Improvement and Evaluation of a Parameterization Scheme for Assessing Dust Devils as Dust Emission in the Northern Margin of the Taklimakan Desert

Based on meteorological and dust devil intensification observation data in the desert transition zone of the Xiaotang region in the northern margin of the Taklimakan Desert, and combined with GPS sounding in the hinterland of the Taklimakan Desert, this study investigated the improvement and evaluation of the dust devil parameterization scheme. The results indicate that the thermodynamic efficiency of dust devils after improvement was significantly higher than that before improvement, improving the values by 84.7%, 63.9%, 25.6%, 13.3%, 12.5%, 22.7%, 26.6%, 26.9%, and 21.4% for the hourly intervals from 09:00–17:00, respectively. The annual occurrence of dust devils after improvement was 431 times, 55.2% more than before improvement. The correlation coefficients of convective boundary layer height after improvement was 0.96, higher than that before improvement (0.908). After the improvement, the total annual dust emission time was 181.3 h, 95.9% less than that calculated using the day length before improvement, and 31.8% more than that calculated using sunshine time before improvement. After the improvement, the average vertical dust flux of a single dust devil was 0.25 m2/s, 68.8% less than that before improvement. After the improvement, the average annual dust emission from dust devils per square kilometer was 15.3 t/km2, significantly lower than the value of 320.5 t/km2 before the improvement, approximately one-twentieth of the value.

Study on Surface and Internal Humidity of Dunes in the Southwestern Margin of the Taklimakan Desert

Greening on the edge of desert is an effective way to prevent and control desertification. This paper studies the humidity characteristics of sand samples collected from the surface and interior of dunes in the southwestern edge of the Taklimakan Desert, whose geographic coordinates are 39°43’37” – 39°43’41” N, 78°43’02” – 78°43’09” E. The humidity of sand samples at vertical depths under five different surface positions of windward slope bottom, windward slope middle, windward slope top, leeward slope middle and leeward slope bottom was studied. On the surface of the sand at different locations and at the same depth under the surface, the sand humidity is greater closer to the bottom of the slope, for both windward slope and leeward slope. The humidity gradient values on the surface and at different depths on different positions of the dunes are obtained. Finally, recommendations are provided for effective ways to prevent desertification in the desert edge of Kashgar.

Streptomyces Pimoensis sp. nov., Isolated From the Taklimakan Desert in Xinjiang, China

A novel Streptomyces strain, designated TRM 75549T, was separated from a sample of sand in Pimo, Taklimakan desert, Xinjiang, North-West China. Phylogenetic analyses of the 16S rRNA gene sequences placed strain TRM75549T within the genus Streptomyces with the highest similarities to Streptomyces flavoviridis NBRC 12772T (98.76%). The whole-genome average nucleotide identity (ANI) value between strain TRM75549T and S. flavoviridis NBRC 12772T is 88.20%. Digital DNA-DNA hybridization (dDDH) value between strain TRM75549T and S. flavoviridis NBRC 12772T is 44.10%. They are well below the recommended 95-96% and 70% cut-off points for designated species respectively. A multi-locus sequence analysis of five house-keeping genes (atpD, gyrB, recA, rpoB and trpB) and phylogenomic analysis also illustrated that strain TRM75549T should be assigned to the genus Streptomyces. Strain TRM75549T contained MK-9 (H6) and MK-9 (H8) as predominant menaquinones. The diagnostic diamino acid of cell walls was identified as LL-diaminopimelic acid and Meso-diaminopimelic. The whole-cell sugar pattern of strain TRM 75549T consisted of mannose and glucose. The major fatty acids (>5%) were iso-C14:0, iso-C15:0, anteiso-C15:0, iso-C16:1H, iso-C16:0. The polar lipids were diphosphatidylglycerol, lysophosphatidylglycerol, phosphatidylethanolamine, phospholipids, phosphatidylglycerol, phosphatidylinositol, phosphatiylinositol mannosides and unidentified phospholipids. Strain TRM75549T could be differentiated from S. flavoviridis NBRC 12772T, based on physiological and biochemical characteristics. Based on the data from this polyphasic study presented above, strain TRM75549T is represent ative of a novel species of the genus Streptomyces, for which the name Streptomyces pimoensis sp. nov. is proposed. The type strain is TRM75549T (=CCTCC AA 2020054T=LMG 32221T ).

Water Supply Increases N Acquisition and N Resorption from Old Branches in the Leafless Shrub Calligonum caput-medusae at the Taklimakan Desert Margin

