Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tDur − the time interval for analysisSkyGap,− the gap fraction for the sky sectorElev − elevation above sea levelGzG,s− surface zenith,azimuth angleWeight,(cos2−=cos1)/Divazizenith angles of the sky sector1,2− the boundingDivazi− the number of azimuthal divisions in the skymapSunGap,− gap fraction for the sunmapUsing equation (1), we calculated the monthly mean ofISWSR at all sites. Figure 2 shows the monthly mean ofISWSR by calculation and by measurement at Terelj GL.Using the data given in Table 1, we obtained the followingregression equation:t −= 2 . 1755 + 0 . 0116 R(2)ξyearlyFrom regression equation (2) the threshold value belowwhich the permafrost occurs is 187.5WM -2 .Mapping Permafrost DistributionWe generated the map of YM of ISWSR. The YM ofISWSR fluctuates from 50.7WM -2 to 409.1WM -2 , dependingon topography and forests. Mountain permafrost distributionwas mapped based on the threshold value of 187.5WM -2 .The permafrost island exists along the small river valleys(valley permafrost) and on the bottom of depression(depression permafrost), where a YM of ISWSR is morethan 187.5WM -2 . From DEM data, we generated the slopemap. From this slope map we have separated the areaswith a slope angle between 0–1°. The area with slope anglebetween 0–1° corresponds to the bottom of depression inNalaikh. This area of Nalaikh was mapped as a depressionpermafrost area (relict permafrost). From the slope map wehave separated the areas with a slope angle between 0–5°.The areas with 0–5° indicate the small river valleys. In theseareas, we have calculated the NDVI and NDWI as follows:NDVINDWINIR − VIS= (4)NIR + VIS(3)NIR − SWIR= (4) (5)NIR + SWIRThe areas with high NDVI and NDWI were mapped aswetland areas. NDVI lies between the limits of -0.4667 and+0.7042. A high value of NDVI is between the limits of +0.30and +0.7042. NDWI lies between the limits of -0.6 and +0.6129.A high value of NDWI is between the limits of 0.0 and +0.6129.The wetland areas overlie the more vegetated areas, and weseparated more wetland areas. These areas correspond with thepermafrost island areas along the small river valleys.The study area divides into two areas: permafrost areasand no permafrost areas. The permafrost areas divide intothree kinds of permafrost: 1 – mountain permafrost, 2 –depression permafrost (relict permafrost), and 3 – valleypermafrost (Fig. 3).Figure 2. Monthly mean of ISWSR at Terelj GL AWS site.Figure 3. Permafrost map of areas surrounding Ulaanbaatar.ConclusionIn summer 2007, we carried out the 1D geophysicalmeasurements by instrument AE-72 on 30 more points andexcavated 10 pits in our study area for validation of thepermafrost distribution. The probability is about 90%.ReferencesEtzelmuller, B. & Hoelzle, M. 2001. Mapping and Modellingthe Occurrence and Distribution of MountainPermafrost. Status Report at First European<strong>Conference</strong> on Permafrost, Roma, Italy, March 2001.Fu, P. & Rich, P.M. 1999–2000. The solar analyst 1.0. UserManual, Helios Environmental Modeling InstituteLLC, USA.Kudryavtsev, V.A. 1978. General Geocryology. Moscow:Moscow University Press, 462 pp.114