The use of different climatological normal periods means the change of the evaluation results of meteorological elements, the abnormal state of climate events and their change characteristics, which have a substantial impact on the climate monitoring and prediction operations. Using temperature and precipitation observation data from national meteorological stations in Ningxia from 1981 to 2021, this study conducted a comparative analysis of the temperature and precipitation characteristics between the old climatological normal period (1981-2010) and the new climatological normal period (1991-2020). Additionally, it explored the changes in extreme characteristics of these factors. The results are as follows: Compared to the old climatological normal period, the annual and seasonal average temperatures in Ningxia are generally higher in the new climatological normal period, which is particularly evident in spring, summer and winter, and the frequency of abnormally high (low) temperatures increases (decreases) accordingly. Yinchuan, the western part of Wuzhong, and the northern part of Zhongwei are areas experiencing significant temperature increase. The overall intensity of extreme high (low) temperature has intensified (weakened), and their frequency has increased (decreased). In summer, the threshold and intensity of extreme high-temperature rise across various regions, especially in the central and northern areas, while in winter, the intensity of extreme low-temperature weakens in most regions, the amplitude of extreme low-temperature varies significantly. The average annual precipitation, as well as the summer, autumn and winter average precipitation, are greater in the new climatological normal period compared to the old. There’s an increased frequency of abnormally more precipitation in summer and autumn, whereas the opposite trend is observed in spring and winter. Meanwhile, the frequency of abnormally less precipitation in all seasons has decreased to some extents. There are significant spatial differences in seasonal precipitation, with a general increase in precipitation in summer and autumn, and a pattern of “decreasing in the north and increasing in the south” in spring and winter. The overall trend of extreme precipitation in spring and autumn (summer and winter) is intensifying (weakening), albeit with fewer (more) extreme precipitation events. In summer, the threshold and intensity variations of extreme precipitation are greater in the north and south, and smaller in the central region, with a notable increase in extreme precipitation in Shizuishan.

Based on the rainfall station observations and the products of Multi-source Merged Precipitation Analysis System of China Meteorological Administration (CMPAS), eight kinds of satellite-based precipitation products (FY-4A, CMOPRH-RT, IMERG-Early, IMERG-Late, GSMaP-Now, GSMaP-Gauge, PERSIANN-Now, PERSIANN-CCS) are comprehensively evaluated during the record-breaking extremely heavy precipitation process in East Gansu on July 15, 2022 by using quantitative analysis, classification and structural similarity methods. The results show that eight kinds of satellite-based precipitation products basically reflect the spatial distribution characteristics of precipitation with more in the central and eastern regions and less in the northwest. Except for the GSMaP-Now product, the other seven satellite-based precipitation products all underestimate the precipitation at the center of the rainstorm. The eight kinds of satellite-based precipitation products have a good ability to describe the peak value of heavy precipitation, and both peak stages of the heavy precipitation process are reflected, but all of them seriously underestimate the magnitude of heavy rainfall and above. For precipitation of different magnitudes, the GSMaP-Gauge is the best for estimating precipitation of magnitude below torrential rain, while the CMOPRH-RT is the best for heavy rain and above, and all products cannot correctly hit the precipitation of torrential heavy rainfall. In terms of the structural similarity index, the CMOPRH-RT product can best represent the structural distribution of the precipitation process from three aspects of total precipitation, precipitation magnitude, and precipitation morphological distribution. In summary, for this precipitation event, the CMOPRH-RT precipitation product had the best performance in all aspects.

