6 March 1993  Hong Kong
     Representatives  from China, Japan, Hong Kong, Norway, Taiwan and the United States met 
in a Symposium and Workshop on remote sensing instrumentation and applications for use in 
environmental studies, focusing where possible on examples from the western Pacific. Some 20 papers 
were presented orally (21 in the Proceedings Volume) over two days on the 3-4 March 1993 at the 
Hong Kong University of Science and Technology.  An additional half-day on 6 March 1992 was used 
for a discussion Workshop.  Major topics included Application in Oceanographic Research ( 9 papers) 
and Global Change (8 papers). Highlights included summaries of future programs such as SeaWifs, new 
and developing instrumentation such as SAR with proposed applications to climatic and nvironmental studies, 
and discussions of techniques of validation of satellite data (sea truthing by ships, buoys, sondes etc.) and 
verification of algorithms. 
Pat Wilde
The new Hong Kong University of Science and Technology (HKUST) was the site and the host of Environment '93: Symposium on Remote Sensing in Environmental Research and Global Change held from 3 to 6 March 1993. The purpose of the Symposium was two fold: (1) to assess the status of environmental remote sensing both globally and specifically in the east Asian area; and (2) to see what role the new University might play in the development of remote sensing research. The Hong Kong University of Science and Technology is still building in the Kowloon hills on Clear Water Bay and is now only in its second year of operation. It presently has 2500 students with a target of 7 to 8,000 students and a student-faculty ratio of 11-1. In fact, this symposium opened the second phase of the initial three phase construction of the new campus. Uniquely funded by funds from the Hong Kong Jockey Club, the university is growingrapidly, hiring some 10 faculty per month. The facilities are both new and very high technology with all class rooms and even the student dormitory rooms connected with a optical fiber LAN network.
The symposium consisted of two days of formal presentations followed by a half-day workshop whose objective was "to identify and summarize the potential contributions of remote sensing technology to environmental issues in the western Pacific region during the next five to ten years".
The program was divided into four sessions: Keynote Speech; Overview (3 papers); Applications in Oceanographic Research (9 papers); and Global Change (8 papers).
Dr. John S. Theon, chief, Atmospheric Dynamics, Radiation and Hydrology Branch, Earth Science and Application Division of NASA talked on "The NASA Earth Observation Program: Global Change and Remote Sensing". His address focused on NASA's "Mission to Planet Earth" whose objective is to make the long-term observations required to ascertain the impact current changes will have on the climate. The goal is to be achieved through analysis of observations, modeling, and eventually predicting climate and climate change. The observations, per force, must be by remote sensing as the only practical scheme to observe the whole earth for a decade or more to establish the baseline for estimating the changes. Dr. Theon described the varioussystems to be used in the program and called for international co-operation in implementing the program.
Unfortunately, like many so-called high technology approachs to assess Earth scale issues, this program tends to ignore previous work and other disciplines for the sake of instrumentation. NASA's Mission to Planet Earth has a serious flaw in ignoring the geologic record of climate change. As bad or as incomplete as the geologic record is, is the only real record of the Earth's climate. Suggesting that even a ten year record of real time observations, although unquestionably needed, can act as a baseline to assess climatic processes with time scales of various lengths is scientific grantsmanship of the first order.
The planned overview talk by Dr. Xinnian He of the Institute of Remote Sensing of Application of the Chinese Academy of Sciences was not given orally. The talk was included in the proceedings and discusses "Airborne Remote Sensing System of Chinese Academy of Sciences (CASARSS)". The system uses two Cessna Citation S/II airplanes as the platform. The instruments flown include: 19-channel infra-red, thematic infra-red, thermal infra-red, 64-channel imaging spectrometer, multi-band camera, X-band side-looking real aperture radar (SLAR), synthetic aperture radar (SAR), airborne spectrometer, X-band scatterometer, multi-band microwave radiometer, and a laser altimeter. The instruments are connected by a micro-computer based monitoring system. The complete system is used is resource studies, environmental monitoring, urban management, disaster monitoring, crop estimation as well as in research.
