Study on Temperature Disaster Indicators of Passion Fruit in Southwest Fujian, China

In China, meteorological forecasting relies on meteorological data obtained from regional and national stations. However, there were discrepancies between the data collected from the meteorological station at the passion fruit growing base and the data from regional and national stations. Consequently, the high and low temperature disaster indicators determined by the meteorological station at the passion fruit growing base cannot be applied to meteorological forecasting. To address this issue and facilitate the monitoring and early warning of high and low temperature disasters in passion fruit cultivation in Fujian, China, we used multi-source hourly temperature data (including the data from meteorological observation stations in passion fruit growing bases, the nearest regional stations, and national surface conventional meteorological observation stations) in three cities in southwestern Fujian (Longyan, Sanming, and Zhangzhou) spanning the years 2020 to 2022. By employing comprehensive statistical analysis methods (0.5 interval division and Cumulative frequency), we identified that passion fruit in southwestern Fujian was susceptible to high temperature disasters during the blooming-fruiting period, as well as low temperature disasters during the sprouting period. Consequently, we developed high and low temperature disaster indicators based on data from regional and national stations for different phenological periods of passion fruit in this region.

The Spatial-Temporal Characteristics of Meteorological Disasters in the Southwest Region of Zhejiang Province during 1953-2022

Meteorological disasters are some of the most serious and costly natural disasters, which have larger effects on economic and social activity. Liuchun Lake is an ecotourism area in the southwest region of Zhejiang province, where also has experienced meteorological disasters including rainstorm and cold wave. Understanding the temporal-spatial characteristics of meteorological disasters is important for the local tourism and economic development. Based on the daily temperature and precipitation from 18 meteorological stations in the southwest of Zhejiang province during 1953-2022 and some statistical approaches, the temporal and spatial characteristics of meteorological disasters (Freezing, Rainstorm, Cold wave) are analyzed. The results indicate that 1) Rainstorm occurred frequently around the Liuchun lake, the frequency was about 8 times/a, it can also reach about 3 times/a in the other region. Freezing and cold wave (including strong cold wave and extremely cold wave) had the same spatial distribution as rainstorm, however, except for Liuchun lake, they occurred less than one time in the other regions;2) The trend of rainstorm had larger spatial difference, it increased in all the study area, but it increased more significantly around the study area than around Liuchun lake. Freezing was on the downtrend in the whole region, with 93.3% of the stations passed the 95% significant level. Cold wave also showed a declined trend, but it was insignificantly at most of the stations, only 33% of the stations passed the 90% significant level. Compared with cold wave, strong cold wave and extremely strong cold wave had weaker decline in all the regions. In general, from 1953 to 2022 rainstorm showed an increasing trend, it was the main meteorological disaster in the study area, cold wave displayed a decreasing trend, but it still occurred about 2 - 3 times/a in most regions.

The Spatial-Temporal Change of Extreme Precipitation in the Southwest Region of Zhejiang Province during 1953-2022

Based on the daily precipitation from 17 meteorological stations in the southwest of Zhejiang from 1953 to 2022, 11 extreme precipitation indices were calculated, and the temporal-spatial characteristic of extreme precipitation were analyzed. The results indicate that 1) Except for the number of consecutive dry days (CDD), all the other extreme precipitation indices had low values in the northeast of the study area and high value around Liuchun Lake;2) CDD had a decreasing trend in most part of study area, while the other indices were on the rise, especially at Suichang (SC) and Tonglu (TL) stations, the change was significant (p 0.05);3) The annual variation showed that CDD declined with the trend of 0.83 d/10a, however, all the other indices increased, especially after 2000, the increase was more obvious. In general, the extreme precipitation mount, the extreme precipitation days showed an increasing trend, drought was less likely to happen, and the possibility of heavy precipitation is less, however, at some individual station such as SC, heavy precipitation and storm is much more likely to occur.

