Satellite monitoring of vegetation in arctic zone of Yakutia

  1. Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Division of Russian Academy of Sciences

Model calculations and observations show that highest effects of climate change occur in high northern
latitudes. These observations of soil temperature at meteorological stations in the second half of XX century
indicate an increase in depth of seasonal thawing and decrease of depth of seasonal freezing of permafrost. As
a result of thaw of permafrost, which is the largest reservoir of greenhouse gases, huge amount of greenhouse
gases will be injected into the atmosphere. Changes in concentration of greenhouse gases and aerosols in the
atmosphere, changes in solar radiation and vegetation differ energy balance of climate system and impulse
climate change.
The report presents preliminary results of studies of changes in vegetation index in arctic zone of Yakutia.
A long series of AVHRR radiometer data were used, these data were obtained at SKANOR station(IKFIA SB
RAS, Yakutsk) from NOAA satellites during 1998-2009. According to the first and second spectral channels of
AVHRR vegetation index NDVI was calculated; it indicates the degree of vegetation conditions. Four test sites
with size 30x30 km (three sites in the north-east and one in the central part of Yakutia) were selected, for
which NDVI during the growing season May-September was calculated. As a result of AVHRR data processing
ten-day, seasonal and annual average values of NDVI and cloudiness in the north-east of Yakutia were received.
In addition to AVHRR measurements Rosgidromet data were obtained to assess temperature and humidity at
test sites.
During the observation period 1998-2009 a weak but steady upward trend in humidity and temperature was
observed. At the same time an overall decrease in NDVI in the north-eastern and central parts of Yakutia was
observed. Particularly noticeable declination in NDVI was observed in 2001-2005. This declination coincided
with a phase of decrease in solar activity in the 23rd cycle.
This work was supported by RAS Program №16/3.