Prof. Cho-Teng Liu, of the National Taiwan University, gave the overview talk on "Remote Sensing in Oceanographic Research in Taiwan". The program which began in the 1980's combined both airborne and satellite data for applied purposes. Airborne techniques were used to monitor power plant effluent, long-shore sediment drift and plumes from polluted rivers. Satellite information was used to "show the erosion and accretion of offshore sand bars". More recently, NOAA data has been used to study sea surface temperatures chiefly in the region north of Taiwan where a cold water dome is a region of high nutrient content, and thus a area of great fishing potential. Studies are on-going on the interaction of the thermal dome and the Kuroshio current. This intensive observation program (IOP) is scheduled for September 1992 and March 1993. Studies are also on-going west of Taiwan looking at the boundaries between the China Coastal Current and a branch of the Kuroshio. Sea surface temperature anomalies monitored by satellite are being used to trace these current interactions.
The last overview presentation was by Dr. A. T. C. Chang of NASA's Hydrological Sciences Branch on "Space-borne Remote Sensing Sensor- Past, Present and Future". The talk gave a brief history of various packages starting with TIROS-1 in 1960. Optical sensors discussed include: Advanced Very High Resolution Radiometer (AVHRR), Multi-Spectral Scanner (MSS), Return Beam Vidicon (RBV) camera, Thematic mapper (TM) and the up-coming Moderate Resolution Imaging Spectrometer (MODIS) which has 36 spectral bands from 0.4 to 14.2 micrometers. Thermal infrared sensors mentioned include: Advanced Space-borne Thermal Emission and Reflective Radiometer (ASTER) for the Earth Observation System (EOS) series of satellites. The ASTER system will have a resolution of 15 to 90 meters and be operated in three visible and near infra-red (VNIR) bands between 0.5 and 0.9 micrometers; six short-wave infra-red (SWIR) channels between 1.6 and 2.5 micrometers; and five thermal infra-red bands between 8 and 12 micrometers. Microwave sensors mentioned include: Electrically Scanned Microwave Radiometer (ESMR) and Nimbus E Microwave Spectrometer (NEMS) from Nimbus- 5; Scanning Multi-channel Microwave Radiometer (SMMR) from Nimbus-7 and Seasat-A; the Defense Meteorological Satellite Program-Special Microwave Imager (DMSP-SSM/1); and for EOS, the Multichannel Imaging Microwave Radiometer (MIMR). The MIMR system will operate in six frequencies in the range of 6.8 to 90 Gigahertz, with a swath width of 1400 kilometers and an incidence angle of 50 degrees to provide three day coverage of the Earth. This system will provide much needed hydrologic data. Future developments are expected in lidar for atmospheric sounding using Raman scattering.
These series of sessions was led off by Prof. James Yoder of the University of Rhode Island discussing the 'Scientific Applications of Sea Wide Field Sensor (SeaWifs) Imagery. This system to be launched in August 1993 is sponsored by a private company Orbital Sciences Corporation, which will sell the real-time high resolution (1 kilometer) wide-band ocean color scanner data. Qualified researchers will be able to obtain 4 kilometer data in non-real time relatively cheaply. SeaWifs will have the same visible bands as the Coastal Zone Color Scanner (CZCS) which died in 1986, with bands centered near 443, 520, 550, 670 nanometers and two additional visible bands at 412 and 490 nanometers plus additional near infra-red channels at 765 and 865 nanometers. The additional channels will be used to assess the atmospheric correction and chlorophyll algorithms. The orbit is set to provide two-day coverage for any location on Earth. Prof. Yoder presented some data on coccolith blooms in the Atlantic obtained from analysis of the CZCS satellite pictures as an example of how such data may be used in climate studies. Coccoliths are a major fixer of carbon dioxide in the ocean converting it into calcium carbonate much of which is deposited on the sea floor, thus removing it from the short term atmospheric cycle.
Prof. Dana Kester, also of the University of Rhode Island, presented a paper entitled "Chemical and Biological Remote Sensing of the South China Sea: Satellite and in situ Observations". The Coastal Zone Color Scanner (SZCS) images were reexamined in this region and monthly "nearly cloud-free images" were reconstructed. The South China Sea has highly variable color sources including chlorophyll, suspended particles from rivers, and organic substances "yellow substances or Gelbstuffe" etc. Due to the lack of in situ data, it was difficult to separate out the components just using the standard chlorophyll algorithm. This is particularly valid for the apparent color "high" values in December, which intuitively seem unrelated to biological activity. An appeal for Volunteer Observing Ships (VOS) with automated analysis for chlorophyll and nutrients and expendable drifting buoys was made to be put in place before the SeaWifs data comes on line, so that the remote sensing data can be calibrated better for local conditions.
