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The tableland protected region, as a major region for agriculture and habitation, plays an important role in the Loess Plateau. The information of the regional potential evapotranspiration (ET0) and its distribution on the Loess Plateau are beneficial to the reorganization in regional water cycle, control on the soil erosion and sustainable development of agriculture. Based on the meteorological data of the tableland protected regions of the Loess Plateau during 1960-2017, the spatial and temporal distribution of the ET0 and its controlling factors were analyzed by using the Penman-Monteith model, wavelet analysis, Mann-Kendall test and ArcGIS. The results are shown as follows: (1) The average ET0 of the study area is 1173.4 mm, which shows a significant increasing trend with a rate of 21.1 mm/10 a. The average ET0 in growing season is much higher than that in the non- growing season. (2) The spatial distribution of the multi-year annual average ET0 in the study area decreased from the east to the west, and the multi-year average ET0 in the western Gansu tableland is far lower than that in the eastern Shanxi tableland. (3) Over the past 58 years, the average ET0 of the whole study area, growth season and non-growth season showed a significant increasing trend, but the spatial variations are remarkable. There were 10-year, 30-year and 50-year oscillation periods in the variation of average ET0 in the study area, of which the 30-year oscillation is the main oscillation period during the past 58 years. (4) Air temperature is the most important meteorological factor controlling ET0 change in the region, but the influence of air temperature on ET0 change shows an obvious spatial difference. The lowest temperature has the most significant effect on the ET0 change of the whole study area. The changes of ET0 in the Gansu tableland and Shaanxi tableland are mainly affected by the change of average temperature. The change of maximum temperature in Shanxi tableland has significant influence on regional ET0. (5) The Pacific/North America index (PNA) and the Atlantic Multi-decadal Oscillation (AMO) are associated with the regional ET0 change, while the ET0 change of the non-growing season is related to the change of the WPI. [ABSTRACT FROM AUTHOR]

Based on in-situ observations in Qiyi Glacier during 2011-2016, and combined with the data from meteorological stations and remote sensing images (1975- 2015), this paper analyzed the glacier terminal change, spatial and temporal variations of glacier mass balance and its sensitivity to climate change. The results showed that: the terminal of Qiyi Glacier continued to retreat 235 m from 1975 to 2015, with a rate of 5.9 m/a, and the glacier area reduced by 0.13 km2 (4.5%). During 2011- 2016, the average annual mass balance of Qiyi Glacier was -476 mm w.e., the average ELA was 4941 m a.s.l., and the mass balance gradient was 2.9 mm/m. Affected by snowdrift and ice sublimation, the glacier mass balance tended to be more negative from November to March of the next year. Mass balance in April and September is dominated by precipitation, and the change with altitude showed the precipitation effect. Mass balance increased with altitude linearly from June to August, and the end of glacier melting season was delayed from early September to the end of September. The sensitivity analysis of glacier to climate change showed that, mass balance sensitivity to air temperature change was -178.7 mm w.e. ℃-1 a-1, while that to precipitation change was + 2.93 mm w.e. mm- 1 a- 1. A 61 mm increase in precipitation was required to compensate for the net mass loss induced by an air temperature increase of 1 ℃. [ABSTRACT FROM AUTHOR]

