Conformidade entre dados biofísicos orbitais e terrestres para o zoneamento agroclimático, identificação espaço-temporal de tendências de precipitação e suas relações com uso e cobertura da terra no bioma cerrado
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2021-09-10
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Universidade Federal de Goiás
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Context
The Cerrado biome plays a prominent role in Brazilian and global agricultural production, where approximately 50% of the national agricultural production and 30% of the country's gross agricultural income are in this biome. The Climatic Risk Agricultural Zoning (ZARC) arises as an important instrument of the Brazilian agricultural policy by indicating more favorable dates of crop planting on a municipal scale. The improvement of the methodology used in ZARC is of paramount importance and should be carried out continuously. Altitude and temperature are important agricultural conditions, with altitude being one of the factors used for the calculation of temperature by utilizing regression equations. As for the precipitation data, they are factored in the modeling of the water balance of different agricultural crops in ZARC.
Goals
In this context, the current study aims to analyze the conformity/accuracy between the altitude and precipitation data obtained from terrestrial reference stations and estimated by orbital sensors, and to identify trends of increase or decrease of precipitation in the Cerrado biome, itemized by classes of land use and land cover.
Materials and methods
The digital elevation models (MDEs) analyzed were NASADEM_HGT from NASA and ALOSAW3D30 version 3.1 from the Japan Aerospace Exploration Agency (JAXA), both with a spatial resolution of 30 meters. These models were evaluated according to the parameters recommended in the Cartographic Accuracy of Digital Cartographic Products Standard (PEC-PCD), which defines tolerances according to the evaluation scale and classes (A, B, C, or D). NASA's IMERG Final Run Global Precipitation Measurement (GPM) data, available every half hour, were compared with the hourly measurements of 215 automatic surface weather stations of the National Institute of Meteorology (INMET) of the Cerrado biome in the 2017-2019 period. In addition, considering the period from 2000 to 2019, areas of precipitation tendency were identified in the biome and compared to the predominant classes of land use and land cover, obtained by the MapBiomas project.
Results
Considering class A of the PEC-PCD, MDE NASADEM_HGT was compatible with 1:250,000 scales and smaller, while MDE ALOS AW3D30 reached scales of 1:100,000 and smaller. When compared to each other, the models provide close and similar altitude measurements and may be used in ZARC.
There was great conformity between GPM precipitation data and data from automatic weather stations, notably for months of the dry season (May to September), especially June, which showed the best performance (0.89), high agreement (0.96), and very strong positive correlation (0.93). All the evaluation indices that were considered, that is, detection probability, false alarm rate, critical success rate, and correct percentage, demonstrated a high ability to detect rain via orbital data.
For the 2000 - 2019 period, it was possible to notice that the dry season in the biome is being intensified. Approximately 20% of the Cerrado that is covered with native vegetation showed a trend of statistically significant reduction of precipitation of -2.58 mm/month and -2.55 mm/month in 12% of the total area of Cerrado with anthropic cover. The areas that presented significant positive precipitation trends occupied 5% of the Cerrado (around 5 mm/month of increase).
Final considerations
The results of this study showed that the MDEs and the GPM data have great potential to be incorporated into the ZARC methodology, especially to complement the historical series of data from surface rainfall stations. More in-depth studies need to be conducted to analyze the trend of increase or decrease in precipitation with possible relations with changes in the land use and land cover of the biome.
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BETTIOL, Giovana Maranhão. Conformidade entre dados biofísicos orbitais e terrestres para o zoneamento agroclimático, identificação espaço-temporal de tendências de precipitação e suas relações com uso e cobertura da terra no bioma cerrado. 2021. 199 f. Dissertação (Mestrado em Ciências Ambientais) - Universidade Federal de Goiás, Goiânia, 2021.