The global climate model BCC-CSM2-MR (Beijing Climate Center-Climate System Model version 2-Medium Resolution) in⁃ dependently developed by the National (Beijing) Climate Center, which has participated in the Climate Model Interomparison Project Phase 6. Based on the BCC-CSM1.1m version, the BCC-CSM2-MR model is optimized in aspects of atmospheric radiation transport scheme, deep convection processes and gravity wave drag. Therefore, the improvement of the model’s ability to simulate precipitation and temperature in East Asia needs further assessment. Utilizing gridded observational datasets and station observations in China, the paper thoroughly compares the performances of BCC-CSM2-MR and BCC-CSM1.1m in simulating seasonal mean precipitation (tem⁃ perature) and daily precipitation (temperature) extremes in East Asia. The results are as follows: (1) Compared with the BCC-CSM1.1m, the BCC-CSM2-MR improves the model performance in simulating seasonal mean precipitation in most sub-regions of East Asia, espe⁃ cially for summer precipitation in the Tibetan Plateau. In particular, the model can better reproduce the annual cycle of precipitation in southeastern China, the Korean Peninsula and Japan. (2) The ability of the BCC-CSM2-MR to simulate the seasonal mean temperature in East Asia has not been improved significantly, and the simulated biases of monthly temperature change in most sub-regions of East Asia are greater than those of the BCC-CSM1.1m. (3) In terms of daily extreme precipitation (temperature), the simulation ability of the BCC-CSM2-MR is obviously better than that of the BCC-CSM1.1m, which significantly improves the simulation ability of daily extreme precipitation (temperature) in southeast China. Overall, the improvement of the BCC-CSM2-MR in deep convection process parameter scheme is beneficial to the simulation of precipitation in East Asia.

From January to June 2023, meteorological droughts of varying degrees occurred in southwestern China, eastern North China, northern East China, central southern China, southern South China, and central Northeast China, seriously affecting agricultural production and restricting local economic development. To improve the ability to respond to drought disasters, timely carry out disaster prevention and reduction work, and conduct real-time summaries of drought situations. This article uses K index, MCI index, T-N flux and CABLE land surface model, as well as meteorological observation data, reanalysis data, soil moisture data to comprehensively analyze the spatiotemporal distribution characteristics and causes of regional drought events. The results are as follows: (1) In the first half of 2023, severe regional drought occurred in southwestern China and eastern Inner Mongolia. The southwestern region experienced atransition from sustained to sudden drought, while Inner Mongolia continued to experience drought. (2) During the same period, the 500hPa geopotential height field showed a two trough and two ridge pattern at mid to high latitudes. The western Pacific subtropical high pressure abnormally extended westward and uplifted northward, and the Rossby waves at mid latitudes in Eurasia were abnormally weak, resulting in a weakening of the influence of flat westerly winds and cold air in mid to high latitudes, resulting in less precipitation in the southwest and eastern Inner Mongolia, leading to regional drought. (3) In the first half of 2023, the winter La Niña event shifted to the spring El Niño event, resulting in weak convective activity in the southwest region and triggering sustained hot and dry weather; The distribution of sea surface temperature sensitive areas in Inner Mongolia has led to the stability of its upstream high-pressure ridge, resulting in drought and limited rainfall in the eastern region of Inner Mongolia.

There are some systematic biases in prediction of solar radiation based on numerical models, the AVT method has been verified to reduce the prediction bias effectively. The AVT correction method was used to modify the forecasted solar radiation in two photovoltaic power plants in Hexi area of Gansu Province. The results state: (1) Before correction the forecast bias presented obviously diurnal variation with increase first and then decrease, while it wasn’t obvious after correction. There was a strong linear relationship between forecast deviation of solar radiation and observed values before correction, while it got weak after correction (the correlation coefficient and good fitting degree decreased). (2) There was obviously annual change characteristic of solar radiation with the highest forecast bias in spring, followed by summer, autumn and winter. After correction, its forecast bias was reduced in four seasons, especially in spring and summer.

