松岡 延浩

Dakhla Oasis is the most highly populated oasis in Egypt. Although the groundwater resource is very large, there is essentially no rainfall and the aquifer from which the water is drawn is not recharged. Therefore, for the future development and sustainability of Dakhla Oasis, it is important to understand how land and water are used in the oasis and meteorological conditions there. In this study, meteorological and satellite data were used to examine the recent agricultural situation and water use. The results showed that the meteorological conditions are suitable for plant production, and the maximum vegetation index value was comparable to the Nile delta. The cultivated area increased between 2001 and 2019 by 13.8 km(2) year(-1), with most of the increase occurring after the 2011 revolution (21.2 km(2) year(-1)). People living in Dakhla Oasis derive their income primarily from agricultural activity, which requires abundant water. Thus, the increasing demand for water is likely to put pressure on the groundwater resource and limit its sustainability.

In Asia, sand dust storm (SDS) occurs nearly every year, especially in northern China. However, there is less research about the relationship between SDS and greenhouse gases (GHGs). In this paper, we select 4 times of SDS that occurred in the spring of 2009 and 2010 in Asia. We monitor the areas covered by the SDS using MODerate resolution Imaging Spectroradiometer (MODIS) data, and then we use Greenhouse Gases Observing Satellite (GOSAT) data to check how the SDS affect the concentration of CO2 and CH4. Compare the concentration of CO2 and CH4 on SDS days with the monthly mean values of the SDS happened month. We also compare the concentration of CO2 and CH4 on SDS days with the value before and after the SDS. After analysis, we found that SDSs increase the concentration of CO2 and CH4 in the atmosphere. When the SDS occurred, the concentrations of CO2 and CH4 increased and reached peak values on the last or penultimate days of the storm and then decreased to their normal values. Atmospheric flow is the main reason of CO2 concentration increase, the lack of free radicals (OH) during SDSs and the presence of CH4 sources in southeast China are the main reasons of CH4 increase. We also found that in arid and semi-arid areas, SDSs had little effect on the concentration of these two GHGs.

This study uses a multiple linear regression method to composite standard Normalized Difference Vegetation Index (NDVI) time series (1982-2009) consisting of three kinds of satellite NDVI data (AVHRR, SPOT, and MODIS). This dataset was combined with climate data and land cover maps to analyze growing season (June to September) NDVI trends in northeast Asia. In combination with climate zones, NDVI changes that are influenced by climate factors and land cover changes were also evaluated. This study revealed that the vegetation cover in the arid, western regions of northeast Asia is strongly influenced by precipitation, and with increasing precipitation, NDVI values become less influenced by precipitation. Spatial changes in the NDVI as influenced by temperature in this region are less obvious. Land cover dynamics also influence NDVI changes in different climate zones, especially for bare ground, cropland, and grassland. Future research should also incorporate higher-spatial-resolution data as well as other data types (such as greenhouse gas data) to further evaluate the mechanisms through which these factors interact.