New inventory of dust sources in Central Asia derived from the daily MODIS imagery

This paper presents the first inventory of dust emission sources in Central Asia and western China (35-50°N, 50-100°E) derived from the twice daily MODIS imagery from 2003-2012. The high-resolution (1 km) dust enhancement product was generated and used to produce maps of dust point sources and gridded data sets of dust emission frequencies. The most active dust emissions were observed in the eastern part of the Tarim basin (Lop Nur salt lake) followed by the Aralkum. A high frequency of dust emissions was recorded in the regions which were not reported in literature to date: the upper Amudarya region in northern Afghanistan and the Pre-Aral region (from the Ustyurt Plateau to the Betpak Dala desert). Dust emissions were associated mainly with the fluvial features (dry river beds and lakes), agricultural activities and fire damage to vegetation. In the eastern and northern parts of the study region and in the Aralkum, dust emissions peaked in spring while in the western and southern parts, they peaked in summer. The Aralkum exhibited a consistent growth in the frequency and intensity of dust emissions and similar but weaker trends were observed in the Karakum and Kyzylkum

Using the significant dust deposition event on the glaciers of Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and provenancing of desert dust events recorded in snow pack.

A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution provenancing of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm and the dominant mode of 0.60 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite and oxides of aluminium, manganese, and magnesium. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the provenancing of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives

An assessment of SEVIRI imagery at various temporal resolutions and the effect on accurate dust emission mapping

This paper evaluates the use of the ‘Dust red/green/blue (RGB)’ product derived from Spinning Enhanced Visible and Infrared Imager (SEVIRI) data at 15-min, 30-min, and 60-min temporal resolutions, for monitoring dust emissions in the Middle East. From January 2006 to December 2006, observations of dust emission point sources were recorded at each temporal resolution across the Middle East. Previous work has demonstrated that using SEVIRI data is a major improvement on other remote sensing methods for mapping dust sources in the Sahara, by enabling dust-storm observations through sequential images, back to the point of first emission. However, the highest temporal resolution available (15-min observations) produces 96 images per day, resulting in significantly higher data management requirements than data provided at 30-min and 60-min intervals. To optimize future research workflows, this paper investigates the effect of lowering the temporal resolution on the number and spatial distribution of observed dust emission events in the Middle East. The results show that the number of events observed reduced by 17% for 30-min resolution and 50% for 60-min resolution. These differences change seasonally, with the highest reduction observed in summer (34% and 64% reduction, respectively)

New inventory of dust emission sources in Central Asia and Northwestern China derived from MODIS imagery using dust enhancement technique

The first inventory of dust emission sources in Central Asia and northwestern China (35–50°N, 50–100°E) derived from the twice daily MODIS imagery from 2003 to 2012 is presented. A high‐resolution (1 km) dust enhancement product was generated to produce maps of dust point sources (DPS), indicating geographical locations of the observed dust emissions, and gridded data sets of dust emission frequencies. About 13,500 DPS were detected over an area of ∼5 × 106 km2, however, their distribution was uneven. The highest frequency of DPS occurred in the northern and eastern Taklimakan, in the Aralkum, and in the regions, which were not widely reported in literature before, the Balkh delta in northern Afghanistan and the pre‐Aral, from the northern Caspian coast to the Betpak‐Dala desert in Kazakhstan. South of the Aral, DPS were mainly associated with fluvial features: drying lakes, dry river beds, alluvial deposits and agricultural activity which is closely linked to water availability in this arid region. In the pre‐Aral and Balkhash‐Junggar regions, land damaged by wildfire was the main source of dust. In China and eastern Kazakhstan dust emissions peaked in spring; in Central Asia and western Kazakhstan—in summer. The Aralkum was active throughout the year with a positive trend in emission frequency over the study period. Locations of DPS did not always correlate with high atmospheric optical depth (AOD) particularly west of the Aral and in the southern Taklimakan where few DPS were detected despite the high AOD values. This was attributed to dust transport from the upwind sources

Optical, geochemical and mineralogical characteristics of light-absorbing impurities deposited on Djankuat Glacier in the Caucasus mountains

Supra-glacial material, including light-absorbing impurities (LAI) such as mineral dust of crustal and soil origin, black carbon, algae and cryoconite, reduce the reflectance of snow and glacier ice. The reduction depends on the amount of LAI and their physical and chemical properties, which vary spatially and temporally. Spectral reflectance data and snow and ice samples, containing LAI, were collected in the ablation zone of the Djankuat Glacier, Central Caucasus, Russia. The spectra of the samples containing mineral dust transported from deserts were characterized by negative visible near-infrared gradients and were different from the spectra of clean aged snow and exposed glacier ice and from the samples containing mineral dust produced locally. Geochemical and mineralogical analysis using X-ray diffraction and X-ray fluorescence spectrometry showed that samples containing desert dust were characterised by a high proportion of clay materials and such minerals as smectites, illite–smectites and palygorskite and by a smaller size of mineral particles. They were enriched in chromium, zinc and vanadium. The latter served as an indicator of dust transport over or origin from the oil-producing regions of the Middle East. There was a strong negative correlation between the amount of organic matter and mineral dust in the collected samples and the albedo of surfaces from which the samples were collected. The results suggested that organic matter reduced albedo more efficiently than mineral dust. The study highlighted the importance of supra-glacial material in changing the surface reflectivity of snow and glaciers in the Caucasus region