In order to project the future climatic characteristics and their changing tendencies in different areas in Ningxia section of the Yellow River Basin, the performance of the CMIP6 models in simulating the annual mean air temperature in Ningxia are evaluated based on observation data at 19 national meteorological stations and the CMIP6 models data. Then the future air temperature changes in the Yellow River irrigation area, the middle arid area and the southern mountainous area of Ningxia under different scenarios are analyzed. The results are as follows: (1) Most models of the CMIP6 have a good simulation ability to annual mean air temperature in the Ningxia section of the Yellow River Basin, with spatial correlation coefficient of 0.603-0.930 and temporal correlation coefficient of 0.381-0.782. Meanwhile, the result of multi-model ensemble simulation is better than that of a single model. (2) Under the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenarios, it is predicted that the annual mean air temperature in the Yellow River Basin Ningxia section will present a significant warming trend from 2021 to 2099, with a warming rate between 0.09 and 0.68 ℃·(10 a)^-1. The warming rates are obviously different in different scenarios, which shows a decreasing trend under the SSP1-2.6, and firstly increasing and then decreasing trend under the SSP2-4.5, an increasing-decreasing-increasing trend under the SSP3-7.0, and an increasing trend under the SSP5-8.5. (3) It is estimated that the annual mean air temperature in the Yellow River irrigation area, the middle arid area and the southern mountainous area will reach 10.91-11.29, 9.48-9.87, 7.47-7.84 ℃ in the 2030s, respectively, and 11.46-13.21, 10.00-11.75, 7.97-9.66 ℃ in the 2060s under the four scenarios, respectively.

With the global warming, the intensity and frequency of abnormal drought and flood are increasing, to improve the understanding of drought-flood transition events and the ability of precipitation prediction in the east region of Northwest China, the circulation characteristics of drought-to-flood transition over the east region of Northwest China from spring to summer are analyzed by establishing an index based on the observed monthly mean precipitation, sea surface temperature (SST), and NCEP/NCAR reanalysis datasets during 1979-2020, and the possible influence from the Atlantic SST anomalies is also discussed. The results are summarized as follows: In spring of drought-to-flood years, the polar vortex is weaker, the Ural blocking is stronger and deeper, and the east Asian trough is deeper, which result in less precipitation in the east region of Northwest China controlled by dry and cold northwest flow. In summer, the upstream low-pressure system is active, the south Asian high is stronger and the western Pacific subtropical high (WPSH) is stronger and westward. Such circulation anomalous can lead to warm and moisture air supplement, resulting in a sharp transition phenomenon occurring in the east region of Northwest China. While in flood-to-drought years, it presents an opposite feature. From the previous winter to summer, the Atlantic tripole SST anomalies are key factors affecting the difference of precipitation between spring and summer. In spring of drought-to-flood years, the negative phase of the Atlantic tripole SST pattern stimulates a zonal teleconnection wave train, passing through the central and western Europe, Lake Balkhash, and Northeast China to the Sea of Japan, and this circulation is conducive to less precipitation in the study area. With respect to summer, the intensity of the wave train is weakened and shifts westward. Therefore, the intensity and location of the key circulation system in the middle and high latitudes are adjusted comparing with that in spring, causing more precipitation. In flood-to-drought years the opposite occurs.

In order to better exploit the detection advantages of wind profile radar in upper layer, the detection data of ST wind profile radar during 2014-2017 from Huainan Climate and Environment Observatory (HCEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, were used to evaluate the detection performance of ST wind profile radar under different detection mode combinations, and the influence of meteorological environment on detection performance was explored. On this basis, the applicability of detection mode combinations was discriminated in practical operations. The results show that ST wind profile radar can achieve different detection purposes by combining high or low modes with switching altitude. However, there are differences in detection performance under different combinations of mode. On the one hand, the detection performance of radar gradually decreases before the mode conversion and rapidly increases after the mode conversion, while it gradually decreases with height under the high mode. On the other hand, the detection performance of radar doesn’t change significantly in process of the conversion, while it gradually decreases after the high mode to a certain height. In addition, the reducing degree of detection performance gradually increases as the transition altitude approach in autumn and winter. The precipitation reduces the detection performance in lower and middle layers of troposphere. So, we select suitable mode combination based on the detection performance of radar to atmospheric boundary layer, troposphere and stratosphere.