Prof. Delu Pan, of the Second Institute of Oceanography, People's Republic of China, continued on the previous theme of the problem of a proper color algorithm to interpret satellite data in his paper "Ocean Colour Remote Sensing for Marine Environment". He reviewed the various algorithms of the three major color contributors and suggested that inverse modelling might be used to separate out the effects of each. Various examples of the use of ocean color were shown from off the Minjiang River into the East China Sea, off Vancouver Island, Canada, the Gulf of Bohai and coastal waters of China, and in the North Sea off Germany. Inverse modelling was applied to the North Sea data. Again, the plea for more and more geographically consistent and persistent Sea Truth data was made.
Dr. Akira Harashima of the National Institute for Environmental Studies, Japan showed how such Sea Truth measurements are being made by "Continuous Marine Biogeochemical Monitoring by Japan-Korea Ferry Boat for the Validation of Ocean Color Remote Sensing". This operation using a Volunteer Observing Ship (VOS) which travels twice weekly between Kobe, Japan to Pusan, Korea covers about 200 kilometers. The parameters monitored are sea water temperature, salinity, pH, fluorescence, and dissolved nutrients (nitrite, nitrate, ammonia, phosphate, and silica). The pumps run at 15 to 20 liters per minute and the chemicals are automatically sampled at a spatial rate of about 100 meters with the mean ship speed at 20 knots. The filtered samples are analyzed back at the laboratory and not on shipboard. This is an excellent example of both international co-operation, in this case between Japan and Korea, and obtaining baseline data prior to the launch of SeaWifs.
Not presented orally, but included in the Proceedings was a paper by Dr. Xuelian Chen and Dr. Dan Luo of the Scientific Research Institute, Pearl River Water Resources Commission on "Remote-Sensing Analysis of the Environmental Change in the area of the Pearl River Estuary, Hong Kong and Macao". This paper briefly discusses the enormous changes in the Pearl River Estuary due to development of shore based industrial and land reclamation projects and attendant water pollution. Remote sensing techniques are being used to monitor both the natural changes and variations due to tides etc. as well and man-made effects on sediment transport, nutrient supply, and pollution. Crisp color photographs taken by satellite and high flying aircraft using various sensors illustrate the conditions in the estuary.
Dr. Antony K. Liu of the NASA/Goddard Space Flight Center discusses "Synthetic Aperture Radar of Ocean Applications". This technique called SAR measures microwave backscatter and can be used to distinguish surface and internal waves, wind patterns, oceanic fronts, films, water current fields, shallow bottom topographic features, and mesoscale eddies. This method unlike visible band sensors, is not affected by clouds or darkness and thus is very useful not only in normally cloudy areas but in high latitude winters where daylight hours are short or non-existent. A SAR instrument has been up and running since July 1991 on the ERS-1 satellite. An example of the application of SAR data was given for the Fisheries Oceanography Coordinated Investigation (FOCI) carried out in the Gulf of Alaska, for the identification of eddies, fronts, and currents that transport larvae to the various nursery fishery grounds in the area. Real-time SAR images were used for the development of recruitment models.
Continuing the theme of operations using SAR in high latitude where both clouds and visible light can be limited, Dr. Johnny A. Johannessen of the Nansen Environmental and Remote Sensing Centre, Bergen, Norway, gave an example of "Monitoring and Modeling of the Marine Coastal Environment: A conceptual View for the Future". He gave the results of the Norwegian Continental Shelf Experiment (NORCSEX'91) which was a validation experiment of the ERS-1 SAR images off the coast of Norway. Several examples were given of the combined use of satellite images in real time to vector research ships to validate features seen on the images. SAR images are able to distinguish features such as water current fronts and eddies, natural slicks and oil spills, internal waves, the wave length and travelling direction of wind waves and swell, as well as wind fronts and wind patterns. Dr. Johannessen and his group are proposing to integrate satellite SAR and other sensor images such as from SeaWifs and TOPEX-Poseidon, with ship-board measurements to provide a more complete physical-chemical-biological monitoring scheme in this area.
