Comprehensive Marine Observing Experiment Based on High-Altitude Large Unmanned Aerial Vehicle(South China Sea Experiment2020 of the “Petrel Project”)

In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models.

Spatial Distribution and Temporal Variation of the Winter Wheat Late Frost Disaster in Henan,China

The winter wheat late frost disaster（WFD） occurs mainly in the Yellow and Huaihe River area,of which Henan Province covers the most part.Henan is the major area of wheat production in China,but it is severely hit by the WFD.In this study,we construct a WFD index based on the minimum temperature and the winter wheat development period（WDP）.The WFD degrees and days at 30 agrometeorological stations in Henan Province during the period of 1981-2004 are calculated.For the large-scale temporal variation analysis of WFD,the 24-yr WDP observation series is relatively short,so it is expanded by using the relation between the turning green date of winter wheat and the 5-day running mean temperature and that between the stem elongation phase and the effective cumulative temperature above a critical value of 2.5 ℃.The WFD data are also expanded for the last 50 years and are analyzed by using the empirical orthogonal function（EOF） and the Morlet wavelet methods.Characteristics in the spatial distribution and temporal variation of WFD are revealed.The results show that the frequency of WFD is generally high,exceeding 40% in parts of Henan,and exhibits a rising trend in the period of 1970-1990.The variation trend of WFD degrees is similar to that of WFD days,and the areas with higher WFD degrees coincide the areas with more WFD days.Moreover,the WFD degree has a greater impact on the winter wheat yield than the WFD days.The areas with high WFD degrees lie in the southeast and southwest of Henan,and the areas with low WFD degrees lie in the south of the Huaihe River and parts of western Henan.Temporal variations of the first and second EOF modes of the WFD degree display 16-and quasi-22-yr periodicities,respectively.The areas of high（low） WFD frequency are distributed in the northern Henan and the southwest border of Henan（the northeast Henan and the middle part of southwest Henan）.The temporal variation of the first（second） EOF mode of WFD days exhibits a periodicity（periodicities） of quasi-4 yr（quasi-3 and quasi-6-7 yr）.

Arctic warming trends and their uncertainties based on surface temperature reconstruction under different sea ice extent scenarios

IPCC AR6 states that the neglect of recent rapid warming in the Arctic generally leads to an underestimate of global warming trends.In this study,by reconstructing the surface temperature(ST)datasets in the Arctic under different sea ice extent scenarios(Imax and Imin),we respectively evaluated the annual and seasonal warming trends and their uncertainties from 1900 to 2020.The results show that the reconstructed datasets have a good representation of the ST change trends in the Arctic.In 1900e2020,the annual warming trends in the Arctic(0.17±0.031 and 0.14±0.025℃ per decade under the Imax and Imin reconstruction,respectively)are roughly 1.6e1.8 times the global mean warming trends(0.10±0.008 and 0.09±0.008℃ per decade).While in 1979e2020,the Arctic warming trends(0.66±0.100 and 0.55±0.080℃ per decade)increase to 3.1e3.5 times of the global warming trend(0.19±0.023 and 0.18±0.023℃ per decade)for Imax and Imin,respectively,indicating that the Arctic amplification effect has been significantly enhancing in recent decades.Although the seasonal warming trends are closely related to cloud feedback mechanisms,atmospheric circulation,and ocean circulation,they are not sensitive to the different reconstruction scenarios.