Abstract:
keep_len="250">To address problems including underestimation of heavy precipitation, rapid decay of synoptic systems and low computational efficiency in operational forecast of CMA-GFS V3.3, some key technologies related to physics and dynamics of the model are developed and applied.A suite of graupel-related microphysical processes is adopted in the cloud microphysics scheme to improve the forecast performance of heavy precipitation. These processes include graupel colliding with cloud water, ice crystals and snow, automatic conversions of ice crystals to graupel and snow to graupel, melting process of graupel to raindrop and sublimation process of graupel. In addition, the evaporation rate of cloud and rainwater is restricted, which can increase the liquid water content in warm areas and improve precipitation efficiency.In the convection parameterization scheme, the role of the sub-cloud environmental relative humidity to convection triggers is considered, and the unreasonable occurrence of convections in dry environment is suppressed. Also, the sensitivity of the entrainment rate of the convective updraft to the relative humidity outside the cloud is enhanced to weaken the convections in dry environment. At the same time, the quasi-equilibrium closure scheme is optimized to improve the accuracy in calculating cloud-base mass flux which is related to the convection intensity.To solve the problem of the mass loss in long time integration, a mass conservation correction method is introduced to the model dynamic framework. The method is developed to ensure the mass conservation by adjusting mass in each grid box according to different weight coefficients which are determined by the change of total atmospheric mass of the current time step relative to the previous step.In terms of computational efficiency, the two-dimensional reference profile algorithm is developed. Without losing calculation accuracy, the model integration time step is extended from 240 s to 300 s using the new profile instead of the original three-dimensional reference profile. Meanwhile, the PCSI method is adopted instead of the GCR method, which reduces the time consuming of solving Helmholtz equation. In addition, the radiation scheme and predictor-corrector algorithms are also optimized to improve the computational efficiency.Through the application of the above key technologies, the forecasting skills for weather pattern and precipitation of CMA-GFS are significantly improved. And its computational efficiency is increased by about 1/3, which meets operational time requirement for the model with 0.125° horizontal resolution. Based on the improved model and the research achievements in other aspects of the forecast system, CMA-GFS is upgraded to V4.0 with a significantly improved comprehensive performance. To address problems including underestimation of heavy precipitation, rapid decay of synoptic systems and low computational efficiency in operational forecast of CMA-GFS V3.3, some key technologies related to physics and dynamics of the model are developed and applied.A suite of graupel-related microphysical processes is adopted in the cloud microphysics scheme to improve the forecast performance of heavy precipitation. These processes include graupel colliding with cloud water, ice crystals and snow, automatic conversions of ice crystals to graupel and snow to graupel, melting process of graupel to raindrop and sublimation process of graupel. In addition, the evaporation rate of cloud and rainwater is restricted, which can increase the liquid water content in warm areas and improve precipitation efficiency.In the convection parameterization scheme, the role of the sub-cloud environmental relative humidity to convection triggers is considered, and the unreasonable occurrence of convections in dry environment is suppressed. Also, the sensitivity of the entrainment rate of the convective updraft to the relative humidity outside the cloud is enhanced to weaken the convections in dry environment. At the same time, the quasi-equilibrium closure scheme is optimized to improve the accuracy in calculating cloud-base mass flux which is related to the convection intensity.To solve the problem of the mass loss in long time integration, a mass conservation correction method is introduced to the model dynamic framework. The method is developed to ensure the mass conservation by adjusting mass in each grid box according to different weight coefficients which are determined by the change of total atmospheric mass of the current time step relative to the previous step.In terms of computational efficiency, the two-dimensional reference profile algorithm is developed. Without losing calculation accuracy, the model integration time step is extended from 240 s to 300 s using the new profile instead of the original three-dimensional reference profile. Meanwhile, the PCSI method is adopted instead of the GCR method, which reduces the time consuming of solving Helmholtz equation. In addition, the radiation scheme and predictor-corrector algorithms are also optimized to improve the computational efficiency.Through the application of the above key technologies, the forecasting skills for weather pattern and precipitation of CMA-GFS are significantly improved. And its computational efficiency is increased by about 1/3, which meets operational time requirement for the model with 0.125° horizontal resolution. Based on the improved model and the research achievements in other aspects of the forecast system, CMA-GFS is upgraded to V4.0 with a significantly improved comprehensive performance.

