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Permafrost plays an important role in numerous environmental processes at high latitudes and in high mountain areas. The identification of mountain permafrost, particularly in the discontinuous permafrost regions, is challenging due to limited data availability and the high spatial variability of controlling factors. This study focuses on mountain permafrost in a data-scarce environment of northern Mongolia, at the interface between the boreal forest and the dry steppe mid-latitudes. In this region, the ground temperature has been increasing continuously since 2011 and has a high spatial variability due to the distribution of incoming solar radiation, as well as seasonal snow and vegetation cover. We analyzed the effect of these controlling factors to understand the climate--permafrost relationship based on in situ observations. Furthermore, mean ground surface temperature (MGST) was calculated at 30-m resolution to predict permafrost distribution. The calculated MGST, with a root mean square error of ±1.4°C, shows permafrost occurrence on north-facing slopes and at higher elevations and absence on south-facing slopes. Borehole temperature data indicate a serious wildfire-induced permafrost degradation in the region; therefore, special attention should be paid to further investigations on ecosystem resilience and climate change mitigation in this region. [ABSTRACT FROM AUTHOR]

Net radiation is a key component of surface radiation balance and has a strong influence on hydrological processes via evapotranspiration. In this study, daily average net radiation (Rnmean) for all-sky conditions was investigated as a function of the estimated daily average global radiation (GRmean) during the summers of 2011 and 2012 (128 days total) in the Sugnugur Valley of Northern Mongolia. We present a simple alternative remote sensing approach that considers factors such as topography, cloud fraction, cloud optical thickness and surface albedo. First, a geometric model for the simulation of daily average global radiation (GRCS:mean) for clear-sky conditions was applied on a daily basis. It considers topographical effects, such as slope, azimuth and elevation. GRmean was then derived for all-sky conditions by coupling the averaged atmospheric products of MODIS. Finally, Rnmean was obtained as a function of the simulated GRmean using the linear regression parameters found at a permanent observation site. The results were validated with the data from a nearby temporary observation site. The root mean square errors (RMSE) were 44 and 52 Wm−2 for GRmean and 18 and 25 Wm−2 for Rnmean at the two different sites. This methodology requires few observations and offers a simple means for estimating GRmean with high spatial (30 m) and temporal (daily) resolution under any sky conditions in the absence of ground measurements. Furthermore, Rnmean can be modeled from the simulated GRmean at regional or watershed scales where ground observations exist at one site at least. [ABSTRACT FROM AUTHOR]

Mongolia is not only a water-scarce but also a data-scarce country with regard to environmental information. At the same time, regional effects of global climate change, major land use changes, a booming mining sector, and growing cities with insufficient and decaying water and wastewater infrastructures result in an increasingly unsustainable exploitation and contamination of ground and surface water resources putting at risk both aquatic ecosystems and human health. For the mesoscale (≈15,000 km²) model region of the Kharaa River Basin (KRB), we investigated (1) the current state of aquatic ecosystems, water availability and quality; (2) past and expected future trends in these fields and their drivers; (3) water governance structures and their recent reforms; and (4) technical and non-technical interventions as potential components of an integrated water resources management (IWRM). By now, the KRB is recognized as one of the most intensively studied river basins of the country, and considered a model region for science-based water resources management by the Mongolian government which recently adopted the IWRM concept in its National Water Program. Based on the scientific results and practical experiences from a six-year project in the KRB, the potentials and limitations of IWRM implementation under the conditions of data-scarcity are discussed. [ABSTRACT FROM AUTHOR]

The headwaters of mountainous, discontinuous permafrost regions in north-eastern Mongolia are important water resources for the semi-arid country, but little is known about hydrological processes there. Run-off generation on south-facing slopes, which are devoid of permafrost, has so far been neglected and is totally unknown for areas that have been affected by recent forest fires. To fill this knowledge gap, the present study applied artificial tracers on a steppe-vegetated south-facing and on two north-facing slopes, burned and unburned. Combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone. On the unburned north-facing slope, rapid and widespread infiltration through a wet organic layer was observed down to the permafrost. On the burned profile, rapid infiltration occurred through a combusted organic and underlying mineral layer. Stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow (SSF). Ongoing SSF could directly be studied 24 h after a high-intensity rainfall event on a 55-m hillslope section in the burned forest. Measurements of water temperature proved the role of the permafrost layer as a base horizon for SSF. Repeated tracer injections allowed direct insights into SSF dynamics: A first injection suggested rather slow dispersive subsurface flow paths; whereas 18 h later, a second injection traced a more preferential flow system with 20 times quicker flow velocities. We speculate that these pronounced SSF dynamics are limited to burned slopes where a thermally insulating organic layer is absent. On three south-facing soil profiles, the applied tracer remained in the uppermost 5 cm of a silt-rich mineral soil horizon. No signs of preferential infiltration could be found, which suggested reduced biological activity under a harsh, dry and cold climate. Instead, direct observations, distributed tracers and charcoal samples provided evidence for the occurrence of overland flow. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The semi-arid forest-steppe ecotone in the Khentii Mountains in Northern Mongolia is characterized by southerly exposed steppe slopes, shrublands in the floodplain of river valleys and northerly exposed taiga slopes. Here, the freshwater for the downstreaming agricultural, rural and mining sectors is generated. To gain insight into the main water-generating sources in mountainous river basins, we studied the actual evapotranspiration (ET) and its main influencing eco-hydrometeorological parameters at a steppe and a shrubland site during the growing season 2012. Latent ( LE) and sensible ( H) heat fluxes were measured using the Bowen ratio energy balance method, and the surface soil heat flux ( G) was determined with the PlateCal and GradCal approach. During water-stressed soil conditions at the steppe site, volumetric water content (VWC) values of 0.05 m m (−10 cm) resulted in significant limitations of the mean actual ET rates to 0.4 mm day. In contrast, high VWC with maxima of >0.4 m m and high mean actual ET rates >6.0 mm day were observed during water-unstressed soil conditions. As precipitation and change of stored soil moisture were approximately equal to actual ET, the contribution of freshwater from mountainous steppe within the forest-steppe ecotone can be neglected. At the shrubland site, which is underlain by a shallow aquifer system, VWC remained relatively constant with mean values of 0.4 m m (−10 cm). A multiple regression analysis indicated that actual ET, with mean rates of 2.3 mm day, was not significantly limited by precipitation and VWC, but by net radiation ( R) and air temperature. As precipitation exceeded total actual ET, shrub covered river floodplains can contribute to freshwater generation. [ABSTRACT FROM AUTHOR]

