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

Characterisation of dust sources in Central Asia using remote sensing

Central Asian deserts are a significant source of dust in the middle latitudes, where economic activity and the health of millions of people are affected by dust storms. Detailed knowledge of sources of dust, controls on their activity, seasonality and atmospheric pathways are of crucial importance but to date, these data are limited. This thesis presents a detailed database ofsources ofdust emissions in Central Asia, from western China to the Caspian Sea, obtained by a multi-scale analysis of the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. The multi-scale approach consists of the following steps: 1) MODIS Deep Blue Aerosol Optical Depth (DB AOD) at 10 km resolution, acquired between 2003 and 2014, is used to investigate the spatiotemporal distribution ofdust hotspots. 2) A dust enhancement algorithm was employed to obtain two composite images (Dust Enhancement Product, DEP) per day at 1 km resolution from MODIS Terra/Aqua acquisitions between 2003 and 2012, from which dust point sources (DPS) were detected by visual analysis of dust plumes and recorded in a database together with meteorological variables at each DPS location derived from the ERA-Interim reanalysis dataset. In all, more than 13500 DPS were identified. Using this multi-scale approach we provided a high resolution inventory of dust sources at sub-basin scale for Central Asia. Our analysis revealed several active source regions, the most active of which are the eastern part ofthe Taklmakan desert. An important finding was an increase in dust activity in the newly-formed desert ofthe Aralkum. Several ofthe identified dust source regions were not previously identified (e.g. sources in northern Afghanistan) or were not widely discussed in literature before (e.g. the Pre-Aral region in western Kazakhstan). Investigation of land surface characteristics and meteorological conditions at each source region revealed mechanisms for the formation of dust sources, including rapid desiccation of water bodies (e.g. Aral Sea), deflation of dust from fluvial sources (e.g. the Upper Amudarya region) and post-fire wind erosion (e.g. Pre-Aral and Lake Balkhash basins). Different seasonal patterns of dust emissions were observed as well as inter-annual trends. Comparison of DB AOD and DPS revealed a noticeable spatial bias in the AOD-based methods for detection of dust sources which is attributed to the fact that the highest atmospheric dust loadings are not always observed over the dust point sources

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

Critical Analysis of Policy Making and Policy Implementation Metaphor: Presenting Alternative Metaphors

An examination of the views of great thinkers such as Bourdieu, Foucault, and Habermas suggest that we live in a language age. Thus, questions of language and power are increasingly raised in politics and the public sphere, but have received less attention. Due to this issue, the purpose of this study is to critically analyze the metaphor of policy-making and policy implementation and provide alternative metaphors for them. To achieve this goal, the method of critical metaphor analysis was used. In this method, metaphor was recognized, interpreted and explained in three steps. The findings show that the metaphor of policy-making and policy implementation is a conventional and fruitful metaphor. Hence, the concepts of "approval", "notification", "order", "implementation", "mission", "report", etc. are derived from the generative metaphor of "policy-making and policy implementation" that affects the cognitive system of actors, and prevents them from acting. The results show that the metaphor of Policy making and Policy implementation indirectly and covertly values actors and persuades them to act. Hence the alternative metaphor of policy development and policy enactment were presented. Policy enactment is a theory that was endorsed in 2012 by Ball et al

A new framework for evaluating dust emission model development using dichotomous satellite observations of dust emission

Dust models are essential for understanding the impact of mineral dust on Earth's systems, human health, and global economies, but dust emission modelling has large uncertainties. Satellite observations of dust emission point sources (DPS) provide a valuable dichotomous inventory of regional dust emissions. We develop a framework for evaluating dust emission model performance using existing DPS data before routine calibration of dust models. To illustrate this framework's utility and arising insights, we evaluated the albedo-based dust emission model (AEM) with its areal (MODIS 500 m) estimates of soil surface wind friction velocity (u(s*)) and common, poorly constrained grain-scale entrainment threshold (u(*ts)) adjusted by a function of soil moisture (H). The AEM simulations are reduced to its frequency of occurrence, P(u(s*) > u(*ts)H). The spatio-temporal variability in observed dust emission frequency is described by the collation of nine existing DPS datasets. Observed dust emission occurs rarely, even in North Africa and the Middle East, where DPS frequency averages 1.8 %, (similar to 7 days y(-1)), indicating extreme, large wind speed events. The AEM coincided with observed dust emission similar to 71.4 %, but simulated dust emission similar to 27.4 % when no dust emission was observed, while dust emission occurrence was over-estimated by up to 2 orders of magnitude. For estimates to match observations, results showed that grain- scale u(*ts) needed restricted sediment supply and compatibility with areal u(s*). Failure to predict dust emission during observed events, was due to u(s*) being too small because reanalysis winds (ERA5-Land) were averaged across 11 km pixels, and inconsistent with u(s*)across 0.5 km pixels representing local maxima. Assumed infinite sediment supply caused the AEM to simulate dust emission whenever P(u(s*)>u(*ts)H), producing false positives when wind speeds were large. The dust emission model scales of existing parameterisations need harmonising and a new parameterisation for u(*ts) is required to restrict sediment supply over space and time