The impacts of fake below-ground meridional wind (FBGMW) on the regional Hadley circulation in Africa (AFHC) in terms of the climatology, interannual variability, and linear trends have been analyzed based on seven reanalysis datasets by using the local partitioning method of the tropical overturning circulation (M1) and the three-pattern decomposition of global atmospheric circulation (M2). The results are as follows: (1) In terms of the climatology, the impacts of FBGMW on the intensity, common rising branch, and sinking branches in both hemispheres of the AFHC depended on the seasons and methods for the calculation of mas stream function. (2) Except for the common rising branch, the FBGMW had small impact on the interannual variability of the intensity of AFHC and the sinking branches location of AFHC in both hemispheres. No-considering FBGMW led to smaller interannual variability of the common rising branch of AFHC in winter and summer based on M1 method and in winter based on M2 Method, and larger interannual variability of the common rising branch of AFHC in autumn based on both methods. With no-considering FBGMW, the change of the interannual variability of the common rising branch of AFHC in spring based on M1 method and in spring and summer based on M2 method depended on the choice of the reanalysis data. (3) Although no-considering FBGMW, it had impact on the quantitative values of the linear trends of the intensity, common rising branch, and sinking branches location in both hemispheres of AFHC, the main conclusions of these linear trends did not change.

Based on daily meteorological observation data at 227 weather stations of Northwest China during 1962-2017, the decadal change characteristics of drought frequency with different grades including light drought, moderate drought, heavy drought and extreme drought were analyzed by using SPEI index. The results are as follows: (1) The frequency of drought with different grades in Northwest China occurred inter-decadal transition from more to less in the 1980s. The drought mainly occurred in western part of Northwest China before the transition, while it mainly occurred in eastern part of Northwest China after the transition. (2) The frequency of light drought and moderate drought was significantly higher than that of heavy drought and extreme drought, and the frequency of light drought and moderate drought appeared opposite variation tendency after 1980. (3) The spatial difference of drought frequency with different grades was obvious. The light drought and moderate drought mainly occurred in eastern Xinjiang and southern Qinghai, while heavy drought and extreme drought mainly occurred in western part and eastern part of Northwest China, respectively.

From the view of climate system complexity, the nonlinear characteristics of drought were discussed in Northwest China from 1962 to 2017. Based on the monthly meteorological observation data at 159 stations of Northwest China, the standardized precipitation evapotranspiration index (SPEI) was calculated, firstly. Then, the temporal and spatial distribution of drought was analyzed by using empirical orthogonal function (EOF). And on this basis the abrupt change of decomposed time coefficient of SPEI was detected by using moving cut data- approximate entropy (MC-ApEn) method. Finally, the complexity of drought was discussed by using approximate entropy (ApEn) method in Northwest China. The results are as follows: (1) The first EOF mode of SPEI was consistently positive in Northwest China from 1962 to 2017, while the second EOF mode was positive in the east and negative in the west of Northwest China. Compared with time coefficient of the second mode, the climate was wetter in the west and drier in the east than that before the abrupt change, and the change point was approximately in 1980. The drought existed 2-3 a period in Northwest China during 1962-2017. (2) The complexity of drought increased after the abrupt change of 1980 in Northwest China as the whole, so the predictability of drought decreased. Moreover, the complexity of drought in autumn and winter was greater than that in spring and summer in Northwest China from 1962 to 2017, and the complexity was the largest in winter and the smallest in summer.

Based on the daily mean air temperature data of NCEP/NCAR during 1948-2017, the extreme high temperature events in Central Asia were determined by percentile threshold method, then the temporal-spatial distribution characteristics of intensity and frequency of extreme high temperature events over the past 70 years were analyzed. The results show that the spatial distribution of mean temperature in warm season in Central Asia was significantly affected by topography, and it gradually decreased from southwest to northeast. The intensity and frequency of extreme high temperature events occurred interdecadal transition in 1967. The intensity after transition was significantly higher than that before the transition. The frequency showed a negative trend before 1967 and a positive trend after that. The areas of extreme high temperature events also occurred interdecadal transition. According to the trend distribution of intensity, the region with the most significant increase was located in the west of Uzbekistan, and the region with the most significant negative trend was located in the southern Xinjiang of China. While the most significant increase in frequency trend was in Ural region of western Kazakhstan, and the negative trend was in Pamir Plateau.