Climate In Central Asia Research Articles

Latitudinal gradients in the phylogenetic assembly of angiosperms in Asia during the Holocene

Spatio-temporal assessment of phylogenetic diversity gradients during the Holocene (past 12,000 years) provides an opportunity for a deeper understanding of the dynamics of species co-occurrence patterns under environmental fluctuations. Using two robust metrics of phylogenetic dispersion (PD) and 99 fossil pollen sequences containing 6557 samples/assemblages, we analyse spatio-temporal variation in PD of angiosperms and its relationship with Holocene climate in central Asia. Overall, PD throughout the Holocene decreases linearly with increasing latitude, except for a rise in mean nearest taxon distance from ca. 25 to 35° N. This indicates that phylogenetically divergent taxa decrease progressively with increasing latitude, leaving more phylogenetically closely related taxa in the assemblages, thereby increasing phylogenetic relatedness among the co-occurring taxa. The latitudinal gradient of PD has not been consistent during the Holocene, and this temporal variation is concordant with the Holocene climate dynamics. In general, profound temporal changes in the latitudinal PD toward higher latitudes implies that the major environmental changes during the Holocene have driven considerable spatio-temporal changes in the phylogenetic assembly of high-latitude angiosperm assemblages. Our results suggest that environmental filtering and the tendency of taxa and lineages to retain ancestral ecological features and geographic distributions (phylogenetic niche conservatism) are the main mechanisms underlying the phylogenetic assembly of angiosperms along the climate-latitudinal gradient. Ongoing environmental changes may pose future profound phylogenetic changes in high-latitude plant assemblages, which are adapted to harsh environmental conditions, and therefore are phylogenetically less dispersed (more conservative or clustered).

River inverse modeling of the late Cenozoic uplift history of the Pamir-Tian Shan orogens: Implications for aridification of Central Asia

The uplift history of the Pamir-Tian Shan orogens remains debated, and is crucial to understanding the aridification of Central Asia. To address this question, we performed inverse modeling of the westward-flowing Vakhsh River along the Alai Valley between the Pamir and Tian Shan orogens. We validated the application of this method in reconstructing uplift history of mountains with complex climatic and tectonic settings. The modeled results reveal three episodes of accelerated uplift of the Vakhsh River drainage at ca. 10–7 Ma, ca. 5 Ma, and 2–0 Ma. The late Miocene rapid uplift at rates of 0.6–0.8 mm/yr of the Vakhsh River drainage occurred at ca. 10–7 Ma. Rock uplift, coeval with compressional deformation and exhumation around the Alai Valley, was likely driven by crustal shortening during the Pamir-Tian Shan convergence. Narrowing of the Alai Valley started to impact westerly atmospheric flow, leading to incipient rain shadow responsible for emergence of desert in the proximal leeward Tarim Basin. Accelerated uplift at ca. 5 Ma and 2–0 Ma at rates of 1.0–1.4 mm/yr and 1.7–2.3 mm/yr, increased surface elevations to near modern heights (3.5–5 km) that largely blocked the westerlies, causing enhanced aridification in the Tarim Basin. Our modeling results highlight the important role of mountain building in shaping late Cenozoic climate in Central Asia.

Linking source and sink: The timing of deposition of Paleogene syntectonic strata in Central Asia

Abstract Determining the age of siliciclastic continental sequences in the absence of comprehensive biostratigraphy or radiometric dating of geological markers (e.g., volcanic layers) is inherently challenging. This issue is well exemplified in the current debate on the age of Cenozoic terrestrial strata in Central Asia, where competing age models constrained by non-unique paleomagnetic correlations are interpreted to reflect the growth of the Tibetan Plateau and its impact on Central Asian climate change. Here we present a new approach to evaluate competing age models by comparing the onset of rapid basement exhumation constrained by low-temperature thermochronology in the sediment source region with the initiation of growth strata in the adjacent sedimentary sink. We first validate this method in regions with well-constrained age models and subsequently apply this approach to the Tarim and Qaidam Basins in the northern Tibetan Plateau. The results of this analysis show that syntectonic sedimentation had already initiated during the Paleocene–Eocene and was followed by intensified Oligocene–Miocene mountain building along the northern margin of the plateau. Based on this refined Paleogene tectonic history, we further arrive at a temporal correlation between Paleogene tectonism in Northern Tibet and the retreat of the Proto-Paratethys Sea, a major water body that extended across Eurasia and was closely associated with climatic and biodiversity changes. We thus highlight the previously underestimated role tectonics in Northern Tibet had in the evolution and demise of the Proto-Paratethys Sea during the Paleogene.