Coverage of in situ climatological observations in the world's mountains

Many mountainous environments and ecosystems around the world are responding rapidly to ongoing climate change. Long-term climatological time-series from such regions are crucial for developing improving understanding of the mechanisms driving such changes and ultimately delivering more reliable future impact projections to environmental managers and other decision makers. Whilst it is already established that high elevation regions tend to be comparatively under-sampled, detailed spatial and other patterns in the coverage of mountain climatological data have not yet been comprehensively assessed on a global basis. To begin to address this deficiency, we analyse the coverage of mountainous records from the Global Historical Climatological Network-Daily (GHCNd) inventory with respect to space, time, and elevation. Three key climate-related variables—air temperature, precipitation, and snow depth—are considered across 292 named mountain ranges. Several additional datasets are also introduced to characterize data coverage relative to topographic, hydrological, and socio-economic factors. Spatial mountain data coverage is found to be highly uneven, with station densities in several “Water Tower Units” that were previously identified as having great hydrological importance to society being especially low. Several mountainous regions whose elevational distribution is severely undersampled by GHCNd stations are identified, and mountain station density is shown to be only weakly related to the human population or economic output of the corresponding downstream catchments. Finally, we demonstrate the capabilities of a script (which is provided in the Supplementary Material) to produce detailed assessments of individual records' temporal coverage and measurement quality information. Overall, our contribution should help international authorities and regional stakeholders identify areas, variables, and other monitoring-related considerations that should be prioritized for infrastructure and capacity investment. Finally, the transparent and reproducible approach taken will enable the analysis to be rapidly repeated for subsequent versions of GHCNd, and could act as a basis for similar analyses using other spatial reporting boundaries and/or environmental monitoring station networks

Impacts of climate change on river discharge in the northern Tien Shan: Results from long-term observations and modelling

This paper presents preliminary results of investigation of the observed and projected changes in discharge of the snow- and glacier-nourished rivers of the Balkhash-Alakol basin, Kazakhstan using the long-term homogeneous records and climate projections from an ensemble of climate simulations. Positive trends in discharge were registered at most sites between the 1950s and 2010s. An increase in discharge was observed at all sites between May and October in 2000 – 2013 in comparison with the previous decades which was particularly strong in July-August at the rivers with a high proportion of glacierized area. This positive trend in discharge appears to be driven primarily by an increase in temperature. Results for four climate scenarios with spatial resolution of 25 km are presented. These scenarios were generated using regional climate model PRECIS driven by HadGEM GCM for RCP 2.6 and RCP 8.5 scenarios, HadCM3Q0 and ECHAM5 GCM for A1B scenario. While all climate experiments project increase in temperature, precipitation projections vary between models, seasons and spatially. HBV-ETH model was used to simulate the observed and future discharge for the Ulken and Kishi Almatinka rivers using climate projections from PRECIS-HadCM3Q0 simulation for A1B scenario. The results show that peak flow has already been reached at both rivers and is likely to continue for the next 10-15 years. A small decrease of 7-10% in annual discharge is projected for the Ulken and Kishi Almatinka for the 2025-2044 period increasing thereafter and the projected decline in discharge is more significant in summer

Chapter 8 The Status and Role of the alpine Cryosphere in Central Asia

The alpine cryosphere including snow, glaciers and permafrost are critical to water management in the Aral Sea Basin (ASB) and larger Central Asia (CA) under changing climate: as they store large amounts of water in its solid forms. Most cryospheric components in the Aral Sea Basin are close to melting point, and hence very vulnerable to a slight increase in air temperature with significant consequences to long-term water availability and to water resources variability and extremes. Current knowledge about different components of cryosphere and their connection to climate in the Basin and in the entire Central Asia, varies. While it is advanced in the topics of snow and glaciers, knowledge on permafrost it rather limited. Observed trends in runoff point in the direction of increasing water availability in July and August at least until mid-century and increasing possibility for water storage in reservoirs and aquifers. However, eventually this will change as glaciers waste away. Future runoff may change considerably after mid-century and start to decline if not compensated by increasing precipitation. Cryosphere monitoring systems are the basis for sound estimates of water availability and water-related hazards associated with snow, glaciers and permafrost. They require a well-distributed observational network for all cryospheric variables. Such systems need to be re-established in the Basin after the breakup of the Soviet Union in the early 1990s. This process is slowly emerging in the region. Collaboration between local operational hydro-meteorological services and academic sector, and with international research networks may improving the observing capabilities in high mountain regions of CA Asia in general and the ASB specifically