Abstract:
keep_len="250">Great part of China experiences hot spells in summer of 2022. In August, an extensive and intensive heat wave occurred along the Yangtze Basins, which persists nearly a month, causing serious damage and the worst summer drought, which is the second only to 2011. The persistent hot spell tends to be closely related with the anomalous activity of the Western Pacific subtropical high (WPSH). To better understand the causes, observations and reanalysis data are used to study the mechanism of anomalous activities of WPSH, the influence of tropical circulation, and the westerly long-wave trough ridge on WPSH.During summer of 2022, anomalous activity is observed in both the continental subtropical high and WPSH. In mid-late July, WPSH shifted to the west, and the continental subtropical high over the Iranian Plateau expanded to the east, resulting in the formation of a high-pressure belt and heat wave in the middle and the lower reaches of the Yangtze. In August, the continental subtropical weakens, and WPSH extended westward to 90°E, 40 longitudinal degrees to the west of its climatic position, which plays an important role in the persistent heat wave.The steady westward march of WPSH is discussed based on the investigation of both the anomalies of tropical circulation and systems in the westerlies. In August, the intertropical convergence zone over the region from the Western Pacific to South China Sea is intensified, associated with vigorous convection, and three typhoons or tropical cyclones. The remarkable local Hadley circulation appeared over the South China Sea, which supported the maintenance of WPSH to the west of 115°E.The flow pattern in the westerly zone also shows some particular features. From mean geopotential height field at 500 hPa for the hot spell, a pattern of "two ridges with a trough in between" maintains over the Eurasian region. The Okhotsk ridge in the east almost merges with WPSH into a stable high pressure dam. The Rossby wave activity indicates the ridge over the Ural area in the west consistently conveying energy southeastward, which also plays an important role in the strengthening and maintenance of the subtropical high. Great part of China experiences hot spells in summer of 2022. In August, an extensive and intensive heat wave occurred along the Yangtze Basins, which persists nearly a month, causing serious damage and the worst summer drought, which is the second only to 2011. The persistent hot spell tends to be closely related with the anomalous activity of the Western Pacific subtropical high (WPSH). To better understand the causes, observations and reanalysis data are used to study the mechanism of anomalous activities of WPSH, the influence of tropical circulation, and the westerly long-wave trough ridge on WPSH.During summer of 2022, anomalous activity is observed in both the continental subtropical high and WPSH. In mid-late July, WPSH shifted to the west, and the continental subtropical high over the Iranian Plateau expanded to the east, resulting in the formation of a high-pressure belt and heat wave in the middle and the lower reaches of the Yangtze. In August, the continental subtropical weakens, and WPSH extended westward to 90°E, 40 longitudinal degrees to the west of its climatic position, which plays an important role in the persistent heat wave.The steady westward march of WPSH is discussed based on the investigation of both the anomalies of tropical circulation and systems in the westerlies. In August, the intertropical convergence zone over the region from the Western Pacific to South China Sea is intensified, associated with vigorous convection, and three typhoons or tropical cyclones. The remarkable local Hadley circulation appeared over the South China Sea, which supported the maintenance of WPSH to the west of 115°E.The flow pattern in the westerly zone also shows some particular features. From mean geopotential height field at 500 hPa for the hot spell, a pattern of "two ridges with a trough in between" maintains over the Eurasian region. The Okhotsk ridge in the east almost merges with WPSH into a stable high pressure dam. The Rossby wave activity indicates the ridge over the Ural area in the west consistently conveying energy southeastward, which also plays an important role in the strengthening and maintenance of the subtropical high.

Abstract:
keep_len="250">To better understand the influence of aerosols on micro-properties of clouds and to facilitate weather modification experiments including the analysis of various materials' seeding effect on clouds and precipitation, Beijing Weather Modification Center has taken a decisive step forward by constructing an advanced facility known as Beijing aerosol and cloud interaction chamber (BACIC) in suburban Pinggu district. Boasting an impressive volume of 70 m³, BACIC is not only the largest of its kind in operation in China, but also a testament to the scale of the country's commitment to this sphere of atmospheric science. The enormity of the chamber's capacity facilitates the performance of a broad spectrum of investigations, thus enhancing the comprehensiveness and reliability of the results obtained.Inside BACIC, advanced instrumentation allows for the meticulous measurement and control of temperature, relative humidity, and background aerosol concentration. During 2019-2021, the chamber's capabilities extend further, as demonstrated by successful tests of its ability to create liquid and mixed-phase clouds. These attributes, combined with its capacity to control the cloud droplet size distribution as proved by comparative experiments involving changes in expansion rate and aerosol number concentration, solidify BACIC's standing as a prime location for warm cloud experimentation. The chamber has also been utilized to investigate effects of anthropogenic pollution over North China Plain (NCP) on cloud microphysics. Using ambient air and manipulating the expansion rate, a significant correlation is discovered between such pollution and the size distribution of cloud droplets. Interestingly, while an increase in aerosol leads to higher number of cloud droplets, it also causes a decrease in droplet size, typically within the range of 5-8 μm. Furthermore, an increase in aerosol number concentration leads to a decrease in the activation rate of aerosols into cloud droplets. This activation rate is around 10% for aerosol concentrations less than 5000 cm^-3, and remains stable even when the aerosol concentration increases to 10000 cm^-3.BACIC is also proved useful in conducting warm cloud expansion experiments involving different hygroscopic materials. It shows that the distribution of submicron (less than 1 μm) hygroscopic catalysts in a polluted environment leads to narrowing of the cloud droplet spectrum. It suggests that for the purpose of artificially reducing warm clouds or fog, it is recommended to use larger particle sizes. The results obtained from these diverse series of experiments have significantly contributed to theoretical knowledge and provide practical guidance for the ongoing development of artificial weather modification techniques. To better understand the influence of aerosols on micro-properties of clouds and to facilitate weather modification experiments including the analysis of various materials' seeding effect on clouds and precipitation, Beijing Weather Modification Center has taken a decisive step forward by constructing an advanced facility known as Beijing aerosol and cloud interaction chamber (BACIC) in suburban Pinggu district. Boasting an impressive volume of 70 m³, BACIC is not only the largest of its kind in operation in China, but also a testament to the scale of the country's commitment to this sphere of atmospheric science. The enormity of the chamber's capacity facilitates the performance of a broad spectrum of investigations, thus enhancing the comprehensiveness and reliability of the results obtained.Inside BACIC, advanced instrumentation allows for the meticulous measurement and control of temperature, relative humidity, and background aerosol concentration. During 2019-2021, the chamber's capabilities extend further, as demonstrated by successful tests of its ability to create liquid and mixed-phase clouds. These attributes, combined with its capacity to control the cloud droplet size distribution as proved by comparative experiments involving changes in expansion rate and aerosol number concentration, solidify BACIC's standing as a prime location for warm cloud experimentation. The chamber has also been utilized to investigate effects of anthropogenic pollution over North China Plain (NCP) on cloud microphysics. Using ambient air and manipulating the expansion rate, a significant correlation is discovered between such pollution and the size distribution of cloud droplets. Interestingly, while an increase in aerosol leads to higher number of cloud droplets, it also causes a decrease in droplet size, typically within the range of 5-8 μm. Furthermore, an increase in aerosol number concentration leads to a decrease in the activation rate of aerosols into cloud droplets. This activation rate is around 10% for aerosol concentrations less than 5000 cm^-3, and remains stable even when the aerosol concentration increases to 10000 cm^-3.BACIC is also proved useful in conducting warm cloud expansion experiments involving different hygroscopic materials. It shows that the distribution of submicron (less than 1 μm) hygroscopic catalysts in a polluted environment leads to narrowing of the cloud droplet spectrum. It suggests that for the purpose of artificially reducing warm clouds or fog, it is recommended to use larger particle sizes. The results obtained from these diverse series of experiments have significantly contributed to theoretical knowledge and provide practical guidance for the ongoing development of artificial weather modification techniques.

