Ninth International Conference on Permafrost ... - IARC Research

Mapping the Mountain Permafrost in Areas Surrounding Ulaanbaatar CityYa Jambaljav, A. Dashtseren, D. Battogtokh, D. DorjgotovInstitute of Geography, Mongolian Academy of Sciences, Ulaanbaatar, MongoliaY. Iijima, M. Ishikawa, Y. Zhang, T. Kadota, T. OhataInstitute of Observational Research for Global Change, JAMSTEC, Yokosuka, JapanIntroductionAccording to the geographical location and to theclimatic condition of Mongolia, the dominating parametersfor permafrost occurrence are incoming shortwave solarradiation (ISWSR) and ground moisture. Using thresholdvalues, we have generated a permafrost distribution map inareas surrounding Ulaanbaatar city.Study areaThere are three observation sites in our study area: (1)Terelj forest site (Terelj FA) is characterized by northfacingforested slope; (2) Terelj grassland site (Terelj GL)is characterized by south-facing sparse grassed gentle slope;and (3) Nalaikh site is characterized by sparsely grassedplate area with smooth hillocks.Data usedWe used the following data: (1) ISWSR at the Nalaikhautomatic weather station (Nalaikh AWS), at Terelj GLAWS), and at Terelj FA AWS (Fig. 1). (2) Mean annual groundtemperature (MAGT) on the bottom of seasonal freezing andthawing (BSFT) at the above sites and at Sanjai of the SelbeRiver basin (Table 1). In 5 boreholes, temperatures weremeasured by CR-10X dataloggers, data marks, and HOBOFigure 1. MM of SWSR at Terelj GL AWS, at Terelj FA AWS, andat Nalaikh AWS site.Table 1. MAGT on BSFT, depth of SFT, and YM of ISWSR.MAGT onBSFT, *CDepth ofSFT, mYM of ISWSR,WM -2Name of sites1 Terelj GL +1.9 4.0 349.32 Terelj FA -1.4 3.5 67.173 Nalaikh -0.14 5.0 330.234 Nalaikh pingo -2.2 1.45 327.67*5 Sanjai +1.75 3.2 346.9** these data from calculation resultsdataloggers. (3) DEM data from SRTM. (4) Landsat 7ETMimage from August 1, 2001, of 131 path and 027 row. Weused the temperature data measured by a HOBO dataloggerin a borehole located in Sanjai of the Selbe River valley andthe temperature data measured by a HOBO datalogger in aborehole located on top of small pingo near Nalaikh AWS.Table 1 shows the MAGT on BSFT, the depth of seasonalfreezing and thawing (SFT), and the yearly mean (YM) ofISWSRModeling the Permafrost OccurrenceOne of more important criteria of permafrost occurrenceor absence is the MAGT at the BSFT. According toKudryavtsev (1978), the MAGT at the BSFT is the functionof multiparameters. Where the MAGT at the BSFT is lowerof the zero, permafrost occurs. In contrast, permafrost isabsent. It is the main criterion of our model. We calculatedthe monthly mean of ISWSR at selected sites as the followingequations (Fu & Rich 2002):where:+∑∑R dif ,R income = R dir , αθ αθ )()((1)where:R( dir , αθ ) = S Const * τθ )(m* SunDur , αθ* SunGap , αθ * cos( AngIn , αθ )R( dif , αθ ) = R glb * Pdif* Dur * SkyGap , αθ* Weight , αθ * cos( AngIn , αθ )m( θ ) EXP ( −=0.000118 *Elev − 1.638 * 10AngIn , αθ = arccos[cos ( θ )* cos( G+ sin( θ )* sin( G )* cos( α − G )]Rglb - solar - solarflux that= ( SConstis diffused−9z∑zenith angleazimuth angle* Elev( τ2the atmosphere) / cos( θ )aθ )(m)) /( 1 − Pdif− solar constant (1367WM-2)SConst − transmitiv ity ofSunDur,− time durationby sky sectorPdif− the proportion of global normal radiationz))113