Study on the Changes of Extreme Temperature in the Southwest of Zhejiang Province during the Period of 1953-2022

Under the background of global warming, extreme temperature occurs frequently around the globe, which has a significant and direct impact on social and economic system. Liuchun Lake is an important ecotourism scenic region in Longyou in the southwest of Zhejiang province, it is very important for the local economic development. Based on the daily mean temperature, maximum and minimum temperature from 15 stations, the 13 extreme temperature indices as defined by the Expert Team on Climate Change Detection and Indices (ETCCDI) were calculated, and the characteristics of extreme temperature in the southwest of Zhejiang province were analyzed. The results showed that: 1) The Warmest day (TXx) and Warmest night (TNx) increased at most of the stations, while the coldest day (TXn) and the coldest night (TNn) basically significantly increased at all the stations;2) The number of frost days (FD0) showed decreased trend, and all the stations passed the 99% significant level, the number of ice days (ID0) also was on downward trend, but it is not significant at all most of the stations, however, both the number of summer days (SU25) and tropical nights (TR20) were on upward trend, and all the stations passed the significant level (p < 0.1);3) Both the number of cold days (TX10P) and cold nights (TN10P) showed a declined trend, while the number of warm days (TX90P) and warm night (TN90P) had an upward trend, especially TN90P had significant increase at all the stations. This implies that the cold events declined and warm events increased in the southwest regions of Zhejiang from 1953 to 2022.

Study on Changes of Microclimate in Greenhouse of Pleurotus nebrodensis in Jizhou, Tianjin

Based on the air temperature (1.0 m and 1.5 m) every 10 minutes, ground temperature (0 cm, 10 cm and 20 cm) and air relative humidity (1.5 m) from the stations in the greenhouse, and the air temperature (1.5 m) every 10 minutes and air relative humidity (1.5 m) from the regional stations in Chutouling Town, Jizhou district of Tianjin from April 2019 to November 2020, the changes of the microclimate in the greenhouse of Pleurotus nebrodensis were studied. The results explained that 1) the heat preservation effect of the greenhouse was the best in spring, the effective accumulative temperature and active accumulated temperature in the greenhouse had increased by 203.7°C and 233.7°C, respectively, compared with that outside the greenhouse. In the sunny or cloudy days of summer, the range of temperature difference (TD) between inside and outside the greenhouse was wider, more than 90% of the TD ranged from -6.0°C to 2.9°C;2) the minimum temperature occurred later because of heat preservation effect of the greenhouse, the delay time can reach about 30 minutes in spring, it was about 20 minutes in summer and autumn, and 10 minutes in winter, however, the maximum temperature appeared earlier, it occurred 50 minutes ahead of time in spring, and it has been advanced by 20 minutes in summer and 10 minutes in autumn and winter;3) the greenhouse mainly played a role of increasing humidity, the humidity in the greenhouse basically was larger than that outside the greenhouse, except the periods of 03:10-07:20 in spring, 0:00-08:50 and 23:10-23:50 in winter;4) the temperature in the greenhouse significantly positively correlated with the temperature outside the greenhouse, the stronger correlation also appeared between the ground temperature (at the depth of 0 cm and 10 cm) in the greenhouse and the temperature inside and outside the greenhouse, however, there was a weak correlation between the ground temperature (20 cm) and the temperature inside and outside the greenhouse, this implies that the change of temperature had less impact on the ground temperature at deeper soil layers. This paper is of significance in identifying the microclimate in the Pleurotus nebrodensis greenhouse.

Identification of Convective and Stratiform Clouds Based on the Improved DBSCAN Clustering Algorithm

A convective and stratiform cloud classification method for weather radar is proposed based on the density-based spatial clustering of applications with noise(DBSCAN)algorithm.To identify convective and stratiform clouds in different developmental phases,two-dimensional(2D)and three-dimensional(3D)models are proposed by applying reflectivity factors at 0.5°and at 0.5°,1.5°,and 2.4°elevation angles,respectively.According to the thresholds of the algorithm,which include echo intensity,the echo top height of 35 dBZ(ET),density threshold,andεneighborhood,cloud clusters can be marked into four types:deep-convective cloud(DCC),shallow-convective cloud(SCC),hybrid convective-stratiform cloud(HCS),and stratiform cloud(SFC)types.Each cloud cluster type is further identified as a core area and boundary area,which can provide more abundant cloud structure information.The algorithm is verified using the volume scan data observed with new-generation S-band weather radars in Nanjing,Xuzhou,and Qingdao.The results show that cloud clusters can be intuitively identified as core and boundary points,which change in area continuously during the process of convective evolution,by the improved DBSCAN algorithm.Therefore,the occurrence and disappearance of convective weather can be estimated in advance by observing the changes of the classification.Because density thresholds are different and multiple elevations are utilized in the 3D model,the identified echo types and areas are dissimilar between the 2D and 3D models.The 3D model identifies larger convective and stratiform clouds than the 2D model.However,the developing convective clouds of small areas at lower heights cannot be identified with the 3D model because they are covered by thick stratiform clouds.In addition,the 3D model can avoid the influence of the melting layer and better suggest convective clouds in the developmental stage.