A discussion of the finer scale oceanographic features was provided by Prof. Jin Wu of the Air-Sea Interface Laboratory of the University of Delaware. Prof. Wu described his test facilities including an at-sea tower which is used to validate various instruments and "tune" algorithms related to wind-wave phenomenon. His group is looking at three types of remote sensors: altimeters, scatterometers, and radiometers. Altimeters are sensitive to microwave return from ripples. Scatterometer values are shown to be related to the Bragg equation and are a function of the wave number slope spectrum. This devise can be used to "measure" oil pollution as films damp waves. Altimeters also may be able to distinguish actually rain falling on the ocean as rain drops suppress wave action.
Sea truthing of various satellite sensors using of buoys and ship observations was presented by Prof. Hiroshi Kawamura of the Center for Atmospheric and Oceanic Studies of Tohoku University, Japan in the paper: "Validation Results of the Satellite-derived parameters for the Oceanography in the North Western Pacific Ocean". The comparison with satellite data are made from data from four Ocean Data Buoys (three in the Pacific ocean and one in the Sea of Japan) arrayed around Japan and from the Ocean Mixed Layer Experiment (OMLET) cruises. The buoys measure 11 variables every three hours. On the cruise physical data and radiation fluxes were measured south of Honshu Island. The results were: Short Wave Radiation- rms error = 20 Watts per square meter; Cloud Amount- rms error = 10.5%; Long Wave Radiation- rms error = 14 Watts per square meter; Sea Surface Temperature Multi Channel Sea Surface Temperature (MCSST)- high resolution data rms error = 0.43 degrees Celsius, global (weekly average) = 0.98 degrees Celsius; Wind Speed from GEOSAT Altimeter- rms error = 2.1 meters per second; Wind Speed from Special Scanning Microwave Imager SSMI on the Defense Meteorological Satellite Program (DMSP) satellite- rms error = 2.21 meters per second; Wind Vector from Active Microwave Instrument (ARI): Wind Speed- rms error = 1.90 meters per second, Wind Direction- rms error = 44.2 degrees; Atmospheric Water Vapor by SSMI/DMSP- rms error = 1.48 grams per kilogram.; Wind Waves by GEOSAT Altimeter- rms error = 0.48 meters.
Dr. William P. Chu of NASA Langley Research Center gave the first talk in the Global Change Sessions, on "Remote Sensing using the Solar Occulation Techniques". He discussed the results of data from the Stratospheric Aerosol Measurement II (SAM II) and Stratospheric Aerosol and Gas Experiment I (SAGE I) measuring globally the vertical distribution of aerosol, ozone, water vapor, nitrogen dioxide and cirrus clouds. This method differs from other systems which have to be validated from ground bases, in that the calibration light source is the sun and the technique is self-calibrating. Other validations of the profiles have been made using lidar and balloon and rocket sondes. Dr. Chu presented some interesting profiles of the spreading of aerosols from Mount Pinatubo based on such measurements, indicating their use in global climatic studies.
Focusing on earth-surface derived ozone measurements, Dr. Jack Fishman, also of NASA- Langley Research Center, presented a talk on "Identification of Global Smog deduced from analyses of satellite data sets and Ozonesonde measurements". Tropospheric ozone, dubbed Global Smog, has been monitored using the Total Ozone Mapping Spectrometer (TOMS) and from SAGE, discussed in the previous talk by Dr. Chu. Total ozone in the atmosphere is 300 Dobson units (1 D.U. = 2.69 * 10^16 molecules of ozone per square centimeter). Of interest, is the high anthropogenic contribution of ozone at low latitudes caused by agricultural burning, both from development of new agricultural land by burning the rain forests but also by annual burning of stubble etc. of existing fields. This is a common practice in the tropics both to fertilize the generally poor soil and to prepare the fields for new plantings. This explains the high values of ozone spotted by satellites over Ascension Island in the middle of the South Atlantic far from industrial sources of ozone concentrated in the Northern Hemisphere.