Abstract:
keep_len="250">To study the impact of global warming on the yield and quality of winter wheat, field scientific experiments are carried out at Xuzhou Agro-meteorological Station of Jiangsu from 2017 to 2022. There are four sowing dates each year with different temperature during the growing season of winter wheat, while the winter wheat variety, soil physical and chemical properties, and agriculture measures are all the same. Therefore, the yield structure and quality of winter wheat are mainly influenced by climate change. It shows that the average temperature increases 0.1℃ to 1.7℃ during the growing season of winter wheat at different sowing dates during 5-year field experiments. The increasing temperature has an impact on the yield structure, and there is a significant negative influence on the number of grains per ear of winter wheat, with a correlation coefficient of -0.49 (P<0.05). The number of grains per ear of winter wheat decreases by 14.7% for 1℃ increase, resulting in a reduction in yield. The increasing temperature also has a negative impact on grain quality, the correlation coefficient between temperature and grain protein content reaches -0.72 (P<0.01), and the correlation coefficient with fat content is -0.52 (P<0.05). In addition, the increasing temperature has a negative impact on 14 of 16 amino acids, especially on the content of aspartic acid and arginine. Overall, climate change could decrease the number of grains per ear of winter wheat, and decrease significantly in protein and fat content in grains. The main cause is that the minimum temperature at night increases due to global warming, strengthening the respiration of winter wheat, which is not conducive to its assimilation and organic matter accumulation. At the same time, climate warming leads to an increase in high-temperature damage during the flowering to maturity period of winter wheat, affecting its physiological and biochemical processes, especially limiting the absorption and synthesis of nutrients of winter wheat. To study the impact of global warming on the yield and quality of winter wheat, field scientific experiments are carried out at Xuzhou Agro-meteorological Station of Jiangsu from 2017 to 2022. There are four sowing dates each year with different temperature during the growing season of winter wheat, while the winter wheat variety, soil physical and chemical properties, and agriculture measures are all the same. Therefore, the yield structure and quality of winter wheat are mainly influenced by climate change. It shows that the average temperature increases 0.1℃ to 1.7℃ during the growing season of winter wheat at different sowing dates during 5-year field experiments. The increasing temperature has an impact on the yield structure, and there is a significant negative influence on the number of grains per ear of winter wheat, with a correlation coefficient of -0.49 (P<0.05). The number of grains per ear of winter wheat decreases by 14.7% for 1℃ increase, resulting in a reduction in yield. The increasing temperature also has a negative impact on grain quality, the correlation coefficient between temperature and grain protein content reaches -0.72 (P<0.01), and the correlation coefficient with fat content is -0.52 (P<0.05). In addition, the increasing temperature has a negative impact on 14 of 16 amino acids, especially on the content of aspartic acid and arginine. Overall, climate change could decrease the number of grains per ear of winter wheat, and decrease significantly in protein and fat content in grains. The main cause is that the minimum temperature at night increases due to global warming, strengthening the respiration of winter wheat, which is not conducive to its assimilation and organic matter accumulation. At the same time, climate warming leads to an increase in high-temperature damage during the flowering to maturity period of winter wheat, affecting its physiological and biochemical processes, especially limiting the absorption and synthesis of nutrients of winter wheat.

