Wang C.-L.,Guangdong Climate Center |
Guo J.,Tianjin Climate Center |
Chen H.-H.,Guangdong Climate Center |
Liu X.,Guangdong Climate Center
Chinese Journal of Ecology | Year: 2011
According to the principles of soil water balance, Penman-Monteith function was adopted to calculate potential evapotranspiration. The daily soil available moisture was simulated, and the daily dynamic drought-monitoring index was put forward based on soil moisture (SM). With the comparison of the standardized precipitation index (SPI), relative moisture index (MI), and combined meteorological drought index (CI) recommended by the 'meteorological drought levels of National Standards' (GB/T 20481-2006), the applicability of the daily dynamic drought-monitoring index based on SM in Guangdong was evaluated, and the results showed that the drought season (from November to next April) based on SM lagged one month, compared to rain-less period (from October to next March). The SM index could describe the lag effect and gradual change characteristics of drought relative to the annual change of precipitation, and objectively reflect the seasonal distribution of drought frequency in Guangdong. The drought index based on SM automatically implied the time cumulative effect of precipitation-evaporation process, and thereby, could describe the start, development, and end of drought process in detail. In terms of progressive development, precipitation sensitivity, and integrity of drought course, the drought index based on SM was of good application value.
Luo T.,CAS Institute of Tibetan Plateau Research |
Li M.,CAS Institute of Tibetan Plateau Research |
Li M.,Tianjin Climate Center |
Luo J.,CAS Chengdu Institute of Mountain Hazards and Environment
Ecological Research | Year: 2011
It is still unclear to what extent variations in foliar δ13C and nitrogen can be used to detect seasonal changes in canopy productivity. We hypothesize that in a wet and cloudy fir forest, seasonally higher litterfall and lower leaf area index (LAI) are correlated with higher mass-based leaf nitrogen (Nmass) and net primary productivity (NPP), while foliar δ13C may change with specific leaf area (SLA), area-based leaf nitrogen (Narea), and/or starch concentration. In order to test our hypotheses, stand-level litterfall and the means of δ13C, Nmass, Narea, SLA, and starch concentration of canopy needles for a wet and cloudy Abies fabri forest in the Gongga Mountains were monthly measured during the growing season. Seasonal estimates of LAI were obtained from our previous work. A conceptual model was used to predict seasonal NPP of the fir forest. Seasonal mean δ13C and Nmass and climatic variables were used as inputs. The δ13C across 1-7-year-old needles increased from May to September associated with decreasing SLA and increasing Narea. There were no significant differences in seasonal starch concentration. With increasing litterfall and decreasing LAI, seasonal mean Nmass increased, while the δ13C varied little. The simulated NPP increased with increasing litterfall and related traits of Nmass and Narea. Our data generally supported the hypotheses. The results also suggest that in the forest with relatively moist and cloudy environment, the largest fraction of annual carbon gain may occur in the early part of the growing season when higher litterfall results in higher Nmass of canopy leaves. © 2010 The Ecological Society of Japan.
Wang J.,Beijing Regional Climate Center |
He L.,Tianjin Climate Center |
Zhang X.,Harbin Meteorological Bureau
Dili Xuebao/Acta Geographica Sinica | Year: 2015
Using daily snowfall observations (1961-2012) of 227 meteorological observation stations which are treated by a series of climatic statistical methods, analysis is performed on the temporal and spatial characteristics of winter snowfall in the agri-pasture transitional zone of North China and its relations with circulation factors. The result shows that the high value center of snowfall is located in the northeast of Inner Mongolia in early winter, and then it moves to the southern part of North China at the end of winter and the beginning of spring. The periods of the 1960s and 1970s witnessed more snowfalls at all levels than normal, with high value centers moving eastward from West Inner Mongolia (in the 1960s) to most parts of Hebei and Shanxi provinces (in the 1970s). Since the 2000s, heavy snowfalls across North China have been the most significant in the north of Shanxi and Hebei provinces, with Hulunbuir coming next. Regarding variations of snowfall frequencies, there is a decline in the frequency of heavy snowfalls in different regions, with the most significant decrease occurring in Hebei province and the south of Shanxi province (named as the VI region in this paper). During the period with fewer snowfalls in North China (in the 1980s and 1990s), vapor transport was weak, moving from northwest to southeast; whereas during the years of strong vapor transport, the water transport in the past decade moved from southeast to northwest. The inter-decadal snowfall has a negative correlation with the air temperature and Arctic Oscillation (AO) index, whereas the snowfall at moderate and high levels is positively correlated with the air temperature and AO index in high latitude areas like the Greater Hinggan and Taihang Mountains in northeastern Inner Mongolia. © 2015, Science Press. All right reserved.
Li M.,Tianjin Climate Center |
Cao J.,Tianjin Climate Center |
Guo J.,Tianjin Climate Center |
Niu J.,Tianjin University |
Xiong M.,Tianjin Climate Center
Meteorological Applications | Year: 2016
The present paper concerns the impact of climate on building heating energy consumption for different types of energy in Tianjin, a large city in northern China. The results show that heating energy consumption is dominantly related to dry bulb temperature (DBT), but the impacts vary with energy types and time scales (day, month or year). DBT can explain 97.7% of the coal consumption at different time scales and 83.0–89.7% of the natural gas consumption. DBT can also account for 25% of the daily and monthly heating electricity consumption and 89% of the annual heating electricity consumption. These results suggest that different measures for building energy conservation should be taken because of the differing climate impacts for different energy types. Especially, likely increase in temperature in the future should be considered to improve the energy efficiency of buildings. In addition, different models should be used to predict building energy consumption at different time scales. This would be helpful for energy policy makers and energy providers for adjusting energy use strategies. © 2015 Royal Meteorological Society
Si P.,Tianjin Meteorological Information Center |
Ren Y.,Tianjin Climate Center |
Liang D.,Tianjin Climate Center |
Lin B.,Xiamen Meteorological Bureau
Journal of Geographical Sciences | Year: 2012
Based on China homogenized land surface air temperature and the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) Atmospheric Model Intercomparison Project (AMIP)-II Reanalysis data (R-2), the main contributors to surface air temperature increase in Southeast China were investigated by comparing trends of urban and rural temperature series, as well as observed and R-2 data, covering two periods of 1954-2005 and 1979-2005. Results from urban-rural comparison indicate that urban heat island (UHI) effects on regional annual and autumn minimum temperature increases account for 10. 5% and 12. 0% since 1954, but with smaller warming attribution of 6. 2% and 10. 6% since 1979. The results by comparing observations with R-2 surface temperature data suggest that land use change accounts for 32. 9% and 28. 8% in regional annual and autumn minimum temperature increases since 1979. Accordingly, the influence of land use change on regional temperature increase in Southeast China is much more noticeable during the last 30 years. However, it indicates that UHI effect, overwhelmed by the warming change of background climate, does not play a significant role in regional warming over Southeast China during the last 50 years. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.