Dr. William K. M. Lau of NASA-Goddard Space Flight Center discussed the use of satellite in probing the hydrologic cycle by measurements of water vapor. Using El Nino-Southern Oscillation (ENSO) as an example, Dr. Lau discussed the various instruments and programs to monitor climate and the global hydrologic cycle. Sea surface temperatures are derived from infra-red sensors such as NOAA's Advanced Very High Resolution Radiometer (AVHRR), TIROS Operational Vertical Sounder (TOVS) and microwave instruments like the Scanning Multichannel Microwave Radiometer (SMMR). The advantage of microwaves sensors are that they can see through clouds, which are present over large areas of the surface. Precipitation can be estimated using a combination of visible and infra-red techniques; although the present methods have serious problems and are difficult to validate. Global precipitation maps have been produced from data from Electrically Scanning Microwave Radiometer (ESMR) from Nimbus-5, (SMMR) from Nimbus-7, and SSM/I from the Japanese Defense Meteorological Satellite Platform. It is hoped that the Tropical Rainfall Measuring Mission (TRMM) which is a joint US- Japan effort scheduled for 1996 will improve the techniques. Evaluation of the effect of clouds continue to be a major unsolved problem in the determination of surface radiation budgets. The different types and altitude of clouds have various impacts on the heat balance, not always in the same direction. Cloud classification algorithms have been developed from the Nimbus-7 Temperature Humidity Infrared Radiometer (THIR) and from TOMS. This general problem is being studied by the International Satellite Cloud Climatology Project (ISCCP). As wind speed has a major effect on evaporation, sensing of this parameter is also critical to the development of climatic models. In general this is estimated by microwave backscatter using various scatterometers. Sea level, which is important in geostrophic ocean circulation models is monitored by satellite altimeters. On the global scale, knowledge of the circulation at various time scales is important to the understanding of the heat flux and long term climatic effects.
Following the theme of the previous paper, Dr. W. Timothy Liu of the Jet Propulsion Laboratory of the California Institute of Technology focused attention on "Spaceborne Scatterometer in synergistic studies of Global Change". He discussed the NASA scatterometer (NSCAT) which will be launched with the Japanese Advanced Earth Observing Satellite (AEDOS-1) scheduled for launch in 1996. This system with the Advanced Microwave Scattering Radiometer (AMSR) planned for AEDOS-2 will measure sea surface temperature, surface wind speed, water vapor under clear and cloudy skies. From these measurements, evaporation and precipitation can be computed. These measurement combined with the proposed Ocean Color and Temperature Scanner (OCTS) and the Global Imager (GLI) also planned for the AEDOS satellites will add the capability to observe the ocean's thermal and biological response to the surface wind-driven forcing. Tests were run comparing temperatures derived from two wind stress field evaluations (SSMI and the European Center for Medium Range Forecast:: ECMRF) for the Ocean General Circulation Model (OGCM) spun up for 3.5 years to reach a quasi- equilibrium seasonal cycle. The AVHRR temperature data were used as the standard for observation. Agreement for sea surface temperature was good polar-ward of the sub-tropics (above 15 degrees) but was poor in the equatorial zone.
The ever present problem of clouds and their formation was addressed by Dr. Man Li Wu of NASA-Goddard Space Flight Center in her presentation: "Effect of Pollution on Cloud Condensation Nuclei, Cloud Properties and Rainfall". The results of eight cruises in the western tropical Pacific on the PRC research ship XIANGYANGHONG 14, studying aerosols and then comparing this data with cloud observations from satellites was discussed. The aerosols trapped were chiefly sulfates with biogenic sulfate particles 12% (El Nino- warm anomalies) and 40% (La Nina - cold anomalies) of the concentration of anthropogenic sulfate particles. On a much smaller spatial scale from the above regional and global discussions in the above papers, Dr. Robert L. Spellicy of Radian Corporation described systems for detection of speciated organics etc. in the environmental monitoring of industrial chemical plants, stack effluent, petroleum refineries, etc. His paper: "Ground-Based Optical Remote Sensing for Environmental Applications" discussed the use of optical "fences" which surround the plant, reactor vessel etc to provide serial data for emission monitoring, detecting of fugitive emissions and accidental release. The fences can use both or either infra-red and ultra-violet spectroscopic methods depending on the need. Commercial units available include Fourier Transform Infrared (FTIR) and Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS) and Gas Filter Correlation (GFC) spectrometer system. Other systems under consideration are Non-Dispersive Infrared (NDIR), Lidar systems (DIAL) and diode laser systems. Many of these systems are being used in advance of any legal requirement as a defense against lawsuits as well as a method to improve plant efficiency and maintenance. Distances up to one kilometer can be covered by one set of detectors.
