Tibetan Plateau vortices (TPVs) are major rain-producing systems over the Tibetan Plateau. Some TPVs can move off the plateau under certain conditions and impact rainfall over Eastern China. Accordingly, the eastward propagation distances of the TPVs moving off the plateau (EPDs) are closely related to the areas of rainfall associated with TPVs. In this study, the moving-off TPVs during May-August of 1998–2015 are classified into two groups according to their EPDs, and the circulations and heating fields at the times when the TPVs move off the plateau (i.e. moving-off times) are investigated based on reanalysis data. The dynamic and thermodynamic conditions to the east of the Tibetan Plateau are found to significantly impact the EPDs. In the middle and lower troposphere, the zonal ranges of negative geopotential height anomalies to the east of the Tibetan Plateau are in accordance with the EPDs of the TPVs, indicating that anomalous lows play a favourable role in the eastward movement of TPVs. In addition, the anomalous highs to the northeast of the Tibetan Plateau and over Southeastern China also benefit the maintenance of cyclonic circulation to the east of the plateau. Meanwhile, in the upper troposphere, the jet stream over Northeast Asia is beneficial for divergence at 200 hPa. Accordingly, ascending motion associated with the upper-level divergence and lower-level convergence is observed, with the zonal extent corresponding well to the EPDs in the two situations. The atmospheric thermodynamic factors also show a remarkable effect on the EPDs. The TPVs move farther away when the unstable stratification and water vapour convergence extend further eastward. The heating ranges above 500 hPa coincide with the EPDs of TPVs, implying a close relationship between the heating fields and the EPDs. These results benefit prediction on EPDs and further on rainfall to the east of the Tibetan Plateau.
Abstract Tibetan Plateau vortices (TPVs) are important rainfall triggers in southwestern and eastern China after they move off the plateau. Characteristics of the moving‐off TPVs derived from two gridded data sets, the final operational global analysis data from the Global Forecasting System of National Centers for Environment Prediction (NCEP‐FNL) and the ERA‐interim data from the European Centre for Medium‐Range Weather Forecasts, are evaluated against the Yearbooks of Tibetan Plateau Vortex and Shear Line (YB). Generally, NCEP‐FNL captures more moving‐off TPVs in YB than ERA‐interim does. Both gridded data sets perform the best in capturing the TPVs in YB in May and the worst in July. Zonal propagation distances of TPVs are apparently better revealed in NCEP‐FNL than in ERA‐interim, and the performances of NCEP‐FNL and ERA‐interim in showing the meridional propagation distances and lifespans are similar. Positional deviations of TPVs in NCEP‐FNL and ERA‐interim reveal that both data sets show good skills in presenting the TPVs locations, and NCEP‐FNL generally performs better than ERA‐interim. In both gridded data sets, positional deviations of TPVs are larger before the TPVs move off the plateau than after moving off, and zonal deviations are always larger than meridional deviations. Before the TPVs move off, NCEP‐FNL shows no specific preference for the directions of positional deviations, whereas ERA‐interim tends to present further west TPVs locations relative to those in YB. After the TPVs move off, TPVs in both gridded data sets are always observed to the west and north of the TPVs in YB, which is more significant in ERA‐interim.
Establishment of meteorological disasters in Qiannan history database and application of GIS for zoning of disasters,according to the calculated index of major disaster recurrence period,The construction of Qiannan urbanization construction in meteorology disaster influence decision-making platform.Aiming at different regions of the meteorological disaster warning threshold,to obtain the automatic filtering system of regional automatic weather station data real-time elements,combined with the extraction of radar echo and numerical prediction of weather forecast index,complete system of the township and the focus of regional real-time meteorological disaster monitoring and early warning.
Using statistical data of Beijing from 1991 to 2008,temporal spatial variation characteristics of cultivated land resources in Beijing are analyzed.The driving forces of cultivated land area change are analyzed using the principal component analysis method.The results show that the area of cultivated land in Beijing has been decreasing.The yearly decreasing rate is about 2.43%.The area of cultivated land resources per capita has been decreasing.The main driving forces of cultivated land decrease in Beijing are population growth,economic development and urbanization.
