We have reconstructed the Palmer Drought Severity Index (PDSI) from 1580 to 2005 for Western Tian Shan, Central Asia, using tree rings of Picea schrenkiana. The reconstruction explains 35% of the actual January-May PDSI variance during the common period 1925-2005. Split-sample validation supports our use of the reconstruction model based on the full period of reliable observational data (1925-2005). Spatial climate correlation analyses with gridded PDSI data revealed that our PDSI reconstruction represents a strong regional drought signal for Western Tian Shan. Dry periods occurred during ad 1614-1628, 1700-1722, 1758-1790, 1806-1833, 1873-1898, 1908-1936, 1943-1951, 1960-1966 and 1973-1988; while the periods of ad 1580-1613, 1629-1699, 1723-1757, 1791-1805, 1834-1872, 1899-1907, 1937-1942, 1952-1959, 1967-1972 and 1989-present were relatively wet. Our reconstruction agrees reasonably well with the dry and wet periods previously estimated from tree rings in Tian Shan. Significant spectral peaks are identified at 2-5, 60.2 and 213 years. Our reconstructed drought is significantly correlated with sea surface temperature in the North Atlantic and Indo-West Pacific Oceans. The linkages to the North Atlantic and Indo-West Pacific Oceans suggest the connection of moisture variations of Central Asia to the westerly circulation and tropical ocean-atmosphere systems.

A 426-year drought history for Western Tian Shan, Central Asia, inferred from tree rings and linkages to the North Atlantic and Indo–West Pacific Oceans

The aerosol optical properties at the center of the Taklimakan Desert in Northwest China are investigated based on the measurements of aerosol optical depth (AOD) and Angstrom exponent from 2004 to 2008. A seasonal variation is found with high AOD and low Angstrom exponent values in spring and summer, due to the effect of dust storm events, and low AOD in autumn and winter. The maximum and minimum AOD occur in April (0.83 ± 0.41) and November (0.19 ± 0.10), respectively, with the maximum and minimum Angstrom exponent in January (0.70 ± 0.25) and May (0.09 ± 0.06), respectively. The diurnal variation of AOD (Angstrom exponent) shows the characteristic of high (low) values about 0.50– 0.60 in the morning and evening, and is constant around 0.40 during daytime. The relationship between AOD and the Angstrom exponent can be fitted by a power equation with a R 2 of 0.55. The frequency distributions of AOD and the Angstrom exponent occurrence probability have a single peak distribution, and can be well fitted by a two-mode distribution.

/pdf/variation-of-aerosol-optical-properties-over-the-taklimakan-jax69v2kb6.pdf

Variation of Aerosol Optical Properties over the Taklimakan Desert in China

Based on the historical and RCP8.5 experiments from 25 Coupled Model Intercomparison Project phase 5 (CMIP5) models, the impacts of sea surface temperature (SST) warming in the tropical Indian Ocean (IO) on the projected change in summer rainfall over Central Asia (CA) are investigated. The analysis is designed to answer three questions: (1) Can CMIP5 models reproduce the observed influence of the IO sea surface temperatures (SSTs) on the CA rainfall variations and the associated dynamical processes? (2) How well do the models agree on their projected rainfall changes over CA under warmed climate? (3) How much of the uncertainty in such rainfall projections is due to different impacts of IO SSTs in these models? The historical experiments show that in most models summer rainfall over CA are positively correlated to the SSTs in the IO. Furthermore, for models with higher rainfall-SSTs correlations, the dynamical processes accountable for such impacts are much closer to what have been revealed in observational data: warmer SSTs tend to favor the development of anti-cyclonic circulation patterns at low troposphere over north and northwest of the Arabian Sea and the Bay of Bengal. These anomalous circulation patterns correspond to significantly enhanced southerly flow which carries warm and moisture air mass from the IO region up to the northeast. At the same time, there is a cyclonic flow over the central and eastern part of the CA which further brings the tropical moisture into the CA and provides essential moist conditions for its rainfall generation. In the second half of twenty-first century, although all the 25 models simulate warmed SSTs, significant uncertainty exists in their projected rainfall changes over CA: half of them suggest summer rainfall increases, but the other half project rainfall decreases. However, when we select seven models out of the 25 based on their skills in capturing the dynamical processes as observed, then the model projected changes are much closer. Five out of the seven models predicted more rainfall over CA. Such a result is helpful for allowing us to attribute part of the observed upward rainfall trend in the CA region in the last several decades to the IO SST warming.