The Sangonghe biota in the Junggar Basin, NW China: age constraints and climate implications

ABSTRACT A distinct coal break occurs widely in the late Early Jurassic in Central Asia, the cause of which, however, is still debated largely due to the uncertainty of its age constraint. In the Junggar Basin of northwestern China, this coal break coincides with the Sangonghe Formation, which is well exposed along the basin margins, and is mainly composed of lacustrine deposits rich in a variety of fossils, including plants, pollens and spores, bivalves, clam shrimps, insects and some vertebrates. Here we name them as the Sangonghe biota and review their biostratigraphic framework. The Sangonghe biota constrains the Sangonghe Formation to the late Pliensbachian to the early Aalenian. Abundant thermophilous plants and Classopollis, together with frequent occurrences of red beds and carbonate nodules in the middle part of the Sangonghe Formation, are indicative of an arid climate in Central Asia at that time. This arid interlude should be responsible for the coal break, which may be related to the global warming in the early Toarcian. However, more precise dating evidence is needed to substantiate this.

Gene Profiling of the Ascorbate Oxidase Family Genes under Osmotic and Cold Stress Reveals the Role of AnAO5 in Cold Adaptation in Ammopiptanthus nanus.

The uplift of the Qinghai Tibet Plateau has led to a drastic change in the climate in Central Asia, from warm and rainy, to dry and less rainfall. Ammopiptanthus nanus, a rare evergreen broad-leaved shrub distributed in the temperate desert region of Central Asia, has survived the drastic climate change in Central Asia caused by the uplift of the Qinghai-Tibet Plateau. Ascorbate oxidase (AO) regulates the redox status of the apoplast by catalyzing the oxidation of ascorbate acid to dehydroascorbic acid, and plays a key role in the adaptation of plants to environmental changes. Analyzing the evolution, environmental response, and biological functions of the AO family of A. nanus is helpful for understanding how plant genome evolution responds to climate change in Central Asia. A total of 16 AOs were identified in A. nanus, all of which contained the ascorbate oxidase domain, most of which contained transmembrane domain, and many were predicted to be localized in the apoplast. Segmental duplication and tandem duplication are the main factors driving the gene amplification of the AO gene family in A. nanus. Gene expression analysis based on transcriptome data and fluorescence quantitative PCR, as well as enzyme activity measurements, showed that the expression levels of AO genes and total enzyme activity decreased under short-term osmotic stress and low-temperature stress, but the expression of some AO genes (AnAO5, AnAO13, and AnAO16) and total enzyme activity increased under 7 days of cold stress. AnAO5 and AnAO11 are targeted by miR4415. Further functional studies on AnAO5 showed that AnAO5 protein was localized in the apoplast. The expression of AnAO5 in yeast cells and the transient expression in tobacco enhanced the tolerance of yeast and tobacco to low-temperature stress, and the overexpression of AnAO5 enhanced the tolerance of Arabidopsis seedlings to cold stress. Our research provides important data for understanding the role of AOs in plant adaptation to environmental change.