Abstract To assess the recent warming on the Tibetan Plateau (TP), some tree‐ring‐based temperature reconstructions have been performed. However, most of the previous studies focused on the local or regional scale. In this study, we analyzed the recent variability of August‐September temperature using observations from 79 TP meteorological stations, and the observed records were extended back to 1,572 based on a tree‐ring maximum density network comprising 17 sites. Moreover, the future August‐September temperature scenarios on the TP are also presented using the ensemble mean of five regional climate models. The tree‐ring maximum late‐wood density network shows good capacity to reconstruct the August‐September temperature variability at the spatial scale of the whole TP (i.e., 79‐station average; r 1951–2014 = 0.80, P < 0.01). The reconstruction suggests that the instrumental epoch is the warmest interval of August‐September over the past four and a half centuries on the TP, and the decadal‐scale August‐September warming since the 1960s is unprecedented. The ensemble simulation of five regional climate models indicates that persistent August‐September warming will occur on the TP in the future. The magnitude of August‐September warming is approximately 1.56 ± 0.30°C and 3.02 ± 0.29°C over the period 2006–2049 under the Representative Concentration Pathways (RCPs) 4.5 and P8.5 scenarios, respectively. These results imply a further ecological and environmental change on the TP linked to the persistent warming in the future.
Abstract It is reported that surface warming over the Tibetan Plateau (TP) has been faster than the global average, but exactly how much faster remains controversial. This study investigates the time dependency of warming amplification over the TP using CRU_TS4.01 grid dataset during 1961–2016 with a consideration of its consistency with the global average. We find that the magnitude of warming on the TP and its consistency with the global average have been variable. Compared to the global average, the TP warming during 1983–2016 is faster than in the period of 1961–1983, and has a higher consistency with the global average in the period of 1983–2016. The TP warming has a seasonal amplification of 1.1–1.4 times than the global average during 1983–2016, while warming amplification during 1961–1983 is relatively less evident. Generally, the magnitude of warming on the TP is smaller than in the northern high‐latitudes, but larger than in the Southern Hemisphere and the Tropics. Based on current scientific understanding, the possible contribution of snow/ice‐albedo feedback may have played an important role in warming amplification on the TP since the 1980s.
Sprinkler irrigation has been widely used for winter wheat crops in the North China Plain (NCP) to maintain high crop yield and enhance water use efficiency because water resources are scarce. Determining the accurate crop evapotranspiration (ETc) and crop coefficient (Kc) of winter wheat is critical for optimizing sprinkler irrigation management. In this study, an eddy covariance system was deployed in a sprinkler irrigation field to measure the energy balance components (net radiation Rn, soil heat flux G, sensible heat H, latent heat LE) and calculate ETc and Kc. The wheat growth parameters and yield were also investigated. The results showed that the energy balance closure rate, the rate of daily (LE + H) to (Rn - G), was 0.89, indicating a sufficient energy balance closure. Seasonal total LE flux accounted for 67% of the total available energy (Rn - G). The seasonal ETc values were 434 and 396 mm during the 2019–2020 and 2020–2021 growing seasons, respectively, which are comparable to those (400–470 mm) under surface irrigation. The mean daily ETc was 0.87, 0.46, 3.24, 4.81, and 3.94 mm day−1 in the early growth, overwintering, rapid growth, middle, and late growth stages, respectively. The corresponding Kc values were 0.77, 0.47, 1.09, 1.14 and 0.70. The Kc values were close to those reported in the FAO 56 paper. The Kc is positively related to the leaf area index (LAI), and their relationship was fitted as Kc=0.87+0.14lnLAI(R2=0.96) for an LAI range of 1–7, where ln is a natural logarithm function. The measured wheat grain yield was 9100 and 9857 kg ha−1, and the water productivity (WP) was 2.07 and 2.49 kg m−3 in the two seasons, respectively. Both factors are approximately 30% higher than those (7200 kg ha−1, 1.68 kg m−3) reported by other studies. Considering the high wheat yield and comparable crop ETc, sprinkler irrigation is recommended for application on the NCP. The seasonal ETc of 400–430 mm and the obtained Kc values in this study can be used to make sprinkler irrigation scheduling for winter wheat on the NCP.
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