A Global Land Data Assimilation System (GLDAS) has been developed. Its purpose is to ingest satellite- and ground-based observational data products, using advanced land surface modeling and data assimilation techniques, in order to generate optimal fields of land surface states and fluxes. GLDAS is unique in that it is an uncoupled land surface modeling system that drives multiple models, integrates a huge quantity of observation-based data, runs globally at high resolution (0.25°), and produces results in near–real time (typically within 48 h of the present). GLDAS is also a test bed for innovative modeling and assimilation capabilities. A vegetation-based “tiling” approach is used to simulate subgrid-scale variability, with a 1-km global vegetation dataset as its basis. Soil and elevation parameters are based on high-resolution global datasets. Observation-based precipitation and downward radiation and output fields from the best available global coupled atmospheric data assimilation systems are employe...

The Global Land Data Assimilation System

An overview of MODIS Land data processing and product status

[1] The hydrological budget of Himalayan rivers is dominated by monsoonal rainfall and snowmelt, but their relative impact is not well established because this remote region lacks a dense gauge network. Here, we use a combination of validated remotely-sensed climate parameters to characterize the spatiotemporal distribution of rainfall, snowfall, and evapotranspiration in order to quantify their relative contribution to mean river discharge. Rainfall amounts are calculated from calibrated, orbital, high-resolution Tropical Rainfall Measurement Mission data, and snow-water equivalents are computed from a snowmelt model based on satellite-derived snow cover, surface temperature, and solar radiation. Our data allow us to identify three key aspects of the spatiotemporal precipitation pattern. First, we observe a strong decoupling between the rainfall on the Himalayan foreland versus that in the mountains: a pronounced sixfold, east-west rainfall gradient in the Ganges plains exists only at elevations <500 m asl. Mountainous regions (500 to 5000 m asl) receive nearly equal rainfall amounts along strike. Second, whereas the Indian summer monsoon is responsible for more than 80% of annual rainfall in the central Himalaya and Tibetan Plateau, the eastern and western syntaxes receive only ∼50% of their annual rainfall during the summer season. Third, snowmelt contributions to discharge differ widely along the range. As a fraction of the total annual discharge, snowmelt constitutes up to 50% in the far western (Indus area) catchments, ∼25% in far eastern (Tsangpo) catchments, and <20% elsewhere. Despite these along-strike variations, snowmelt in the pre- and early-monsoon season (April to June) is significant and important in all catchments, although most pronounced in the western catchments. Thus, changes in the timing or amount of snowmelt due to increasing temperatures or decreasing winter precipitation may have far-reaching societal consequences. These new data on precipitation and runoff set the stage for far more detailed investigations than have previously been possible of climate-erosion interactions in the Himalaya.

Toward a complete Himalayan hydrological budget: Spatiotemporal distribution of snowmelt and rainfall and their impact on river discharge

Mapping paddy rice agriculture in southern China using multi-temporal MODIS images

Information on the area and spatial distribution of paddy rice fields is needed for trace gas emission estimates, management of water resources, and food security. Paddy rice fields are characterized by an initial period of flooding and transplanting, during which period open canopy (a mixture of surface water and rice crops) exists. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the NASA EOS Terra satellite has visible, near infrared and shortwave infrared bands; and therefore, a number of vegetation indices can be calculated, including Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI) that is sensitive to leaf water and soil moisture. In this study, we developed a paddy rice mapping algorithm that uses time series of three vegetation indices (LSWI, EVI, and NDVI) derived from MODIS images to identify that initial period of flooding and transplanting in paddy rice fields, based on the sensitivity of LSWI to the increased surface moisture during the period of flooding and rice transplanting. We ran the algorithm to map paddy rice fields in 13 provinces of southern China, using the 8-day composite MODIS Surface Reflectance products (500-m spatial resolution) in 2002. The resultant MODIS-derived paddy rice map was evaluated, using the National Land Cover Dataset (1: 100,000 scale) derived from analysis of Landsat ETM+ images in 1999/2000. There were reasonable agreements in area estimates of paddy rice fields between the MODIS-derived map and the Landsat-based dataset at the provincial and county levels. The results of this study indicated that the MODIS-based paddy rice mapping algorithm could potentially be applied at large spatial scales to monitor paddy rice agriculture on a timely and frequent basis. (c) 2005 Elsevier Inc. All rights reserved.

/pdf/mapping-paddy-rice-agriculture-in-southern-china-using-multi-4h0e4vl40l.pdf

https://ntrs.nasa.gov/api/citations/20010069265/downloads/20010069265.pdf

MODIS snow-cover products

https://modis-snow-ice.gsfc.nasa.gov/uploads/pap_R_consid03.pdf

Consideration of the errors inherent in mapping historical glacier positions in Austria from the ground and space (1893-2001)

Ground-based measurements on the Pasterze Glacier and the Kleines Fleisskees, located in the eastern Alps of Austria, have shown that these glaciers have receded significantly. Landsat Thematic Mapper (TM) data of these glaciers were acquired in August of 1984,1986,1988 and 1990, and have been studied in detail. The 1984–1990 retreat of the Pasterze Glacier has been measured using digital TM data, but the 1984–1988 retreat of the Kleines Fleisskees has not been observed using the TM data because the magnitude of recession between 1984 and 1988 was small relative to the resolution of the TM data. Significant increases in the area of exposed ice (icc facies) on both the Pasterze Glacier and the Kleines Fleisskees were observed and measured using TM data acquired in early August from 1984 to 1988. The area of the Pasterze Glacier and Kleines Fleisskees basins, as measured using TM data, is 20·8±1·02km2 and 1·56±0·188 km2, respectively. The percentage of the Pasterze Glacier comprised of bare ice inc...

Observations on glaciers in the eastern Austrian Alps using satellite data

It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle.

Glacier recession in Iceland and Austria

What were the indigenous agricultural and population patterns in peninsular Malaysia's southern lowlands? What factors produced these patterns? Based on our analysis of ethnographic and historical evidence, as well as aerial photographs taken in 1948 in the Tasek Bera and Sungai Bera watersheds, the Semelai, an Orang Asli group, had a robust and productive subsistence agricultural system emphasising rice but insured by cassava. These photographs, from the P.D.R. Williams-Hunt Collection, provide an unusual record of Semelai agriculture prior to settlement in 1954 and contribute to our knowledge of indigenous economic patterns in the southern lowlands, which have received little ethnographic attention.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022463409000071

Klaus J. Bayr

Papers

MODIS snow-cover products

Consideration of the errors inherent in mapping historical glacier positions in Austria from the ground and space (1893-2001)

Observations on glaciers in the eastern Austrian Alps using satellite data

Glacier recession in Iceland and Austria

Semelai agricultural patterns: Toward an understanding of variation among indigenous cultures in southern peninsular Malaysia