High topographic heterogeneity and complex mechanisms between the atmosphere and the ground create unique hydro-climatic processes over mountainous regions. Based on in situ observations, we present the spatial variability of ground surface temperature (GST) in the Khentii Mountains of northern Mongolia, which is situated at the southern fringe of the Eurasian permafrost zone. Changes in the hydrothermal regime of the active layer were investigated in association with changing climate and wildfire effects. The results reveal that the GST tends to increase continuously since 2011 in both thawing and freezing seasons, and varies significantly within a short horizontal distance, particularly during the thawing season. Extreme weather events, such as drought and heavy snowfall, amplify the increase in the ground temperature and deepen the seasonal thawing depth. The fire-induced loss in organic layer resulted in a greater heat penetration deeper into the ground and unbalanced the moisture distribution. Overall, the thawing depth is greater by >1.7 m under severely burned forest, compared to unburned forest. Given that about 30% of the boreal forest was affected by wildfire in the study area, the ground thermal regime changed considerably. The findings suggest that the combination of regional temperature rise and more frequent extreme weather and wildfire events in the region triggers permafrost degradation and alters the hydrothermal regime in the future. [ABSTRACT FROM AUTHOR]

Livestock production is a socioeconomic linchpin in Mongolia and is affected by large-scale livestock die-offs. Colloquially known as dzuds, these die-offs are driven by anomalous climatic events, including extreme cold temperatures, extended snow cover duration (SCD) and drought. As average temperatures across Mongolia have increased at roughly twice the global rate, we hypothesized that increasing cold season surface melt including soil freeze/thaw (FT), snowmelt, and icing events associated with regional warming have become increasingly important drivers of dzud events as they can reduce pasture productivity and inhibit access to grazing. Here, we use daily brightness temperature (Tb) observations to identify anomalous surface melt and icing events across Mongolia from 2003–2016 and their contribution to dzuds relative to other climatic drivers, including winter temperatures, SCD, and drought. We find a positive relationship between surface melt and icing events and livestock mortality during the fall in southern Mongolia and during the spring in the central and western regions. Further, anomalous seasonal surface melt and icing events explain 17–34% of the total variance in annual livestock mortality, with cold temperatures as the leading contributor of dzuds (20–37%). Summer drought showed the greatest explanatory power (43%) but overall had less statistically significant relationships relative to winter temperatures. Our results indicate that surface melt and icing events will become an increasingly important driver of dzuds as annual temperatures and livestock populations are projected to increase in Mongolia. [ABSTRACT FROM AUTHOR]

Knowledge of the snow cover dynamics in mountains of the semi-arid regions on Earth is essential for an improved understanding of the hydrological regime and for human water supply in a water scarce environment. In the semi-arid Sugnugur headwater catchment (in the Khentii Mountains, northern Mongolia), a spatial analysis of seasonal snow cover duration (SCD) was achieved on a 30 m grid by integrating the spatial resolution of Landsat-7, Landsat-8 and Sentinel-2A images with the daily temporal resolution of MODIS snow products (2000-2017). Validation was achieved using in situ measurements from winter field campaigns and spatially distributed surface temperature recordings. We found a mean increase of SCD with altitude at approximately +6 days/100m. However, no altitude-dependent changes in snow depth could be observed during the field campaigns. The southern exposed valley slopes are either snow free or covered by intermittent snow throughout the winter months due to high sublimation rates and prevailing wind. The estimated mean SCD ranges from 124 in the lower parts of the catchment to 226 days on the mountain peaks, with a mean underestimation of 12-13 days. Snow onset and melt dates exhibited large inter-annual variability, but no significant trend in the seasonal SCD was evident. Our method supports the better quantification of snow melt rates and thus water availability in this semi-arid environment. It can be applied to high-resolution snow mapping in similar mountainous regions. [ABSTRACT FROM AUTHOR]