/pdf/impacts-of-sst-warming-in-tropical-indian-ocean-on-cmip5-4zjmj2oy4n.pdf

Impacts of SST Warming in tropical Indian Ocean on CMIP5 model-projected summer rainfall changes over Central Asia

https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/asl.928

Impact of El Niño and Southern Oscillation on the summer precipitation over Northwest China

Striped hyena (Hyaena hyaena) is a near-threatened large carnivore known to occur in arid and semi-arid landscapes in many parts of the world. Its population is declining globally and ecological information is required urgently to meet their conservation needs. We studied the diet pattern of the striped hyena in the semi-arid Gir National Park and Sanctuary (GNPS), western India. Prey items eaten by the striped hyena were identified from scats. Around 44.4% scats represented single to three mammalian preys while 55.6% of them represented four preys to seven preys. A variety of food items were identified including mammals, birds, insects and vegetable matters. Scats analysis showed that 63.91% diet of striped hyena was contributed by wild prey items, 20.94% by domestic prey and 3.31% by birds, whereas vegetable and insects contributed 9.92% and 1.93%, respectively. Diet diversity of the striped hyena computed by the Shannon-Weiner Index (H) was found to be 2.64. The presence of domestic mammals in the scat remains implied that the striped hyena might frequently visit human habitation in search for food and hence, a potential conflict between human and wildlife might arise. Reducing the dependence of hyena on domestic livestock is a challenge to ensure the survival of striped hyena outside the protected area.

Food habits of striped hyena (Hyaena hyaena) in a semi-arid conservation area of India

The relationship between the summer precipitation in northern Xinjiang and sea surface temperature was investigated using monthly precipitation data during 1960-2004 of 36 meteorological stations in northern Xinjiang and monthly mean sea surface temperature data during 1960 2004 reconstructed by NCEP/NCAR. The results were as follows. Summer precipitation anomaly in northern Xinjiang didn't relate to ENSO. Summer precipitation anomaly in northern Xinjiang was remarkably sensible to sea surface temperature anomaly in last winter and spring in 5 sea areas which were northern Indian Ocean (20°S-20°N,60°-110°E), western Pacific warm pool and Kuroshio extent (0°-30°N, 110°-150°E), tropical middle-eastern Pacific (5°S-5°N, 80°-150°W), northern Atlantic (30°-50°N, 20°-60°W)and tropical Atlantic (0°-20°N, 20°-60°W). There is a prominently positive correlation between summer precipitation in northern Xinjiang and spring sea surface temperature anomaly in the 5 sea areas, and it can be used for prediction of summer precipitation in northern Xinjiang.

Relationship Between Summer Precipitation in Northern Xinjiang and Sea Surface Temperature Anomalies

The Urumqi Institute of Desert Meteorology under the China Meteorological Administration(CMA) launched a scientific experiment with the radar wind profiler at the Tazhong Station—an experimental site for atmospheric environment observations in the hinterland of the Taklimakan Desert in July—October 2010.This study uses high temporal resolution data from the experiment to analyze the turbulence development of boundary layer, vertical velocity and atmospheric virtual temperature of typical clear-air day.The results show that:(1) The turbulence refractive index structure constant(C_n~2) can reflect in detail the development of turbulence,and the height of turbulence development bloom area in summer days may be reached at 4000 m.(2) RASS system has good credibility for atmospheric virtual temperature detection,and its near boundary layer is generally in line with the daily temperature variation.(3) The clear-air days in Taklimakan Desert are mainly controlled by east and northeast winds,the wind speed is relatively small and changes within 2.0—6.0 m·s~(-1).The atmospheric vertical velocity change of the desert hinterland fits in with the static equilibrium theory,the vertical velocity is very weak, generally in the -1.0 to 1.0 m·s~(-1) range fluctuations.

