Editor’s note

The past two decades have witnessed great progress in development of ultrashort laser pulse in laser science, often at an unexpected speed. It has found various applications, both theoretical and practical, in the frontiers of science.     

The altitude effect of δ 18O in precipitation and river water in the Southern Himalayas

The lapse rate of water isotopes is used in the study of the hydrologic cycle as well as in the estimation of uplift of the Tibetan Plateau.The greater elevation contrast in the Southern Himalayas allows for a detailed discussion about this lapse rate.We analyze variations of 18δO in precipitation and river water between 1320 m and 6700 m elevations in the Southern Himalayas,and calculate the specific lapse rate of water 18δO.The results show that the multi-year average lapse rate in precipitation over this region is 0.15‰/100 m.The one-year average lapse rate is 0.17‰/100 m from three sites along the Southern Himalayas.The two results agree,but are much lower than the global average of 0.28‰/100 m.This work also shows that there is a difference in precipitation 18δO lapse rate between the monsoon and non-monsoon seasons.The calculated precipitation lapse rate is much lower than that in surface water.     

Recent high-resolution glaciochemical record from a Dasuopu firn core of middle Himalayas

A 16.8 m firn core of middle Himalayas was recovered on the col of Dasuopu glacier in August 2006, being 7000 m above sea level. A total of 317 samples were measured for stable oxygen isotope ratios （6180） and major ion concentrations （Na＋, NH＋, K＋, Mg2＋, Ca2＋, Cl-, SO4^2-, and NO3^-. The firn core dating and seasonal partitioning were carried out based on the marked seasonal variations along the stable oxygen isotopes and crustal species （Ca2＋, Mg2＋） profiles. The multi-parameters and high-resolution glaciochemical data set of Dasuopu firn core recorded the detailed chemical characteristics of pre cipitation in high-elevation region, middle Himalayas, since 1991 A.D., which mainly originated from the crustal and anthropogenic sources, while the sea-salt contribution was minor. The seasonal variability of major ion concentrations was dominated by the seasonal alternation of the prevalent air mass, atmospheric circulation situation and precipitation regime. Linear regression analysis indicated that most of the variance in annual ionic fluxes can be explained by a linear dependence on snow accumulation rate.     

Seasonal variations of dust record in the Muztagata ice cores

Based on the oxygen isotope ratio and microparticle record in ice cores recovered at Mt. Muztagata, Eastern Pamirs, the seasonal variations of atmospheric dust have been reconstructed for the past four decades. High dust concentrations and coarser particle grains have the similar trend with oxygen isotope value. Our statistical results indicate that 50%--60% high dust concentration samples occur during the season with high oxygen isotope values （summer）, while low dust storm frequency during spring and winter. Back-trajectory analysis shows that the air mass hitting Muztagata predominately came from West Asia （such as Iran-Afghanistan Plateau） and Central Asia, which are the main dust source area for Muztagata. Dust storms in those source areas most frequently occur during summer （from May to August）, while frequent dust storm events in northern China mainly occur during spring （March to May）. Regions in the path of Asian dust transport, such as in Japan, the North Pacific, and Greenland, also show high dust concentrations during spring （from March to May）. Our results indicate that dust storms have different seasonality in different regions within Asia.     

Editor’s note

In 1961, the Global Network Isotopes in Precipitation （GNIP） was operated by the IAEA in collaboration with WMO, and over 500 stations across the globe participated in this program. The initial objective of this program was the systematic collection of isotope data in precipitation to provide the basic isotopic data for the use of basic environmental isotopes in the hydrology within the scope of hydrological and geochemical cycle and water resources management. During the implementation of the program the close relationship between precipitation isotopes and air temperature was found. This finding was subsequently used in the paleoclimate study, and air temperature change had been reconstructed from isotopes in the ice sheets. Meanwhile, precipitation isotopes were also used to verify and improve atmospheric circulation models.     

Oxygen isotope variation in the water cycle of the Yamzho lake Basin in southern Tibetan Plateau

Given the potential use of stable isotope in the paleoclimate reconstruction from lacustrine records as well as in the local hydrology cycle, it is crucial to understand the processes of stable isotope evolution in catchment in the Tibetan Plateau region. Here we present a detailed study on the water oxygen isotope based on 2 years observation including precipitation, river water and lake water in the Yamzho Lake, south of the Tibetan Plateau. Temporal variation of local precipitation 5180 shows an apparent ＂monsoon cycle＂. In monsoon season, 5180 in waters is lower. In non-monsoon season, δ^18O in precipitation and lake water is higher and higher river δ^18O exists in spring, probably reflecting the effect of land surface evaporation, together with the higher δ^18O values in spring precipitation. It is also found that the surface lake water δ^18O varies seasonally and annually. The lower lake water δ^18O in the late summer is apparently related to the summer monsoon precipitation. The mean δ^18O value of lake water in 2007 is 1.2‰ higher than that in 2004, probably due to the less monsoon precipitation in summer of 2007, as can be confirmed from the precipitation data at the Langkazi meteorological data. It is also found that an obvious shift of vertical lake water δ^18O reflects the fast mixture of lake water. δ^18O values of lake water are over 10‰ higher than those of precipitation and river water in this region due to the evaporation fractionation. The modeled results show that the evaporation process of the lake water is sensitive to relative humidity, and the present lake water δ^18O reflects a relative humidity of 51% in the Yamzho Lake. It shows that the lake will take 30.5 years to reach present lake water δ^18O given a large shift in the input water δ^18O. The modeled results also reveal that surface lake water temperature and inflow δ^18O have slight effect on the isotopic balance process of lake water in the Yamzho Lake.     

Chernobyl nuclear accident revealed from the 7010 m Muztagata ice core record

The total activity variation with depth from a 41.6 m Muztagata ice core drilled at 7010 m, recorded not only the 1963 radioactive layer due to the thermonuclear test, but also clearly the radioactive peak released by the Chernobyl accident in 1986. This finding indicates that the Chernobyl nuclear accident was clearly recorded in alpine glaciers in the Pamirs of west China, and the layer can be potentially used for ice core dating in other high alpine glaciers in the surrounding regions.     

Seasonal transition characteristics of the westerly jet: Study based on field observations at an altitude of 6900 m on the Mt. Xixiabangma Dasuopu glacier

To better understand ultra-high-altitude climate characteristics and their changes, an automatic weather station was installed on August 4, 2005 on the Mt. Xixiabangma Dasuopu glacier (28°23.04′N, 85°43.72′E, 6900 m a.s.l.) in the middle of the Himalayas. Mountain weather conditions were observed continuously and automatically. This paper is the first to publish meteorological data for a whole year for a high-elevation region, and analyze wind direction, wind speed, air temperature, air pressure and humidity. Analysis of the observation data reveals that this region was strongly influenced by the westerly jet from October 10, 2005 to April 21, 2006 and by the Indian monsoon from May to September. The seasonal transitions of the westerly jet were characterized by changes in meteorological elements. In winter, influenced by the westerly jet, the wind speed in the study region was very high and fluctuated violently, gale days were frequent, temperature and air pressure fluctuated dramatically, the diurnal range of temperature decreased and the diurnal range of air pressure increased, relative humidity and specific humidity declined sharply, and air was dry. In summer, influenced by the Indian monsoon, the relative humidity and specific humidity were high. In addition, we analyzed reanalysis data for the location of the automatic weather station. The results confirmed that this region was strongly affected by the westerly jet from October 10, 2005 to April 21, 2006 and the observations that the seasonal transitions of the westerly jet were characterized by changes in meteorological elements.