C. J. Tucker

Satellite remote sensing of primary production

Abstract Leaf structure and function are shown to result in distinctive variations in the absorption and reflection of solar radiation from plant canopies. The leaf properties that determine the radiation-interception characteristics of plant canopies are directly linked to photosynthesis, stomatal resistance and evapotran-spiration and can be inferred from measurements of reflected solar energy. The effects of off-nadir viewing and atmospheric constituents, coupled with the need to measure changing surface conditions, emphasize the need for multitemporal measurements of reflected radiation if primary production is to be estimated

A global 1° by 1° NDVI data set for climate studies. Part 2: The generation of global fields of terrestrial biophysical parameters from the NDVI

A coke oven leveling door hatch construction, comprises a hatch pivot bearing adapted to be mounted on the coke oven door or directly adjacent the door. A hatch door for closing a leveling port includes a locking bar extending across the front face thereof which terminates in a forked end having a pair of bearings which engage over the respective ends of the hatch pivot bearing and which are secured to a pivot which extends through the pivot bearing so that the door may be pivoted thereabout. The pivot includes an offset portion or crank arm which is connectable to an opening mechanism which comprises a fluid pressure operated cylinder having a movable piston therein which is connected to a rotatable forked arm which engages the crank to rotate it through an arc to effect turning of the door to open the door. The locking bar includes an inwardly extending portion on the side of the door opposite from the pivot, which terminates in a hook which is engageable by a rotatable arm having a detent which engages with the hook. The arm is biased by a spring to rotate in a direction to cause engagement but the locking bar may be moved against the biasing force to rotate the latching arm having the detent so that the detent moves out of engagement with the hook.

Comparison of Radiative and Physiological Effects of Doubled Atmospheric CO2 on Climate

The physiological response of terrestrial vegetation when directly exposed to an increase in atmospheric carbon dioxide (CO2) concentration could result in warming over the continents in addition to that due to the conventional CO2 “greenhouse effect.” Results from a coupled biosphere-atmosphere model (SiB2-GCM) indicate that, for doubled CO2 conditions, evapotranspiration will drop and air temperature will increase over the tropical continents, amplifying the changes resulting from atmospheric radiative effects. The range of responses in surface air temperature and terrestrial carbon uptake due to increased CO2 are projected to be inversely related in the tropics year-round and inversely related during the growing season elsewhere.

Interannual variations in satellite‐sensed vegetation index data from 1981 to 1991

Normalized difference vegetation index (NDVI) data processed from measurements of advanced very high resolution radiometers (AVHRR) onboard the afternoon-viewing NOAA series satellites (NOAA 7, 9, and 11) were analyzed for spatial and temporal patterns comparable to those observed in atmospheric CO2, near-surface air temperature, and sea surface temperature (SST) data during the 1981–1991 time period. Two global data sets of NDVI were analyzed for consistency: (1) the land segment of the joint NOAA/NASA Earth Observing System AVHRR Pathfinder data set and (2) the Global Inventory Monitoring and Modeling Studies AVHRR NDVI data set. The impact of SST events was found to be confined mostly to the tropical latitudes but was generally dominant enough to be manifest in the global NDVI anomaly. The vegetation index anomalies at latitudes north of 45°N were found to exhibit an increasing trend. This linear trend corresponds to a 10% increase in seasonal NDVI amplitude over a 9 year period (1981–1990). During the same time period, annual amplitude in the record of atmosphere CO2 measured at Point Barrow, Alaska, was reported to have increased by about 14%. The increase in vegetation index data between years was especially consistent through the spring and early summer time periods. When this increase was translated into an advance in the timing of spring green-up, the measure (8±3 days) was similar to the recently published estimate of about 7 days in the advance of the midpoint of CO2 drawdown between spring and summer at Point Barrow, Alaska. The geographical distribution of the increase in vegetation activity was consistent with the reported patterns in springtime warming and decline of snow cover extent over the northern hemisphere land area.

A global 1° by 1° NDVI data set for climate studies derived from the GIMMS continental NDVI data

Abstract A nine-year (1982–1990) global normalized difference vegetation index (NDVI) data set with a spatial resolution of 1° by 1° and a temporal resolution of one month was compiled for use in climate studies. This data set was derived from higher resolution (5–8 km) monthly continental NDVI data sets that have been processed and archived by the Global Inventory Monitoring and Modelling Studies (GIMMS) group at NASA/Goddard Space Flight Center. The continental GIMMS NDVI data sets were calculated from Global Area Coverage (GAC) data collected at daily intervals by the Advanced Very High Resolution Radiometer (AVHRR) onboard the NOAA-7, -9 and -11 satellites The global 1° by 1° NDVI data set was produced to calculate land surface parameters for use within general circulation model J of the atmosphere (GCM). In view of this quantitative application, an evaluation is given of the representation by the NDVI data of the spectral properties of vegetation at the landsurface. Errors are defined as deviations f...