Growth of the southern Tian Shan-Pamir and its impact on central Asian climate

Uplift and amalgamation of the high-elevation (>3000 m) Tian Shan and Pamir ranges in Central Asia restricts westerly atmospheric flow and thereby limits moisture delivery to the leeward Taklimakan Desert in the Tarim Basin (<1500 m), the second largest modern sand dune desert on Earth. Although some research suggests that the hyper-arid conditions observed today in the Tarim Basin developed by ca. 25 Ma, stratigraphic evidence suggests the first erg system did not appear until 12.2 Ma. To address this controversy and to understand the tectonic influences on climate in Central Asia, we studied a continuous, 3800-m-thick stratigraphic section deposited from 15.1 to 0.9 Ma now exposed within the western Kepintagh fold-and-thrust belt in the southern Tian Shan foreland. We present new detrital zircon data (n = 839), new carbonate oxygen (δ18Oc) and carbon (δ13Cc) stable isotope compositions (n = 368), structural modeling, and stratigraphic observations, and combine these data with recently published magnetostratigraphy and regional studies to reconstruct the history of deposition, deformation, and climate change in the northwestern Tarim Basin. We find that basins along the southern (this study) and northern (i.e., Ili Basin) margins of the Tian Shan were likely receiving similar westerly precipitation by 15 Ma (δ18Oc = ∼−8‰) and had similar lacustrine-playa environments at ca. 13.5 Ma, despite differences in sedimentary provenance. At ca. 12 Ma, an erg desert formed adjacent to the southern Tian Shan in the northwestern Tarim Basin, coincident with a mid- to late Miocene phase of deformation and exhumation within both the Pamir and southern Tian Shan. Desertification at ca. 12 Ma was marked by a negative δ18Oc excursion from −7.8 ± 0.4‰ to −8.7 ± 0.7‰ in the southern Tian Shan foreland (this study), coeval with a negative δ18Oc excursion (∼−11 to −13‰) in the Tajik Basin, west of the Pamir. These data suggest that only after ca. 12 Ma did the Pamir-Tian Shan create a high-elevation barrier that effectively blocked westerly moisture, forming a rain shadow in the northwestern Tarim Basin. After 7 Ma, the southern Tian Shan foreland migrated southward as this region experienced widespread deformation. In our study area, rapid shortening and deformation above two frontal foreland faults initiated between 6.0 and 3.5 Ma resulted in positive δ13Cc excursions to values close to 0‰, which is interpreted to reflect exhumation in the Tian Shan and recycling of Paleozoic carbonates. Shortening led to isolation of the study site as a piggy-back basin by 3.5 Ma, when the sediment provenance was limited to the exhumed Paleozoic basement rocks of the Kepintagh fold belt. The abrupt sedimentologic and isotopic changes observed in the southern Tian Shan foreland appear to be decoupled from late Cenozoic global climate change and can be explained entirely by local tectonics. This study highlights how tectonics may overprint the more regional and global climate signals in active tectonic settings.

Phenological Changes and Driving Forces of Lake Ice in Central Asia from 2002 to 2020

Lake ice phenology is an indicator of past and present climate, it is sensitive to regional and global climate change. In the past few decades, the climate of Central Asia has changed significantly due to global warming and anthropogenic activities. However, there are few studies on the lake ice phenology in Central Asia. In this study, the lake ice phenology of 53 lakes in Central Asia were extracted using MODIS daily LST products from 2002 to 2020. The results show that MODIS-extracted lake ice phenology is generally consistent with Landsat-extracted and AVHRR-extracted lake ice phenology. Generally, lakes in Central Asia start to freeze from October to December. The trends in the lake ice phenology show strong regional differences. Lakes distributed along the Kunlun Mountains show overall delayed trends in all lake ice phenology variables, while lakes located in southwestern Central Asia show clear advancing trends in the freeze-up start dates (7.06 days) and breakup end dates (6.81 days). Correlations between the phenology of lake ice and local and climatic factors suggest that the ice breakup process and the duration of its complete coverage depend more on heat, while precipitation mainly affects the freezing time of the ice. Wind speed mainly affects the time of completely frozen of ice. In general, the breakup process is more susceptible to climatic factors, while local factors have strong influences on the freeze-up process.

A high spatiotemporal resolution land surface temperature research over Qinghai-Tibet Plateau for 2000–2020

As ‘the third pole of the world’, the land surface temperature (LST) of the Qinghai-Tibet Plateau (QTP) has a profound impact on the climate of central Asia and even the whole earth. Studying the impact of the LST over QTP depends on long time and high spatiotemporal resolution LST dataset. However, the unavailability of such dataset has hindered LST-related researches: one of the most important reasons is that traditional spatiotemporal fusion methods such as Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) have heavy computation demands to process big data. To fill this gap, this paper outlines one new cloud spatiotemporal fusion method by combining Google Earth Engine and STARFM to develop for the first time a 3-hourly 30 m LST dataset over the QTP from 2000 to 2020 through fusing Landsat and GLDAS-2.1 derived LST data. The outlined method first fuses the LSTs obtained from Landsat and GLDAS-2.1 data within one year to synthesize the LST of the entire QTP on one base time, and then the base time LST is spatiotemporally fused with GLDAS-2.1 LSTs on the base and prediction times to derive the 3-hourly 30 m QTP's LSTs on prediction times. The outlined method provides a promising technical scheme for batch processing big data in combining traditional spatiotemporal fusion methods with cloud computing platforms. Derived LST dataset is validated by station observations at multiple time and spatial scales to have high accuracy, which provides a guarantee for analyzing water and heat exchange and climate change over the QTP.

