Based on the drought disaster data of the Heng-Shao drought corridor from 1961 to 2018, the meteorological drought composite index (MCI) was used to study the drought monitoring and evaluation methods of the Heng-Shao drought corridor. The results are as follows: (1) During the peak period of crop water demand (from June to October), the drought events with weighted mean of regional MCI (DI) less than or equal to -0.5 and the process duration greater than or equal to 16 days were included in the statistics, and the three elements such as the extreme intensity, cumulative intensity and duration of DI index were the best factors for annual regional drought assessment. Furthermore, based on the three elements of DI index, the annual assessment index of regional drought (MCI_e) calculated by using the TOPSIS method was the best. (2) Based on the MCI_e index, the combined grading method of average value and standard deviation was used to obtain the threshold of regional drought degree for normal, drought, severe drought, and extreme drought years. It was found that the MCI_e index had a strong ability to assess extreme drought years and normal years in the Heng-Shao district, and had good assessment ability for 2019 and 2020. Furthermore, the extreme disaster year in 2013 was simulated, it was found that the MCI_e index could better capture the change of drought in the Heng-Shao drought corridor. Therefore, the MCI_e index could support the rapid assessment and early warning of drought in the Heng-Shao drought corridor to some extent.

To explore the mesoscale characteristics of heavy rainfalls triggered by warm shear line with low vortex over the Yangtze-Huaihe region, based on the conventional and intensive observation data, FY-2E satellite cloud images and NCEP/NCAR reanalysis data, two typical rainstorm processes with different types were comparatively analyzed in the Yangtze-Huaihe region. The rainfall with the stable pattern continued for a long time in wide range of the Yangtze-Huaihe region, while that with the eastward moving pattern relatively concentrated for a short time with stronger rainfall intensity. The results are as follows: (1) Two rainstorms were caused by the interaction of upper trough and low-level warm shear line, but the upper trough and low-level warm shear line were stable during the rainfall process with the stable pattern, while the low pressure trough on 500 hPa, low vortex in low layer and surface mesoscale low pressure moved eastward during the rainfall process with the eastward moving pattern, and the convergence was stronger in low and middle layer. (2) The convective organization form for the stable pattern was forward sequential development, and the structure of convection system was relatively loose, while the convective organization form for the eastward moving pattern was backward sequential development, and the organized degree was higher. (3) Two processes occurred in wet environment, and the low-level jet (LLJ) played a key role in transporting water vapor. The rainfalls mainly appeared in wind convergence area in the front of the southwesterly jet axis. The water vapor continuously transported on 850 hPa during the stable moving process, which was beneficial to the heavy rainfall with a wide range. LLJ was relatively strong during the eastward moving process, and the active southeasterly extra LLJ occurred in the late of the rainfall, which was conducive to the local concentrated rainfall. The convergence of the southwest and southeast winds in low level formed obvious mesoscale lifting during two processes, and the uplifting condition for the eastward moving process was better than that for the stable process. The heavy rainfall was mostly occurred nearby surface convergence. So, the surface convergence line played an important role in triggering convective instability, which can afford some indication to the rainfall area of short-term and imminent prediction.