Radar Wind Profiler Observations of Convective Boundary Layer During Clear-Air Days over Taklimakan Desert

Wind fields at boundary layer in hinterland of the Taklimakan Desert were investigated by the CFL-03 Wind Profile Radar.Its observation data from April 1 to November 30,2010 were used to figure out the spatio-temporal patterns of boundary layer wind fields in hinterland of the Taklimakan Desert.The wind field structures are similar in spring and autumn: wind direction at upper layer is west and wind speed is relatively high,while wind direction at lower layer is east and wind speed is relatively low.In summer,wind speed decreases at upper layer and increases at the lower layer,so wind speed changes little from the ground to high altitude;a clear wind shear region exists in 100~200 m altitude due to impact of weather systems.

Wind Field at Boundary Layer in Hinterland of the Taklimakan Desert

The aerosol scattering proterties in the hinterland of Taklimakan Desert was continuously observed by integrating Nephelometer in 2004,which in combining with the data of mass concentration of PM10,the visibility and the routine weather observation,the seasonal and daily variation features of aerosol scattering coefficients and its correlation with the PM10 and the visibility were analyzed.The results indicate that the hourly mean aerosol scattering coefficient,the mean mass concentration of PM10,and the mean visibility at TaZhong in 2004 were 124.74±187.30 Mm-1,538.9±841.7 μg·m-3,and {12 748}±{7 274 m},respectively.The maximum frequency distribution of the hourly mean scattering coefficient is below 100 Mm-1,and the aerosol scattering coefficient is higher in the morning and evening,while it is lower at noon during a day.There are more particles in the air in the wee hours in winter and spring,so the aerosol scattering coefficients are more higher;The variations of the hourly mean aerosol scattering coefficient and the mass concentration of PM10 are consistent.The daily mean aerosol scattering coefficients and the visibility are significantly correlated,and their relationship might be described by a negative power function.

Aerosol Scattering Properties in the Hinterland of Taklimakan Desert

Variations of mean temperature,precipitation,relative humidity,and water vapor pressure in Urumqi city and suburb are analyzed in this paper based on climate data from seven meteorological stations.The results showed that the annual mean temperature in both regions increased apparently during the last 30 years except for a more obvious increasing trend in city than in suburb.In winter,air temperature in city is remarkably higher than that in suburb,showing strengthened "Heat Island Effect".The temperature difference between city and suburb is smaller in spring,summer and autumn.The change of temperature differentce between city and suburb during the past 30 years showed increasing trend in winter and decreasing trend in the other three seasons.Besides,the precipitation difference between city and suburb also increased at a rate of 3.7 mm per year in recent 30 years,and showed the highest difference(181.3 mm) in 2003.In this past 30 years,the relative humidity in city gradually decreased,while that in suburb increased,showing "Dry Island Effect";the vapor pressure difference between city and suburb also increased too,and the vapor pressure in suburb was always higher than that in city except in winter season.

Wang Minzhong

Papers

Relationship Between Summer Precipitation in Northern Xinjiang and Sea Surface Temperature Anomalies

Radar Wind Profiler Observations of Convective Boundary Layer During Clear-Air Days over Taklimakan Desert

Wind Field at Boundary Layer in Hinterland of the Taklimakan Desert

Aerosol Scattering Properties in the Hinterland of Taklimakan Desert

Comparison of Climate Parameters between Urumqi City and Suburb in Recent 30 Years