Abstract:
keep_len="250">Precipitation is particularly important for the earth's climate system. Understanding the structural characteristics, microphysical processes and drop size distribution (DSD) of precipitation is very important for quantitative precipitation estimation with radar and improving microphysical parameter schemes of numerical weather prediction models. With the launch of the Second Tibet Plateau Scientific Expedition and Research(STEPS), Chinese Academy of Meteorological Sciences has deployed Ka-band cloud radar (KaCR), X-band dual polarization phased array radar (X-PAR), disdrometer, micro rain radar (MRR) and other detection equipment in Mêdog, filling the gap of cloud and precipitation observation in this area and provides data basis for studying the physical characteristics of clouds and precipitation. Mêdog is located at Yarlung Zangbo Grand Canyon, the entrance of the water vapor channel in southeastern Tibet. Influenced by the warm and humid airflow brought by the Indian Ocean monsoon, the precipitation of Mêdog during the monsoon period exceeds 60% of the annual precipitation. MRR is a low-cost, miniaturized vertical directional Doppler rain radar that can more accurately analyze the vertical structural changes of precipitation. Based on observation of the rain gauge, MRR and disdrometer set up at Mêdog National Climate Observatory from 1 June to 30 September in 2021, the consistency of different instruments is studied. The observed rainfall is classified into convective, stratiform and shallow precipitation types, and the average vertical distribution characteristics of different precipitation types are studied from the aspects of raindrop size distribution, falling speed, rain rate, liquid water content and radar reflectivity. The results show that the measurement of rain gauge, MRR and distrometer are highly consistent. The correlation coefficient of daily rainfall is above 0.89, and the highest correlation coefficient between MRR and rain gauge is 0.96. However, MRR overestimates weak precipitation and underestimate strong precipitation. There are significant differences in the vertical structure of different precipitation types during the monsoon period of Mêdog. Values of each microphysical quantity of convective precipitation are larger. The collision and growth process of raindrop is significant during the falling process below 3 km height, and the raindrop number concentration increases rapidly. There is significant updraft at a height of 1-2 km. The echo intensity of stratiform cloud precipitation is weak below the height of the melting layer. The radar reflectivity, rain rate and liquid water content increase with altitude decrease, the falling speed of raindrops remains basically stable in the vertical direction. The concentration of medium-sized raindrops remains constant with height, and the evaporation, fragmentation, and coalescence processes are in a relatively balance. Values of each microphysical quantity of shallow precipitation are relatively small but vary significantly with height and show negative slops in the vertical direction. The shallow precipitation is dominated by the collision process of raindrops. Precipitation is particularly important for the earth's climate system. Understanding the structural characteristics, microphysical processes and drop size distribution (DSD) of precipitation is very important for quantitative precipitation estimation with radar and improving microphysical parameter schemes of numerical weather prediction models. With the launch of the Second Tibet Plateau Scientific Expedition and Research(STEPS), Chinese Academy of Meteorological Sciences has deployed Ka-band cloud radar (KaCR), X-band dual polarization phased array radar (X-PAR), disdrometer, micro rain radar (MRR) and other detection equipment in Mêdog, filling the gap of cloud and precipitation observation in this area and provides data basis for studying the physical characteristics of clouds and precipitation. Mêdog is located at Yarlung Zangbo Grand Canyon, the entrance of the water vapor channel in southeastern Tibet. Influenced by the warm and humid airflow brought by the Indian Ocean monsoon, the precipitation of Mêdog during the monsoon period exceeds 60% of the annual precipitation. MRR is a low-cost, miniaturized vertical directional Doppler rain radar that can more accurately analyze the vertical structural changes of precipitation. Based on observation of the rain gauge, MRR and disdrometer set up at Mêdog National Climate Observatory from 1 June to 30 September in 2021, the consistency of different instruments is studied. The observed rainfall is classified into convective, stratiform and shallow precipitation types, and the average vertical distribution characteristics of different precipitation types are studied from the aspects of raindrop size distribution, falling speed, rain rate, liquid water content and radar reflectivity. The results show that the measurement of rain gauge, MRR and distrometer are highly consistent. The correlation coefficient of daily rainfall is above 0.89, and the highest correlation coefficient between MRR and rain gauge is 0.96. However, MRR overestimates weak precipitation and underestimate strong precipitation. There are significant differences in the vertical structure of different precipitation types during the monsoon period of Mêdog. Values of each microphysical quantity of convective precipitation are larger. The collision and growth process of raindrop is significant during the falling process below 3 km height, and the raindrop number concentration increases rapidly. There is significant updraft at a height of 1-2 km. The echo intensity of stratiform cloud precipitation is weak below the height of the melting layer. The radar reflectivity, rain rate and liquid water content increase with altitude decrease, the falling speed of raindrops remains basically stable in the vertical direction. The concentration of medium-sized raindrops remains constant with height, and the evaporation, fragmentation, and coalescence processes are in a relatively balance. Values of each microphysical quantity of shallow precipitation are relatively small but vary significantly with height and show negative slops in the vertical direction. The shallow precipitation is dominated by the collision process of raindrops.

Abstract:
keep_len="250">Based on daily precipitation and temperature data as well as population, gross domestic product (GDP), land use and land cover change (LUCC), night lighting remote sensing data of 46 meteorological stations in Sichuan and Chongqing Region from 1971 to 2020, 21 extreme climate indices are calculated using RClimDex software, and the interannual variation trends of these indices are analyzed using linear trend method. The Mann-Kendall nonparametric method is used to test the significance levels of all indices. These meteorological stations are categorified to further investigate the impact of urbanization on extreme climate indices, especially the impact of urbanization on extreme climate events in Sichuan and Chongqing. It's found that the monthly maximum value of daily maximum temperature (TXx), maximum value of daily minimum temperature (TNx), minimum value of daily maximum temperature (TXn), minimum value of daily minimum temperature (TNn), summer days (SU25), occurrence of hot nights(TR20), warm nights (TN90P) and warm days (TX90P) all show an increasing trend in the last 50 years, while the frost days (FD0), cold nights (TN10P) and cold days (TX10P) show a decreasing trend, and the changes are all significant. The annual total precipitation in wet days (PRCPTOT), very heavy precipitation days (R25mm), very wet days (R95P), extremely wet days (R99P) and simple precipitation intensity index (SDII), which represent the extreme precipitation and the intensity of extreme precipitation, all show an increasing trend, indicating that the extreme high temperature and extreme precipitation in Sichuan and Chongqing Region have been increasing. The extreme indices show an increasing trend in all three types of meteorological sites. The increasing trend of TXx, TNx, TR20, TX90P and daily temperature range (DTR) are most obvious in urban stations, and FD0, TN10P, TX10P and DTR are most obvious in rural stations. Urbanization has basically no effects on TXx and TN90P at rural-urban sites, but has a greater effect on the monthly TXn, TNn, FD0, TR20 and DTR at rural and urban sites, as well as the number of TN10P and TN90P at urban sites. In Sichuan and Chongqing Region, among the rural sites, all indices show a significant increasing trend except for the monthly maximum 1-day precipitation (RX1DAY), monthly maximum 5-day precipitation (RX5DAY) and consecutive wet days (CWD), which show a non-significant decreasing trend. The