Based on European Centre for Medium-Range Weather Forecasts （ECMWF） fifth-generation global atmospheric reanalysis （ERA5） every day from May to August during 1979-2020, three land-atmosphere indexes to investigate land-atmosphere coupling processes were calculated,characteristics of land-atmosphere coupling in climatology and their difference under different dry and wetsoil conditions were analyzed over eastern and southern Asia. The results show that Northeast and North China,the Tibetan plateau, India, Yunnan Province of China and Southeast Asia,the middle latitude arid zone were strong land-atmosphere coupling zones in climatology. In the middle latitude arid zone, land-atmosphere coupling had no significant difference under different soil conditions due to the low soil moisture and its little variability. In the other strong coupling zones, the coupling strength decreased with increasing soil moisture condition because of the bigger variability of soil moisture in these regions, and this law is applicable to the coupling processes between soil moisture（SM） and evapotranspiration （ET）, between ET and water vapor condition of boundary layer, between ET and instability condition of boundary layer. The land-atmosphere couplings over South China were weak in climatology, coupling between SM and ET was significant only under dry soil conditions, while the coupling between ET and atmospheric boundary layer were not significant under all soil moisture conditions.

Based on the detailed information on transmission line lightning strike and meteorological elements data in 6 hours before transmission line lightning strikes from 1990 to 2017 in Shijiazhuang of Hebei Province, the statistical methods such as occurrence probability, occurrence frequency, linear trend and fluctuation amplitude were used to analyze occurrence regularity of transmission line lightning strikes, variation of timing wind, pressure, relative humidity, air temperature and ground temperature in 6 hours before transmission line lightning strikes. By defining the cumulative occurrence frequency of transmission line lightning strikes, the meteorological element indicators of occurrence of transmission line lightning strikes were determined, and the accuracy of level prediction of transmission line lightning strike accidents in Jingxing county of Shijiazhuang on 9 August 2018 was tested by comparing the EC numerical prediction with the automatic station data. The results show that the transmission line lightning strike accidents increased significantly and there were three peaks in Shijiazhuang in recent years, occurring mainly from afternoon to morning in summer, in August there was the highest probability, and in a day it was highest from 03:00 BST to 04:00 BST. In addition, when there was easterly wind, air pressure and relative humidity were rising, or when air temperature and land surface temperature were dropping, transmission line lightning strike accidents occurred frequently. Within 6 hours, when air pressure rose by 0.0-2.0 hPa, air humidity increased by 0-14%, air temperature dropped by 0-3.0 ℃, land surface temperature dropped by 0-6.5 ℃, and with the east wind as the central wind direction, the timing wind direction was within the range of 90°, the occurrence regularity and meteorological indicators of lightning strikes on transmission lines were well predicted and tested on 9 August 2018, which had certain guiding significance for preventing lightning strike accidents.

Based on the observational rainfall data in July of Ningxia, the NCEP/NCAR reanalysis data and the ERSSTv5 SST data from 1981 to 2018, the variation characteristics of precipitation in July in Ningxia and their formation causes were analyzed. This paper also discussed the influence of the equatorial Pacific SST anomaly on precipitation. The results are as follows: (1) In the past 38 years, the inter-annual variability of precipitation in July was significant, but the extremity and anomaly of precipitation both increased after 2000. (2) The 500 hPa geopotential height anomaly was low over the Balkash lake and it was high between North China, the Northeast China and the Sea of Japan in mid-high latitudes. The active low-pressure system from the Bay of Bengal to the South China Sea, coupled with water vapor transported by the southerly anomaly on 700 hPa from the Northwest Pacific, led to more precipitation in July in Ningxia. (3) Since the 21th century, the implication of equatorial Pacific SST on precipitation in July has strengthened, especially during late winter and early spring during the ENSO decaying phase. When the SST anomaly in the equatorial Pacific characterized  by a dipole pattern, namely, warm (cold) in the west and cold (warm) in the central, and the subtropical western Pacific anomaly cyclone (anticyclone) in July played an important role in transportation of water vapor. The pattern of lower in the west (east) and higher in the east (west) existed on 500 hPa height, which was favorable to more (less) precipitation and reflected the impact of the central pacific type of ENSO on precipitation in Ningxia to some extent.