Northward Expansion of Desert Climate in Central Asia in Recent Decades

AbstractClimate variation in Central Asia is examined using changes of climate classification to obtain geographically specific information of the variation across the region. Major results show the northward expansion of desert climate by over 100 km in mid‐latitudes of the region since the 1980s. In the meantime, all types of climates in the region have increased temperatures. In mountainous areas, previous cold climate is replaced by warmer and also wetter climate. These changes could have largely resulted in the fast retreat of glaciers and the temporary rise of groundwater and the water levels of lakes in the drainage areas in recent decades. Because different climate types are associated with specific flora and fauna, the shifts of the climate types in locations have elevated the potential to initiate new feedbacks of the ecological systems to the climate and complicate its variation.

EFFECTS OF SUNLIGHT AND SHADOW ON THE SURFACES OF PIGEON TOWERS IN CENTRAL ASIA: CASE STUDIES IN IRAN, QATAR, EGYPT AND SAUDI ARABIA

In many parts of the world, especially Central Asia, pigeon towers have been constructed as traditional buildings with different forms and types to keep pigeons. These buildings are cylindrical, cubic, dome-like and multi-cylinder in shape. This study was conducted to identify the effects of sunlight and shadow on the surfaces of pigeon towers in Iran, Qatar, Egypt, and Saudi Arabia with hot and dry or humid climates. Several pigeon towers with different types and structures in these countries were selected and modeled in detail in Rhino 5. Radiance and Ecotect were then employed to measure solar radiation and shadow on the surfaces of the pigeon towers on the hottest day of the year. According to the graphical and numerical results obtained, sunlight and shadow differently affected the surfaces of the different pigeon towers. The effect level of sunlight and shadow on the single-form pigeon towers was higher than on the vaults. In fact, solar radiation was lower and shadow was higher per square meter of the surfaces of the vaults constructed as pigeon towers in close proximity. These houses were therefore found to be the optimal type for the hot and dry or humid climate in Central Asia.

The problems of livestock theft in Tuva: History and modernity (ethnic and legal aspects)

One of the most important achievements of the Tuvans in the process of adaptation to the nomadic culture and to the extreme continental climate of Central Asia was the breeding of various domestic animals adapted to different ecological conditions of the region. The main wealth of a nomad is livestock: horses, camels, cattle, sheep and goats, yaks, and reindeer. The article analyses the problems of livestock theft in Tuva from the mid-nineteenth century to the current state, as well as structure and dynamics of livestock theft. The main reasons for livestock theft and its reduced detection are analysed. On the basis of the conducted research, the authors have revealed a subjective portrait of a Tuvan livestock thief. Grazing as one of the factors of stock theft was studied. Suggestions on preventing livestock theft and recommendations on counteracting this crime are made.

Late 19th - Early 20th Century Western Scholars Have Analyzed Data On The Climate, Nature, Flora And Fauna Of Central Asia

In the study of the history of Uzbekistan, in addition to local sources, the study of works and research by foreign authors can be used in a scientific and objective analysis of possible controversies on the subject. The periodic boundaries of our research work cover the late 19th and early 20th centuries. During this period, a number of foreign ambassadors, traders and tourists visited Central Asia. Many of them write about their experiences here and later write about it. Such manuscripts and works also contain a wealth of impressions and information on the nature and climate of Central Asia at that time.

High-resolution dynamical downscaling for regional climate projection in Central Asia based on bias-corrected multiple GCMs

Central Asia (CA) is among the most vulnerable regions to climate change due to the fragile ecosystems, frequent natural hazards, strained water resources, and accelerated glacier melting, which underscores the need to achieve robust projection of regional climate change. In this study, we applied three bias-corrected global climate models (GCMs) to conduct 9 km-resolution regional climate simulations in CA for the reference (1986–2005) and future (2031–2050) periods. The regional climate model (RCM) and GCM simulated daily temperature and precipitation are evaluated and the results show that both the bias-correction technique and dynamical downscaling method obtain numerous added values in reproducing the historical climate in CA, respect to the original GCMs. The former contributes more to reducing the biases of the climatology and the latter contributes more to capturing the spatial pattern. The RCM simulations indicate significant warming over CA in the near-term future, with the regional mean increase of annual mean temperature in a range of 1.63–2.01 ℃, relative to the reference period. Pronounced warming is detected north of ~ 45° N in CA from autumn to spring, which can be explained by the snow-albedo feedback. Enhanced warming projected in many mountains in the world is not found in CA, which is consistent with the study based on the reanalysis datasets during the past. Heatwave day frequency, number and maximum duration are expected to become more severe by 2031–2050. Changes in precipitation and Standard Precipitation Index (SPI) shows a wetter condition in CA in the coming decades. However, a fairer assessment of the wet/dry change with Standard Precipitation Evapotranspiration Index (SPEI) which takes into account of both precipitation and potential evapotranspiration reveals a drier condition. The climate change projections presented here serve as a robust scientific basis for assessment of future risk from climate change in CA.