Satellites reveal Earth's seasonally shifting dust emission sources

Establishing mineral dust impacts on Earth's systems requires numerical models of the dust cycle. Differences between dust optical depth (DOD) measurements and modelling the cycle of dust emission, atmospheric transport, and deposition of dust indicate large model uncertainty due partially to unrealistic model assumptions about dust emission frequency. Calibrating dust cycle models to DOD measurements typically in North Africa, are routinely used to reduce dust model magnitude. This calibration forces modelled dust emissions to match atmospheric DOD but may hide the correct magnitude and frequency of dust emission events at source, compensating biases in other modelled processes of the dust cycle. Therefore, it is essential to improve physically based dust emission modules. Here we use a global collation of satellite observations from previous studies of dust emission point source (DPS) dichotomous frequency data. We show that these DPS data have little-to-no relation with MODIS DOD frequency. We calibrate the albedo-based dust emission model using the frequency distribution of those DPS data. The global dust emission uncertainty constrained by DPS data (±3.8 kg m−2 y−1) provides a benchmark for dust emission model development. Our calibrated model results reveal much less global dust emission (29.1 ± 14.9 Tg y−1) than previous estimates, and show seasonally shifting dust emission predominance within and between hemispheres, as opposed to a persistent North African dust emission primacy widely interpreted from DOD measurements. Earth's largest dust emissions, proceed seasonally from East Asian deserts in boreal spring, to Middle Eastern and North African deserts in boreal summer and then Australian shrublands in boreal autumn-winter. This new analysis of dust emissions, from global sources of varying geochemical properties, have far-reaching implications for current and future dust-climate effects. For more reliable coupled representation of dust-climate projections, our findings suggest the need to re-evaluate dust cycle modelling and benefit from the albedo-based parameterisation

The Inylchek Glacier in Kyrgyzstan, Central Asia: Insight on Surface Kinematics from Optical Remote Sensing Imagery

Mountain chains of Central Asia host a large number of glaciated areas that provide critical water supplies to the semi-arid populated foothills and lowlands of this region. Spatio-temporal variations of glacier flows are a key indicator of the impact of climate change on water resources as the glaciers react sensitively to climate. Satellite remote sensing using optical imagery is an efficient method for studying ice-velocity fields on mountain glaciers. In this study, temporal and spatial changes in surface velocity associated with the Inylchek glacier in Kyrgyzstan are investigated. We present a detailed map for the kinematics of the Inylchek glacier obtained by cross-correlation analysis of Landsat images, acquired between 2000 and 2011, and a set of ASTER images covering the time period between 2001 and 2007. Our results indicate a high-velocity region in the elevated part of the glacier, moving up to a rate of about 0.5 m/day. Time series analysis of optical data reveals some annual variations in the mean surface velocity of the Inylchek during 2000–2011. In particular, our findings suggest an opposite trend between periods of the northward glacial flow in Proletarskyi and Zvezdochka glacier, and the rate of westward motion observed for the main stream of the Inylchek

A new framework for evaluating dust emission model development using dichotomous satellite observations of dust emission

Dust models are essential for understanding the impact of mineral dust on Earth’s systems, human health, and global economies, but dust emission modelling has large uncertainties. Satellite observations of dust emission point sources (DPS) provide a valuable dichotomous inventory of regional dust emissions. We develop a framework for evaluating dust emission model performance using existing DPS data before routine calibration of dust models. To illustrate this framework’s utility and arising insights, we evaluated the albedo-based dust emission model (AEM) with its areal (MODIS 500 m) estimates of soil surface wind friction velocity (us*) and common, poorly constrained grain-scale entrainment threshold (u*ts) adjusted by a function of soil moisture (H). The AEM simulations are reduced to its frequency of occurrence, P(us* > u*tsH). The spatio-temporal variability in observed dust emission frequency is described by the collation of nine existing DPS datasets. Observed dust emission occurs rarely, even in North Africa and the Middle East, where DPS frequency averages 1.8 %, (~7 days y− 1), indicating extreme, large wind speed events. The AEM coincided with observed dust emission ~71.4 %, but simulated dust emission ~27.4 % when no dust emission was observed, while dust emission occurrence was over-estimated by up to 2 orders of magnitude. For estimates to match observations, results showed that grain-scale u*ts needed restricted sediment supply and compatibility with areal us*. Failure to predict dust emission during observed events, was due to us* being too small because reanalysis winds (ERA5-Land) were averaged across 11 km pixels, and inconsistent with us* across 0.5 km pixels representing local maxima. Assumed infinite sediment supply caused the AEM to simulate dust emission whenever P(us*>u*tsH), producing false positives when wind speeds were large. The dust emission model scales of existing parameterisations need harmonising and a new parameterisation for u*ts is required to restrict sediment supply over space and time.</p

The Inylchek Glacier in Kyrgyzstan, Central Asia: Insight on Surface Kinematics from Optical Remote Sensing Imagery

Mountain chains of Central Asia host a large number of glaciated areas that provide critical water supplies to the semi-arid populated foothills and lowlands of this region. Spatio-temporal variations of glacier flows are a key indicator of the impact of climate change on water resources as the glaciers react sensitively to climate. Satellite remote sensing using optical imagery is an efficient method for studying ice-velocity fields on mountain glaciers. In this study, temporal and spatial changes in surface velocity associated with the Inylchek glacier in Kyrgyzstan are investigated. We present a detailed map for the kinematics of the Inylchek glacier obtained by cross-correlation analysis of Landsat images, acquired between 2000 and 2011, and a set of ASTER images covering the time period between 2001 and 2007. Our results indicate a high-velocity region in the elevated part of the glacier, moving up to a rate of about 0.5 m/day. Time series analysis of optical data reveals some annual variations in the mean surface velocity of the Inylchek during 2000–2011. In particular, our findings suggest an opposite trend between periods of the northward glacial flow in Proletarskyi and Zvezdochka glacier, and the rate of westward motion observed for the main stream of the Inylchek