In the spring of 2023, a severe meteorological drought occurred in southwestern China, which had a serious impact on the local social economy. In order to deeply understand the causes of this drought event and further provide a basis for the prediction technology of spring drought in southwestern China, causes of the spring drought event were analyzed from the perspective of SST (sea surface temperature) and MJO (Madden-Julian Oscillation) by using station-observed data, NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data, NOAA (National Oceanic and Atmospheric Administration) SST and other data, choosing T-N wave activity flux, composite analysis and other methods. The results showed that: (1) The spring drought over southwestern China in 2023 was a compound dought-heatwave event occurred in the middle in March, developed and expanded westward in April, and maintained in May. (2) In March, the horseshoe-shaped SST anomalies in the North Pacific caused the westerly jet stream to drift southward and westward, suppressing the precipitation in southwestern China. (3) In April, the anticyclonic circulation anomaly near the Bay of Bengal induced by warm SST in the Indian Ocean through Kelvin wave and the cyclonic circulation anomaly from the South China Sea to the Philippines triggered by warm SST in the Northwest Pacific through Rossby wave resulted in northerly winds in the south of southwestern China, which caused the divergence of water vapor and the development of drought in southwestern China. (4) MJO, which maintained in the western Pacific for a long time in May, stimulated the cyclonic anomaly from the South China Sea to the Philippines in lower troposphere due to Gill response, reduced the transport of southerly water vapor, and maintained drought in southwestern China.

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 a transition from sustained to sudden drought, while Inner Mongolia continued to experience drought. (2) During the same period, the 500 hPa 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.

The land-atmosphere coupling (LAC) strength can be used to characterize how the land surface influences precipitation, temperature or other atmospheric physical processes, and can be used to identify the hotspot of land-atmosphere interactions, which can deepen the understanding of landatmosphere interaction and climate system. In order to quantify the LAC strength in China, the spatial-temporal distribution characteristics of the LAC index of soil moisturelatent heat flux and latent heat flux-lifting condensation level, the Pearson and Kendall’s Tau correlation of soil moisturetemperature and soil moistureprecipitation were analyzed by using ERA5 reanalysis data. The results are as follows: (1) The latent heat flux increased with soil moisture increasing, providing water vapor for precipitation. The increase in latent heat flux led to the decrease of sensible heat flux, then temperature decreased, which weakened the drive of boundary layer and was not conducive to the uplift and condensation of air mass over arid and semiarid areas of northern China. This region was a hotspot of landatmosphere interaction in China. (2) There were obvious seasonal differences in LAC strength in China. The LAC strength over arid and semiarid regions was stronger in spring and summer, but weaker in autumn and winter. The soil was relatively dry in dry season over southwest China where LAC was significant. For landatmosphere coupling, we should not only consider the division of traditional climate zones, but also ponder the influence of rain belt dynamic changes.

A Tibetan Plateau Vortex (TPV) generated on the western Tibetan Plateau on 14 August 2006 was simulated using the Weather Research and Forecasting (WRF) regional model. Based on the evaluation of the performance of the WRF driven by different reanalysis/analysis datasets including the ERA5 and ERA-Interim data from the European Centre for Medium-Range Weather Forecast, and the final analysis data (FNL) of the global forecasting system of the National Centers for Environment Prediction (NCEP) on the simulation of TPV, the kinematic and thermodynamic structures during the genesis of TPV were investigated through the equation of  vorticity budget, apparent heat source and apparent moisture sink. The results show that ERA5 and ERA-Interim could well reproduced the genesis of TPV. The ERA5 had the best ability to simulate the low-level cyclonic circulation, the spiral rainbands of TPV, and it produced the heaviest rainfall among three simulations. The FNL data could not portray the genesis of this TPV and its rainfall pattern. The development of positive vorticity, heat and moisture budgets during TPV generation were closely related to corresponding vertical transportation in lower troposphere. Before the genesis of TPV, surface sensible heating played an important role. During the development of TPV, strongest upward motion and most significant rainfall occurred, which was contributed mainly by obvious latent heating of condensation and eddy vertical transport process of heat and moisture, and conducive to the development of simulated vortex.

Drought is the most severe natural hazard affecting on human society and it exists generally in the whole global. In recent a century, the climate warming and society developing exacerbated the degree of drought influence and risk, which brought a great threat to global agriculture, water resource, ecological environment security and society sustainable development. It is the basis of fighting and managing drought and reducing drought vulnerability to improve the drought monitoring and early warning skill. In this paper, we introduce the new progress of drought monitoring and prediction operation and research in the United States in recent years, and provide an overview of the development of regional and global drought monitoring and prediction systems (DMAPS). It focuses on the scientific researches and technology improvement of drought. At last, the opportunities and challenges of drought monitoring and prediction are discussed referring to NOAA Interagency Drought task Force in 2016, which is beneficial to provide a new perspective for drought monitoring and forecast in China.