Palaeoenvironmental changes in Eocene Tibetan lake systems traced by geochemistry, sedimentology and palynofacies

• Late Eocene continental climate in Central Asia remains poorly understood. • Tibetan lake deposits preserve records of Eocene palaeoenvironmental changes. • Saline lakes in east-central Tibet existed in a cool and semi-arid desert-steppe. • Late Eocene aridification caused a palaeoenvironmental shift in Central Asia. • Tibetan palaeoclimate was primarily influenced by regional to global drivers. Ancient lake deposits preserve detailed records of Cenozoic environmental changes, providing information on past climate, vegetation, precipitation and lake chemistry. This study focuses on palaeoenvironmental changes recorded in Eocene limnic environments across what is today the modern Tibetan Plateau. We describe a section dated as late Eocene (~38–37 Ma) and integrate these findings within a regional context of similarly-aged Tibetan lake deposits across the plateau. These sedimentary archives of environmental change indicate a period of late Eocene aridification and cooling in the lead-up to the greenhouse-icehouse transition, which remains poorly understood in Central Asia. We show, based on geochemical, sedimentological, and palynofacies analyses, that a large saline lake existed within a semi-arid to arid steppe environment in the Nangqian Basin, east-central Tibet. The saline lake experienced cyclic drying intervals with shifts to a playa lake / mudflat system. Evidence of increased aridity is recorded in the upper part of the section, including a thinning of gypsum beds, decrease in palynomorph abundance, and concurrent increase in wood debris and amorphous organic matter. This is consistent with late Eocene aridity in Asia, drying of the playa lake, and an impoverished desert-steppe vegetation. Grain size data and geochemistry indicate a stable provenance of sedimentary material, suggesting that tectonic activity did not dominate sedimentation in east-central Tibet during deposition of these successions. Rather, palaeoenvironmental changes across the Tibetan region were most probably controlled by global climate oscillations and retreat of the proto-Paratethys Sea during the late Eocene: knowledge that is relevant for ecological interpretations through the Cenozoic, Quaternary and to the present.

THE HISTORIOGRAPHY OF WORKS BY WESTERN RESEARCHERS ON THE NATURE AND CLIMATE OF CENTRAL ASIA IN THE THE SECOND HALF OF THE 19TH CENTURY AND IN THE EARLY TWENTIETH CENTURY

The periodic boundaries of our research work cover the late 19th and early 20th centuries. During this period, a number of foreign ambassadors, traders and tourists visited Central Asia. Many of them write about their experiences here and later write about it. Such manuscripts and works also contain a wealth of impressions and information on the nature and climate of Central Asia at that time.

Projections of desertification trends in Central Asia under global warming scenarios

Central Asia (CA) is a core area of global desertification, but the effect of the intensifying “global greening” policy on the desertification process under global warming scenarios in CA remains unclear. Based on multi-source remote sensing data and Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) 2b climate data, this study investigated desertification in CA using actual evapotranspiration (ETa), temperature and precipitation as driving factors. Coupling with the CA-Markov model, the inversion method of desertification was improved, and the evolution normal form of desertification in CA was proposed. Finally, spatio-temporal variations of desertification in CA were quantified. The results indicate that temperature, precipitation, and normalized difference vegetation index (NDVI) in CA increased during the historical period (1980–2015), with sudden changes in 1994. In contrast, although ETa exhibited fluctuating increases (7.41 mm/10 yr) during this period, no sudden changes were observed in 1994. In the future (2006–2099), the climate of CA will become warmer and wetter. With reference to 1980–2005, precipitation under global warming of 2.0 °C (GW2.0) will be higher than that under global warming of 1.5 °C (GW1.5) by 10.3 mm, and ETa will increase by 20.88 mm and 27.54 mm under GW1.5 and GW2.0, respectively. Although the area of desert lands has decreased (5.94 × 104 km2/10 yr), the area of potential desert lands has increased (0.17 × 104 km2/10 yr). With global warming, this situation will continue to intensify, mainly in Xinjiang of China, and Kazakhstan. The Aral Sea plays an important role in the desertification of CA. The potential increase in desert land under GW2.0 is equivalent to the current water area of the Aral Sea. The findings could provide policy support for combating desertification in CA and promoting the achievement of the Sustainable Development Goals.