Irrigation is the main strategy deployed to improve vegetation establishment, but the effects of increasing water availability on N use strategies in desert shrub species have received little attention. Pot experiments with drought-tolerant shrub Calligonum caput-medusae supplied with water at five field capacities in the range of 30–85% were conducted using local soil at the southern margin of the Taklimakan Desert. We examined the changes in plant biomass, soil N status, and plant N traits, and addressed the relationships between them in four- and seven-month-old saplings and mature shrubs after 28 months. Results showed that the growth of C. caput-medusae was highly responsive to increased soil moisture supply, and strongly depleted the soil available inorganic N pools from 16.7 mg kg−1 to an average of 1.9 mg kg−1, although the total soil N pool increased in all treatments. Enhancement of biomass production by increasing water supply was closely linked to increasing total plant N pool, N use efficiency (NUE), N resorption efficiency (NRE), and proficiency (NRP) in four-month saplings, but that to total plant N pool, NRE, and NRP after 28 months. The well-watered plants had lower N concentrations in senesced branches compared to their counterparts experiencing the two lowest water inputs. The mature shrubs had higher NRE and NRP than saplings and the world mean levels, suggesting a higher N conservation. Structural equation models showed that NRE was largely controlled by senesced branch N concentrations, and indirectly affected by water supply, whereas NRP was mainly determined by water supply. Our results indicated that increasing water availability increased the total N uptake and N resorption from old branches to satisfy the N requirement of C. caput-medusae. The findings lay important groundwork for vegetation establishment in desert ecosystems.

In-situ observation of warm atmospheric layer and the contribution of suspended dusts over the Tarim Basin

Basing on the radiosonde observations in the spring and summer during 2016–2017, an anomalous warm atmospheric layer is verified and the contribution of suspended dusts over the Tarim Basin (TB) is quantified. The result indicates a warm atmospheric layer between 300 hPa and 500 hPa with an average intensity of 2.53 K and 1.39 K in the spring and summer, respectively. Over the TB, where the world’s second largest moving desert, the Taklimakan Desert (TD) is distributed, large amounts of dust particles are emitted from the TD and suspended over the TB. Using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data, we found the dusts can be lifted to the upper atmospheric layer between 2.5 and 5.5 km above mean sea level over the TB. Consequently, the suspended dusts can exert a maximum heating effect of approximately +0.45 K and +0.25 K in spring and summer, respectively. The contribution of dust heating to the anomalous warm atmospheric layer over the TB is 13.77 % and 10.25 % in spring and summer, respectively. In view of the topographical feature, the TB is adjacent to the Tibetan Plateau (TP) which acts as an elevated heat source in spring and summer. The warm atmospheric layer over the TB seems a northward extension of Tibet heat source, the concept of which is proposed in this study. Such a northward extension of the elevated heating by the Tibetan Plateau could induce some profound impacts on the regional climate, especially on the western section of the “Silk Road Economic Belt”, and therefore demands more attention.

Characteristics of solar radiation at Xiaotang, in the northern marginal zone of the Taklimakan Desert

The characteristics of solar radiation and the influence of sand and dust on solar radiation in the northern margin of Taklimakan Desert were analyzed using radiation observation data from 2018. The results showed that the annual total radiation, direct radiation, and scattered radiation at Xiaotang were 5,781.8, 2,337.9, and 3,323.8 MJ m−2, respectively. The maximum monthly total radiation, direct radiation, and scattered radiation were observed in July (679.8 MJ m−2), August (317.3 MJ m−2), and May (455.7 MJ m−2), respectively. The aerosol optical depth corresponded well with the scattered radiation, and the maximum value was in May. Further analysis showed a significant correlation between the total radiation and solar height angle under different weather conditions. Under the same solar height angle, total radiation was higher during clear days but lower on sandstorm days. Calculation of atmospheric transmittance showed that the average atmospheric transmittance on a clear day was 0.67; on sand-and-dust days, it was 0.46. When the atmospheric transmittance was 0.5, the increase in scattering radiation by aerosol in the air began to decrease. Probability analysis of radiation indicated the following probabilities of total radiation <500 W m−2 occurring on clear, floating-dust, blowing-sand, and sandstorm days: 67.1%, 76.3%, 76.1%, and 91.8%, respectively. Dust had the greatest influence on direct radiation; the probabilities of direct radiation <200 W m−2occurring on clear, floating-dust, blowing-sand, and sandstorm days were 44.5%, 93.5%, 91.3%, and 100%, respectively, whereas those of scattered radiation <600 W m−2were 100%, 99.1%, 98.1%, and 100%, respectively. Therefore, the presence of dust in the air will reduce scattered radiation.

Increasing spring dust storms in the future over the Taklimakan Desert, Northwest China: implications from changes in circulation pattern frequency in CMIP6

Dust storms over the Taklimakan Desert (TD), Northwest China, not only influence human health but also affect regional climate through direct effects of dust aerosols on solar and longwave radiation. The Coupled Model Intercomparisons Project Phase 5 (CMIP5) models project a decrease in dust storms because of a decrease in dust emissions over the TD in the future under warming scenarios. However, inaccurate simulations of dust emissions cause the CMIP5 models to simulate dust storms poorly. Here we analyzed typical circulation patterns that initiate dust storms over the TD and examined changes in the frequency of typical circulation patterns derived from the CMIP6 models in an extreme warming scenario. The results show that there will be an increase in typical circulation pattern frequency in the latter half of the 21st century compared with 1958-2014, implying an increase in dust storms over the TD in the future under the extreme warming scenario. The increase in dust storms over the TD may be related to an increase in synoptic activities in the future from the Middle Asia to the TD, which is caused by a southern movement of subtropical westerly jet stream under the extreme warming scenario.