influence of urbanization causes a decreasing trend in the number of heavy precipitation days (R10mm), R25mm, RX1DAY, RX5DAY, R95P and PRCPTOT in urban-rural and urban sites, and causes an increasing trend in SDII and CWD. The urbanization effects contribute 100.00% to R10mm, RX1DAY, RX5DAY, R95P and PRCPTOT for both urban-rural and urban sites. Based on daily precipitation and temperature data as well as population, gross domestic product (GDP), land use and land cover change (LUCC), night lighting remote sensing data of 46 meteorological stations in Sichuan and Chongqing Region from 1971 to 2020, 21 extreme climate indices are calculated using RClimDex software, and the interannual variation trends of these indices are analyzed using linear trend method. The Mann-Kendall nonparametric method is used to test the significance levels of all indices. These meteorological stations are categorified to further investigate the impact of urbanization on extreme climate indices, especially the impact of urbanization on extreme climate events in Sichuan and Chongqing. It's found that the monthly maximum value of daily maximum temperature (TXx), maximum value of daily minimum temperature (TNx), minimum value of daily maximum temperature (TXn), minimum value of daily minimum temperature (TNn), summer days (SU25), occurrence of hot nights(TR20), warm nights (TN90P) and warm days (TX90P) all show an increasing trend in the last 50 years, while the frost days (FD0), cold nights (TN10P) and cold days (TX10P) show a decreasing trend, and the changes are all significant. The annual total precipitation in wet days (PRCPTOT), very heavy precipitation days (R25mm), very wet days (R95P), extremely wet days (R99P) and simple precipitation intensity index (SDII), which represent the extreme precipitation and the intensity of extreme precipitation, all show an increasing trend, indicating that the extreme high temperature and extreme precipitation in Sichuan and Chongqing Region have been increasing. The extreme indices show an increasing trend in all three types of meteorological sites. The increasing trend of TXx, TNx, TR20, TX90P and daily temperature range (DTR) are most obvious in urban stations, and FD0, TN10P, TX10P and DTR are most obvious in rural stations. Urbanization has basically no effects on TXx and TN90P at rural-urban sites, but has a greater effect on the monthly TXn, TNn, FD0, TR20 and DTR at rural and urban sites, as well as the number of TN10P and TN90P at urban sites. In Sichuan and Chongqing Region, among the rural sites, all indices show a significant increasing trend except for the monthly maximum 1-day precipitation (RX1DAY), monthly maximum 5-day precipitation (RX5DAY) and consecutive wet days (CWD), which show a non-significant decreasing trend. The influence of urbanization causes a decreasing trend in the number of heavy precipitation days (R10mm), R25mm, RX1DAY, RX5DAY, R95P and PRCPTOT in urban-rural and urban sites, and causes an increasing trend in SDII and CWD. The urbanization effects contribute 100.00% to R10mm, RX1DAY, RX5DAY, R95P and PRCPTOT for both urban-rural and urban sites.

Abstract:
keep_len="250">Typhoon In-fa lands on the coast of Zhoushan, Zhejiang Province on 25 July 2021, bringing severe wind and rain to the coastal areas for a long time. Before landing, it maintains in the sea, east of Ryukyu Islands and then suddenly turns northward. The official subjective and numerical model forecasts both produce serious errors on the landing time and location, which has a certain impact on the decision of disaster prevention.Using the best track data of China Meteorological Administration (CMA) and the water vapor channel data of FY-4A satellite cloud image, the characteristics of Typhoon In-fa, especially the causes of its stagnation and northerly bend are investigated. Deterministic model forecast results from the regional mesoscale typhoon numerical forecast system (CMA-TYM), the fine-grid numerical forecast product of European Center for Medium-range Weather Forecasts (ECMWF) and National Center for Environmental Prediction Center (NCEP), and ECMWF ensemble forecast data are also analyzed. The fifth generation global climate reanalysis data set ERA5 is used for the analysis of the real situation field and physical quantity field. The center of the upper-tropospheric cold low (UTCL) is determined by referring to the water vapor channel of the satellite cloud image and the horizontal flow field is obtained according to the wind field data of ERA5. The center of the cyclonic circulation over 200 hPa is set as the center of UTCL.Through FY-4A water vapor cloud image, it is found that in the stagnation stage of Typhoon In-fa, there is a UTCL system on the north side. By analyzing the vertical distribution of circulation situation field, steering flow, and relative vorticity, it is found that the position of the subtropical high system is to the east and north, and typhoon guiding effect on the typhoon is weak. Therefore, the main weather systems that affect the change of its track are the UTCL and westerly trough system in the upper troposphere. There are also differences in the interaction between UTCL and typhoon at different intensities and distances. By analyzing the deterministic and ensemble prediction of ECMWF and CMA-TYM models, it is found that the prediction errors and deviations of UTCL are important reasons for the track predictions. There are still large errors and uncertainties of ensemble prediction in the prediction of UTCL, especially for long lead time forecast products. The UTCL slows down Typhoon In-fa and makes it bend to the left, which indirectly leads to the northerly bend of Typhoon In-fa.In the future, it is necessary to further study the influence of UTCL on typhoon track and intensity, pay more attention to the prediction performance of UTCL, and carry out the prediction and inspection of UTCL in the model, so as to support the interpretation and improvement of the model product. Typhoon In-fa lands on the coast of Zhoushan, Zhejiang Province on 25 July 2021, bringing severe wind and rain to the coastal areas for a long time. Before landing, it maintains in the sea, east of Ryukyu Islands and then suddenly turns northward. The official subjective and numerical model forecasts both produce serious errors on the landing time and location, which has a certain impact on the decision of disaster prevention.Using the best track data of China Meteorological Administration (CMA) and the water vapor channel data of FY-4A satellite cloud image, the characteristics of Typhoon In-fa, especially the causes of its stagnation and northerly bend are investigated. Deterministic model forecast results from the regional mesoscale typhoon numerical forecast system (CMA-TYM), the fine-grid numerical forecast product of European Center for Medium-range Weather Forecasts (ECMWF) and National Center for Environmental Prediction Center (NCEP), and ECMWF ensemble forecast data are also analyzed. The fifth generation global climate reanalysis data set ERA5 is used for the analysis of the real situation field and physical quantity field. The center of the upper-tropospheric cold low (UTCL) is determined by referring to the water vapor channel of the satellite cloud image and the horizontal flow field is obtained according to the wind field data of ERA5. The center of the cyclonic circulation over 200 hPa is set as the center of UTCL.Through FY-4A water vapor cloud image, it is found that in the stagnation stage of Typhoon In-fa, there is a UTCL system on the north side. By analyzing the vertical distribution of circulation situation field, steering flow, and relative vorticity, it is found that the position of the subtropical high system is to the east and north, and typhoon guiding effect on the typhoon is weak. Therefore, the main weather systems that affect the change of its track are the UTCL and westerly trough system in the upper troposphere. There are also differences in the interaction between UTCL and typhoon at different intensities and distances. By analyzing the deterministic and ensemble prediction of ECMWF and CMA-TYM models, it is found that the prediction errors and deviations of UTCL are important reasons for the track predictions. There are still large errors and uncertainties of ensemble prediction in the prediction of UTCL, especially for long lead time forecast products. The UTCL slows down Typhoon In-fa and makes it bend to the left, which indirectly leads to the northerly bend of Typhoon In-fa.In the future, it is necessary to further study the influence of UTCL on typhoon track and intensity, pay more attention to the prediction performance of UTCL, and carry out the prediction and inspection of UTCL in the model, so as to support the interpretation and improvement of the model product.

