samad khosravi yeganeh; mostafa karampour; Behrouz Nasiri
Abstract
In the coming years, drought is one of the potential threats to low rainfall countries, especially Iran. Iran has always faced big and small droughts. The geographical location and natural conditions of the country are such that severe and weak droughts have occurred in it. Evaluating the effects of ...
Read More
In the coming years, drought is one of the potential threats to low rainfall countries, especially Iran. Iran has always faced big and small droughts. The geographical location and natural conditions of the country are such that severe and weak droughts have occurred in it. Evaluating the effects of drought on vegetation is very important. In order to reduce damages and consequences caused by drought, drought monitoring using remote sensing method is considered in most countries because of its advantages. In this study, in order to reveal the effects of precipitation on vegetation in Iran, the precipitation data of 143 synoptic meteorological stations of the country were used to calculate the monthly average of the Standard Precipitation Index (SPI) in the period 2000-2021. Then, using visible infrared images (VIIRS) as a weekly average in the period of 2013-2021 (April 1st to the end of July every year) obtained from the Suomi NPP sensor, the drought condition of the vegetation was investigated. Based on the obtained results, it can be said that the vegetation cover in 2015 and 2021 was more affected by drought than the other investigated years. The most severe vegetation drought occurred in 2021. In 2016, 2019 and 2020, vegetation was in more favorable conditions. The correlation of SPI with NDVI, VCI, TCI and VHI was calculated as 0.1906, 0.038, 0.016 and 0.002 respectively.
mostafa karampour; samad khosravi yegane; hamed heidri
Abstract
IntroductionIn each region, drought conditions vary from moderate to severe and with different durations, which require continuous and operational monitoring. The longer a drought occurs, the greater its effects on vegetation and water resources, and the more severe the drought, which can limit human ...
Read More
IntroductionIn each region, drought conditions vary from moderate to severe and with different durations, which require continuous and operational monitoring. The longer a drought occurs, the greater its effects on vegetation and water resources, and the more severe the drought, which can limit human services and alter natural systems. The effects of drought include habitat destruction for wildlife and water quality, reduced access to water resources, etc. and as a result, disruptions such as fire incidents and other natural disasters increase. ). Vegetation in each region, especially in different regions of Lorestan province, is at risk of numerous fires every year due to the lack of rain and dryness of the environment. For this reason, the issue of revealing and identifying fire-prone areas in relation to the most important climatic element (rainfall) has been selected and carried out, which can facilitate appropriate and preventive measures to protect vegetation areas. In this research, a combined method has been used.Material and methods:In this study, an attempt has been made to investigate the drought condition of vegetation in Lorestan province by using Suomi NPP infrared images using NDVI, VCI and TCI indices. The studied period of 2013-2021 corresponds to the first of April to the end of July (week of 13-26 AD) as a weekly average. The monthly average of Standard Precipitation Index (SPI) using precipitation data, the use of monthly precipitation data from Aligoderz, Durood, Khorramabad, Borujerd, Noorabad, Kohdasht and Azna weather stations was done to analyze the precipitation situation well and separate dry and wet months from each other. become Then the correlation coefficient of SPI index with each vegetation index (NDVI, VCI and TCI) is calculated.Results and discussion:Based on the rainfall data recorded in the meteorological stations of Lorestan province, it can be said that there is no rainfall in the study area in the summer season (July, August and September) and only in the autumn, winter and spring seasons. Therefore, the water year in Lorestan province starts approximately from the third decade of September and continues until the second and third decade of June every year. This indicates the very dry air and lack of humidity. Dry air or lack of humidity and increase in temperature provide the necessary conditions for causing fire in the province. In this article, they put a dry season in the summer season of Lorestan province and August is the driest month of the year.ConclusionThe results of this research showed that the vegetation in Lorestan province is always facing the risk of fire and this is very high in the years when there is a lack of rainfall, in different months. It was proved that if there is a lack of rainfall in the first months of the water year, there is a risk of vegetation fire even in the cold months of the year, and this risk increases significantly in the hot months of the year, which is the case in 2021. there have been. SPI calculations showed that the months of July, August and September are negative in Lorestan province. The results show that the best indicator is based on satellite images for monitoring vegetation drought and fire risk in the study area (TCI). In the years 2013 and 2015, the highest fire risk occurred in the western and central regions of Lorestan province. In 2021, the most severe fire risk has occurred in vegetation in the studied area. Due to the large changes and dispersion of vegetation indicators effective in the occurrence of fires in terms of time and place, Spearman's non-parametric correlation has been used.Keywords: Vegetation fire, drought , precipitation, infrared images, Lorestan province
