Tianding Han

A Bias-Corrected Precipitation Climatology for China

This paper presents the results of bias corrections of Chinese standard precipitation gauge (CSPG) measurements for wind-induced undercatch, a trace amount of precipitation, and wetting loss. Long-term daily data of precipitation, temperature, and wind speed during 1951‐98 at 710 meteorological stations in China were used for this analysis. It is found that wind-induced gauge undercatch is the greatest error in most regions, and wetting loss and a trace amount of precipitation are important in the low-precipitation regions in northwest China. Monthly correction factors ratio of corrected amount to measured amount of precipitation differ by location and by type of precipitation. Considerable interannual variation of the corrections exists in China due to the fluctuations of wind speed and frequency of precipitation. More importantly, annual precipitation has been increased by 8 to 740 mm with an overall mean of 130 mm at the 710 stations over China because of the bias corrections for the study period. This corresponds to 6%‐62% increases (overall mean of 19% at the 710 stations over China) in gauge-measured yearly total precipitation over China. This important finding clearly suggests that annual precipitation in China is much higher than previously reported. The results of this study will be useful to hydrological and climatic studies in China.

Regional difference of annual precipitation and discharge variation over west China during the last 50 years

Using annual precipitation and discharge data measured in the past five decades, this paper analyzed the regional differences over west China in terms of climate and discharge variations, and investigated the relationship between the regional characteristics and the activities of South and East Asian summer monsoon. Results revealed that the precipitation and discharge in the upper reaches of the Yellow River (Central West China) have a negative correlation with those in Xinjiang (northwest China) and the Yarlung Zangbo River (the upper reaches of the Brahmaputra Rive, southwest China) regions. The geographical patterns of precipitation and discharge variations are different over west China, i.e. the regional climate displays the alteration of dry-wet-dry or wet-dry-wet from north to south in west China. The negative correlation of annual discharges between Xinjiang and the upper reaches of the Yellow River is found statistically significant in the decadal scale, and that between the Yarlung Zangbo River and the upper reaches of the Yellow River is found active in the interannual scale. The regional characteristics indicate that the discharge/precipitation variations in the upper reaches of the Yellow River are dominated by the East Asian summer monsoon while their variations in Xinjiang are affected by both the west wind and East Asian summer monsoon.

Mass-balance characteristics of Ürümqi glacier No. 1, Tien Shan, China

Abstract The temporal and spatial variations of mass balance on different timescales were analyzed to identify their response to climate change using long-term observed mass-balance data covering the period 1959–2002 at Ürümqi glacier No. 1 at the headwaters of the Ürümqi river, Tien Shan, China. The results show that the accumulated glacier mass balance has decreased by 9599 mm w.e., which is equivalent to about 10 m mean thickness reduction. The negative mass balance has been accentuated in recent years, with a mean mass balance during the period 1997–2002 of –739.6 mm a−1. The glacier mass balance shows a clear periodicity, with positive and negative alternations of 7 and 15 years during the past several decades. Annual mass balance shows a significant negative correlation with summer air temperature from June to August. It is influenced more by annual air temperature than by annual precipitation. The temperature increase preceded the precipitation increase as an influence on the mass balance. Furthermore, monthly mass balance shows a negative correlation with monthly air temperature, significant at the 99% confidence level in July and August. Monthly mass balance is negatively correlated with precipitation in May and August at the 95% confidence level, but positively and insignificantly correlated with precipitation in June and July. The negative relationship between mass balance and precipitation might be related to concurrent increases of precipitation and temperature.

Response of the snowmelt and glacier runoff to the climate warming-up in the last 40 years in Xinjiang Autonomous Region, China

Some analytical results of the measured runoff during 1950s to 1980s at outlet hydrological stations of 33 main rivers and climatic data collected from 84 meteorological stations in Xinjiang Autonomous Region are presented. Comparison of hydrological and climatic parameters before and after 1980 shows that the spring runoff for most rivers after 1980s increased obviously at a rate of about 10%, though the spring air temperature did not rise very much. Especially. an increment by 20% for alpine runoff is observed during May when intensive snow melting occurred in the alpine region. To the contmy, the runoff in June decreased about 5%. When the summer or annual runoff is taken into account. direct relationship can be found between the change in runoff and the ratio of glacier-coverage, except the runoff in August when the glacier melting is strong, indicating that climatic warming has an obvious effect on the contribution of glacier melting to the runoff increase

Seasonal variations of organic carbon and nitrogen in the upper basins of Yangtze and Yellow Rivers

The profound impacts exerted by climate warming on the Tibetan Plateau have been documented extensively, but the biogeochemical responses remain poorly understood. This study was aimed at seasonal variations of total organic carbon (TOC) and total organic nitrogen (TON) in stream water at two gauging sections (TTH, ZMD) in the upper basin of Yangtze River (UBYA) and at four gauging sections (HHY, JM, JG, TNH) in the upper basin of Yellow River (UBYE) in 2013. Results showed that concentrations of TON exhibit higher values in spring and winter and lower values in summer. TOC exhibits higher concentrations in spring or early summer and lower concentrations in autumn or winter. Seasonal variations of TOC and TON fluxes are dominated by water flux. In total, the UBYE and UBYA delivers 55,435 tons C of organic carbon and 9,872 tons N of organic nitrogen to downstream ecosystems in 2013. Although the combined flux of TOC from UBYA and UBYE is far lower than those from large rivers, their combined yields is higher than, or comparable with, those from some large rivers (e.g. Nile, Orange, Columbia), implying that organic carbon from the Tibetan Plateau may exert a potentially influence on regional and/or global carbon cycles in future warming climate.