Abstract:
keep_len="250">Tall object not only has a high probability of being struck by downward lightning, but also is easy to trigger upward lightning. Comparing with 2D optical observation, reconstructed 3D observation by dual-station optical observation can better reflect the real characteristics of the lightning channel. Based on the synchronous dual-station optical observations from the Tall-Object Lightning Observatory in Guangzhou (TOLOG), an upward lightning triggered by a nearby positive cloud-to-ground (CG) flash at Guangzhou Tower is investigated, and 2D and 3D development characteristics of the upward leader are compared.The result shows that the length of 3D channel is 5.4 km, which is 1.5 times of 2D channel. 3D channel is developed at a height of more than 4.6 km in the vertical direction and about 800 m in the horizontal direction. 2D speed ranges from 1.8×10⁴ to 4.5×10⁵ m·s^-1, with an average of 1.8×10⁵ m·s^-1. 3D speed ranges from 3.8×10⁴ to 7.2×10⁵ m·s^-1, with an average value of 2.8×10⁵ m·s^-1. Within 10 ms after the leader initiation, 3D and 2D speeds show roughly the same trend. After 10 ms, 2D rate decreases significantly and changes little over time, while 3D speed shows an obvious irregular fluctuation with time. The ratio of 3D speed and 2D speed ranges from 1 to 4.7, with an average of 1.5. The ratio remains stable at 1-2 for the first 10 ms after leader initiation and then shows irregular fluctuations with time. In fact, due to the change of horizontal development direction of the channel 10 ms after the leader initiation, the distance between the channel and the station-1 increases rapidly, leading to increasing speed difference between 3D and 2D observations. The cause for the fluctuation of 3D speed and 2D speed ratio is that the angle between the development direction of the channel and the sight direction of the observation station changes greatly. The results of 2D and 3D vary greatly at a certain stage of upward leader development, which further proves the importance of analyzing 3D development characteristics of lightning. Tall object not only has a high probability of being struck by downward lightning, but also is easy to trigger upward lightning. Comparing with 2D optical observation, reconstructed 3D observation by dual-station optical observation can better reflect the real characteristics of the lightning channel. Based on the synchronous dual-station optical observations from the Tall-Object Lightning Observatory in Guangzhou (TOLOG), an upward lightning triggered by a nearby positive cloud-to-ground (CG) flash at Guangzhou Tower is investigated, and 2D and 3D development characteristics of the upward leader are compared.The result shows that the length of 3D channel is 5.4 km, which is 1.5 times of 2D channel. 3D channel is developed at a height of more than 4.6 km in the vertical direction and about 800 m in the horizontal direction. 2D speed ranges from 1.8×10⁴ to 4.5×10⁵ m·s^-1, with an average of 1.8×10⁵ m·s^-1. 3D speed ranges from 3.8×10⁴ to 7.2×10⁵ m·s^-1, with an average value of 2.8×10⁵ m·s^-1. Within 10 ms after the leader initiation, 3D and 2D speeds show roughly the same trend. After 10 ms, 2D rate decreases significantly and changes little over time, while 3D speed shows an obvious irregular fluctuation with time. The ratio of 3D speed and 2D speed ranges from 1 to 4.7, with an average of 1.5. The ratio remains stable at 1-2 for the first 10 ms after leader initiation and then shows irregular fluctuations with time. In fact, due to the change of horizontal development direction of the channel 10 ms after the leader initiation, the distance between the channel and the station-1 increases rapidly, leading to increasing speed difference between 3D and 2D observations. The cause for the fluctuation of 3D speed and 2D speed ratio is that the angle between the development direction of the channel and the sight direction of the observation station changes greatly. The results of 2D and 3D vary greatly at a certain stage of upward leader development, which further proves the importance of analyzing 3D development characteristics of lightning.