Dr. Tung Fung of the Chinese University of Hong Kong examined a local application of remote sensing in his presentation: "An Assessment of Hill Fire Impact in Country Parks with spot HRV images". Some 40% of the land area of Hong Kong is park land. With its high population, it is imperative for Hong Kong to maintain these parks for recreations purposes. Hill fires are significant problem. This discussion was on the use of SPOT High Resolution Visual images to make a geographically useful data base to develop a fire prevention strategy. The multi-spectral images are classified by vegetative types, etc. and merged with topographic and cultural information onto a computer retrievable spatial data base. Prior and frequent burn areas along with types of vegetation burned are thus identified.
The final paper of the formal sessions was by Dr. Fuk Li of the Jet Propulsion Laboratory of the California Institute of Technology on "Spaceborne Imaging Radars for Earth Remote Sensing". This provided a brief summary of activities on Synthetic Aperture Radars (SAR) at the Jet Propulsion Laboratory. The latest system is the shuttle borne imaging radar (SIR) model C (L and C band) which will be used in conjunction with the European developed X-band SAR (XSAR) in future space shuttle flight scheduled in 1994. SAR systems have the potential to monitor ecosystem dynamic studies including green biomass to total biomass, the now difficult to measure- soil moisture, plus fine scale mapping of sea ice (ice type, age and concentration). The data intensive processing requires complex facilities at a ground station such as the present one in Alaska mentioned in the above paper by Dr. A. K. Liu.
The meeting was ended by a half-day workshop with the objective "to identify and summarize the contributions of remote sensing technology to environmental issues in the western Pacific region during the next five to ten years". The panel included Dr. Dana Kester as Chair; Jay-Chung Chen, Hong Kong University of Science and Technology; Akira Harishima, National Institute for Environmental Studies, Japan; Huasheng Hong, Hong Kong University of Science and Technology; Johnny A. Johannessen, Nansen Environmental and Remote Sensing Centre, Norway; Cho-Teng Liu, National Taiwan University; Delu Pan, Second Institute of Oceanography, People's Republic of China, and John S. Theon, NASA, USA. Each panelist gave a brief summary of his views and experience emphasing (1) problems, (2) existing capabilities, (3) planned enhancements, and (4) obstacles. These findings will be produced in a final report to HKUST. Some of the problems discussed included the non-availability of the Japanese satellite data to anyone except the original investigators. This was perceived as a "start-up" problem which will eventually be solved permitting open use. There was a discussion of the availability of SeaWifs real-time data for science purposes including a special license at a discount from the commercial rate.
The tenor of the meeting was optimistic with both near-term and long-term co-operation among the scientists of many nations seemingly assured. Unquestionably the United States and NASA is the technological leader in both hardware and analytical use. However, Japan and eventually China are developing a significant role as their own programs mature. Both China and Japan are taking a healthy inquiring stance with respect to interpretation, particularly with respect to color imagery algorithms running validation tests. One difference between the attendees from the US and the other countries was the predominance in the US delegation of satellite instrument and theoretical people, whereas the other countries were represented by actual environmental users of the data. This may be a deja vu feeling of another technology transfer of US instrumental know-how, while the actual applied uses of the data are developed elsewhere. This, I am sure, reflects the partition of funds in these countries. As a marine scientist as well as a geologist, I am concerned that not enough attention or money is paid in the US to fields with experience in the environment in favor of high-tech rhetoric to support instrument development glibly directed towards poorly defined "climatic" problems. Here in Asia and also apparently in Europe, application of remote sensing data seems to take precedence over newer and better gizmos. Obviously both approachs should be balanced if actual environmental problems are to be ameliorated. The Hong Kong University of Science and Technology is to be congratulate for putting on such a professional international meeting at such a young school. The size was just about right as I was able to talk to a fair number of the participants, including the observers from the Hong Kong environmental agencies. For those interested, a copy of the bound proceedings including many color photographs is available from the University at $235 HK per copy. That is about $30 US and so is a real bargain thanks to the Jockey Club and the Hong Kong Chamber of Commerce that partially funded the conference.