Sensitivity of climate to changes in NDVI

Abstract The sensitivity of global and regional climate to changes in vegetation density is investigated using a coupled biosphere–atmosphere model. The magnitude of the vegetation changes and their spatial distribution are based on natural decadal variability of the normalized difference vegetation index (NDVI). Different scenarios using maximum and minimum vegetation cover were derived from satellite records spanning the period 1982–90. Albedo decreased in the northern latitudes and increased in the Tropics with increased NDVI. The increase in vegetation density revealed that the vegetation’s physiological response was constrained by the limits of the available water resources. The difference between the maximum and minimum vegetation scenarios resulted in a 46% increase in absorbed visible solar radiation and a similar increase in gross photosynthetic CO2 uptake on a global annual basis. This increase caused the canopy transpiration and interception fluxes to increase and reduced those from the soil. T...

Monitoring the grasslands of the Sahel 1984-1985

Abstract Normalized difference vegetation index data obtained from polar-orbiting meteorological satellites were used to compare the growing or rainy seasons of 1984 and 1985 for the Sahelian zone of Africa. A substantial difference was found between these two years, with 1985 generally having higher normalized difference vegetation index values indicating higher levels of primary production in 1985 than in 1984. 1 km data were compared for Senegal, Mali, Niger and Sudan, and 7 km data were compared for sub-Saharan Africa. The qualitative comparison of these data suggests the use of similar data to assist in centralized monitoring of rangeland conditions, to identify areas of deficiencies in primary production and provide synoptic information in support of regional drought monitoring

Mean and inter-year variation of growing-season normalized difference vegetation index for the Sahel 1981-1989

Images are presented that show the mean and coefficient of variation of nine years (1981-1989) of NOAA AVHRR normalized difference vegetation index (NDVI) data for the growing season (July-October) in Africa, north of the equator. The variation in the growing season NDVI is represented by the coefficient of variation image that shows the large variation in the Sahelian growing season between years. It is concluded that these images illustrate some aspects of the perspective being brought to regional and continental scale processes by coarse resolution satellite sensors and the potential of these sensors to provide consistent, long-term datasets.

Satellite remote sensing of rangelands in Botswana II. NOAA AVHRR and herbaceous vegetation

Abstract NOAA-7 Advanced Very High Resolution Radiometer (AVHRR) global-area coverage (GAC) data for the visible and near-infrared bands were used to investigate the relationship between the normalized difference vegetation index (NDVI) and the herbaceous vegetation in three representative rangeland types in eastern Botswana. Regressions between Landsat MSS band-7/band-5 ratios and field measurements of the cover of the live parts of herbaceous plants, above-ground biomass of live herbaceous plants and bare ground were used in conjunction with MSS data in order to interpolate the field data to 144 km2 areas for comparison with blocks of nine AVHRR GAC pixels. NOAA NDVI data were formed into 10-day composites in order to remove cloud cover and extreme off-nadir viewing angles. Both individual NDVI composite data and multitemporal integrations throughout the period May 1983-April 1984 were compared with the field data. In multiple linear regressions, the cover and biomass of live herbaceous plants and bare ...

A Revised Land Surface Parameterization (SiB2) for GCMS. Part III: The Greening of the Colorado State University General Circulation Model

Abstract SiB2, the second-generation land-surface parameterization developed by Sellers et al., has been incorporated into the Colorado State University general circulation model and tested in multidecade simulation. The control run uses a “bucket” hydrology but employs the same surface albedo and surface roughness distributions as the SiB2 run. Results show that SiB2 leads to a general warming of the continents, as evidenced in the ground temperature, surface air temperature, and boundary-layer-mean potential temperature. The surface sensible heat flux increases and the latent heat flux decreases. This warming occurs virtually everywhere but is most spectacular over Siberia in winter. Precipitation generally decreases over land but increases in the monsoon regions, especially the Amazon basin in January and equatorial Africa and Southeast Asia in July. Evaporation decreases considerably, especially in dry regions such as the Sahara. The excess of precipitation over evaporation increases in the monsoon re...