Abstract:
keep_len="250">Lightning activity poses threats to human life and property safety. A large volume studies indicate that aerosol plays a significant role in lightning activity. To explore the effect of different types of aerosols on lightning activity in the Yangtze River Delta and its surrounding areas, cloud-to-ground (CG) lightning location data and aerosol optical depth from reanalysis dataset is analyzed in the target area(27.5°-35°N, 115°-122.5°E) during 2015-2021.The spatial distribution of aerosol optical depth (AOD) with CG lightning condition and without CG lightning condition, and monthly variation of aerosol concentration under two conditions are investigated. All the grids in the target region show that sulfate AOD is higher, while dust AOD is lower with CG lightning. In summer there are little differences between the AOD with CG lightning and without CG lightning conditions. In other months, more sulfate aerosol and less dust aerosol are found with CG lightning condition.The spatial distribution of CG lightning density difference under higher and lower AOD conditions is given. The results show that when the sulfate AOD is high, the CG lightning density of most grids is higher. The CG lightning density is significantly lower when the dust AOD is high.The correlation coefficient between CG lightning density and the AOD for different types of aerosols is calculated for the months when CG lightning is active. When the concentration of sulfate aerosol is low, the correlation coefficient between sulfate AOD and CG lightning density is significant. When the sulfate aerosol concentration exceeds a certain threshold, there is no significant correlation between CG lightning density and sulfate AOD. The positive correlation may be due to the fact that the cloud microphysical effect of sulfate aerosols can promote the development of convection. With sufficient water vapors, sulfate aerosols form cloud condensation nuclei and promote CG lightning activity. When the concentration of sulfate aerosols is higher than the threshold value, the cloud microphysical effect and the radiation effect of aerosol may be counterbalanced, which may lead to weak correlation between CG lightning density and aerosol concentration. The results also show a weak negative correlation between dust aerosol and CG lightning density in April, May, June, and no significant correlation in July, August, September. Considering the low concentration of dust aerosols in the Yangtze River Delta and its surrounding areas, the inhibitory effect of dust aerosols on CG lightning activity may not be just explained by the radiation effect. The large particle size of dust aerosol may play a significant role in suppressing CG lightning activity. Lightning activity poses threats to human life and property safety. A large volume studies indicate that aerosol plays a significant role in lightning activity. To explore the effect of different types of aerosols on lightning activity in the Yangtze River Delta and its surrounding areas, cloud-to-ground (CG) lightning location data and aerosol optical depth from reanalysis dataset is analyzed in the target area(27.5°-35°N, 115°-122.5°E) during 2015-2021.The spatial distribution of aerosol optical depth (AOD) with CG lightning condition and without CG lightning condition, and monthly variation of aerosol concentration under two conditions are investigated. All the grids in the target region show that sulfate AOD is higher, while dust AOD is lower with CG lightning. In summer there are little differences between the AOD with CG lightning and without CG lightning conditions. In other months, more sulfate aerosol and less dust aerosol are found with CG lightning condition.The spatial distribution of CG lightning density difference under higher and lower AOD conditions is given. The results show that when the sulfate AOD is high, the CG lightning density of most grids is higher. The CG lightning density is significantly lower when the dust AOD is high.The correlation coefficient between CG lightning density and the AOD for different types of aerosols is calculated for the months when CG lightning is active. When the concentration of sulfate aerosol is low, the correlation coefficient between sulfate AOD and CG lightning density is significant. When the sulfate aerosol concentration exceeds a certain threshold, there is no significant correlation between CG lightning density and sulfate AOD. The positive correlation may be due to the fact that the cloud microphysical effect of sulfate aerosols can promote the development of convection. With sufficient water vapors, sulfate aerosols form cloud condensation nuclei and promote CG lightning activity. When the concentration of sulfate aerosols is higher than the threshold value, the cloud microphysical effect and the radiation effect of aerosol may be counterbalanced, which may lead to weak correlation between CG lightning density and aerosol concentration. The results also show a weak negative correlation between dust aerosol and CG lightning density in April, May, June, and no significant correlation in July, August, September. Considering the low concentration of dust aerosols in the Yangtze River Delta and its surrounding areas, the inhibitory effect of dust aerosols on CG lightning activity may not be just explained by the radiation effect. The large particle size of dust aerosol may play a significant role in suppressing CG lightning activity.