The relationship between community biomass of spring Carex and Sentinel- 2 derived vegetation indices (VIs) was analyzed using regression analysis in one of dish-shaped lakes (i.e. Changhuchi) of Poyang Lake. In addition, the effects of elevation, water level, and temperature changes on community biomass were also examined. The results showed that: ① Among the 10 commonly used VIs, Soil Adjusted Vegetation Index (SAVI) is the most appropriate VI for spring Carex biomass estimation of Changhuchi Lake from March 22ndto May 5th. The cubic polynomial parameterized by SAVI was an optimal biomass estimation model with the root mean square error of 73.91 g/m2 and the predicted coincidence of 71.90%. Spatially, the biomass of spring Carex community generally increased from the central part to lakeshore. ② On March 22nd (normally in the middle of growth) and May 5th (the end of growth), the total aboveground biomass of spring Carex grass was 1.06×105 kg and 3.28×105 kg, respectively, along with the biomass per unit area of 77.56 g/m2 and 208.44 g/m2, respectively. Our estimates were basically in line with the previously reported upper limit of 300 g/m2 in other sub-lakes within Poyang Lake. ③ The growth of spring Carex in Changhuchi Lake is jointly affected by elevation, water level and air temperature. At the end of March, the area below 13.47 m (Yellow Sea Datum) in Changhuchi Lake is generally flooded, hence with dwarf plants and less biomass accumulation. For the regions above 13.47 m, the biomass is also at a low level due to low temperature and short dormancy. As the temperature rises, the biomass of spring Carex in the whole exposed area of Changhuchi Lake gradually accumulates with larger per unit area biomass at the higher elevations. [ABSTRACT FROM AUTHOR]

The abnormal first frost date and last frost date that occur in the critical period of crop growth will cause great losses to crop yields. It is of great significance to know and grasp the changing rules of abnormal frost date index accurately in the Huaihe River Basin to ensure the stable, high and safe grain yield of China. Ground 0 cm daily minimum temperature collected at 61 meteorological stations were used to identify the first and the last frost dates. The standard deviation was used to calculate the stability of the first and the last frost dates and the probability density function was used to define abnormal first and last frost dates. Meanwhile, IDW interpolation method was adopted to reflect the stability of first and last frost dates and the frequency of abnormal frost date before and after the transition of climate state. Moreover, linear trend estimation, Mann-Kendall mutation test, sliding t- test and cumulative averaging method were employed to obtain the mutation year in temperature. And the effect of the circulation index and air temperature on the first and the last frost dates was analyzed by correlation coefficient method. The following conclusions can be drawn from the analysis above: (1) The mean temperature of Huaihe River Basin in the period 1960- 2015 showed a significant upward trend at a rate of 0.18 °C· 10 a-1 (P<0.01) and the mutation year happened in 1993. The transition of climate state promoted the postponement of the first frost date and the advancement of the last frost date. (2) The transition of climate state led to the decrease of the stability of first and last frost dates. The stability of first and last frost dates became much better with the increase of latitude and longitude. The stability of the first frost date became better with the increase of elevation. But the change of the last frost date is not significant even when the elevation increases. The stability of the last frost date is better than that of the first frost date. (3) There was a descending order among the frequency of earlier first frost date, later last frost date, special early first frost date, and special late last frost date. And after the transition of climatological state, the frequency of abnormal first and last frost days tends to decrease and be stable at 0-20%. On the whole, the frequency of abnormal first frost date is higher than that of abnormal last frost date. The impact of climate warming is greater on the first frost date than on the last frost date. (4) The spatial distribution of abnormal first and last frost dates was significantly different, the high frequency of which was observed in the 1970s and the 1960s, respectively, and the low frequency of which was found in the 2000s. Although the frequency of abnormal first and last frost dates was gradually stabilized and remained at a low level, the transition of climate promoted the increase of the frequency of special early first date in the southeast and south parts, partial early first frost date in the south, partial late last frost date in the northeast, and special late frost date in the southeast of the Huaihe River Basin respectively. (5) The smaller the polar vortex area is in September in the northern hemisphere, the later the first frost date is (R=- 0.41, P< 0.01); the smaller the polar vortex area is in February, the earlier the last frost date would be (R=0.29, P<0.01); the larger the subtropical high is in October, the later the first frost date is (R=0.39, P<0.05); the larger the subtropical high is in April, the earlier the last frost date is (R=-0.15, P>0.05). Moreover, the tendency ahead of schedule was accelerated after 1990. The result of this article is good for frost forecast services and mitigation of frost disasters. [ABSTRACT FROM AUTHOR]