Abstract: Based on the every 3-hour precipitation data from ERA-Interim dataset of European Centre for Medium-Range Weather Forecast (ECMWF) during 1979-2017, the spatial and temporal variation characteristics of precipitation in Qilian Mountain and its surrounding areas in the past 39 years were analyzed. The results show that the average annual precipitation in the study area was 232.4 mm, the precipitation had an increasing trend with a climate trend rate of 24.7 mm·(10 a)-1, and precipitation increased obviously in the semi-humid area, with a climate trend rate of 45.9 mm·(10 a)-1. The precipitation had a mutation between 1996 and 1997, and then increased significantly after 2000. The precipitation in the study area was largest in summer, accounting for 54.08% of the annual precipitation, while it was smallest in winter, accounting for 3.88% of the annual precipitation. The maximum monthly precipitation was 45.1 mm in July, while the minimum was 2.7 mm in December. The diurnal variation of precipitation had two peaks, the maximum peak value occurred during 14:00-20:00, and the second peak vaule occurred during 05:00-08:00. Both of the annual precipitation and climate trend rate in the study area had a good correspondence with the altitude. The higher the altitude was, the greater the precipitation would be, and the maximum precipitation was in the high altitude area in the central part of Qilian Mountains. The distribution of annual precipitation was mostly from northwest to southeast, and precipitation in the central and eastern parts of the Qilian Mountains was relatively larger.

Based on the intensified hourly rainfall observation data of regional automatic weather stations, the characteristics of extreme precipitation from May to September during 2008-2017 in southwestern Hubei was analyzed by using percentile method. Satellite cloud photograph TBB data and NCEP reanalysis data with 0.5°×0.5° spatial resolution were adopted to analyze the causes of typical cases. The results are as follows: (1) The degrees of extreme precipitation at different stations were not comparable because of large difference in threshold ranges between hourly heavy rainfall and daily extreme precipitation. The stations with high frequency of hourly heavy rainfall and heavy rainstorm mainly distributed around the mountains with topographic convergence and uplift. Hourly heavy rainfall mainly occurred during the period of 00:00-03:00 and 16:00-19: 00. (2) Most of the extreme precipitation in southwestern Hubei occurred near Hefeng with large altitude difference. Low-level jet flow and topographic effect caused the back propagation of mesoscale convection system during the eastward migration process, which led to long duration of precipitation and large accumulated rainfall. (3) The thermodynamics and vertical structures were different for the extreme precipitation processes in different periods. For warm sector extreme precipitation in June, thermal effect dominated and the upper layer systems developed before the lower. Dynamic effect was main for extreme precipitation in September, in which frontal zone was obvious, and the whole system strengthened.

It has been well known that the triple － pattern interannual SST anomalies in the North Atlantic are principally forced by the dominant modes of Atmosphere variability，the North Atlantic Oscillation(NAO)or Arctic Oscillation(AO) ，but to what extent the North Atlantic SST anomalies can affect the Storm Track in the midlatitudes remains to be an issue． Here we estimate the response of North Atlantic Storm Track to SST anomalies by a GCM named CAM3． 0． The atmospheric CAM3． 0 was forced by the triple SST anomalies firstly，then the simulation results in winter (December to January)were compared with the NCEP/NCAR reanalysis data． We found the simulation results could reproduce the anomalies of Atlantic Storm Track and Jet accompanying the AO anomalies． Conclusions can be summarized as follows:when the SSTA was positive(negative) ，the storm track enhanced (weakened) ， and the jet exit region had a meridional displacement to polar (equator) ． The SSTA may influence the storm track through two ways，one is to change the lower atmospheric baroclinicity to affect the intensity of storm track directly，the other is to influence the meridional displacement of jet firstly，and then the jet influence the storm track． The positive feedback effection between eddies and mean flow becomes severe ( weakening)when SSTA is positive (negative) ．

The variation characteritics of frost times and period in Ningxia region from 1961 to 2004 were analyzed. The results show that frost occurring in Ningxia wasmainly in Ap ril and October, and the frost times wasmost in the second ten - day of Ap ril; in the south and north of Ningxia region, the frost times was different significantly, and frost occurred frequently in mountainous region of South Ningxia; the annualmean frost times there was 8. 7 - 10. 8 times, and frost times was least in Tongxin for only 2. 1 times. The frost times p resented decreasing trend as a whole and itwas obvious in June and autumn. The abrup t of frost times occurred in 1984,and after 1984 the frost times reduced significantly. The first frost date was delayed and the last frost date advanced, as well as the frostless period was extended gradually in the three areas ofNingxia region.