Abstract:
keep_len="250">Beijing, Tianjin, Hebei and neighbouring areas (34°-43°N, 113°-123°E) are located at the north edge of the East Asian summer monsoon, and they are also the main heavy-rain areas in northern China. The hourly precipitation data of 87 national meteorological stations from 1966 to 2021 are used for the analysis of spatial distribution and interannual variations, while the data of 298 stations from 1980 to 2021 are used to statistically analyze the diurnal variations and interannual variations of light precipitation (0.1-20 mm·h^-1) and short-time heavy precipitation (no less than 20 mm·h^-1) for the warm season (May-September) over the region. The results show that the annual average light precipitation and frequency in Beijing, Tianjin, Hebei and neighbouring areas during the warm season are much higher than those of short-time heavy precipitation. However, there is an area in the west of the Bohai Sea Region (37°-41°N, 115°-119.5°E) with high short-time heavy rainfall intensity but weak rainfall amount and frequency, which means the convective characteristics of short-time precipitation over this area are more extreme and significant. The interannual variations of two kinds of precipitation amount, frequency, and intensity in Beijing, Tianjin, Hebei and neighbouring areas excluding the west of Bohai Sea Region both present an overall growing trend in the warm season, in which the increasing trend of short-time heavy precipitation is more obvious, but the trend in the west of the Bohai Sea Region is not obvious. The diurnal variation amplitudes of light precipitation amount and frequency in Beijing, Tianjin, Hebei and neighbouring areas excluding the west of the Bohai Sea Region are significantly weaker than those of short-time heavy precipitation, but the peak durations are significantly longer. Compared to Beijing, Tianjin, Hebei and neighbouring areas excluding the west of the Bohai Sea Region, two types of precipitation in the west of the Bohai Sea Region from July to September are more frequent and the rainfall peak durations are longer. The interannual variations of precipitation in different periods of the whole day show that the light precipitation in two regions both decrease in the afternoon, while the short-time heavy precipitation has weakened significantly in the afternoon since 2005, but increased significantly from midnight to early morning. Beijing, Tianjin, Hebei and neighbouring areas (34°-43°N, 113°-123°E) are located at the north edge of the East Asian summer monsoon, and they are also the main heavy-rain areas in northern China. The hourly precipitation data of 87 national meteorological stations from 1966 to 2021 are used for the analysis of spatial distribution and interannual variations, while the data of 298 stations from 1980 to 2021 are used to statistically analyze the diurnal variations and interannual variations of light precipitation (0.1-20 mm·h^-1) and short-time heavy precipitation (no less than 20 mm·h^-1) for the warm season (May-September) over the region. The results show that the annual average light precipitation and frequency in Beijing, Tianjin, Hebei and neighbouring areas during the warm season are much higher than those of short-time heavy precipitation. However, there is an area in the west of the Bohai Sea Region (37°-41°N, 115°-119.5°E) with high short-time heavy rainfall intensity but weak rainfall amount and frequency, which means the convective characteristics of short-time precipitation over this area are more extreme and significant. The interannual variations of two kinds of precipitation amount, frequency, and intensity in Beijing, Tianjin, Hebei and neighbouring areas excluding the west of Bohai Sea Region both present an overall growing trend in the warm season, in which the increasing trend of short-time heavy precipitation is more obvious, but the trend in the west of the Bohai Sea Region is not obvious. The diurnal variation amplitudes of light precipitation amount and frequency in Beijing, Tianjin, Hebei and neighbouring areas excluding the west of the Bohai Sea Region are significantly weaker than those of short-time heavy precipitation, but the peak durations are significantly longer. Compared to Beijing, Tianjin, Hebei and neighbouring areas excluding the west of the Bohai Sea Region, two types of precipitation in the west of the Bohai Sea Region from July to September are more frequent and the rainfall peak durations are longer. The interannual variations of precipitation in different periods of the whole day show that the light precipitation in two regions both decrease in the afternoon, while the short-time heavy precipitation has weakened significantly in the afternoon since 2005, but increased significantly from midnight to early morning.

Abstract:
keep_len="250">Ecological monitoring is an important part of environmental protection. To monitor the movement and abundance of animals in the airspace, an Aerial Ecological Monitoring System (AEMS) is developed by CMA Meteorological Observation Center for China's next-generation weather radar (CINRAD) network. Characteristics of weather radar clear air echo data and airborne biological scattering data are studied to identify biological echoes through fuzzy logic algorithm, and the system can monitor real-time ecological activities of insects such as biological density, migration path and space-time distribution.Weather Radar Airborne Ecological Monitoring System has been put into trial operation since May 2022. During the real-time monitoring period, it's found that the insect activity shows obvious spatial and temporal distribution characteristics. From August to September, pests are of large quantity and wide range, indicating urgent need of insect disaster prevention and control. In May, June, September, and October, insect activity gradually increases from 2000 BT every day, reaches its peak from 2200 BT to 2300 BT, gradually decreases thereafter, and disappears mostly by 0600 BT. In July and August, insect activity gradually increases from 2000 BT every day, with a peak from 2100 BT to 2200 BT. Insect activity begins during the daytime, increases at 0600 BT, becomes more frequent at 1300 BT, and gradually decreases thereafter. From May to July, there is a significant shift from south to north (i.e., northward migration process), and in late August, it quickly changes into a to southward migration. The southward migration process of insects is larger and more numerous than the northward migration process. It's verified that the system can effectively monitor real-time aerial ecology, providing technology and data support for precise pest control.However, characteristics of pests need further research and clear distribution of pests is an urgent need. Therefore, in-depth research will be carried out on aerial ecological classification technology, combined with other direct observation means such as real-time monitoring by drones to explore the relationship between radar detection and different pests, and improve the ability to identify different kinds of insects. Ecological monitoring is an important part of environmental protection. To monitor the movement and abundance of animals in the airspace, an Aerial Ecological Monitoring System (AEMS) is developed by CMA Meteorological Observation Center for China's next-generation weather radar (CINRAD) network. Characteristics of weather radar clear air echo data and airborne biological scattering data are studied to identify biological echoes through fuzzy logic algorithm, and the system can monitor real-time ecological activities of insects such as biological density, migration path and space-time distribution.Weather Radar Airborne Ecological Monitoring System has been put into trial operation since May 2022. During the real-time monitoring period, it's found that the insect activity shows obvious spatial and temporal distribution characteristics. From August to September, pests are of large quantity and wide range, indicating urgent need of insect disaster prevention and control. In May, June, September, and October, insect activity gradually increases from 2000 BT every day, reaches its peak from 2200 BT to 2300 BT, gradually decreases thereafter, and disappears mostly by 0600 BT. In July and August, insect activity gradually increases from 2000 BT every day, with a peak from 2100 BT to 2200 BT. Insect activity begins during the daytime, increases at 0600 BT, becomes more frequent at 1300 BT, and gradually decreases thereafter. From May to July, there is a significant shift from south to north (i.e., northward migration process), and in late August, it quickly changes into a to southward migration. The southward migration process of insects is larger and more numerous than the northward migration process. It's verified that the system can effectively monitor real-time aerial ecology, providing technology and data support for precise pest control.However, characteristics of pests need further research and clear distribution of pests is an urgent need. Therefore, in-depth research will be carried out on aerial ecological classification technology, combined with other direct observation means such as real-time monitoring by drones to explore the relationship between radar detection and different pests, and improve the ability to identify different kinds of insects.