Mountain permafrost distribution modeling using Multivariate Adaptive Regression Spline (MARS) in the Wenquan area over the Qinghai-Tibet Plateau

In high mountainous areas, the development and distribution of alpine permafrost is greatly affected by macro- and mi- cro-topographic factors. The effects of latitude, altitude, slope, and aspect on the distribution of permafrost were studied to under- stand the dislribution patterns of permafrost in Wenquan on the Qinghai-Tibet Plateau. Cluster and correlation analysis were per- formed based on 30 m Global Digital Elevation Model （GDEM） data and field data obtained using geophysical exploration and borehole drilling methods. A Multivariate Adaptive Regression Spline model （MARS） was developed to simulate permafrost spa- tial distribution over the studied area. A validation was followed by comparing to 201 geophysical exploration sites, as well as by comparing to two other models, i.e., a binary logistic regression model and the Mean Annual Ground Temperature model （IVlAGT）. The MARS model provides a better simulation than the other two models. Besides the control effect of elevation on permafrost distribution, the MARS model also takes into account the impact of direct solar radiation on permafrost distribution.

Integrated hydrologic modeling in the inland Heihe River Basin, Northwest China

As a typical inland river basin in arid Northwest China, having distinct hydrological characteristics and severe and repre- sentative water problems, the Heihe River Basin （HRB） has attracted considerable research interest worldwide and in 2007 became a pilot basin of the G-WADI network of UNESCO/1HR Many research programs have been conducted in the HRB since the 1980s, producing rich knowledge and data about the basin, which will be very helpful to further studies. This paper reviews research efforts related to hydrologic modeling and ongoing model integration studies performed in the HRB in re- cent years. Recently, an observation network covering the whole area and a Web-based data-sharing system have been estab- lished which can greatly improve data acquisition. This paper tabulates modeling activities in past years, including model ap- plications, model modifications and enhancements, and model coupling efforts. Also described is a preliminary modeling in- tegration tool designed to quickly build new models, which has been developed for hydrologic modeling purposes. Challeng- es and issues confronted in current studies are discussed, pointing toward key research directions in the future.

Accuracy evaluation of two precipitation datasets over upper reach of Heihe River Basin, northwestern China

As an important forcing data for hydrologic models, precipitation has significant effects on model simulation. The China Meteorological Forcing Dataset （ITP） and Global Land Data Assimilation System （GLDAS） precipitation data are the two commonly used data sources in the Heihe River Basin （HRB）. This paper focused on evaluating the accuracy of these two precipitation datasets. A set of metrics were developed to characterize the trend, magnitude, annual allocation, event matching, frequency, and spatial distribution of the two datasets. Meanwhile, such accuracy evaluation was performed at various scales, i.e., daily, monthly, and yearly. By comparing with observations, this study concluded that： first, both ITP and GLDAS precipitation data well represented the trends at corresponding sites, and GLDAS underestimated precipita- tion in most regions except the east tributary headwater region; second, unusual annual precipitation distribution was observed in both datasets with overestimation of precipitation in May through September and GLDAS appeared to be much severe; third, the ITP data seriously over-predicted the precipitation events; fourth, the ITP data have better spatial distribution than GLDAS in the upper reach area of HRB. Overall, we recommended ITP precipitation data for the land surface study in the uooer reach of HRB.

An estimation of groundwater storage variations from GRACE gravity satellites in the Heihe River Basin, northwestern China

There are only limited surface water resources available in the Heihe River Basin （HRB）, a typical inland river basin in the arid region of northwestern China, where groundwater overexploitation is a serious problem. Groundwater has become one of main resources of fresh water in the HRB. In this paper, temporal and spatial variations of groundwater in the HRB are estimated by the Gravity Recovery and Climate Experiment （GRACE） satellites. Our analysis shows that groundwater storage in the HRB reaches its highest in the summer of 2005, and then begins to decline in the following years and reaches steady status in 2008. Spatially, groundwater shows a decline in the upper HRB in the first two years and a slight increase in the following years, while this phenomenon is reversed in the middle HRB where groundwater slightly increases in 2005 and then declines in the following three years. In the lower HRB, GRACE detects a continual increase in the full six-year period. This approach is proven successful when employed in the HRB and thus offers a new insight into monitoring groundwater variations in a river basin with limited or even without any observed data.

Mapping the permafrost stability on the Tibetan Plateau for 2005–2015

Data scarcity is a major obstacle for high-resolution mapping of permafrost on the Tibetan Plateau(TP).This study produces a new permafrost stability distribution map for the 2010 s(2005–2015)derived from the predicted mean annual ground temperature(MAGT)at a depth of zero annual amplitude(10–25 m)by integrating remotely sensed freezing degree-days and thawing degree-days,snow cover days,leaf area index,soil bulk density,high-accuracy soil moisture data,and in situ MAGT measurements from 237 boreholes on the TP by using an ensemble learning method that employs a support vector regression model based on distance-blocked resampled training data with 200 repetitions.Validation of the new permafrost map indicates that it is probably the most accurate of all currently available maps.This map shows that the total area of permafrost on the TP,excluding glaciers and lakes,is approximately 115.02(105.47–129.59)×10^4 km^2.The areas corresponding to the very stable,stable,semi-stable,transitional,and unstable types are 0.86×10^4,9.62×10^4,38.45×10^4,42.29×10^4,and 23.80×10^4 km^2,respectively.This new map is of fundamental importance for engineering planning and design,ecosystem management,and evaluation of the permafrost change in the future on the TP as a baseline.

Toward an improved data stewardship and service for environmental and ecological science data in West China

Sharing of scientific data can help scientific research to flourish and facilitate more widespread use of scientific data for the benefit of society.The Environmental and Ecological Science Data Center for West China(WestDC),sponsored by the National Natural Science Foundation of China(NSFC),aims to collect,manage,integrate,and disseminate environmental and ecological data from western China.It also aims to provide a long-term data service for multidisciplinary research within NSFC’s‘‘Environment and Ecology of West China Research Plan’’(NSFC West Plan).An integrated platform has been developed by the WestDC,and this has the function of data sharing,acting as a knowledge repository.Major data sets developed by the WestDC include basic geographic data,the regionalization of global data set for China,scientific data for cold and arid regions in China,scientific data for the cryosphere in countries that neighbor China,data relating to the inland river basins in northwestern China,and data submitted by the NSFC West Plan projects.In compliance with the‘‘full and open’’data sharing policy,most data in the WestDC can be accessed online.Highlights include detailed data documentation,the integration of data with bibliographic knowledge,data publishing,and data reference.