Dryland Forest Restoration Under a Changing Climate in Central Asia and Mongolia

Diverse environmental gradients in Central Asia and Mongolia, from high mountain forests to semi-desert lowlands salinized by past agriculture and water withdrawals, pose challenges to restoring degraded forests and landscapes. Technical approaches in dryland forestry and agroforestry methods are available to overcome these challenges, but to be fully effective, require policy and institutional changes. Climate variability and natural hazards are features of the region and the future is projected to become more arid with more intense rainfall. Closed forests, open woodlands, and shrublands are features of the dryland landscape, and provide a variety of ecosystem functions and services to be restored. In this work, steps in the restoration process are discussed, including halting degradation, conserving and rehabilitating existing forests, restoring dryland forests and agroforestry where trees are lacking, and adapting to climate change.

Profiling Aerosol Optical Properties at the Central Asian Site of Dushanbe, Tajikistan: Pure Dust Cases

Tajikistan is often affected by atmospheric mineral dust originating from various surrounding deserts. The direct and indirect radiative effects of that dust play a sensitive role in the Central Asian climate system and therefore need to be quantified. The Central Asian Dust Experiment (CADEX) provides for the first time an aerosol climatology for Central Asia based long-term aerosol profiling by ground-based lidar (PollyXT type) in Dushanbe, Tajikistan. For pure dust cases, mean depolarization(lidar) ratios of 0.23±0.03(44±3 sr) at 355 nm and 0.32±0.02(38±3 sr) at 532 nm wavelength have been measured. The mean extinction-related Ångström exponent was 0.18±0.15.

A 2000 year-long proxy and observational reconstruction of Central Asian climate

Central Asia (CA) is one of the most arid places on Earth and climate change threatens to disrupt the natural hydrologic systems that store its limited annual wet-season precipitation in glaciers and release it during the dry season. Warm/Wet and Cold/Dry periods recorded over the last 2000 years using multiple paleoclimate proxy records reflect a local hydrocycle dominated by the Westerlies and moisture recycling within the Aral Sea catchment.The best tool for assessing recent climate trends is modern reanalysis modeling, ground-truthed by weather station data. Using the best-fit reanalysis, we find warming and drying trends have dominated the region over the last 115 years. Continued warming and drying in glacierized eastern CA during the critical spring season when glaciers typically increase in mass increase the likelihood that human infrastructure will be needed to impound wet-season precipitation.

Variability of the Cold Season Climate in Central Asia. Part II: Hydroclimatic Predictability

Abstract Central Asia (CA) is subjected to a large variability of precipitation. This study presents a statistical model, relating precipitation anomalies in three subregions of CA in the cold season (November–March) with various predictors in the preceding October. Promising forecast skill is achieved for two subregions covering 1) Uzbekistan, Turkmenistan, Kyrgyzstan, Tajikistan, and southern Kazakhstan and 2) Iran, Afghanistan, and Pakistan. ENSO in October is identified as the major predictor. Eurasian snow cover and the quasi-biennial oscillation further improve the forecast performance. To understand the physical mechanisms, an analysis of teleconnections between these predictors and the wintertime circulation over CA is conducted. The correlation analysis of predictors and large-scale circulation indices suggests a seasonal persistence of tropical circulation modes and a dynamical forcing of the westerly circulation by snow cover variations over Eurasia. An EOF analysis of pressure and humidity patterns allows separating the circulation variability over CA into westerly and tropical modes and confirms that the identified predictors affect the respective circulation characteristics. Based on the previously established weather type classification for CA, the predictors are investigated with regard to their effect on the regional circulation. The results suggest a modification of the Hadley cell due to ENSO variations, with enhanced moisture supply from the Arabian Gulf during El Niño. They further indicate an influence of Eurasian snow cover on the wintertime Arctic Oscillation (AO) and Northern Hemispheric Rossby wave tracks. Positive anomalies favor weather types associated with dry conditions, while negative anomalies promote the formation of a quasi-stationary trough over CA, which typically occurs during positive AO conditions.